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MIL-HDBK-684
FEBRUARY 15, 1995

MILITARY HANDBOOK

DESIGN OF COMBAT VEHICLES

FOR
FIRE SURVIVABILITY

0
,“

. . .

AMSC N/A FSC 12GP

o DISTRIBWION STATEMENTA Approved fcr public releose; distribution is unlimited.

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MIL-HDBK-684

9
FOREWORD ‘
II
1. This military handbook is approved for use by all Departments and Age~cies of the Department of Defense.
2. Beneficial comments (recommendations, additions, and deletions) and ariy pertinent data that may be of use in improving
this document should be addressed to Commander, US Army Tank-Automotive and Armaments Command, Am: AMSTA-
TR-T, Warren, MI 48397-5000, by using the Standardization Document Improvement Proposal (DD Form 1426) appearing at
the end of this document or by letter.
3. This handbook was developed to provide guidance to the armored combat vehicle designer and program managers for the
incorporation of fire survivability techniques early in the process and throughc$t the development of a vehicle. The application
of these techniques should enhance the survivability of the combat vehicle and its crew. The design procedures and survivabil-
ity techniques are also applicable to aircraft and naval vessels.
4. This handbook was developed under the auspices of the US Army Mate~el Command’s Engineering Design Handbook/
Information Program, which is under the direction of the US Army Industrial Engineering Activity. Research Triangle Institute
(RTI) was the prime contractor for this handbook under Contract No. DAAA09-86-DOO09. This handbook was prepared at
Southwest Research Institute (SWRI), a subcontractor to WI, by a diverse team of experts under the direction of the principal
investigator and author, Mr. Patrick H. ZabeL Mr. Zabel’s dedication and attention to detail were crucial to the successful com-
pletion of this work. The development of this handbook was guided by a technjcal working group (TWG) chaired by Dr. James
L. Thompson and composed of individuals ~om the Department of Defense. Mr. Steve McCormick of the US Army Tank/
Automotive Research, Development, and Engineering Center deserves special recognition for his manuscript reviews and
technical guidance to the principal investigator and the Engineering Handbook Office at RTI.

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o CONTENTS

FOREWORD ................................................................................................................................................................................ti
LIST OF ILLUSTRATIONS .....................................................................................................................................................xti
LIST OF T.ES ....................................................................................................................................................................ti
LIST OF ABBREVIATIONS AND A=O.S .................................................................................................................fi

INTRODUCTION
1-0 LIST OF S~ON ........................................................................................................................................................I.i
1-1 P~SE .........................................................................................................................................................................I.l
1-1.1 GENERAL P~SE .........................................................................................................................................l.l
1-1.2 OWECITVE ............................................................................................!...........................................................l.l
1-2 SCOPE ..............................................................................................................................................................................l.l
1-3 .APPIXATION ................................................................................................................................................................l.l
1-4 OVERVIEW ..............................................i......................................................................................................................l.l
1-4.1 BACKGRO~ ..................................................................................................................................................I.l
1-4.1.1 Review of Combat Vehicle Use ..............................................................................................................l.2
1-4.1.2 Review of~ ....................................................................................................................................l4
1-4.1.2.1 Direct-Fire ~.s ...........................................................................................................................l4
1-4.1.2.2 Overhead and Underneath Threats ..........................................................................*.......................l.5
1-4.1.2.3 Incendiary Threats ...........................................................................................................................1.5
1-4.1.3 Review of Survivability Enhancement T*iqu= .................................................................................l.5
1-4.2 DESIGN PHILOSOPHY .....................o...............................................................................................................l4

0,,
1-4.2.1 Basic Combm Vehicle Design Ptiomphy ..............................................................................................l4
1-4.2.2 Incorporation of F= Survivability Concept ..........................................................................................l.7
1-5 COST ANALYSIS ...........................................................................................................................................................l.8
1-5.1 COST-EFFECITVENE SS STUDIES CONDUCTED AT THE US ARMY TANK-AUTOMOTIVE
RESEARCH AND DEVELOPMENT COMMAND (TARADCOM) NOW US ARMY TANK-
AUTOMOTIVE COMMAND ~AcoM)] ......................................................................................................l.8
1-5.1.1 External Fuel Cell for M113 FoV.............................................................................................................l.8
1-5.1.2 AFDSE for M60 Series MBT .................................................................................................................l.8
1-5.2 COST ANALYSIS FOR FAASV PREPARED BY TACOM ...........................................................................l.9
1-5.3 METHODOLOGY TO ESTIMATE LIFE CYCLE COSTS OF AIRCMF”l’ FUEL SYSTEM
SURVIVABILITY ENHANCEMENT CON. .......................................................................................l.9
1-6 CONTENT OF HANDBOOK .......................................................................................................................................l.lO
~m ......................................................................................................................................................................... 1-11
BIBLIOGRAPHY ................................................................o..................................................................................................l.ll
CHAIT’ER 2
CATEGORIZJkTION OF FIRES
2-O LLST OF SYMBOLS ........................................................................................................................................................2.l
2-1 INTRODUCTION ............................................................................................................................................................2.l
2-2 DEFINITION OF ~S ..................................................................................................................................................2.2
2-2.1 IGmoN ...................................................................................!........................................................................2.2
2-2.1.1 Fluid Combmtibles ..................................................................................................................................2.2
2-2.1.1.1 Ignition of Fuel Va~m ....................................................................................................................2.3
2-2.1.12 Ignition of Fuel WS ........................................................................................................................2+
2-2.1.13 Geomerry Effects .............................................................................................................................2.5
2-2.1.1.4 Ignition of Vapors by an Exploding @ge ....................................................................................2.6
2-2.1.1-5 Ignition of a Spray by aI-kated Stiam ..........................................................................................2.8
O
!. 2-2.1.1.6 Ignition by Hot Pticles ..................................................................................................................2.8
2-2.1.1.7 Environmental Effects .....................................................................................................................2.8
2-2.1.2 Solid Combmtibles ..................................................................................................................................2.8
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2-2.1.3 Solid Cornbustible.Oxidlzer Mxmre ...................................................................................................2.l2
2-2.2 GRom ......4..................................................................................................................................................2.l2
2-3 WP~.GRO. =S ...........................................................................................................................................2.l3
2-3.1 MUNITION IIWl%4’IION ...........................................................~.................................................................... 2-13
2-3.1.1 Wnetic Energy ~eaW ..................................................../....................................................................2.l3
2-3.1.2 ChemicalEnergyThreats ................................................!.................................................................... 2-14
2-3.1.3 Incendiary Threats ...........................................................: ............................................................ ........ 2-16
2-3.1.4 Blmt~ea~ .........................................................................................................................................2.l6
2-3.2 ~L .................................................................................................................................................................2.l7
2-3.2.1 Locations ...............................................................................................................................................2.l7
2-3.2.2 Hazards ................................................................................................................................................. 2-17
2-3.3 I-IYDRAUIXFLUID ........................................................................................................................................2-18
2-3.3.1 Locations ...............................................................................................................................................2.l8
2-3.3.2 HUm& .................................................................................................................................................2.20
2-3.4 M~~ONS .....................................................................................................................................................2.2O
2-3.4.1 Locations .........................................................................~.....................................................................2.20
2-3.4.2 Hazards .....-.......................’..............................................2...........................................................“........ 2-20
2-4 SLOW-GROWTH FIRES ............................................................................................................................................. 2-20
2-4.1 IGNITION SOURC~S .................................................................!.................................................................... 2-20
t
2-4.1.1 Electricity ............... ..........................................................7..................................................................... 2-20
2-4.1.2 Hot Stiaces .......................................................................................................................................... 2-21
2-4.1.3 Exothermic Reactions ........................................................................................................................... 2-21
2-4.2 CQMBUS~LES ............................................................................................................................................. 2-21
2-4.2.1 Fuel ....................................................................................................................................................... 2-21
2-4.2.2 Hydraulic Fluids ................................................................................................................................... 2-22
2-4.2.3 Oil and Lubricants ................................................................................................................................ 2-22
2-4.2.4 Otiers ..............................................................................j..................................................................... 2-24
M~mNCES ..................................................................................................i......................................................................2.25
BIBLIOGRAPHY .................... ............................................................ .............:,...............-.......... ........................................ ... 2-26
CHAPTER 3 ~
II
MATERIALS AND HAZAR$S
3-1 INTRODUCTION ......................................4................................................................................................................... 3-1
3-2 MOBILITY =LS ........................................................................................................................................................ 3-1
3-2.1 IN-2: DIESEL ~L ......................................................................................................................................... 3-2
3-2.2 DF-1 WINTER-GRADE DIESEL ENG~F~L ...................!....................................................................... 3-2
3-2.3 DF-A ARCTIC DIESEL ENGINE @L .......................................................................................................... 3-2
3-2.4 JP-8 KEROSENE-TYPE AVLiTION mw ENGm ~L ................................................................... 3-2
3-2.5 OTHER FUELS .................................................................................................................................................. 3-6
3-2.5.1 “JP-4 Gasoline-Type Aviation Turbine Engine Fuel ............................................................................... 3-6
3-2.5.2 JP-5 High-l%sh-Pointj Kerosene-Type Aviation Turbine Engine Fuel ................................................. 3-6
3-2.5.3 Automotive Gasoline .............................................................................................................................. 3-6
3-2.5.4 Gmohol ................................................................................................................................................... 3-6
3-2.5.5 Commercial Diesel Fuels ........................................................................................................................ 3-7
3-2.5.6 Foreign Diesel Fuels ............................................................................................................................... 3-7
3-2.5.6.1 NATO Diesel Fuel F.54 ........................................... ....................................................................... 3-7
3-2.5.6.2 Russian Diesel Fuels ....................................................................................................................... 3-7
3-2.5.6.3 Foreign Commercial Diesel Fuels ................................................................................................. 3-8
3-2.5.7 Prirmuy, Alternate, and Emergency Fuels ....................... ....................................................................... 3-8
3-2.5.7.1 Field-Expedient Mixtures ............................................................................................................... 3-8
3-2.5:7.2 Comparison of Fuel Types .............................................................................................................. 3-8
3-2.5.7.3 Single Fuel on the Battlefield ......................................................................................................... 3-9
3-2.5.8 Fire-Resistant Fuels ................................................................................................................................ 3-9
3-3 HYDRAULIC ~WDS ................................................................................................................................................. 3-10
3-3.1 FIRE-RESISTANT HYDRAULIC FLUID ..................................................................................................... 3-10

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33.1.1MIL-H-46170, Hydraulic Fluid, Rust-Inhibited, Fire-Resisumq Synthetic Hydrocarbon-Base

o (MilitarY Symbol FRIL NATO Symbol H544) .............................................................................. 3-I3

3-3.1.2 MIL-H-8321?2, Hydraulic Fluid, Fw-Resistan4 Synthetic Hydrocarbon-Base, AircmfL Metric,
NATO Symbol H-537 ...................................................................................................................... 3-13
3-3.1.3 Proposed Single Hydraulic Htid .......................................................................................................... 3-13
3-32 NONIWWMABLE HYDRAULIC =~S .................................................................................................. 3-13
3-3.3 PIXROLEUM-BASED =WS ...................................................................................................................... 3-13
3-3.3.1 MIL-H-6083, Hydraulic FluiL Petroleum-Base for Preservation and Opemtion (Military Symbol
OHT, NATO Symbol C-635) ............................................................................................................ 3-14
3-3.3.2 MIL-H-5606, Hydraulic FluiA Petroleum-Base, Aim& Mksile, and Ordnance (Military
Symbol OHA, NATO Symboi H-515) ............................................................................................ 3-14
3-3.3.3 MILH-19457, Hydraulic Fluid, FiiResisrant, NoMemtotic .......................................................... 3-14
3-3.3.4 MIL-B-46176, Brake Fluid, Silicone, Automotive, All-Weather, Operational and Presemuive,
Metric (Military Symbol BFS, NATO Code No. H-547) ................................................................. 3-14
3-3.4 HYDRAULIC FLUID HAzARDs .................................................................................................................. 3-14
3-3.4.1 Ignition and Combustion of a Spray .................................................................................................... 3-14
3-3.4.2 Ballistic Rupture of a Vessel ................................................................................................................ 3-16
3-3.4.3 Combustion of a Pool ........................................................................................................................... >16
3-3.4.4 Ignition and Combustion on a Hot Surface ......................................................................................... 3-17
3-4 OTHER PETROLEUM, OILS, AND LUBRICANTS (POL) ..................................................................................... 3-18
3-4.1 TRJUWMISSION FLUIDS, ENGINE OILS, AND L~N~ ............................................................... 3-18
3-4.1.1 MIL-L-2104, Lubricating Oii, Internal Combustion Engine, Combat/Tactical Service ...................... 3-18
3-4.1.2 MIL-L-2105, Lubricating Oil, Gear, MdtipuWoW .............................................................................. 3-18
3-4.1.3 MIL-L-7808, Lubricating Oil, Akaft Turbine Engine, Synthetic-Base, NATO Code No. 0-148.....3-18
3-4.1.4 MIL-L-9000, Lubricating Oil, Sbipboad Internal Combustion Engine, High-output Diesel ............ 3-20
3-4.1.5 MIL-L-21260, Lubricating Oil, Internal Combustion Engine, preservative and Break-in ..................3-20
3-4.1.6 MILL-23699, Lubricating Oil, Aircraft Turbirte Engine, Synthetic Base ........................................... 3-20

o 3-4.1.7 MILL-46152, Lubricating Oil, Internal Combustion Engine, Administrative Service ...................... 3-20
3-4.1.8 MIL-L-46167, Lubricating Oil, hmtrnal Combustion Engine, ktic .................................................. 3-20
3-4.1.9 W-L-765, Lubrkmm Enclosed Gear, Norwxtreme Pressure .............................................................. 3-20
3-4.2 AMFMEZE comms ......................................................................................................................... 3-20
3-4.2.1 MIL-A-1 1755, Antifreeze, AnXic-Type ............................................................................................... 3-21
3-4.2.2 MIL-A-46153, Antiikeze, Ethylene Glycol, Inhibite& Heavy-Duty, Single Package ........................ 3-21
3-4.2.3 Other Freeze Point Suppressants .......................................................................................................... 3-21
3-4.3 FOG OIL ............................................................................................................................................................32l
3-5 MUNITIONS ................................................................................................................................................................. 3-22
3-5.1 GUN AND SOLID ROCKET PROP ELLANTS .............................................................................................. 3-23
3-5.2 HIGH EXPLOSIVES ........................................................................................................................................ 3-24
3-5.3 OTHER MUNITIONS ...................................................................................................................................... 3-26
3-6 OTHER COmUS~~ ........................................................................................................................................... 3-28
3-6.1 ELECTRIC WIRING ~SUA~ON ............................................................................................................... 3-2$
3-6.1.1 Elastomer Types ................................................................................................................................... 3-29
3-6.1.2 ‘I%ermoplastic Types ............................................................................................................................ 3-29
3-6.1.3 Toxic ~m ......................................................................................................................................... 3-29
3-6.2 SPALL AND RADIATION ~ ............................................................................................................... 3-29
3-6.3 S~TS .............................................................................................................................................................. 3-33
3-6.4 ON-VEHICLE EQWMENT (.O=) ............................................................................................................... 3-35
3-6.5 PAINTS AND COATINGS .............................................................................................................................. 3-35
3-6.5.1 Nonintunmcent Coatings ..................................................................................................................... 3-35
3-6.5.2 Intumescent CoaMgs ............................................................................................................................ 3-35
3-6.6 MISCELLANEOUS COMBUSTIBLES .......................................................................................................... 3-35
3-6.6.1 Elastomers, Plastics, Fire-Retardant Additives, and Fiflem.................................................................. 3-40

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3-6.6.1.1 Plastics .......................................................................................................................................... 3-45
3-6.6.1.2 Hmtomem ..................................................................................................................................... 3-45
3-6.6.1.3 Fire-Retardant Ad&tiv= ............................................................................................................... 3-45

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3-6.6.1.4 Fillers ............................................................................................................................................3.45
3-6.6.2 Textiles .................................................................................................................................................3.46
3-6.6.3 Otier .....................................................................................................................................................3.46
REFERENCES ...................................................................................................................................... ............... ............... .... 3-49
BIBLIOGRAPHY ..............................................................................................J!................................................................... 3-53
i
CHAPTER 4 i
FIRE PREVENTION
4-1 INTRODUCTION ..........................................................................................................................................................4.l
4-1.1 TRAINING-INDUCED FIRES ......................................................................................................................... 4-2
4-1.2 BA’lTLE-INDUCED FIRES .;........................................................................................................................... 4-2
4-1.2.1 Battle Damage Assessment and Repair Program Databde ................................................................... 4-2
4-1.2.2 Vehicles, Situations, T@eats, and Combustibles .................................................................................... 4-5
4-1.2.3 Hits: Number and Locations ............................................l..................................................................... 4-5
4-2 ENGINE TYPES ......................................................................................~-............ ..................................................... 4-1o.
4-2.1 COMPRESSION IG~ON ............................................................................................................................ 4-11
4-2.1.1 Fuel Feed ........................................................................i.................................................................... 4-12
4-2.1.2 Hot-Surface Ignition ........................................................~.................................................................... 4-13
4-2:2 SPARK IG~ON ......................................................................i.................................................................... 4-14
4-2.2.1 Fuel.Feed .........................................................................j.................................................................... 4-14
4-2.2.2 Hot-Surface Ignition ............................................................................................................................. 4-14
..........................................................................................................................................................
4-2.3 TURBINE 4-14
4-2.3.1 Fuel Feed .........................................................................{.................................................................... 4-15
4-2.3.2 Hot-Surface Ignition ............................................................................................................................ 4-16
4-3 FUEL SYS~M ........................................................................................\.................................................................... 4-16
4-3.1 FUEL STOWGE .........................................................................!.................................................................... 4-16
4-3.1.1 Current US Fuel Cell Design .i.........................................~.................................................................... 4-17
4-3.1’.2 Fuel Cell Design Criteria .................................................~.................................................................... 4-18
4-3.1.3 Fuel Cell Location ..........................................................2.................................................................... 4-19
4-3.1.4 Hydraulic ~Loads ......................................................~.................................................................... 4-19
4-3.1.5 Fuel Cell Survivability Enhancement ................................................................................................... 4-20
4-3.1.6 Comments on Fuel Cell Design .......................................i.................................................................... 4-23
4-3.2 FUEL mS~R'S~SYS~M ..............................................i.................................................................... 4-23
4-3.3 FUEL LINE’CONSTRUCTION AND ROUTING .......................................................................................... 4-24
4-3.4 FUEL ~PES .................................................................................................................................................... 4-25
4-3.5 LESSONS LE.D ...................................................................................................................................... 4-25
4-3.5.1 Design of Vehicular Bilge ...............................................L.................................................................... 4-25
4-3.5.2 Selection of Engine Types .................................................................................................................... 4-26
4-3.5.3 Design and Location of Fuel Cells ..................................~.................................................................... 4-26
4-3.5.4 Design and Location of Fuel Lines ....................................................................................................... 4-27
4-3.5.5 Selection, Design, and Location of Space Heaters ............................................................................... 4-27
4-3.5,6 Smoke Generators ................................................................................................................................. 4-29
4-4 HYDRAULIC’AND ANCILLARY POWER SYSTEMS ............................................................................................ 4-29
4-4.1 POWER MEDIA CHOICE ............................................................................................................................... 4-29
4-4.1,1 Liquid”Systems ..................................................................................................................................... 4-29
4-4.1.2 Pneumatic Systems ............................................................................................................................... 4-30
4-4.1.3 System Specifications ........................................................................................................................... 4-30
4-4.2 COMPONENT LOCATION, MATERIAL SELECTION, ~PRO~C~ON . .......................................... 4-30
4-4.2.1 ~~p ..................................................................................................................................................... 4-31
4-4.2.2 Resewoti ............................................................................................................................................... 4-32
4-4.2.3 Accumulators ........................................................................................................................................ 4-33
4-4.3 CIRCUIT LAYOUT%ND LOCATION ....................................~..................................................................... 4-34
4-4.3.1 High-Pressure Side .........................................................J..................................................................... 4-34
4-4.3.2 Low-Pressure Side ................................................................................................................................ 4-34
4-4.4 MATERIAL CHOICES ................................................................................................................................... 4-35

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4-4.4.1 Hydraulic Rping ................................................................................................................................... 4-35
,, 4-4.4.2 Pipe Fittings .......................................................................................................................................... 4-35
0 4-4.4.3 EbStOIIWiCSds .................................................................................................................................. 4-36
44.5 LESSONS LEARNED ...................................................................................................................................... 4-37
4-45.1 Locating Hydraulic Lines Near Hot SWu ............................................................................................ 4-37
4-4.5.2 Hydraulic Fluid Line Cut With aTorcb ............................................................................................... 4-37
4-4.5.3 Hydraulic Fluid Line Protection ........................................................................................................... 4-37
4-5 ELECI-RJCAL SYSTEMS ............................................................................................................................................ 4-37
4-5.1 VOLTAGE CHOICE ........................................................................................................................................ 4-38
4-5.2 MATERIAL CHOICES .................................................................................................................................... 4-39
4-5.3 CIRCUIT DESIGN ........................................................................................................................................... 4-39
4-5.4 LESSONS ~D ......................................................................................................................................M
4-5.4.1 Flammability of Electrical Wue Insulation .......................................................................................... 4-40
4-5.4.2 Electrical Fusing Improperly Sized, Selecte& or hted .................................................................... 4-40
4-5.4.3 Electric Short Melts Through Combustible Fluid or Gun propellant Container .................................. 4-40
4-5.4.4 Electric Spark Ignition of Flammable ~ti& ....................................................................................... 4+1
4-5.4.5 Wiring Routing and F~tetig .............................................................................................................. 4-41
4-6 ~ON ............................................................................................................................................................ 4-41
4-6.1 AMMmoN TYPES ................................................................................................................................... 4-41
4-6.1.1 Ammunition for Onboard Use .............................................................................................................. 4-42
4-6.1.2 Transported ~unition ...................................................................................................................... 4-42
4-6.1.3 Relative Ammunition Hazard Assessment ........................................................................................... 4-42
4-6.2 STOWAGE LOCATION AND D~IGN ......................................................................................................... 4-43
4-6.2.1 Stowage Locatiom ................................................................................................................................ 4-44
4-6.2.2 Ammunition Stowage Designs ............................................................................................................. 4-46
4-6.2.2.1 Early Designs ............................................................................................................................... 4-46
4-6.2.2.2 Ammunition Magazines for the Ml and MIA] MBTs ................................................................ 4-46
4-6.2.2.3 Advanced Survivability Test Bed Ammunition Stow~e ............................................................. 4-48
4-6.2.2.4 Armored Mobile Haetiw~ ................................................................................................... 4-51
4-6.3 NEW DEVELOPMENTS ................................................................................................................................. 4-52
4-6.3.1 Insensitive Munitions: Background and Requirements ........................................................................ 4-52
4-6.3.2 Liquid Gun BoFllmG ......................................................................................................................... 4-52
4-6.3.3 Insensitive High Explosives ................................................................................................................. 4-53
4-6.3.4 Insensitive propellants and/or Propulsion Systems ... .......................................................................... 4-53
4-6.4 LESSONS LEARNED .................................................................................................................................... .. 4-53
4-6.4.1 Stowage of Main Weapon hutition ............................................................................................... 4-54
4-6.4.2 High-Explosive Stowage ...................................................................................................................... 4-56
4-6.4.3 chemical Ammunition Stowage ........................................................................................................... 4-56
4-7 MATERIALS S=~ON .......................................................................................................................................... 4-56
4-7.1 FLAMMABrLllY ............................................................................................................................................ 4-57
4-7-’2 PYROLYSIS AND COMBUSTION PRODUCIX .......................................................................................... 4-58
4-7.3 LESSONSLEARNED ......................................................................................................................................4-60
4-7.3.1 Ballistic Fabric Selection ...................................................................................................................... 4-60
4-7.3.2 Wazard Potential From Use of Composites .......................................................................................... 4-60
4-7-3.3 Fiie-Resistant Polymers and Polymeric Compsi@s ............................................................................ 4-61
4-8 SYSTEM INTEGRATION ............................................................................................................................................ 4-61
4-8.1 COMPARTMENTALIZATION ....................................................................................................................... 4-61
4-8.1.1 Ammunition Mag~nes ........................................................................................................................ 4-61
4-8.1.2 External Ammunition Stowage ............................................................................................................. 4-62
4-8.1.3 Jacketed or Double-Walled Fuel Cells ................................................................................................. 4-62
4-8.1.4 Storage Compartments and Bilge ......................................................................................................... 4-63
4-8.1.5 Span Ctins ........................................................................................................................................ 4-64

0 4-8.2 SYNERGISM OF FIRE PROTECTIVE COMPONENT3 ............................................................................... 4-64

4-8.2.1 Less Hazardous Ammunition ............................................................................................................... 4-64
4-8.2.2 Water Storage ....................................................................................................................................... 4-65
4-8.2.3 Space Henters and Exhaust System ..................................................................................................... 4-65
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4-8.3
EXAMPLES OF SYSTEM mGW~ON ................................................................................................... 4-66
4-8.3.1” Advanced Survivability Test Bed (ASTB) Fuel Btier ....................................................................... 4-66
4-8.3.2 LSTP-5AI Fuel System Reticulated Foa .......................................................................................... 4-67 a
4-8.3.3 Jettisonable Fuel Cells .......................................................................................................................... 4-68
4-8.4 LESSONS LE.D...: .................................................................................................................................. 4-69.
4-8.4.1 Lessons Learned From Tests of External Fuel Cells ......~..................................................................... 4-69
4-8.4.2 Use of Intumescent Coatings ................................................................................................................ 4-69
4-8.4.3 Lessons Learned From North Africa, 1942 ....................j..................................................................... 4-70
4-8.4.4 Protection Afforded by Water and Other Materials in SEA ................................................................. 4-71
4-8.4.5 Engine Compartment Design ..........................................!..................................................................... 4-71
,,
REFERENCES .....................”.”
- -
...............................”.”.......”.............................. ..’;..................................................................... 4-71
BIBLIOG~HY .............................................................................................t..................................................................... 4-75
CHAPTER 5 ~
CREW SURVIVAL CRITEI+A
5-O LIST OF SYMBOLS ...................................................................................................................................................... 5-1
5-1 INTRODUCTION ........................................................................................................................................................... 5-1
5-1.1 PURPOSE ........................................................................................................................................................... 5-1
5-1.2 THREATS ........................................................................................................................................................... 5-1
5-1.2.1 Threat Effects in General ........................................................................................................................ 5-2
5-1.2.2 Shock Pressure and/or Impulse ................................................................................................................ 5-3
5-1.2.3 Light ........................ .........................................................~,
.................................................... .................... 5-3
II
5-1.2.4 Vapors, Mists, and Solid Particulate ............................+....................................................................... 5-3
5-1.3 CREW PERFORMANCE .........................................................ji....................................................................... 5-3
5-2 THERMAL INJURY .................................................................................i.........”............................................................. 5-4
5-2.1 BACKGROUND ....................... .................................................!!....................................................................... 5-4
5-2.1.1 Problem Magnitude ................................................................................................................................. 5-5
5-2.1.2 Medical Considerations .................................................j........................................................................ 5-5
5-2.1.2.1 Skin BDs ............................................................................................~.......................................... 5-5 9
5-2.1 .2.1.1 Heat Trmsfer ........................................................................................................................... 5-5
5-2.1 .2.1.2 Degree and Extent of aBw ................................................................................................... 5-6
5-2.1 .2.1.3 Results of Skin Burn Tes@...................................................................................................... 5-7
5-2.1.2.2 Hyperthermia .................................................................................................................................. 5-7
5-2.1 .2.2.1 Body Temperature Regulation ................................................................................................ 5-7
5-2.1 .2.2.2 Reaction to Excessive Heat ..................................................................................................... 5-8
5-2.1 .2.2.3 Localized Overtemperature of Body P@s .............................................................................. 5-8
5-2.1 .2.2.4 Upper Respiratory Tract Damage ........................................................................................... 5-9
5-2.1 .2.2.5 Lung Damage .......................................................................................................................... 5-9
5-2.1 .2.2.5.1 Smoke Inhalation ............................................................................................................. 5-9
5-2.1 .2.2.5.2 Heated Air ......................................................................-......!....-....................................... 5-9
5-2.1.3 Protective Equipment and Protection Factors ....................................................................................... $10
5-2.1.3.1 Vehicular Requkements ................................................................................................................ 5-I(I
5-2.1.3.2 Protective Clothing ......................................................................................................................5.ll
5-2.1.4 Full-Scale Tests .................................................................................................................................... 5-11
5-2.2 THERMAL INJWRY ASSESSMENT .............................................................................................................. 5-12
5-2.2.1 Data-Gathering Techniques Used in Live-Fire Tests ........................................................................... 5-12
5-2.2.2 Second-Degree Bum Criterion ............................................................................................................ 5-12
5-2.2.3 Vehicle Tests Involving Animals ......................................................................................................... 5-13
5-2.2.3.1 Tests of the LVTP 5A1 ............................................ .................................................................... 5-13
5-2.2.3.2 Tests of Diesel-Fueled APC, MI 13A1 ......................................................................................... 5-14
5-2.2.3.3 Test of Gasoline-Fueled Ml13 APCs ....................JI...................................................................... 5-15
5-2.2.3.4 Tests of Aircrew Uniform Materials ......................?...................................................................... 5-16
5-2.2.3.5 Overall Evaluation of These Animal Tests ................................................................................... 5-17
5-2.2.4 Combat Data from Southeast Asia ...................................................................................................... 5-17
9
5-2.2.4.1 Casualties in ACAVS and Other APC Ml 13 Vehicles ................................................................ 5-17

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5-2.2.42 casualties in MBT’sM48A3 .............................................................................................................5.l7

o 5-2.2.4.3 Casualties in ARIAAV M551 ...........................................................................................................5.l8

$2.2.4.4 Evaluation of SEA Armored Vehicle Fire Casualties ......................................................................5.l8
5-2.3 HUMAN INCAPACITATION ........................................................................................................................5.l9
5-2.3.1 llermal Overload ...............................................................................................................................5.l9
5-2.3.2 Local Site Disability ............................................................................................................................. 5-19
5-2.3.3 Systemic Disability .............................................................................................................................. 5-20
$2.3.4 Other Thermal Effects ..........................................................................................................................5.2o
5-2.3.4.1 White Phosphorus Burns ..............................................................................................................5.2O
5-23.4.2 Oxygen Depletion and Toxic By.HuCS ...................................................................................5.2O
5-2.3.4.3 Flash Btindn=s .............................................................................................................................5.2O
5-2.3.5 Ability of Dynamicrdly Launched Flame and Incendiary Agents to Produce Burns ...........................5-2O
5-2.3.6 Psychological Effects ...........................................................................................................................5.2l
5-2.3.7 Quality of Estimates .......................................o.....................................................................................5.2l
5-3 EAR DAMAGE .............................................................................................................................................................5.2l
5-3.1 THEE/U? ..........................................................................................................................................................5.2l
5-3.2 EAR INJURY LEVELS ...................................................................................................................................5.22
5-3.2.1 Eardrum Rupture ..................................................................................................................................5.22
5-32.2 Temporary Threshold Shift ..................................................................................................................5.23
5-3.3 EAR DAMAGE CRITERIA ............................................................................................................................5.25
5-3.3.1 ‘IT’SCriteria ...................................................................................................................................... .... 5-25
5-3.3.2 Eardrum Rupture Criteria ..................................................................................................................... 5-25
5-3.4 PRESSURE WAVES ASSOCIATED WITH SHAPED-CHARGE JET ........................................................$X
5-3.4.1 Description of Everm ...........................................................................................................................5.26
5-3.4.2 Interpretation of Gage Records .................=..............Y...........................................................................$28
5-3.4.3 Assessment of Potential Injury to Humans in the Referenced Tesu ....................................................5.28
!. 5-4 LUNG DAMAGE .........................................................................................................................................................5.32
54.1 LUNG DAMAGE CIUTEIUA .........................................................................................................................532
o 542 EFT13X OF WEARING BALLISTIC VEST ..................................................................................................5.33
5-4.3 SWG OF PRESS ~mELO~S ..............................................................................................5.36
5-4.3.1 Scaling of Peak Pressure Versus Duration by Lovelace ......................................................................5.36
5-4.3-2 Scaling of Peak Pressure Versus Impulse by SWRI .............................................................................5.37
5-4.4 LOADS FROM A SHAPED-CHARGE JEI’ ...................................................................................................5.38
5-5 EYE DMGE .............................................................................................................................................................5.39
5-5.1 BACKGROUND .............................................................................................................................................$39
5-5.2 INJURY MECHANISMS ................................................................................................................................5-
5-5.2.1 Foreign Bodies .....................................................................................................................................5M
5-5.2.2 Hot and/or Burning Liquid Droplets ...................................................................................................54l
5-5.2.3 Irritant chemicals .................................................................................................................................54l
5-5.2.4 Flash EffWB .........................................................................................................................................54l
5-5.2.5 Concussions and Contusions ................................................................................................................542
5-53 S~Y ......................................................................................................................................................5~2
5-6 ASPHYXIATION, TOXIC GASES, AND PARTICULATE SOLIDS .......................................................................542
5-6.1 HYPOXIA-PRODUCING GASES AND CONDITIONS ...............................................................................543
5-6.1.1 Carbon Monoxide .................................................................................................................................543
5-6.1.2 Hydrogen Cytide ................................................................................................................................5A
5-6.1.3 Carbon Dioxide ....................................................................................................................................545
5-6.1.4 Oxygen Depletion ...............................................................................................................................w5
5-6.1.5 Synergistic Effec~ ................................................................................................................................5x
5-6.2 THE HUUT’ANTGASES AND PARTICULATE SOLIDS ............................................................................547
5-6.2.1 Irritant Gases ........................................................................................................................................547
5-6.2.2 pardcuiate Solids ..................................................................................................................................547
5-6.2.3 Toxic Effects ........................................................................................................................................547
o 5-6.3 OTHER NOXIOUS PRODU~ ....................................................................................................................5A8
5-6.4 DESIGN CIUTERIA FOR SMOKE INHALATION mDumoN ...............................................................54

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5-7 EFFECTS ON I-iSJMANPERFORMANCE ................................................................................................................. 5-49
5-7.1 KNOW, EFFECTS OF COMBUSTION-RELATED S~~I .................................................................... 5-49
5-7.1.1 Effects of Contaminants ....................................................................................................................... 5-49 4
5-7.1.2 Effects of Sound or Blast Waves .......................................d.................................................................. 5-50
5-7.1.3 Effects of Flash or Flying I%rticulates .. . . ............!............ ..................................................................... 5-51
5-7.1.4 Effects of.liieat and Bws ..................................................................................................................... 5-51
5-7.2 GENERAL EFFECTS OF HIGH AROUSAL ON HUMAN PERFORMANCE ............................................ 5-51
5-7.3 OVERVIEW OF DESIGN COUNTERMEASURES ........................................................................................ 5-52
5-7.3.1 Facilitating Cognitive and Motor Performance in a Crisis ................................................................... 5-52
5-7.3.2 Facilitating Escape and Subsequent Survival .................`!..................................................................... 5-53
5-7.3.3 Combat Experience From Southwest Asia ....................y..................................................................... 5-53
REFERENCES .................................................................................................~..................................................................... 5-53
BIBLIOGRAPHY ................................................................................................................................................................... 5-60
CHAPTER 6 :
FIRE DETECTION SYSTE+IS
6-1 INTRODUCTION ............................................................................................................................................. .............. 6-1
6-1.1 BACKGRO~ .....i........................................................................................................................................... 6-1
6-1;2 EXAMPLES OF FIRES TO BE ENCOm~D ........................................................................................... 6-2
6-1.3 FIRE SIGNATURES .......................................................................................................................................... 6-3
6-1.4 DEVELOPMENT OF AUTOMATIC FIRE DETECTION AND EXTINGUISHING SYSTEMS FOR
COMBAT VEHICLES .................................................................................................................................... 6-3
6-2 OPTICAL DE~CTORS ................................................................................................................................................. 6-4
6-2.1 GENEML CHARACTERISTICS ..................................................................................................................... 6-4
6-2.1.1 Sensitivity ............................................................................................................................................... 6-5
6-2.1.2 Respofise Time ................................................................~....................................................................... 6-6
6-2.1.3 False Alarm Rejection .“.................................’.............. ..;.....................- .......................- ......................... 6-7
6-2.1.4 Discrimination ........................................................................................................................................ 6-9
6-2.1.5 DwabiliV ........................................................................l..................................................................... 6-10 a
6-2.2 TYPES .........................................................................................~..................................................................... 6-10
6-2.2.1 Ultraviolet Fire Detectors ..................................................................................................................... 6-10
6-2.2.1.1 Omniguad@ UV Detectors of Armtec ......................................................................................... 6-11
6-2.2.1.2 Det Tronics AOi@Ultraviolet Sensor by Detector Electronics .................................................... 6-12
6-2.2.2 InfraredFire Detectors ......................................................................................................................... 6-13
6-2.2.2.1 Dual Spectrum@Infrared Sensors ................................................................................................. 6-13
6-2.2.2.2 HTL Optical Fire Sensor Assembly ........................~..................................................................... 6-13
6-2.2.3 Combination UV and IR Detector ........................................................................................................ 6-14
6-2.2.3.1 Ornniguard@Model 750 ..........................................#..................................................................... 6-14
6-2.2.3.2 Spectrex Optical Fire Detector ..................................................................................................... 6-14
6-2.3 Application ....................................................................................................................................................... 6-14
6-2.3.1 Number Required ................................................................................................................................. 6-15
6-2.3.2 Location Selection ........................................................i...................................................................... 6-16
6-2.3.3 Standardization ...................................................................................................................................... 6-16
6-3 THERMAL DETECTORS ......................................................................i..................................................................... 6-16
6-3.1 CONTINUOUS THERMAL DETECTORS .................................................................................................... 6-16
6-3.1.1 Types ................................................................................................................................................... 6-17
6-3.1.1.1 Thermistor-Type Continuous Detector ........................................................................................ 6-17
6-3.1.1.2 Continuous Thermocouple Cable .............................................................................................. 6-18
6-3.1.1.3 Eutectic Salt Continuous Detector ............................................................................................... 6-18
6-3.1.1.4. Pneumatic Continuous Detector ................................................................................................... 6-19
6-3.1.2- General Characteristics of Continuous Thermal Detectors .................................................................. 6-20
6-3.1:2.1 Response Time ........................................................~..................................................................... 6-20
6-3.1 .2.1.1 Thermistor-Type Detector ..................................................................................................... 6-21
6-3.1.2.1.2 Continuous Thermocouple Cable ..................... ................................................................... 6-21
6-3.1 .2.1.3 Eutectic Salt Detector ............................................................................................................ 6-21 a

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6-3.1.2.1.4 Pneumatic continuous Detector ...........................................................................................&2l

o 6-3.1.2.2 False Alarm Rejection ..................................................................................................................6-21

6-3.1.221 Thermistor-Type Detector ....................................................................................................62l
6-3.1 .22.2 Continuous Thermocouple Cable .........................................................................................62l
6-3.1 .2.2.3 Eutectic %lt Detector ...........................................................................................................62l
63.1.22.4 Pneumatic htector ...............................................................................................................&22
6-3.1.23 Sensitivity .....................................................................................................................................Gz
6-3.1 .2.3.1 Thermistor-T’ype Detector ....................................................................................................&~
6-3.1 .2.3.2 Continuous Thermocouple Cable .........................................................................................&22
6-3.1 .2.3.3 Eutectic Salt Detector ...........................................................................................................6M
6-3.1.23.4 Pneumatic-Type Detector .....................................................................................................622
6-3.1.2.4 D=b%~ ......................................................................................................................................6E
&3.1.3 Application Suitability of Continuous Thermal Detectom ...................................................................&~
6-3.1.3.1 CID Installation ...........................................................................................................................6~
t$3.1.3.2 Comparative Tests of Several CTDs ............................................................................................6~
($3. 13.3 Lessons Learned ...........................................................................................................................&24
6-3.2 THERMOCOUPLES ........................................................................................................................................624
6-3.2.1 Basic Functioning .................................................................................................................................&24
63.2-2 Thermocouple T~s ............................................................................................................................625
6-3.2-3 Application Suitability of Thenrmcoupks ...........................................................................................&26
6-3.23.1 Reduction of Noiw .......................................................................................................................&26
&3.2.3.2 Performance Degradation tiblems .............................................................................................6ti
63.2.32.1 Joint Connection ...................................................................................................................&26
6-3.2 -3.2.2 ~dibmtion .........................................................................................................................&%
&3.2.3.2.3 Shunt, Impedance and GaIvanic Action ................................................................................6M

0,,
632.32.4 Thermal Shunting .................................................................................................................&26
6-32.3.2.5 Noise and Leakage Cmen~ .................................................................................................&M
632.3.2.6 Physical Damage to the Thermocouple ................................................................................&26
&32.3.3 Advantages and Di4vm@ges ....................................................................................................&26
6-32.3.4 Recommen&tions ........................................................................................................................&26
63.3 THERMOPILE .................................................................................................................................................627
6-3.3.1 Thin-Fiirn Thermopile ..........................................................................................................................627
6-3.3.2 Russian Thermopile ..............................................................................................................................627
6-4 OTHER DETECTORS ..................................................................................................................................................&27
641 PENETRATION D.~OR .........................................................................................................................&27
&4.2 SMOKE DETECTORS ....................................................................................................................................&B
642.1 Photoelectric Smoke ~t=tor ..............................................................................................................6M
6-4.2.1-1 Photoelectric Smoke Detector Used in Cargo Aircraft ................................................................&~
6-42.12 Photoelectric Smoke Detector Used in Commercial Buildings ...................................................&29
6-42.2 Ionization Smoke Detectors .................................................................................................................&29
6-4.3 VARIOUS GAS DET?330RS ........................................................................................................................629
6-4.3.1 Noxious Gas Detecto~ .........................................................................................................................63O
6-4.3.2 Oxygen Detector .................................................................................................................................63o
6-4.3.3 Combustible Vapors and Their Potential Hazards ...............................................................................&3O
6-5 EXAMPLES ..................................................................................................................................................................63l
&5.1 LEOPARD U MAIN BATTLE TANK ............................................................................................................&31
6-5.2 BRADLEY FIGHTING VEHICLES ...............................................................................................................&3l
&5.3 MBT M60A3 ....................................................................................................................................................63l
REFERENCES .......................................................................................................................................................................&32
BIBLIOGR4.PHY ...................................................................................................................................................................GM

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CHAPTER 7
EXTINGUISHING AGENTS AND SYSTEMS 9
7-O LIST OF SYMBOLS ................... ........................................................................................................................................ 7-1
......................................................................................................................................................
7-1 INTRODUCTION 7-1
7-1.1 GENERAL ...................................................................................i......................................................................
~ 7-1
7-1.2 PAST EXPERIENCE ........................................................................................................................................... 7-2
7-1.3 TECHNIQUE FOR AGENT COMPXSON .................................................................................................... 7-5
7-2 AGE~S ...................................................................................................!...................................................................... 7-6
7-2.1 OXYGEN OR FUEL EXCL~ERS .................................................................................................................. 7-6
7-2.1.1 Carbon Diotide ....................................................................................................................................... 7-8
7-2.1.2 Oxygen-Depleted (Vitiated) &r ............................................................................................................. 7-8
7-2.1.3 Nl@ogen .................................................................................................................................................. 7-9
7-2.1.4 Noble Gases .......................................................................................................................................... 7-10
7-2.1.5 Water Vapor (Stem) ............................................................................................................................ 7-10
7-2.1.6 Foams ................................................................................................................................................... 7-10
7-2.1.7 Surfactants ............................................................................................................................................ 7-11
7-2.1.8 Copper Powder ...........................!......................................................................................................... 7-11
7-2.2 CHEMICAL INTERVENTION AGENTS ...................................................................................................... 7-11
7-2.2.1 Alkali Metal Salt Powders ................................................................................................................... 7-12
7-2.2.2 Alkali Metal Salt Aqueous Solutions ................................................................................................... 7-15
7-2,2.3 Halogen-Containing Hydrocarbon Compounds .................................................................................. 7-17
7-2.2.3.1 The Search for Halon Replacements andor Alternates ................................................................ 7-17
7-2.2.3.2 Halon Replacements ..................................................................................................................... 7-20
7-2.2.3.3 HaIon Alternates ........................................................................................................................... 7-20
7-2.2.4 Halogen-Containing Nonhy&ocmbons ................................................................................................. 7-20
7-2.2.5 Other ........................v........................................................................................................................... 7-23
7-2.3 COOLING AGENTS ........................................................................................................................................ 7-23
7-2.3.1 Water ...................................................................................................................................... ............... 7-23 4
7-2.3.1.1 Forms of Fire Extinguishant Water ............................................................................................... 7-23
7-2.3.1.2 Freeze Point Suppressants ............................................................................................................. 7-24
7-2.3.1.3 Surfactants and Foaming Agents .................................................................................................. 7-27
7-2.3.1.4 Conduction of Electricity by Water .............................................................................................. 7-27
7-2.3.1.5 Use of Bulk Water ........................................................................................................................ 7-27
7-2.3.1.6 Use of Water Mist ......................................................................................................................... 7-27
7-2.3.2 Alumina Powder ........................................4.......................................................................................... 7-31
7-2.3.3 Perfluorinated Carbon Compounds ...................................................................................................... 7-31
7-2,3.4 Other ..................................................................................................................................................... 7-31
7-2.4 EXTINGUISHANTS FOR COMBUSTIBLE METALS ~Sl ..................................................................... 7-31
7-3 EXTINGUISHERS ..................................................................................~..................................................................... 7-32
7-3.1 ACTIVE SYSTEMS ......................................................................................................................................... 7-32
7-3.1.1 Fast-Acting Valves ............................................................................................................................... 7-33
7-3.1.1.1 Solenoid ........................................................................................................................................ 7-33
7-3.1.1.2 Squib ......................................................................................................................................... 7-34
7-3.1.2 Manual Valves ...................................................................................................................................... 7-35
7-3.1.3 OtherValves ......................................................................................................................................... 7-35
7-3.1.4 Bottles ................................................................................................................................................... 7-35
7-3.1.5 Linear Fke Extinguishers ..................................................................................................................... 7-35
7-3.2 PASSIVE SYSTEMS ..................................................................~..................................................................... 7-36
7-3.2.1 Hazardous Materials Stowage .............................................................................................................. 7-36
7-3.2.1.1 Munitions Stowage ....................................................................................................................... 7-36
7-3.2.1.2 Mobility Fuel Storage ................................................................................................................... 7-37
7-3.2.1.3 Hydraulic Fluid Systems ............................................................................................................... 7-37
7-3.2.2 Powdered Fire Extinguishant Layer ................................................................................................... 7-38
7-3.2.3 Double-Walled Fuel Cells ................................................................................................................... 7-39 a

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,, 7-32.4 Water Gel Subsystem ........................................................................................................................... 7-40

O 7-3.2.5 Intumescent Paints and Coatings .......................................................................................................... 7-40

7-3.2.6 Other k.enti ............................................................................................................................... 742
7-3.2.7 Fire-Retardant Matetis ....................................................................................................................... 7-42
7-328 Bdge ...................................................................................................................................................... 7-42
7-3.2.9 Other Passive Concepts ........................................................................................................................ 7-42
7-3.2.9.1 Fuel Cell Cofinement .................................................................................................................. 7-42
7-3.2.9.2 Fuel Cell Material and Coti~~tion ........................................................................................... 7-43
7-3.2-9.3 Reticulated Foam Whhin a Combustible Fiuid Confiner ............................................................ 7-43
7-3.2.9.4 Ullage Explosion protection ......................................................................................................... 7-44
7-3.3 HANDHELD EXTINGUISHERS ................................................................................................................... 7-44
7-3.3.1 T~s ..................................................................................................................................................... 7-44
7-3.3.2 Uses ...................................................................................................................................................... 7-44
7-3.3.3 Selection Guidance ............................................................................................................................... 747
7-4 sYsms ...................................................................................................................................................................... 7-47
7-4.1 GENERAL SYSTEM OBJECITVES ............................................................................................................... 7-47
7-4.1.1 Crew Compartment ............................................................................................................................... 7-48
7-4.1.2 Engine and/or Cargo Comp~ent ...................................................................................................... 7-48
7-4.1.3 F~e-Extinguishing System Sumivability ............................................................................................. 74$9
7-4.2 GENEIUL SYSTEM DES~ON ............................................................................................................. 7-49
7-4.2.1 Active Systems ..................................................................................................................................... 7-50
7-4.2.2 Passive SysM ...................................................................................................................................... 7-5o
7-4.2.3 Logic Followed by Current US Army Active Fro-Extinguishing Systems ......................................... 7-50
7-4.3 DISTRIBUTION SUBSYSTEM ...................................................................................................................... 7-51
7-4.3.1 Within the Crew ~mp~ent ............................................................................................................. 7-51
7-4.3.2 Within the Engine andbr Cargo Compartment .................................................................................... 7-54

0 7-4.4 AUTOMATIC ELECTRONIC CONTROL S~SYS~ ............................................................................. 7-54

7-4.4.1 One Sho~ Two Shots, or N Shots ......................................................................................................... 7-54
7-4.4.2 Backups for Automatic Extinguishers and for Automatic Systems ..................................................... 7-55
7-4.4.3 Response R~tiemenw ........................................................................................................................ 7-55
74.4.3.1 Hydrocarbon Fiuids in Mist or Spray Fom .................................................................................. 7-55
74.4.3.2 Explosives, Low and ~gh ............................................................................................................ 7-56
7-4.4.3.3 Other Combustibles ...................................................................................................................... 7-56
7-4.4.4 Buih-In Test Equipment @~) ........................................................................................................... 7.56
7-4.4.5 Test and Alamt tiel ............................................................................................................................ 7-57
74$.5 MANUAL Activation ................................................................................................................................ 7-57
7-4.5.1 Elwm-ical-Manual ................................................................................................................................. 7-57
7-4-5.2 MedtanicahMnnual .............................................................................................................................. 7-57
7-4.5.3 Placement of Activation Handles and Switches ................................................................................... 7.58
7-4.6 ROLE OF HANDHELD .G~S~RS ................................................................................................... 7-58
7-5 EXAMPLES .................................................................................................................................................................. 7-58
7-5.1 COMBAT ~~ES ...................................................................................................................................... 7-58
7-5.1.1 Description of US Army SyWm ......................................................................................................... 7-58
7-5.1.1.1 Ml 13 Armored Personnel Carrier . .. .. .. ... . ... .. ... .. .... .... .. ... ... . .. . .. . .. . .. . . .. ... .. . .. .. .. ... . .. .. .. .. ... . .. ... . .. ... .. .. 7-58
7-5.1.1.2 The M60 Main Battle Tti ........................................................................................................... 7-58
7-5.1.1.3 The Ml Main Battle Tank ............................................................................................................. 7-60
7-5.1.1.4 Bradley Fighting Vehicles M2 and M3 ........................................................................................ 7-61
7-5.1.1.5 Advanced Survivability Test Bed Veticle .................................................................................... 7-62
7-5.1.1.6 Field Artille~ Anrnunition SupporKVehicle M992 .................................................................... 7-64
7-5.1.1.7 Armored Reconnaissance and/or Airborne Assault Vehicle M551 (Sheridan) ............................ 7-64
7-5.1.2 Description of US Marine Coqx Sywem ............................................................................................ 7-65
7-5.1.2. I Landing Vehicle, Tracked, Personnel (LVTP) 5A 1 ..................................................................... 7-67
7-5.1 .2.2 Assault Amphibian Vehicle (AAV) 7A] ...................................................................................... 7-67
7-5.1.2.3 Light-Armored Vehicle (LAV) M ................................................................................................ 7-68
7-5.1.3 Description of Foreign System ............................................................................................................ 7-68

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7-5.1.3.1 Leopard II Main Battle Tank ........................................................................................................ 7-68
7-5.1.3.2 British Axmy Main Battle Tmb .................................................................................................... 7-69
J
7-5.1.3.3 Israeli Combat VeMcles ...........................................j.................................................................... 7-69
7-5.1 .3.4 Russian Tti .........................................................~..................................................................... 7-70
7-5.1 .3.4.1 T-54 MBT .......................................................J.....................................................................
x 7-70
7-5.1 .3.4.2 T-55 MBT .......................................................!..................................................................... 7-71
7-5.1 .3.4.3 Otier ...................................................................................................................................... 7-72
7-5.2 =CH .................................................................................~..................................................................... 7-73
7-5.2.1 Ullage Filler Matefids .......................................................................................................................... 7-73
7-5.2.2 Inerting Systems for the Ullage ........................................................................................................... 7-74
7-5.2.3 Self-Sealing Fuel Cells ......................................................................................................................... 7-74
7-5.2.4 Dry Bay and Void Space Fillers .....................................j..................................................................... 7-74
7-5.2.5 Powdered Fire Extinguishant Panels ...............................l.................................................................... 7-75
7-5.2.6 Fire-Extinguishing Systems ............................................~..................................................................... 7-75
7-5.2.7 Fire-Resis~t Fuels and Hydraulic Fluids .....................i..................................................................... 7-75
7-5.2.8 Adapting Aircraft Fire Prevention Concepts to Combat ~hicles ....................................................... 7-76
7-5.3 SHIPS ................................................................................................................................................................ 7-77
7-5.4 CIVILIAN EQ~ME~ ...........................................................{l..................................................................... 7-78
7-6 LESSONS LEARNED. . .................................................................................................................................................
I
. 7-78
7-6.1 DESIGN CONCE~S EXPLOMD ~.~AS~PROGH ..................................................................7.78
7-6.2 DESIGN CONCE~S USED~FO~IGN T~KS ................j.....................................................................7.78
7-6.3 ~L.m A~OMA~C ~PRO~C~ON .........................................................................................7.78
7-6.4 ~M~I~ON MAG=~DESIGN ..........................................................................................................7.79
REFERENCES ......................................................................................................................................................................... 7-79
BIBLIOGRAPHY .............................................................................................~..................................................................... 743fj
I
I
CHAPTER 8 1!
TEST AND EVALUATION FOR DESIGN ~ERIFICATION
8-O LIST OF SYMBOLS ....................................................................................................................................................... 8-1
8-1 INTRODUCTION ........................................................................................................................................................... 8-1
8-2 PERFORMANCE PARAME TERS THAT CAN BE TESTED ..................................................................................... 8-4
8-2.1 PRESSURE AND TEMPERATURE TIN@ HISTORY .................................................................................... 8-6
8-2.1.1 Hydraulic Ram Pressure Versus Time Recordngs ................................................................................. 8-6
8-2.1.2 Air Blast or Shock Pressure Versus Time Recordings ..i..................................................................... 8-13
8-2.1.3 Recording Temperature Versus Time .............................!..................................................................... S-13
8-2.1.3.1 Thermocouples ............................................................................................................................. 8-14
8-2.1.3.2 Thermistors ............................'.. "....................".".....\..............' ........................' ..........................-." 8-14
8-2.1.3.3 Heat Flux Sensors ...................................................i.................................................................... 8-15
8-2.2 GAS CONCENTRATION ..........................................................\..................................................................... 8-16
8-2.2.1 Fuel and Extinguishant Vapors ............................................................................................................. 8-16
8-2.2.2 Fire By-Products .................................................................................................................................. 8-16
8-2.3 EX’I’JNGUISI-HNGSYSTEM EVENT TIMING .......................!..................................................................... 8-19
8-2.3.1 Threat Functioning ...........................................~.............................................................. 8-19
8-2.3.2 Target Response .................................................................................................................................... 8-20
8-2.3.3 Combustion ........................................................................................................................................... 8-20
8-2.3.4 Extinguisher System Performance ........................................................................................................ 8-21
8-2.3.5 Correlation ............................................................................................................................................ 8-21
8-2.4 ANCILLARY DATA ........................................................................................................................................ 8-21
8-2.4.1 Recording of Rapidly Occurring Even~ ............................................................................................... 8-21
8-2.4.1.1 Photographic Equipment ............................................................................................................... 8-21
812.4.1.2 Electronic Equipment ..............................................i!..................................................................... 8-25
8-2.4.1.3 Examples of High-Frame-Rate Motion Pictures ........................................................................... 8-25
8-2.4.2 Documenting Overall Test Events ...................................................................................................... 8-27 a
8-2.4.3 Value of Photographs ........................................................................................................................... 8-28

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8-25
OTHER ASPECI’S OF FIRE SURVIVABILITY TESTING ......................................................................... 8-29
8-25.1 FW Extinguislmnt Selection ................................................................................................................. 8-29
8-25.2 Fire-Fighting Crews and SOPS ............................................................................................................ 8-31
8-2.5.3 Preparation of Test Specimen and FKture for a Fwe ............................................................................ 8-32
8-3 MODELING .................................................................................................................................................................. 8-32
8-3.1 CREW INCAPAC~ATiON ............................................................................................................................. 8-33
8-3.1.1 First Live-Fro Crew Casualty Assessment Worhhop ......................................................................... 8-33
8-3.1.2 Second Live-Fw Crew casualty Assessment Workshop .................................................................... 8-34
8-3.1.3 Crew Casualty Assessment Reference System ..................................................................................... 8-34
8-3.1.4 JTCG/AS Component Vulnerability Pa Workshop ............................................................................ 8-34
8-3.2 EQUI.PM.ENT DAMAGE ................................................................................................................................. 8-34
8-3.3 FIRE INITIATION ........................................................................................................................................... 8-35
8-3.3.1 FIRESIM ............................................................................................................................................... 8-35
8-3.3.2 PARK AC ............................................................................................................................................. 8-36
8-3.3.3 Predictions of Probabilities of Sustained Fires for Combat-Damaged Vehicles .................................. 8-36
8-3.4 I=lRJ3GROWTH AND ~G~S~G ...................................................................................................... 8-36
8-3.4.1 Model for Predicting the Performance of Halon Fiie-Extinguishing Systems ..................................... 8-37
8-3.4.2 Fluid Flow Computations ..................................................................................................................... 8-37
8-3.4.3 FKe Extinguishment Retictions ........................................................................................................... 8-37
REFERENCES ....................................................................................................................................................................... 8-39
BIBLIOGRAPHY ................................................................................................................................................................... 8-42

GLOSSARY ............................................................................................................................................................................. G-1

INDEX .......................................................................................................................................................................................I.I
SUBJECT TERM (KEY WORD) LISTING ..........................................................................................................................ST.l

0
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MIL-HDBK-684

LIST OF ILLUYIR,ATIONS
Figure
II
No. Title Page
1-1 British Mark IV Tank Viewed From Left Rear .....................................T....................................................................... 1-3
1-2 Reduction in Reticulated Foam Kit Cost Resulting From Simplification and Competition ...................................... 1-1o
2-2 Fuel Flammability Ranges .....................................................................~ .......................................................................2.3
2-3 Qualitative Representation ofl%mmability Limits on Military Mobihty Fuels ........................................................2.3
2-3 Blends of Fuels With Widely Differing Volatile Synergistic Flash Point Effects ......................................................2.3
2-4 Correlation of Theoretical Flash Points With the Flammability Limit Compositions for Standard Military
Mobility Fuels ...........................................................................................................................................................2.4
2-5 Minimum Energy to Ignite Selected Military Fuels in Spray Form .............................................................................2.5
2-6 Spark”Ignition Energy vs Fuel-Air Composition for Various Straight Chain Saturated Hydrocarbons in
Vapor State ................................................................................................................................................. .............. 2-6
2-7 Relative Ignition Temperatures of Heat Sources .........................................................................................................2.6
2-8 Time Sequence From 23-mm HEIT Detonation To Ullage Vapor Combustion ..........................................................2.7
2-9 Effect of Airflow Upon Flame Propagation ..................................................................................................................2.8
2-1o Comparison of Ignition Temperatures of Two Aircraft Fuels With a Heated 5 l-mm (2-in.) Diameter by
610-mm (24-in.) Long Steel Target .........................................................................................................................2-9
2-11 Front Face Splash Emitted by Aluminum2024T81 Sheet When Impacted by a Steel Fragment .............................. 2-9
2-12 Front Face Splash Emitted by a Titanium 6A1 4V Sheet When Impacted by a Steel Fragment ..............................2-lo
2-13 Shaped-Chrwge Jet Perforating Steel Plates on Both Sides of a Test Fixture ............................................................2.lo
2-14, Flash Emitted by RI-IA Steel Taget ............................................................................................................................2.ll
2-1.5 Flash Emitted by Aluminum Target ............................................................................................................................2.ll
2-16 Reaction of Gun Propellant in 105-mm Cartridge to Perforation by a Shaped-Charge Jet .......................................2-12
2-17 Response of Water-Filled Fuel Tank to a Shaped-Charge Jet ...................................................................................2.l5
2-18 Hydraulic Power Supply and Distribution, Ml MBT ................................................................................................2-19
3-1 Typical ChromatographyDistillation Traces of JP-4, JP-8, Jet A-1, DF;,2, and Fog Oil .............................................. 3-5
3-2 Effect of Ivlist,Droplet Size on Burning Speed of Monodispersed Tetr$in-Air Suspension .....................................3-16
3-3 105-mm Cartridge Case After Deflagration of Solid propellant Filler ~trated by a Shaped Charge ....................3-23
3-4 WV M3A0 Stowage Diagram ....................................................................................................................................3.36
4-1 Armored Cavalry Assault Vehicle (ACAV) .................................................................................................................4-8
4-2 M113A3 Showing the Cupola for the .50 Caliber Machine Gun ................................................................................4.8
4-3 “Ml 13A1 APC Hit Pattern, Southeast Asia ....................................................................................................................4-9
4-4 M48A3 MBT and M551 A.WAAV Hit Pattern, Southeast Asia ................................................................................4.lo
4-5 I
Rear View of BTR-60 ....................................................................................................................................... .......... 4-16
4-6 BTR-60 Fuel System Schematic ................................................................................................................................. 4-17
II
4-7 Rear View of BMP-2 4-17
.........' ........................~..........................................(...."........................'.......................................
4-8 BMP-2 Fuel System ......................................................................................................................................... ............. 4-18
4-9 View of Aluminum ASTB Engine Compartment Fuel Cell Bottom an~ Rear Showing Weld Failures ....................4-20
4-10 Front View of Aluminum ASTJ3 Engine Compamment Fuel Cell Sho+ing Weld Failure at Seam Between
Front and Bottom Faces ."...........".........."........"............."....... ...."......".."" ti
......."....................".....................................4-20
4-11 Stainless Steel Engine Compartment Fuel Cell After Penetrauon by a Shaped-Charge Jet From an M28A2
Warhead ................................................................................................................................................ ................... 4-20
4-12 Ruptures in a Plastic (Nylon 6) Fuel Cell After Penetration by a Sha~ed-Charge Jet From an 81-mm BRJ.,
Precision Warhead ................................................................................................................................................... 4-20
4-13 A Crashworthy Caliber .50 Fuel Cell Penetrated by a Jet From an 8 l@n BRL Precision Shaped Charge ............4-21
4-14 Exit Holes in Jacket and Fuel Cell Wall After Penetration by the Jet of an M28A2 Warhead ................................4-21
4-15 Confinement Box Used With Test Cells ........”................-.......-.”...............”....””........................................................... 4-21
4-16 Fuel Cell Failure at Access Plate ............................................................’.....................................................................4-22
4-17 j
Fuel Cell Failure Near Access Plate ....... ..................................”............j.”................................................................... 4-22
4-18 Jet Penetration Through Simulated Velucle Armor, Crew Compartment, and Fuel Barrier Into Fuel Cell ...............4-22
4-19 Fuel Drainage From Fuel Barrier ................................................................................................................................4.22
4-20 Two Examples of an Aluminum Engine Compartment Fuel Cell Hit by a Kinetic Energy Pene~ator
After the Penetrator Passed Through the Vehicle Hull ....................!.....................................................................4-22

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Title
fJ ~21
Perforation in Self-Sealing Hose Coupling That D1d Not SA ...................................................................................4fi
4-22 External, Rear-MountetL Armored Fuel Cell of the Mark IV Tmk ............................................................................&26
4-23 Progression of Combustion in Test No. 26 ................................................................................................................4M
4-24 SPH MI09A6 Paladin Mdtications ..........................................................................................................................432
4-25 Damage to Stainless Steel and Aluminum Tuting ......................................................................................................436
4-26 Hit pattern, MBT in Defense, Direct-Fn, High-Velocity Gun and Rocke@ropelled Missile .................................4-44
4-27 Hit Pattern, From Tanks, Antitank Guns, and Wwe-Guided, Rocket-propelled Mksiles Upon MBTs
Usually in the A~ck ..............................................................................................................................................Q5
4-28 Ammunition Stowed in Recesses in Fuel Cell of T-62 MBT ....................................................................................W
4-29 Ammunition Stowage in Ml and MIA1 ~Ts ..........................................................................................................M8
4-30 Rolled Homogeneous Armor (RHA) Penetration of a Side-Initiated M830 HEAT Warhead ....................................4-49
4-3 I Types of Antifratricide Devices .................................................................................................................................~9
4-32 Ammunition Stowage for the ASTB ...........................................................................................................................45O
4-33 Turbine-Driven Fuel Pump for the Ramjet RJ43 En@ne ............................................................................................452
4-34 Truck-Mounted Flamethrower Powered by the Turbine-Driven Fuel Pump ..............................................................452
4-35 Ballistic Shield on Scale Model Crew Compartment .................................................................................................ti2
4-36 Posttest Condition of Scale Model Oew Compartment .............................................................................................ti2
4-37 Posttest Condition Showing Bulged Missile Confiner ..............................................................................................ti3
4-38 Fuel Cells From Tests No. 2 and 3 ..............................................................................................................................463
4-39 Fuel Cells From Tests No. 4 and 5 .............................................................................................................................463
4-40 Five-Gallon Water-Filled Can After Test No. 10 .......................................................................................................M5
4-41 Slug Plugging Hole in Troop Compartment Wall of the APC M113A3 ....................................................................467
4-42 Russian ‘1’34/85Tank Showing Jettisonable Fuel Qll ................................................................................................468
4-43 Russian Joseph Stalin HI (JS-3) Heavy TA ..............................................................................................................468
Test No. 3 Showing Jettisoned Fuel Cell ...................................................................................................................469
445 Posttest Condition of Frangible, External Fuel Cells .................................................................................................469
0“
5-1 Skin Response From Temperatum Exposure .............................................................................................................. 5-7
5-2 Radiant Energy Required to Cause Flash Bums .......................................................................................................... 5-8
5-3 Temperature Traces for 7-s Exposure TesK ................................................................................................................5.16
5-4 Mean Cliniczd (Gross) Grade for Each High-Temperature Fabric and/or Configuration ..........................................5-16
5-5 The Human Ear ...........................................................................................................................................................5.2l
5-6 Audibility Curve and Eardrum Rupture Pressure for Man .........................................................................................5.~
5-7 Representative Trace of Sound Pressures Showing Both “A and “B’ Durations .....................................................5.24
5-8 Temporary ‘Ilweshold Shift Curves .............................................................................................................................5.24
5-9 Shocks From Jet to Ear @ects ..................................................................................................................................5.24
5-1o Peak Sound Pressure Levels and “B’ Duration Limits for ITS .................................................................................%M
5-11 Ear Injury 6teria ........................................................................................................................................................5.26
5-12 Test Installation ...........................................................................................................................................................5.27
5-13 Shock Wave From Shaped-Charge Jet ......................................................................................................................5.27
5-14 Vector Diagram of Velocities of Shaped-Charge Jet and Shock Wave ......................................................................5.27
5-15 Pressure Versus Tne, Tests 1,2,3, and 4 ..................................................................................................................5-29
5-16 Side-On Pressure Versus Side-On Impulse for Ears ................................................................................................. 5-31
5-17 Reflected Pressures Versus Reflected Impulse for Ears ..............................................................................................5.3l
5-18 Example of Graphic Extrapolation of ‘Effective Peak pressure” ...............................................................................5.33
5-19 Lung Stival Curves With Free-Stream Pressures Propagating Parallel to the Long Axis of the Body ................5-34
5-20 Lung Survival Curves With Body Near a Reflecting Sufi=e .....................................................................................5.35
5-21 Bowen Pressure-Duration Injury Criteria ...................................................................................................................5.35
5-22 Probability Plot of Percent Incapacitation for Lung Injury ........................................................................................5.36
5-23 Log Robit Plot for Lethality Following Blast Exposure ............................................................................................5.37
5-24 Scaled Pressure-Duration and Partial-lrnpulse Analyses of Animal Tolerance .........................................................5.37
5-25 Survival Curves for Lung Damage to Man ..................................................................................................... ..........5.38
,:
0 5-26 Lung Damage Potential From Test Data of Reflected Pressure Versus Reflected Impulses ......................................5-39
5-27 The Eyeb41 ...................................................................................................=..............................................................54

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Figure
No. Title Page
6-1 Electromagnetic Radiations From JP-4 Burning at Sea Level .....................................................................................6.3 a
6-2 Probability of Vehicle Survival Given Multiple Hits for Three AFES ~onfigurations .............................................6-lO
6-3 Ultraviolet Spectral Transmission Through Various Window Glasses lWhen New ....................................................6.l 1
/
6-4 Edison” W Detector Tube’ ..................................................................~.....................................................................6.l2
6-5 Omnigutid@ Model 652 Ultraviolet Fire Detector ................................'......................................................................6.l2
6-6 Series 650 Fire Detector Horizontal Performance Envelope (Cone of Vision) ..........................................................6.l2
6-7 Geiger-Mueller-Type Sensor .......................................................................................................................................6.l2
6-8 W Fire Sensor Cone of Vision ..................................................................................................................................6l3
6-9 W Dectector Sensitivity to a Gasoline Reference Fire .............................................................................................6.l3
6-10 Dual IR Sensor Plus a Thermopile Sensor Assembly ..........................i......................................................................6.l3
6-11 Combination UV-LR Flame Detector, Omniguard @Model 750 ...............................................................................6.l4
6-12 Typical Hydrocarbon Fire Emission Spectrum Showing Detection Regions of Omniguard @Model 750 ................6-14
6-13 Fire Suppression System of the Ml MBT Engine Compartment ................................................................................6.l5
6-14 Fire Suppression System for Al and A2 Configurations of BFVs M2;and M3 ..........................................................6.l5
6-15 Comparative Outputs Versus Inputs for Thermistors, Resistance Thermocouple Detectors (RTD),
and Thermocouples .................................................................................................................................................6l6
6-16 Graviner Firewire@.......................................................................................................................................................6.l7
6-17 Typical Temperature Ranges for Graviner Firewire@ ................................................................................................6.l7
6-18 Family of Curves From Armtec Continuous Thermistor Sensor Elements ................................................................6.l7
6-19 Continuous Thermocouple Cable ................................................................................................................................6.l8
6-20 Eutectic Sensing Element ...........................................................................................................................................6.18
6-21 Systron Dormer Model 808-DRV Pneumatic Continuous Detector ............................................................................6.l9
6-22 Typical Pneumatic Sensor Performance Curve ..........................................................................................................6.2O
6-23 Typical 6-m Long Pneumatic Detector Performance .................................................................................................6.2O
6-24

6-25
6-26
Typical Eutectic Response Times Without Air Movement Across Sensors for a Specified Alarm
Temperature of 204° C (400”F) ...............................................................................................................................6.22
Typical Fiiewire” Installation in Combat Vehicle (Leopard II) ..................................................................................6.24
Typical Thermocouple Temperature and Voltage tiges ...................!......................................................................6.25
a
6-27 Thermocouple Sensing Elements ..............................................................................................................................6.25
6-28 Thermocouple Time Constants ....................................................................................................................................6.25
6-29 Typical Thermopile Sensor Used in Russian T-55 MBT ............................................................................................6.27
6-30 Wire Grid Detector ........................................................................................................... ..........................................6.27
6-31 Continuous Wire Grid System of LVTP 5A1 ......................................!.....................................................................6.28
6-32 Leopard II Crew Bay Fire Detection and Suppression System ..................................................................................6.3l
6-33 Fue Detection System Designed for the M60A3 MET ...............................................................................................6.3l
7-1 H arnmmability Envelope Illustrating Influence of Water Vapor on D~esel-Fuel-Vapor-Air Mixture
Flammability ..........................F................................................................................................................................ 7-2
7-2 Overpressure Resulting From Combustion in Ullage of Fuel Cell Containing JP-4 Given a 23-mm
HEIT Projectile Detonation ...................................................................................................................................... 7-9
~1
7-3 Freezing Point of Water-GS 4m Solution ...............................................................................................................7-25
7-4 Difference in Carbon Monoxide Buildup Due to Water Mist Scrubbi~O ,Ie .................................................................. 7-28
7-5 Difference in Hydrogen Chloride Buildup Due to Water Mist Scmbbjng ..................................................................7.~8
7-6 Difference in Carbon Dioxide Buildup Due to Water Mist Scrubbing~ ......................................................................7-29
7-7 Effect of WaterPressure on Droplet Size for Various Flow Rates ......II.......................................................................7.29
7-8 Temperature Increase With and Without Water Mist ........................{......................................................................7.3o
7-9 Effect of Water Flow Rate on Heat Absorption ........................................................................................4.................7-30
II
7-10 MV 7A 1 Automatic Fire Sensing and Suppression System .............~.......................................................................7.32
7-11 AAV 7A1 Halon Dispersement ...........................................................~......................................................................7.32
7-12 Typical Solenoid Valve and Bottle Assembly ..............................................................................................................7-33
7-13 Solenoid Valve Schematic ..........................................................................................................................................7-33
7-14 Marotta Scientific Controls, Inc., Valve With Mechanical Override ..........................................................................7.34
7-15 Protractor Valve Schematic. ........................................................................................................................................7.34 a
7-16 “AIOSeries Deluge Valve ............................................................................................................................................ 7-35

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Fiwre

o iv:
7-17
7-18
lhle
Installation for Fire-Lamm Tests ................................................................................................................................7.38
Substrate Temperature-Time Histories for AcruaI kttumescent Formations ...............................................................74l
MY

7-19 Portable Fire Extinguisher, Water T~ .......................................................................................................................7~5

7-20 Standard Electronic Control Mdule ............................................................................................................................7.5l
7-21 Block Diagram of Typical AFES Confi~tion ........................................................................................................ 7-52
7-22 Extinguisher Activation Logic ....................................................................................................................................7.53
7-23 M992 FA.ASV Engine Bay Test and AIarm Pael ......................................................................................................7.M
7-24 Line Drawing of MIA1 MBT ..................................................................................................................................... 7-60
7-25 Photograph of MIAI MBT .........................................................................................................................................7a
7-26 M2Al Infantry Fighting Vehicle (WV).......................................................................................................................74l
7-27 M3A1 Cavalry Fighting Vehicle (m) ......................................................................................................................7+2
7-28 ASTB IFV Concept 163 ..............................................................................................................................................743
7-29 ASTB CFV Concept 165 ............................................................................................................................................ 7-63
7-30 Layout of Ammunition Compartment Sensors and Extinguisher Bottles on the FAASV ..........................................7.&I
7-31 FAASV ~ .............................................................................................................................................................7.65
7-32 Armored Reconnaissance/Airborne Assault Vehicle w51 ........................................................................................7.fi
7-33 Shaped-Charge Jet Trajectories in Two Incidents Jnvolving ARJAAV M551 in Southeast Asia ..............................7-66
7-34 LVTP 5AI ...................................................................................................................................................................747
7-35 AAV 7Al .....................................................................................................................................................................747
7-36 USMC Light-&mored Vehicles: LefL LAV 25 With 25-mm Chain Gun; Righ4 Logistics Variant ......_................7-68
7-37 Spectronix Automatic Fiie-Extinguishing System in the MBTs of Several NATO Counties and the
Merkava MBT .................................................................................................................................... .................... 7-69
7-38 Freed Fn-Extinguishing System for T-54 ~T ........................................................................................................7.7o
7-39 Free-Extinguishing System for the T-55 T@ ............................................................................................................7.72
7-40 Russian T-55 MBTs Showing Jettisonable Fuel Drums .............................................................................................7.73

0
‘,, 7-41
742
Explosive Dkpersion Tube Schematic ....................................................................................................................... 7-75
Dispersion Tube Bladder Funtiotig ........................................................................................................................ 7-76
8-1 Major Decision-Making Support Systems and Key btemctiom ................................................................................ 8-1
8-2 Requirements Generation System .................................................................................................................................8.2
8-3 Inappropriate Test Instrumentation Location ................................................................................................................8.4
&4 Jet Enrg Hole and Fragment Impacts From Staac-Fmed M28A2 Warhead Placed at 45-deg Obliquity to a
Heavy-Walled Fuel Cel ...........................................................................................................................................8.5
8-5 Test of Actual Fuel Cell ................................................................................................................................................8.5
8-6 Damage t.oFuel Cell Shown in Fig. 8-5 .......................................................................................................................8-6
8-7 Hydraulic Ram Buffering Test ......................................................................................................................................8.7
8-8 Typical Recordings Made With Pressure Tmnsducers Configured as Shown on Fig. 8-7 ...........................................8-8
8-9 Hydraulic Ram Pressures Recorded Using a PCB 102AO3Piezoelectric Prwsure Transducer ..................................8-8
8-10 Hydraulic Ram Pressure From an Underwater Blast Transducer .................................................................................8.9
8-11 Strain Gages on External Surface and Underwater Blast Gages on Internal Surface of Fuel Cell Fixture ..................8-9
8-12 Hydraulic Ram Pressures Recorded Using Underwater Blast Gages Cemented to an Aluminum Wall WMI a
Biaxial Strain Gage on the Outside ........................................................................................................................&lo
8-13 Hydraulic Ram Pressures From a Shnped-Clutrge Jet Passing Through a Fuel Cell Measured With an
Underwater Pressure Transducer ............................................................................................................................8.ll
8-14 Hydraulic Ram Pressures in a Fuel Cell Impacted by a Shaped-Charge Jet Measured With a Piezoelectric
Pressure Transducer ..............................................................................................................................................8.ll
8-15 Ressure Transducers ...................................................................................................................................................8.l2
8-16 collapsed Fuel Line Within Aimraft Wmg Integral Fuel Cell ....................................................................................8.l3
8-17 Piezoehxtric Pressure Transducer Mounted in Stagnation Plate for Test Fixture Air Shock Pressure
Determinations ........................................................................................................................................................8.l3
8-18 Heat Flux Sensors ....................................................................................................................................................... 8-15
,! 8-19 Installation Showing Test Specimens, Mann Gun, and Whd MacMne ..................................................................... 8-20
8-20 Fragments Showing Different Rupture M&es ............................................................................................................8.2O
0
8-21 Streak Picture of Booster for 23-mm HEIT Projectile Detonating .............................................................................8.22

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Figure !!
No. Title ~ Page
8-22 Frames of Detonation of the Booster of a 23-mm HEIT Projectile ......~.....................................................................8.22 a
8-23 Framing Rate Versus Elapsed Tlrne and Linear Footage for Hycarn@Using a 122-m (400-ft) Reel ......................... 8-23
8-24 Three Sequential Frames From Motion Picture of Test No. 1 of Ref. S~ ,. .................................................................... 8-23
8-25 Sequential Pictures of.a 23-mm HEIT Perforating a Stainless Steel T~get ...............................................................8.24
8-26 Flash X Ray of Static Detonation of a 23-mm HEIT Projectile ..........~!.....................................................................8.25
8-27 Fire Extinguishant Purple K Dissemination ................................................................................................................8.26
8-28 Test Site Installation ....................................................................................................................................................8.28
8-29 Installation for Testing .............................................................................................................................................. 8-28
8-30 Vehicles Impacted by Large HEAT Warheads in SWA .............................................................................................8.29
8-31 Installation Showing Carbon Dioxide Piping and Fog Nozzles Positioned to Extinguish JP-5 Fire .........................8-30
8-32 Regression of Test Data to Provide a Prediction Equation of ResiduaWelocity for Projectile Penetration ..:...........8-33
8-33 Extinguishing Effectiveness Versus Particle Diameter for the Extinction of the N-Heptane Pan Fire ......................8-38
8-34 Flame Extinguishing Effectiveness Versus Particle Size for Large Pticle Sizes of Hydrated
Extinguishants ..................................................................................~.......................................................................&38

,.

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MIL-HDBK-684
LIST OF TABLES

O,’ T&k
No.
1-1
Title
Estimated Extinguisher System Effectiveness .............................................................................................................. i-9
P&&

2-1 Propeties of Simple Hydrocarbons ..............................................................................................................................2.6

‘2-2 Penetrator or Jet Trajectory, Fuel Form, and Primary Ignition Source .......................................................................2.l8
2-3 Flame Ropagation Rates in Fuels at Various Temperatums ......................................................................................2.22
24 Inspection Data for Selected Hydraulic Fluids ...........................................................................................................2.23
3-1 Dksel Fuel Parameters From TUB ...............................................................................................................................>3
3-2 Aircmft Turbine Fuel Parameters From Test ................................................................................................................3.4
3-3 Nato Fuel Designations and US Equivalent Specifiuitions/Standards ..........................................................................3.7
34 Russian Gost 305 Auto Diesel Fuels .............................................................................................................................3.8
3-5 Fuels Wed in Army Materiel .......................................................................................................................................3.9
3-6 Hydraulic Fluids Parameters .......................................................................................................................................3.lI
3-7 Response of Various Hydraulic Fluids to High-Pressure Spray Ignition (Federal Test Standard 791B
Method 6052) .........................................................................................................................................................3.l5
3-8 Response of Various Hydraulic Fluids to Brdlistic Impact of 20-mm HEIT Ammunition ........................................3-17
3-9 Effect of Atomizing Pressure on Mist Flammability ................................................................................................3.l8
3-10 Typical Properties of Selected LubriaK ...................................................................................................................3.l9
3-11 Pertinent Properties of Selected ti~llmE ................................................................................................................3.M
3-12 Pertinent Properties of Explosives ..............................................................................................................................3.27
3-13 Conductor Application and Insulations .......................................................................................................................3.3o
3-14 Fire Hazad of Seats ....................................................................................................................................................>M
3-15 Properties of Plastic and Elastic Materials Including Fillets and Fue-Retardant Additives ......................................3-41
3-16 Pertinent Properties of Fibers, Paper, and Uatir ......................................................................................................347
3-17 Toxicological Effects of Fw Gases ............................................................................................................................348
4-1 Summary of Vehicle Fire Survivabili~ SM&tim .........................................................................................................43
!, 4-2 Fire and Nonllre IncidenE .............................................................................................................................................46
0
4-3 Elastomeric MateriaIs timpatibiti~ ...........................................................................................................................437
44 Estimates of Sensitivity of Explosive-Filled Objects and probable Reaction to Potential Threats ..................._......443
4-5 Insensitive High Explosives ........................................................................................................................................453
4-6 Standard Laboratory-Scale Flammability Test h@m .........................................................................................4.58
4-7 Fkmnmability Properties of Materials TypicaJly Used in Combat Vticlw ................................................................459
4-8 Toxic Products That May Be Produced From Selected Materials Undergoing .pyrolysis or Combustion .................4-60
4-9 Char Yield For Selected Polymers .............................................................................................................................46l
5-1 Approximate Range of Values of the Coefficient of Heat Transfer Between a Solid Surface and a Fluid ..................5-5
5-2 Percent of Body Surface Area For AddS .....................................................................................................................>6
5-3 Relation Between Carbon Monoxide Concentration and Human Response ..............................................................5.lO
54 Reaction of Fabrics to Heat ........................................................................................................................................5.ll
5-5 Thermal Equivalency Table for Second-Degree Burn of Skin ...................................................................................5.l3
% Times for Reflections of Shock Waves to Reach Pressure Transducers .....................................................................5.28
5-7 Hazardous Concentrations of Major Toxicants Generated by Thermal Decomposition of Materials ........................5-44
5-8 Human Response to Various Concentrations of carboxyhemoglobin .......................................................................545
5-9 Physiological Response of Humans to Various Concentrations of Hydrogen Cyanide in Air .......-...........................545
5-10 Human Physiological Effects From Various Levels of Carbon Dioxide ...................................................................5M
5-11 Human Physiological Effects of Reduced Levels of Oxygen ......................................................................................M
5-12 Volatile Combustion Products of Polyvinyl Chloride Smple .....................................................................................X
6-1 Fire Cases, Signatures, and Required Detector Responses ...........................................................................................65
6-2 False Alarm Stimfi .......................................................................................................................................................&7
63 Typical Armtec UV/TRFR Detection Distance ........................................................................................................&l2
64 Thermocouple Mamri* ..............................................................................................................................................&~

0‘:, 6-5
7-1
7-2
Interfemnts for Carbon Monoxide Detector ...............................................................................................................&3O
Fiie Extinguisher System Evaluation ............................................................................................................................7.3
Dominant Fn-Ext@guishing Mechanism of AgenB .....................................................................................................7%

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MIL-HDBK-684 ,
Table
No.
7-3
‘7-4
Diluents to Render a Space Nonfl~able
Title Page
.................................................................................................................. 7-7
Properties of Dry Chemicals and Products ~ereof ..............................~....................................................................7.l3
a
7-5 Relative Effectiveness of Aqueous Solutions of Alkali Metal Salts Us~d TOExtinguish Gasoline Pan Fires ...........7-16
7-6 Minimum Concentration of HaIons Requked for Inerting All Concen~ations of Heptane in Air .............................7- 18
7-7 Compliance of Selected l-hlons to Military Chmactefistics ........................................................................................7.l9
7-8 Approximate Lethal Concentration for Selected Hdons .......................t.....................................................................7.2O
7-9 Preliminary Evaluation of Halon Replacements Compared to the Two Principal Haloes ...................................... 7-21
7-1o Properties of Halon Replacements ............................................................................................................................7.22
7-11 Data for Water and Its Freeze Point Suppressants ......................................................................................................7.26
7-12 Effect of Superheating on Water Droplet Size.. ..........................................................................................................7.29
7-13 Effect of Dissolved Carbon Dioxide on Water Droplet Size .....................................................................................7.3o
7-14 Dry Chemical Usage in Portable Extinguishers ..............................................4.......................................................... 7-46
7-15 US Combat Vehicle Fire Suppression System Characteristics ............+.....................................................................7.59
8-1 Summary for Analytical Methods for Fire Gases ........................................................................................................8.l8
8-2 Comparison of Predicted Extinguishing Concentrations With Experimental Values From Literature
(Finely Divided Solids and Liquids) ................................................................................................................... 8-39

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MIL-HDBK-684

LIST OF ABBREVIATIONS AND ACRONYMS

o AAv
ABs
=
= amphibious assault vehicle
acrylonitrile butadiene styrene
CRES =
Cs=
comosion-resistant steel
ChSoracetophenone solution
AC = hydrogen cyanide CST = cardiac sensitivity threshold
ACAV = armored cavaby assault vehicle m= continuous thermai detector
ACGIH = &wrican Conference of Governmental CrFE= chlorotriiiuoroethylene
Industrial Hygienists Cvc = combat vehicle crewman
ACV = axmored combat vehicle DAN = document acquisition number
AEHA= US-Y Environment Hygiene Agency DF = diesel fuel
AEv= armored engineer vehicle DIGL-RP = diglycol rocket propellant
AFDSE = automatic 6re detection and suppression DIVAD = division aix defense
equipment DoD = Department of Defense
AFEs= automatic fire-extinguishing system DU = depleted uranium
AFFF= aqueous film-forming foam EBw = exploding bridgewire
AFsss = automatic fire+msing and suppression EMI= electromagnetic interference
system emp = electromagnetic pulse
AIT= autogenous ignition temperatm = electromagnetic radiation
AP= armor piercing E% = Explosive Ordnance Disposal
APc= armored personnel carrier EP= end point
APDS = armor-piercing, discarding sabot EPA = Environmental Protection Agency
APFSDS = armor-piercing, fin-srabfixe~ discarding ETo = European Theater of Operations
sabot F = fast
APO= Aberdeen Proving Ground FAA = Federal Aviation Administration
APHEl = armor-piercing, high-explosive incendi- FAASV = field artiliery ammunition support vehicle
ary FAE = fuel-air explosive

,, APIT
=
API = armor-piercing incendiary
armor-piercing, incendiary tracer
FDES =
FFEs =
fire detection and extinguishing system
fixed fire extinguisher system

o Mu =
AR/AAv =
auxiliary power unit
armored reconnaissancehirborne assault
vehicle
FFFP=
FMP =
FoV =
film-forming fluoroprotein
fright motor propellant
family of vehicles
ARv = armored reconnaissance vehicle FRF= fire-resistant fuels
ASM = armored systems modernization FRH= fire-resistant hydraulic
Am = Advanced Survivability Tmc Bed FSES = fire survivability enhancement systems
ASTM = American Society for T=ting and Materi- FSI = Fme and Safety International
als FY= fiscal year
AT = antitank GB = tin
AVLB = armored vehicle launch bridge GD = soman
BDARP = Battie Damage Assessment and Repair GFI = ground fault imemupters
Program GLT = grade G, low temperature
BDU = battle dress uniform GWP = global warming potential
BFV = Bradley fighting vehicle HC = bexachloroethane
BITE = built-in test equipment HD= rhickened mustard
BMEP = brake mean-effective pressure HE= high explosive
BMP = brortevaya maschina pickhota HEAT= high-explosive antitank
BRDEC = US by Belvoir Research, Develop HEAT-T-NIP = high+xplosiv% antitank, tracer, multipur-
men~ and Engineering Center pose
BRL = US Army Ballistic Research Laboratory HEF= high-expansion foam
CBV = cloth ballistic vest HEI= high-explosive incendiary
BTR = brone transporter HEIT= high-explosive incendiary tracer
CE= chemical energy HEY= high-explosive plastic
CEL= cumulative expected 10ss HESH = high-explosive squash head
CEv= combat engineer vehicIe HE-T = high-explosive ttacer
CI= compression ignition Ems = high-impact polystyrene

,,:
O
COIN =
cows
CPI =
=
counterinsurgency
continental United States
consumer price index
IBP =
IDLH =
w=
initial boiling point
immediately dangerous to life or health
infantry fighting vehicle
F= counts per second IM= insensitive munitions
...
mull
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MIL-HDBK-684
Et= infrared RPO;A = rocket-propelled flamethrower-airborne
m= inhathoracic pressure I@= recoilless rifles
JP= jet propellant RTD = resistance thermocouple detector 9
JTCG-AS = Joint Technical Coordinating Group for s= slow
Aircraft Survivability s+ = Society of Automotive Engineers
KE= kinetic energy SARS = Standard Army Refueling Systems
LAN-L = Los Alamos National Laboratory SAVA = Standard Army Vetronics Architecture
LAV = light-armored vehicle SBRC = Santa Barbara Research Center
LAW = light antitank weapon s@ = silicon control rectifier
LEL = lower explosive limit SEA = Southeast Asia
LFT = live-fire test SIG = specific gravity
LGP = liquid gun propellant SHF = single hydraulic fluid
LOI = limiting oxygen index S1 = spark-ignition
LOVA = low-vulnerability ammunition SOP = standard operating procedure
Lox = liquid oxygen S~H = self-propelled howitzer
LVTP = landing vehicle, tracked, personnel STANAjG = Standardization Agreement
MAP = monoammonium phosphate STEL = short-term exposure limit
MAW = medium antitank weapon S1-ljc = short-term lethal concentrations
MBT = main battle tank S/l? = subroutine
MIX = manual discharge system SURVIAC = Survivability/Vulnerability Information
MK = mark \ and Assessment Center
MOGAS = motor gasoline Susv = small unit support vehicle
MOPP = r@sion-oriented protection posture SWA = Southwest Asia
MRI = magnetic resonance imaging TACOM = US Army Tank-Automotive Command
MSEC = module, standard electrical control T-COM = US Army Tank-Automotive Research and
NASA = National Aeronautics and Space Admini- II Development Command
stration. qc = track commander
NATO = North Atlantic Treaty Organization T($P = tricresyl phosphate
NIX = nuclear, biological, and chemical id = troland
NFPA = National Fire Protection Association ‘@A = rnethylaluminum “4
MST = National Institute of Standards and Tech- TE14!A= Terminal Effects Research Activity
nology T$7 . threshold limit value
NV/c = Naval Weapons Center ~B = trimethoxyboroxine
OCONUS = outside the continental United States ~= trinitrotoluene
‘OD = outside diameter TOfV = tube launched, optically tracked, wire
ODP = ozone depletion potential guided ~.
OFSA = optical fire sensor assembly TRADq,c = US Army Training and Doctrine Com-
OVE = on-vehicle equipment mand
OVM = on-vehicle material ‘n& = tracked recovery vehicle
PARK AC = parked aircraft T-p = temporary threshold shift
PBI = polybenzimidazole TWA = Trans World Airlines
PBX = plastic bonded explosive p= ultrafast
PETN = pentaerythritol tetranitrate qK = United Kingdom of England, Scotland,
PG = propylene glycol I and Northern Ireland
POL = petroleum, oils, and lubricants qs = United States
ppm = pails per million US* = US Air Force
m= polytetratluoroethylene USASC = US Army Safety Center
PTs = permanent threshold shift USMC = US Marine Corps
Pvc = polyvinyl chloride USN = US Navy
QPL = qualified products list USNSC = US Navy Safety Center
RAE= Royal Aircraft Establishment UuF= ultra ultrafast
FLKF= Royal Air Force Uv= ultraviolet
REME = Royal Electrical and Mechanical Engi- Vc = Viet Cong
neers VEESS = vehicle engine exhaust smoke system
RHA= rolled homogeneous armor w-P AFB = Wright-Patterson Air Force Base
RPG = rocket-propelled grenade WP= white phosphorus
RPo = rocket-propelled fl~ethrower

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MIL”I’IDBK-684

o CHAPTER 1
INTRODUCTION
The general purpose and objective of this hanclbook are stated The scope and appiicotion of the handbook are also stated
The use of combos vehicles is reviewed, as are the threats to those vehicles. A design philosophy is given that can result in
highly sum”va.ide combat vehicles. 7%e contents of the remaining chapten are described

1-0 LIST OF SYMBOLS support costs through reduced Ike damage to vehicies and
A = availability, i.e., probability that the vehicle is in a
equiptnenL
ready state al a random point in time, or opera-
tional reaches% dimensionless
1-2 SCOPE
C = capability, i.e., a measure of the ability of the ‘Ms handbook is intended to organize and consohiate
vehicle to achieve its mission performance objec- documentation on technologies and techniques suitable to
tives, or design adequacy, dimensionless make combat vehicles more resistant to fire and to minimize,
CER = cost-effectiveness ratio, i.e., system effectiveness the effects of fires on the vehicles and their crews.
divided by vehicle COSL.5US-* This handbook contains data on
P sF = probability a sustained fire will resul~ disnension- 1. Materials used in combat vehicles with emphasis on
less their ignition and flammability chasactetitics
P~~c~c= probability a sustained fire will result when an 2. Available fire-reduction techniques and -eminguish-
external fuel cell is used, dimensionless ing systems
P = probability a sustained fire will result when an 3. Past experience with combat vehicle fires, materi-
‘FIFC
internal fuel cell is usecl dimensionless als, and components
R = reliability, i.e., conditional probability that rbe 4. Suwivability enhancement testing
vehicle can complete a defined mission under 5. Computer models used to predict fire survivability
o specific conditions, or dependability, dimension- performance.
less Clothing can enhance the survivability of the crew. Comb-
SE = system effectiveness, dimensionless at vehicle designers, however, should not depend upon
VC = vehicle cost or cost of vehicle plus the fire surviv- such clothing to meet the fire survivability design objec-
ability enhancement system (FSES) cos~ $US tives.
Stowed munitions may detonate rather than burn or defla-
1-1 PURPOSE grate given a ballistic impact. The design features needed to
1-1.1 GENERAL H.JRPOSE withstand the &tonation are beyond the scope of this hand-
book.
The purpose of this handbook is to provide information
tit CIUJ be used
1-3 APPLICATION
1. By engineers to integrate fire survivability into the
This handbook applies to all combat and tactical vehicles,
des@n of combat vehicles
2. By developers of fire prevention, detection, and which include tanks, fighting vehicles, armored personnel
suppression systems to understand the operational require- carriers, reconnaissance vehicles, combat engineer vehicles,
ments and environments of combat vehicles self-propelkd artillery, ammunition supply vehicles, recov-
3. By vehicle project and product managers to obtain ery vehicles, amphibious ianding vehicles, armored cars,
an ovesview of the available technology and of fire surviv- andany other armored vehicles intended for use in the battle
ability problems area in direct or indirect contact with hostile persomel.
4. By military officem to obtain information to aid in These vehicles can be either tracked, as is the main battle
establishing fire survivability requirements for future vehi- tank (MB’I’) Ml, or wheeled, such as the light-armored
cles. vehicle (LAY) 25.

1-1.2 OBJECTIVE 1-4 OVERVIEW

The paramount objective of this handbook is to maximke 1-4.1 BACKGROUND
,J the survivability and safety of the soldiers using combat Most combat vehicles are armored to minimize the
o vehicles fiorn threa~ of fire. A secondary and complemen- equip-
effects of hostile action on the occupants and internal
@y objective is reduction of acquisition, operating, and ment. ‘I’hearmor, however, can withstand only a given level

1-1
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MII.,-HDBK-664 i
of threat. The basic fire prevention design objective is to Once the armor is perforated, the ballistic pene?rator can-
design the vehicle so that when the armor is. overwhelmed not be prevented from killing people or destroying equip-
or a slow-growth fire, which can occur in training, occurs, men~ but~la fire can be prevented, span or secondary
the occupants and internal equipment will not suffer cata- missiles CT be minimized or stopped, and the generation of
strophic darnage from fires or their effects. To accomplish irritating, ~oxious, or toxic particulate or gaseous products
this, the design and materials selected should be such that a cw be m.irpmized.
fire is not ignited by an overmatching balIistic impact or, if a If a vefilcle were made to be indestructible by fire, to
fire does star4 to extinguish it before excessive damage or destroy t$ vehicle to prevent it from falling into hostile
injury is incurred. hands in tie event of local defeat or encirclement would be
A fire-extinguishing system should be as simple as possi- almost impossible for the crew. To have vehicle destruction
ble and consistent with the requirements for speed, effec- a problem ,is the true goal of this handbook.
tiveness, and reliability. Any fire-extinguishing system for
occupied compartments should’ be automatic because the 1-4.1.1 \Review of Cornbat Vehicle Use
occupants will probably be preoccupied when the system is Combai vehicles are used to protect and carry fighting
needed. A fire-extinguishing system for the engine compart- personnel~ to a location at which those personnel can use
ment should either be automatic or have a warning system rheir wea@ns effectively against an enemy. In ancient times
to alert the driver and/or the vehicle commander when there rams used! to batter castle or city gates were armored with
is a fire in the compartment. Passive fire suppression tech- wood and ~ hides to protect warriors within from arrows,
niques should be used to the utmost to reduce the probabil- javelins, r~cks, hot oil or water, and fire. These rams were
ity of fire andlor to extinguish fires. Manual fire the ancient and medieval equivalent of our modem combat
extinguishers are needed when the automatic system is off vehicles. b World War I the coupling of the internal com-
or does not trigger or when the fire is not extinguishable by bustion e~gine with the endless track developed for farm
the automatic system. tractors produced the first effective cross-country combat
Fire extinguisher systems should not force the crew to vehicle. p early combat vehicles were armored to pro-
leave the vehicle. Shaped-charge or kinetic energy (KE) tect their ~rew from the caliber .30 rifle and machine gun
projectile hits, which usually are the cause of ballistically ball bullef~and were designed to pass through barbed wire
induced fires, are usually from direct-fire weapons or bomb- entanglements and over trenches to enable the crewmen to
lets. If the vehicle is unoccupiable, the personnel must use velicular machine guns against enemy infantry or
choose either to leave the vehicle promptly and probably be vehicular cannon against enemy weapons. These tanks still
exposed to other direct-fire weapons, such as machine guns, proved vulnerable to small arms armor-piercing bullets,
which are firing projectiles the vehicle armor could stop, or which could penetrate the armor, perforate fuel cells, and
to remain inside and be overcome by fire or noxious gases. igfite gasoline vapors, and to direct-fire, high-explosive
Personnel should be able to stay wi@in the vehicle an~ if it artillery shells (Ref. 1). From that day to this the history of
is operable, perform their duties for at least as long as is tanks and other combat vehicles is one of developing better
reqidred for the vehicle to reach cover. Further, any ground armor to resist the weapons used against the combat vehi-
fires resulting from jettisoned or drained fuel or other liquid cles and then developing better weapons to defeat the com-
combustibles should not bar personnel from operating or bat vehicle armor. Shortly before they jumped into Sicily in
evacuating the vehicle. 1943, General George Patton told the men of the 505th Air-
The design philosophy for fire-extinguishing systems borne I.nf~try, “Now I want you to remember that no
should be similar to that used by aircraft designers when sonuvabitch ever won a war by dying for his country. He
they consider armor. Fret, they design components to with- won it by ~makingthe other poor dumb sonuvabitch die for
stand ballktic impacts, then they use the shielding provided his country.” (Ref. 2). Eventually the armor will be pene-
by other aircraft components as much as possible to protect trated; therefore, the combat vehicle must be desiOmedto
more critical components, arsdfinally they use armor only as continue to protect its occupants after the armor is pene-
a last resort to protect what cannot otherwise be shielded. trated so that our troops can win any war they have to fight.
The abrogation of fire-extinguishing systems is not Because combat vehicles must carry fuel for their internal
intended. The design concept is twofold: combustion engines and carry propellants and explosives
1. Reduce the probability of ignition by selecting non- for use in their weapons, the occupants and internal compo-
combustible materials, selecting materials that do not gener- nents of t@esevehicles are highly vulnerable to fire and/or
ate strong ignition sources when hi~ or by preventing explosion when a threat penetrates the armor. The burning
formation of combustible mixtures of fuel and oxygen. or explosion of the contents of the vehicle usually kills or
2. Reduce the probability of sustained combustion by injures the crewmen and destroys the vehicle. Throughout
lowering the overall temperature of combustible materials,
reducing the oxidizer available locally, or automatically *US militq-yvehiclesare designedfor 5th percentilesize females
releasing a fire extinguishant in the threatened region. through95th percentilesize males.
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the history of combat vehicles, the solution has been to

,, improve the armoq however, designers are now seeking
,’
o ways to enhance the survivability of crew and vehicle by
reducing the probability of fire or explosion given a perfora-
tion of the armor or by reducing the vulnerability of crew
and vehicle given the ignition of fire or the initiation of
explosion.
Since the first tanks appeared in World War I, many varia-
tions of combat vehicles have been developed. There are
still tanks, but there are also armored personnel carriers.
infantry fighting vehicles, self-propelled artillery, combat
engineer vehicles, recovery vehicles. and many other spe-
ckd purpose velicles that are intended to protect the crew-
men while they are perfomning their mission or engaging an
enemy. Cornbat vehicles can be best categorized by their Figure 1-1. British Mark IV Tank Viewed
cross-country mobility and armor protection against threats From Left Rear
that would inhibit dismounted infamy or other operations
by wtprotect&I soldiers.
All British and German tanks and most American tanks
The British designed the Mark I tank in 1916 to protect
were gasoline fueled. T%e Russian tanks and some of the
infantrymen fmrn machine-gun fire and shrapnel while trav-
American M4 tanks used diesel engines, but the only reason
eling across open terrain between trench systems. These
these American tanks had diesel engines was that there were
tank had to be able to negotiate shell craters, trenches, and
not enough gasoline engines available. Also the Americans
barbed wire entanglements. These British tanks were vul-
preferred to camy more ammunition, so water jackets were
nerable to direct hits by artillery, but the machine gun and
often removed from ammunition magazines artd/or more
ma=tie rifles forced the towed artillery to move into defi-
ammunition was stowed witlin the vehicle than the water-
lade. Thus artille~ pieces were not often encountered by
jacketed magazines could hold. Fire was accepted as one of
tanks during their assault of the forward trenches. Besides,

o,, the artillery pieces were not designed to track and engage
moving targets. Against machine-=-n fire, particularly after
the Germans had introduced the 7.92-men armor-piercing
the phenomena that could happen to someone else’s tank.
The Russians used design features that improved vehicular
fire survivability more than dld the Americans, Germans, or
(AP) bullet, the British tanks were found to be vulnerable to British. These features included the use of diesel fuel and
fuel fires. These early Mark I, 11.and HI tanks had the fuel the incorporation of fixed, manually actuated water, and
cells installed within the vehicle. There was only one corn- later carbon dioxide, tire extinguishers. The Americans and
partrrtent. which contained the engin% the mobdity t%el,and British did provide hardened holders for some of the stowed
the crew. To simplify the intend hardwtut further, the ammunition in order to reduce the incidence of ammunition
engine was supplied fuel by gmvity feed. Thus the fuel cell propellant explosions given tla=gnent or span impacts. iMost
was locrmd over the engine, and when a bullet penetrated of the major powers started using steel cartridge cases, but
the armor or entered through a hole or slit, and perforated the reason was usuaIly to conserve bmss rather than to have
this fuel cell, the fuel would dribble onto the hot engine a more fragment-resistant cartridge case. In World War H
where it would usuidly ignite. ‘Ilk situation was remedied most warfare was conducted with known battlefronts with
in the desi=mof the Mark IV tank by emplacing the fuel cell enemies in somewhat fixed locations. There were a few
low, outside, and in the rear of the vehicle ttnd by armoring more fluid situations, such as in No* Africa. but usual~y
it (Ref. 1)- Note in Fig. 1-I that the steel fuel cell box is the locations of the enemy were known and armored vehi-
across the mar of the vehic!e between the tracks. After the cles could be used facing their opponents. AISOthe use of
shooting stopped in 1918, Iater tank designers forgot why small, shoulder-fired antitank grenades began to threaten
that change had been made, and the fuel cell was moved tanks from any dimccion. The Russians used Stormavi.k air-
back inside the next model tank. craft to attack tanks from above with cannon fire.
In World War II the tire survivability of combat vehicles After World War IL a Iitde more attention was given to
received much kt-ssconsideration than did mass-producing, fire survivability features for combat vehicles. Russians,
arming and armoring, and providing them the capability to and later the Americans, placed fixed fire-extinguishing sys-
move. Tlte only tire survivability feature considered in US tems in the engine compartments of their vehicles andusu-
tanks was to provide protection for stowed ammunition, ally used carbon dioxide for a fire extinguishant. The British
which consisted of metal jackets for ready ammunition in also used carbon dioxide fire-extin=mishirtg systems and
,,,’ the turret. and at the request of the British, water jackets sur- kept water jackets on their ammunition magazines; these
o
rounded the ammunition stotage on some of the M4 tanks. water jackets were not removed until the Challenger IMBT

1-3
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MIL-HDBK-684 I
was made. The Americans switched to diesel fuel primarily defeated by the larger rocket-propelled antitank missiles,
to reduce the. incidence of fires but then used the diesel fuel such as the tube-launched, optically tracked, wire-guided
to cool some engine parts. Some of this heated fuel was (TOW), or Sagger, missiles, even through their heaviest a
returned to the fuel cell and thus heated the remaining armor. The slug of a shaped charge can cause significant
fuel—sometimes above its flash point. This practice almost damage w@in a lighter combat vehicle and possibly is hot
negates the value of using diesel fuel as a less easily ieqit- enough to @ite diesel fuel spray. The shaped-charge jet can
able fuel and increases the magnitude of the hazard because pass completely through both sides of a light combat vehi-
the volumetric energy content of diesel fuel is higher than cle and eject span and molten particles into the vehicle from
that of gasoline. The Americans began to incorporate fire both the exit side of the wall initially impacted and the entry
suppression systems using Halon in their crew and engine side of the far wall. This span and splash back can be a
compartments, Similar systems have been developed and major ignition source for fuel spray and exposed propellant.
improved upon by the Israelis, British, and Germans. Stin- A shaped-charge jet passing through solid propellant will
ting with ihe T-55, the Russians have used HaIon-type tire ignite the ‘propellant and usually result in deflayation. A
extinguishers in both engine and crew compartments. The shaped-ch~ge jet passing through high explosive will usu-
Americans use. rear-mounted external fuel cells, armored ally cause ~detonation. A shaped-charge jet passing through
ag~nst sm~l -s, on some vehicles, and the Israelis have the fuel in,,a fuel cell usually will generate a high-pressure
incorporated this feature in their latest MBT, the Merkava hydraulic ~am against the fuel cell walls. When the fuel cell
III. The Americans now use a fire-retardaqt hydraulic fluid, ruptures, the fuel usually is sprayed into the adjacent com-
but this fluid can be ignited and does bum, especially in mist partment. The jet will not ignite the liquid hydrocarbon fuel
or spray form. Also it has too great a viscosity at low tem- inside the kuel cell, but the jet will &aw some of the fuel
perature to be used in gun recoil systems. The Americans behind in’ its wake in the form of a mist, which can be
have incorporated separate, vented ammunition compart- readily igriited by the span or molten splash generated by
ments (magazines), which can protect the occupants from the jet. This fuel mist usually spreads radially and will bum
ballistically initiated gun propellant. in a fireball along the trajectory of the jet. Once fuel starts to
Many of these fire survivability enh~cements have been bum, it liberates heat that vaporizes other liquid fuel, which
incorporated because of the increasing need to repair dam- then bum~. This fuel fire ignition process takes only milli-
aged vehicles rather than to depend upon receipt of new seconds. ~
vehicles—a burned out vehicle is usually irreparable-and Diesel fuel spray is slightly more difficult to ignite than is
the need to conserve trained crews. gasoline fuel spray. Gasoline vaporizes more readily than a
diesel fueI at normal ambient ~emperatures; there~ore, a
1%1.2 Review of Threats small gas~line leak is more dangerous than a small diesel
fuel leak. me vapors mix with air to form combustible mix-
1-4.1.2.1 lDirect-Fhe Threats tures, and /gasoline emits more vapors than diesel fuel at
A continuously improvin~ inventory of ~ and chemical normal operating temperatures. When heated, diesel fuel
energy (CE) weapons are designed to destroy combat vehi- can provide highly flammable vapom”.As the temperature of
cles. The armor of combat vehicles is designed to protect diesel fuel reaches its flash point, it becomes as flammable
the occupants and internal components from selected threats as gasoline. Similarly, hydraulic fluid bums readdy in spray
attacking from specific directions. When combined with or mist fo$n. Hydraulic fluid is particularly susceptible to
weight, size, and other requirements, the protection require- forming a ~pray or mist because it is used at higher pressure
ments result in combat vehicles that usually are heavily than is the mobility fuel. Such hydraulic fluid sprays are
armored in the front, less heavily armored on the sides, and almost as ~flammable as diesel fuel sprays. These include
lightly armored on the rear, top. and bottom. Since threat fire-resista$t hydraulic fluid. A noncombustible hydraulic
capabilities improve and hostile tactical scenarios change, fluid has nbt yet been used because of the high cost of such
direct-fire antitank weapons can be assumed to be capable fluid, eve~ though the noncombustible hydraulic fluid is
of defeating combat vehicle armor almost anywhere. A much less! expensive than the combat vehicle that can be
direct hit by a high-explosive artillery projectile of 100-mm lost becau’se of the combustible hydraulic fluid. Because
caliber or greater on a lightly armored combat vehicle or on ballistic impacts often result in hydrocarbon fluid sprays
the side or rear of a heavily armored vehicle will usually that are stibject to ignition without regard to specific mixt-
damage .or at least immobilize the vehicle. ure ratio, a fuel spray is generally more hazardous than a
Cumently, even small, shoulder-fired rockets, such as fuel vapor~air mixture,, which is more temperature depen-
light antitank weapons (LAWS) or rocket-propelled gre- dent for ignition.
nades (RPGs) -7 or -16, can penetrate the rears or tops of Once mobility fuel, solid propellant, or hydraulic fluid
even the most heavily armored vehicles. And in urban ter- starts to bum, it produces a great amount of heat. Items that
rain infantrymen can attack the tops of armored vehicles. would otherwise smolder or melt bum readily with the extra d
Combat vehicles lighter than first-line MBTs can usually be heat. These items include rubber, plastics, wood, and fabric.

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MIL-HDBK-684
Solid gun propdkmts also burn more readily with increased Also two aerial-dispensed incendiaries were reportedly
pressure. used by the Soviets in Afghanistan. One was a black tar-
o Some ignition soumes are present before the ballistic Jike substance (Ref. 6), dispensed from container bombs
impact disperses fuel. Hot spots, such as turbine combustor that spread the incendiary in large droplets, which ignited
housings or mrbochargers, readily ignite sprays of liquid when stepped on by pemonnel or when driven on by vehi-
fuel or hydraulic fluid Electricalshorts caused by abrasion cles. The second incendiary consisted of brown dropiets
of insulation or ballistic impact ignite materials that am (Ref. 7) dispensed by a cluster bomb and accompanied by
much less flammable than hydrocarbon fluids. With ignition small antipersonnel charges. These droplets are reputed to
soumes such as th% any action that causes a fuel spray or ignite on contact by foo~ wheel, or track These incendiary
fuelvaporin airwuallywillresultinatire. weapons are more ful~ydescribed in par. 2-3.1.3.
These incendiary weapons are threats that should be con-
14.122 Overhead and Underneath ‘Ilueats sidered in designing combat vehicles. In urban or heavily
Not even the gods could make a warrior completdy wooded temain there is the threat of the Molotov cocktai~ a
invuJnemble-AchiJles had his heel. Similarly, present-day gasoline-filled glass bottle with a burning wick which was
combat vehicle des@ners have to save weight somewhere, successfully used by the Fm agaiast Russian tanks in
so they have chosen to place Iess armor on the tops and bot- 1940. The RPO and IWO-A present the threat of an
toms of the vehicles than on the fronts and sides. The vehi- improved Molotov cocktail projected from a distance in
cle rears are also left a little weaker than the fronts and sides either urban or rural temaim The acriaklispenwd incendiar-
on the theory that tanks wiJJusually be facing the enemy. As ies present a threat on a roatL trail, or open ~ each of
Lucas PhiJJ.ips (Ref. 3) explains, however, sometimes the which can become a pool fire under a vehicle.
enemy wiJJ get behind friendly vehicJes and shoot from
there. This situation can occur in meeting engagements and 1-4.13 Review of Suwivability Enhancement
where the enemy has infiltrated into our rear areas. This
Techniques
technique is favored by the former Soviets (Ref. 4) and Chi-
Most designers, when faced with the need to counter a
nese and was used against US forces in Vlemam. But the
fire, install a fire extinguisher in the vehicJe, but &es are
tops and bottoms of combat vehicles rwnain their weakest
parts. di-f%ctdtto start and maintain when they are wanted and m
To altack the top surfaces of combat vehicleq two basic diflicult to extinguish when they are not wanted. AJso fires
o approaches have been followed The first is to use cluster can destroy both personnel and equipment even when
warheads with many small shaped-charge bomblets rhat fall promptly extinguished. For these reasons, preventing tires is
upon the vehicle or a shaped-charge warhead missile attack preferable to extinguishing them. Fii extinguisher systems
fmrn above. A variation of this approach is to use explo- should not be eliminated. There wiJJalways be instances in
sively formed penetrators instead of shaped-charge jets. The which fires cannot be precluded. Fw extin=@sher systems,
second approach is to have a rapid-fue cannon mounted on however, should not be the only, or even the primary, pro-
an aimraft Jire an armor-pieming projectile from above. In tection against fires.
World War L1 armor-piercing bullets were use4 more T& simplest way to prevent a fire is to dekte one of the
recmuly, Iong rod penetrwors of a h- dense material have three eJemenB needed for combustion to occur, lle three
been used Therefo% the vehicles have to be designed so eiements are (1) a fuel in a combustible stateA(2) sufficient
that both KE penetrmors and CE (shaptxkharge) wmheads oxidizer in intimate contact with the fu4 and (3) an ignition
are considered soume in contact with both fuel and oxidizer that can raise
To attack the bottom surface, the principal fire threat is a the tempemmes of the two to their kindling state. Thus a
shaped-charge-type land mine. The shaped charge could fire can be prevented by removing the fuel+asmring that the
either form a jet or launch a flyer plate. The mine could be fuel is not in a combustible state or foa reducing the
fuzed with a tilt rod or a magnetic proximity device. amount of oxidizer presen~ or ehinating or reducing the
probability of ignition sources. AJJof these am described in
1-4.L23 Incendiary Threats this handbook. Control of these elements is also used to
h addition to the CE and I(E penetration weapons and extinguish fires. FH aIE extinguished (1) by placing a bar-
antitank mines that are currently tielde4 the former Soviet rier beween the M and oxidizer, e.g., light water foam, (2)
forces reportedly used several incendiary weapons in by diluting the oxygen until there is not enough present to
Mghanistan that could pose a significant threat to our com- support combustion, e.g., diluting the air with carbon diox-
bat vehicles. These are the family of mcket-propel.led infiM- idei (3) by cooling the fuel and surrounding objects below
try Jkunethrowers, i.e., the rocket-propelled flamethrower their kindling temperatures, e.g., by cooling with water, (4)
(IWO) and rocke@ropeJJed flamethrower-airbome (RPO- through chemical inhibition of the combustion proces.%e.~,
,’ :
o A). (R&. 5 and 6) T&se wwqxms am similar to the 3.5-in. with HaJons or potassium bicarbonate, or (5) by a combm-
rocket Jauncher. tion of these techniques.

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IWL-HDBK-684
Flammable fluids, in fact, almost all combustible materi- compartment. A fixed fire extinguisher system in one com-
als, bum only in the gaseous state and then only within a partment, however, cannot affect a fire in another compart-
rather narrow range of fuel-vapor-to-air mixture ratios. A ment, and some extinguisher systems must direct the
fuel-vapor-to-air mixture can be too fuel rich or too fuel extinguisljant at the fire to be effective. Also use of gaseous
lean to burn. Designers should not depend upon maintaining extinguisl#ants, such as many I-Ialons or carbon dioxide,
a mixture that is too fuel rich because as that mixture makes the:effect time dependent since hot spots will not be
spreads away from the fuel source, more air is available to cooled an~ the gaseous extinguishant will be diluted by air-
assure that somewhere the mixture will be combustible. flow through the compartment with passage of time. This
Once a fire starts, the heat increases fuel vaporization, and dilution makes the compartments thereby protected subject
air convection makes more of the mixture combustible. The to reignition after more ak has mixed with the atmosphere
more volatile the fuel, the more probable the presence of a of the compartment.
combustible mixture. Gasoline is more hazardous th~ die- Solid rocket propellants and to a lesser degree high
sel fuel because it is in vapor form at normal operating tem- explosives contain most of the oxidizer as well as the fuel
peratures. When diesel fuel is heated, however, it win needed for combustion. Solid gun propellants bum more
become aImost as volatile as gasoline. This is the reason it is rapidly when pressurized, and a cartridge case prevents the
poor policy to use diesel fuel as “m injector coolant unless rapid dispersion of products and results in pressure buildup.
the fuel is injected into the engine and burned immediately For these \lreasons, solid propellant or explosive fires are
after it is heated. Recirculating heated diesel fuel to the fuel more difficult to preclude than are liquid fuel fires. Solid
cell increases the fire hazard. rocket propellants are usually closer to a stoichlometric oxi-
The energy required to ignite a combustible fuel-vapor- dizer-to-fuel mixture than are high explosives; therefore,
air mixture is one-tenth of a millijoules,which is a miniscule they are more susceptible to reacting violently given a bal-
amount of energy.
,. Mists or sprays of flammable liquids in listic imp~ct. Once ignited, solid rocket propellants can be
air can be igmted below the lean limit and above the rich extinguisd~ only by being cooled below the kindling tem-
limit of the fuel-vapor-air mixtures given somewhat more perature, preferably with a water deluge. When these pro-
ignition energy than that required to ignite the vapor-air pellants ~e cased, either with a metallic or combustible
mixture but much less than the energy available in a ballis- case, or are in a solid mass as are caseless charges, the cool-
tic impact. Thus mists or sprays in air present a greater haz- ant canno~ reach the propellant in time to prevent chemical
ard than does a vapor-air mixture. Prevention of the release reaction. Gooling of gun propellant has proved feasible only
of mists or sprays can eliminate the most hazardous of the with exposed propellant grains. This is fine for ammunition
fuel forms. Diesel fuel mists or sprays normally occur when loading plants but does not help in combat vehicles unless a
the fuel cell is pressurized locally by hydraulic ram result- device is used to inject the liquid through the cartridge case.
ing from”ballistic impact and when the spray is released Methods fir enhancing crew and vehicle survivability given
from failures in the fuel cell. These failures can be signifi- solid propellant or high-explosive initiation due to ballistic
cantly reduced through fuel cell design, fuel cell material impact us@Iy focus on containment and redirection of the
selection, ardor fuel cell confinement or reinforcement. explosion effects away from critical areas of the vehicle.
The release of fuel sprays in critical locations can also be By criti&l examination of the combustion phenomena for
significantly reduced by proper fuel cell location or by com- each combustible and of the failure modes of the equipment,
partmentation. Because antitank gunners normally aim at the equipment can be modified either to preclude fire or
the center of the presented area of the target, the probability explosion or to assure that the fire or explosion effects will
of a fuel cell impact can be reduced by locating the fuel cell be directed away from the crew and critical components of
as far from the normal aim point as possible. Fuel cells can the vehicle.
be located either low in.the vehicle or in the rear. The proba-
bility of diesel fuel spray from a fuel line can be reduced by 1-4.2 DESIGN PHILOSOPHY
lowering the pressure in the fuel line. If atmospheric pres-
sure is used to force the fuel to flow, there is a much smaller 1-4.2.1 Basic Combat Vehicle Design Philosophy
probability of a fuel spray given fuel line puncture by a bal- History has shown that every armor system fielded has
listic impact. Hydraulic fluid lines, on the other hand, are been folloked by the fielding of an antiarmor system capa-
usually more highly pressurized than fuel lines, and they are ble of overcoming the armor, which has in turn been fol-
located throughout the vehicle. Therefore, the hydraulic lowed by \he fielding of a newer armor system capable of
power system of a vehicle can be more hazardous than a withstanding the new antiarmor system, and that design,
properly designed fuel system unless a truly nonflammable development, manufacture, and fielding of the newer armor
hydraulic fluid is used. Electric drives can be used to elimi- system have taken twice as much time as they did for the
nate the hydraulic fluid. Alternatively, a fire extinguisher or newer anti~or system (Ref. 8). Therefore, sooner or later
inerting system can be used to extinguish combustion or armor will ~;beovercome by some threat. The combat vehicle
reduce the probability of a hydrocarbon fuel fire in a given should be constructed so that when the armor is defeated,

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the crew will not be burned and the vehicle will not be dam- 1. Already issued to troops

o
I,, aged beyond recovery by fire.

is
In designing a combat vehicle, the priority for protection
2. currently being produced
3. To be designed for future use.
Where combat vehicles are cumently vulnerable to fire,
~. P~Md these vehicles should be modified and the fire sumivabiity
2. The vehicle concepts must be designed for economic incorporation. Fu
3. Equipment within the vehicle sumivability concepts for retrofit on existing vehicles may
4. Material stowed within the vehicle. not be as fully effective, as economical as lighL or use as
The approach used in designing a combat vehicle should small a volume as a complete vehicle redesign would pro-
be to use passive&e protection techniques to vide, but these design modifications can provide significant
1. Eliminate, reduce, or confine combustible materi- survivability enhancement. When incmporating modifica-
als. tions into existing vehicles, maintenance personnel can
2. Reduce the probability of ignition of these combus- more easily replace specific components, such as an existing
tible materials. single-walled fuel cell with a double-walled fuel cell, which
3. Reduce the probability of having sustained combust- wdl fit into the same space, or install an added componen~
ion of these materials. such as a reinforcing wall over an exposed pornon of a fuel
4. Reduce the generation or liberation of toxi~ nox- cell, than tear out the internal components and rebuild Rlo-
io~ or irritating products that would drive persomel out of cat% and replace all or most of these. This also means mod-
the vehicle. ifications that can be performed at the organizational or
5. provide some means for the crew to extinguish direct support level of maintenance are preferable to those
whatever combustion does occur. that require depot or fabricator rework. Field teams from the
Specific techniques that can be used are to depots or fnbncator should be sent to advise the organiza-
1. Locate hazardous items so that if they burn or tional or direct support maintenance personnel to assure
explode, the personnel will not be killed or injured and the proper modification.
vehicle will not be destroyed. If possible, render these items Modifications that can be incorporated during production
nonhazardous by preventing severe reactions, e.g., by pro- should be planned in order to minimize dismption in the

0,,
viding an extinguishant which will be released by the same production schedule. Again, these modifications may not be
tbmat that caused the teaction. as effective as those incorporated in a completely new
2. Assure that a damaged combat vehicle provides design, but they will be better than no design modification
protection for its occupants. The vehicle must remain habit- and should be more effective andless expensive than modi-
abie an~ if possible operable after being hiL which fications that would be made after the vehicle is completed-
includfs preventing the entrance of flare% fire. and noxious When incorporating fire survivability concepts into
products into the occupied compatlrnents. designs of future vehicles, the designers have more freedom
3. Realize that ifa combat vehicle is hit on% it is sub- to select materials, locations, and,techniques than they do
ject to being 4it more times, particularly if the vehicle can when modifying existing vehicles or changing designs
no longer move; therefo% care must be taken to design the already in production. me same goals can be achieved
vehicle so that the early hits do not render the vehicle more using different means. Some hamrds can be precluded by
susceptible to potential 6res by subsequent hits. more reasonable material selection or component location.
In general, however, a sirqgie, optimum design will not be
142.2 Incorporation of Fiiw Survivability Con- achieved since there are design tradeoffs and continued
cepts changes in threats, required contents, and operational
General George S. Patton, Jr., has been quoted as saying, requirements that wilI make today’s defense tomomow’s
‘There is only O-Mtactical @ncipIe, which is not subject to hazard. Some thought should be given to providing designs
change. It is to use the means at hand to inflict the maximum that can accommodate the future modifications which will
amount of wounds, death and destruction on the enemy in undoubtedly become necessary.
the minimum amount of time.” (Ref. 9). The job of vehicle Note that when &e survivability enhancements are incor-
designers, program managers, equipment manufacturers, porated early in the design and development of a combat
and ptanners is to make certain that US troops have at had vehicle, better protection is provided at a lower cost witi
now and in rhe future, the most fire survivable and effective similar weight and volume penalties. For example, it costs
combat vehicles in order for them to wound kill, and more money to provide less protection on older and current
destroy the enemy. combat vehicles than to ales@ fi.tture systems that include
There are basicalIy three times during the life of rnilitmy these enhancements. k general, the current designs will be

0 equipment when &e survivability enhancement &vices can

be incorporated into combat vehicles. These three times are
when the vehicl= are
used by troops now and for several years. The future
designs will be used for combat vehicles sometime in the
future and for many years after hey are issued to troops.

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i
IWL-HDBK-684 “
1-5 COST ANALYSIS ‘! SE= 1 – P~F, dimensionless. (1-1)
Inevitably, when a modification to a combat vehicle is
proposed, the iirst question asked is what is the cost, or what For P~~ Hackenbruch ev~uat,ed tie combat loss data
am I buying for the cost? There is no existing computer from SEA kor fiscaJ year (FY) 1969 to obtain the probability
model that can be used to predict this cost or to establish of a sustai~ed fire resulting when an internal fuel celI is used
whether the modification will be cost-effective. Documents P ~~l~cfor~the M113 FoV. He assumed that P~~ equaled the
that could assist in the preparation of such a computer number of incidents of sustained fires causing complete
model are the cost and effectiveness analyses of modifica- losses div~~ed by the total number of vehicles hit. He then
tions to the M 113 family of vehicles (FoV) and the M60
estimated how many vehicles would not have been lost if
MBT by Douglas Hackenbruch (Ref. 10 and 11), the cost
these vehicles had had external fuel cells to obtain the prob-
comparison of nine alternate fire-extinguishing systems for
ability of a sustained tire resulting when an external fiei cell
the l%eld Artillery Ammunition Support Vehicle (F&%5V)
by John Karas (Ref. 12), and a means to estimate the life is used P ~F~~cby deleting the number of vehicles that had
cycle costs of incorporating survivability en@ncement con- fires start horn hits on the fuel cell from the sustained fire
cepts for fuel systems in aircraft (Ref. 13) in an unpub~shed subtotal.
report by P. H. Zabel and N. W. Blaylock. The cost-effectiveness ratio CER was determined for the
Ml 13 FoV;,by dividing the SE by the vehicle cost VC or
1-5.1 COST-EFFECTIVENESS STUDIES CON-
DUCTED AT ‘THE US ARMY TANK- CER = SEAW, $US-l . (1-2)
mrohiomm RESEUCH AND The ve~lcle cost used was the cost to acquire the vehicle.
DEVELOPMENT COMMAND (TARAD-
~~ This CER was determined for the vehicle as manufacture~
COM) ~OW US ARMY T~K-AUTO- i.e., with @ internal fuel cell, and for the vehicle with exter-
lkfOTIVE CO MlW4.ND (TACOM)] nal fuel eel/s. The incremental cost of the external fuel cells
The cost-effectiveness of fire survivability enhancement was estimated by Government persomel.
systems (FSES) was evaluated for two different vehicles. The CE1/ with the FSES was compared to the CER with-
The use of external fiel cells was evaluated for the M113 out the F~ES to determine whether the FSES was cost-
FoV (Ref. 10), and the use of automatic fire detection and effective. These CERS and their constituent SES and VCS 9
suppression equipment (AFDSE). was evaluated for the were then ~ompared to establish the break-even cost of the
M60 MBT (Ref. 11). The basic evaluation ,technique was FSES and Ijalternatively the break-even cost of repairing
damaged v~~cles.
the same in both cases, but the methods used to calculate the
system effectiveness SE differed. In both cases combat
1-5.1.2 kFDSE for M60 Series MBT
damage dam from Southeast Asia (SEA) were considered,
and for the M60. MB’I’data from the Yom &ppur War were Regar~g evaluating the cost-effectiveness of incorpo-
reviewed. In both cases, the Dehn fuel fire model (Ref. 14) rating ~SE into the M60 series MBT, the difference in
was used to establish the probability a sustained fire could the evaluation was the ‘method used to establish the system
exist this model description was supplemented by Wright effectiveness. The SEA data available were for the M48A3
and Slack (Ref. 15). MBT and the Yom Kippur War data for M60 MBTs. These
data were ~ot sufficiently detailed to permit assumption of
1-5.1.1 Exkmal Fuel Cell for M113 FoV the Valkiitylof J.@ 1-1; therefore, the expression recognized
by the Dep@nent of Defense (DoD) for SE was used. This
In the analysis of the Ml 13 FoV, the use of external fuel
SEis ~
cells was deemed 100% effective preventing a sustained
diesel fuel fire within an Ml 13-type vehicle. This followed ] SE= A-l?” C, dimensionless
$,
,(1-3)’
the Dehn fuel fire model, which states that four consecutive where
events must occur for a sustained fuel fire to develop. These A +, availability, i.e., probability that the vehicle is
four events are (1) a fhel spray must form, (2) the spray : in a ready state at a random point in time, or
must be ignited, (3) the ignited spray must i=tite a fuel pool, ~operational readiness, dimensionless
and (4) the extinguishing system must fail. Hackenbruch R =1 reliability, i.e., conditional probability that the
assumed that with external fuel cells the probability of a i vehicle can complete a defined mission under
fuel spray forming and the probability of a fuel pool form- , specific conditions, or dependability, dimen-
~
ing inside an armored personnel carrier (APC) were near IIsiordess
zero. As a corollary, the system effectiveness of the FSES C =’:capability, i.e., a measure of the ability of the
was assumed to be equal to the complement of the probabil- , vehicle to achieve its mission performance 9
ity of having a sustained fire P$~ or objectives, or design adequacy, dimensionless.
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Hackenbruch (Ref. 11) determined A, R. and C for the vehi- These fire extinguisher systems were not assumed effective
,, cle, with and without the AFDSE, by using a combination of against explosion of ammunition.
0 the available combat damage data and vulnerability assess- A combat analysis was performed to generate the cumu-
ments provided by TACOME3. TACOME3 (Ref. 16) is a lative probability of survival and cumulative expected loss
computer model with which the probability of kdl of a comb- (CEL) for each alternative by round. The methodology used
at vehicle can be computed given shotlines of either KE or to compare the alternatives was CEL after the vehicle was
CE projectiles through the armor and then internal compon- hit by one, two, and three penetrating munitions. For two or
ents. Using TACOME3 techniques and inputs, Hacken- more hits redundancy of extinguisher systems either in
bruch computed values of SE for the vehicle with and added bottles or in discriminating sensors redwed the CEL.
without AFDSE Using these values of SE and costs of the A break-even analysis and an incremental analysis were
vehicle and AFDSE. which were determined in the same performed to examine systems, cosq survivability, and
manner as those for the M113 FoV anditsFSES,he calcu- expected loss.
lated the CERS and analyzed cost-effectiveness, break-even
AFDSE cost. and break-even vehicle repair cost in the same 1-53 METHODOLOGY TO ESTIMATE LIFE
manner described for the M113. CYCLE COSTS OFA.IRCRAIW FUEL
SYSTEM SURVIVABILITY ENHAIICE-
1-S2 COST ANALYSIS FOR FAASV PRE-
MENT CONCEPT’S
PARED BY TACOM
Zabel and Blaylock (Ref. 13) prepared a methodology to
Nine 6re-extin.@shing system alternatives for the M992
estimate life cycle costs of incorporating and using several
FAASV were compared for combat effectiveness and cost-
ahernative stuvivability enhancement devices for airmail
effectivertess for protecting against fires ignited by shaped-
fuel systems. The items treated were the overall system and
charge warhead perforations (Ref. 12). A shotline genera-
specific subsystems, such as self-sealing fuel cells, tdlage
tion program was run that passed an array of shotlines
filler materials (reticulated foam, fiber mats, and metal
through each one-inch square of the area presented by the
vehicle and recorded the incidents on ammunition, diesel mesh), ~oid space fillers. powder packs, fire-extin=g.tishing
fltel, and hydraulic fluid. This shotlhe generation program systems, on-board nitrogen generators, and some other
was repeated for borizonml and vertical aspects 30 deg devices. The costs included both those normally contracted
apart. These shotlines were assumed to be hits by shaped- and those incuxwi in a Government depot. The life cycle
o charge. warheads that would overwhelm the vehicle armor. costs included the cost of engineering plans for incorporat-
The assumption was made that a hit on any ammunition ing the modifications, the cost of the hardware to be added
would result in an explosion which would cause the loss of including the cost of qualification testing if necesszuy, the
the vehicie and its contents. Hits on diesel fuel or hydraulic costs of disassembling existing aircraft as necessary and
fluid czmtainers would result in vehicle loss due to a sus- reassembling the aircmft as modified or the additional costs
tained fire unless these were protected by some 6re-extin- of using these new devices over the existing hardware if the
.@shing system in the same compartment as the container. aircmft had not yet been assemblec4 and the additional costs
The assumed efktiveness of each fire-extinguishing sys- to operat% maintain, and suppott these devices through the
tem considered is given in Table 1-1. The cost associated opemtional life of the aircraft inchdng additional units
with a hit is rhe vehicle cost times the probability of an needed for potential battle damage repair.
explosion or a sustained fire. The probability of a sustained The cost elements were based upon combhntiorts of esti-
fire is the complement of the probable effectiveness of the mates by suppliers or fabricators of the materiai% comp
fire extinguisher to extin=tish a fire listed in Table 1-1. nents and subsystems and of costs redzed by some prime

TABLE 1-1. ESTIMATED EXTINGIJISEER SYSTEM EFFECTIVENESS (Ref. 12)

EX~GUISHER TYPE* I EFFECTNENESW*, %
Portable 1
Fwed fm extin=tisher system (FFES), manual activation, no 30
automatic warning system
FFES, manual activation with automatic warning system so
Dry chemical passive panel I 90
Automatic fwe extintzuistter system using HaIon 1301 99
,,,
0 *Deployedin either crew or enginecompattrnent
**M=tjVm= ~ma~ 10extinguish a fire in a givencompattrnentbasedupon discussionswirh personnelfrom HUITVUI
Laknatoxy and dte Systemshqmtion Branchof LightCombatVehicJeProgmmManager’sOffice
Engintig

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p
MIL-HDBK-684
contractors and Government agencies or depots in obtaining component. In estimating unit costs the effects of procure-
components for original assembly or replacement items ment quantity, unit complexity, and fabrication and assem-
needed for maintenance operations. Component costs were bly “learning” were factored into the estimates.
obtained from records of Government purchases for stock- Estimations of the effectiveness of these survivability
age of repair parts and tracked from 1970 to 1981; these enhancem~nt concepts were beyond the scope of the cost
costs were found normally to escalate with the consumer estimator }ffort; however, Zabel et al. (Ref. 17) developed
price index (CPI). These components were made by origi- effectiveness factors for many of these items based upon
nally qualified vendors of the products who became “locked test results.
in” for future procurements. Another example is shown as
Fig. 1-2 in which a combination of Government-owned 1-6 CONTENT OF HANDBOOK
drawings and specifications plus a generic qualification and This handbook covers the types of combat vehicle fires,
procurement competition resuited in a decrease in price how these fires are initiated, what flammable materials are
over the same time period. For the initial procurement the present, and what hazards the fires present to the crew and
relative cost was 2 and the CPI approximately 1.3. The data their vehicle.
were furnished by a prime conbctor for the same type of The combustible materials present are described in detail
with emphasis on the properties that enhance or degrade
ignitability and fire sustainability or create special hazards.
The combustible materials include fuels; hydraulic fluids;
1- other mobility fuels, oils, and lubricants; munitions; and
other combustibles, such as electrical wiring insulation, rub-
ber and plastics, seat covers and cushions, paints and coat-
ings, and ~tems used or stowed in or on the vehicle. me
clothing w’omby the crew is not considered as either protec-
tion or as a combustible; however, spare clothing and bed-
ding stow~d by the crew within or on the vehicle are treated
as combustibles.
Fire pre~ention that can be gained by engine selection or
engine de~ign features is discussed. Fuel, hydraulic, and
electrical system design features that affect fire prevention
are described and discussed. Munitions types and stowage
features t~at affect fire prevention are covered. General
guidance oh material selection for fire reduction is provided.
System design features that enhance fire prevention or
inhibit fire propagation are covered.
Crew survival criteria are covered and include the types
and extents of thermal injury and ear, lung, and eye injury.
The potential for asphyxiation or toxic gas poisoning is dis-
cussed. Tlie potential effects on human performance from
1 KitManufacturer these types of injuries are discussed.
Fire detection systems and their components are
described and their characteristics given.
Fire-extinguishing agents and systems are described and
discussed. Both active and passive systems are covered, as
are manual fire extinguishers.
Techniques used to test and evaluate design verification
are described and discussed. Means of measuring perfor-
-.. mance parameters that can be tested are described. The
0 5 10 techniques used to model crew incapacitation, equipment
Time, y damage, z$d tire initiation, growth, extinguishment, and
prevention~as functions of ballistic impacts or other ignition
I?@re 1-2. Reduction in Reticulated Foam Kit causes are described. Existing computer models are
Cost Resulting From SimpMication and (hn- described. ~f these are lacking, the elements needed for such
petition (Ref. Xl) models are!given.

1-10
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REFERENCES 14. J. H. Dehn, A Fuel Fire Model for Combat Vehicles,

o 1. B. Cooper, ?7zeBattle of Cambrai, Stein and Day Pub-

lishers, New York NY, 1968.
BRL Memorandum Report No. ARBRL-MR-0289Z
US Army Ballistic Research Laboratory, Aberdeen
proving Groun& ~, January i979.
2 C. Blair, Ridgeway k Parasrvopers, The American Air-
15. W. P. Wright and W. A. Slack An Anaiysis of Diesel
&ome in World War H, The DM Press, Double&y dk
Fuel Fire Tesr Data for theM113A1 APC Subject to
Company, Inc., Garden City. NY, 1985.
Shaped-Charge Munition Attack. BRL Memorandum
3. C. E Lucas Phillips Afamein, Little, Brown and Com- Report ARBRL-MR-03054, US Army Ballistic
~y, Boston, MA, 1962 Research Labomtory, Aberdeen Proving Groum$ MD,
4. D. C. Isby, Weapons and Tactics of the Soviet Army, August 1980.
FulIy Revised Edition, Jane’s Publishing company, 16. J. J. Piechock.i, G. Ialongo, R. A. Dees, artd J. B. ReiA
LtcL hXldOI& m 1988. Analytical Procedwes for Vulnerability Computations
5. ‘lZPO-A Flamethrower Artillery for the Soviet Sol- of Combat Vehicles Agaittst AP and HEAT Projectiles,
dier”, Jane k Defmce Weekly, 934-5 (24 May 1986). Supplement 1, TACOME3 Operator’s Man@ Tkchni-
6. “Soviets Use Afghanistan to Test ‘Liquid Fw’”, Jane 3 cal Report No. 12071, US Amy Tank-Automotive
Defence Weekly, 819 (26 May 1984). CommanrL Warmm,MI, June 1975.
7. Yo.sszf Bodartsky, “New Weapons in Afghanistan”, 17. P. H. Zabel, V. B. Parr, M. G. Whimey, and L. M. Var-
Janek Defence Weekty, 412 (9 March 1985). gas, Parked Aitwa~ Vtdnerability/Sumivability Assess-
8. Personal conversations between P. I-i. Zabel and M. J. ment Proce&n?, ASD Technical Report ASD-TR-80-
Clauson, US Amy Tank-Automotive CommantL War- 5051, Air Force Systems Command Aeronautical Sys-
rem MI, 19 February 1992. tems Dh&on, Wrigln-Pattmon Air Force Base, ON
November 1980.
9. G. S. Patton, Jr., WU as 1 Knew It, Houghton Mifflin
Company, Boston, MA, 1947.
BIBLIOGRAPHY
10. D. J. Hackenbruch, Cost-Effectiveness of Ektemal FueI
Tti for M113 Family of Vehicles, TARA.DCOM Atmored Vehicle (M113) Vulnerability w Diesel Fire, NMTl
Report No. 79-04, US Amy ‘l?%k-Automotive TERA Group Report TD-78- 1260-U, New Mexico Tech-
Research and Development Command Warren, Ml. nical Univemiv, Terminal Effecrs Research Activity,
0 Socomo, NM, 22 June 1978.
June 1979.
11. D. J. Haclmnbruch. Cosr-Eflecriveness of Automatic H. Guderian, Panzer Leader, Michael Joseph, Ltd., Londom
Fire-Extinguishing System on the M60 Series Combat w 1952.
Vehicles, TAIWDCOM Repott No. 79-04A, US Asmy S. J. McCormicL P. F. Motzenbecker, and M. J. ClausoG
Tank-Automotive Research and Development Com- Passive Fuel T& Inehg Systems for Ground Cornbar
rnana Wamen, MI, October 1979. Vehicles, Tdmktal Report 13385, US Army Tank-Auto-
12 J. - Comparison of Alternate Fire-Extinguishing motive Command+ Warren, MI, September 1988.
Systems for the M992 Field Am-ile?y Ammunision Sup- F. W. von Mellenthiz Panzer Battles, Ballenti@ New
port Vehicle (FUSV), TACOM Report No. V-85-14, Yo& NY, 1956.
US Army Tank-Automotive CommanA Warm+ ML L. Olson, Mauser Bolt Rij?.es, F. Brownell and Son, Publish-
February 1987. ers, Inc., Montezuma+ IA, 1976.
13. P. H. Zabel and N. W. Blaylock Cosr-&timating Rela- W. P. Wright and W. A. Slach Diesel Fuel Fire Test Data
tionships for CO* Survivability Enhancement! Con- and Model for Armored Vehicles, Report ARBRL-MR-
cepts for Aircrafi Fuel T&, Southwest Research 03004, US Army Ballistic Research Labomtory,
Institute project Report 02-6288-001, prepared for Aberdeen Proving Grow& MD, March 1980.
Naval Weapons center, China Lake, CA I.htpublishea
4 May 1982.

0 ,!, .

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.:;
O CHAPTER 2
CATEGORIZATION OF FIRES
This chapter iderutjies broad categon’es ofjires th.a occur in combtu vehicles. Fire types are &@ed and grouped on the
basis of propagation rate. The rype of combustible mmerial, ignition source, jire Iocm”on, and other details chtu a~ect the
growrh rare offires and hence zhe swvivabiiiry of combat vehicles are discussed

2-Q LIST OF SYMBOLS persed and forms sheahs followed by ligaments. which
Ddd= t%ddroplet diameter, pm bemuse of surface tension forces, breakup into droplets. A
D,,~ = sphere diameter, mm ballistic impact through a liquid fuel or mpture of a high-
E= = apparent activation energy, kcal/mole -pressurehydraulic fluid line can result in a spray.
Tin = temperature of sphere that results in fluid ignition, K 5. Dust. A mist-like suspension in which the materiai
J3 = fuel droplet evaporation factor, pm2/ms is in the soiid state rather than liquid.
‘z = fuel droplet evaporation time, ms The means of initiation of fires include munition initia-
tion, electrical disch~e, hot surfaces, and exothennic reac-
2-1 INTRODUCTION tions. The jet from a shaped chargge can initiate gun
Fms in combat vehicles can be categorized by rate of propellants directly or can disperse liquid hydrocarbon fuel
growth. by means of initiation, by fuel types, and by bca- in the form of vapors and spray and can project ttigh-tem-
tion. The rate of growth of a fire can vary from a deflagra- perature particles of ahtminum or steel, which can ignite the
tion, i.e., a low order explosion occurring in milliseconds, to hydrocarbon fuel. High-velocity, kinetic energy (ICE) pro-
a smolder, e.g., the burning of coals. Normally the rate of jectiles can do the same. Armor-piercing incendiary or
growth of a &e varies as different combustible materials are tracer projectiles can introduce a burning matentd into an

,:,
o,: reached or releawl as the heat generated builds up, or as
the quantity of oxidizer present changes. The state or form
of the combustible material. or fuel, also affeets the rate of
internal, vehicular compruzrnent as well as disperse fuel.
Armor-piercing, high-explosive incendiary projectiles caa
introduce a &tonating warhead into a Iightly atmomd vehi-
growth. Thus the potential rate of growth of a fire can influ- cle. Thus there are many means by which to disperse fuel in
ence the sekction of the fire suppression system. For examp- flammable forms and provide many ignition sources from
le, an automatic system would be needed to suppress a threat munitions. Electrical discharges can occur where
deflagration. inst.dation is destroyed through abmsion during normal
The definitions that follow are usefitl in considering the vehicle opemtion or is ruptured and removed by munition
state or form of combustibles: effects. UnIess the electrical circuit is broken, the electrical
1. Vapor. Any substance in the gaseous state; thought ddarge can continue for a considerable time. f-lotsurfaces
of with some reference to the liquid or solid state. Vapor is can ignite hydrocarbon fiuids that are sprayed thereon- If the
molecular m size and usually formed by heating a liquid so temperature of the hot surface is high enough, heavy hy~
that mokcuies leave the liquid bulk. carbon fiuids can be cracked to produce more easily ignite~
2. Fog. Vapor condensed into fine droplets large lighter fluids, Exorherrnic teactions can provide heat to melt
enough to scatter light and to obscure vision. The droplets in and boil and then ignite combustibles. Exothetmic reactions
a fog range in size from 025 to 1.0 pm and remain sus- include the spontaneous combustion of oily rags, a smol&r-
pended in air by the effects of Brownian motion. ing cigarette butq and a slow-burning fire, which by itself
3. Mi.m Liquid droplets .-r in size than 1.0 ~ might not be dangerous. High-tempemure exothermic reac-
and extending up to about 5 pm in dhmeter. For droplets in tions, such as burning metals, can convert extinguishants
this size range, the gravitational fotce is relatively small into fuels and oxidizers. The means of initiation of a fire is
compared to tbe viscous draft force. These droplets are not an important consideration in sekxting tie &tails of the
permanently airborne by Brownian motiow they will even- extinguishant and fire suppression system.
tually settle unless buoyed up by gas convection or circtda- All combustible materials are considered to be types of
tion. Sloshing of fiel in a cdl can cause a mist to form in fuei. These fiels include hydrocarbon fluids, gun pmpel-
the @lage of the fuel cell. Ian& high explosives, elecrnc wire insulation. pain~ plas-

,,
0
4. Spray. A distribution of droplet sizes generally
greata than 5.0 pm in diameter. In the area of combustion,
SPraYS~ produced by shear foxes acting on a liquid fuel
tics, rubber, seat covers, axe handles, maps, clothing,
magnesiutnhlurnimun alloy road wheels, and lithium bat-
tery plates. The fuel type is a determinant for the extinguis-
jet thas isnpinges on the surrounding air. The liquid is dis- hant to be used as well as the type of fire suppression

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MIL-I+DBK-684
system. In addition to fuels oxidizers also should be consid- gory of fire is defined and described in the paragraphs that
ered. For example, armored maintenance or recovery vehi- follow. These definitions include both fast-growth and slow-
cles, or armored personnel carriers used for medical growth fires fid describe the fuel involved and probable
evacuation, may be required to carry bottled oxygen. mode of igniti~n.
Release of the oxygen could increase the probability of igni- Fires are t$e observable effects that result from rapid
tion and contribute to the severity of a fire in this type of chemical reactions between an oxidizing medium (such as
vehicle. air) and oxi$lzable (combustible) materials. Combustion
Fires can occur within, on, or below combat vehicles. reactions are accompanied by the release of heat, light, and
Potential fire locations are important in positioning fire sup- oxidation products. The rapidity at which ties burn var-
pression systems and in designing other survivability ies—they can be slow smoldering; they can have a gradual
enhancement features. Most current combat vehicles have flame spread; $ they can be an explosion, a nearly instanta-
separate engine and personnel compartments. Munitions are neous total involvement of exposed materials. Explosions
often carried within personnej compartments for accessibil- vary in rate of reaction from a deflagration to a detonation.
ity. Some combat vehicles, however, have separate compart- A deflagration, i.e., a reaction occurring in milliseconds, is a
ments for the stowage of munitions and other hazardous rapid fire, whereas a detonation, i.e., a reaction occurring in
items. Fuel can be canied in cells located within vehicles, microseconds is a chemical reaction that is not categorized
either in the engine compartment or the crew compartment, as a fire. The’ products of these two reactions differ. Nor-
or in external cells. An individual fire-extinguishing system mally in a fire the products are more thoroughly oxidized
is normally effective only for a single compartment. than they are ~ a detonation.
The ignition and propagation of fires require the simulta-
2-2 DEFINITION OF FIRES neous presen~e of three key ingredients, fuel, oxidizer, and
Fire is a chemical reaction that involves the rapid oxida- heat. Heat en$rgy is required to achieve ignition and to sus-
tion of a combustible material. Combustion is an exother- tain combusd~n. Initially, it must be provided by an external
mic process: Heat is liberated. A combustible material source and f$ sustained combustion is supplied or supple-
ignites ,’whenan ignition source raises ,its temperature above mented by energy released by combustion reactions. The
its kindling point for a time in excess of the ignition delay oxidizer may be atmospheric oxygen or it may be an oxitlz-
period. This chemical reaction occurs at the junction of the ing substance!present in, or derived from, materials comain-
combustible material and the oxidizer. For most solid or liq- ing fuel-oxld~zer mixtures. The fiel can be any combustible
uid materials, combustion occurs at or near the surface. For material withjn or around the vehicle or of the vehicle itself.
gaseous materials combustion occurs in the volume in ,,
i
which a flammable mixture of combustible gases, e.g., fuel 2-2.1 IGNITION
vapor and air, exists. For solid propellants for which the oxi-
Ignition is dependent upon the state of tbe combustible
dizer in solid fomn is mixed intimately with the fuel, which
material. To have a fast-growth fire when the oxidizer is pri-
is also in solid form, combustion will start at the place of
marily atmospheric oxygen, the fuel must be a vapor, mis~
ignition and travel through the propellant at a rate affected
or dust. A very minute quantity of heat energy can cause
by the surrounding pressure.
ignition of vapor, but greater quantities of heat energy are
Flaming combustion occurs when the combustible mate-
needed to ignite mist or dust. When the combustible mate-
rial is in the gaseous state. Most combustible materials bum
rial is in large globules, pools or bodies of liquid, or in large
in the gaseous state; this is true for hydrocarbon fuel (liq-
particles or objects of solid matter, a slow-growth fire is
uid), magnesium (solid), and the volatiles in wood. Solids
more probable unless a great quantity of energy is involved.
decompose, sublimate, or melt and then vaporize to burn. A
Ignition isdescribed for bo~ flfid and solid combustibles.
liquid vaporizes to burn. The volatiles in wood decompose
Solid combustibles that contain oxidizers, e.g., solid propel-
to bum as gases; then the remaining carbon bums as a glow-
ing solid. lant, bum at: a rate dependent upon the surrounding pres-
sure. They burn slowly at atmospheric pressure and more
Smoldering or glowing combustion occurs when the
combustible material is in the solid state. Carbon, such as rapidly as the pressure increases.
coke or charcoal+oal or wood after the volatiles have
been boiIed out, burns in two stages as a glowing mass. In 2-2.1.1 Fhid Combustibles
the first stage the solid carbon combines with atmospheric The presence of gaseous fuel, oxidizer, and an ignition
oxygen to form carbon monoxide. In the second stage the source is not sufficient to assure that ignition will occur. If
gaseous carbon monoxide combines with atmospheric oxy- the “fuel-oxitlzer mixture is lean in fuel, ignition will not
gen to form carbon dioxide. occur even if the amount of energy injected by the igniti”on
Combat vehicle fires can be categorized by rate of source is enormous. The same is true within limits if the
growth, means of ignition, fuel type, and fuel location. Such fuel-oxidizer mixture is extremely rich in fuel. At an
tires may be internal, external, or on the ground. Each cate- extremely ~gh temperature, such as that achieved by the

2-2
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MIL-HD8K-684
burning of combustible metals. some materials present can

o be altered to provide more easily ignitable ones, e.g., water

carI disassociate into hydrogen and oxygen. As illustrated in (uqlictwirlAirl 3% A
Fig. 2-1, there is a limited ramge of fuel-air mixtures in
which iagnitioncan occur. This figure shows the existence of
a lower limit of flammability and an upper limit of flamma-
bility between which ignition can occur. Between these lim-
Poa@W
Dl%a,
DF-
OF-1.Snd’JPa
E
its lies the optimum concmtration at which the least amount Fkmrmme”wi
of energy is required to achieve ignition. For combustible
vapors and atmospheric oxygen this optimum concentration
is near the stoichiometric ratio.
.h lMi Re@on

/ a.-&”- 1
2-2.1.1.1 Ignition of Fuel Vapors
For vaporizable liquid fuels tkrnmability characteristics
may be represented graphically, as shown in Fig. 2-2. This
figure illustrates the volatility and flammability chamcteris-
tics of common military mobility fuels, i.e., motor gasoline
@lOGAS), jet propellant (JP)4, JP-8, diesel fuel (DF)-1,
DF-& JP-5, and DF-2. This graphical portrayal was devel-
oped specifically for we in this handbook by using estab ~vs$orinAq
Iished estimation procedures to extend existing data from
Refs. 3,4.5, 6, 7, and 8. In Fig. 2-2 the centrally located
vapor pressure curve separates liquid fiel on the left from
/ I
vaporized i%el on the right. The flammable vapor mnge for Temperature, “C
each of the illustrated fuels lies within the shaded areas.

,,.
,
NOTG Shaded Areas S@ily Ftarnmable Regons
between the lean limi[ (lower bounckuy) and the rich limit
(upper boundmy)+ to the right of the vapor pressure curve.

0 The intersection of the lower limit boundary with the vapor

pressure curve comqonds to the theoretical flash point of
each fue~ i.e., the lowest temperature at which the surface
Figure 2-2. Qualitative Representation of Fiam-
mabtity Liits on Military Mobility Fuels
(Ref. 2)
of a liquid fuel can support combustion. The vapor pressute surface vapor concentration, as shown in F@ 2-3. The theo-
data for each of the fuels correspond to the in-solution vola- retical flash points of these fuels at their flammability limits
tilig of the most volatile constituents of the fuel. This con- are presented in F@ 24. The flash point of JP4 is not con-
cept is consistent with the observed effects of mixing a
trolled by the military specification and can vary through
volatile fuel with a rdatively nonvolatile &e!. For example,
the values shown in Figs. 2-2,2-3, and 24.
if a small quantity of JP4 is mixed with JP-8, the most vol-
atile JP-4 components will dominate the vapor pressure and

40
.
adansed F@ in Are -Vapobad F@ h A&
f
f- 920 -
apor Pre$salra Cauvtt
g-
{ i%ral-VanorRich 2
so -
if!
-m -

-40 t 1 t I
0 a 40 60 m 1J
votume of JP4 in JP-4/JP+ Btend. %

~ F’iguR 2-3. Blends of Fuels With Widely Differ-

T~ ~ ing Volatile Synergistic FhMh Point Effects
Figure 2-L Fuel Flammability Ranges (Ref. 1) (Ref. 1)

--
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lWliL-HDBK-684

10~
(2-1)

where
D~~ ~ fuel droplet diameter. ~
~ ~~ fuel droplet evaporation factor, ~~/ms.

For example, the time required to evaporate a 100-~m

droplet at ‘flame temperamres of approximately 1927°C
(3500”F) is about 25 ms, and a 10-pm droplet would evapo-
rate in about 0.25 ms. When droplets in a combustible mix-

1
ture are less than 20 @, a flame can propagate through the
mixture at up to twice the rate that would exist if the fuel
had been c~mpletely vaporized. With larger droplet size this
flame prop~gation rate decreases. Therefore, flame propaga-
tions through fuel vapors, fogs, and mists all occur at almost
Temperature, ‘C the same rate. Large convective currents are present when
fuel vapors, fogs, and mists are formed due to ballistic
Figure 2-4 Comelation of~eoretidflxh
attack. These currents result in a significant increase in
Points With the Flammability Lmit Composi- flame speed.
tions for Standard Military Mobwty Fuels There are basically two types of mixing processes. The
(Ref. 2) first is simple diffusion, sometimes accompanied by mild
convection! This is found in relatively quiescent fuel/air
Volatile fuels,. such as MO(3AS and JP-4, whose vapor
interfaces. Because the mixing is relatively slow, the bur-
compositions are above the rich flammability limit, are not
ningprocess’ is also slow. The second form of mixing is tur-
nonflammable. Because of their high volatility, such fuels
bulent mixing; it is much faster than simple diffusion
generate vapors that can diffuse or be carried into the air in because the fuel and air are carried together by fast-moving
surrounding regions with compositions ranging from over- eddies. Turbulent mixing is the dominant mixing process of
rich at the liquid surface to zero at sufficient distances from most practical combustion systems and of rapid-growth
the source liquid. Hence the compositions pass through the fires. ~
flammable range as the vapors travel from the fuel source In this discussion the concern is the combustion of a
into the surroundings. Moreover, because of their mobility, cloud of a~omized fuel formed by the impact of a high-
such vapors can encounter ignition sources remote from the speed pene~ator upon a fuel cell. In this case, the cloud of
liquid fuel source. atomized li~uid t%elis very dense and there ii only a limited
supply of &r within the cloud. As the fuel droplets evapo-
2-2.1.1.2 Ignitim Of Fuel Mist rate, the fuel-air mixture becomes very rich, and the cloud
Diesel .fuel mist or spray requires slightly more energy to will not bu’rn because the fuel concentration has exceeded
ignite than does gasoline mist or spray. Hydraulic fluid mist the rich t%$nmability limit. Consequently, combustion is
or spray requires slightly more energy to ignite than does possible only near the periphery of the cloud where there is
diesel fuel mist or spray. These inists or sprays, however, a substanti$ supply of oxygen. When an ignition source,
are still easily ignited, especially since ballistic impacts cre- such as a spark or a burning incendiary, is present at the fuel
ate strong ignition sources. cloud/air interface, a diffusion flame quickly envelopes the
Liquid fuel mus? vaporize before it will bum. The process cloud. In a diffusion flame the fuel is not initially mixed
of combustion consists, of three steps: (1) fuel evaporation, with air, so mixing is the rate-contro~ling step in the burning
(2) mixing of fuel vapors in air, and (3) oxidation reactions. process. When the fuel cloud is produced by a high-energy
The rate of flame propagation and heat release will always penetration of a liquid fuel source, the turbulence in the fuel
be limited by one of these. processes. For example, if fuel cloud and the surrounding air is such that they mix at a rate
evaporation and mixing are relatively slow, the burning rate much faster than in still air. This increased rate of mixing of
will be limited because fuei must vaporize and mix with air the fuel vapors and air increases the burning rate and conse-
before it will bum. quently the: heat release rate until the turbulence produced
we droplet evaporation rate is strongly dependent on the by only the burning fuel creates a self-sustaining mixing of
droplet diameter. According to Godsave’s Law (Ref. 9), the the fuel an! air, especially when the droplet diameters are
droplet evaporation time ‘cin milliseconds can be expressed larger, i.e., ’50 ~m or greater. Fuel mists or sprays are pro-
as duced when a ballistic penetrator punctures a high-pressure

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MIL-HDBK-664
line or a nonpressurized vessel that is then pressurized
through hydmtdic ram. A small puncture in a high-pressure
o line is worse than complete severance because the small
puncture creates a spray, whereas sevemnce produces a
stream.
If the release of these mists or sprays can be prevent~
the most hazardous of the hydrocarbon fuel forms can be
eliminated. Diesel fhel mists or sprays normally occur when
the fuel ceil is pressurized localIy by hydraulic ram that
results from ballistic impact, and the spray is released at
failures in the fuel cell. These fuel cell failures include the
perforation made by the projectile or jeh the rupture of
seams, and the tearing out of bosses or other attachments.
These failures can be precluded by proper fuel cell design
and fuel cell material selection or by fuel cell confinement
or reinforcement.
Also. as indicated irt Fig. 2-2 for vaporizable liquid fuels,
i=gtitionand combustion can occur in the region to the left
of the vapor pressure cr.uve if the liquid phase is dispersed
as a spray or mist in air. Thus, the flammable range cannot
be indicated on the graph because it is determined by com-
plex interactions among variables involving the tmture of
the misL its environment, and the type of ignition source. A t I i I I i
discussion of the major difference between flame propaga- -m -10 0 10 20 m’
tion in suspensions of liquid droplets in air and in mixtures Temperature, “C

,,
of fuel vapor in air follows. Reprintedwirhpermission.Copycight@by CoordinatingResearch

,’
o
The lower flammability limit for a mist on a weight basis
in some cases may be less than that of the same fuel dis-
persed as a vapor-air mixture. h is partly because of thk
Council,Inc.
F-2-5.
Military
Minimum Energy to Jgnite Selected
Fuels in Spray Form (Ref. 10)
phenomenon that the fire or explosion hazards posed by fuel
misls are substantial even though the energy required to the heavier fluids and are lost from the blend as it “ages” or
i=tite a mix is substantially ~~ater than that for a gaseous ‘Weathers”. DF-2 has been crudely described as a blend of
mixture. Fig. 2-5 illustrates the minimum energy required to decane 19%, cetane 57%, docosane 14%, C?-benzenes 5%,
achieve spark ignition of JP4, JP-8. and JP-5 sprays or and C2-naphthalenes 5% (Ref. 13). .This is a simplification,
mists and the effects of temperature on the minimum igni- of the composition of DF-2.
tion energy (Ref. 10). Mists may be highly flammable, even when the tempera-
Mobility fuels are blends of many hydrocarbon fluids.
ture of the droplets is substantially lower than the flash point
Ignitability of a blend depends primarily upon the lighter—
of the fuel. In addition, flame propagation rates and the
cad by molecular weight-hydrocarbon fiuids (Ref. 11).
0> resulting blast over-pressures in mists can be greater than in
The simpler of these fluids are described in Table 2-1, and
gases, depending on the properties of the mist and the com-
the energy required to ignite the vapor of the lighter of these
position of cbe liquid t%el.In view of the unique characteris-
is shown in Fig. 2-6. There is not a great differenm in the
tics of flammable mists, their importance relative to combat
minimum ignition energy for any of these vapo~ but bodt
vehicle fire safety cannot be overstated
the vapor-air mixture ratio at which the minimum energy is
effective and the overall mixture ratio ignitability range
2-2.1.13 Geometry Effects
increase with an increase in fluid molecular weight. These
lighter hydrocarbon fluids are present in mobility fiels to a The ability of an ignition source to achieve ignition in the
vqi.ng degree. More are present in fuels with a lower flash presence of a flammable fuel-air mixture depends not only
poin~ e.g., JP-4, than in a fuel with a higher flash poin~ e.g., on the temperature or energy content of the ignition source
JP-5. Since these lighter fluids, e.g., methane, etlmne, or but atso on its geometry. As shown in Fig. 2-7, the source
propane, are more volatile than the heavier ones, e.g., temperature required for ignition increases as the surface

,,
o
,,
decan% tridecane. or cetane, the lighter fluids, which are
present in freshly relined fuels, are basically absorbed by
area of the ignition source decreases. The greatest tempera-
ture or energy content is required for electrical sparks.

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MIL-HDBK-684

TABLE 2-L PROPERTIES OF SIMPLE HYDROCARBONS (Ref. 12)

FLUID FORMULA MOLECULAR SPECIFIC GRAVITY BOILING POINT, ‘C 9
1 1
WEIGHT ,
DIMENSIONLESS!I AT “C !
AT ATMOSPHERIC PRESSURE
Methane CH, 16.04 I 0.466 @ -164 ‘ –164
Ethane C,I-I, 30.07 I 0.572 @ -100 –88.6
Propane C~H* 44.11 0.5853 @ +45 42.1
Butane C4H10 58.11 0.6012 @ O -0.5
Pentane C~H1, 72.15 0.6262 @20 36.1
Hexane CcH,, 86.18 0.6603 @20 69.0
Heptane C,EI,6 100:21 0.6837 @ 20 ~ 98.4
Octane C8H18 114.23 0.7025 @ 20 114.23
Nonane C9H20 128.26 0.7176 @ 20 150.8
Decane 142.29 0.7300 @ 20 174.1
Tndecane ! ::; 184.37 0.7564 @ 20 235.4
Cetane* \ C1,I-IW I 226.45 I 0.7733@ 20 287
Docosane C,, H,, 310.61 0.7944 @ 20 368.6
*or hexadecane

2-2.1.1.4 Ignition of Vapors by an Exploding explosive following frapents that perforated a crashwor-
Charge &y, caliber ‘(cal).50 self-sealing panel, which was along one
An example of the ignition of an explosive JP-4 vapor-air wall of the fuel cell. Figs. 2-8(B) through 2-8(I) show this
cloud of detonation products traversing the ullage to a simi-
mixture by the products of detonation flom a 23-mm high-
lar crashworthy, cal .50 self-sealing panel on the opposite
explosive incendiary tracer (HEIT) projectile impacting at
wall. Note that this cloud of detonation productsj which Q
472 m/s (1548 ftis) is shown in Fig. 2-8. This figure illus-
contained numerous glowing particles of ah.un.inum that
izates a sequence of events after a 23-mm HEIT projectile*
were the probable source of the light photographed, did not
detonated on the outside surface of a fuel cell containing JP-
4 near –7°C’ (20”F). An explosive mixture of fuel vapors
and air formed within the ullage. A high-frame-rate motion
picture camera recorded events within the”ullage through a ““ ‘“

k“”’
yrmaJsPhIfG”’ “
transparent top of 3.2-mm (O.125-in.) thick acrylic. Fig. 2-
8(A) shows products of the detonation of an aluminized
Region of ignition

Metfwle

I I ! I
—
1 ! i I
0.4 o.a 1.2 1.6 5.0 2.4 2.0 a
Combustiblein At ss Fractionof Stoichiometric
Ratio,dimensionless

Figure 2-6. Spark Ignition Energy vs Fuel-Air I+etstedVeeseU

Composition for Various Straight Chain Satu-
rated Hydrocarbons in Vapor State (Ref. 3)
L
~Spatial Dimensions of Heat Source ~
*The MG-25 faze of this projectile had been modifiedto produce
an almost super quick function rather than the normal delay fanc- Figure 2+7. Relative Ignition Temperatures of a
tion. Heat Sources (Ref. 14)

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MIL-HDBK-684

(A) Frame 1,100 ps (est..) (E) Frame 6,725 M (I) Frame 20,2.475 ms

0,, (B) Fmnte 2,2,225 ps (F) Frame 8,975 I.IS (J) Frame 32,3.97 rns

(C) Fiarne 3,350 w [G) Frame 10,1.255 ms (K) Frame 36,4.475 ms

I
~

1.

(D) Frame 4,475 w (H) Frame 16,1.975 rns (L) Frarne91, 11.35 ms
Re@nted with permissionof Bell Helicopter-Texmm.
r%+
~ F&me 24 ‘1’hneSequenceFrom 23-mm =~@nation b -e Vapor Combustion (Ref. M)

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,1

MIL-HDBK-884 ~
ignite the explosive mixture and were either cooling or col- 3. The lowest temperature Ti~ in K at which a partially
lecting on that far wall until approximately the time of Fig.
2-8(I) when the vapors in the ullage ignited. At the time of
Fig. 2-8(L), the transparent top of the test fixture began to
submerged ;!steelsphere can ignite diesel fuel near its flash
point is
~ a
rupture (Ref. 15). T;] = 1338 exp(-O.0073611J, K (2-2)
where jg
2-2.1.1.5 Ignition of a Spray by a Heated Surface
D,~ ~= sphere diameter, mm.
When heated surfaces ignite a fuel spray, ignition temper-
1,
atures exhibit an apparent inverse volatility effect. The sur-
4. The apparent activation energy E., i.e., the energy
face temperatures required to achieve ignition of a
hydrocarbon fuel spray increase with increasing fuel volatil- needed to ignite the fuel, for diesel fuel is 32 kcaUmole.
ity, even though the minimum autoignition temperatures 5. G~oline was ignitable by hot steel spheres at fuel
remain about the same (Refs. 4 and 14). Similar effects have temperatures of –78°C (–108”F) and O°C (32”F), but the
been observed for hot-surface ignition of low-volatility gasoline vapors formed were too fuel rich to be ignited at
hydrocarbon oils. An explanation of this effect could be in 25°C (77”F9.
the rates of fuel vapor evolution when the liquid fuel
impinges on the heated surface; these rates would increase 2-2.1.1.7 Environmental Effects
with increasing fuel volatility. Wi~ a more volatile fuel, the In additi~ to the foregoing effects of variables on flam-
location of the vapor-air mixture containing the composition mability, bbth the ignition energy, or ignition temperature,
requtied for ignition under the existing conditions would be requiremen~ and the flammability limits may be altered by
pushed farther from the hot surface than it would for a less en’vironme~tal effects, such as the flow of fuel-air mixtures
volatile fuel because the rate of vapor evolution increases past the ig~tion source. Such influences are shown in Figs.
with fuel volatility. Since the temperature gradient within 2-9 and 2-1o.
the vapor adjacent to the hot surface would be about the
same for different hydrocarbons and if all other physical 2-2.1.2 !$olid Combustibles
conditions are the same, the surface temperature required
Solid coipbustibles that are dependent upon external oxi-
for ignition of the mixture would be correspondingly higher
dizers generally require more heat energy to ignite than do
if the mixture were farther ffom the surface. Obviously,
combustible vapors (Ref 18). If these solids are in the form 9
these inverse effects do not imply that hot-surface fire safety
of dust, ig~ltion can occur at lower energy levels than it can
should increase with increasing fuel volatility. In fac~ the
coincident increase in the evolution of flammable fumes for larger combustible particles, and the combustion can
would represent a decrease in fire safety. achieve a ~ery rapid growth, as is ‘demonstrated by dust
explosions ~n grain elevators. In combat vehicles, such dust
2-2.1.-1.6 Ignition by Hot Pariicles clouds can ~~ fo~ed on a,:mall scale by the ballistic pene-
13nnerty and Schuclder (Ref. 16) explored the ignition of
FlowVelocity,
R./s
military fuels by hot particles. Their work concerned the sit-
_.-O l!20 40 60 80 100 120 140 160 180
uation in which a small, hot particle came in contact with
liquid fiel. This could occur where hot span or a shaped-
charge slug could come to rest in a puddle of fuel on or in a.
combat vehicle. Stainless steel spheres were used for the
particles. DF-2 and MOGAS were used to test both low-
and high-volatility fuels. The spheres were heated and then
dropped into fuel in a container. The size of the sphere and
the depth of t~e fuel were adjusted so’that approximately a
third of the sphere would protrude above the fuel surface
unless complete immersion of the sphere was desired. A
sustained fire was adjudged only when the entire fuel sur- 2 II Ratio
8to”d”kwliebk
face burned; otherwise, the result was judged to be no igni- m Ill
~ 80 -J
tion. & p
Lem Limit
The conclusions were 40~ 1 I I I
1. Diesel fuel can be ignited by partially submerged o , 10 20 20 40 50
hot particles as long as the fuel temperature is 30°C (86°F) Flow Vetixity, lllh
or higher. ,
2. Fully submerged particles can ignite diesel fuel at Figure 2{$ Effect of Airflow Upon Flame Prop-
a
or above its flash point. agation (Ref. 4)

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MIL-HDBK-684

m’ ‘“”-e ‘

Figure z-lo. comparison OfIgnition Tenlpera-

tnres of Two Aircraft Fuels With a EIeated 51-
mm (2-in.) Diameter by 610-mm (24-ii) Long
Wed Target (WE 17)

uation of a solid material layer by a fiagmenq a kinetic

energy penetrator, or a shaped-charge jet. An image con-
verter was used to obtain a series of five photographs taken
at 2G ps intervals to establish the terminal effect of steel
fragments fired into tin targets in order to obtain penetm-
tion data Fig. 2-11 shows such a series of photographs in
which a steel fiagmen~ traveling from right to left at 1754
m/s (5753 Ws), impacts a thin aluminum sheet. lhis impact
occurred after the first Iiarne (top) but before the second
i%umt. Note the fiash or sphsh-baclq which appears to the
right of the target sheet. Note also the cloud of particles of
shattered figment and span, which appears to the left of the
target sheeL This cloud of panicles and span was accompan-
ied by a strong flash ffom small pieces of span that com-
busted in the air. F~g. 2-12 is of a similar test in which the
meel fragment impacted a titanium sheet at 1861 mk (6106
R/s). In this test the lop frame was taken shortly afier
impact. The flash was stronger than the one emitted by the
aluminum sheet in the previous figure. In a program to
estahkh the effectiveness of external fuel ceils to enhance
the smwivability of a combat vehicle given a small shaped-
charge impact (Ref. 19), tests were performed to establish
the ckaetems . tics of the flash generated when the shaped-
US Air Porte Photograph.
charge jet perforated a simulated vehicle wall. Fig. 2-13
shows the test installation just after the shaped-charge jet Figure 2-11. Front Face Splash Emit&l by
passed through 6.25-mm (0.25-in.) thick steel on both sides
Aluminum 20UT81 Sheet When Impactedbya
of the fixture. lhis fi-ame, taken fkom the real-time motion
picw shows the warhead detonation fireball escaping
steelFragment
TArOugh tie smallannularspacebetweenthe figment trap
and the entry face of the fixture, the jet flash (i.e., a combi-
nation of ionized air from the jet passage and flash fkorn the

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NllL-HDBK-884

Figure 2-~3. Shaped-Charge Jet Perforating

Steel P1ates on Both Sides of a Test Fixture
(Ref. 19)

steel spall)l the splash from the rear face, and the rear face
jet and span flash. In one test, shown in Fig. 2-14, the simu-
lated vehicle wall was 6.25-mm (0.25 -in.) thick rolled
homogeneous armor (RHA) steel. In another test, shown in
Fig. 2-15, the simulated vehicle wall was 25.4-mm (lo-in.)
fick Aluminum 5083. In both figures, the jet traveled horn
left to righ~i The flash, which is seen to the left of the test
fixture wal~tis a fireball from the shaped-charge detonation.
Note that tie shaped-charge fireball persisted for over 20 ms
in both test$ but the RI-IAflash had vanished within 10 ms, 4
as seen in Fig. 2-14(C). Actually all light within the test fix-
ture was gone in 9 ms. The aluminum flash was still visible
after 20 ms;las seen in Fig. 2-14(D), and all light within the
test fixture was gone in 28 ms. This aluminum flash was
both more $illiant (Note how ,Frames 1 and 4 are “washed
out” in Figs. 2-15(A) and (B) compared to the same frames
for Fig. 2! 14.) and had a longer duration-over three
times-than the R.HA flash. As with the steel fragment
impacts shown in Figs. 2-11 and 2-12, the flash appears at
both the impacted face of the target and at the exit face. In
all of these cases the perforation flash, although not a haz-
ardous fire ‘itself, is an ignition source that can ignite liquid
fuel mists caused by a ballistic penetrator that perforates a
fuel or hydraulic system component.
Combustible metals, such as magnesium and lithium,
pose a pecdiar problem. Many fire extinguishants cannot be
used because of the high burning temperature of these com-
bustible metals. These temperatures are high enough to
break down some extinguishants. HaIons containing chlo-
rine, e.g., 1211, can produce pbosgene, a toxic gas, when
exposed to high heat levels. Water will disassociate into
USAir Force Photograph. oxygen and hydrogen, which later can explode upon recom-
bination. In addition, high-temperature engine parts can
Eigwre 2-12. Front Face Splash Emitted by a cause diesel fueI or hydraulic fluid to break down into more
Thaniwn 6M 4V Sheet When Impacted by a volatile hydrocarbon fluids that are more readily ignited. a
Steel Fragment Because of the danger involved when the more commonly

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(A) Frame 1, t = O
(A) Frame 1, r=O

(B) Fmme4, t=3ms (B) Frame 4,t=3ms

0
,*!,

(C) Frame 11, r=lOms (C) Frame 11, t=lOms

@) Frmne21, r=20ms @) Frame 21, r=20ms

1!~igum 2-14. Flash Emitted by RHA Steel Tar- H gwe 21S. Flash Emitted by Ahuninum Tar-
get (N& D] get (Ref. 19)

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,,” .
:. WN’L-HDBK-684 ~
used fire extinguishants encounter bu~ing combustible listic perforation of the cartridge case by a fragment or pro-
metals, the National Fire Protection Association (NFP.$) has jectile. In a test program that evaluated the use of selected
established a separate classification, Class D, for combusti- fire extinguishants to mitigate the della=mtion of the propel-
ble metal fires (Ref. 20). ‘, lant charg$ of a 105-mm cartridge (Ref. 23), the baseline
When there is a gross release of energy, as in the detona- test demonstrated how the propellant charge reacted to per-
tion of a high explosive, pieces of moderately combustible foration b~~the jet from a US Army Ballistics Research Lab-
materials, such as polyethylene or aluminum tubing sur- oratory (B~) 8 l-mm precision shaped-charge warhead. In
rounding the explosive, can deflagrate in air (Refs. 21 and these tests ~the 105-mm cartridge was placed within a 0.76-
22). This deflagration probably occurs because the detona- m (30-in.) diameter steel pipe, a tank hull was simulated by
tion and ensuing outward expansion of detonation products steel plate~~and the shaped charge was detonated so that the
can pulverize and heat the surroundhg materials and drive jet perforated the simulated hull and then the cartridge. The
them outward to contact atmospheric oxygen and thus pro- reaction OPthe gun propellant to perforation by the shaped-
mote combustion. charge jet is shown in Fig. 2-16. This violent reaction was a
deflagration, as was shown by examination of the remnants
2-2.1.3 Solid Combustible-Oxidizer Mixture of the ca.r$dge case. (The even more violent reaction, seen
Gun propellants are examples of solid combustible-oxi- to the right of the pipe, is the detonation of the shaped
dizer mixtures. Such mixtures can be initiated by heat.+hot charge. Th} rod of light seen to the left of the pipe is the
‘ particles, impact by a shaped-charge jet or hypervelocity reaction of ‘the air to the passage of the shaped-charge jet.)
projectile, and severe deformation or crushing. The heat can
be from a fire and be added rather slowly to the propellant 2-2.2 G&OWT13!
itself or to the casing that encloses the propellant. The hot The gr~tvth of fires following ignition is affected by
particles can be from a primer composition or from the bal- availability of fuel and oxidizer, by the addition of heat, and
II

-Figure 2-16. Reaction of Gun Propellant in 105-mIn Cartridg~ to Perforation by a Shaped-Charge Jet
(&f. 23) !1
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MIL41DBK-684
by location of the fire. Both fuel and oxidizer must be 2. Shaped charges including high-explosive antitank

o present for a fire to sustain itself, let alone grow.

The addition of heat makes combustible materials more
%ammabIe. Liquid fuels vaporize with the addition of heat.
@lEAT) projectiles fired fkom guns and warheads of rocket-
propelled missiles or shoulder-fired rockets like the light
antitank weapon (LAW) and rocket-propelled grenade
Solids melt and then vaporize with more hea~ or the vola- m)
tiles in solids boil out with the addition of heat. On the other 3. Armor-piercing, high-explosive incendiary (APHEI)
hand, when heat is removed, the growth of a fire slows or armor-piercing, incendiary tracer (APIT) projectiles
down or stops, or the fire dies down and can be em.in- 4. Incendiary threats, such as Molotov cocktails as
guished. well as the mcket-proplkd flamethrower (IWO) and
The location of a fire affects fire growth primarily as a rocket-propekd fhunethro wer-airbome (RPO-A), or sirni-
fimction of where the heat is applied to the fuel. The addi- Iar incendiary mixtures dispensed horn aircraft
tion of heat makes air expand. The hotter air, being less 5. Fragments from high-explosive projectiles
dense, rises and carries the heat and flames upward. Fuel 6. Land and beach mines including those with explo-
that is above the fire becomes hot more quickly than fuel sively formed penetrators and some rype of shaped charge.
that is alongside or below the fke, so the fire travels upward One combat vehicle threat left off this list is a fuel-air
quickly. Fwe can travel laterally or downward but at a much explosive (FAE) weapon, which would probably not
ksser rate. involve combustion of other materials as a damage mecha-
If the combustible is an intimate mixture of fuel and oxi- nism.
dizer, e.g., gun propellan~ the fire moves through the mate- The assumption that the threat overwhelms or bypasses
rial. Gun propellants are known to bum more rapidly when the vehicular armor is used. l%roughout the history of com-
in a confined space because an increase in pressure causes bat vehicles, armor and antiarmor threats have been in com-
an increase in the rate of combustion. petition-first with the armor superior and then with the
From the standpoint of the survivability of combat vehi- antittrmor threat superior. Currently, combat vehicles
cles, h can be categorized as %apid-growth fires” and include rather Iightly armored ones, such as armored per-
“slow-growth fires”. These are described and discussed in sonnel carriers or fighting vehicles, as well as the heavily

.,,, the paragraphs that follow. armored main battle tanks (MBT). Also these M13Tsare not
armored all over to the same degree. The 60deg tkontal arc
0“, 2-3 RAPID-GROWTH FIRES
Fms in combat vehicles can result in the destruction of
has the heaviest armor, the sides are less heavily annorwi,
and the rear, top, and bottom are even less armored. There-
the vehicle and loss of the crew. Combat vehicles contain fore, even the best-armored vehicle is vulnerable some-
fkunrr&le hydrocarbon fluids and explosives. When a vehi- where. Combat vehicles should be designed so that if the
cle is struck by a figment or projectile that interacts with armor is defeated, a catastrophic failure will not occur. A
either of these energetic materials, a tapid-growth h can catastrophic failure as considered here is an expIosion or a
resuk This rapid-growth fire can be a low-order explosion, fast-growth fire. “
i.e., a deflagration. Rapid-growth fires are characterized by
being too fast for the vehicle occupants to reacc therefore, 2-3.1.1 Kinetic Energy Threats
any fire prevention system must be automatic, i.e., not There are many types of ICEpenetrators that can pose a
dependent upon personnel to activate or direct its employ- threat to combat vehicles. T%earmor-piercing (AP) bullet of
ment. Rapid-growth firm are often. initiated by munitions, World War i is still available. The tank and antitank gun AP
but such a fire can start from other causes, such as a hydmu- projectiles of 2 1/2 to 3 calibers in length used in World War
lic fitting failure that sprays fuel or hydraulic fluid onto an II are still around, although they are no longer the pMcipal
engine hol spot. antitank threat. The newer ICE projectiles are the long rod
penetratom. TEese long rod peneuators can be made of
2-3.1 MUNITION INITIATION hardened steel, tungsten, or depleted uranim, are from 10
Combat vehicles can be attacked from any direction. to 12 calibers in length; and are launched using sabots,
Some of the weapons employed will not be as serious a which drop off after the projectile leaves the muzzle. Many
thma to the combat vehicIe as others. Lightly armored com- of the long rod penetrators, e.g., armor-piercing, fin-stabi-
bat vehicles can be seriously damaged by weapons to which Iize4 discarding sabot (APFSDS) have fins, unlike the ear-
a heavily armored vehicle is almost invulnerable. lier armor-piercing, discarding sabot (APDS) projectiles of
Currently, we can expect to have the following types of 3 to 4 calibers in length, which &pended upon spin alone
weapons used against our combat vehicles: for stabilization.
L IKE penetrators including armor-piercing projec- Penetrators often break up during penerratiou particu-
tiles long rod penetrators fired at very high velocity, pyro- larly if they impact at a sticiently large angle of obliquity
phoric penetrators, and explosively formed penetrators or encounter successive surfaces that are at different angles

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MIL-HDBK-684
of obliquity. Where the target ii ‘overwhelmed, the breakup 914 m/s (3000 fW) and is still a minor contributor to the jet
can result in damage to fuel system components, stowed velocity with respect to the target.
munitions, and other items by multiple projectile pieces. The fragmentation from the shaped-charge projectile 9
These KE penetrators, intact or in pieces, can rupture fuel body wouldl have a primary velocity directed sideward. At
II
zero degree ~obliquity,only where projectile impact velocity
celIs and cause a spray of fuel within a vewcular compart-
ment. Impact of these tiagments could initiate the propellant approaches 914 nis (3000 fds) would any casing fragments
in a rocket motor. impact nem~the hole in $e target surface created by the jet.
When passing through a materiti, kinetic energy penetra- ~ese casidg fragments would most probably be from the
tors produce a flash and span similar to those shown in Figs. base of the projectile, would have a comparatively low for-
2-11 and 2-12. Flashes in these figures appear on bo~ he ward velocity (This velocity would be the difference
impacted faces of the targets and the exit faces. Also the between the projectile velocity at impact and the velocity
flash emitted by titanium in Fig. 2-12 is more intense than imparted by the charge detonation.) and a comparative] y
that from ahuninum shown in Fig. 2-11. These flashes are large size (much larger than the hole produced by the jet),
strong ignition sources that can ignite a fuel mist resulting and would probably be unable to penetrate through the vehi-
from a penetration. cle armor. ,~e other projectile casing fragments, which
Depleted uranium penetrators not only cause extremely would probably be lighter but have a higher velocity, would
sgong flashes but are in essence pyrophonc, i.e., produce most probably not penetrate through the vehicle armor
sparks when they srnke steel or ignite spontaneously in air either. Thus the behind-the-armor effects would be pro-
when in a finely divided state. duced by the jet and the slug (if it also passes through the jet
Another kinetic energy threat is from fragments from hole). This, jet would probably produce a comparatively
high-explosive-filled projectiles. Fragments would produce small dkuneter hole in steel armor but a larger hole in alu-
the same effects after penetrating fie armor as would the AP minum ~or. Where a fuel system component is inter-
penetrators. Some of the older AP penetrators contained a sected, this jet would probably perforate the fuel system
small quantity of high explosive, which was initiated by a component land the fuel and most internal components of
delay fuze. These would produce fragments as well as a the vehicle jn its path and may exit the vehicle through the
opposite side. This action has been demonstrated repeatedly
small blast within the vehicle after penetrati~g.
in tests. These tests showed that a small amount of fuel
vapor followed the jet through the hole in the inside wall of
2-3.L2 Chemical Energy Threats a
the fuel cell and burned in a fireball inside the vehicle. In
HEAT warheads were first fielded during World War II by many tests ,$hebulk of the fuel in the vehicle compartment
the U.S., England, and Germany. These warheads employ leaked from open seams of the fuel cell.
focused chemical energy and are frequently referred to as In a series of tests of a thin-walled, welded, metal fuel
shaped charges. This round in its simplest form consists of a cell, which ~was mounted on the inside surface of a combat
cylinder of high explosive with a conical cavity at one end. vehicle, the’shaped-charge jet pressurized the fuel through
The cavity is lined with a thin metallic liner. When the the hydrau$c ram effect. The welded seams ruptured, and
explosive charge is initiated, the liner collapses to form a the liquid c~ntents sprayed into the vehicle. Fig. 2-17 shows
stream or jet of high-velocity, high-density material. The jet frames taken from the high frame rate motion picture—
is followed by a relatively slow-moving slug. The jet is 1000 frames per second—from the test in which the fuel
capable of penetrating homogeneous met@ armors having cell was filled with water. These frames show the generation
thicknesses equivalent to several times the cone diameter of of incandescent particles, which can cause ignition of a fuel
the warhead. spray. In Fig. 2-17(A) the jet has already traveled from right
A shaped charge is presumed to detonate at nominal war- to left. A puff of mist has emerged from the hole through
head standoff on contact with the outer surface of the vehi- which the jet passed, and the seam in the fuel cell has
cle. Most fin-stabilized, rocket-propelled HEAT projectiles opened al~ost 2/3 of its leng~. Sprays of mist can be seen
are traveling at a relatively low velocity at impact, e.g., the that have emerged through similar splits in the front seam of
velocity of the Russian RPG-7 is approximately 294 m/s the fuel cell. In Fig. 2-17(B) the mist from the jet exit hole is
(965 ftfs) (Ref. 24). Hence the greatest warhead effect dispersing ~d that the seam has opened farther. Also the
against me vehicle is obtained from the jet formed by the mist spraysl from the front seam split(s) have dispersed. In
shaped charge. The tip of this jet lm.sa velocity of approxi- Fig. 2-17(~) a heavy mist spray is emerging from the split
mately 7620 m/s (25,000 ft/s). Obviously, the-velocity of the seam. Also ~’’sparklers”,probably from the impact of the jet
shaped-charge jet is primarily due to the chemical energy of on the far yehicle wall, are coming into view emoute to the
the warhead; the residual velocity of the projectile has only locations o! the mist sprays. In Fig. 2-17(D) the sparklers.
a minor contribution to.the velocity of the jet with respect to from the je~ perforation are contacting the outer limits of the
,tie target vehicle. Even when a HEAT projectile is fired spray mist~[In Fig. 2-17(E) the sparklers have continued 9
from a tank gun, the velocity at impact is in the vicinity of toward the’ entry wall. The sparklers and mist are well

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MIL-HDBK-684

o -x

(A) Frame 1 (D) Frame 4

,,,
0 —.-
(B) Frame 2 (E) Frame 5

—
(C) Frame 3 (F) Frame 6

Figure 2-17. Response of Water-Ned Fuel Tank to a Shaped-Cha.rge Jet (Ref. 25)

o
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M! L-HDBK-684
mixed in Fig. 2-17(F). In a similar test, butwith DF-2 in the range of 1~0 m. The charge is ignited on firing, bums in
fuel cell instead of water, the DF-2 ignited shortly after, the fligh~ and her exploding on impac~ produces a fireball 30
sparklers reached the mist. to 40 m deep and 3 to 4 m wide. a
Where a fuel cell is ruptured, the fuel spray enters the The RIW-A has been used by airborne and helicopter-
vehicle compartment in the form of a mist umless special bome troo~. The complete assembly, launcher plus missile,
antimisting addhives are placed in the fuel (Ref. 26). This weighs approximately 11 kg and has a filler charge in the
mist is readily ignitable, but the strongest ignition source is wirhead a~proximately one-half of. that of the IWO. The
apparently produced by the subsequent impacts. of the jet RPO-A ha+ a maximum range of 800 to 1200 m and a max-
with components within the compmtment including the far imum effe~pve range of 400 to 600 m. The accuracy of the
vehicle wall. Ignition of this fuel mist and/or vapor and the RPO-A is two to three times better than that of the RPO.
air within the compartment results in a fireball; the heat The incenc$uy used is a brown liquid, which ignites when
from which can severely injure the occup~ts. Additional droplets lut an object. The same launcher was reportedly
fuel can flow into the compartment through the jet perfora- used in Afghanistan for warheads filled with white phospho-
tion hole and ruptures, if any, in the fuel cell walls or seams. rs (WP) a~d with shrapnel warheads (Ref. 27). Later infer-
This fuel can vaporize from the heat of the ea@ierfireball. If mation (Ref. 28) indicates that this infantry rocket
air is being continuously introduced into the compartment, flamethrower, known as the Schmel, is actually a fuel-air
the resulting combustion can be sustained. The liquid fuel explosive @WE)weapon that is used against light armored
can collect in the bilge, and given sufficient air and heat and vehicles, $x-tifications, and troops. (The Soviets used
an uncovered bilge, a pool fire can result. Afghanist~ as a testing ground for weapons and tactics.
If this jet impacts an explosive-filled object, a-chemical Reports of Soviet activities in Afghanistan were often con-
reaction can be initiated, as shown in Fig. 2-16. If the explo- fusing or cqntradictory.)
sive is a propellant, a defiagration can occur or, with the Another incendiary reportedly used by the Soviets in
stronger rocket propellants, a detonation. The reaction of a Afghanistan (Ref. 29) was a black, tar-like substance dis-
high explosive is less predictable; the result could be any- pensed horn container bombs that spread the incendiary in
thing from a detonation to a mechanical rupture of the cas- large droplets, which ignited when stepped on or when
ing with no reaction from the explosive. Pyrotechnics would driven on. ~The droplets emit flames that shoot upward.
probably burn, ‘but less sensitive or energetic materials These dro~ets continued burning and emitted sickening
would probably not react other than mechanically.
fumes. Trucks driven onto these droplets have burned com- 9
Some land mines are shaped charges directed upward.
pletely. Td~se black droplets were difficult to detect on
These charges can be finely focused to- produce a jet or
isphalt roabk
broadly focused to project a flyer plate, i:e., the Misznay-
Bombs ~eportedly used in Afghanistan contained another
Schardin effect. The jet or plate is directed into the bottom
form of tl& “liquid fire” (Ref. 30). The incendiary was
of the hull of the vehicle, which is less protected tl&I the
described ~ a ~brown” liquid, which was less viscous than
rest of the vehicle. Otherwise, the effects we similar.
the black, ~-hke substmice and more easily ignited, This
incendiary was used in conjunction with small antiperson-
2-3.1.3.’ Incendiary Threats
nel charges. The brown ‘droplets dispensed by the bomb
In 1917 the Germans attacked British Mark IV tanks with were reput$d to ignite on impact; hence this may have been
flamethrowers. In 1940 the Finns used Molotov cocktails—
the same incendiary described for the IWO-A.
a gasoline-filled glass bottle with a burqing wick—with
These i~~endiary weapons are threats that should be con-
great success against Russian tanks. (The Finns named this
sidered in Jhe design of combat vehicles. In urban terrain
simple, expedient weapon to indicate how ~ey planned to
there is the threat of the Molotov cocktail. The RPO and
extend their hospitality to these emissaries of the Soviet
RPO-A present the threat of an improved Molotov cocktail
Foreign Minister, VyachesIav Molotov.)
or a fuel-air explosive device projected from a distance in
Soviet forces reportedly used several incendiary weapons
either urb~ or rural terrain. The “liquid fire” presents a
in Afghanistan. These weapons can pose a significant threat
threat of a pool fire being created under a vehicle on a road,
to our combat vehicles. One of these is the family of rocket-
trail, or open area.
propelled infantry flamethrowers, RPO and RPO-A (Ref.
27). These weapons are similar in appearance and function
to the US 3.5-in. rocket launcher. ‘f%eIWO launcher has a 2-3.1.4 @last Threats
rated tube life of 100 rounds, whereas the IWO-A launcher Blast tt$eats include high-explosive plastic (HEP)—
is a plastic one-shot device. called higli}explosive squash head (HESH) by the British—
The RPO round is a rocket-propelled incendiary charge. and FAE. “
The filler consists of four liters of an incendiary mixture, HEP w~heads crush on the outer surface of an armored
and the complete round weighs 9.25 kg (20.4 lb). The RPO target before detonating. This intimate contact enables the 4
has a maximum range of 400 m and a maximum effective shock wave from the detonation to pass into the armor.

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MIL”HDBK-684
When this shock wave reflects from the opposite surface of Heater fuel lines extend into the troop compartment and are

o the armor and meets a secondary stress wave traveling, tim

the originally shocked surface, the metal fails and sends
span into the vehicle. This effect is felt by the outer atmor
typically controlled by manual valves. External auxiliary
fuel stowage in small quantities is also common and is gen-
erally used to fbel auxiliary generators. Detailed descrip-
layer only, so only monolithic armor is affected. Spaced tions of fuel storage and handling systems are presented in
armor can withstand this type of warhead provided the out- par. 4-3.
side layer does not fail catastrophically.
A fuel-air explosion is the deflagration of an explosive 2-3.2.2 EIaznr&
fuel-air mixture. When such an explosion occurs outside a Combat vehicles are subject to various hazards that could
vehicle, the outer vehicle surface receives significant itnpu~- initiate catastrophic rapid-growth tires. These include non-
sive loading. Light armored vehicles receive significant hostile events such as accidental fuel spillage and impinge-
damage. ment of leaking pressurized hydraulic fiuid or lubricating oil
Both the HEP and FAE or their secondary effects could on hot engine-related surfaces. Hazards resulting from hos-
damage armored vehicles and injure crew members, but nei- tile actions include fuel spillage due to ballistic fuel cell
ther induces fire as a primary effect- rupture, fuel spray caused by projectile penetration of the
fuel cell or fuel line, impingement of leaking pressurized
2-3.2 FUEL hydraulic fluid or lubricating oil on hot engine-related snr-
The types of engine fuels that may be exposed to fire faces, and ignition of stowed ammunition by balliitic
ignition situations in combat vehicles can be categorized in effects.
general terms of volatility, source, and puqwse. Military In thecaseof ballistic penetration of the combat vehicle
tlel types include (in the order of decreasing volatility)(1) crew compartment, several specific situations can be
gasoline motor fuel (MOGAS), (2) gasoline-type aviation defined to represent the possible hazardous conditions.
turbine engine fuel (JP-4), (3) kerosene-type aviation tur- ‘I&se situations are described in Table 2-2 in tem.s of the
bine engine fuel (JP-8), arctic-grade diesel engine fhel (DF- sequence of objects the penetrator encounters as it passes
A), and winter-grade diesel engine fuel (DF- 1), (4) regular- through the vehicle, the fuel forms, and the primary ignition
grade diesel fuel @F-2), and (5) high-flash-point kerosene- soumes, e.g., sparklers fiwm portions of the vehicle that are

0 type aviation turbine engine fuel (JP-5). Other fuel types

include commercial diesel engine fuels, foreign diesel
engine fuek field expedient mixtures, and fire-resistant
impacted. Tbe spurt of fuel maybe interspersed with or sur-
rounded by mist and/or vapor, which can ignite and be a
secondary ignition source and thereby behave as a
fuels. Detailed properties and characteristics of such fuels Ylametbrowef’.
are presented in par. 3-2. In fuel-release incidents the extent of the rapid-growth
fire hazard differs with the type of fuel involved. Genemlly,
2-321 Locations the more volatile the fuel being used+the greater the hazard-
Primary factors in combat vehicle fire survivability am The amount of the other conrnbutors to combustion, how-
the positioning and size of fuel storage cells. The type, num- ever, in a given design or situatiom can modify the hazard.
ber, and hxation of fiel cells are hugely determined by the Highly volatile fuels, such as MOGAS or JP-4, at the stan-
purpose of the vehicle. Historically, primary design consid- dard sea level temperature of 15°C (59W) or higher may not
eration has been given to meeting the range requirement of suppott combustion within a fuel cell baause of insufficient
the vehicle. This, in turn, has dictated the fuel volume air (Tlte fuel-air mixture would be too fuel rich for igni-
requiremen~ The purpose of the vehicle then determined to tion.), whereas outside the cell these fuel vapors, subjected
what extent the fuel had to compete for volume with other to the same ignition source, would burn. On the other IM@
mission-essential materiel, e.g., weapons, ammunition, etc. depending on the extent of ventilation availabie, less vola-
Consequently, resuhing fuel cell arrangements range from a tile fuels, such as DF-2, lubricating oils, or hydmdic fluids,
single cdl system to a tnultip~e cell system with fuel man- could support extensive pool burning inside the vehicle.
agement controls. Pod burning, in turn, could lead to ignition of stowed Class
Fuel cells in many combat vehicles are in or near the A (e.g., cloth, wood, and paper) combustibles or to cook-off
troop compartmen~ this location, given projectile penetra- of other combustibles such as lubricating oil, hydraulic
tion, can diminish crew survivability. Other vehicles have flui~ or stowed ammunition.
fuel cells located in the engine companment or extemdly The relative hazards posed by mists or sprays of military
mounted, usually in tie rear. Fuel transfer lines that service mobility l%els depend upon the nature and severity of the

,,
0
the engine are often contained within the engine compart-
ment but must travel to the fuel cell. Auxilimy fuel lines ser-
vice smoke generators in the engine compartment or
ignition source, the fuel temperature relative to its flash
poin~ and the droplet size involved. In the case of spark
ignition, Fig. 2-5 illustrates that a mist or spray of a volatile
exhaust or small personnel heater units in the troop area. fiel, such as JP-4, can be ignited by sparks that are about an

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MIL-HDBK-684 :

TABLE 2-2. PENETRATOR OR JET TRAJECTORY, FUEL FO~ AND PRINIARY

IGNITION SOURCE /,
SITUATION \ OBJECTS ALONG TRAJECTORY IIFUEL FORM I PRIMARY IGNITION
SOURCE
1 Hull, Fuel Cell, Crew Compartment, Hull Spray Hull at jet exit
I spurt Spray fweball
2 Hull, Crew Compartment, Fuel Cell, Hull Spray Hull at jet entry
spurt Fuel cell at entry
3 Fuel Cell, Hull, Crew Compartment, Hull Spray Hull at both entry and exit
spurt Spray fireball
4 Hull, Crew Compartment, Hull, Fuel Cell Spray Hull at exit
spurt Hull at both entry and exit
5 Hull, Crew Compartment, Deck, Fuel Cell or Bilge, Hull Spray Deck
Sl)urt Deck

order of magnitude weaker than those required to ignite (one-horse~ower) electric auxiliary pump to provide power
mists of nonvolatile fuels, such as JP:8 or JP-5 (Ref. 10). for the gun@ret drive system during engine off and emer-
gency,operations.
2-3.3 HYDRAULIC FLUID The turret ammunition door actuation system employs a
Hydraulic power is transmitted by the pressure and flow linear actuator that is hydraulically decelerated at each end
of liquids. For many years petroleum oils were the most of the door Ipavel. The controls include a solenoid-operated
cormnon hydraulic fluids; however, use of synthetic fluids is @rectional livdve that is actuated by the loader’s knee
becoming widespread. Most hydraulic fluids used today are switch. A #ressure-compensated flow-control valve limits
flammable or at best “tire-resistant”. The term fire-resistant and contro~s the actuating speed of the door. Cross pilot-
can be misleading, however, and depends upon the state and operated check valves are used to lock the actuator and door
form of the fluid when subjected to an ignition source. Refer hydraulically.
to Chapter 3 for fluid properties. An accu$dator, precharged with nitrogen, supplements
the hydmuljc flow in excess of the system output for main
2-3.3.1 Locations gun deck clearance during rapid turret traversing.
The f@ctioning of combat vehicles is dependent on sus- A filter manifold and reservoir are fully integrated with
tained operation of all vehicuku subsystems. The vulnera- vehicle layout and ire readily accessible for ease of mainte-
bility of hydraulic systems is doubly critical because their nance. Falter elements require service only when self-con-
dhrnage cm lead not only to fires but to system and, there- tained differential pressure indicators pop out to alert the
fore, vehicular, failure. For example, hydraulic systems in crew visu~y of the maintenance requirements. Fluid is not
tanks provide power to operate the turret and the gun mech- spilled during filter changes because of built-in poppet
anisms, as well as other secondary functions such as the valves that stop incidental. flow. Quick disconnects are used
operation of magazine doors. The hydraulic fluid system for easy uncoupling of hydraulic lines to service compo-
schematic in Fig. 2-18 shows the hydraulic power supply nents or remove the engine. Tubing for the system is stain-
and distribution system for the gun elevation, turret direc- less steel, ~MIL-T-8808 (Ref. 32), a high-performance
tion, and the magazine door of the Ml tank (Ref. 31). tubing. Stainless steel ferrules are brazed on tubes, and
The M 1 hydraulic system provides 37 kW (50 horse- flareless-ty~ fittings conforming to military specifications
power) for the operating demands of the gun and turret are employed to provide reliable, leak-tight hydraulic con-
drive system and the turret munition door actuation sys- nections. “’
tem. The total capacity of the hydraulic system is 72, L (19 Thermal ‘stability of the system is maintained with the use
gal), which includes 68 L (18 gal) in the reservoir and 3.8 L of a simple’,tube-tinned crossflow heat exchanger, which is
(1 gal) in the lines. A variable-displacement, pressure-com- integrated with the vehicle cooling system. A shield is pro-
pensated pump is interfaced directly to the turbine engine vided to isolate the hydraulic reservoir from the crew.
accessory drive unit. This 11.03-h4Pa (1600-psig) pump is The main,. and auxiliary hydraulic systems provide the
electrically depressunzed during the engine starting cycle. gunhurret c/rwe and control systems with adequate powel
Hydraulic power redundancy is provided with a 746-W for all mission and emergency operations.

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MIL-HDBK-684

.-
O
,’

!,1
,.

I
‘-i%nita-”
I

I
--— -- —-- ~
i-
, b-----

Irr
*
.
.
.
.
b ---------

Emaxl

II y I
LA
P
[111

.
>
1
-

..-...6-------

R- ++

*,
●

I
✎
✌
✎

0
☛

w-
●
,

0 Figure 2-l& EIydraulic Power Supply and Distribution Ml MBT (Ref. 31)

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MIL-HDBK-684
NOTE: The following abbreviations are used in Fig. 2-18.
Acc = accumulator Brk Rtn = brake return MD = manual
.Amm = ammunition c1) = case drain depress
Assy = assembly EDV = electical repressurization ME = manual
AUXI-Iyd = auxiliary hydraulic valve elevate
BP = bilge pump HE = heat exchanger Press = pressure
LVDT = linear variable- Rtn = return
displacement transducer Servo = servovalve

2-3.3.2 Hazards “ 2-3.4.2 Hazards

Oral reports from members of the Israeli Defense Force The hazdrd presented by munitions is that they are
to US Army representatives after the Yom Kippur War extremely s~n:itive to ballistic impact or to fire. Munitions
(1973) disclosed the hazard to tank crewmen of burning usually coqrun components that either explode or bum
hydraulic fluid sprays following ballistic impact. The poten- when impac!ted. If rounds are perforated and the propellant
tial for this hazard was verified by tests conducted at is initiated, it is desirable that the explosion or hot gases and
Aberdeen Proving Ground (Ref. 33). debris not injure the crew. Stowage designs now exist that
will contain or direct away the fire, blast, and debris not
2-3.4 MUNITIONS only from de crew but also from adjacent ammunition.
In the design of future armored combat vehicles and the
2-4 SLOW-GROWTH FIRES
modifications to or update of older armored vehicles, con-
sideration must be given to the probability that these vehi- Slow-gro~th fires can be as destructive as rapid-growth
cles will be subjected to an overmatching tieat. This has fires. In fat{, a slow-growth fire can ignite and burn unde-
been true through history and will continue to be true in the tected for a ~onsiderable period before it grows to a confla-
future because of the rapid progress being made in the gration. M6st slow-growth fires in crew compartments,
designs of kinetic and chemical energy projectiles and of the however, C$ be detected in time for crew members to react
development of high-velocity and/or hypervelocity guns before exce$ive damage has been caused.
,
capable of defeating current defensive armor systems.
Means must be found, to enhance survivability, to simplify 2-4.1 IG~ITION SOURCES
repairability, and to promote future modifications. Modem 2-4.1.1 ~]ectricity
combat vehicles frequently carry a significant volume of Historically, electrical system failures have been a pri-
munitions, and much of this volume consists of propellants mary ignition source for slow-growth fires, particularly on
and may inciude explosives. Any rocket or smoke systems tracked ve~cles. Most electrical fires within the engine or
and propellants associated with the primary and often the the crew compartment, including the turret, we caused by
secondary weapon system munitions, have enough energy to elecrncal shorts and are maintenance or crew related. In
incapacitate the crew completely and destroy the vehicle. addition, almost all of these are related to some type of
The propellant presents a severe threat of explosion prima- material failure. In general, electrical fires involve both the
rilyfrom a deflagration of the propellant that can be followed metallic co~ductors and the insulating materials. Therefore,
by burning of other combustibles and finally detonation of particulm a~ention must be given to conditions that can
the high explosive. During World War 11,the Vietnam War, cause insulation degradation, excessive resistance heating
and the Arab-Israeli Wars, most irreparably damaged and arcing, Iand connector integrity and function failure.
armored combat vehicles revealed evidence of catastrophic Care must ~e taken to prevent sparking and arcing of elec-
fire. tric components, particularly in areas with potential leakage
of liquid flammables or in oxygen-rich areas that contain
2-3.4.1 hwtftims combustibles such as electrical insulation, fabrics, or other
AUthough ammunition stowage locations differ among potentially $kunrnable materials.
vehicles, small and large caliber ammunition stowage can The ope+ng of a mechanical switch or the mechanical
be found in almost every available area, including the ready breaking 0$ a current-carrying wire may cause an arc to
rack and bustle of the turret. Additional storage is provided jump across the separating conductors. This action could
in compartments or boxes attached to external surfaces. cause ignitiion of the insulation or of any combustible gas
Some survivability enhancement designs place cartridges in mixtures present. Even when protected, aIl elecrnc compo-
storage racks. Cartridges are spaced and shielding materials nents amdtires with sufficient energy to ignite flammables
are placed between the rounds to reduce the probability of should be considered potential ignition sources. Incandes-
blast and fragment initiation of propellant in contiguous cent carbon[wear particles, i.e., hot w-face ignition sources,
rounds. can be produced by brushes in electrical motors.

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,, 2-4.1.2 Hot Surfaces this point the reaction rates steadily increase. Additional

O The majorityof nonmunition-initiated fires in combat

vehicles occur in the engine compartment are started by hot
surface ignition, and are petroleum, oil, and Iubricams
heat is generated, part of which is absorbed by seIf-heating
and part of which is lost to the cooler surroundings through
convection and conduction. Since the rate of heat produc-
(POL) related. Since hot surfaces will exist on and within tion is an exponential fimction of temperature, whereas the
vehicles, care must be taken to reduce their potential as igai- rate of heat dissipation is substantially linear, the oxidation
tion sources for fires and explosions. process (depending on-surrounding conditions) can quickly
Even with very minor leakage during opetation or minor lead to temperatures that exceed the spontaneous ignition
spillage during maintenance, combustible masses can easily temperature of rhe residual carbon deposi~ This situation
form on or near hot surfaces by the gradual accumulation of may cause the particle irself to ignite, or if a combustible
solid residues produced by severe oxi&tion and decomposi- vapor is presen~ an immediate fire or explosion may resuk
tion of lubricating oils or hydraulic fluids. For example, a When the temperature reaches the kindling point of dry car-
thin film of almost any mineral oil exposed to air at atrn- bon, the deposits may start to glow and give off heaq which
spheric pressure at 149*C (300T) will reduce to a coke-like causes other pieces of carbon to smolder. Hoses or other
mass in a short time, and the process will accelerate with combustible materials in contact with or in the vicinity of
increased temperature and the presence of catalytic parti- these smoldering panicles may become involved. In some
cles, such as rum The accumulation of deposits, dus~ and cases the hot carbon deposits may break loose and become
debris on engine and component surfaces also progressively ignition soumes as they travel through or lodge in some
reduces local heat transfer so that ultimately, as the buildup other part of the engine compartment and thereby create
continues and the tempemture continues to rise, a potential either an immediate or impending hazard. If these incandes-
hot spot ignition source staiily develops. cent particles encounter a combustible mixture directly, an
immediate fire or explosion may occur. If the particles lodge
2-4.1S Exothermic Reactions in an oil-soaked ~ their heat may form and then ignite a
combustible mixture or they may experience sticient heat
Exotherrnic reactions, i.e., reactions that generate ha
transfer.to be temporarily cooled below the immediate dan-
can lead to fires and explosions in a rapid or long-term fash-
ger point. Further accumulations, however, wiIl increase the
ion. ‘llms the direct contact of potential exotherrnic reac-

0
!:, :
tants should be avoided. Care must be taken to prevent t%els
or other combustible fluids fkom leaking into munitions
compartments and from contacting reactive paints, plastics,
likelihood of a fire.

>4.2 COMBUSTIBLES
metals or other component materials &cause such contact 2-4.2.1 Fuel
cmdd promote smoldering or ignition. Fluid contamination The ignition and development of slow-growth fires may
and mixing should be. avoided to reduce the risk of fluid be categorized in terns of fuel type and the presence of
instab]dity, decomposition, or autoignition. Lubricant coexisting t%tmrnablematerials. The types of fuel subject to
decomposition (on hot surface-s)can lead to the formation of ignition as slow-growth fis include kerosene+pe mobfl-
carbon deposits, which, because they contain the ‘Lcatbod ity fuels, hydraulic fluids and lubricating oils, and Class A
oxygen complex”, can become highly exothermic, and once combustibles. Class A combustibles consist of materials
the exothetmic reaction is initiated, combustion of oil fllrns either stowed within the vehicle, such as paper or cloth
and/or carbon deposits can proceed rapidly. Even very small products, or used in its construction, such as electrical insu-
accumulations can become a problem because they can rap- lation and rubber-like elastomers. Such fires may be inia-
idly build in size in the pruence of oil vapors or mists. The ated by spontaneous ignition of con mmmated . Class A
process is self-perpetuating. As the accumulation grows, it combustibl~ by incendiary ballistic effects; by burning
further reduces heat conduction fimm the area while it engine fuel, lubricating oil, or hydraulic fluid, or by electri-
increases the surface area available for the capture of more cal malfunctions. Such slow-groti fires may lead to cata-
vapor so that the enlarged deposit quickly becomes oil strophic destntction of the vehicle as the fire spreads to
soaked. In this state, the liquid film temporarily retards oxi- other fuels and to stowed ammunition. The ignition of vehi-
&tion by reducing the amount of oxygen that can enter the cle parts made of a Class D combustible, i.e., combustible
deposi~ however, since convective cooling is also reduti metals, as described in par. 24.2.4, by incendiary ballistic
the temperature of the deposit gradually increases as it effects represents a separate type of slow-growth+ but highly
“dries out” by slow oxidation. Upon further decomposition sustained, fire.
a critical point is reached at which sufficient oxygen can Kerosene-type mobility fuels, hydraulic fluids, and lubn-
reenter the developing porous structure to allow oxidation ctwing oils may fuel slow-growth fues when spilled as
to continue at an ever-increasing rate. TM process repeats pools. Following ignition of a fuel pool, flame will spread
until the particle reaches a critical si= and temperature at across the liquid surface at a rate determined by the temper-
which more heat is produced than can be camied away. At ature of the fuel. This rate is about 20 mm/s (0.8 in.h) when

2-21
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d
),

!1

MIL-HDBK-684 !
the hydrocarbon liquid temperature is below the flash point. surface temperatures. Table 2-4 shows some typical values
The pool ahead of the advancing flame fron4 however, is for the hy~aulic fluids used in the flame propagation tests
warmed by convection and thermal radiation ffom the (Ref. 36). Itl is readily apparent that there are great differ- 9
flame, and as the liquid temperature approaches the flash ences in fl~h points among the various fluids. The flash
point, the flame speed increases rapidly and levels out at point is not ~ ~mportant flammability consideration in mist
about 1.25 rds (4.1 Ms) at temperatures above the flash ignition, bu$ It 1s a very important property that affects con-
point (Ref. 3). This difference in flame speed reflects the tinued burrung and flame propagation rates. It is important
difference between flame propagation where liquid vapor- to remember that if the system operating temperature is
ization is the controlling factor and flame propagation much over 100”C (2 12“F), the MIL-H-5606 (Ref. 37) and
where a preexisting vapor phase exists. MIL-H-6083 (Ref. 38) fluids would exhibit flame propaga-
The below-the-flash-point case represents one type of tion rates more near rapid growth than slow growth. In con-
slow-growth fire because the time required for the entire trast, at the same operating temperatures, MIL-H-83282
pool to become involved in the conflagration can be long (Ref. 39) and MJ.L-H-46170 (Ref. 40) fluids exhibit slow-
enough to allow crew action either to extinguish the fire or growth characteristics. Under these conditions, continued
to evacuate. Additionally, the rate of energy release in pool flame involvement may occur only as a result of wicking
fires is substantially slower than in vapor or mist deflagra- action. When wick burning occurs, the flame may or may
tions. Table 2-3 indicates how slow this burning rate is arrd not propaga~e from the flame source, depending on the sur-
shows the influence of temperature on the flame propaga- face temperature.
tion and the rate at which the pool surface drops as fueI is ;,.
consumed. 2-4.2.3 ~11 and Lubricants
The conventional Itrbncants used in diesel engines gener-
2-4.2.2 Hydratilc Fluids ally are formulated to meet the MJL-L-2104 (Ref. 41), MIL-
Flame spread rates of hydraulic fluids are controlled by L-9000 (Ref. 42) or MILL-46167 (Ref. 43) (rwctic)specifi-
chemical and physical characteristics of the fluid and the cations. In ~ese classes of lubricants, generally a base oil
systemic parameters, such as operating temperatures and will be blerided with antiotidants, antiwear additives, and

TABLE 2-3. FLAME PROPAGATION RATES IN FUELS AT VARIOUS TEMPERATURES

(Ref. 34 and 35) a
PROPAGATION RATE
CLOSED CUP FUEL ~PERATURE
ALONG SURFACE*, ALONG STRING”*, VERTICALt,
FUEL FLASH POINT, AT TEST START,
@s (in./s) mmfs (in./s) rnmh.in (in./rnin)
‘C (°F) “c (“F)
Jet A-1 45 (113) 24 (75) 33.0 (1.3) 6.1 (0.24)
J-P-5 63 (146) 24 (75) Did not propagate 4.3 (0.17)
DF-2 64 (148) 24 (75) Dld not propagate 3.6 (0.14)
Jet A-1 45 (113) 51 (125) 63.5 (2.5)
J-P-s 63 (146) 51 (125) Did not propagate
DF-2 64 (148) 51 (125) Did not propagate
Jet A-1 45 (113) 77 (170) Instantaneousjf
P-5. 63 (146) 77 (170) 63.5 (2.5) ~
DF-2 64 (148) 77 (170) 25.9 (1.02) ~
P-5 63 (146) 96 (205) 406.4 (16.0)1,
DF-2 64 (148) 96 (205) 25.4 (1.0)
AvGas Unknown unknown 6.0 (0.24)
J?.4 Unknown Unknown (, 5.0 (0.20)
JP-5 Unknown unknown 1 4.4 (0.17)
*Along the surfaceof fuel in a channel.See Ref. 34 for a descriptionof the test. ~
**Along ~fiel-wetted string. see Ref. 34 for a descriptionof the test.
~Verticalrate of drop of pool surfaceas fuelis consumed.SeeRef. 35.
~lToo fast to establishwith video. Probablyrate of flamefrontin vapor.The maximum&wnespeedthroughhydrocarbonfuel vaporin air is a
in a slightlyricherthan stoichiometricmixtureand is approximately400 rnrds (15.7ink).

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o
‘,, TABLE 2-4. INSPECTION DATA FOR SELECTED
(Ref. 36)
HYDRAULIC FLUIDS

mum VISCOSITY, VISCOSITY, FLASH

rnm2/s or cSt rnmz/s or diit POINT, POINT,
at 37.8°C at 99°C “c (T) “c@)
(1OO”F) (21(W)
MIL-H-5606m* 12.74 4.27 103 (217) 113 (235)
MIL-H-6083*m 13.43 3.86 102 (215) 113 (235)
MIL-H-83282Af 16.52 3.75 225 (437) 251 (483)
MIL-H-46170 15.85 3.62 244 (435) 244 (480)
Skydrol 300 11.73 3.89 193 (380) 207 (405)
(Phosphate Ester)
MS-5 (Silicone) 40.54 11.35 249 (480) 324 (615)
MIL-H-13919Bt 38.71 io.75 141 (285) 154 (3 10)
(Discontinued)
MIL-B=M176R 34.19 8.18 282 (540) 316 (600)
Source A
MIL-B-46176tt 16.63 4.79 252 (485) 271 (520)
Source B

AUTOIGNTITON AMERICAN POUR POINT”,

,.,,
,,
TEMPER.+TJMZ
‘c (T)
PETROLWM
INsT1-IUTE (API)
“c (“F)

0 GRAVITY AT
15.6°C (60°F)
MIL-H-5606”* 238 (460) 31.1 <-68 (-90)
MIL-H-6083** 238 (460) 33.0 <-68 (-90)
MIL-Ii-83282At 407 (765) 33.1 <-68 (-90)
MIL-H-46170 I 410 (770) 32.7 <48 (-90)
skydro~ 300 566 (1050) 1.6 <-68 (-90)
(Phosphate Ester)
MS-5 (Silicone) 363 (685) 1.09 <-66 (-87)
MIL-H-13919Bt 346 (655) 30.6 <-64 (-83)
(Discontinued)
MIL-B-46176ti 435 (815) 27.7 <-66 (-87)
Source A
MIL-B-46176H 396 (745) 30.8 <-67 (-87)
Source B
Whe “lessthan” symbol(c) meansthat tbe pourpoint is at a lowertemperamrethan that
Skown.
**Revisjonnumbernot -d
Wkwisionnumberin effect at time of propertydetermination
ttTesred prior to prodwxapproval,but metthe basic spedxation requirermms

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MIL-HDBK-684
detergent dispersants. The finished product is. normally a its electromotive series position, which is really a definition
very viscous-compared to fuels-fluid that operates in a of its chemical reactivity or chemical proclivity toward
very low-pressure environment and thereby produces only combining with other materials.
drips and leaks, which require an overwhelming ignition Uranimll becomes pyrophoric when finely divided,
source to sustain burning. Instances in recent years in which warmed, or ‘heated as a solid. When it is used as a projectile,
1.
oil leaks came in contact with heated surfaces resulted in the heat of ~fiction upon impact induces ignition. Uranium
sustained burning that was difficult to control with conven- is listed as a dangerous fire hazard in the form of a solid or
tional suppression systems. These fluids normally have a dust when exposed to heat or flame and is a moderate explo-
flash point in excess of 200”C (392”F) and ignite at surface sion hazarrl in the form of dust when exposed to flame (Ref.
temperatures in the 400 to 500°C (752 to 932”F) range. +4). It is also an alpha particle emitter, which makes the
Lubricating oil is not normally considered hazardous; how- material highly toxic when ingested.
ever, wick burning or heated surfaces readily act to ignite Lithium metal—used in high-power batteries-is less
leaks or spills of these fluids. At high operating tempera- reactive wi~ water and oxygen than the other alkali metals
tures the viscosity of lubricating oil becomes significantly (cesium, p,ptassium, rubidium, sodium, etc.) but forms
lower and thus renders the oil more hazadous. nitrides wi$ moist nitrogen unlike the other alkali metals.
When heated in air, lithium does bum and can bum vio-
2-4.2.4 Others lently. It reacts slowly with cold water and does not ignite
the liberated hydrogen. If the water is heated, the lithium
Slow-growth fires result from the ignition of plastics,
reacts more rapidly and generates enough hydrogen at a
elastomers, composites, wire insulations, pipe insulations,
high enough temperature to become explosive. Lithium is
paints, coatings, textiles, woods, books, jofials, manuals,
considered ~a dangerous fire hazard and would easily be
and certain metals. Ignition may occur from exposure to ignited by the kinetic energy of an impinging projectile, as
faster growth combustibles such X torching from fuels, would uraihun.
incendiruies, pyrotechnics, electrical shorts, explosives, Small aluminum particles will ignite and burn in atmos-
pyrophoric penetrators, or incendiary projectiles. Clothing, pheric uxygen (e.g., flash powder and nuclear flash simula-
span curtains, rags, texts, manuals, and other utilitarian tors), but lxger pieces or plates will not sustain combustion.
items including plastic canisters, paper or plastic dinner- If oxygen-$ch materials, such as propellants, however, are
ware, containers, fltid cells, and upholstery represent poten- burning very close to aluminum, they supply the heat and
tial slow-growth fire combustibles that are in close additional ~xygen required to sustain combustion of larger
proximity to personnel. Painted surfaces and composite pieces of aluminum. This fact was demonstrated by the
structures, such as fluid cells, bulkheads, storage compart- burning of the Hh4S Shej’jfeld during the Falkland Islands
ments, and decorative panels, pose a less proximate person- conflict. Siinilarly, iron filings and fine steel wool will bum
nel hazard. Electrical and refrigerant insulation, ductwork, in atmospheric oxygen, but larger pieces will not. (Fine steel
etc., pose even a lesser hazard. wool will ignite from a spark from a flint and steeL) Given
Hoses, insulation, and electrical jacketing located in and that these metals burn at very high temperatures, the pow-
around engine compartments are vulnerable to ignition by dered metals produced by a ballistic penetration are formi-
burning fuels from leaking or ruptured cells or lines ignited dable ignition sources, but the metals themselves nre not
by assault weapons, projectiles, incendiaries, explosives, or usually hwi$rdous combustibles.
electricid shorts. The kinetic energy of impacting projectiles on metals
Coatings and paints represent a minor source of fire haz- increases with the mass (linearly) and velocity (by the
ard but can be darnaged by exposure to heat and flame and square) of the projectile, and hence its ability to ignite tar-
can be instrumental in the spread of fires, as can clothing, gets increases accordingly. Magnesium and its alloys with
upholstery, etc. Coatings and paints, as well as most syn- aluminum we subject to ignition in air by impinging projec-
thetic materials, may produce toxic or noxious fumes when tiles; steelqlnormally are not. At elevated temperatures or in
they bum. an oxygen+enriched atmosphere, span from most target met-
Metals bum because they are powerful reducing agents, als ignites when impacted with sufficient kinetic energy.
and as a rule, they oxidize at room temperature to a limited Lithium, a@ninum, and magnesium in small particles are
degree, i.e., the outer exposed surface forms an oxide fairly vulnerable ~to ignition as elements in air. Uranium, pluto-
readily. This oxide layer, in turn, often protects the base nium, and~thorium, among others, are also vulnerable to
material from subsequent and continuous oxidation or cor- varied degiees.
rosion—a condition that depends upon the continuity of the Active metals, such as magnesium, ignite very easily and
oxide and the chemical potentkd of the metal below. Each bum very ~~pidly,whereas inactive metals, such as titanium,
metal has a specific chemical potential related, in a sense, to may or may not ignite and burn. Mercury and lead are very

2-24
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slow to reactj as are copper, goId, silver, and piatinum. 11. Presentation made by B. R. Wrigh4 Southwest

o
,$
These metals are virtually impossible to ignite and cannot
sustain combustion without the use of pure oxygen and very
high temperatures. ‘Iheir chemical potential is much lower
Research htitute, at US Army Belvoir Research,
Development and Engineering Center, Fort Belvoir,
VA 27 Jdy 1988.
than that of magnesium. IrI between active and inactive met- 12. R C. W-t and M. J. AstIe, E&., CRC Handbook qf
als are an assortment of materials that have their own inher- Chemistry and Physics, 61st Ed., CRC Press, Inc., Boca
ent chemical potential. An important consideration in Raton, 1% 17 March 1980.
addition to chemical potential is surface area. Almost aay 13. M. D. Kanakia and B. R. Wnghtj Fkmmability Char-
metal linely divided and exposed to a strong ignition source acteristics of Di-stifZare Fueir, BFLRF Interim Repofi
will burn explosively. whereas monolithic bulk metal is dif- No. 234, Belvoir Fuels and Lubricants Research Facil-
ficult to ignite arid would burn relatively slowly under nor- ity, Southwest Research Instimte, San Antonio, TX,
mal conditions. Surface are% mass, and chemical potential June 1987.
all figure signiikantly in the endothermic reaction required 14. J. M. Kuchm investigation of Fire and fipioswn Acci-
for ignition and in the exotherrnic reaction that is generated dents in the ChemicaL! Mining, and Fuel-Related hdus-
and dictates the rate at wtich the metal will burn and the tries-A ManuaL Bulletin No. 680, US Bureau of
amount of hat generated. Mines, Pittsburgh, PA, 1985.
15. I? l-i. Zabed, Gurglre Tests of Bell Helicopter Fuel Cell
REFERENCES
installation Vulnerability, Test Report 1560-75-91,
1. W. D. WeatherfortL Jr., US Army Helicopter Modijied Dynamic Sciences Divisiom Ukrasystems, Inc., Phoe-
Fuel Development Program-Review of Em.tdsi@d and nix, u May 1975.
Gelled Fuel Studies, AFLRL Repofi No. 69, US Amy 16. A. E. Finnerty and H. J. Schuclder, Igrution of Miliaz~
Fuek and Lubricants Research Laboratory, Southwest Fueir by Hot ParticLes, MR No. 244Z US Army Brdlis-
Research Institute, San Antonio, TX, 1975. tic Research Laboratory, Aberdeen Proving Gmmr@
2. Contributed by Dr. W. D. Weatherford, Jr., May 1988. MD, March 1975.
3. M. G. Zabetakis, Flammability Charac?etitics of Com- 17. Basic Considemtions in the Combustion of Hydrocar-

0
bustible ties and Vapors, Bulletin 627, US Bureau of bon Fuels With Aic Chapters III and W, NACA Report
Mines, Pittsburgh, PA, 1965. No. 1300, National Advisoty Committee for Aerospace,
4. J. M. Kuchta Fire and Erpiosion Manual for Aircrafi Washington, DC, 1957.
Accident hvestigarars, Technical Report No. AFAPL- 18. P. H. Zabel, S. A. Royal, B. L. Morns, J. F. Maguire,
TR-73-74, US Air Force Aero Propulsion Laboratory, and W. A. Mallow, Defeat of Armored Vehicles by Use
Wright-Patterson Air Force Base, OH, August 1973. of Fine, SWRI Repom 06-3193-001, Southwest
5. MIL-HDBK-1 14A, Fuels, Mobility, User Handbook, Research institute, San Antonio, TX, December 1990.
July 1990. 19. P. H. Zabel, Shaped-Charge Tut Pe@ormance of Fuel
6. G. G. Brown and R A. Badger, Brown-C&zt.s Vizpor T&for the Advanced Survivability Tm Bed Vehicles,
Pressure Chart for Hydrocarbons, University of Michi- SWRI Report 06-8899-003, Southwest Research Insti-
gan, Arm Arbor, MI, 1933. tute, San Antonio, TX, prepared for US Army Ballistic
7. Technical DaUI Book—Permleum Rejining, Chapter 5, Research Laboratory, Aberdeen Proving Groun& MD,
‘%por pressure”, 2nd Ed., American Petroleum Insti- February 1987.
tute, Washington, DC. 1970. 20. A. E. Cote and J. L. Linville, Eds., Fire Projection
8. R. W. Van Drdah et al., Revt”ew of Fire and Explosion Handbook, 16th Ed., National FR Protection Associ-
Hazards of Flight Vehicle Combustibles, Information ation,Qt.iincy,MA, 1986.
Circular 8137, US Bureau of Mines, Pittsburgh, PA, 21. P. H. Zabel and J. A. Weeks, Design to Enhance the
1963. Blast of a High-E.qpiosive Warhead, Paper presented at
9. G. A. E Godsave, “Studies on the Combustion of the 38th Annual Bomb and Warhead Technical Meet-
Drops in a Fuel Spray-The Burning of Single Drops ing, Albuquerque, NM, 18-19 May 1988.
of FueY, Proceedings of the Fourth International Sym- 22. P. H. Zabel, Feasibility Demonstration of Quari-Static
posium on Combustion, Williams and Wdlrins, Eds., Overpressun? Generation for Use in an Enhanced
Baltimore, MD, 1953, Combustion Institute, Pittsburgh, &ect Wahead, SWRI Repon 06-1204-001, Southwest
PA Research Institute, San Antonio, TX, March 1987.
10. Handbook of Aviation Fuel Properties, CRC Report 23. Letter Report, P. H. Zabel, Southwest Rewrch Insti-

0 ,.~,
No. 530, Coordinating Research Council, Inc., Atlan~
GA, 1983.
tute, to A.. E. F~erty, Ballistic Research Laboratory,
Subjecc Tests Performed to Quantify the Effectiveness

2-25
 Downloaded from http://www.everyspec.com

NML-HDBK-684 ,
of Fire-Suppressing Agents on Propellant Fires, SWRI Swmression
.. and Rescue Systems”, Basic Rehtionshins.
Project 06-7896, Southwest Research Institute, San in Military Fires, DoD-AGFSPS-75-4, Department of
Antonio, ‘IX, March 1984. Defense, Aircraft Ground Fire Suppression and Rescue 9
24. D. M. Potter and J. G. Garges, Final Repoti on Military Office, ~Wright-Patterson Air Force Base, OH, May
Potential Test of RPG-7 Weapon System, TECOM 1975. ~
Report No. DPS-2866, US tiy Test and Evaluation 36. B. R. $right, Discussion of Hydraulic Fluid Flamma-
Command, Aberdeen Proving Ground, MD, September bility l+~zards, Report No. AFLRL 95, Army Fuels and
1968. Lubricants Research Laboratory, Southwest Research
25. M. D. Kannkia and B. R. Wright, Investigation of Die- Institute, San Antonio, TX, December 1977.
sel Fuel Fire Vulnerability Parameters in Armored Per- 37. MIL-H~5606F, Hydraulic Fluid, Petroleum Base; Air-
sonnel Carriers due to Ballistic Penetration, Interim craft, M#sile, and Ordnance, August 1991.
Report No. AFLRL 194, US Army Fuels and Lubri- 38. MIL-H{6083E, Hydraulic Fluid, Petroleum Base, for
cants Research Laboratory, Southwest ‘“ResearchInsti- Presew and Operation, August 1986.
tute, San Antonio, TX, March 1985. 39. MIL-H{83282C, Hydraulic Fluid, Fire-Resistant, Syn-
26. P. H. Zabel, P. F. Piscopo, and L. E. Hendrickson, thetic Hydrocarbon Base, Aircraji, Metric, NATO Code
“Functioning/Malfunctioning of 23-rein Projectiles in Numbe! H-537, March 1986.
Aircraft Integral Fuel Tanks, Resulting Target Damage, II
40. MIL-1+46170B, Hydraulic Fluid, Rust-Inhibited, Fire-
and Relative Vulnerability of Neat and Modified JP-5 Resista~, Synthetic Hydrocarbon Base, August 1982.
Fuels”, Proceedings of the Symposium on Vulnerability
41. M’JL-L~2104E, Lubricating Oil, Internal Combustion
and Survivability of Su~ace and Aen”al Targets, Ameri- II
Engine(, Tactical Service, August 1988.
can Defense Preparedness Association, Washington,
IX, 1975. 42. MIL-L~9000H, Lubricating. Oil, Shipboard Internul
Combustion Engine, High Output Diesel, September
27. “RPO-A Flamethrower: Artillery for the Soviet Sol-
1987. ‘
dier;’ Jane’s Defence Weekly 5, No. 20,934-5 (24 May
1986). 43, MIL-L~46 167B, Lubricating Oil, Internal Combustion
Engine; Arctic, June 1989.
28, T. Gander, “Infantry Equipment Update+3chrnel Fuel-
Air Weapon Revealed”, Jane’s Defence Weekly 18, No. 44, N. I. Sax, Dangerous Properties of Industrial Materi-
18, 24(3 1 October 1992). als, 4+ Ed., Van Nostrand Reinhold Company, New @
York, NY, 1975.
29. Y. Bodansky, “Soviets Use Afghanistan to Test ‘Liquid ,
Fire’”, Jane’s Defence Weekly 1, No. 20, 819 (26 May
1984). BIBLIOGRAPHY
30. Y. Bodansky, “New Weapons in Afghanistan”, Jane’s J. W. Beach, Cost and Effectiveness of Alternate
Defence Weekly 3, No. 10, 412(9 March 1985). Approaches to Dieselization of the M113 Armored Per-
31. P. A. Specht and J. Feeney, MIA1 Tank Cbracterisrics sonnel C$rn”er(U), Appendix A (U), AMS&4 Technical
iznd Description Book, NP-86- 13098-002, General Memorar+dum No. 38, US Army Materiel Systems Anal-
Dynamics Land Systems, Center Line, MI, for Project ysis Ac$vity, Aberdeen Proving Ground, MD, August
Manager for Abrahms Tank System, Armored Systems 1969, (THIS DOCUMENT IS CLASSIFIED CONFI-
Modernization, Warren MI, November 1991. DENTIAL.).
32. MIL-T-8808B, Tubing, Steel, Corrosion-Resistant (18- F. Campbell, Noncombat Fires in Army Vehicles, AMSAA
8 Stabilized), Aircraji Hydraulic Quality, 8 April 1981. Technic+ Report No. 349, US Army Materiel Systems
33. A: E. Finnerty, R. R. Meissner, and A. Copekmd, Frag- Analysis’, Activity, Aberdeen Proving Ground, MD,
ment Attack on Ground Vehicle Hydraulic Lines, BRL March 1~82.
Technical Report No. 2661, US Army Ballistic P. Carell, The Foxes of the Desert, Translated from the Ger-
Research Laboratory, Aberdeen Proving Ground, MD, man by M. Savill, Bantam Books, Toronto, Canada, and
July ’1985. New York, NY, 1960.
34. B. R. Wright, Comparative Flammability Testing, of Jel M. Carroll: Vehicle/Crew Survivability in Fuel System
A-1, JP-5, and DF-2, Letter Report No. BFLRF-90-003 Fires, ~SAA Interim Note No. 3, US Army ,Materiel
(Revised), US Army Belvoir Fuels and Lubricants Systems ~Analysis Activity, Aberdeen Proving Ground,
Research Facility, Southwest Research Institute, San MD, Se@ember 1976.
@onio, TX, April 1991. Also conversation between P. GEN. J. M! Gavin, On to Berlin, Bantam Books, New York,
H. Zabel and B. R. Wright of Southwest Research Insti-
tute, 1 December 1992.
35. R. S. Alger and E. L. Capner, “Aircraft Ground Fire
NY, 197$.
W. D. Wea~erford, Jr., et al., Research on Fire-Resistant
Diesel Fuel, AFLRL Report No. 145, US Army Fuels and
a
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MIL-I-IDBK-684
Lubricants Research Laboratory, Southwest Research Bernard R. WrighL Discussion of Hydraulic Fluid Flanuna-

o lnstitute, San Antonio, TX, December 1981.

W. D. Weadterfor& Jr., Report on MicroenuiLsion-T~e Fire-
ReszM.um Fuel, AFLRL Report No. 191, US &my Fuels
biiiry Haamo!r, AFLRL Report No. 9.5, US &my Fuels
and Lubricants Research Laboratory, Southwest Research
Institute, San Antonio, TX, December 1977.
and Lubricants Research Laborato~, Southwest Research F. H. Zabel, Test Program w Demonstrate Enhuruxd Surviv-
Institute, San Antonio, ‘IX, December 19$4. ability of Armored Aluminum Vehicle Fuel System to
W. D. WeatherfcIrd, Jr., and D. W. Naegeli, “Study of Pool Shuped-Chaqe Attack, SWRI Repmt 06-8899-001,
Burning Self-Extinguishment Mechanisms in Aqueous Southwest Research Institute, San Antonio, TXj July
Diesel Fuel Microemulsions”, Journal of Dispersion Sci- 1986.
ence and Technology 5 (1984). MIL-I%DBK-118, Design GuideforMilit.ary Applications of
W. D. Weatherford, Jr., et cd., Army Fire-Resistant Diesel Hydraulic Fluids, 22 September 1993.
FueL SAE T@bnicai Paper No. 790925, Society of Aut+ TM-E 30-451, Handbook on German Military Foxes, War
motive Engineers, Warrendale, PA, October 1979. Department, 15 March 1945.
W. D. WeatherfOrd, Jr., et al., Development of Amy Fire- Hydraulic System Vulnerability Reduction, Report No. 79-
Resistant Diesel Fuel, AFLRL Report No. 111, US Amy AF- 1, Fluid Power Research Center, Oklahoma State
Fuels and Lubricants Research Laboratory, Southwest University, Stillwater, OiL 31 July 1979.
Research Institute, San Antonio, TX, December 1979.

0,,

,,,.
0
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MIL+IDBK-684

o CHAPTER 3
MAT+lmIALs Am HAZARDS
Cornbustdde materials located within or on combat vehicles ore described The propem”es of the materials that relate to
ignition and su.smined combustion are presemed I&ads resultin.gj?om the combm”on of these materials are described

>1 INTRODUCTION properties, such as energy content (heating value), vapor

This chapter provides detailed descriptions of the com- pressure, viscosity, pour poin4 melting poin~ and density,
bustible materials located witi or on combat vehicles, lhe vmy with the type and size of hydrocarbon molecules.
properties of each combustible material that affect ignition Therefore, such properties of a mobility fuel maybe tailored
and sustained combustion are presented. The hamrds pre- by the appropriate hydrocarbon compositional adjustments.
sented by eaeh combustible material are also presented. Further examples of engine+erformartce-related hydro-
Flammability characteristics, which are peculiar to a given carbon composition tailoring of fuels are provided by com-
matexial, am de--bed. The conditions under which the position adjustments made to optimim pumpability and
combustibility of these materials is affected are described. filterability in low-temperature appl.ieations, to minimin
The combustible materials described are carbon deposition, to assure adequate fuel vapor for igni-
1. Mobility fitels, such as diesel fuel, turbine fuel, and tion, and to minimize evaporation losses.
gasoline Several fuel-related fictors govern the nature and extent
2. Hydraulic fluids of the hazards with regard to fire safety and sumivability. b
3. Other petroleum products, oils, and lubricants a particular fire exposure situation, the physical, cttemieal,
4. Munitions and flammability properties of the fuel, the quantity of fbel,
5. Other combustibles such as electric wiring insula- the fuel environmental conditions, and the extent of
tion, .@] and miiation liners, seats, on-vehicle eq,uipmem involvement with other combustible materials are impor-

0
,, (OVE), paints and coatings, and miscellaneous combusti-
bles including plastics and elastomers, textiles, and other
items that can bum.
tant. Such factors determine whether the resulting fire
develops slowly or rapidly and whether it remains trivial or
becomes catastrophic,
In addition to performance requirements, logistics and
3-2 MOBILITY FUELS safety requirements may be considered in the selection of
Mlitary mobilig fuels are derived from petroleum and the mobility fltels to be used in combat vehicles. As the tem-
comprise complex mixtures of indefinite numbers of hydro- perature of a liquid fiel-such as jet propellant (JP)-S, die-
carbon molecules. Differences among the various fuels are sel fuel (DF)-2, DF- 1, or DF-A—increases, the vapor
~om the composition (hydrocarbon type and size) of the pressure increases until it eventually corresponds to the
constituent molecules. In general, these fuels are distin- lean-limit composition of fuel vapor in air at the theoretical
guished by distillation characteristics, such as initial boiling fiash point of the specific fuel. his fact is shown for United
point (IBP), boiling point distribution vema percent dis- States (US) military fuels in Fig. 2-2 and described in sub-
tilled, and final boiling poin~ i.e., endpoint @P) (Ref. 1). par. 2-2.1.1. At the flash poing vapor above the surf= of
Specific fuels are additionally defined by other properties the bulk liquid ignites when subjected to an adequate igni-
required bytheend application of the fitel. For example, tbe tion source. On the other hand, if the liquid fuel is dispersed
chemical structure of the hydroeatbon molectdes present in as a spray (or mist), the dispersion can achieve ignition at
spark-ignition engine fuels is significantly different fforn lower than flash point temperatures if sticient ignition
those present in diesel engine fuels. This difference is energy is provid~ as is indicated in Fig. 2-5. At temperat-
required to assure optimum ignition quality since spark- ures above the flash poin; the liquid surface is covered
ignition engines require fiel-ignition properties essentially with enough fuel vapor to generate a flammable mixture
opposite those required by the compression-ignition mecha- with air. Temperatures substantially above the flash poin~
nisms of diesel engines. however, are required to generate enough vapors to form a
As an additional illustration, a very important property of mixture that is too fuel rich to sustain combustion. In the
turbine engine fitels is the amount of thermal radiation emit- case of the gasoline-type fuels, e.g., motor gasoline
ted during their combustion since this radiation is detriuten- (MOGAS) and JP-4, within a small, conlined space (the
tal to the turbine engine parts. Consequently, turbine fuels ullage of a fuel cell), sufficient vapor pressure may exist at
should not contain substantial quantities of hydrocarbon temperatures below the normal operating temperature to
moleeules that produce excessive thermal radiation. Other exceed the rich limit of flammability (Ref. 2). Designers

3-1
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IWL-HDBK-684
cannot, however, rely upon this fact to provide fire protec- the continental United States (OCONUS). The CONUS
tion because dilution with air at the outer edge of the fuel grade’ has ~a minimum flash point of 51.7°C (125°F),
vapor provides a combustible mixture. whereas the OCONUS grade has a minimum flash point of a
The foregoing discussion illustrates the need for knowl- 56°C (133°F). Thus DF-2 obtained in the U.S. can ignite at
edge of the fuel properties, most of which are described in a slightly $wer temperature than can the DF-2 obtained
Ref. 3, to assure successful use of military mobility fuels. In elsewhere. ~F-2 has a higher minimum flash point than JP-
addition, such knowledge is quite important to optimizing 8 (38°C (10~F)) and is less volatile.
vehicle fire survivability (Refs. 4 and 5).
In 1987 the Department of Defense (DoD) initiated 3-2.2 Dti-1 WINTER-GRADE DIESEL
implementation of a “one fuel forward” concept, which ENGINE FUEL
involves the tise of a single fuel in diesel-fuel-consuming DF- 1 diesel fuel is intended for use at ambient tempera-
and turbine-fuel-consuming ground equipment and aircraft. tures as low as –32°C (–25.6°F).
Preceding this action, US aircraft in Europe had been con- The pro@ties of DF- 1 are defined by Federal Speci6ca-
verted, from JP-4 to JP-8. The North Atlantic Treaty Organi- tion W-F-800 (Ref. 6). Properties related to ignition and
zation (NATO) allies have concurred with this concept; combustion are summarized in ‘I’able 3-1. Data in Ref. 7
therefore, diesel engines being constructed in the future indicate th~t commercial diesel 1-D should meet the fiash
must be able to operate on JP-5 and JP-8 as well as DF-2. point req+ for either DF- 1 or DF-A.
JP-5 meets DF-2 requirements for flash point and has been
used successfully in both diesel and turbine engines. JP-8 3-2.3 Dl$A ARCTIC DIESEL ENGINE FUEL
has a flash point equal to that of DF-1 and DE-A and is an
Arctic diesel fuel, as its name implies, is intended to be
efficient diesel fuel, but it has other characteristics to meet
used to power diesel engines in arctic-type frigid environ-
aviation needs. At the time this handbook was written, all
ments. DF-~ has the same flash point as DF- 1 and JP-8.
US Army and US Air Force organizations assigned to
The pro$rties of DF-A are defined by Federal Specifica-
NATO had converted to JP-8, and US Army organizations
tion W-F-800. There is enough overlap in the specifica-
in the continental United States were in the process of con-
tions for DF-A and DF- 1 for a given lot of diesel fuel to
verting from DF-2 to JP-8.
meet both ~ade requirements. Because there is so little use
The propefies described are those related to the potential
of DF-A, tlfme is Mtle likelihood that a refinery would make
for ignition and those that would be used to establish the
a special production run of a diesel fuel that would meet a
effects of fire. The two parameters by which the flammabil-
DF-A requ~ements but not DF- 1 requirements. Therefore,
ity of liquids can be determined .me the flash point and the
combat vedcle designers should assume that DF-A and DF-
initial boiling temperature. These will be described and
1 would re!ict similarly as far as fire survivability is con-
related to those of JP-8. The other pamrneters of interest rel-
cerned.
evant to fire are the fire point, autoignition temperature, vis- I
cosity, heat of combustion, thermal conductivity, specific
3-2.4 Jd:8 KEROSENE-TYPE AVIATION TUR-
heat, density, and vapor pressure versus temperature.
BIifE ENGINE FUEL
3-2.1 Dl?-2: DIESEL FUEL JP-8, per,:MIL-T-83 133 (Ref. 14), is a kerosene-type avia-
Diesel fuel is used in compression-ignition engines. DF-2 tion turbine!engine fuel that has replaced JP-4 in combat air-
is normally used where “cold-starting and cold-fuel handling craft and is replacing diesel fuels-DF-2, DF- 1, and DF-
are not severe problems. It is intended for use in all automo- A—in ground combat and tactical vehicles in NATO areas.
tive high-speed diesel engines and in medium-speed appli- JP-8 is functionally the same as Jet A- l—the fuel used by
cations in areas in which the ambient temperatures are commercial aircraft worldwide; however, JP-8 has some
above -1 8°C (O°F). icing-, corrosion-, and static-inhibiting additives that Jet A-
The properties of DF-2 are defined in Federal Specifica- 1 lacks. JP-8 has a higher minimum flash point than JP-4
tion W-F-800, Fuel Oil, Diesel (Ref. 6). Typical properties and a lower minimum flash point than DF-2, but these
pertinent to flammability and combustion obtained from points are essentially the same as those for DF- 1 and DF-A.
tests are summarized in Table 3-1. DF-2 is not as volatile as DF-1 or D~-A is no longer needed in NATO areas in winter
gasoline at normal room* temperatures, but when heated to or in the afctic because JP-8 meets the winter and tictic
or above its flash point, DF-2 can be as Ikn.mable as gaso- requiremen~s (Refs. 6 and 15). The initial boiling point of
line (Ref. 5). 91 sarnplesiof JP-8, supplied by 15 sources worldwide, was
DF-2 comes in two grades: the first is for the continental 144°C (29~°F) minimum, 174°C (345”F) maximum, with a
United States (CONUS)** and the second is for use outside 157.5°C(316°F) average (Ref. 15). Pertinent properties and
flammability characteristics are tabulated in Table 3-2.
*The temperaturemost often used for the designof air-condition- JP-8 is specified as having a specific gravity between
ing equipmentas the most comfortableset point is 24°C (75”F). 0.775 and $840 and a minimum net heat of combustion of a
**~e continent~ I_JtitedStates includesAlaskaand Hawaii. 42.8 MJ/kg. (A typical sample of DF-2 was tested and

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MIL-HDBK-684

TABLE 3-1. DIESEL FUEL P~TERS FROM TESTS (R& 7-13)

MILITARY COMMERCIAL
PROPERTY DF- 1 I DF-2 I DF-2 GR4DE 1-D GRADE 2-D
CONUS OCONUS
Spcific Gravity 0.8338 0.8493 0.845 0.811-0.825 0.863-0.865
at 15°C (6Q’’F),dimensionless
Flash poink 66 (150) 70 (158) 66 (151)
‘c (W)
Fire Point 115 (235)
“c (1=)
Kinematic Viscosity
at 40°C (104T),
mm2fsorcSt
Net Heat of Combustion
L86

42.556 (18,295)
2.5-3.1
1.22 @ 100”C (212*F)

42.556
3.2

T
at 4o”c (KJ&l?), (18,295-18,450)
MJK_kg-”Cl(13nd(Ibrn0F))
Thermal Conductivity 0.09205 0.07699
at 40”C (104”F),
W/{m.°C)
Specific Heat, 2134 2259
J/(kg.°C)
Autoignition Temperature 250 A 3 (482 A 5)
Vapor in Air, “C (“F)
Latent Heat of Vaporization, 203 258
J/kg
Autoigriition Temperature 649 *17 (1200*25)
Hot Manifol~ ‘C (~
Distillation IBP, 188 (370) 188 (370)
“c (“F)
Distillation 10%, 214 (417) 214 (417)
“c (T)
Distillation 50%, 238 (461) 258 (496) 281 (538)
“c (“F) (425-438) I (513-520)
Distillation 90%, 314 (598) 314 (598) 340 (644) 249-255 I 315-321
‘c (“q
Distillation EP, 343 (650) 343 (650) 370 (698)
“c (“F)
Cetane Number, 44 44 47
dimensionless

found to have a specific gmvity of 0.8577 and a net heat of ranks (MBTs), Bradley fighting vehicles (BFVs), M113A3
combustion of 42.305 M.J/kg.) Therefore, concern has been armored personnel carriers (APCs), M88 tracked recovery
expressed that there is an energy per unit volume decrease vehicles (TRVs), and tactical and administrative vehicles,
of apprcmimately 4% for JP-8 versus DF-2, which may only the M88 TRV continued to exhibit degraded perfor-
result in slower acceleration, less available power, and mance with JP-8, and this performance was deemed to be
shorter travel range for the vehicle when JP-8 is used. Both vehicle-peculiar (Ref. 27).
labmatory and field tests, as well as experiences in South- JP-8 has another failing relative to DF-2: It cannot pro-
west Asia (SWA), have shown that either the fuel metering duce smoke fkom the vehicle engine exhaust smoke system
system will automatically adjust or can be adjusted for the (VEESS). The smoke results when the larger molecules of
differences in the fiels to provide the power needed. “Ilwre high boiling point fluids form mist droplets. Note on Fig.
can be a slight loss in vehicle acceleration, and there proba- 3-1 that fog oil and DF-2 have greater portions of high
bly will be a loss in the travel dismnce (Refs. 20-26). Of the boiling point fluids (the larger or heavier molecules) than
vehicles test@ which included the Ml and M60 main battle does JP-4, JP-8, or Jet A- 1. For this reason, combat vehi-

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,,

TABLE 3-2. AIRCRAFI’ TURBINE FUEL PARAMETERS FROM TEST (I&&. 9-13 and 15-19)
PROPERTY AT FUEL
“C (“F) JP-4 JP-5 JP-8 JET A JET A-1 KEROSENE AV GAS AV GAS

Specific Gravity,
dimensionless
Flai.h Point,
‘C ~F)
1S“c
(60”F)
0.762-0.78

–18
(o)
0.817-0.83

62-66
(144-150)
0.800-0.819

45.6-46
(114-115)
0.805-0.816

41-60
(105-140)
0.805

43-54
(109- 130)
0.8~0.83

50-52
(122-125)
T
100-130 115-145
-0.7

(x)
Fire Point,
“C (“F) (:;0) (::5) +
Autoignition 229-246 224-248- 224-240- 224-238 250k3”” 149
Temperature (AIT) (445-475) (435-478) (435-465) (435-460) (482 k 5) (480)
Vapor in Air, ‘C (“F)
AIT Liquid Stream, 704 704 649 649+ 14
‘c (W) (1300) (1300) (1200) (1200 + 25) I

Kinematic Viscosity, -20 (-4) 5.75-5.84 4.09 5.58 1.48 I

mm2/s or cSt 40 (104) 1.50 1.10-1.25 1.07-1.21 I
70 (158) 1,02 0,88 0.77-1.04 I

100 (212) 0.58

Net Heat of Combustion, 42.8-43.5 42.6-43.0 42.5-43.0 42.8-43.3 42.7-43.1 43.2 44.2 I
MJ/(kg.°C) (Btu/(lbm.°F)) (18,412-18,723) (18,312-18,514) (18,325-1 8,506) (18,412-1 8,628) (18,377-1 8,508) (18,000) (19,000)
Thermal Conductivity,
W/(m”C) [Btu/(fth°F)]
Specific Heat,
J/(kg”C) [Btu/(lbm°F)]
-=Latent=Heat=of=-
Vaporization,
J/kg, (Btu/lbm)
.:=
40°c
(104°)
40”C
(104°)
2 -====-
0.1364
(0.0788)
0.0946
(0.05467)
1715.4
(0.41)
- =:===0:0207-2---.-==
(48.16)
-- --- =-= --
I0.1364
(0.0788)

-.

T
Vapor Pressure, 16°C 8.96 19.99
kpa (lb/in?) (60°F) (1.3] (2.9)
Distillation IBP, 180 150-157.5 163 149-167 177
‘C (“F) (f;8) (356) (305-3 16) (325) (300-333) (350)
Distillation 10%, 90-99 193-196 176-188 192 170-173 193-196
“c (W) (194-210) (380-385) (359-370) (377) (338-343) (380-385)
Distillation 50’%, 143 212-215 200-209 203 194-196 221

z
“C (“F) (289) (414-419) (392-426) (397) (381-385) (430)
Distillation 90%, 199-209 238-242 235-256 247-249 228-234 254 116
“C (“F) (390-409) (460-468) (456-493) (476-480) (442-453) (490) (240)
Distillation EP, 261 258-284 271 247-276 274 159
“C (“F) (502) (496-543) (520) (477-529) (525) (3 19)
Cetane Number, 23 42 45 45.0-49.1
dimensionless
 Downloaded from http://www.everyspec.com

o
1oo-
(A) JP4
80 -
60 -
40 -
20 -
0
1 9

100 “
60 “ (B) JP-8
60 -
40 “
20
0

100“ (C) Jet A-1

80 -
60 “
40 -
20 -

0
100 r
(0) OF-2

100“
Fog 01
60 “

60 -
40 -
20 “

50 100 200 300 400 500

Temperature, ‘C

Fi 3-1. ~ical Chromatogmph D@ation Traces of JP4, J% Jet A-1, DF-2, ad F% on

(I&& 13 and 19)

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MIL-HDBK-684
cles using JP-8, Jet A-1, or Jet A fuel will have to carry fog combustible vapor layer should form over JP-8 at a lower
oil. There is more information on fog oil and the VEESS in temperature than it does over JP-5. The average flash point
Ref. 28 and par. 3-4.3. Jet Aand Jet A-1 aremade to the of JP-5 is 162°C (144”F), whereas that of JP-8 is 46°C @
same specification and have the same properties except for (115°F), wkch indicates that JP-8 vapor would ignite at a
the maximum freezing point, which is -40°C for Jet A and lower temperature than would JP-5 vapor. The average heat
-47°C for Jet A- 1. of combushon of JP-5 is 42.929 MJ/kg (18,456 Wu/lbm),
JP-8 is procured per military specification MIL-T-83 133. whereas tit$ of W-8 is 43.019 MJ/kg (18,495 Btu/lbm). It
The alternate fuel for JP-8 is Jet A- 1, which is described in can be assumed that there is no essential difference in the
American Society for Testing and Materials Standard heat output of these two fuels.
ASTM D 1655 (Ref. 29). Note on Fig. 3-1 that the samples
of JP-8 and Jet A-1 show similar ,temperature ranges and 3-2.5.3 Automotive Gasoline
therefore are from the same “narrow cut” of hydrocarbon Gasoline is a multicomponent blend of petroleum-
fuels. This alternate fuel was used in the 1991 operations in derived hyckocarbons with appropriate additives and is used
SWA (Ref. 11). In SWA some organizations using Jet A-1 in in spark-ignition engines. Several grades are formulated
lieu of DF-2 complained of Iack of lubricity. In JP-8 lubric- with different antiknock indices. Volatility is established
ity is supplied by one of three additives used to convert Jet during pro~ction to obtain gasoline in five classes; gaso-
A-1 to JP-8; this lubricity-adding material is a dimenc line is processed by US refineries in the appropriate volatil-
organic acid, usually dilinoleaic acid, which is intended to ity class fo~ the geographic location and the month of use.
provide an anticorrosion feature.
The US ~y uses three specifications for procuring gaso-
3-2.5 OTHER FUELS line: AS~ D 4814 (Ref. 31), MJL-G-3056 (Ref. 32), and
MIL-G-53~06 (Ref. 33). In 1959 the US Army started con-
3-2.5.1 W-4 Gasoline-me Aviation l’brbine
verting to diesel fuel from gasoline for ground combat vehi-
Engine Fuel cles. Now +e primary use of gasoline by the US Army is for
JP-4 is a gasoline-type fuel comprised of mixtures of gas- passenger aider administrative automobiles.
oline and kerosene and is used as a jet engine fuel in mili- Commer@ automotive gasoline is procured under
tary aircraft. The properties of JP-4 are defined in Military ASTM D 4814, and there are five volatility classes for both
Specification MIL-T-5624, Turbine Fuel, Aviation Grades leaded and ~unleaded blends of neat gasoline or blends of
JP-4, JP-5, and JP-51JP-8 St (Ref. 30). Its pertinent proper- gasolines ~d oxygenates (gasohol), such as alcohols or 4
ties are summarized in Table 3-2. methyl tertrbutyl ether, for use in CONUS. Commercial
JP-4 exhibits significant vapor pressure but not as much gasoline is usually available in one antiknock index for
as MOGAS, and it contains heavier hydrocarbons than leaded and ithree antiknock indices for unleaded gasolines.
MOGAS, which cause slower overall evaporation rates. In
The propefies of gasoline vary according to classes and
gasoline-type fuels sufficient vapor pressure exists at sub- indices, w~ch are selected for geographic location and cli-
room temperatures to exceed the rich hm.it of flammability.
mate.
The flash point of JP-4 is not specified in MILT-5624, but
Gasolinelfor combat automotive vehicles can be procured
tests of W-4 samples, indicate that a flash point of approxi-
according to MJL-G-3056 for OCONUS use. Two types of
mately -18°C (O°F) can be expected. This flash point is sig-
unleaded gh.soline are procured under this specification:
nificantly lower than that of W-8. JP-4 has a marginal
Type I is ~ all-purpose gasoIine that meets NATO Code
cetane number; 23 is a typical value. Therefore, it is used
No. F-461 ~d Type 11is a low-temperature, all-purpose gas-
only as an emergency fuel in compression-ignition engines.
oline. lhs gasoline is intended for use in automotive, sta-
3-2.5.2 m-5 High-Flash-Point, Kerosene-’&pe tionary, and marine spark-ignition engines; vehicle and
Aviation Turbine Engine Fuel personnel heaters; and cooking units. This gasoline is
notto be used within CONUS.
W-5 fuel is intended for use in naval aircraft because vol-
Selected ~roperties of aviation gasoline are given in Table
atile fumes of lower flash point fuels could pose a flamma-
3-2. In general, gasoline is much more volatile at lower tem-
bility hazard in shipboard applications, specifically aircraft
peratures t@n diesel fuels or JP-8 and could form combusti-
carriers and helicopter-bearing ships.
The properties of JP-5 are delined by Military Specifica- ble fuel-air ~~tures at relatively low ambient temperatures.
tion MILT-5624 (Ref. 30). Typical properties are sma- ~s vdneqability of gasoline-fueled vehicles is the princi-
rized on Table 3-2. JP-5 is within the distillation patterns of pal reason gasoline has been removed from use by the US
JP-8 and Jet A-1 on Fig. 3-1; therefore, JP-5 would not pro- Army.
duce smoke using the VEESS.
Evaluation of data in Ref. 15, which is based upon evalu- 3-2.5.4 Gasohol
ation of flash points of 63 samples from 15 sources, indi- Gasohol !‘Ma blend of gasoline and 10% by volume of 9
cates that W-5 should ignite less readily than JP-8. Thus a denatured ethyl alcohol. Leaded or unleaded automotive

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MIL-HL)BK-684
gasohol is procured per ASTM D 4814 or MIL-G53006 3-2.5.6 Foreign Diesel Fuels
(I&f. 33). Gasohol is supplied in five volatility ckasses, five 3-2.5.6.1 NATO Diesel Fud F-54
water miscibility classes, and 14 different antiknock grades. The principal foreign diesel fuel used by the US Army is
‘Ibe volatility and water miscibility classes are selected as NA~ diesel fuel F-54, which is analogous to DF-2 (OCO-
fimctions of the month and geographic location of use. The NUS). NA~ F-54 has a miniium flash point of 56°C
antiknock index is selected by the procuring agency from (133°F). DF-2 (OCONUS), intended for entry into the Cen-
six levels of limited grade, six levels of regular grade, or tral European Pipeline System, has a minimum flash point
two levels of premium grade gasohol. T%eprocuring agency of 58eC (136’W).
also selects whether the gasohol will be leaded or unleaded. The properties of NATO F-54 are defined by NA3U Stan-
dardizahonAgreement (STANAG) 2754. Pertinent proper-
3-2.S.5 Commercial Diesel Fuels ties are equivalent to OCONUS DF-2 in Table 3-1. NATO
‘Ihe properties of commercial diesel fuels are defied by fiel codes are given in Table 3-3.
ASTM D 975, Sumdarri Spec@caa”on for Diesel Fuel Oils
Ref. 34). Pertinent properties are summarized in Table 3-1. 3-2.5.62 Russian Diesel Fuels
Note that both of rhe commercial diesel fuels listed-1-D The requirements for diesel fuels meeting Russian Speci-
and 2-D-have higher flash points than the minimum for fication GOST 305-82 are shown in Table 3-4. ‘I%eRussians
JP-8.
TWLE 3-3. NATO FUEL DESIGNATIONS AND US EQUIVALENT
SPECIFICATIOWSTANMRDS (Ref. 12)
NATO INDUSTRY
CODE NATO MILITARY/FEDEW4L EQUIVALENT
NO. SPECIFICATION STANDARD
F-18 Gasoline, Aviation, Gmde 100/130 ASTM D 910 Aviation Gasoline ASTM D 910 Aviation
Gasoline
F46 GasoiinG Auto, Military (91 RONj — —
F-57 GasOlin% Auto, Low Lead (98 RON) STANAG 2845 CEN EN-228
o F-67 Gasolin% Auto, Unleaded (95 RON) STANAG 2845 cm EN-228
— — \ ASTMD4814 S-I Engine Fuel ~ASTM D 4814 S-I
I ~Enfine Fuel
— — MIL-G-53006 Gasohol —
— — MIL-G3056 Gasoline —
F-40 Turbine Fuel, Aviation, WideCut Type MIL-T-5624 Turbine Fuel, Aviation, —
+ FSII(S-748K-1745) Grade JP4
F-34 Turbine Fuel, Aviation, Kerosene MILT-831 33 Turbine Fuel, Aviation, —
+ FSII(S-748K-1745) GradeJP-8
F-35 Ttrrbke Fuel, Aviation, Kerosene MILT-83133 Turbine Fuel, Aviation ASTM D 1655 Aviation
Turbine Fuel, Jet A-1
F-44 Turbhe Fuel, Aviation, High-Flash Type MILT-5624 Turbine Fuel, Aviation, —
+ FSII(S-1745) Grade JP-5
F-54 Diesel Fuel. Militiw W-F-800 Fuel Od, Diesel Grade DF-2 —
(OCONUS)
F-65 Low-Temperature Diesel Fuel Blend 1:1 Mix F-54 With F-344F-35 —
— — ~W-F.800 Fuel Oil, Diesel Grades DF-J%” ASTM D 975 Diesel
DF-1, 7 DF-2 (COtiS) Fuel, Grades 1-D and
2-D
F-75 IFuel, Naval Distillate, Low Pour Point — —
F-76 IFuel, Naval Distillate NIL-F-16884 Fuel, Naval Distillate —
S-748 ‘Fuel System Icing Inhibitor (FSII) MfL-I-27686 Inhibitor, Icing Fuel System ASTM D 4171 Fuel
System Icing Inhibitom
S-1745 Fuel System king Inhibitor (FSII) High- MIL-I-85470 Inhibitor, Icing Fuel System, —

o CEN=( ,Flash-Point Type

otite Europeende Nonnatisation
RON= I ese.archOcraneMm&r
High Flush

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TABLE 3-4. , RUSSIAN GOST 305 AUTO D~EL F’UELS (Ref. 35)

SOVIE~-TYPE DIESEL FUEL a

&R NORTHERN
SUMMER WINTER ARCTIC
;
PHYSIOCHEMICAL Properties ‘L q Zs A
Cetane No. (rein) 45 4.$ 45 45
Pour Point, “C (rnax) ‘–lo –35 -45 –55
Cloud Point, “C (max) -5 -25 –35 -45
Flash Point, ‘C (rein) 40 35 35 30
Vkcosity at 20°C, mm 2/s or cSt 3.0-6.0 1.8-’5.0 1.8-3.2 1.5
Specific Gravity, dimensionless 0.860 0.830 0.830 0.830
at 20”C (max)

Fractional Composition at the Maximum Temperature in *C Indicated:!

1

50% Distills 280 280 280 240

90% Distills 360 34) 340 330
End’Point 369 34! 340 330
. ‘i

use type L fuel as the U.S. uses DF-2. Types Z and ZS com- 3-2.5.7.1 ~Field-Expedient Mixtures
pare to DF-1, and Type A to DF-A (Ref. 35). l?ield-ex~~dient mixtures include alternate fuels, blends
of one spec$cation fuel with another, and adulterated spec-
3-2.5.6.3 Foreign Commercial Diesel Fuels 9
ification fuels.
In a survey (Ref. 8) conducted to establish how well for-
In Europe, NATO units have used a 50/50 mixture of JP-8
eign sources of commercial diesel fuel would meet the
and DF-2~NAT0 Code No. F-65—as a winter diesel fuel.
requirements of OCONUS DF-2 per W-F-800C, a total of
When one $el is blended with another, the blend will have
78 samples of commercially available diesel fuel from at
all the flamjnability characteristics of both constituents, and
least 27 countries were found to have an average flash point
it will be fl~able over the entire range between those of
of 66°C (151°F), with a maximum of 88°C (190”F) and a
minimum of 21 “C (70°19. Thirteen of the samples had flash the constitu~ts. An example is the blend of JP-8 and DF-2;
points below the specification value of S6°C (133°F) minim- it would be flammable from the lean limit of flammability of
um, and ten of those were from a single country (from .JP-8, seen on Fig. 2-2, through the rich limit of flammability
which a total of eleven samples had been received). These of DF-2. Consequently, such blends represent a greater fire
undesirably low sampIe flash points ranged from21 to 55°C and/or exp16sion hazard than would either constituent alone.
~
(70 to 131°F). Seven of these 13 were below the specified
‘minimum flash point of W-8, i.e., 38°C (1OO”F), which 3-2.5.7.2 ~Comparison of Fuel Types
means that the potential for ignition could be greater in The principal fuel characteristic of concern in this hand-
some instances than it would if JP-8 were used. book is tla$rnability, and the fuels of major concern are
those that ~ or may be used in combat vehicles. These
3-2.5.7 IWrnary, Alternate, and Emergency Fuels include DF-,j2,JP-8, JP-5, and others. If flammability is to be
For every vehicle a primary fuel is designated that permits gaged by fljish points alone, then commercial diesel 2-D
full design performance. Alternate fuels are designated that would meet CONUS DF-2 requirements, as is shown in
provide acceptable operational performance, i.e., a level. of Ref. 7 in w~h samples horn throughout the U.S., taken in
performance that meets the minimum requirements defined 1990 and 1~91, had a minimum flash point of 56°C (132”F).
in the vehicle specification. Emergency fuels are also desig- Worldwide samples described in Ref. 8, however, failed to
nated for use when the primary or alternate fuels are not meet the O~ONUS 13F-2standard of a minimum flash point
available. I?erfozmance may be degraded, but emergency of 56°C (133°F) in 13 of 76 cases. There is no indication
fuels should not materially degrade the design operating life that only the foreign equivalent of commercial diesel 2-D
of the ve~cle (Ref. 36). The primary, alternate, and emer- was included in the samples. The sample horn Scotland 9
gency fuels for US Army materiel are given in Table 3-5. obtained in March with a flash pointof51 ‘C (124°F) could

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IWL-HDBK-684

TABLE 3-5. I?U’IW$ UfXI) 1NARM% MATERIIW (Ref. 12]

o PRJMARY FUEL
ALTERNATE FUEL
(See Note 1) EMERGENCY FUEL
Grotmd gasoline-eonmrting MIL-G-3056 F-57 (Gasoline)
materiel: OCONUS environments (MOGAS) F-67 {Gasoline)
F-18 (AVGAS)
CONUS environments ASTM D 4814 MXL-G-53006 (@sohol]
(S-I Fuel) ASTM D 910 (AVGAS)
(See Note 2)
Ground diesel-fuel-consuming W-F-800 (_lXesel), ML-T-83133 (JP-8), F-34 ML-G-3056 (MOGAS)
materiel: OCONUS environments F-54 (See Note 3} MILT-5624 (JP-5), F-44 F-57 (Gasoline)
ML-F-16884, F-76” F-67 (Gasoline)
F-75 (Navy Distillate)* F-18 (AVGAS)
ASTM D 1655 (Jet A-1) ML-T-5624 (JP-4), F-40
(See Note 4)
F<5 (Diesel ~lend)
CONUS environments W-F-800 (IXesel) ASTM D 975 (’Diesel) ASTM D 4814 (S-1 Fuel)
ASTM D 1655 (Jet A) ASTM D 910 (AVGAS)
(See Note 4) ML-T-5624 (JP-4), F-40
ASTM D 396 ‘TOI & F02)
Aviation materiel: Gasoline-consuming ASTM D 910 F-18 (AVGAS) ASTM D 4814 (S-1 Fuel)
[AVGAS), F-i8
Turbhe-fuel-consuming MILT-83 133 MJL-T-5624 (JP-5), F-44 —
[JP-8), F-34 MIL-T-5624 (JP4), F40
ASTM 1655 (JetA/A- 1)
ASTM 1655 (Jel B)
NOTES:

0
,,’ 1. Environmentalconditionsmay limit use of eestainalternatefbeis designatedwith m astetisk (*).
2. ASTM D 4814a spark-ignitionengine fuei (S-I t%el)that ailowsuse of oxygenatesto ertbmeeits antiknockquaiity.
3. AithoughW-F-800 is shownas the primaryfuei,MiLT#3133 (JP-8)or MILT-5624 UP-5)wiii be used as the prinuuyfud in those
theatemin which the singiefuei on the battlefieldis implementedin accordancewithDoD Directive4140.25and moremcentiy,with US
tadficadon of STANAG4362.
.- hid
4. Jet A-UF-35or Jet A is acceptablefor continuoususe in environmentswith cold to moderatetemDenmtres.For modemteto —-
tempmmres, Jet A-i/F-35 o; Jet A is not recommendedand shouldbe repixed with JP-8/F-34. ‘

well have been the equivalent of winter diesel and would lubricity did not present a problem, and the greater fire haz-
have met the DF-I criteria, i.e., a flash point 37.8*C (1OO”F) ard did not materialize (Ref. 11). In some instances, organi-
minimum Also two of the 13 samples failed to meet the zations added engine oil or hydrauiic fluid to “improve” the
OCOhWS DF-2 flash point requirement but wotdd have met lubricity, but this action added contaminants to the fue~
the CONUS DF-2 flash point requirement, and another three which increased filter ciogging. There was a probiem with
would have met the DF-A/DF-l flash point requirement. filters clogging in okler vehicles that had been using DF-2,
The user of commercially availalde foreign diesel fiel can- but this was the same problem that had been encountered
not rely upon meeting fuel specifications but shouid test the earlier at Fort Bliss in a program to establish the feasibility
fuel to ascertain its quabty, as was done in SWA (Ref. ii). of using JT-8 in diesel-engined equipmetm (Refs. 25 and
26) JP-8 or Jet A-1 cleans the DF-2 sludge out of rhe system
3-2.5.7.3 Single Fuel on the Bat.tlefieJd
and thus overloads the filters until the fuel system is clean.
In recent operations one mobility fuel was designated to
l%e one deficiency presented by JP-8 or Jet A-1 is the fail-
be the primary fuel used in both aerini and ground vehicles.
ure to produce smoke in the VEE.SS. For this reason, some
In Operation Just Cause-Panmq 1989-JP-5 was so des-
major commands chose to use DF-M, i.e., DF-2 that meets
ignated. In Operations Desert Shield and Desert Storm-
the requirements of ML-F-16884, instead of Jet A-1 in
SWA, 1990 to 1991—Jet A-1 was so designated and is still
used for organizations in Kuwait in 1993. Jn Operation Operation Desert Storm (Ref. 11). VEESS fuel usage is dis-
Restore Hope-Sornali~ 1992 to 1993-JP-5 was desig- cussed in par. 3-4.3.
nated the primmy fuel
3-2.S.8 Fn-Resistant Fuels
0 In Operation Desert Storm concern was expmsed that
the yet A-1 fuel did not have sufikient lubricity and that the
lower flash point would present a fire hazard. The iesser
Extensive research and development have been con-
ducted by the US &my to reduce fire vulnerability and

3-9
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MIL-HDBK-684 I,
increase fire survivability of mobility equipment by modify- of those properties pertinent to ignition and/or flammability.
ing the flammability characteristics of the mobility fuels, Hydraulic fluids currently in use are described in MIL-
particularly diesel fuel. Following several preliminary gen- HDBK-11~1(Ref. 41); hydraulic fluids and their usage are
erations of experimental formulations (Ref. 37), a lire-resis- covered in MIL-HDBK- 118 (Ref. 42).
tant diesel fuel formulation has been proposed (Refs. 38 and Because ‘K the wide and vastly different areas of applica-
39). This fuel contains 10% by volume of added water dis- tion, it is not surprising that hydraulic fluids have been clas-
persed with 12% by volume of emulsifier premix (equal sified by ‘~ many different systems based on various
parts of surfactant and aromatic concentrate) as a clear-to- characteristics, such as physical properties, chemical types,
hazy, aqueous microemulsion. The fuel displays an appear- operating ~haracteristics, utility, or specific applications.
ance and properties similar to those of the base fiel from Althou~h none of these groupings fully describe the proper-
which it is made, and its use in diesel engines does not ties of a hydraulic fluid, they are still employed and assist in
adversely affect engine durability. selecting fluids for use in specific areas. in this handbook
These fuels are not ready to be fielded. Various fire-resis- hydraulic fluids are classified by fire resistance.
tant fuel formulations were tried and did not meet all of the Hydraulic fluids can be classed as flammable, fs.re-resis-
fuel handling system and environmental performance tant, or nonflammable. A flammable hydraulic fluid can
requirements specified by the potential military users. bum almost as welI as a fuel does. The fire-resistant classifi-
The volumetric net heat of combustion of the fire-resis- cation is somewhat arbitrary because the degree of flamma-
tant fuel formulation is less than that of its base fuel by bility depe~ds on both the specific fluid and the definition of
approximately the amount of dilution with water. The vis- “flarnmabi$ty”. Generally, flammability has been gaged by
cosity of fire-resistant fuel is somewhat greater than that of whether or not a sustained fire results within an enclosure.
its base fuel and is substantially greater at low temperatures. However, ~ecause fireballs of sufficient strength and dura-
Fire-resistant fuel enhances fuel fire safety by decreasing tion can injure personnel, flammability can be evaluated
ignition susceptibility, by retarding flame spreading rates,
based upon~the fireballs produced when a shaped-charge jet
aad by self-extinguishing if ignited when spilled. It is effec-
or a high-explosive projectile encounters a fluid. Other
tive for starting, idling, and running diesel engines as well
gages of fl$nrnability are whether a flame results when a
as turbine combustors. On the other hand, it burns readily
, liquid sae~ or spray encounters a hot object and whether
when dispersed as a spray or mist.
the flame i! on the hot object only or also encompasses the
The partial vapor pressure of water above fire-resistant-
liquid or spray. Usually fire-resistant hydraulic fluids are of
fhel-type microemulsions has been experimentally deter-
three types! synthetic fluids, water-based fluids, and aque-
mined to be significantly less than that of pure water (Ref.
ous emulsi~s. Fire-resistant synthetic fluids are fire-resis-
40). It, has been determined also that sufficient amounts of
tant because of their chemical nature and include phosphate
water vapor exist (approximately 24% by volume) in other-
wise flammable fuel-air mixtures (approximately 2 to 3% esters, chlorinated hydrocarbons, halogen-containing com-
fuel by volume) ahead of an advancing fi~e to prevent sus- pounds, organophosphorgs
,, derivatives, and mixtures of
tained combustion above the bulk liquid. Hence the flame similar materials. The water-ba&d fluids are solutions of
orJ the surface of the fire-resistant fuel liquid is self-extin- various nat$ral or synthetic materials in water and depend
guishing. upon their water content for fire resistance. Glycols, ,poly-
Conversely, when the fire-resis@nt fuel is dispersed as a glycols, and mixtures containing additives are the most
spray or mist, the amount of water vapor formed by the common h$draulic fluids of this type. Aqueous-emulsion-
totaIly vaporizing droplets is of the smqe order of magni- type hydra~lc fluids also depend upon water content for fire
tude on a volume basis as the fuel vapor formed. Thus the resistance and are water-in-oil mixtures made from petro-
water vapor concentration in the fuel-air-water mixture leum hydrocarbons, but they may contain various additives
formed from a mist of fire-resistant fuel is about an order of to provide i other desirable properties. A nonflammable
magnitude less than that required to prevent sustained com- hydraulic fluid will not bum under most conditions.
bustion. The combustion characteristics are comparable to
those of a mist formed from only the base fuel; therefore, a 3-3.1 FIRE-RESISTANT HYDRAULIC FLUID
fuel fireball usually occurs when a shaped-charge jet perfo- Fire-resi&nt hydraulic (FRH) fluid normally refers to a
rates a fuel cell containing fire-resistant fuel. synthetic fl~d (compared to a petroleum-based fluid) and
contains an ~dditive package developed for a specific appli-
3-3 IIYDIUUUC mums cation. The ~synthetic base stocks are normally polyalpha-
As the use of hydraulics and fluid power systems has olefins or e$ters, such as phosphate esters. The following
increased, the number and types of hydraulic fluids avail- fluids are those normally used by DoD service groups. Perti-
able have also increased. Descriptions of the more common nent data Oriparameters related to flammability are given in
types of ,hydraulic fluids are presented with a brief summary Table 3-6.

3-1o
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o c) o
TABLE 3=6. ,HYDRAULIC FLUIDS PARAMETERS (lkfs. 43-50)
FLUID
PR0P13RTY MIL-H-5606 MIL-H-6083 MIL-H-46 170 MIL-83282 PvIIL-H-53119 MIL-B-46 176 MIL-H-19457
(CTFE!)
Flmh Point, 91-103 102-124 224 196-226 252-282
‘c (’w) ( 195-217) (2 15-255) (435) (385-437) (485-540)
Fire Point, 107-112 112 250-254 252-254 271-313
“C (“F) (225-235) (235) (480-489) (486-489) (520-600)
Autoigni[ion Temperature 225-238 238-243 368-410 347-407 630-646 396-436 560
(AIT), Vapor in Air, “C (“F) (437-461) (460-470) (694-770) (656-765) (1165-1195) (745-8 15) (1040)
AIT Liquid 400 322-400 927
Stream, “C (“F)
AIT, Spray,
“c(”F)
Net Heal of Combustion,
MJ/kg (Ih/lbm)
-%--l-+ (750)
504-730
(939-1350)
41,20
(17,726)
(630-750)
677-730
(1250- 1350)
41.14-41,54
(17,700- 17,870)
(1700)
>927
(> I700)
560
(2390)
Coefficient of Thcrmd Vol. E?xp. 2.556 X 10_” 2.778 X 10-s
m3/m3FC (in?/in?/”F) (4.5 x 104) (5.0 x 10-6)
Specific Heat, 2100 2093 980-1005
J/(kg.°C) [Iltu/(lbm.”F)] (0.50) (0.50) (0.234-0.24)
Latent Heat of Vmorizalion, 205
Id/kg - +

Surface Tension,
dynedcm I 28.99 20,97
I 1 1

Linear Flame Speed, mrds I.7 I

(cent’d on next page)

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TABLE 3-6. (cent’d)

FLUID
At
PROPERTY MIL-H-5606 MIL-H-6083 MIL-H-46170 ML-83282 MIL-H-53119 MIL-B-46176 MIL-H-19457
‘C CF)
(c’rFE)
Specific Gravity,
dimensionless
15 (60) 0.860-0.865 0.860 0.862 0.84-0.860 0.877-0,889
I
Kinematic -54 (-65) 2050 10,250 881
Viscosity 24 (76) “ 21.30 27.37
mm3/s or cSt
37.8 (100) 12.73 13.43 15.85 16.52 156 16.63-34.19
at -40”C, (40°F)
99 (210) 4.27 3.86 3.62 3.75 2:87
at 40”C ( 104”F)
116 (240) 2.9 2.1 I

149 (300) 2.1 1.5 ,

Absolute Viscosity, -54 (-65) 2050 10250 4870
MPa or CP 116 (240) 2.9 2.1 3.1
199 (300)
. . [ 2,1 1 ,
1.5 2.1
y. I 0.1678 (0.097) 0.0744 (0.043)
. Thermal Conductivity, 38 (100) I 0.1350 (0.078) I
‘N W/(mK) [Btu/(hft°F)] 93 (2oo) 10.1026 (0.0593) I 0.0675 (0.039) I

Bulk Modulus, 25 (77)* 1.884 (273,300) 1.891 (274,200) 1.680 (240,700)

MPa (lb/ft 2,
.- V’p&r PrgsSu_re,. . . ..2? (21!2 . . 1257.(9.51 . . . . . ..-- . . . . 467
. . (3.5)
-.–- 1267 (6) ---+---
‘a(mm”~) 116 (240) 2533 (19) .667 (5.0) 2000 (15)
149 (300) 7466 (56) 1’ 1133 (8,5) 9466 (71)
* also at 20.68 MPa(3000psi)
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3-3.1.1 MIL-H-46170, Hyhukk Fluid, Ru@- 2. Limitations. This fluid is not rust inhibited. Contam-
Inhib~ Fire-Resi.stkmg Syn.thdzk Hydro- ination of this fluid with MIL-H-5606 results in a significant
carbon-Base (N1.ilitary Symbol ~ loss of its fire-resistance propenies.
NATO Symbol H-544) 3. Constituent Materials. This fluid CQnsistsof a syn-
thetic hydrocarbon base stock and additives to meet the
Altho@ MIL-H46170 (Ref. 51) hydraulic fluid is the
technical requirements.
iire-resistant version of MIL-H-6083 (Ref. 52), it will still
produce a fkball when a shaped-charge jet passes through. 3-3.1.3 Proposed Single Hydraulic Fluid
MIL-H-46170 can be mixed with MIL-H-6083, and the
The Belvoir Research, I)eveIopmen~ and Engineming
mixture will produce fireballs given a shaped-charge jet
Center (BRDEC) has proposed a single hydraulic fluid
impact because the mixture has the worst characteristics of
(SHF) to replace the MJL-H-5606, M3L-H4i083, and MIL-
each constituent over the temperature range of each constit-
H-46170 hydraulic fluids currently used in Army equipmen&
uent and any temperature inbetween. Pertinent &ta relative
This single fluid is to be a fire-resistant fluid that will not
to MIL-H-46170 hydRlldiCfluid follow:
sustain a pool lire; it is to be usable at temperatures to -20*C
L lnrenakf Use. Type I is intended for use in recoil
or Iower, including use as a recoil fluid in large caliber guns;
mechanisms and battle tank turret hydraulic systems. This
it is to provide improved lubricity artd corrosion protection
fluid has superior fire-resistance characteristics compared to
for the eqnipmen~ and it is to be compatible wirh the seals
MIL-H-6083 fluids, and it has been evaluated and found sat-
and metallurgy of existing equipment- Toxic and environ-
isfactory for use in the Ml, M60, and M48 series tanks. If it
mentally hazardous constituents are to be ehnkated The
is to be used in other combat vehicles, a study should be
fiash point of the SHF is to be 192°C (378°F) (Ref 55).
made to determine its applicability, particularly with respect
to seal compatibility and low-temperature operability, in
such systems. Since this fluid is rust inhibitd it may be 3-3.2 NO~LE HYDRAULIC
used as a preservative medium for hydmulic systems and FLUIDS
components. Type II is a preservative fluid for aircmft A program was initiated by the Air Force to develop a
hydraulic systems and componen~. Type I is natural straw- MIL-H-5606 replacement without the restrictions imposed
yellow in color, but TjqE II is dyed red for identification by requiring compatibility with hydraulic systems that use
P-s- MIL-H-5606. This fluid was to be nonflammable in situa-
2. .Limitatiomr. For retrofit of hydraulic systems con- tions in which a threat produces a flash and a spray, which .
taining MTL-H4083, IWL-H-6083 should be drained as normally result in a &eball with both petroleum-based and
completely as possible. Contamination of MIL.H46170 fire-retardant hydrati~c fluids. This situation is the sense in
with MIL-H-6083 or MIL-H-5606 (Ref. 53) seriously which the term “nonflammable” is used. Very few fluids are
affects the fire-resistance chmcteristim of this fluid. This totally nonflammable, but the resistance of these fluids to
fluid cannot be used in the recoil sysmn of self-propelled ignition and subsequent burning is so far superior to that of
artillery because its low-temperature viscosity is too hi~ existing fluids defined as fiqxesistant that the use of the
MIL-H-6083 hydraulic fluid is U* instead. term nonhnrnable is justiiki. The operational properties
3. Conrti-tuent MaMria&r. This fluid consists of a syn- of MIL-I-L5606 hydraulic flukl except densi~ and system
thetic hydrocarbon {alphaolefin polymer) base stock and material compatibiMy, were used as target requirements for
additives to mea the technical requirements of the finished this nonflammable fluid. No separate efforts were made to
producL develop nonflammable hydraulic fluids for ground vehicle
systems. ‘Ms fluid has been adopted by the &my as MIL-
3-3.1.2 NIWH-83282, f!lyh.uf.ic Fh@ Fire- H-531 19(ME) (Ref. 56). Pertinent properties of rhis fluid
Retitanh Synthetic Hydrocarbon-Base, are tabulated in Tkide 3-6.
Avcra& Metric, NATO Symbol H-537 ML-H-53 119 is a commercially available chlorofluoro-
This US Air Force (USWspecified hydraulic fluid, per carbon fluid based on chlorotrifiuoroethylene (CIl?E).
ML-H-83282 (Ref. 54), is the fire-retardant version of C.El% has no flash poin~ but it does have an allowable heat
MIL-H-5606. Perdnent data relative to this hydraulic fluid of combustion of 11-51 IWkg (2748 Btu/lbm) maximum.
follow. Thus there could be some combustion involvedj particularly
1. Intended Use. This fluid is intended for use in auto- if the fluid is tested with the compression-ignition test used
matic pilots, shock absorbers, air compressor gearboxes, for the water-based catapult hydraulic fluig MIL-H-22072
brakes, flap control mechdsms, missile hydraulic servo- (Ref. 57).
controlled systems, and other hydraulic systems using syn-
thetic sealing materials. me recommended operating tem- 3-3S PETROLEUM-BASED F’LUIDS
perature range is from -40 to 204°C (-40 to 40(PF). Tbe petroleum-based fluids that follow are stall used for
Although designed for aimraft use, this fluid has applica- some applications in hydraulic systems of alI the branches
tions in ground equipment of service, especially low-temperature applications.

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MIL-HDBK-684
3-3.3.1 MIL-H-6083, Hydraulic Fluid, Petroleuin- 3. Constituent Materials. MIL-H-5606 consists of
Basefor Preservation and Operation (Mii- light petroleum fractions, a viscosity index improver, an
tary Symbol OHT, NATO Symbol C-635) oxidation m~bitor, and TCP antiwear agents. 4
Pertinent data relative to MIL-H-6083 (Ref. 52) hydraulic I
3-3.3.3 hflL-EI-19457, Hydraulic Fluid, Fire-
fluid follow
1. Zntemded Use. This hydraulic fluid is intended pri- Resistant, Nonneurotoxic
marily for use as a preservative for aircraft hydraulic sys- MIL-H-19457 (Ref. 58) is a fire-resistant fluid for
tems and components in which MIL-H-5606 is used as an hydraulic s$tems that are accumulator loaded and generate
operational fluid and for use as an operational preservative pressures above 4.14 MPa (600 psi) gage. This fluid was
fluid for all tactical and support ordnance equipment for compounded for use in submarines and must be a stable,
which a determination has been made that MIL-H-46170 homogeneous formulation of tertiary butylated triphenyl
(FRH) cannot be used. Examples of ordnance use are phosphate and other ingredients. Its fire resistance is 42:1
recoil mechanisms and hydraulic systems. for rotating minimum when tested using the compression ratio test by
weapons or aiming devices. The fluid is dyed red for iden- which the cetane rating is determined. This fluid would be
tification purposes. The operating temperature range is –54 hazardous to personnel if it were released in air and
to 135°C (-65 to 275”F). This hydraulic fluid has a rather breathed. ,
high rate of evaporation and should not be used as a gen-
eral-purpose, high-temperature lubricant. 3-3.3.4 MIL-B-46176, Brake Fluti, Silicone, Auto-
2. Limitations. The rust-preventive additive somewhat ntotive, All- Weatheq Operti”onal and Pre-
increases the viscosity of this fluid and also limits its high- serv~”ve, Metric (Military Symbol BFS,
temperature capability. Consequently, it is not generally a NATO Code No. H-547)
suitable aircraft hydraulic fluid except in those systems spe- This silicgne-based hydraulic brake fluid, MIL-B-46176
cifically designed for this fluid. It is not interchangeable (Ref. 59), is for use in brake systems operating at ambient
with any other type or grade of hydraulic fluid. temperature ranging from -55 to +55°C (-67 to +131°F).
3. Constituent Materials. This hydraulic fluid consists The flash pdint of this fluid is not less than 204°C (399°F).
of light petroleum fractions, a viscosity index improver, an
oxidation inhibitor, and tricresyl phosphate (TCP) antiwear 3-3.4 @lM?AULIC FLUID HAZARDS
agents. / 4
3-3.4.1 Ignition and Combustion of a Spray
3-3.3.2 ML-H-5606, lilydraulic Fluid, Petroleum- When a ~gh-pressure line is ruptured either by direct
penetration or by being jarred loose as a result of impact,
Base, Aircrajl, Missile, and Ordnance (Mil-
various combinations of events can occur. Initially, of
itary Symbol OHA, NATO Symbol H-515)
course, a ~st or spray would develop, and depending upon
Pertinent data relative to USAF-specified IvUL-H-5606 the size of $e rupture, this,“spray could become more of a
(Ref. 53) follow: stream than la mist.
1. Intended U$e. The primary intended use of this fluid In 1972 ~-onan (Ref. 60) conducted some tests of incen-
is in aircraft applications, such as automatic pilots, shock diary bulle~ Impacting either a pressurized hydraulic fluid
absorbers, brakes, flap control mechanisms, missile hydrau- line or a pl~te covering a hydraulic fluid spray to establish
lic servo-controlled systems, and other hydraulic systems whether there were benefits to be obtained by using MIL-H-
using synthetic sealing material. This fluid has limited use 83282 rath~r than MIL-H-5606. In all of his firings into
in ground equipment since it does not provide any rust pro- pressurized Ihydraulic lines with both MIL-H-83282 and
tection. This oil is dyed red for identification purposes. The MIL-H-560~, fireballs were obtained that had mean dura-
recommended operating temperature ranges are –54 to 71“C tions of ap~roximately 1.61 s unless the fires became sus-
(-65 to 160”F) in open systems and -54 to 135°C (-65 to tained. In 6,,of 28 tests with MIL-H-5606, the fires were
275”F) in closed systems. For sealed systems pressurized sustained, whereas in none of the 20 tests with MIL-H-
with inert gas, a maximum operating oil temperature of 83282 was the fire sustained. Clearly then there was a slight
260°C (500”F) can be tolerated for short periods (not to advantage t!using MIL-H-83282 instead of MI.L-H-5606.
exceed 15 ruin). In Noon&’s tests in which the incendiary bullets were
2. Limitations. MIL-H-5606 has a rather high rate of fired through a striker plate into a hydraulic fluid spray,
evaporation and should not be used as a general-p’urpose, there was a less clear differentiation. With MIL-H-5606
high-temperature lubricant. Shipment and storage of sys- eight of 10~tests resulted in fires, all of which were sus-
tems filled with this fluid require draining and refilling with tained. Wldi MIL-H-83282 17 of 18 tests resulted in fires,
MIL-H-6083 for preservation and testing. This fluid is not 13 of whick were sustained. Although ML-H-83282 was
interchangeable with any other type or grade of hydraulic better than MIL-H-5606, it was only marginally better. Also a
fluid. tested was a proprietary hydraulic fluid under evaluation by

3-14
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MIL-I+DBK*84
the USAF, known as AEROSAFE 2300, which produced lets for igniters, and aIl four tests resulted in sustained fires.
,,
O fires in all 37 tests, all of which self-extinguished, A missile
hydraulic fluid, MIL-H-46004* (Ref. 61), was also tested,
Some cup flammability tests** were performed with both
MIL-H-6083 and MIL-H-83282. Jn these tests the fluid was
but in nine tests six fires resulted, all of which had to be preheated to 27°C (80”F), 104°C (220W), or 177*C
extinguished. (350°F). For all thm fluid temperatures MIL-H-6083 pro-
In 1974 Noonan (Ref. 62) conducted another series of duced sustained fires. ML-H-83282, however, self-extin-
tests to compare MIL-H4083 to M3L-H-83282 for relative guishtxl when tested at the two lower fluid tempemmres and
fire survivability of the M60 MBT. This time he performed produced a sustained fire at only the highest fluid tempera-
a fluid spray test for the vast majority of specimens. He ture.
made two changes to his test procedure, both of which were Because a better definition was needed for the fluid spray
unfortunate. F- for these tests he changed tirn the oil ignition tesq a program was conducted by Kanakia et d.
burner nozzle he used in the earlier test series to a nozzle (Ref. 50) to establish the effects of fluid spray pattern and
that better met the fedeml standard called for in MIL-H- droplet size upon ignition in order to produce a stan~
83282. This nozzle change resulted in a narrower spray, method for hydraulic fluid flammability assessment. From
which had difkrent ignition and combustion characteristics. this program it was concluded that the aix vekci~ through
II was more dMicrdt to have the flash fkom the incendiary the nozzle was the most critical parameter to obtaining
bullet coincide with the spray, and the fires that did ignite reproducible results. The temperature of the fluid being
tended to self-extinguish. Second to obtain more positive tested is also critical but can easily be measured. ‘he pres-
ignition, he substituted a d flame produced by burning sure at the nozzle is important but can be adjusted arid mea-
an oil-soaked cloth for the incendiary bullet flash. This sured. ‘Rte nozzle must be standardized in terms of type and
replacement igniter produced much less heat over a much manufacturer and must be tested and preselected to main-
smaller space but for a longer time than did the incendiary tain uniformity among laboratories. These nozzles must
bWeL The results for 123 tests with MIL-H-6083 and for obtain a consistent pattern and droplet size. Freely dispemd
165 tests with ML-H-83282 were all the same All pro- fhel droplets are a serious flammability hazard in the pres-
duced fires that .seI,kxtinguished. The MIL-H-6083 iires ence of a proper ignition source; however, experiments have
had a median duration of 1.04s and the ML-H-83282 fires shown that once the ignition source is remove4 the flame

0
had a median duration of 0.83s. Similar tests using the oil may not be sustained, as shown in Tkble 3-7.
burner nozzle produced different resuhs. The MIL-H-6083
fluid producd sustained fires in all 23 tests. The MIL-H- *~e hid was placedin a cup and bested to one of duee speci-
83282 fluid produced OIdy 31 SU@lId fires in 104 tests, fied tempemmres.An open, wide-mouthedBunsen burner flame
and the other 73 fires self-extinguished with a median dura- was applied to the fluid surface for three seconds and then
tion of 3.49 s. Four tests were performed with MIL-El- removed.If the tire in the cup Self-tinguished upon withdrawal
83282 fluid using the oil burner nozZle and incendiary bul- of the flare%the tluid was consideredto be capable of producing
onty a nonsustainedfire.The three initial bulk fluid tempemmres
represented 27°C-an unoperating hydrautic system, 104W-a
W.TL-W$6CM)4
W= cancelled 19 hdy 1982 and replacedby ME.- hydraulic Sy~~ ~ freqlmt O~IZtiOIIS,and 177°C-a gun
H-!%06. recoil systemafter manyrapidly firedrounds.

TABLE 3-7. RESPONSE OF VARIOUS HYDRAULIC

FLUIDS TO HIGH-PRESSURE SPRAY IGNITION
(Federal Tmt Stmdmd 791J3, Method 6052]
(w. 48)
FLUID RESULTS
MIL-H-5606** Ignition at pilo4 self-extinguishing flame
ML-H-6083** I&ition at pllo~ self-extinguishing flame
MIL-H-8328W* Ignition at pilot, self-extinguishing flame
MIL-W46170* Ignition at pilo4 self-extinguishing flame
MlL-H- 13919B* Ignition at pilo~ self-extinguishing flame
MS-5 Ignition at pilo~ self-extinguishing flame
Skydrd 300 (Phosphate Ester) No ignition at 152,305, or 457 mm (6, 12, or 18 in.)
MIL-B46176* Source A Ignition at pilo~ self-extinguishing flame

,,:0
,’
MIL-B46176* Source B

*
Ignition at pilot, self-extinguishing flame
N(I’TE Ropenies of materialsare given in Table 2-4.
change letters applyto the materialstestedor test methodsused.
**~m~ letter not known

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MIL-HDBK-684
Finnerty et al. (Ref. 63) demonstrated that MIL-H-46170 a vapor of 100°C (212°F) but has a lower limit of flya-
FRH fluid would ignite and burn in mist form when exposed bility in a.iras a mist of 29°C (84”F).
to a strong ignition source, The FM fluid, at a working In a mqre recent ballistic test program conducted by 4
temperature of 77°C (170”F) and contained in 6-mm (0.25- Wright-Pat~son Air Force Base (Ref. 65), a 20.68-MPa
in.) outside diameter, 0.9-mm (0.035 -in.) @ick corrosion- (3000-psi) ~hydraulic system was installed within a simu-
resistant steel (CRES) 304 tubing (which simulates the lated aircrafi dry bay, and a Russian 23-mm high-explosive
hydraulic fluid tubing used in US combat vehicles) and incendiary pacer (HEIT) projectile was fired into it while an
pressurized to 10.35 MPa (1500 psi), sprayed when the tub- airilow of d m/s (Oknot) or 244 rnk (475 knots) passed over
ing was hit by one or more explosively launched steel the simulated aircraft. With an airtlow of Ornh MIL-H-5606”
cubes. The cubes had a mass of 0.13 g (2 gr), 1.04 g (16 gr), had 32 sustained fires in 32 tests, and MIL-H-83282 had 32
or 6.48 g (100 gr) and a velocity of approximately 3(IQto self-exting~shing fires with a mean duration of 7.31 s. W]th
800 rrds (984 to 2625 ft/s), which simulates behind armor a 244-m/s #rflow MIL-H-5606 bad no fire in 10 tests and
debris from, a kinetic energy penetrator. These tests demon- 22 self-extinguishing fires with a mean duration of 3.07 s,
strated that these fragnent impacts could result in breaks in and MIL-H~83282 had no fire in five tests and 27 self-extin-
the steel tubing, that the FRH fluid could escape through the guishing fi&s with a mean duration of 8.44 s. These results
breaks and form a mist, and that the FRH fluid mist could be indicate that under high-speed airflow conditions, MII.,-H-
ignited by a strong ignition source-an ethyl alcohol fire— 83282 can ~xperience more combustion than MIL-H-5606.
even when the FR.H fluid is well below its flash point. This differ~nce would be important for combat vehicles
This ignition of hydraulic fluid in mist form was again only when $ere is a marked excess of oxygen present, such
demonstrated in another program conducted in 1970. In that as is provided by a high-speed aixflow or rupture of an oxy-
progam a silicate ester hydraulic fluid (~ronite 8515) had gen bottle. ;,
an ihitial bulk fluid temperature of approximately 21°C.
(70°F) and a flash point of 202°C (395°F). The baIlistic 3-3.4.2 ~aliistic Rgpture of a VesseI
impact produced a spray, ignition. of which resulted in an When an incendiary round penetrates a hydraulic fluid
explosion. (This incident is further described in par. 4- reservok o: line, there are several possible results. The
4.4.1.) parameters affecting these results are the volume and tem-
There is strong evidence that a flame” front will pass perature of \,fie fluid and the duration and intensity of the
through a mist more rapidly than through a vapor-air mix- incendiary e,xposure. With ballistic impact there is sufficient a
ture. Burgoyne (Ref. 64) measured the burning velocity of energy over~sufficienttime to create a flammable mist and to
tetraJin (C IOHIZ ) mist in air as a function of the mist droplet ignite it. Results of ballistic tests using a pressurized
size, as is shown on Fig. 3-2. Note that the flame front speed hydraulic cylinder and 20-mm HEIT projectiles, shown in
in vapor is approximately 280 mm/s but that the speed with Table 3-8, indicate that some fluids produce self-sustaining
droplets of 0.015 mm or greater is approximately 605 mm/s. fires. The pdtroleum-based fluids (MIL-EI-5606 and MIL-H-
Burgoyne indicated that tetralin, which has a boiling point 6083) produced a large fireball and sustained burning of the
of 207°C (404°F), has a lower li~t of flammability in air as remainder of the fluid when subjected to these ballistic tests.
750T Results ob$ined with other fluids, however, generally
●e showed a f$eball (of various sizes) but no residual burning.
Finnerty (Ref. 63) demonstrated that a shaped-charge jet
ruptures a ~ydraulic fluid container, broadcasts the fluid,
500 “ and ignites it. In tests in which shaped-charge jets perfo-
rated steel r~rvoirs containing either MIL-H-6083 or fire-
resistant MIL-H-46 170 that had no fire protection, both
hydraulic fl~ids ignited and burned (Ref. 67). See par. 7-
250 3.2.1.3 for hydraulic fluid reservoir protection techniques.
.,
3-3.4.3 Combustion of a Pool

il~ o 0.010 0,020 O.owl 0.040

In a hydraulic system that is under pressure during nor-
mal combat vehicle operation, the operating temperature
can be apprbxirnately 104”C (220”F). The temperature of
DropletDHmeter,mm the fluid in a gun recoil mechanism may be substantially
higheq one ~stimate is 177*C (350”F). Therefore, the nor-
Figure 3-2. Effect of Mist Droplet Size on Burn- mal operating temperature is near the flash point of the
ing Speed of Monodispersed Tetralin-Air Sus- petroleum-b~sed fluids that have been in use. Flame propa- a
pension (Ref. 64) gation studi~~have shown that once this fluid is ignited, the

3-16 (t
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MIL-HDBK-684

,,,
O
T~LE %$. RESPONSE OF VARIOUS HYDRAULIC
IMPACT OF 20-mm HEIT AMMUMTION
FLUIDS
(Ref. 66)
TO BALLJSTIC

TEST FUEL
TEMPERAT’LJR.E
FLlm) i AMBENT t 77ec I
2 l“c (70”I?) I
(171%’)
MIL-H-5606** 1
x x Inmact fireball. sustained burnimz
.

MIL-H~83** I x x Impact fireball, sustained burning

MIL-H-83282A* x x Impact fireball
MIL-H46170” x x Impactfireball; 0.803-s duration
MIL-H-13919B* x x Impact fireball, some sustained burning
at 77°C tests
MS-5 x x Small impact fmball
Skydrtd 300 (Phosphate Ester) x x Small impact fireball
MILB46176* Source A x x SmaU impact fmball; 0.349-s duration
MIL-B46176* Source B x x Impact fireball;0.667-s duration
NOTE propertiesof materialsare given inTab[e24.
*Changeletter appliesto materialused.
**~~ge letter not knOwn

flame should spread until total pool involvement has 3-3.4.4 Ignition and Combustion on a Hot Sttr-
occurred. Flame propagation, however, occurs only after the faee
temperature at the surface of the bulk liquid is near the flash In an effort to relate Iire vulnerability to hot-surface igni-
point of the fluid. It is improbable that the bulk temperature
,,
0
could be maintained at or near 200”C (or even reached)
until ignition occurs. Hence it is unlikely that bulk liquid
tion, it was detenn.ined that mist from petroleum-based flu-
ids-flash point of approximately 100°C (212”F)-would
not ignite when sprayed onto surfaces heated to 730”C
involvement could ever occur with the newer fire-resistant
(1350°F), i.e., glowing red. l%e same result was obtained
hydraulic fluids. Tltis faa is further indicated by the ballis-
with fire-resistant fluids. This result was entirely unex-
tics tests described in Ref. 66, which showed residual burn-
pecte~ so fmlher expairnents were conducted to explain iL
ing with the petroleum fluids and no residual burning with
The procedure used was a combination of a high-pressure
the other fluids (Ref. 48). It is interesting to note that
spray apparatus (l%& Tes~Std. 791B, Method 6052) and the
another petroleunwbased fluid, ML-H-13919*, which had a
significantly higher flash point than that of MIL-H-5606, hot manifold (Fed. Test SttL 791B, Method 6053). TabIe 3-9
showed less extensive residual burning than MIL-H-5606. shows that the degree of atomization greatly influences the
Again a relationship exists between flash point and bulk liq- surface temperature required for ignition.
uid b iINOh@menL M should be emphasize~ however, To better understand those situations in which the fine
that the mist flammabtity characteristics are not directly mist would not ignite on the glowing red surflme, various
related to flash poinL MIL.-B46176 has a still higher mini- methods of mist generation were attempted. ‘he standard
mum flash point, 204W (399”F), but also produced a fireb- procedure of Method 6052 used a 0.4-mm (0.014-in.)
all from the 20-mm HEIT impact hat was, however, of a square-edged orifice and 6.9 MFa (1000 psi) niuogen pres-
shomer duration than the one produced by MIL-H46170. sure. It was thought that perhaps the mist formed by this
When a liquid container is in contact with the detonation of method produced an ovemich situation at the heated surt%ce
a high-explosive projectile, the detonation undoubtedly will and that forced dilution with air might produce a i%el-air
simultaneously form a mist and, if the fluid is combustible, mixture in the flammable range. Therefore, in one series of
ignite it (Ref. 68). Flame propagation studies of bulk fluid experiments mist generation was accomplished by using a
have shown hat the fluid has to be heated to near its flash smooth-bore fueldelivery tub, the mist was formed by
point before even a wick wiI1stay ignited or certainly before three intersecting air jers that caused the fue~ stream to
aflame will propagate. break up into very fine droplets. The mist formed using this
procedure of air impingement also wouldnot igniteat sur-
*MIMI- 13919is now obsolete. facetemperatures up to 730°C (1350’’F).
8!
!
o

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MIL-HDBK-884 ~

TABLE 3-9. EFFECT OF ATOMIZIN@ PRESSURE ON

N?IST FLAMIMAB ILITY (Ref. 48)
MANIFOLD S~ACE TEMPERA- REQUIRED FOR IGNITION, ‘C (“l?)
FLUID HIGH PRESSURE, 6.9 MPa ~1 LOW PRESSURE, 0.69 MPa
MIL-H-6083* No fue up to 730 (1350) ‘ 524 (975)**
IWL-H-83282A** * No fwe up to 730 (1350) 400 (750)
1
IWL-H-46170** * No fne up to 730 (1350) 400 (750)
Skydrol 300 (Phosphate Ester) No f~e up to 730 (1350) 677 (1250)
MS-5 649 (1200) 454 (850)
NHL-G-13919B*** No fwe up to 730 (1350) ~ 482 (900)
*Changeletter of materialused not known
**Temperaturegivenbulk fluidtemperatureof 14°C(25”F)
*,**Ch~ge letter appliesto materialused

Further studies were conducted with tists formed by a 3-4.1.1 $IIL-L-2104, Lubricating OiZ, Internal
standard nozzle from a T-63 turbine engine. These results 4@nbustion Engine, Combat/Twtical Ser-
!,.
showed that the mists formed by this procedure ignited vice
instantly upon coming into contact with the tiot surface, the The US ‘my lubricating oil used in the crankcase of
temperature of which was greater than 730°,C (1350°F). The both spark~land compression-ignition internal combustion
same results were obtained with two petroleum-based flu- engines and in other applications, such as power transmis-
ids; thus once again the relationship is to particle size rather sions and p~wer systems, is specified in MIL-L-2104 (Ref.
than volatility. 69) and co~es in four grades: 10W, 30, 40, and 15W-40.
When a low-pressure (nonmisting) spray impinged on the The specified minimum flash points of these four grades are
same hot surface, the ignition temperatures were entirely 205°C (40$’F), 220”C (428”F), 225°C (437°F), and 215°C
different. It is interesting to note in Table 3-9 that an 9
(419°F), respectively. The specified kinematic viscosities,
increase in hot-surface ignition temperatures of MIL-H- i.e., minimum and maximum values in cSt at 100”C
6083,,relative to those of MIL-H-83282 or MIL-H-46170, is (212°F), for these four grades are (5.6, <7.4), (9.3, <12.5),
observed (relative to the minimum MT) in the low-pressure (12.5, c16.~), and (12.5, <6.3), respectively. Some mea-
spray procedure. It would seem, therefore, that a low-pres- sured v~ues for these parameters are in Table 3-10.
sure or tipping leak would be very hazardous due to the i,.
low temperature required for ignition. 3-4.1.2 i@-L-2105, Lubricating Oil, Geaq ikM.ti-
+rpose
34 OTHER PETROLEUM, OILS, AND
Multip~ose gear oil for the US Army is specified in
LUBRICANTS (POL) MIL-L-210$ (Ref. 71) and comes in three grades: 75W,
3-4.1 TRANSMISSION FLUIDS, ENGINE 80W-90, mi~ 85W-140. The specific minimum flash points
OILS, AND LUBRICANTS for these tl-ireegrades are lSO°C (302°F), 165°C (329”F),
A goal of the DoD is to limit the number of POL products and 180”C (356”F), respectively. The specified kinematic
required. Therefore, certain classes of fluids are used to ser- viscosities Ii.e., minimum and maximum values in cSt at
‘ 1,
vice more than a single requirement. A number of research 100”C (21~F), for these three grades are 4.1, no require-
programs are currently underway to evaluate multiuse of ment; 13.5,~,<24.O;and 24.0,<41.0.
1,
fluids in order to reduce’ the number of fluids required to be
stocked and to prevent the required use of proprietary prod- 3-4.1.3 $IL-L-7808, Lubricating Oi& Aircrajt
ucts. The paragraphs that follow list the specifications cur- Turbine Engine, Synthetic-Base, NATO
rently ~eing used and present the only available property ~ode No. 0-14/3
concerned with flammability, the flash point. ,If other perti- This air$aft lubricating oil for gas turbine engines is
nent information is available, it is included. Other properties specified in#MIL-L-7808 (Ref. 72) and is available in a sin-
are given inMIL-HDBK-113 (Ref. 41). gle grade. The specified minimum flash point of this fluid is

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o c) 0
TABLE 3=10. TYPICAL PROPERTIES OF SELECTED LUBRICANTS (Reh 10,44,45,50, and 70)
MIL-L-2 I04 MIL-L-7808 MIL-L-23699 MIL-L-46 152 MILL-46 167
PROPERTY
low 30 40 15W-40 30 5W-30 1OW-3O 15W-40
Specific Grnvity, 0.883 0,891 0.893 0.886 0,92 0.99 0,894 0.886
dimensicmless
Hash POint, 204-214 218-220 225 204-211 207-225 227 216-247 209 204-235 218 200-218
%! (OF) 399-417) (424.428) (437) (399-412) (405-437) (440) (421-477) (408) (400-455) (424) (392-424)
Latent Heat of T4
V8pariz22tion,
- Iwkg
Heat of 34.40-35.78 30.36-33.04
Combustion, (15,211) (14,790- 15,383) (13,060- 14,215)
h4J/(kg.K) [Btu/(lbm’”P)
Specific Hent nt 2.10
Constnnt Pressure,
kJ/(kg,K)
Autoignition 350 372 363 387-412 384-415 364-368
Tempcmture, ‘C (“F) (728-755) (725-778) (687-694)
Vapor in Air
Minimum Ignition 704 621
Tempemturc, “C (°F) (1300) (1150)
Strenm on Hot Manifok
Minimum Ignition 720 680 705 834 >816 685-690
Temperature, ‘C (“P) (1533) (?1500) (1265- 1274)
Spray on Hot Manifold
Pire Point, 236 24 i 238 238 243-247
“c (“P) (460) ~_ —. (469-477)
Surface Tension, 32.71
dynes/cm
Flame Propagation on 1.98 1,47 1.39 1,48-1.75
Liquid Surface, rnnds
Kinematic Viscosity, 6.7 ll,t3-12.l 14.8-15.3 14.3 3,1-3.3 10,50-12.28 12.17 9.58-11.92 14.3-15.19
mm2/s or cSt,
at IOO°C(212°F)
at 40”C ( 104°F) I07 152 78.64- 115.2 78,42 46,83-92.88 112.05
nt 389C ( 10O°F) 12.1-12.58
at 24°C (76°F) 89.67
Pour Point, -33 -18 -15 -24 -35 -24
‘c (“P) (-27) (o) (5) (-1 1) (-3 i) (-1 1)
 Downloaded from http://www.everyspec.com

MIL-HDBK-684 ~
‘21O”C (41O”F). The specified kinematic viscosity of this In an evaluation of commercially available, rebranded
fluid is at –53.9°C (-65°F) 17,000 cSt maximum and @ni- lubricants, 5 of 16 samples of SAE 30 and 2 of 24 samples
mum at 100”C (212”F) 3.0 cSt. Some typical property val- of S,AE 10~-30 were below the specified flash points (Ref.
ues are given in Table 3-10. 70)4 [
I
3-4.1.4 MIL-L-9000, Lubricating Oil, Shipboard 3-4.1.8 ~IL-L-46167, Lubricating Oil, Internal
Internal Combustion Engine, High-Output ~ombustion Engine, Arctic
Diesel Specification MIL-L-46167 (Ref. 77) was prepared by the
l%is US-Navy-prepimed specification for lubricating oil US-y for one grade of lubricating oil to be used in inter-
for high-output diesel engines is specified in MIL-L-9000 nal combustion engines, both spark- and compression-igni-
(Ref. 73) and is available in a single grade. The specified tion types, when the ambient air temperature is in the range
minimum flash point is 199°C (390”F) and the specified of –55 to 5°$ (-67to41 “F) and to be used in arctic regions as
kinematic viscosity range is 12.5 to 16.5 cSt at 100”C
an all-weather power transmission fluid. The minimum flash
(212°F).
point is 220,°C (428”F). The specified kinematic viscosity is
3-4.1.5 IWIL-L-21260, Lubricating Oil, Internal 5.6 cSt minipmm at 100°C (212”F), 8,800 mm2/s (cSt) max-
imum at -4$PC (-40”F), and 75,000 mm 2/s (cSt) maximum
Combustion Engine, Preservat@e and
at –55°C (-fi7°F).
Break-in
This US-Army-prepared specification for lubricating oil, 3-4.1.9 ~-L-765, Lubricant, Enclosed Gea~ Non-
which is intended for preservation and breaking in engines
e!ytreme Pressure
and transmissions, is specified in MIL-L-2 1260 (Ref. 74)
and is available in four grades: 10W, 30, 40, and 15W-40. The federal specification, W-L-765 (Ref. 78), covers
The specified minimum flash points and kinematic viscosi- four grades fof enclosed gear oil for nonextreme conditions.
ties at 100°C (212°F) are the same as those for MIL-L- These grade~ are 80, 90, 140, and 250, and their respective
2104. flash points, are 177°C (350*F), 191°C (375”F), 204°C
(400”F), an? 204°C (400°F).
3-4.1.6 N41L-L-23699, Lubricating Oil, Aircrafi
Turbine Engine, Synthetic Base 3-4.2 ANTIFREEZE COMFOUNDS
This US-Navy-prepared specification for aircraft turbine Most ant$reeze compounds use mixtures of water, gly-
lubricating oil, intended for use in gas turbine engines, heli- CO1,and an additive package. Therefore, flammability con-
copter transmissions, and other aircraft gear boxes, is speci- siderations ,,ae not usually given to these products. A
fied in MILL-23699 (Ref. 75) and is available in a single flammablli~ hazard could occur if the water concentration
grade. The specified minimum flash point is 246°C (475”F). were reduced substantially, e.g., by evaporation. Mist flam-
The specified kinematic viscosity is 5.5 cSt at 98.9°C mability’ ‘would begin to occur with glycol concentrations
(210°F). The maximum value is 13,000cSt at -55°C (-67”F), estimated tiound 6070 by volume, and sustained flame
and this should not change more than k6% after 72 h A5 min propagation would occur with a glycol concentration esti-
of soaking at that same temperature. At 37.8°C (1OO”F)the mated greater than 90% by volume. The effects of this phe-
viscosity should be 25 mm 2/s (cSt), and at 98.9°C (210”F) nomenon were illustrated in two tests of a double-walled
the viscosity range should be 5.00 to 5.50 mm2/s (cSt). Some
fuel cell in which the interstitial space contained either
typical properties of this lubricant are given in Table 3-10.
water with 25% aqueous film-forming foam (AFFF) or
3-4.1.7 MILL-46152, Lubricating Oi~ Internal water with 2S70 AFFF and 5070 propylene glycol (PG), and
the fuel tank contained commercial diesel fuel. (Propylene
Combustion Engine, Administrative Service
glycol was used rather than ethylene glycol, which is gener-
This US-Arrhy-prepared specification, MILL-46152
ally used in automotive applications, because the latter is
(Ref. 76)*, is for the purchase of engine lubricating oil for
toxic.) The ~fireballs-produced when the jet from an
use in noncombat, administration vehicles. It covers five
M28A2 rocket warhead perforated the fuel cell—lasted for
grades: IOW, 30, 5W-30, 1OW-3O,and 15W-40. The speci-
0.041 ‘Switi the water-25% AFFF mixture and for 1.000 s
fied minimum flash points of these grades are 205°C
(401”F), 220”C (428”F), 200”C (362°F), 205°C (401”F), with the 2590 water, 2570 AFFF, and 5070 PG mixture (Ref.
and 2 15°C (419”P), respectively. Some typical properties of 79). These tests indicated that the propylene glycol provided
@ese fhids are given in Table 3-10. a flammable:fuel and thus increased the duration and size of
the diesel fuel fireball. The following specification products
*MIL-L-46152has been supersededby A-A-52039,Lubricating are generall~ used to lower the freeze point of water in com-
Oil, Automotive Engine, API Service SG, 31 October 1991. bat vehicles.:

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3-4.2.1 MIL-A-11755,Anti freeze, Arctic-Type potassium acetate. Cryotech E3~ Liquid Runway Deice@
,, Pertinent data relative to MSL-A-11755 antifreeze (Ref. (Ref. 85) has been modified not to affect the aluminum of air-
o 80) follow: cmi% and the heal transfer fluid, GS4* (Ref. 86), has been
1. ln~ended Use. Asctic-type antheze is intended for modified not to affect carbon steel, aluminum, or brass. Both
use in the coding system of liquid-cooled internal combus- of these fluids are nominally 50% by weight potassium ace-
tion engines to protect against freezing where the ambient tate plus corrosion inhibitors, and both have nominal specific
temperature remains close to AO”C (-40”F) for extended gravities of 1.275 at 20°C (68°F). Their freezing points at
periods of time but may drop as low as -68°C (-90°F). This their nominal composition are less than -SO*C (-58°F). ‘he
material may also be used as a heat transffir liquid for mili- runway deicer has an absolute viscosity of 10 rnpa-s (cP) at
tary applications where low temperatures are encountered. 20”C (68”F) and an absolute viscosity of 20 mpas (cP) at
2. Lirntirions. This material is designed to be used as O“C (32”F’). The heal transfer fluid, GS4m, has a typical
packaged and should never be diluted with water. absolute viscosity of 6.4 mpas (cP) at 20”C (68°F) and of
3. CcmsriruenrMmeriol. This compound is a premixed 12.3 mprrs (cP) at O°C (32”F). l%e E30 Liquid Runway
arctic grade antifreeze that consists of ethylene glycol, Deicer has been subjected to a spray test on a hot manifold;
water, various glycol ethers, and inhibitors. the solution produced no fire (Ref. 87).

3-4.2.2 MIL-A-46153, Antifreeze, Ethylene Gi?y- 3-4.3 FOG OIL

co~ Inhibited Heavy-Duty, Single Packuge With the change from DF-2 diesel fuel to JP-8 turbine
fuel in combat vehicles, the need for a special fluid in the
Pertinent data relative to MIL-A-46153 antifreeze (Ref.
VEESS of combat vehicles arose. These systems are used in
81) follow
the Ml MBT family, the BFVS, and the M60 MBT/M88
1. lnrended Use. Inhibited ethylene glycol antifreeze is
TRV family. When used with the VEE.SS, DF-2 produces
intended for use in the cooling system of liquid<ooled inter-
excellent smoke; JP-8, JP-5, and Jet A-1 do not. To date, the
nal combustion engines other than aircmft to protect against
best smoke-generating performance has come tim fog oil
&eezing in ambient temperatures as low as -48°C (-55”F)
per MIL-F-12070 (Ref. 88). Fog oil was compounded for
when diluted to 60% by adding water.’
use in US Army field smoke generators, which are used to
2. Lirnirazt”on.r.This material should not be nsed under

o , arctic conditions and should not be packaged in metal con-

tainers.
3. Constienr MurenaL This is a conventional anti-
obscure hrge temain features, e.g., to reduce observation by
the enemy in a valley during a river crossing. Boti the
smoke generator and the VEESS meter a spray of fog oil
into a ho~ flowing gas so that the fog oil vaporizes. This fog
freeze concentrme that contains ethylene glycol, water, and
oil condenses into a fog shortly after leaving the smoke gen-
inhibitors.
erator or the VEIN and becomes a dense, white cloud, that
persists near the ground for two or three minutes. Smoke is
3-4.23 Other Freeze Point Suppressants
formed from the heavier ends of the fuel blend, which can
Currently most freeze point suppressants used by the US be estimated from the distillation breakdown. (See Fig. 3-I.)
Army are ethylene glycol based. Ethylene glycol is both JP-8 has an end point of 258 to 284°C but does not generate
toxic and flammable and has a flash point of 1ll°C (232”F) smoke. COIWJS DF-2 has an end point of 370”C and pro-
and a net heat of combustion of 17.06 MJ/(kg”K) (7340 Bttd duces approximately 74.8% of the smoke of an equal vol-
(Ibm.’’F)). Ethylene glycol has an autogenous ignition tem- ume of fog oil (Ref. 28]. Fog oil starts neti the end of the
perarum (AJT) of 458°C (856W); a 50% solution of ethyl- DF-2 distillation trace, as shown on Fig. 3-1. The smoke
ene glycol in water has an AIT of 484°C (903”F). Because it produced by a mixture of fog oil and JP-8 was propm-ionate
is nontoxic, propylene glycol was selected as the freeze to the amount of fog oil in the mixture, i.e., the fueI added
point suppressan~ but its flash point is 99°C (210W, its nothing to the smoke produced. Therefore, the VEESS was
MT is 446°C (8353, and its net heat of combustion is redesigned to be separate from the fuel system of the vehi-
21.73 MJ/~K) (9350 Btu/(lbm.°F)) (Ref. 82). cle. A proposed system for the M 1 MBT would have one
In WOridWar II some German artillery pieces had a sohl- 39-L (lo-gal) tank containing fog oil mounted in the right
tion of water and potassium lactate as the recoil fluid (Ref. rear of the engine compartmen~
83). At presen~ the US Air Force is experimenting with cal- Fog oil consists of overhead petroleum fractions (hydro-
cium chloride as a freeze point suppressant in water used in a carbons extracted during the initial distillation as opposed to
fire extinguisher (Ref. 84). Another freeze point suppressant
thm is cwently used in a water-based airport runway deicer *Use of the trade name does not mean that the Government is
and as a Item transfer fluid for ground source heat pumps is endorsingthe prodnct-

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MIL-I+DBK-684
other late processes such as cracking) without additives; Almost all armored vehicles now mount grenade launch-
rerefined oils are prohibited. Fog oil has a minimum flash ers for quick-reaction smoke screens. These grenade
point of 160”C (320”F), a minimum kinematic viscosity of launchers &e usually mounted on the turret or superstruc- 9
3.40 mrn2/s or cSt at 40”C (-104°F) to a maximum of 4.17 ture of th~~lvehicle. The ammunition for these grenade
mm 2/s or cSt at IOO”C(212°F), ,and a pour point of -40”C launchers iy.usually located near the launchers.
(-40°F) maximum (Ref. 19). Ammumtion for the crew’s individual weapons is also
stowed wit$in the combat vehicle. Most of these individual
3-5 MUNITIONS weapons are used when the crewmen dismount to travel or
Munitions that are carried on combat vehicles are identi- fight on foot, but some vehicles have firing ports to permit
fied and the properties, flammability characteristics, and tie firing of these weapons ffom within the vehicle.
hazards are described in the following paragraphs. These Although most of these individual weapons use fixed car-
munitions are described in terms of their energetic contents, tridges, there can be hand grenades, light antitank weapons
(LAWS), medium antitank weapons (MAWS) such as the
i.e., propellants used in guns or in solid rocket motors; high
Dragon, an! mines (such as the Claymore). Hand grenades
explosives used in projectiles, charges; or other items; and
and weapon-launched grenades have high-explosive (HE)
other materials such as smoke, incendiaries, or flares.
or chemicd~ fillers. Mines are usually HE filled. LAWS and
If the main weapon is a high-velocity gun, the ammuni-
MAWS have both solid propellant rocket motors and high-
tion will usually be a fixed cartridge. The propellant charge
explosive ~tank (HEAT) warheads. On some occasions
is normally loose grains of propellant in a metallic-brass
bulk exploswes are canied on or in the vehicle. These
or steel--case or in a combustible case (e.g., the 152-mm
weapons ~~d ammunition should be available to the crew-
M409 high-explosive, antitank, tracer, multipurpose
men when $ey dismount.
(FIEAT-T-MP) cartridge), or the charge can be a compact
The h~~d presented by the energetic materials used in
r.iMssadhered to the projectile (referred to as “careless”).
the munlt20ps is primarily the potential for fire or explosion.
The metal-cased cartridge is usutdly the most rugged.
Also these materials can emit noxious or toxic fimes. It is
A lower velocity weapon, such as a howitzer, usually
generally acknowledged that most armored vehicles
uses either a semifixed cartridge or separate loading armnu-
destroyed b~eyondrecovery are those in which internal fires
nition. A semifixed cartridge has a projectile that can be
have caus~ the stowed munitions to explode.
removed from the case to enable a cannone~r to modify the Most combat vehicles carry as many munitions as can be
charge by removing or adding bags of propellant. The use of stowed wi~n and/or without. These munitions often con- 4
separate loading ammunition involves loading a projectile, a tin both a low explosive for launching the projectile and a
propellant charge, and a primer instead of a cartridge. There high exploiwe for obtaining the desired terminal effects.
is no case, but the propellant charge is usually transported The low e$plosive is either a gun propellant or a solid
within a metal tube. rocket mot~r propellant. The rocket motor propellants are
If the main weapon is a mortar, the round consists of a usually ne~-stoichiometric mixtures of fuels and oxidizers
projectile with a propellant charge attached either as muhi- and are uswdly quite sensitive to either ballistic impact or
layered wafers or in bags. This round comes in a travel pack heat. The &gh explosives are much more fiel-nch, and
and is removed shortly before firing. The travel pack can be most are less sensitive to kinetic energy impact or heat than
a cardboard or steel tube or a metal box. The charge is var- are the low; explosives. A small number of the high explo-
ied by removal of some of the wafers or bags. sives are sensitive to ballistic impact or heat; these are the
If the main weapon is a missile launcher, the ammunition primary explosives used to initiate the explosive trains in
is rocket-propelled. These rocket-propelled missiles usually the warhea+s or projectiles, These primary explosives, e.g.,
present the greatest challenge for nonhazardous stowage mercury fulininate, lead azide, and lead styphnate, are used
design. to convert a mechanical movement or an electric current
All of these types of rounds must be readily available for flow into ah explosion. Fortunately, these primary explo-
use in the weapon, and they must be stowed to minimize the sives occupj a very small volume and are usually embedded
hazard presented. The warheads can contain explosives, within the projectile. Explosion of the primary explosives
pyrophoric chemicids (such as white phosphorus or rnethyl- may have t! be amplified by a less sensitive explosive, such
aluminum), other chemicals (such as flares or smoke-gener- as pentaery@ritol tetranitrate (PETN) or Composition A5, in
ating mixtures), or can be inert. a booster to!assure initiation of the main charge. The princi-
Secondary weapons are usually machine guns or auto- ples of explosive behavior are covered in detail in AMCP
matic cannon. The’ arrirnunition for these weapons is nor- 706-180 (Ref. 89) and explosive trains are covered in
mally fixed. Most of these use metal-cased cartridges, but AMCP 704179 (Ref. 90). For the purposes of this hand-
some use caseless cartridges. Some vehicles have small cal- book, it m~st be realized that there are both low and high
iber mortars or automatic grenade launchers. Secondary explosives \within or on combat vehicles and that these
weapons are operated from within the vehicle. Ammunition explosives be capable of being ignited or initiated by either 4
,. should be readily available to the gunner. ballistic im$act or heat.
 Downloaded from http://www.everyspec.com

Low explosives are designed to function by burning at propellant charge, which is in a number of bags, caa be

o controlled rates. It is possibl% however, for Iow explosives

to bum at a much higher than desired rate, i.e., to deflagrate,
and some of these low explosives may even detonate. When
altenxl (zoned) for each specific round. After adjustment of
the propellant charge, the projectile is replaced. Separate
loading ammunition has three components: a projectile, a
such chemical reactions occur, the strength of the container propellant charge that often consists of several bags of pro-
for the explosive can be exceeded, sometimes catastrophi- pellan~ and a primer. These items are loaded individually
cally. On the other hand, high explosives are intended to into the weapon.
detonate but can dso burn S1OW1Y. The containers for these Brass, aluminum, or steel cases protect the propellant
high explosives usually are designed to fragment so that horn minor ignition sources. The steel case is slightly more
they cause maximum damage to nearby personnel ador resistant to span or llagment impact than the brass case, and
equipment. In some ballisdc impacts the low explosives both are more resistant than the aluminum case. GNen a
tend to deflagrate, whereas the high explosives often tend shaped-charge jet impact that will probably cause the pro-
either not to reactor simply to burn SIOW1y. High explosives pellant to defiagrate, however, the caruidge case can pro-
can burn initially and later deflagrate and then detonate; vide a number of large, rapidly moving I@ments, as shown
consequently, the designer should always design for the on Fig. 3-3. On the other hand, when a shaped-charge jet
worst case, i.e., detonation. perforated an ammunition can containing loose, brass-
Some of the energetic materials camied in combat vehi- cased, 5.56-mm cartridges, only the cartridges that were
cles are pyrotechnics. Since some pyrotechnics contain both struck by the jet exploded (Ref. 92).
oxidizer and he] in a near-stoichiomernc mixture, a strong There have been several efforts to reduce cartridge
ballistic impact mu result in combustion. weight and handling probiems. The 152-mm gdlauncher
used on theM551 Sheridan has fixed cartridges with a com-
3-5!.1 GUN AND SOLID ROCKET PROPEL- bustible case. The propellant is of loose grains within the
case. This cartridge has a number of problems. titially, the
Gun propellants used in munitions employed in combat case left burning residue in the chamber, but this problem
vehicle gun systems such as armor piercing (AP), HE, was solved. A rubber cover had to be placed over the case to
protect it from high humidityin Southeast Asiz and the case
rocket-assisted projectiles, and small ams ammunition for

0 crewmen’s individual and crew-served weapons are of three

general types. The propellants are single-base, double-base,
and rnple-b~ classification based on the number of
is prone to rupture when roughJy handled and spill propel-
lant grains in the vehicie.
A combustible case cartridge reduces cartridge weight
and eliminates the problem of a fired case cluttering the
explosive ingredients used in their fommdation. Single-base
crew space. The partially combustible-cased, 120-mm tank
propellants in general contain nitrocellulose as an explosive
gun catuidges for the M lA1 MBT illustrate improved char-
ingredien~ double-base propellants contain nitrocelltdose
acteristics; in these ctidges the problems that plague the
and rtitroglycmin, and uipk-base propellants contain nitro-
152-mm cartridge have been solved. l%ese cartridges con-
celltdos% nitroglycerin, and nitroguanidine. Usually triple-
sist of a metal case base and a combustible si&wail. The
base propellants are less susceptible to thermal, compres-
sional, and shock initiation than single- or double-base pro-
pellants. Additives control characteristics such as burning
tzue, flame temperahu% energy release rate, gas evolution,
deterioration as a function of temperature and time, vulnera-
btity, and ignition. Most solid propellants burn more rap-
idly when confined, i.e., higlmr pressure increases the burn
rate.
Gun ammunition can be handled as either fixed or semi-
fixed cartridges or as separate loading components. Freed
cartridges are those in which the propellant charge usually
has hose grains, is stadardizetL and cannot be changed for
a single round Examples of fixed cartridges are small anus
cartridges and combat vehicle gun cartridges up to 152 mm
or the combat engineer vehicle high-explosive plastic car-
tridge of 165 mm. Most often these cartridges have the pro
jectiie crimped or otherwise My fixed to the cartridge
case. Semilixed ammunition, such as that for the l(l%mm Figure 3-3. l(&nm Cartridge Case After De-
howitzer, has the projectile loosely inserted in the cartridge flagmtionofSolid PrQpdJant FflerPenetrated
case so that the projectile can be easily removed and the by a Shaped Charge (Ref. 91)

3-23
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MIL-HDBK-684 ;
propellant for Icinetic,energy (ICE) projectiles is granular propellants can be ignited by heating them above their kin-
and for HEAT projectiles is stick. dling temperature; propellants can also be ignited by explo-
Another concept still not fully developed is the caseless sive shock. fgnitions of these types in armored vehicles are
cartridges and the weapons to use them. The propellant of a usually cau~ed by ballistic attack involving projectile, frag-
caseless cartridge is molded solidly around the projectile. men~ span, !or shaped-charge jet impact. In these instances,
The binder on the outside of the propellant block is intended the impac~ng projectile, ilagment, or jet perforates the
to protect the propellant from moisture. This concept would stowage cornpartmen~ containers, cartridge cases, and pro-
eliminate tie combustible case itself and the potential prob- pellant charge. The extent of the openings caused by these
lem of spilling loose propellant grains in the vehicle. impacts determines whether the propellant is confined,
A third concept is to use a low-vulnerability propellant. semiconfined, or unconfined. The pressure and rate of bur-
This propellant could be either an insensitive solid propel- ninggenerated by the burning propellant are directly propor-
lant or an insensitive liquid gun propellant in which the tional to the degree of confinement. Some unconfined
charge needed for a particular round is metered into the propellants !burn slowly and can self-extinguish. Confined
breech by the gun computer. The insensitive solid propel- propellant can explode. Once a propellant that is a near-sto-
lant, probably a.plastic-bonded type, would be used as solid ichiometric $nixture of fiel and oxidizer is ignited, it is not
propellant is now. The liquid gun propellant would be car- easily extinguished. There has been considerable searching
ried in a special. container with appropriate plumbing to the for low-vulrnerability propellants.
gun. This system would be particularly effective for the cur- As previously mentioned, ignition occurs when the tem-
rent semifixed- or separate-loading-type weapons because it perature of;~ propellant at any point is raised to or above
would eliminate having unused bags of propellant cluttering its autoignition temperature. The converse is also true: The
the vehicle or gun site and would reduce the current large fire is exti~guished when the temperature of the burning
tonnage and volumetric requirements placed on the logistic propellant k reduced below its ignition temperature. This
system. The liquid gun propellant currently being consid- extinguishn$nt has been accomplished by Vargas et al
-ered by the US Army has been insensitive to a shaped- (Ref. 100)J who used a water deluge system, and by
charge jet perforation as long as the storage container has a Finnerty (Ref. 101), who used explosively launched water.
less th& critical diameter. Plastic-bonded solid propellant The water deluge system requires an enormous quantity of
has been much less sensitive to impact than explosive- water, and ~pnboard vehicle stowage of this water would
bonded propellant. Both of these subjects are discussed in cause an intolerable weight and volume penalty. Both Var-
jar. 4-6.3.
gas and Fi&erty were extinguishing fires in exposed pro-
Initially, rocket propellants were similar to gun propel-
pellant, not cased propellant. Ball (Ref. 102) more recently
kmts, and the rocket motors were designed to operate at
investigated a water injection system intended for the 120-
approximately 24 MPa (3500 psi) (Ref. 93). As perfor-
mm rounds] of the Leopard MBT. Ball’s system would use
mance requirements increased and the volume allowed for
considerably less water and would extinguish cased propel-
motors decrease~ however, more energetic propellants
lant fires. T
were formulated. In general, the more energetic the propel-
lant, the more sensitive it is to thermal and shock effects
3-5.2 FIIGH EXPLOSIVES
(Ref. 94). These types of propellants, some~es referred to
as composite propellants, are cast in place or extruded in a In mode+ combat vehicles explosives can be found in
single, large grain. The grain has a synthetic rubber-based or HE warheads stowed externally in boxes or internally in
plastic binder. bustles and ready racks. The HE warheads vary in size from
.Pertinent properties of typical propellants are given in 20-mm projectiles to 165-mm engineer demolition projec-
Table 3-11. Ml is a single-base, M2 is a double-base, and tiles or 203-mm HE projectiles. The quantity of HE for an
M15 and M30 are tiiple-base solid gun propellants. JA-2 individual warhead or projectile ranges ilom 0.01 kg of alu-
and diglycol rocket propellant (IXGL-RP) are German pro- minized RDX to greater than 16.5 kg of Composition B.
pellants used in the cartridges for the smoothbore 120-mm The various warheads use HE to produce fragments, blast,
tank gun. JA-2 is for the KE catr.idge and DIGL-RP is for and metallid jets for the defeat of armor systems, operating
the HEAT cartridge, even though it was initially a rocket systems, an! personnel. Explosives are also used in reactive
propellant. Both cartridges have combustible cases with a armor systems fastened externally to combat vehicles, e.g.,
metallic base. T5 and T8 are the older US rocket- or jet- Israeli Blazer armor. This reactive armor has proven vulner-
assisted takeoff bottle propellants, and M7 launch motor able to a strong incendiary (Ref. 103).
and the flight motor propellants (IMP) are newer US rocket Both kinetic energy and chemical energy threats can per-
propellants. Note that M7 and Fh4P are primarily high forate the armor of combat vehicles and the casings of high-
explosives with a low-explosive binder. explosive-filled warheads stowed either internally or exter-
The vulnerability or ignitability of propellants by external nally and c~ result in burning, deflagration, or detonation
sources is dependent on their ignition sensitivity. Basically, of these w~head fillers. If either detonation or deflagration

3-24
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c) o 0
TABLE 3-11, PERTINENT PROPERTIES OF SELECTED PROPELLANTS (Refs. 93, 95-99)
PROPERTY Ml M2 M15 M30 JA-2 DK3L-RP ‘I-5 “t% FMP M7
S’pccifict2ravity, 1.57 1,65 1.66 1.66 1.57 1,55
dimensionless
Isobaric Flame 2144 3046 2321 2767 3092 2868
Temperature, “C (’F) (3891) (55 15) (4 108) (5013) ‘ (5598) (5 194)
Heat of Combustion, 12.45 9.52
MJ/kg (13tu/lbm) (5354) (4094)
l-featof Explosion, 2,93-3.11 4.51-4.76 3.33-3.35 4.08 4.69 4.29 5.27 3.15 4.82 5.25
MJ/kg (EW/lbm) (1260- 1337) (1939-2047) (1432-1441) (1754) (2017) (1845) (2266) (1355) (1806) (1967)

COMPOS1TION
Nitrocellulose, % 84.2 75.55 20.0 28.0 59.5 62,5 57.5 58.0 35.0
Nitroglycerin, % 19.95 19.0 22.5 14.9 39,2 22.5
Nihcrgwmidine, % 54.7 47.7
RDx, 70 62.0
Oxidizer(s), % 2.5 0.05 0.05 1.5 z
Binder/Stabiliux, % I.75 25.55 37.45 1.0 y
1.8 3.3 I9,5 s
. Other, % 15.8 0.25 6.3 0.5 o
w
z
~
 Downloaded from http://www.everyspec.com

MIL-HDBK-684 ,
occurs, the end result could be disabling or catastrophic charge (the donor) against a variable stack of spacers (the
&unage to the vehicle and crew. Also the HE in nearby gap) to initiate the explosive being tested (the acceptor),
rounds could be initiated through “cook-off” by fires of the which is abutted against a witness plate. The detonation of 9
HE or. other fkurgnable fluids, and solids. If warheads are the acceptor is ascertained by the dentin the witness plate.
perforated and combustion occurs, serious tires, i.e., those The sensitivity of the acceptor explosive is inversely pro-
that last from milliseconds to minutes and ‘produce high portional to~the thickness of the gap, i.e., the thicker the gap,
thermal fluJc,fumes, blast, and noise, are the normal result. the more sensitive the explosive.
In addition, fragments produced by detona~on can cause
fratricide of other munitions through ignition of propellant 3-5.3 O&ER MUNITIONS
ch~ges or initiation of the projectile HE fillers. The primary munitions carried by combat vehicles
Pertinent properties of selected high explosives are given include antitank cartridges for the main guns, antitank mis-
in Table 3-12. The properties are those associated with fire siles such ,as the tube-launched, optically tracked, wire-
or explosion. The explosives are guided (TQ,W) missile, high-explosive artillery projectiles
1. Trinih-otoluene (TNT), Hexahydro-1,3,5 -trinitro- and propellant charges, and engineer demolition charges
l;3,5-triazine (~X), and Composition B (a mixture of 60.% fired from a 165-mm launcher. The antitank munitions can
RDX and 40% TNT), which represent the explosives used be either ldnetic energy or chemical energy. In addition to
in many HE warheads these primary munitions, other types of munitions are car-
2. Octol (a mixture of 75% octahydro- l,3,5,7-tetrani- ried in or on combat vehicles. These other munitions can be
tro- 1,3,5,7-tetrazocine (HMX) and 25% TNT) and LX-14 (a special p~ose rounds for the main armament such as
mixture of 95.5% EIMX and 4.5% Estane” 5702-F 1, a poly- smoke, incendiary, flares, or antipersormel rounds; muni-
urethane solution), which represent the fillers of some tions for individuals such as “small arms cartridges, hand
shaped-charge warheads grenades (i$cluding those for riot control), or LAWS; and
3. PBX 9404 (a plastic-bonded explosive (PBX) con- other items ~suchas antitank or antipersonnel mines, smoke
sisting of 9470 HMX, 3% nitrocellulose, and 3% tris- ~- projector c#tridges, distress flares, demolition charges, or
chloroethyl phosphate), DATJ3 (1,3-diamino-2,4,6-trini- incendiary ‘@enades for materiel destruction. The United
trobenzene), and TATB ( 1,3,5-triamino-2,4,6-trinitroben- States had ~some rnethylahnninum (TEA)-filled 66-mm
zene), which are representative of the newer impact- and rockets for ~se against bunkers in Vietnam, which could be
temperature-resistant explosives being developed in the carried in c~mbat vehicles if used again.
6
insensitive munitions programs. Most of $ese munitions contain propellant, either gun or
In addition to the thermal properties of selected high rocket, an~or high-explosive charges that, if hit, would
explosives, Table 3-12 also contains some data by which the react similirly to the primary munitions previously dis-
relative sensitivities to heat and impact or shock may be cussed. There are, however, other munition fillers that must
gaged. For the older explosives, such as TNT, Composition be considered. These fillers include pyrotechnics, combusti-
B, RDX, and I-IMX, Ref. 90 presents the temperature that ble metals or mixtures, to,~c ,c~emicals, and pyrophoric
would cause an explosion after a 5-s bake. Ref. 104 contains materials. :
an illustration from which the temperatures that would The pyrotechnics include smokes, flares, and incendiar-
cause an explosion after a 100-s bake at each temperature ies. The most common smoke used in munitions is white
can be estimated. While making these estimates, the author phosphorus (VW) loaded into large shells and hand gre-
of this handbook assumed that LX-14 would have the same nades. White phosphoms is pyrophoric and is a signaling or
reaction” to temperature as does LX-10 (Both contain screening agen~ it causes casualties by burning and can
approximately 95.570 HMX and 4.5% of a plastic binder, ignite combustibles. WP-filled shells must be stowed verti-
e.g., Viton A for LX-10 and Estane@ 5702-F1 for LX-14.) cally in a vehicle since WP melts at 44. 1°C; the shell filler
and that the reaction temperature of DA~ would be could melt pnd resolidify with an asymmetric shape that
approximately one-third of the way between those of TNT would affect exterior ballistics. The other smokes are used
and TA~ and would be closer to that of TNT. for screenin~ and signaling. Screening smoke, such as white
The relative impact sensitivities of the explosives men- or red phosphorus, burns to produce phosphorus pentoxide,
tioned may be gaged for the older explosives by the rifle which becomes droplets of phosphoric acid in moist air.
bullet test results (Ref. 90) and for all of them by the Los These smoke fillers are progressive burning solids that do
Alamos National Laboratory (LANL) small-scale gap test not require; added or atmospheric oxygen. EIexachloro-
results (Ref. 1W). The rifle bullet test consists of firing a ethane (HC) smoke produces an aerosol of zinc chloride.
caliber .30 ball M2 bullet at 853 mls (2800 fds) into 76-mm The HC smoke mixture is sensitive to an electrical spark, is
(3-in.) long, capped, steel pipes (51-mm (2-in.) inside diam- moderately ~impact sensitive, but is insensitive to friction
eter and 1.59 rmn (0.0625 in.) thick), containing the explo- and the mild shock of a Number 8 blasting cap (Ref. 106).
sive, and monitoring the reaction of the explosion. The The reaction of HC smoke being struck by a shaped-charge 9
LANL small-scale gap test consists of detonating a standwd jet is not recorded, but an interesting result was obtained in

3-26
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O TABLE 3=12. PERTINENT PROPERTM3$ OF EXPLOSIVES

0. (Refs. 90,93,104, and 10S)
o
PARAMETERS TNT COMPO$~ RDX OCTOL LX- 14 PBX 9404 DATB TATB
B-3 (60% RDX (75% HMX (95.5% HMX
40% TNT) 25% TNT) 4.5% Esmne~
Density, 1.654 1,75 1.806 1.843 1,849 1.865 1.837 1,938
‘1’MDSG
As Loaded SG

Method
m Pressed I
‘“72
I I
1.80-1,82

I
1.83

I
1.83-1.84

I
1.79 I.88

1.63-1,64
Melt Point, 80.9 79-80 205 79-80 >270 >250 286 >325
“c (“F) (178) (174- 176) (401)* (174- 176) (>5 18)* (>482)* (547) (>6 17)*
Heat of Combustion, 15.02-15.15 11.67**-1 1.8t 9,56* *-9,651 1I.20*$
MJ/kR (Btu/lbm) (6462-65 16) (5022-5076) (4 I 13-4152) (4817)
Heat of MJ/kg 4.52-5,9 5.19-6.44 5.36-6.78 6.57 6.59 6.53 5,27 5.02
Explosion, (cnlculrIlc(l)
(1.Nuflbm)
(1944-2533)
I (2232-277 1) (2304-291 7) (2826)
I (2835)
I (2809) I
(2267) (2160)

MJ/kg 4.56 5,02 6.32 5.77 4.10

(ext)wimcnta’
. .
Specific Heat, I.37 at 1.25 at 1.126at 1.13at 1.13al 0.962 at
y -Id/(kg*K) 20*C 25°C 25°C . 20”ctt 20”ctt 2t-jot**
to Thermal 0.260 at 0,262 at 0.106 0.439 al 0.432 ru 0.251
+
Conductivity, 18-45°C 25°C 25°C 21°C
W/(m.”C,)
Temperature 475 (887) 278 (532) 260 (500) 350 (662)
Causing Explosion
After 5s (Cook-off),
‘c (“P)
Temperature 280 (536) 197 (387) 207 (405) 257 (484) 255 (491) 290 (554)f 310 (590)
Causing Explosion (LX- 10)
After 100s Bake.
“c (“F) 1 t I 1 I I

Rifle Bullet Test. Exr)lodcd

. 40% I. 3% t00% 70% I
Parlinlly I3%
Exploded 1 1

13urncd 4% I I I
I
I
Unaffected 60% 80% 30%
Smtdi-Scale Gap 0.33 1.I-I.4 4,8-5.6 0.56-0.71 1,5-2.0 2.97 0.36 0.13
Test (LANL), mm
*decomposes TMD SCi = Theoreticalmaximumdensityspecificgravity
**experimental LANL = LosAlamasNntiormlLriborntory
‘calculated SG = specitlcgravity
‘teslimated
 Downloaded from http://www.everyspec.com

MIL-HDBK-6$4
Vietnam when a shaped-charge jet entered a smoke grenade 3-6 OT~R COIWBUSTIBLES
but did not exit. The other combustibles found on or in combat vehicles
Colored signal smokes are produced by heating a mixture include
to vaporize its components. A dye is included in the compo- 1. Elr$tric wiring insulation
nents to color the cloud formed. ‘l%eheat produced is rela- 2. Span and radiation liners
tively low since the smoke agent should sublimate below 3. Se#s
300QC (572”F). Currently, most combat vehicles carry 4. On~vehicle equipment (the impedimenta carried by
smoke grenades that are launched from tube arrays mounted the vehicle ~crewsand needed to maintain the vehicle and to
on the turret or equivalent and can provide a quick “smoke enable the crewmen to live in the field)
screen” to reduce the accuracy of hostile, direct-fire weap- 5. Paints and coatings
ons. The grenades are small screening smoke grenades, and 6. Miscellaneous combustibles, such as plastic or elas-
the grenade cartridges contain a small amount of propellant. tic components, bedrolls, camouflage nets, maps, docu-
Two types of grenades are currently used: a red phosphorus ments, rations, combustible metal parts, and other items.
grenade for visible obscuration (The red phosphorus is These other combustibles are usually more difficult to
pyrophonc and produces white smoke.) and a brass flake ignite than hydrocarbon fluids or explosives and are more
grenade for infrared (IR) obscuration. A third type of gre- difficult to extinguish than combustible fluids. Once ignited,
nade is being developed that will combine these two types
these items can smolder for a long time before flaming and,
of obscuration; the filler is a combination of brass flakes and while smoldering, often emit toxic gases. A smoldering
carbon fikiments (Ref. 107).
material is not extinguished by smothering with gaseous
Flares carried on or in combat vehicles include illumina-
extinguishing agents; it has to be cooled below the kindling
tion rounds (such as those fired from self-propelled artillery
temperature.
and mortars), signal flares, and road flares. In addition,
Also included as other combustibles are combustible
some vehicles may carry small trip or antipersonnel flares
metal items. Combustible metals, such as”magnesium and
used to protect positions at night. These flares are pyrotech-
lithium, present a very different problem. They are diflicult
nic devices that burn for a comparatively long time, i.e.,
to extinguish because the extinguishants used for other fires
seconds, and emit considerable light and heat. The predomin-
will not ext@guish these metals. The burning temperature of
ant fuel for flares is magnesium, but aluminum bm.salso
these metals is so high that the normal extinguishants
been used. The flare mixture contains sufficient oxidizer to
decompose) before extinguishing the fire. Further, the
consume the fuel.
decomposition products of the extinguishants used on the
An incendiary device that could be found within a com-
metals can be hazardous. These products can combust, even
bat vehicle is a thermite grenade, which could be used ,to
explode, or~are toxic. A different type of fire extinguisher is
destroy the engine, gun, or,some other critical component to
needed for @ese Class D combustibles that would not other-
prevent capture of combatworthy equipment. Such incendi-
wise be ins@lled on a combat vehicle.
ary devices could be ignited or initiated by ballistic impact ,.
and could serve as ignition sources or could burn or melt
3-6.1 EUECTRIC WIRING INSULATION
their way downward through the vehicle. Thennite grenades
cannot be extinguished. The com~tible components in an electrical wiring sys-
Antipersonnel rounds, such as the canister or flechette tem are tie, dielectric element (insulation) used to isolate
(beehive), would not have energetic contents more hazard- electrically the conductor from its surroundings, the paper
ous than the propellant. Small arms cartridges are not exces- wraps used,lin most multiconductor power cables, and the
sively hazardous when they ,are in brass, steel, or aluminum jacketing in:grouped cables. In most vehicles that require a
cases, but many caseless small arms camridges packed nun of bunched, jacketed cables, wrap material is not used
together without flame barriers between them could present and therefo~e is not discussed.
an explosion hazard. Grenades are liable to explode when Synthetic elastomers are used extensively as insulation
subjected to a sustained external fire. LAWS react to btlMis- and jacketigg components in electrical wiring systems.
tic impact, as do larger rocket-propeIled munitions, such as Most elastomers burn easily when not fire-retarded. Ethyl-
TOW missiles. Explosive charges or explosive-containing ene-propylene copolymers, chlorosulfonated polyethylene,
devices similar to the Claymore, antitank, or antipersonnel and silicones are widely used elastomers for electric wire
mines would react similaxly to other high-explosive-filled insulation. me incorporation of halogens either as an addi-
munitions. Also pyrotechnic-filled devices, such as smoke tive or as a jxu-tof a molecule has been used to decrease the
projector cartridges or dktress flares or fusees, would react flammability of elastomers. As a result, materials such as
similarly to larger pyrotechnic-filled munitions, A TEA- polychloropyene (neoprene), chlorinated polyolefins, epi-
filled warhead would react similarly to the pyrophoric WP- chlorohydrin rubbers, fluoro and chlorofluoro elastomers,
filled warhead, i.e., when the case is ruptured, the contents halogen-coritaining polyurethane, and various composi-
ignite and b~. tions incorporating halogenated additives ‘mefound in elec-

3-28
 Downloaded from http://www.everyspec.com

tic wire insulation mataial. These fire-retardant additives lene copolymer, and cross-linked pdyolefins. Additive sys-

o unfortunately are deficient in overall safety characteristics

bwwse they emit smoke and toxic halogen-containing
VilpO@ SUdl as hydrochloric and hydrochloric acid andkr
tems based on a combination of halogen compounds and
antimony oxide have been effective in reducing flammabil-
ity. These compositions do, however, burn readily in fidly
phosgene, when burned or exposed to intense heat. developed fires and emit toxic smoke, halogen acid fumes,
Phosphorous compounds have also been used to decrease and phosgene.
the flammability of wire insulation. In electric wire insula- 2 Polyvinyl chloride (PVC). Polyvinyl chloride does
tion elastomers the use of these compounds is limited to not burn under most normal conditions. When exposed to
plasticizal polyvinyl chloride andpolyurethane. Mamrials flame or excessive hew however, PVC emits hydrogen
that contain phosphorus as a fire retardant have slower chloride at a relatively low temperature in a highly endo-
flame propagation and are more difficult to ignite by small thermic reaction. This characteristic accounts for the intrin-
ignition sources, but they show little advantage over other sic low fkumnability of the uncompounded polymer. Ch.lon-
retardants when exposed to a higher heat flux. Phosphorus- nated and phosphorus-based tire-retardant additives are
containing elastomers also produce toxic organophosphmus used to reduce the flammability of the plasticized composi-
decomposition products when pyrolyzed- tion. ‘l%e phosphoms-containing composition produces
The incorporation of inorganic elements as part of the toxic organophosphorus decomposition products upon
polyner structure also significantly reduces the flame and pyrolysis.
smoke charaeteristica of the resulting elastomer. Silicone 3. Chlorinated d Chlorosuifonated Poiyethykne
elastomers and developmental phosphonitrilic elastomers (fiypalon). The flammability of this resin decreases directly
are examples of these materials. Fire retardancy is also with its chlotie content. Compositions containing up to
achieved by incorporating large amounts of inorganic filler 67% chlorine have been prepared Antimony oxi& reduces
into the elastomer. This additive reduces the fuel value of the amount of chlorine necessay to achieve the desired h
the composition. Most filled elastomers contain in excess of retardancy. The flammability characteristics closely resem-
50% inorganic particulate.
ble those of PVC, and hydrogen chloride is the major com-
bustion product along with toxic antimony-containing
S6.1.1 Elastomer Types
smoke and possibly phosgene.
3%e fire safeV characttistics of elastomers generally A list of insulations with their National Electrical
0 used for electrical insulation applications are largely deter-
rnird by their composition and may be classified into spe-
CodeQ* designation and application provisions is given in
Table 3-13.
cific categories:
Electrical installations in bilges, intercompartrnental pas-
1. CMonhe-Containing Elastomers. This group con-
sages, and ventilation or air-handling ducts should be made
tains polychloroprene, chlorinated ethylene polymers and
so that the spmd of fire or combustion products is not sub-
copolymers, and epichIorohydrin rubbers. These materials
stantial]y enhanced. Openings around electrical penetrations
have significantly better fire retardancy than the purely
through fire-resistant bulkheads shou~d be fire-stopped by
hydrocmbon rubb=, however, they generate large amounts
using approved methods.
of black smoke and hydrogen chloride (hydrochloric aci~
13CI)gas and possibly phosgene gas when exposed to large
3-6.13 TOXiC Effects
fires.
2. Fhmocarbon Elaomers. ‘l%ese elastomers are It is doubtful that the total mass of insulation present in
usually difficult to ignite and resist flame propagation. They vehicle wiring would constitute a significant fire hazard
generate significant toxic hazards, such as hydrofluoric acid, with respect to the heat released from its combustion. The
when exposed to intense fires. presence of toxic gases emitted due to fire, smoldering, or
3. Silicone Ekzwomers. Silicone elastomers generate pyrolysis effects, however, could cause considerable dis-
relatively little smoke, are ilre.retardan~ have a low fuel comfort.
value, and do not contain halogens. They are somewhat
deficient because their mechanical properties are marginal. 3-6.2 SPALLAND IUDIATION LINERS
Span Iiners are used to capture particles of armor that
3-6.1.2 ThIlltO@StiC -S break fkee and are projected within a combat vehicle by a
l’krnopkstic resins are also extensively used in wiring penetrator such as a KE projectile or a shaped-charge je~ or
insulation and jacketing. The predominantly used thermop- by the shock fkom a detonating warhead such as a ltigh-
lastics in these applications are pdyolefins, polyvinyl expIosive plastic (HEP), or by a nonarmor-perforating KE

0,,
chloride (PVC), and types of polyethylene described as fol-
lows: *NcuionalEkcrrical Code@ and NE@ are registered trademarks
1. Polyoiejins. The major polyoletkts used in electrical of the Nadonal Fke Protection Association, Inc., QuincY,iMA
imdation am high-density polyethylene, ethylene-propy- 02269.

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MIL-HDBK-684 !

TABLE 3-13. CONDUCTOR APPLICATION AND INSULATIONS (l?ef. 108)

MAXMUM QUTER @
TYPE OF TYPE OPERATING APPLICATIONI COVERING,
INSULATION CODE EMPERATURE PROVISIONS I INSULATION IF ANY
Fluorinated ethylene FEP 90°c Dry and damp locatio~ Fluorinated None
propylene (FEP) (194”F) I ethylene
~O;B propylene

200°c Dry locations-special Fluorinated Glass braid,

(392”F) applications* ethylene asbestos, or other
propylene suitable braid
material

Mineral insulation NH 90°c Dry and wet locations Magnesium oxide Copper or alloy steel
(Metal sheathed) (194°F)
250”C For special application*
(482”F) ,
Moisture-, heat-, and MTW7t 60”C Machine tool wiring in wet Flame-retardant, (A) None
oil-resistant (140”F) locations as permitted in moisture-, heat-,
thermoplastic NFPA 79** ~ and oil-resistant (B) Nylon jacket
thermoplastic equivalent
90”C Machine tool wiring in dry
(194°F) locations as permitted!in
NFPA 79** II
Paper 85°C For underground service Paper Lead sheath
(185”F) conductors or by special
p&mission
Perfluoroalkoxy PFA 90”C Dry and damp locations Perfluoroalkoxy None
(194”F) (
200”C Dry locations-special
(392°F) applications*
Perfluoroallcoxy PFAH 250”C Dry locations only. Okly Perfluoroalkoxy None
(482°F) for leads within apparatus or
within raceways connected
to apparatus. (Nickel or .
nickel-coated copper only)
Heat-resistant or 75°c Dry and damp locatiohs Heat-resistant or Moisture-resistant,
cross-linked synthetic (167°F) cross-linked flame-retardant, non-
polymer synthetic polymer metallic covering+
,,
Heat-resistant or 90”C Dry and damp locations
cross-linked synthetic (194”F)
polymer
Moisture- Md 75°c Dry and wet locations. Moisture- and Moisture-resistant.
heat-resistant or (167°F) Where over 2000V, i~ heat-resistant or flame-retardant, non-
cross-linked, syntheti insulation shall be ~ cross-linked metallic coveringt
polymer ozone-resistant : synthetic uolymer
Where environmentalconditionsrequire maximumconductoroperatingtemperaturesabove90”C
**Nation~ Fire ProtectionAssociationPublication79. SeeArticle670, Ref. 108.
‘Some rubber insulationsdo not requirean outercovering.
‘%sulation and outer coveringsthat meet the requirementsof flame-retardantand limitedsmokeand are so listed shallbe permittedto be
designatedlimited smoke with the suffix“M” after the codetype designation. “
‘ttListed wire types designatedwith the suffix“-2”, suchas RI-W-2,shall be permittedto be used at a continuous90°C-operating
temperature,wet or dry.
(cent’d on next page)
a

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MIL-HDBK-684

TX.BI.J!J 3-13. (cent’d)

o TYPE OF TYPE OPERATING APPLICATION

OUTER
COVERING,
INSULATION CODE tEMPERATURE PROVISIONS INSULATION IF ANY
Moisture- and RHW-2 90”C Dry and Wt2 k%LtiOtlS Moisture- and Moisture-resistanL
heat-resistant or (194T) heat-resistant or flame-rwardanL non-
cross-link~ syntheti[ cross-linked metallic covering~
polymer synthetic polymex
Silicone-asbestos SA 90°c Dry and damp locations Asbestos, glass, or
(194”F) other suitable braid
material
125°C For special application* Silicone rubber
(257°F)
Synthetic, sIsT~ 90°c Switchboard wiring only Heat-resistang None
heat-resistant (194”F) cross-linked,
synthetic Wlymel
ThLW.RO@StiC and TA 90°c Switchboard wiring only Thermoplastic am l%memardart~
asbestos (194”~ I asbestos nonmetallic covering
Thermoplastic and TBs 90”C Switchboard wiring only ‘thermoplastic Flame-retardant,
fibrous Otlter braid (194”F) I nonmetallic covering
Extended 250°c Dry locations only. Only ~Extruded None
polytetrafluom (482°F) foileads within a~ara& or Polytetratluom
ethylene within raceways comected ethylene
to apparatus or as.open wir-
ing. (IWckelor nickel-coated
comer only)

0 Heat-resistant
thermoplastic
THHNT~ 90”C
(194”F)
Dry and damp locations Flame-retardant,
heat-resistant
thermoplastic
Nylon jacket or
equivalent

Moisture- artd 75°C Wet location Flame-retardant, None

heat-resistant (167°F) moisture- and
thermoplastic 9(YC Dry location heat-resistant
(194°F) ~thertnopiastic
hfOiStUR- and -75°C Dry and wet locations ]Flame-retardan\ None
heat-resistant (167P’) moisture- and
thermoplastic 90°c Special applications within heat-resistant
(194”F9 electric discharge lighting thermoplastic
equipment. Limited to 1000
open-circuit volts or less.
(One size only, see
Ref. 108)
Wttere environmental conditions recmiremaximumconductoroperatingtemmmtmresabove90°C
‘Some tubber insulationsdo not reo&e an outer coverirw. - –
%sulatjon and outer coveringsthat-meetthe requireme&sof flame-retardantand limitedsmokeand are so listed shall be permittedto be
designatedlimitedsmoke with the suflix WAY’after the code type designation.
‘%sted wire types designatedwith the suf3ix“-2”,such as RHW-2,shallbe permittedto be used at a continuous9WCqeradng
ternperaturc,wet or dry.

,,
O,; (cent’d on next page)

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MIL-HDBK-684

TABLE 3-13. (cent’d)

MAXIMUM
TYPE OF TYPE 0PEI%4TING APPLICATION
INSULATION CODE IEMP13RATURE PROVISIONS,
Moisture- and THWNt~’~Tf 75°C Dry and wet locations
heat-resistant (167°F) j
heat-resistant
thermoplastic
thermoplastic I
60”C Dry and wet locations
(140°F)

Underground feeder 60°C

and branch-circuit (140°F)
cable—single ?sF See Article 339 of ~~ Moisture- and Integral with
conductor (For Type 75°C Ref. 108. heat-resistant insulation
UF cable employing (167”F**)
more than one
conductor, see
Mlcle 339 of Ref.
108.) 1

Underground USE’ ‘t 75°C See Article 338 of Heat- and IMoisture-resistant

service-entrance (167”F) Ref. 108. moisture-resistant nonmetallic covering
cable—single (See Section
conductor (For Type I 338-1 (b) of Ref.
USE cable employing “ 108.)
more than one
conductor, see I
Article 338 of Ref.
108.)
Heat-resistant. XHHt~ 90°c Dry and damp locations
!,
cross-linked, synthetic (194”F) II cross-linked, I
polymer
Moisture- and x~~?t,+t+ 90”C Dry and damp locations
heat-resistant, (194°F)
cross-linked, synthetic
polymer 75°c Wet locations ~
I (167”F)
**For ~Paci~ limitation,see Section339-5of ~if. 108.
‘t Insulationand outer coveringsthat meet the requirementsof flame-retardantand liniitedsmokeand are so listed shall be permittedto be
designatedlimited smokewith the suffix“/LS”afterthe codetype designation.
‘tt Listed wire t~es designatedwith the suffix“-2”, suchas RI-13V-2,
shall be permittedto be used at a continuous90”C-operating
temperature,wet or dry.

(cent’d on next page)

a

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MIL-HDBIW84

TABLE 3-13. (cent’d)

o TYPE OF TYPE
OUTER
COVERING,
INSULATION CODE llWULATION IF ANY
~
Mokture- and XHHW-2 9(YC Dry and wel klCMiOUS Flame-retardrmq None
heat-resistanL (194”F) Cross-links
cross-linked, synthetic synthetic polymer
F

T
9VC Dry and damp locations
(194W)
150°c Dry locations-special
(302”F) applications* ~

T
75°C Wet locations Modified ethylene None
(167°F) tetrafluoroethylene
90°c ~ and &lllp locations
(L94”F)

I 150”C
(302°F3
Dry locations-special
applkations*
*Whereenvironmentalconditionsrequire=-mum conductoroperadngmrtperamresabove 9LYC
i~s~ ~ ~ *igna~ Mm &e StiX ‘-2”, suchas RHW-~ shallbe permittedtObe Usedtita COntiIIUOUS
9WC-OpeIUtiDg
t~llltUre,
wet or dry.
-red with permissionhorn NFPA70-1993.the NuriorudEfecm”caiCode’. Copyright~ 199%NationalFue ProtectionAssociation
Quincy,MA02269. This repMted materialis not the completeand ofiicial positionof tie NationalFw ProtectionAssociationon the refer-
--subject, wbicb is repr&entedonly by tbe standard~ its entity,

projectile. This span Liner could be an uqboncied ballistic ing materials are usually embedded in the material used to
fabric curtain, such as the IsraeIis use in the Merkaw or a slow the fast neutrons, and the mixture is applied to the
0
“,
!,

bonded balkistic fabric panel, such as is used in the M113A3

APC and the M2A2 and M3A.2 BFVS. These span liners
inside surface of the armor or skin of the vehicle (Ref. 109).
This liner may be 5- to 76-trim (0.20- to 3.O-in.) thick and
also capture residual penetrator fragments after the initiaI may be bonded to the armor.
penetration and thus prevent their ricochet within the vehi- The hazards and problems associated with radiation liner
cle. These liners must be able to stop the span, and if the materials am rdated to rhe reactions of these materia?s to
liner is used for another purpose, it must have the properties fast neutron imp- the combusabtity or toxicity, and the
and strength needed for that task Materials that can be used mechanical properties of these materials. For exampIe,
for span curtains include Kevku@, ballistic nylon, and other metallic lithium and zirconium burn readily. Lithiuq
such fabrics. The binder materials include phenolic, poly- boron, and cadmium are toxic. Cadmium emits gamma radi-
ethylene, and polyurethane. ‘I%e penetrator will undoubt- ation when impacted by fast neutrons. l%e rare earth ele-
edly perforate the span liner at the initial entrance location. ments are expensive. Polyethylene does not bond readily
lle liner, either in the form of curtains or panels, should be and burns easily. Lead absorbs gamma radiation but passes
spaced at least 102 mm (4 in.) from the wall that am emit thermal neutrons.
span or preferably farther. This spacing allows the span to Where a thick, dense, elastic layer of material is applied
travel away from the penetrator trajectory so that the spali to the insi& surface of a monolithic atmor, span generation
will not pass through the hole the penetrator makes in the is inhibited. Thus a radiation liner may aIso serve as a span
liner. liner with resulting savings in “space or volume. Care must
Radiation liners are used to reduce the number of fast be taken to assure that the radiation liner does not “focus”
neutrons and amount of gamma radiation from a nuclear the span particles into a tighter pattern, i.e., act like the
detonation. Radiation liners contain materials that can slow choke on a sholgun. Care must also be taken to ensute that
fast neutrons and then trap them without generating more the materials are not in a toxic form and that they do not
neutrons or gamma radiation. Materials used to slow fast provide additional easily combustible materials or strong
neutrons are those with a large number of hydrogen atoms, ignition sources.
such as water, polyethylene and polyurethane. The materi-
als that excel at absorbing gamma radiation antilor slowing 3-6S SEATS
0
,’
thermal neutrons are hydrogen, lithium, boron, zirconium,
cadmium, lead, and some rare eanh elements. These absorb
Seat materials in a combat vehicle are among the most
significant of the “other” combustibles presen~ Further-

3-33
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MIL-HDBK-684
more, the covering and the interior foam or batting of the dering cigarettes, polyurethane foam ignites easily when
seats is more easily ignited than many other materials inside exposed to open flame. Its open cellular structure provides
the vehicle. Once ignited, seat materials may burn rapidly enormous surface area for combustion, and its chemical a
and produce heat, toxic products, and smoke. Seat materials componen~ liberate approximately 40% more heat than cel-
are also more difficult to extinguish than many other materi- Iulosic ma~eri~ like wood, paper, or cotton. Fabrics and
als. interior materials that char include cotton, wool, and poly-
Seats are a composite product. They are composed of an isocyanate. ‘lFabricsand paddings that are more fire-resistant
II.
exterior fabric covering and an interior mass comprised of include po$mn.ide, neoprene foam, and polyvinyl chloride.
flexible foam or batting or ,both. The composition of the The presende of a fire-blocking layer between the fabric and
exterior fabric is the main determinant of the relative flam- intenor of !a seat composite adds measurably to the fire
mability of the overall composite. Thus a selected seat foam resistance bf the entire composite. When used as a fire-
material covered by heavy PVC is less likely to ignite and blocking layer, flame-retardant cotton or a fabric backed
spread flame than that same material covered by cotton, with aluminum foil can markedly improve resistance to cig-
rayon, or polyester fabric. If the seat covering is’ ruptured arettes and Ismall, open flames. Flame retardants applied to
and the interior is exposed, however, the flammability of the polyurethane cushioning can provide significant protection
interior material may dominate the fire. against smiill flame sources such as matches. Such retar-
The nature of the ignition source is critical to whether or dants, however, may evaporate over time and thus would be
not a given seat composite will ignite and burn. Possible less effective. In a large fire, retardants may be cooked out
ignition sources include electrical shorts, hot surfaces and produie disabling irritants and/or increase smoke.
(including cigarettes and metal fragments), slowly burning Addition of a flame retardant to an ordinarily flammable
fuels (including any flammable liquids), other burning com- material is often insufficient to classify that material as
bustibles (including debris, paper, and fabrics), and rapid- “highly resistant” to ignition.
burning combustibles such as hydrocarbon fluid sprays and In the presence of electrical shorts or hot surface ignition
munitions. sources, fa~ric coverings that melt away from the heat will
Fabric coverings and interior foam or batting materials generaliy not ignite. (See Table 3-14.) The intenor material,
may each be classified into three categories based on their however, i~~hen exposed to the ignition source. If the inte-
response to heat or ffame: (1) those that melt, (2) those that rior materi$ is also prone to melting, smoldering combus-
char, and (3) those that are highly resistant to ignition and tion, i.e., self-propagating thermal decomposition, may
c
generally do not melt. Each of these categories must be con- occur. Aith~ugh smoldering is less immediately life threat-
sidered in view of the most likely ignition sources. Table 3- ening than flaming, it can produce toxic fumes and is ve~
14 summ~zes the behavior of the various types of fabric difficult to extinguish. Furthermore, continued smoldering
coverings and interior seat materials when presented with in the inteti~r of a foam or batting may lead to sudden flam-
the ignition sources indicated. ing combus~on.
Examples of fabrics amd interior materials that melt are Fabrics ~t char may smolder when in contact with elec-
polyester, polyolefin, and polyurethane. Polyurethane foam trical short? or hot surface ignition sources. This charring
is widely used as a cushioning material in residential and may protect the interior materials for a short time better than
commercial furniture. Although not readily ignited by smol- melting fabrics; however, continued smoldering, e.g., cotton
1
T~LE 3-14. FIRE HAZARD ~F SEATS
IGNITION $OURCB
CHARACTERISTIC
RESPONSE TO FIRE ELECTRICAL OR FUEL OR OTHER
HOT SURFACE COMB~~TIBLES RAPID (EXPLOSIVE)
Fabxics that
Melt Melt, no ignition Melt, burn ,, Burn, spread
Char Smolder Burn slowly ~ Less spread, postsmolder
Resist fres Should not ignite Burn if ignit+m Least spread
source hot enough
Interior materials that
Melt Smolder Burn, melt and flow Burn, spread molten drops
Char Smolder Burn more sl$wly Less spread, smolder
Resist f~es Acceptable if smolder resistant Acceptable i$:resistant to Least spread 9
open flame I

3-34
$
 Downloaded from http://www.everyspec.com

,, fabrics, may result in flaming combustion. Interior matexitls

that char will also smolder. Char-forming materials often
substrates, from reaching ignition temperature is paints and
coatings. Combat vehicles are also painted to provide cam-
O evolve carbon monoxide, an odorless, toxic gas.
Generally, fabrics that are highly fire-resistant will not
ouflage and chemical warfare agent resistance. l%e most
common fire-retardant coatings are intumescent (i.e., swells
ignite fimm electricrd shorts or hot surfaces. Similariy, inte- and chars when exposed to flame) or fire-retardan~ nonintu-
rior materials that are fire-resistant will generally not ignite mescent types.
as a result of these ignition sources. Smoldetig combus-
tion, however, can continue for vmy long periods even in 3-6.5.1 Nottinttunescent Coatings
fire-resistantmaterials, uniess they are designed to be smol- Although fi-retardan~ nonintumescent coatings do not
der resistant. provide the same degree of tie protection to the underlying
Fires due to fueIs or other combustibles have sirndar surface as intumescent coatings, they are useful in vehicles
effects on seat composites; these fires differ only in the rela-
that are repeatedly painted to provide protection to the sur-
tive intensity of the tire as an ignition source. As fabrics
face or to enhance or camouflage their appearam. ‘Ibe
melq they withdraw tim these ignition sources and expose
paints constitute a fire hazard regardless of the nature of the
the interior mamial. If the fabric melts and flows into the
underlying surface as layers of conventional paints build up.
region of the initiaI lire, however, the molten material con-
Fire-retardant coatings are formulated to resist flaming even
tributes substantially to the fire. Interior materials that melt
when heavy layers of paint are exposed to dre. Flame-retar-
will likely bum and spread the fire even beyond the original
dant additives do not render these coatings nonflammable;
source.
they raise the kindling temperature (the temperature at
Char-forming fabrics and highly flame-resistant fabrics
which solids will ignite). Once the flame-retardant coating
may offer some protection to seat composites fkom flaming
does ignite, it can burn hotter and usually emits more toxic
ignition sources and are less likely to expose the interior
matetial. la the same manner, char-forming and highly fire- or noxious ties than the same coating without the flame-
resistant interior materials may be less likely to ignite and retardant additive. A description of these coatings follows
contribute to the fire. Most materials will bum, however, if 1. Alkyd Cbaiing$. The most commonly used iire-
the intensity of the ignition source is “sufficientlyhigh. resistant paints are based on chlorinated allqds. These
In the case of rapid ignition, possibly with explosive paints use chlorinated diacids or anhydrides. Halogenated
additives have been used in iire-retardant coatings because
0
,’ force, the materials that melt would create the greatest haz-
ard because they would ignite and spread the fire with fram-
ing, molten droplets. The char-forming materials would
of their low cost and minimal effect on the basic paint pm~
erties when used in conjunction with metal oxides. Inert
have less timdency to spread, but they may continue to mineral fillers are also used to reduce the flamiability of
smolder long after the initial ignition source is extinguished. the coating. ‘l%e percentage of fillers in the paint must be
high in order to raise the ignition point of the organic mate-
3-6.4 ON-VEHICLE EQUIPMENT (OVE) rial in the paint to desired levels.
In general, much of the OVE in combat vehicles is metal, 2. Other Polymem. Coatings based on epoxy resins
e.g., took or combat weapons, and therefore is not subject and urethane are widely used on US combat vehicles
to the usual concerns about fire safety. Items that should be because of the chemical agent resistance they provide. Coat-
consi&red possible contributors to a fire include, but are not ings based on melnmine/foxrnaldehyde and phenol/formal-
to be limited to, maintenance and repair tools with wooden dehyde resins ate used as somewhat ablative, char-forming
or plastic handles, canvas or nylon straps, plasdc instrument coatings.
cases, plastic ammunition boxe% nonmetal brushes, tarpau-
lin and camouflage nets, books (manuals) and papers (e.g., 3-6.5Q I.ntumescent Coatings
drawings), sleeping bags, field packs, and cloth flags. These Wlten subjected to a significant level of h- intumescent
items do not constitute a major portion of the possible flam- coatings undergo charring and expand from a thin paint film
mab~e items onboard a vehicle. Furthermore, they are not to a thiclG puffy coating with a low thermal conductivity.
easily ignited nor do they readily bum. If glowing, they The resultant pu~ coating can insulate the underlying sub-
couldprovidelong-termignitionsourcesandserveto reig- strate fkom hea~ exclude oxygen horn the substrate, pro-
nitemore combustible items. duce di.luent nonflammable gases, and reduce the
Illustrations of the items carried in and on a typicaI comb- production of flammable combustion products. The
at vehicle are shown on Fig. 3-4. Note that the individual expanded coating retains its effectiveness until it is broken
weapons and stowed ammunition are included. up by extremely high heat or erosion. These coatings protect
nonfhmmable substrates, such as metals, by reducing the
3-6.S PAINT’S AND COATINGS transfer of heat to them. The char does not resist abrasion. A
0 One of the oldest methods used to protect the underlying
substrate tim corrosion, wear, or, in the case of flammable
successful fire survivabWy enhancement application of
intumescent coating is described in subpar. 4-8.4.2.

3-35
 Downloaded from http://www.everyspec.com

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(A) Right Interior Stowage

Figure 3-4. CFV M3A0 Stowage Diagram

(cent’don next page)

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Stowage
I?igure 3=4. (cent’d)
(cent’don next page)
 Downloaded from http://www.everyspec.com

4 Signala,M128AI
Illuminatkrn

F%rsonnal Heater 3 Rifles,5.56.mm r /’- ::::2,??:

M16AI
Binoatlaf M17A1
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for M203, M406
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(C) Top View, Interior Stowage

Figure 3-4. (eont’d)

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MIL-HDBK484

o
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(E) Rear View of Turret Shield and Partial View

of Turret Interior

Figure 3-4. (cent’d)

(cent’d on next psge)

3-39
 Downloaded from http://www.everyspec.com

MIL-HDBK-684

37.62-nmn
AmmunitionBoxes
12 .tia._\y

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Inturnescent comings contain several ingredients neces- 3-6.6.1 Ji@Xonters, Plastics, Fire-Retardant
sary to cause intumescent action, A catalyst is used to trig- Additives, and Fillers
ger tie first of several reactions occurring in the coating. A Plastics qnd elastome~ are widely used in military vehi-
carbon-forming compound reacts with the catalyst to forma cles. These polymeric synthetic materials and natural rubber
cmbon residue. A gas-forming compound decomposes and pose a serious health hazard when they burn in a vehicular
causes the carbon char to foam into a protective layer. A tire. Some materials are more hazardous than others when
resin binder forms a skin over. the foam and traps the gases burned. l?ire-retardant additives can be incorporated within
in the ch,ar layer. Many intumescent coatings have draw- the polymeric matrix of the material to reduce the ignitabil-
backs such as poor aging, poor humidity resistance, lack of ity of the dxture. These tire retardants increase the specific
flexibility, and high cost. I.ntumescent coatings release more
heat of the mixture and thus increase the amount of heat
noxious times than most nonintumescent coatings. Intu-
necessary to raise the temperature of the mixture to the kin-
mescent coatings are normally used in unoccupied compart-
dling temperature of the combustible component. These fire
ments.
retardants c’~ also pose a serious health hazard when the
The amount of fuel in paints and coatings is relatively
material bu$ts. Some fire retardants can release toxic prod-
small. The ability of a finish material to resist the spread of
ucts when the base material bums. Others can break down
flame is determined by the ASTM E 84 test. (Ref. 110)‘A
into toxic components when subjected to heat. FNers and
flame spread rating of 25 or less is desirable. An assessment
extenders tie also normally incorporated into the polymeric
of the toxic effect of the smoke developed from exposure of
matrix. The~ fillers can be released into the atmosphere as
a paint or coating to fire must be supplied by the manufac-
the polymeq burns and the resultant char is disturbed. Some
turer of the material upon request.
of the fillers are combustible and most are harmful upon
inhalation. A list of the properties of the combustible mate-
3-6.6 MISCELLANEOUS COMBUSTIBLES
rials, including some noncombustible fillers used in military
Miscellaneous combustibles include plastics, elastomers,.
vehicles, is ~iven in Table 3-15.
textiles, paper, mash, debris, combustible metals, and any
other item not already covered that is located on or in a
combat vehicle and can bum.

3-40
 Downloaded from http://www.everyspec.com

c) o c)
TABLE 3-15. PROPERTIES (X? PLASTIC AND ELASTIC MATERIALS INCLUDING FILLERS AND
I?IRE-RETARDANTADDITIVES (Refs. 111-116)
:OWFICIENT OF
SPECIFIC 1W3RMAL SPECIFIC AUTOIGNITION
THERMAL FLAMMABILITY
MATERIALS GRAVITY,
CONDUCTIVITY,
EXPANSION,
HEAT,
ASTM D 635, TEMPERATURE,
W/(m.K) J/kg.K
dimensionless [Blu/(tl. ft’wft)]
●
“-srn/m.K
(Btu/lbrn°F)
mm/min (in./min) “c (“F)
,- l:.. On\
ELAsm.s
Acctal I.4-1,5 0.22 (o! 13) 3.61-8.1 (2.0-4.5) 1465 (0.35) 27.9 (1.1) 232 (450)
Acrylic 1.18 0,2 I (0. 12) 8. I (4.5) 1465 (0.35) 13.0-55,9 (0,5 1-2.2) 293 (560)
Alkyd 2.50-2.15 ‘!O5-O.1O (0+03-0.06 1,8-5.4 (1.0-3.0) 1047 (0,25) self-ext* self-exl 260 (500)
Allyl Ester 1.32 0,2 i (o. 12) 10.8 (6.0) 1256 (0.3) (0,35) 260 (500)
Cellulose 13ster I ,3 0.17-0.35 (0,1-0.2) 7.7-15.5 (4.3-8.6) 1256-1758 (0.3-0.42) 13.::?0.8 (0.51-2.0) 143 (290)
Chlorinated Polyalkene Este! 1.4 0.14 (0.08) 1I.9 (6.6) 1047 (0.25) self-ext self-ext 260 (500)
C.yanatcs/Cyanimides 1,4 0.21 (o. 12) 3.6 (2.0) 1675 (0.4) slow burn slow burn 232 (450)
Epoxy [Expoximidc) 1.15 0.69 (0.4) 1I.2 (6.2) 1675 (0.4) variable variaMc 232-288 (450-550)
Epoxy (Bromirmted 1.22 0.21 (o. 12) 3. 1-5.4(1 .7-3.0) 1465 (0.35) self-ext slow to self- 260 (500)
Cyclonalphatic) ext
Furan 1.2 0.21(0. 12) 5,4 (3.0) 1675 (0.4) slow slow 260 (500) ~
Melnmine 1.48 0.21 (o. 12) 3.6 (2.0) 1675 (0.4) self-exl self-ext 327-341 (620-645) ~
Ureaform Aldehyde 1.5 0.35 (0.20) 2.7 (1,5) 1675 (0.4) self-ext Self-cxt 149 (300) k
g Casein I .2 0.21 (o. 12) 3.6 (2.0) 1675 (0.4) low to self- slow to sclf- 177 (350) ~
ext ext
Poly (bis-maleimide) I.4 0.35 (0.20) 5.4 (3.0) i 130 (0.27) self-ext self-ext 260 (500) z
Polyalkene Ethers 0.9 0.17(0.10) 11.7 (6,5) 1968 (0.47) 7.9-13.0 (0.31-0.51) 204 (400) ~
Polyamide 1.14 0.17(0; 10) 8.6 (4.8) 1675 (0.40) self-ext self-ext 218-282 (425-540)
Polyarylene Ether 1.0 0.17(0.10) 3.6 (2.0) 1675 (0.4) 9,4-24.9 (0.37-0.98) 204 (400)
Polybutadiene 1.1 0.2 i (0:12) 5.4 (3.0) 1675 (0,4) 24.9-38.1 (0.98-1.5) 243 (470)
Polybutylene 0.91 0,22 (0, 13) 12.8 (7.1) 1675 (0.4) 24.9-38.1 (0.98-1.5) 204 (400)
Polycwbonate 1.20 0,19(0.11) 6.8 (3.8) 1256 (0.30) self-cxt self-exl 271 (520)
Polyester (saturated) 1.31 0.17(0.10) 9.5 (5.3) 1675-2512 (0.4-0,6) slow slow 249 (480)
Polyester (unsaturated) 1.12-I.46 0.19(0.11) 6.8-10.6 (3.8-5.9) 1382-2303 (0.33-0.55 elf-ext-22.9 (self-ext-O.9 249 (480)
Polyethylene (C- 1) 0.91-0.93 0.35 (0.20) 6.0-19.6 (8.9-10.9 2219-2303 (0.53-0.55 63,5 (2.5) 177 (350)
Polyfluorocarbon FGR 2.14-2.17 0.21 (o. 12) 5.1-18,9 (8,4-10,5 1172 (0.28) INlq 288 (550)
Perftuoroalkoxy (PFA) 2,14-2.17 0.26 (0. 15) 23.4 (13.0) 1047 (0.25) HW INF 288 (550)
*ex( = extinguish
tlNP = inflammable
(cent’don next page)
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TABLE 3-15. (COIBt’d)

COEFFICIENT 01
SPECIFIC THERMAL SPECIFIC
THE~AL FLAMMABILITY AUTOIGNITfON
MATERIALS CONDUCTIVITY, HEAT,
GRAVITY, EXPANSION, ASTM D 635, TEMPERATURE,
W/(mK) J/kg.K
dimensionless 10-5mlmK mm/min (in./min) “C (“F)
[Btu/(h. ft 2.0F/ft)] (Btu/lbm.°F)
( 10-5in./in..0F)
PLASTICS (continued)
Polytrifluoro chloroethylem 2.10-2.15 0s26 (0.15) 7.0 (3.9) 921 (0.22) nwq’ INF 288 (550)
(PTFCE)
Polytetrafluoroethylene 2.10-2.30 0.24 (0.14) 9.9 (5.5) 1047 (0.25) INF INF 277 (530)
(PTFE)
Polyvinylidene Fluoride 1.78 0.17 (0.10) 12.1 (6.7) 963 (0.23) self-ext self-ext 288 (5s0)
(PVF)
Polyvinylidene Fluoride 1.77 0,24 (0,14) 15.3 (8.5) 1382 (0.33) INl? INF 288 (550j
(PVF,)
Polyimide 1.42 0.35 (0,20) 5.0 (2.8) 1130 (0.27) self-ext self-ext >343 (>650)
Polyphenylene Sulfide 1.90 0.35 (0.20) 1.8-3.6 (1.0-2.0) 1465 (0.35) self-ext self-ext 288 (550)
Casein-Aldehyde 1.1 0.21 (0.12) 3.6 (2.0) 1675 (0.4) slow slow 149 (300)
Phenolics 1.36 0.21 (0.12) 3.1-4.7 (1.7-2.6) 1465 (0.35) self-ext self-ext 271 (520)
Polypropylene 0.9-0.91 )s17-0.19 (0.10-0.11) 6.8-10.4 (3.8-5.8) 1884 (.45) 18.0-25.4 (0.71-1.0) 199-210 (390-410)
Polystyrene 1.04 ).10-0. 17 (0.06-0. 10) 5.9-8.6 (3.3-4.8) 256-1465 (0.30-0.35 ~5.4-38rl (lo@l.5) 254 (490)
w Polysulfone 1.24 7.4 (4.3) 5.6 (3.1) 1005 (0.24) Self-ext self-ext 232 (450)
L
w Polyurethane 1.12-1.22 0.24 (0.14) 16.9 (9.4) 1717 (0.41) 216 (420)
Polyvinylacetate 1.19 0.14 (0.8) 14.2 (7.9) 1675 (0.4) 232 (450)
Polyvinyl Chloride (PVC) 1.2- I.55 ).12-0. 17 (0.07-0.10) 16.2 (9.0) 1256 (0.3) self-ext self-ext 235 (455)
PVC-Vinyldene Chloride 1,68-1.75 0.10 (0.06) 16.0 (8.9) 1340 (0.32) self-ext self-ext >277 (>530)
., ...ELASTOMERS . -.
Natural Rubber ‘0.93 0.14 (0.08) 66.6 (37.0) 1675 (0.4) 25.4-76.2 (1.0-3.0)
Butyl Rtt 0.90 0.10 (0.06) 57.6 (32.0) 1675 (0.4) 25,4-76.2 (1.0-3.0)
Nitrile R 0,98 0.24 (0.14) 70.2 (39.0) 1465 (0.35) 12.7-38.1 (0.5-1.5)
Styrene Butadiene R 0.94 0.24 (0.14) 66.6 (37.0) 1675 (0.4) 25.4-50.8 (1.0-2,0)
Polyurethane R 1.25 0.22 (0.13) 36.0 (20.0) 1675 (0.4) 25.4-50.8 (1.0-2,0) 216 (420)
Acrylic R 1.09 0.22 (0.13) 36.0 (20.0) 1675 (0.4) 25.4-50.8 (1.0-2.0)
Silicone R 1.1-1.6 0.22 (0.13) 81.0 (45.0) 1675 (0.4) 2.5-12.7 (O.1-0.5) !88-296 (550-565)
Polyester R 1.16-1.27 0.24 (0.14) 36.0 (20.0) 2093 (0.5) 25.4-38.1 (1,0-1.5)
Ethylene Propylene R 0.90 0.22 (0.13) 36.0 (20.0) 1675 (0.4) 25.4-76.2 (1.0-3.0)
EPDM R 0.86 0.22 (0. 13) 36.0 (20.0) 1675 (0.4) 25.4-76.2 (1.0-3.0)
Isoprene R 0.93 0.22(0,13) 66.6 (37.0) 1675 (0.4) 25.4-76.2 (1.0-3.0)
Polysulfide R 1.35 0.22 (0.13) 36.0 (20.0) 1675 (0.4) 12.7-38.1 (0.5-1,5)
tINF = inflammable
‘tl? s rubber
(cent’d on next page)
 Downloaded from http://www.everyspec.com

O 0 0
TAN.]] 3-15. (cent’d)
COEFFICIENT OF
SPECIFIC THERMAL THERMAL sP13clFrc FLAMMABILITY AUTOIGNITION

ELLJa3s
MATERIALS

Silica (SiOz)
GRAVITY,
Iimcnsionlcs

2,2-2.6
3NDUCT1WTY,
W/(m.K)
Btu/(h.fIz,oWft)]

12,1 (7.0)
13XPANS10N,
10-sndmK
( 10-sin,/in,.OF)

0.05 (0.03)
HEAT,
J/kg,K
(13tu/lbm.017)

837-1256 (0.2-0.3)
ASTM D 635,
mndmin (in,/min)
b
MIWRATURE,
“c (“F)

Silicates 2.1-2.5 L3-6,9 (2,5-4.0) 0,34-0.4 I (0, 19-0,23: 837 (0.2)

Calcite (CaO) 2.7 7.1 (4.1) 1.4 (0.76) 837 (0.2)
Gypsum 2.97 6.9 (4.0) 1,1-1,4 (0.6-0.8) 837 (0.2)
‘rilttnium Oxide (’ri02) 3.9-4.2 ,9-10,4 (4.0-6.0) 0.02 (0.ol ) 754-879 (O.18-0,21)
Tnlc 2,7-2.8 ?.6-3,3 (1.5- 1.9) 0.58-0.72 (0.32-0.40 837-921 (0.2-0.22)
clay 2.0-2.5 6.1 (3.5) 48.6-57.6 (27.0-32.0 754-837 (O.18-0.20)
Alumina (A1103) 3.4-3.9 O-36.9 (13,3-21.3) 0.36-0.41 (0.20-0.23: 837 (0.2)
Aluminntcs 3.7-4. I ).4- 13.8 (6.0-8.0) <0.02 (<,01) 1047 (0.25)
Fly Ash 2.5-4.0 ).4- 13.8 (6.0-8.0) <0.36 (<0.2) 837-1256 (0.2-0.3)
Rice Hull Ash 2.5-4.0 ).4- 13.8 (6.0-8.0) <0.36 (<0,2) 837-1256 (0,2-0,3)
Carbon Black 1.8-2.1 $.2-8.7 (3.0-5.0) 0.23-0,29 (0, 13-0.16 754 (O.18) 7.6-25.4 (0,3- 1.0)
Graphite 2,0-2,3 5-164.4 (65.0-95.0 D.13-0.3 I (0.07-0. 17: 754 (O.18) 7.6-25.4 (0,3- 1,0)
Asbestos 2.2-2.5 !.1-2.9 (1.2- 1.7) 0.54-0.79 (0,30-0,44: 837 (0.2)
g Fiberglass 2.2 .5-12.1 (2.0-7.0) 0.32-0.36 (O.18-0.20 837-1256 (0.2-0,3)
.——
Graphi[e Fiber 1,5-1,9 5-86.5 (2.0-50.0) 0.36-0.74 (0.2-0.4 1) 837 (0.2) 7.6-25.4 (0,3-1.0)
Ceramic Fiber 3.0-3.3 $.2-6.I (3.0-3,5) <0.02 (<0.01 ) 837 (0.2)
Nylon Fiber 1,14 0.17(0,10) 8.6 (4.8) 1675 (0.40) 7.6-25.4 (0.3- 1.0)
Alkyd Fiber 2.1 .52- 1.0 (0.3-0.6) 1.8-5,4 (1.0-3.0) 1047 (0.25) 12.7-50.8 (0.5-2.0)
Imide Fiber I.4 0.35 (0!20) 3.6 (2.0) 1130 (0.27) 12.7-25.4 (0,5- 1.0)
Iron 7.9 60.6 (35.0) 1.4 (0.75) 461 (0.11)
Aluminum 2.7 233.6(135.0) 2.2-2.5 (1 .2-1.4) 963 (0.23)
FIRE-~RDANr ADDITIV~
Aluminum Hydroxide 2.42 1193 (0.28) o
Antimony Tr~oxidc 5.2-5.7 347 (0.08) 0
Sodium Borate Decahydratc 1.73 1611 (0.038) 0
Sodium Borate Penttthydrate 1.815 0
Zinc Borate 3.1-3.64 0
(cent’d on next page)
 Downloaded from http://www.everyspec.com

TABLE 3-15. (cent’d)

THERMAL COEFFICIENT OF
SPECIFIC THERMAL SPECIFIC
CONDUCTIVITY, FLAMMABILITY AUTOIGNITION
MATERIALS GRAVITY, EXPANSION, HEAT,
W/(m.K) ASTM D 635, ~MPERATURE,
dimensionless 10-5m/mK J/kg,K
[Btu/(h.”ft2OF/ft)] (Btu/lbm°F) mmhin (in,/min) “C (“F)
( 10-3in./in..00’0
FIRE-RETARDANT ADDITIVES
(continued)
Disodium Phosphate 1.5-2.0 o
Sodium Silicate Hydrate. 0
Magnesium Phosphate 1.73 0
Magnesium Silicate 0
Dibromoneopentyl Glycol 0
Tetrabromophthalic Acid Ester 0
Chlorendic Anhydride 1.73 0
Tricresyl Phosphate 1.16 0
Ammonium Fluoroborate 1.87 0
Hexachlorocyclopentadiene 1.7-2.4 0

.— -.
 Downloaded from http://www.everyspec.com

3-6.6.1.1 Plastics emit sulfur dioxide andlor hydrogen sulfide and produce

o Most plastics in use today will burn. Even those materials

classified as nonfkunmable or self-extinguishing decompose
and evolve potentially hazardous gases if subjected to a sus-
sulfuric acid if moisture is presen~
Natural rubbers are highly combustible. ‘Rte carbon black
in tires or track pa& for example, burns at a high tertrpaa-
tained flame. Those materials classified as slow burning can ture and produces glowing coals that are difficult to extin-
still evolve significant amounts of toxic fumes over a short guish.
period of time if the burning material has a high surface
3-6.6.1.3 Fire-Retardant Additives
area, which creates greater conuict with atmospheric oxy-
gen. Both organic and inorganic materials are used as fire
Some of the more flammable of the combustible plastics retardants. Some of the inorganic fire reudants are non-
are certain epoxies, celhdosic compounds, acrylics, acetals, toxic but can be respiratory irritanrs. Magnesium silicate,
polyacrylene ethers, poiybutylene, polybutadiene, polyester disodiurrt phosphate, sodium borate, and antimony rnoxide
ed polyurethane), polyethylene, polypropylene, axe all considered toxic. Antimony trioxide is also a sus-
(~
and polystyrene. Examples of slow-burning plastics are pected carcinogen.
furans, acetals, cyanatedcyanimides, and caseins. Self- The organic fire retardrmts are normally highly haloge-
extinguishing matials are plaslics such as ~ds, chlori- nated and when heated to a given temperature can generate
nated ethers, polyvinyl chlorides, melamines, ureaformalde- toxic prt%lucts. Those ihe retardants that contain bromine
hydes, phenolics, polyamide% polycarbonate, polyamides, emit hydrogen bromide gas when heated to decomposition
temperature. Those retardants containing chlorine can emit
pcdyphenylerte sulfide, and polysulfane. The very heavily
phosgene and hydrogen chloride. Organic fire raardants
halogenated plastics,e.g.,polyiluorocarbons andcMoroflu-
also produce carbon monoxide when incompletely burned.
orocarboIwarenonfhmmabie.
The organic fire-retardant chemicals are considered toxic,
Plastics are organic and can emit hazardous gas when
but when incorporated into a plastic or elastomeric mti
burned. If any organic material is burned without sufficient
the chemicals are effectively encapsulated so the polymeric
oxygen presenL carbon monoxide is formed. The chlor-
materials are safe to handle.
inated rwins are particularly hazardous when burned

,,
0
because pitosgene can be produced. Materi#s that can p-
duce phosgene when burned are PVC, PVC-vinylidene
chloride, chlorinated polyalkene ethers, and the chlorofhm-
Fii retardants inhibit burning by several mdumisms.
Some retardants aker decomposition and combustion reac-
tions, so any evolved gases either are noncombustible and
act as diluents or possess sufficiently high heat capacities to
rocarbons. Phosgene is formed even in the presence of suf&
wrve as heat sinks. Either effect reduces chemical reaction
cient oxygen for complete combustion of the materials. The
mtes and hence heat release rates in the burning evolved
chloninatod resins will also emit hydrogen cMoride (HCl)
gases. Water, carbon dioxide, and halogenated compounds
gas when burned The fluorocarbons emit hydrogen fluoride
operate via this gas-generating mechanism. Phosphorus-
(W) when burned. Both HC1 and HF are toxic when
and boron-containing compqnds ipcrease ~ amount of
inhaled- TEe cyanatedcyanimides emit hydrogen cyanide
carbonaceous char and thereby reduce the amount of flam-
&CN) upon burning. HCN is a highly toxic and flammable mable gas evolved from a burning material and reduce the
gas. Upon burning the sulfurous resins, such as poIysu.lfone available heat of combustion. Halogenated compound addi-
and polyphenylene sdfide, emit hydrogen sulfide and prw tives also may inhibit free radical chain reactions as the
duce sulfuric acid if sufficient moisture is present. burning plastic decomposes into combustible gases. Anti-
mony trioxide works synergistically with the haIogenated
3-6.6.1.2 EkMtOIllel% retardants.
The elastomeric materials used in military vehicles are
flammable. Flammability is reduced somewhat by the halo- 3-6.6.1.4 Fillers
genation of the polymeric resin. CMoroprene and haloge- Fiilers and extenders are commonly mixed with plastic
nated silicone are examples of elastomers with reduced and elastomeric resins to improve terrain physical and
flammability. Chlotmprene will bum even though haloge- chemical properties of those resins and to reduce the cost of
nated. The halogenated silicones are considered nonflam- the resultant mixture. Most of the fiilers are harmful to
mable, and the unhalogenated silicones are considered inhale and are classed as respiratory irritants. Prolongti
combustible. When silicone burns, the residue contains sil- inhalation of crystalline silica can lead to silicosis, a serious
ic% which can be a potentially harmfid initant when inhaled lung disease. Asbestos is a widely suspected carcinogen
in powder form. and great care must be taken not to inhale any asbestos par-
All of tbe elastomers are organic and when incompletely ticles. Because of its carcinogenicity, asbestos is not nor-
burns will emit cm%on monoxide. The chlorinated elas- mally used.
0 tomem can produce phosgene when burned. The polysulfide Fillers containing carbon are flammable. Examples of
elastomers have a high sulfur content and when burned can combustible organic fillers are graphite and carbon black

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~iL-HDBK-684
Finely divided metal fillers, such as aluminum and iron, are the ratio of carbon monoxide (highly toxic) to carbon diox-
highly flammable and are used in pyrotechnics. These mate- ide (asphyxiant). Also a wide variety of polymer decompo-
rials burn at high temperatures. Airborne graphite and car- sition prop evolve as simple hydrocarbons (e.g.,
bon fillers and fibers can also damage elecrncal equipment methane a~~ propane), partially oxidized species (e.g., ace-
by causing it to short out and malfunction. taldehyde and acrolein), and more complex compounds
Filler and reinforcing fibers help to maintain the physical (e.g., polyr$clear aromatics).
integrity of the unburned material and the burned char. Many o.f~the materials in combat vehicles, either natural
Maintaining the integrity of the outer char reduces the or synthetic, contain nitrogen, sulfur, and halogens, in addi-
exposed surface area of unburned substrate. Some fillers tion to carbon and hydrogen. See Table 3-16. When these
have a high specific heat and thermal conductivity and materials burn, hydrogen cyanide (HCN), nitrogen oxides
absorb or dissipate the available heat<haracteristics that (NO X), sulk dioxide (SO,), ammonia (NH,), amd halo-
prevent the polymeric material from being heated to igni- gen acids (HC1, HBr, and HF) may form. Also isocyanates,
tion temperatures. Hydrated fillers absorb heat energy as nitndes, and other polymer decomposition products may be
they dehydrate. See Table 3-15 for properties of typical present.
filled and fiber-reinforced phistics. Some of the other textile materials mentioned that are not
specifically~identified in Table 3-16 fall within the general
3-6.6.2 Textiles polymer groups. Canvas is generally linen, hemp (natural
Fabric items such as NBC protective garments, canvas plant fiber)? or cotton. Burlap is usually jute (also a natural
sacks, tarpaulins, camouflage nets, and sleeping bags pose a plant fiber) ,or hemp. Both of these would fall under the gen-
most significant fire threat. Upon ignition, these items will eral categoiy of “sisal” in Table 3-16. Manila rope, made of
burn, and may be difficult to extinguish because of deep- manila he~p, is used because it is resistant to stretching.
seated smoldering combustion. Ignition may occur from any Down wo~d probably fall in the same category as silk
of several sources, e.g., hot metal, fiels or other combusti- (fibroin or protein). Fiberglass and rock wool are used as
bles, and munitions. Ignition of canvas due to hot metal insulation and would have relatively little burnable mass;
fraegnents would be a particularly insidious fire that could howeve~, tQere is some resin to hold it together. This small
potentially smolder for a long time prior to ignition. Smol- amount of ~urnable mass does not necessarily mean that the
dering combustion, although it is not an apparent fire, may combustio~ products are nonhazardous. Fiberglass as a fab-
produce toxic gmes. ric or construction material probably contains at least SO%
Equipment such as tarpaulins, camouflage nets, fabric polyester o! epoxy resin, which would be in the category of
camping gear, or sleeping bags stored on the outside of a polymethylmethacrylate (PMMA) for the purposes of iden-
vehicle may pose an unusual fire hazard in the case of igni- tifying elemental composition. (PMMA is also used in
tion of spilled fuel or a Molotov cocktail external to the monobloc form for aircraft canopies and is refereed to as
vehicle. Such equipment would likely ignite and possibly stretched acrylic.)
sustain flaming combustion long after the fuel has burned Studies ‘involving the analysis of atniospheres in real ties
off. This fire hazard on the outside of a combat vehicle have been conducted by the use of portable smoke-sampling
could generate smoke, potentially make the inside of the devices c+ed by firemen in actual fire environments. In
veh@le untenable due to heat, or cause continued burning of these studies samples of the fire atmospheres were analyzed
items on or inside the vehicle. for selected toxic combustion gases. The results of the anal-
Clothing, including chemical protective garments, yses confi~ that combustion products can be produced by
stowed within the vehicle would probably be made of materials in real fires in sufficient concentration to create
nylon, cotton, nomex, Kevlar ~ , fiberglass, wool, rubber, environments that are toxicologically hazardous to the
and/or the chemical protective carbon-impregnated coat- occupants ~ well as to the firemen engaged in fire-fighting
ings. Sleeping bags would probably be made of ‘fiber- or operations. IA brief review of the toxicological effects of
down-filled nylon. Individual tents are made of nylon; troop exposure to,the major fire gases is presented in Table 3-17.
tents are made of canvas. Camouflage nets are made of
nylon with synthetic streamers providing the colored fills. 3-6.6.3 other
Manila rope is often used. Other items located in ,or on combat vehicles that can
There are too many materials in use today to describe the bum or support combustion and that can present a hazard
composition of each and the range of possible combustion include
produc~” that could result. Table 3-16, however, contains 1. Pa&r items, such as maps, documents, and message
some pertinent properties of natural and synthetic materials. pads :,
All materials containing carbon %e likely to evolve carbon 2. Rations
monoxide and/or carbon dioxide during combustion. The 3. T&h and debris
amount of air present at the site of combustion influences 4. Bottled oxygen and acetylene

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0 0 0
TAIJUI 3-16. PER XNENT PROPIWTIES OF FIBERS, PAPER, AND LEATHER (Refs. 117-119)
HEAT OF SPECIFIC A1.ITOIGNITION AUITIIGNiTION THERMAL LATENT
COMBUSTION, HEAT, TEMPERATURE, TEMPERATURE, CONRUCTMTY,
HEAT OF
lvlJ/kg I(Jn(g.”c ‘C (W), IN FLASK ‘C (W), HOT W/InK VAPORIZATION,
PLATE MJn(g
16.5-20.4 0.267-0.312 385 (725) 465 (869) 0,005-0.042
13.2 -19.8 0.310 0,060-0.159
0.284 0!019-0.045
wool I 0.136 20,7-26.6 0.339 540(1004) 0.020-0.036
Pnoer.
. . brown I
0.7-1s3 16.3-17.9 400 (752) 470 (878) 0.045-0.130 2.2
CCIIUIO.W Acetate, I 1.27-1,34 17.8-18.4 1.26-1.76 550 (992) 3.5
c3f4,*06
Polyamide (Nomcx~ 27.0-28.7 515 (954)
Nylon 6/6 1,13-1.15 31.6-31.7 1.67-1.70 2.3
13.6-19.5 I I I I
I1 0.186 I
467 (873>* I 1 1.57 1 1.7-2.2
427;80&
slarts to carbonize
Polyethylene (Spcctra~ 0.97 2.30 488 (91O)* 1.5-2.7
Sisnl 15.9 I I I I
Linen I I 0.030-0.087
WI methodis not described.
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MIL-HDBK-684

TABLE 3-17. TOXICOLOGICAL EFFECTS OF FIRE GASES (Ref. 120)

ESTIMATE OF SHORT-TERM 9
TOXICOL$KNCAL (10-min) LETHAL
TOXICANT SOURCES E~CTS CONCENTIUTK3N, ppm
Hydrogen Cyanide From combustion of wool, A rapidly fataI ~mphyxiant 350*
silk polyacrylonitrile, poison j
(1-ICN)
ny~on, polyurethane, and II
paper
Nitrogen Dioxide (NOZ) Produced in small Strong pulmonary irritant >200
and Other Oxides of quantities from fabrics and capable of causing
Nitrogen in larger quantities from immediate death as well as
cellulose nitrate and delayed injury
celluloid
Ammonia (NH ~) Produced in combustion of Pungent, unbearable odor; >1000
wool, silk, nylon, and irritant to eyes ‘kndnose
melamine; concentrations
generally low in ordinary
building
Hydrogen Chloride From combustion of Respiratory ~,tanc >500, if particulate is
(HC1) polyvinyl chloride (PVC) potential to~cliy of HCI absent
and some fire-retardant- coated on particulate may
treated materials be greater thm~that for an
equivalent amount of
gaseous HC1. ~
Other Halogen Acid Gases From combustion of Respiratory irritants I’IF= 400
(IIF and HBr) fluorinated resins or films HBR >500
and some fro-retardant
materials containing
bromine
Sulfur Dioxide From materials containing A strong irritaq~ >500
(s02) sulfur intolerable well below
lethal concentrations
Isocyanates From urethane polymers; Potent respiratory irritants; =100 (TDI)
pyrolysis products, such as believed to be @e major
toluene-2, 4-diisocyanate irritants in smoke of 7 : “-
(TDI), have been reported isocyanate-based urethanes
in small-scale laboratory
studies; their significance
in actual fues is undefined.
Acrolein From pyrolysis Potent respiratory irritant 30 to 100
of polyolefins and cellulosics 1:

at lower temperatures
(=400”C)
*Someinvestigatorsbelieve that 350 ppm would requireat least 30 rninto cause lethality.

5. Void filler materials, such as reticulated foam Rations ye normally difficult to ignite but would provide
6. Combustible metal components. additional iiel in a strong fire.
Paper items kept within combat vehicles include maps, Trash includes wastepaper, cleaning rags, used filter ele-
message pads, manuals, records, and many other docu- ments, old fuel or hydraulic fluid hose, cigarette butts, and
ments. These can become saturated with fuel, oil, or other many other combustible items that collect in vehicIes.
hydrocarbon fluids if the liquids are sprayed onto the paper Debris incl~des leaves, twigs, small branches, and other
items. The paper can be ignited by a fuel or gun propellant combustible matter that fall into or are blown or tracked into
fire, by electrical shorts, or by a hot metal fragment or a vehicles an~ collect in the bdge, comers, or other out-of-
shaped-charge slug lodged wi~n or on the paper item. The
paper can burn by either flaming or glowing.
the-way pla~es in vehicles. Many of these items become sat-
urated with ~rnotorfiel or oil and can be ignited by electrical
9
3-48
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MIL-HD8K-684
discharges, vehicuhtr hot spots, hot metal pieces from baUis- ity-Phase 1, Interim Report BFLRF No. 236, Belvoir
tic impacts, or the combustion of more easily ignited items. Fuels and Lubricants Research Facility, Southwest
O
,’
Once ignited, these items can smolder until fire suppressants
have become diluted and fires can mignke.
Research Institute, San Antonio, TX, July 1987.
9. hf. D. Kanakia and B. R Wrighq Fkunrnabili~ Chur-
Bottled oxygen can be found in combat vehicles that are acreristics of Di$rikte FueLr, Interim Report BFLRF
used for medical evacuation or for maintenance or recovery No. 234, Belvoir Fuels and Lubricants Research FaciI-
of immobile vehicles. In the latter case, bottled acetylene ity, Southwest Research IMitute, San Antonio, TX
will probably be present a.ko. ~ an oxygen bottle is Nptured June 1987.
os OXYgencan otherwise ==F, me probability of ignition 10. .?ZcxonPraducts Summury, Exxon Corporation, Hons-
and of achieving fkrning combustion of combustible items ton, ‘IX, August 1990.
is grwuly increased. Freed acetyIene would present a poten-
11. A. D. Rasberry, CPT J. H. Weatherwax, W. Butler, Jr.,
tial explosion hazard. E. A. Frame, P. L Lacey, and S. R. Westbroo~ Pe~or-
If placed within a combat vehicle, void filler material,
mance of Fuels, Lubricants, and Associated Prvducts
such as reticulated foam, would provide another combusti-
Used During Operation Deserr ShieWStonn, Report
ble item. Normally this polyester or polyether foam would No. 2527, US Army Belvoir Research, Development
be somewhat difficult to igaite, but given a strong fire, it and Engineering Center, Fort Belvoir, VA August
would burn.
1992.
Combustible metals include lithium, magnesium, and
12. Fuef Users Guide-1992, Fuels and Lubrhms Divi-
titanium Lithium is used in the newer, heavydu~ battesies.
sion, US Asmy Bclvoir Research, Developmen~ and
Given a ballistic impact that ruptures the battery case, the
Eagitteering Center, Fort Belvoir, VA, December
lithium plates could be exposed to air. Lithium combines
1992.
with either oxygen or nitrogen and produces a high quantity
of heat while combusting. This characteristic makes extin- 13. B. R Wrighq Comparatt”ve Fiizmmabifio Taring of
guishing a lithium fire difficult. Magnesium and high mag- Jet A-1, JP-5, and DF-2, Letmr Report No. BFLRF-
nesium-aluminum alloys burn in air once ignited. 90-003 (Revised), Belvoir Fuels and Lubricants
Research Facility, Southwest Research Institute, San
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0 1. M. G. Zabetakis, Flammability Characrenstics of

Condnxsrible Gases and Vapors, BuUetin No. 627,
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15. J. N. Bowden, S. R WestbroolG and M. E. LePen A
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16. C. L. Dickson and P. W. Woodward, Aviarion Ttiine
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0 8.
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3-49
 ,,
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3-50
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Code No. H-537, 25 March 1986. March 1987.
55. White Paper for Proposed Single Hydraulic Fluid, 69. MU-L2104E, Lubricating 0i4 Internal Combwion
Belvoir Research, Development, and Engineering Engine, CombatiTUticai Senice, 1 August 1988.
Center, Fort Belvoir, VA, 14 December 1992. 70. E. A. Frame, A. F. Montemayor, and E. C Owens,
56. ML-H-531 19(ME), Hydraulic Fluid Nonj?ammable, LAbomtoq Evaluation of Commercial Engine Oil
CMoromjluomethylene-Bare, 1 March 1991. Quality, InterimReport BFLRF No. 228, Belvoir
57. MIL-IW2072C(AS), Hydraulic Fluid, Catapu& Fuels and Lubricants Research Facility, Southwest
NATO Code NO. H-579, 5 March 1984. Research kstitut~ San AfNOtiO, TX, April 1989.
58. MIL-H- 19457D(SH), Hydraulic Fluid Fire-Resistant, 71. MIL-L-2105D, Lubricating Oil, Gear Multipurpose
Nonneumonc, 12 April 1989. (Mem.c), 2 August 1987.

59. MR-B-46176A. Brake Flti Silicone, Automotive,

72. MIL-L-7808J, Lubricating Oi~ Aircraji Turbine

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MIL-HDBK-684 ‘
Engine, Synthetic-Base, NATO Code No. 0-148, 11 report of tests of “Fire Suppression Agents Tested
May 1982. With, Shaped-Charge Jet Perforating 105-mm Car-
73. MIL-L-90001-I(SH), Lubricating Oil, Shipboard inter- tridges”, SWRI Project No. 06-7896, Southwest 9
nal Combustion Engine, High-Output Diesel, 16 Sep- Rese~ch Institute, San Antonio, TX, 19 March 1984.
tember 1987. 92. P. H. Zabel, Shaped-Charge Test Pe@ormance of Fuel
74. IWL-L-21260D, Lubricating Oil, Internal Combus- Tmk~ for the Advanced Survivability Test Bed Vehi-
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Rese$rch Institute, SamAntonio, TX, February 1987.
75. MIL-L-23699C, Lubricating Oil, Aircrajl Turbine
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1955:
76. MIL-L-46152D, Lubricating Oil, Internal Combus-
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1988. on Solid Propellants, Report No. AFRPL-TR-76-90,
US ~ Force Propulsion Laboratory, Edwards Air
77. MILL-46 167B, Lubricating Oil, Internal Combustion
Force Base, CA, November 1977.
Engine, Arctic, 29 July 1988.
95. Table of “US Gun and Howitzer Propellant Composi-
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tion itnd Some Characteristics”, in use in the Internal
Pressure, 10 April 1967.
Balli$ics Group at US Army Ballistics Research Lab-
79. I? H. Zabel, M. J. Lewis, Jr., and B. Bo~osky, Surviv- orato~, Aberdeen Proving Ground, MD, to P. H.
ability Enhancement of Advanced Survivability Test Zabel, Southwest Research Institute, San Antonio,
Bed Vehicles Given a Shaped-Charge Hit Through the TX, horn A. E. Finnerty, US Army Ballistic Research
Engine Companrnent Fuel Trek, Report No. ASTB- Laboratory, Aberdeen Proving Ground, MD, May
87-2, US Army Tank-Automotive Command, Warren, 1992!
MI, July 1987. 96. Corr$mnication from S. Bernstein, US Army Arma-
80. MIL-A-11755D, Antifreeze, Arctic-Type, 14 July ment~Research, Development, and Engineering Cen-
1977. ter, Rjcatinny Arsenal, NJ, to P. H. Zabel, Southwest
81. MIL-A-46153B, Antfreeze, Ethylene Glycol, Inhib- Resehrch Institute, San Antonio, TX, 29 May 1992.
ited, Heavy-Duty, Single Package, 31 July 1979. 97. P. H.iZabel, P. A. Cox, L. R. Garz~ ~d M. J. Lewis,
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Accident Investigators, Technical Report No. AFAPL- SWRI Report 06-1881-001, Southwest Research Insti-
TR-73-74, US Air Force Aero Propulsion Laboratory, tute, San Antonio, TX, December 1987.
Wright-Patterson Air Force Base, OH, August 1973. 98. Propellant Description Sheets for Lots of JA-2 and
83. Conversation Wtween P.. H. Zabel, Southwest DIGL-RP Propellant to P. H. Zabel, Southwest
Research Institute, San Antonio, M, and A. E. Rese$rch Institute, San Antonio, TX, by A. E.
Finnerty, US Army Ballistic Research Laboratory,’ Finnerty, US Army Ballistic ‘Research Laboratory,
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84. M. Bennett, “Advanced Concepts for Aircraft Fue 99. Tele~hone conversation between R. Lantz, US Army
Protection Systems”, Proceedings and Report, Fire Armament Engineering Directorate, Propulsion Engi-
Safety/Sumivability Symposium, 1990, Vol. Z, Defense neering Section, Picatinny Arsenal, Dover, NJ, and P.
Fire Protection Association, Alexandria, VA, Novem- H. Zabel, Southwest Research Institute, San Antonio,
ber 1990. TX, Febmary 1993.
85. Cryotech E3@M Liquid -Deicer, Cryotech Deicing 100. L. M: Vargas, R. M. Rindner, and W. M. Stirrate, Fire
Technology, Fort Madison, IA,.April 1992. Suppression System Safety Evaluation, ARLCD-CR-
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101. A. E: Finnerty, An Extinguisher to Quench Propellant
87. Verbal report by B. R. Wright to I? H. Zabel concer-
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88. MI.L-F-12070C, Fog Oil, 16 May 1984. ‘“
102. D. N. Ball; “Propellant Charge Protection”, Proceed-
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II

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MIL-HDBK-684
of Fire, SWJU Report 06-3193-001, Southwest 119. Allied Fibers Dat@ Sheer on Cbmparrzrive Taile
::
O
l?esearch IiIstitute, San AntoNo, TX, December 1990.
104. B. M. Dobratz, LLNL Explosives Mzndboo4 Proper-
Fiber Properties, Spectra, Allied Signal Inc., Peters-
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~
Fm Protection Association, Quincy, MA, 1986. March 1985.

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Technical Report No. 4483, FMC Corporation, San Jose,
CA 28 October 1986.

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S. R. West~rook and L. L. Stavinoha, Development of the
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sile B“aseline Cook-ofl Tests, NWC Technical Paper No.
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Fluids by Hot Su@aces Under Dynamic Conditions, Louis, MO, Undated.

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o ~WIWK 4
FIRE PREVENTION
l%e components and systems of combat vehicies that render the vehicles and crew vulnerable tojire are described and tech-
niques are given that enhance vehicular survivability by preventing the ignition ofjires. The components and systemr rhatcon-
rnbrate most to vehicular and crew vulnerability are the on-boand munitions, rhe engine, thejitel systenq the hydraulic system
and the electrizd system. Material selection criteria and system integmtwn am also discussed

4-1 INTRODUCTION
When presented with the problem of eliminating an tty M2 and cavalry M3; the light-armored vehicle (LAV)
unwanted fire, most designers of combat vehicles would 2S; and the armored recortnaissanccdairbome assault vehicIe
incorporate a k extinguisher into the design of the vehicle. (AIVAAV) M551
However, h extinguisher systems should not be the only 2. Personnel carriers, such as the armored personnel
or even the jxknary protection. At the veq learn &e can tier (APC) Ml 13 and its variants-the armored com-
force the crew to evacuate and will destroy needed items. A mand post M577, the cargo carrier M548, and others that
better protection technique is to incorporate fire prevention are more properly combat vehicles, such as the improved
measures into the design of the vehicle and its components tube-laurtchq optically tracked, wire-guided (TOW) mis-
in order to minimize the possibility of a fire being ignited or, sile antitank vehicle M901, or combat support vehicles like
once started, of propagating. Fwe prevention can be accom- the armored self-propelled 107-mm mortar carrier M106.
plished by (1) keeping fuel from an oxidizer-rich region, (2) Them is also the amphibious assault vehicle (AAV) 7.
reducing the oxidizer available to fuel that is plenti.fid, (3) 3. .Combat support vehicles, such as self-propelled
keeping ignition sources from flammable fuel vapor-air
,, mixtures, (4) providing a beat sink to transfer heat energy
howitzers (SPH) M109 and Ml 10, combat engineer vehicle
(CEV) M728, and division air defense (DIVAD) vehicle
O away from potential fuels and thereby keeping their temper-
atures below their kindling points, (5) introducing nonflam-
M247 (Sgt York)*
4. Service support vehicles, such as the field artillery
mable gases to dilute the existing fiel artd oxidizer mixture
ammunition supply vehicle (FAASV) M992, the armored
below flammable levels, (6) releasing gases with a higher
vehicle launch bridge (AVLB), and the tracked recovery
probability of uniting with free radicals, (7) providing a low
vehicle (TRV) M88.
thentt.al conductivity layer, which reduces the rate of heat
‘I%ereare two databases that can provide information on
transfes to combustible materials, andlor (8) providing a
design needs. The US Army Safety Center (USASC) col-
material that absorbs heat innocuously-i. e., evaporates or
lects and collates reports of fires involving Army eqip-
becomes hotter, as does ahuninum oxide-and thus reduces
the quantity of heat available to raise the temperature of any merm The bulk of these reports concerns operations during
fuels present. peacetime, i.e., noncombat fire incidents. These reports are
The fire-critical systems or components of combat vehi- refereed to as the USASC &tabase. The second database is
cles are covered in the paragraphs that follow and include data cokcted during the Battle Damage Assessment and
the engine,
— the fuel system, the hydraulic system, the elec- Repair Program (BDARP) conducted in Southeast Asia
trical system, and munitions. A paragraph on material selec- (SEA) during the late 1960s and early 1970s. This database
tion and another on system integration complete this is maintained at the Survivability/Vulnerability Information
chapter. and Assessment Centes (SURVIAC) at Wright-Patterson Air
&tnored combat vehicles provide mobility, protection, Force Base (W-P AFB), OH. ‘his database is referred to as
and firepower. All three attributes are essentizil. These vehi- the SEA BDARP database. These databases are &scribed in
cles must operwe in the field for long periods while moving subpars. 4-1.1 and 4-1.2. Recommendations for design con-
frequently. In training, soldiers use combat vehicles in much siderations are in subparagraphs in this chapter on the fuel
the same manner they would in comb~ therefore, a review system, ancillary power, electrical systems, ammunition,
of reports of fires that have occurred during peacetime oper- materials selection, and systems integration or in Chapter 7,
ations cart provide insight into vehicle weaknesses that “Extinguishing Agents and Systems”.
would be exacerbated in combat operations.
There are four categories of combat vehicles: WI%eairdefense vehicle (Sgt York)was never fielded by the US
1. Fighting vehicles, such as main battle tanks (NIBT) Army. It isincludedhere becausethere are some ti on it and it
Ml, M60, and M48; Bradley fighting vehicles (WV) infan- representsa type of vtitcle that tnay be fieldedin the future.

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MIL-HDBK-684 ;
4-1.1 TRAINING-INDiJCED FDWS which is no longer in wide usage. Only five reports were
Records of fire incidents are collected by the USASC, obtained for review, and the majority of the problems
Fort Rucker, AL. Extracts of these records for the period fis- resulted from the location of the munition storage racks.
cal year (FY) 1983 through FY87 from US Army organiza- The Ml 13 series vehicles had 40 reported fires during the
tions and from the US Navy Safety Center (USNSC) for the time penod~ Many of these cases involved electrical arcs
period October 1985 through September 1986 were that ignited fuel in the engine compartment. Sometimes soft
reviewed for this handbook. Many of the USNSC reports items, such’~ clothing and camouflage netting, burned and
were of the same incidents reported by the Army, but they the fires spread to on-board ammunition. Fire departments
were from the fire departments because all service fire had to extinguish many of these fires. Some of the vehicles
departments report incidents to the LJSIWC. The US Army burned uncontrolled and were completely destroyed.
tactical and training organizations, even those in Germany, The data set on the M88 TRV had 38 reports. Almost all
submit fire reports to the USASC. Often, details missing in reported tires, 35 of 38, occurred in the engine compartment
a report from one source are given in the report from and usually ~hvolved the ignition of fuel or oil on a heated
another source. The USASC issued two reports summrajz- surface. Some wiring harness electrical fires were reported.
ing fires prior to 1984 (Refs. 1 and 2), but these summaries Twenty-three of the fires were extinguished with on-board
lacked the details required to analyze the design features equipment- 14 of them with fixed fire extinguisher systems
that either resulted in fires or helped to extinguish fires. (FFESs), aid nine with portable extinguishers-and 13 by
A tabular summary of vehicle fire survivability statistics fire departments.
is given in Table 4-1. Table 4-1 is divided into four sections: The M60 AVLB, M728 CEV, and M247 (Sgt. York)
DIVAD had.a total of only eight reported fires. All occurred
(A) ignition source, (B) fire location, (C) combustible mate-
in the engine compartment and all but one involved the igni-
rials, and (D) extinguisher used for final suppression of fire.
There were 39 reports involving Ml tank fires from FY83 tion of oil or fuel on a heated surface. The remaining fire
through FY87. The vast majority-of reported fires (33 of 39) was caused by an electrical short. Half of the fires had to be
extinguished by fire departments.
were engine related and located in the engine compmtment.
The M109 and Ml 10 self-propelled howitzers had six
Of the remainder four were in the personnel compartment
reported fires. The fires varied and half were in the crew
and two were external fires. The primary combustibles
compartment. Two electrical fires were reported, one in an
included fuel, oil, and hydraulic fluids, which were usually
engine compartment and one in a turret. Both were extin-
ignited by contact with heated surfaces. Less frequent cases
guished with portable equipment. Another involved gloves
involved the electrical short circuit of major wiring har-
that ignited when placed on the personnel heater. A fire
nesses (6 of 39) or the explosion of heated aerosol cans (2 of
started when a mechanic cut a filled hydraulic line with a
39). Fire department equipment using copious quantities of
torch. Two others were caused by munitions effects while
water was required to extinguish the blaze in at least eight
firing the main gun.
of the reported cases, whereas on-board equipment extin-
An overall examination of these fire statistics reveals that
guished 29 fires. Other evaluations are given in later para-
the engine compartment was the principal location for these
graphs.
noncombat fires (163 of 233). These tires typically involved
A very limited data set exists on the M2 and M3. Only
either electrical or heated-surface ignition of fuel, oil, or
nine fires were reported during the time period. Six of the
hydraulic fluid or the burning of electrical components (172
reported fires were located in the personnel compartment,
of 233). The next largest contributor was personnel heaters
and half of these were due to the troop compartment heating
in the troop compartment, which comprised 25 of the
unit.
reported fires. These fires were caused by fuel from
The kugest data set, containing 88 reported fires from
unpurged he,aters, explosion of aerosol cans left on top of an
FY83 through FY87, exists on the M60 tank. Sixty-eight of
operating heater, or other combustible items placed on or
the incidents occurred in the engine comp@rnent of the
near these heaters. Munitions effects caused few of the fires,
tank and involved burning of electrical wiring harnesses,
although an-knunition was involved as a combustible in 12
electrical ignition of leaking fuel, or ignition of fuel, oil, or
of the noncombat fires.
hydraulic fluid on heated surfaces. Nineteen of the 20
remaining incidents occurred in the personnel compartment
4-L2 BATTLE-INDUCED FIRES
and consisted largely of fires related to the personnel heat-
ing units or the ignition of soft items-camouflage nets, 4-1.2.1 Ilattle Damage Assessment and Repair
sleeping bags, clothing and personal items, sandbags, tar- I?rogram Database
paulins, upholstery-and stowed munitions. The majority of In the fid-1960s, the US Air Force and the US Army
reported fires were extinguishable by on-board means; 28 each had a BDARP in which teams were sent to SEA to
had to be extinguished by fire departments. obtain descriptions of the battle damage sustained by equip-
The smallest data set was obtained for the M48 tank, ment, both aircraft and ground vehicles, and of the efforts

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MIL-HDBK-684

TABLE 4-1. SUMMAR Y OF VEHICLE FIRE SURVIV’IUT’Y STATISTICS (Ref. 3)

o
‘.
VEHICLE NUMBER OF
INCIDENTS HEATED
(A) IGNITION SOURCE
ELECTRICAL MUNITIONS PERSONNEL OTHER
SURFACE HEATER
Ml Tank 39 28 6 0 2 3
NE?and M3 9 2 4 0 3 0
BFVS
M60 Tank 88 30 35 1 10 12
NM8 Tank 5 1 3 0 0 1
M113APC 40 6 16 4 7 7
M88 TRv 38 21 10 0 2 5
AVLB, CEV, 8 7 1 0 0 0
and DIVAD
M109 and 6 0 2 2 1 1
M11OSPH
233 95 77 7 25 29

VEHICLE NUMBER OF (B) FIRE LOCATION

INCIDENTS ENGINE PERSONNEL EXTERNAL
COMPARTMENT COMPARTMENT ‘m HuLL
Ml Tank 39 33 4 2
M2 and N13 9 3 6 0

,,
BFVS

0 M60 Tank
M48 Tank
M113 APC
88
5
40
“ 68
2
13
19
3
21
1
0
6
M88 TRv 38 35 2 1
AVLB, CEV, 8 8 0 0
and DIVAD
MI09 and 6 1 3 2.
MI IOSPH
233 163 58 12

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4-3
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TABLE 4-L (cent’d)

VEHICLE NUMBER OF (C) COMBUSTIBLE MAI’ERIALS
INCIDENTS WIRING FUEL OIL HYDRAULIC MUNITIONS PERSONAL EXIERNAL NOT
HARNESSES, FLUIDS GEAR, SOFT REPORTED
etc. ITEMS, AND
1
CLOrHING
Ml Tank 39 2 24. 0 ‘6 1 2’ 1 ‘3
M2 and M3 9 2 7 0 0 0 0 0 0
BFVS
M60 Tank 88 14 36 24 1 2 3 0 8
M48 Tank 5 1 0“0 o 3 0 0 1
M113APC 40 ‘6 16 0 0 5 10 3 0
M88 TRV 38 7 12 13 0 0 1 2 3
AVLB, CEV, 8 1 3 4 0 0 0 0 0
and DIVAD
M 109 and 6 2 0 0 1 1 2 0 0
MI IOSPH
233 35 98 - 41 8 12 18 6 15

E
(D) EXTINGUISHER USED FOR FINAL SUPPRESSION OF lWIE
VEHICLE NUMBER OF SELF- FIXED FIRE PORTABLE OTHER FIRE VEHICLE NOT
INCIDENTS EXTINGUISHING EXTINGUISHER DEPARTMENT DESTROYED REPORTED
AUTOMATIC IMANUAL “
M-l Tank 39 1 8 5 16 “-0 ““’-8 o ‘– 1 ‘-
M2 and M3 9 0 0 1 5 0 1 0 2
BFVS
M60 Tank 88 3 * 13 37 0 28 0 6
M48 Tank 5 0 * 0 1 0 I 0 3
MI13APC 40 7 * 1 7 1 16 4 4
M88 TRV 38 0 * 14 9 0 13 0 2
AVLB, CEV, 8 0 * 2 1 1 4 0 0
and DIVAD
M 109 and 6 1 * 0 4 1 0 0 0
M11OSPH
233 12 8 36 80 3 71 4 Ill
124 total using onboard fire-extinguishing equipment

*no automatic fixed fire extinguisher system

9
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necessary to repair that damage. I%e records involving These ACAVS bad the same fire suppression system as

o combat vehicles hit by shapeddarge warheads were exam-

ined to obtain a measure of the damage these vehicles sus-
tained. The vehicIes for which data exist include the M48A3
the M113A1. A 4.8-mm (0.188-in.) thick aluminum wall
separated tie crew comparmtent from the engine compart-
ment. The fixed fire extinguishing system for the engine
MBT, the M551 AR/k?.., and the armored cavalry assault compartment had one 2.3-kg (5-lb) COZ bottle and could be
vehicle (ACAV), which was a fie~d-nmdi.fiedvariant of the activated manually by use of a handle ktcated beside the
Ml13Al MC.* A.Uof these are diesel powered. Either the driver or by use of another handle within the troop compam-
BDARP did not start until after the gasoline-fueled vehicles ment. No fire detection system was provided. One 2.3-kg
were replaca or the BDARP effort did not include orgarti- (5-lb) portable COZ fire extinguisher was provided for the
zations with gasoline-fueled vehicles. The hostile weapons troop COmpiWGIIenL It was located on the inside surface of
used against ritese vehicles included the rocket-propelled the right rear vehicle wall opposite the aluminum or steel
grenades (RPG) RPG-2 and RPG-7 and the 57-mm and 75- i%el cell, which was located against the left rear vehicle
mm recoilkss rifles (RR). No huge caliber kinetic energy wall.
~} projectile data are included in the database. The data Many land mines were encountered in SEA These mines
reviewed are summari zed in Ref. 4. Insights presented in so overwhelmed the armored vehicles used-the ACAV,
this handbook are based upon the BDARP database, upon other MI 13-based vehicles, the MBT M48M, and the AIV
several test programs, and upon reports and accounts of AAV M551-that these vehicles were modifkd to improve
events in conflicts. their cou,ntermine resistance. Fret, sandbags or other items
The data described in Ref. 4 include all incidents involv- were placed on the lower deck. Later, some of the Ml 13-
ing high-explosive antitank (HEAT) impacts on ground based vehicles had an additional layer of titanium armor
combat vehicles in the BDARP database. Incidents in which bolted on the forward half of their bellies. Crewmen often
fire artd/or explosion resulted are further described in Table rode on top rather than within the vehicle. Finally, in some
4-2, which is divided into three sections: (A) incidents M 113-based vehicles extensions were added to the driving
resulting in fire or explosion, (B) highly combustible items controls to allow the driver to sit on top of the vehicle.
hit by jet without a tire resulting, and (C) fire extinguisher Combat vehicles in SEA were often attacked with
system or eminguishant hit by jeL All of these incidents are shaped-charge weapons while the crewmen were exposed
referenced back to a Document Acquisition Number on top. This crew exposure skewed the combat injury data
0 (DAN), wtich is the data element identifier&d
WAC, the repository for these =ords. Although not cov-
at s~. toward more wounds from bullets or ffagments than
wounds from behind armor effects, such as from the
ered in this handbook, there are numerous reports of mine shaped-charge jet, from span, or from blas~ which are
damage in the BDARP database.
expected for combat vehicle crewmen.
The three main combustibles for battle-induced fires are
4-1.2.2 Vehicles, Situations, Threa@ and Comb-
the mobility fuel, the munitions (particularly the solid pro-
ustibles
pellant), and the hydraulic fluid. Other combustibles bura,
The data available (Ref. 6) for the M 113 family of vehi- but not as rapidly, and do not liberate as much heat energy.
cles (FoV) consist of that for43ACAVS,oneAPCM113A1, A hit with either a shaped-charge jet or a high-velocity
one 107-mm mortar canier M 106, one 8 l-mm mortar car- kinetic energy penetrator both disperses the fuel or the gun
rier M125, and one cargo carrier M548. These vehichx were propellant and ignites it. Hydraulic fluid is usually at a high
diesel-powered and had a manually activated, fixed C02 fire pressure and spmys when a hydraulic line or a hydraulic
extinguisher system in the engine compartment and only a fluid container is punctured. Further, the jet or penarator
portable COZ extinguisher in the crew compartment. The
creates many ignition sources.
ACAVS,Fig. 4-1, were used as fighting vehicles by armored
cavairy, armored infantry, and combat engineers (Refs. 7
4-1.2.3 Hits: Number attd Locations
and 8). llterefo~ they were exposed to hostile direct-fire
antitank weapons; all 47 data points included were for dam- Vehicles are often hit more than once in a single engage
age due to direct-fire antitank weapons. lle cupola of the mem. Gunners usually continue to fire on a target until they
ACAV W= &n&m to that of the APC Ml 13A3, Fig. 4-2. see visible evidence rhat they have killed the targe~ particu-
larly when that target has the capabd.ity to attack the gunner.
Whe ACAVSwere APC M113A1s modified in field depots in The following quotations, based upon World War If experi-
S&l. I&cords of the modificationsam not available m either the ence, are taken from War Department Pamphlet 20-17, Les-
prime conuactor, FMC corporation, or the W Army Tank-Auto- sons kamed and Erpedienrs Used in Combar (Ref. 9)
motive Command (TACO.M).FMC Corporation probably fur- “466. Disabled T&. crews should Sti3y with
nished some of ritetrack commanders’(T’C)cupolas(Ref. 5). The
0 BDARPrecordsdo not differentiatebetweenACAVand unaltered
AX M113A1.The aothor was able to differentiateby data given
in each DAN.
immobilized tanks, manning their guns as long as pos-
sible. However, if the situation changes, the crew must
be notified and they must be resupplied with ammuni-

4-5
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TMWE 4-2. FIRE AND NONFIRE INCIDENTS (Ref. 4)

,.
(A) INCIDENTS RESULTING IN FIRE OR EXPLOSION
,’ FIRE SUPPRESSION SYSTEM CREW EVACUATION
DAN VEHICLE INITIAL FIRE FFEs PORTABLE OTHER REASON TIME NUMBER REMARKS
COMBUSTIBLES LOCATION USED- EXTINGUISHER USED- AVAILABLE EVACUATED
IYWECTIVE USED- EFFECTIVE
EFFECTIVE
157 M48A3 Main gun cc N N No time “N 2 Blown-outby
propellant explosion
169 M48A3 Oil in filter EC N N SE Fire not o
detected
1839 M48A3 Unknown cc N N Y 3 Propellant
explosion 1O-15
min after fire
.
153 M48A3 CS grenade Turret N N Y 3 Crew killed or
wounded by small
arms fire
310 M551 Propellant Turret N N No time Y 4 Flash fire of one
=
round
y
463 M551 Wire insulation Turret Y-N N Y 3 Sustained fire of z
-P wiring insulation in u
& turret; vehicle m
F
abandoned for fear A
of explosion of on- -
*
board ammunition
632- -M-551= Wire insulation -EC N N--- , . Burned Eire-not.- -.
.— 0 In battery box
out detected
670 M551 Wire insulation cc (Prob. No) Y-Y Y 2
1532 M551 Fuel EC y.? Y-Y Y 4
1550 M551 Propellant cc N N No time N o 4 killed by
propellant
explosion
228 M113A1 Fuel EC, CC N’ Y-N Under fire Y 4
by enemy
381 M113AI Fuel cc N Y-N Y 5
Notes: CC= crew compartment CS = a tear gas SE= self-extinguished
EC= engine compartment Y = yes RPG = rocket-propelledgrenade
FFES= fixedfireextinguishersystem N=no

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o 0 0 .
TABLE 4-2. (cent’cl)
(A) lNCIDii?~TS RE.kJL~JNG lN FIRE OR EXPLOS1ON
FIRE?SUPPRESSION SYSTEM CREW EVACUATION
DAN Vi3H1CLI? INITIAL FIRE FFEs PORTABLE” OTHER REASON TIME NUMBER REMARKS
COMBUSTIBLES LOCATION USED- 13XTINGU1SHER USED- AVAILABLE EVACUATED
rwmcmm USEl)- fXWEc’rIvr3
EFFECTIVE
..
383 Ml13Al — Fuel ‘- cc N N Y 4
385 MI13A1 Fuel cc N Y 4
432 M113AI Grease C)rivcr N Wc)ol Y 4
compartment blanket-Y
607 M113AI Diesel-soaked cc — Y-Y Y 0
waste
671 h4113Al Wire insulation Driver — Y-Y Y 0
compmlmenl
672 Ml13Al Fuel cc N N No lime Y 2
728 M113AI Small arms cc Y-Y Y 0
ammunition
756 MI13AI Fuel cc N N SE? Y 3
~ 1666 MI13AI Paper cc N Writer-Y Y 0
1668 MI13AI Clothing cc N Water-Y Y 0
1682 M113AI Cans of oil cc N SE Y 3
117 M106 Wire insulation IMery box — N Burned out Fire not
detected penetrated through
an runmunition
SLOr~gC box buLdid
not cnusc an explo-
sion or fire
30I M125 Two whim cc — Y-N 1 OLhcrmnnwniLion
phosphorus did not explode
warheads
1709 M548 Fuel, ammunition Cargo hold — Y-N Dirt-Y 107-mm rockcl hiL
vchiclc in cargo
hold
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M!L-HDBK-684

TABLE 4-2. (cent’d)

(B) HIGHLY COMBUSTIBLE ITEMS HIT BY JET
WITHOUT A FIRE RESULTING
DAN VEHICLE ITEM HIT BY JET
30 M48A3 Gun recoil cylinder; no f~e; hit probably
in nitrogen portion of reservok
36 M48A3 Jet deflected into a 90-mm roun~ round
f~ed from gun soon afterward
213 M48A3 Fuel tank hit in ullage
312 M 13A1 Fuel lines and hydraulic line in bilge
while vehicle was moving
’388 M: 13A1 Fuel and hydraulic lines cut in bilge while
vehicle was parked
435 M: 13A] Fuel cell in ullage
1696 h 551 Smoke grenade launcher on side of tumet;
Courtesyof FMC Corporation.
minor damage to turret skin after exiting
grenade launcher Figure 4-2. M113A3 Showing the Cupola for
tie .50 ~ber Mache Gun
(C) FIRE EXITNGIJISI-IER SYSTEM OR
EXTINGUISIL%NT HIT BY JET tion. When contact is impossible, chances of retrieving
DAN VEHICLE ITEM HIT BY JET the tank are gone; the crews should destroy their tanks
and infiltrate back to our lines. [European Theater of
336 Ml 13A1 Fire extinguisher bottle; jet did not pass
beyond fire extinguisher bottle Operations] ,(ETO)”
This excerpt shows that the U.S., as well as the Rus-
360 Ml 13A1 Water-filled radiator in engine
compartment; jet did not exit radiator sians*, cont@ued to man immobilized tanks as long as they
were effective in engaging the enemy.
333 M551 Mamnite can, then water can; did not exit
“409. Gunnery. In training tartk crews, too much
water can
practice in acquiring speed in gun manipulation cannot
be given. We make it [standard operating procedure]
SOP to fire into all tall buildings, as they invariably
Whkle Commanders l+atch wti contain snipers and machine gunners. We continue to
SO-Caliber Machii Gun
\ fire at an enemy tank until it catches tie, to prevent its
Trcq Cymnsnt Hatch repair or use as a pillbox. (ETO)”
\
This excerpt indicates that we recognized that immobi-
lized tanks were still dangerous and should be tired on until
we know they are no longer dangerous. Therefore, we can
assyme that a disabled tank can be hit several times. Thus to
be truly survivable, it must not catch fire on subsequent hits,
and it should be able to move to cover or to a safe place.
Multiple hits on vehicles were seen in SEA (Ref. 4).
Installing”a manually activated flame and smoke emitter,
a device usqd by naval ships in the past, on a combat vehicle
would provide the crew a means to give the appearance of a
vehicle having suffered catastrophic damage and might pre-
clude the vehicle from receiving additiomll hits.
J
DrivetsHatch
z’ M60MachineGuns
Lhtem[ FuelWI
There hd been much discussion on the most probable
impact location of an antitank projectile on a combat vehi-
I?igt.we4-1. bored Cavalry Assault Vehkk cle. Most antitank gunners aim at the center of the presented
(ACAV) (lkf. 7)
*A single iqunobilized Russian Klementi Voroshilov (KV)-2
heavytank held up the advanceof strongelementsof the 6th Pan-
zer Division;on a road through a forest for 48 h on 23-24 June
1941(Ref. 10).

4-8
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MIL-HDBK-664
area. Impact locations of RPGs on the APC Ml 13 series, the hits are best described as scatteti and these hits were at a

o MBT M48A3, and the ARIAAV M551 were obtained fkorn

the BDARP data. The= hits were made in daylight or at
nighL with the gurmem either attacking or defending, while
great variety of obliquities. Hits all over the target are
readily understandable because the antitank gunner is not
often given the oppommity for a pure side-on, head-on, or
the vehicles were moving or stationary, and with no appar- rear-on shot. Twenty-five hits were during night attacks.
ent impact pattern for any set of conditions (Ref. 4). The 57 One RPG even detonated on an attacker, but the jet passed
hits scored on the 46 Ml13 series APCs are plotted on Fig. through him and hit the vehicle. Several shots were fired in
4-3. Most of these vehicles were ACAVS. The people firing heavily vegetated areas in which the lower portions of the
at these vehiclti were not aiming at defenseless targets; they vehicles were not visible to the firers. Ten shots were fired
were engaging fighting vehicles. Note that there are 17 hits from ambush at vehicles in convoys or with reaction forces.
on the front of the vehicle, 18 hits on the right side, 16 hits ‘Ihe 23 hits on the M48A3 MBT nre shown on Fig. 4-4
on the left sia and 6 hits on the rear. In all four profiles the together with the 16 hits on the M551 AR/AAV. The pat-

,,
0,,
(6) Left Side: 16 Hits

●
& m
A
●

I
@ RPG2 ~ 75-mm RR
,
I 8 RPG7 - RP&

,, A 57inm RR
‘o
Hgum 4-3. NlU3Al APC Hit l%tte~ !kNlth~ A (Ref. 4]

4-9
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MIL-HDBK-684

.,

x-’

(A) Front: 10 Hits, M46A3 (B) Left Side: 8 Hits, M46A3

5 t+k, M551 3 f-m, h1551

1 t
(c)Rear: O l-litq M46A3 (D) Ri@d Side: 5 Hits, M46A3
1!
2 Hits, M551 i 6 Hitsj M551

.,-.

VVeapons - Targets

Q RPG2 4 RPG-2
M4$A3 M551
m WG7 1 * RPG-7 1

!FiWre 4-4. iW4SA3 MBT ad N1551 AR/AAV Hit Pattern, Southeast Asia (Ref. 4)

terns of these 39 hits are not essentially different from the box, a past use for some immobilized tanks. Today ground
hits on the Ml 13A1 AIW, and the conclusions are the same. combat forces depend more on motillity for effective fight-
The hits are likely to be anywhere on the presented area of ing than any ground force in history. Much of this increase
the vehicle. The front and the right and left sides are ahnost in mobility comes from high-powered, compact engines.
equally apt to be hit, but the rear is less apt to be hit. These The first practical engines used in combat vehicles were the
conclusions, however, should not be extrapolated beyond spark-ignition, or gasoline, type. Then compression-igni-
shoulder-fired, rocket-propelIed antitank weapons. tion, or diesel, engines were used. I.,ately turbine engines
have been p~d in the US Ml MJ3T and the Russian T80
4-2 ENGINE TYPES MBT. The ~sians have since returned to a diesel engine
Fire safety of military vehicles could be increased tre- for the T80, Ilandthere is some talk of later versions of the
mendously by simply removing the prime mover (engine) M 1 having dldiesel engine, primarily to conserve fiel. This a
and its fuel system. The vehicle would then become a pill- paragraph d~scribes those engines that have been used, are

4-1o
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MIL-HDBK-684
being US* or will probably be used to power military some limited circumstances this type of engine can burn

o ground vehicles in the near future.

There have been few major developments in military
engines for ground vehicles in the past few decades, and
fuels similar to naphtha or residual products. ‘RIese depend
on engine size, load cycle, starting requirements, and
desired pfXf’OIITEUW
“revolution@ power plants are unlikely in the foreseeable 4. High Reliability. CE engines have a reputation for
future. The guidelines presented in this handbook will be high reliability, and in most cases this reputation has been
appropriate for some time to come. All engines do much the well earned. Tlte CI-type engine eliminates the need for an
same task i.e., convert a combustible fuel to usable work. ignition system—a factor that is a primary cause of spark-
As long as the nature of this task remains the same, danger ignition engine degradation and poor operation. By elimin-
due to fires will exist. ating this sensitive electrical systerm overali engine reli-
The engine types included are compression ignition, ability is improved and a major ignition source for fires is
spark ignition, andturbine. The characteristics of each type eliminated There is another reason for high reliability in
are destibed. Specific details of the fuel system are listed as diesel engines. Because the combustion event is very
well as potential areas for hot-surface ignition. Differences severe, diesel engines must be very rigid in order to with-
fiorn commercial vehicle practices are explained. stand the high combustion pressures. The rigid engine struc-
ture aids in engine durability and reliability by keeping
4-2.1 COMPRESSION IGNITION cylinder bores and bearing surfaces concenrnc for reduced
engine wear.
The compression-ignition (cI), or “diesel”, engine is the
The heart of the CI engine is the fiel injection system. It
primary power plant for current combat and tactical vehi-
must do three things very well and very quickly, i.e.,
cles. ‘Ilk development is due to some very good reasons:
1. Meter the proper amount of fuel into the chamber
1. Reduced Fire Hazard. Due to its wide fuel toler-
2. Inject fiel at sufficient pressures to provide atomi-
ance, the diesel engine can bum fuels with a much higher
zation and sufficient mixing of the fiel and the air
flash point than a spark-ignition engine. lhis is the primary 3. Initiate the combustion event by proper timing of
reason for using CI engines in military equipment and was the injection.
the basis for “dieselization” of the ground vehicle fleet in The equipment comprising the fuel injection system must
1959. In 1987, in order to reduce further the number of fuels

0.,
have very close tolerances due to the high pressures
provided in a combat zone, the Department of Defense involved. Consequently, the diesel fuel injection pump is
(DoD) sekcted JT-8 to be the fuel for both aircraft and normally the most costly component of a diesel engine.
ground vehicles. JP-8 has a lower flash poin~ 38°C (1OWF), Because of these close tolerances, tie fitel must have lubric-
than DF-2, 60”C (140T). Therefore, it may be more readily ity, and the fuel injection pump must be protected from dirg
ignitable given a sprayor leakageresultingfromperforation water, or other contaminantts that may be present in the fuel-
or rupture of fuel containers due to ballistic or accidental Some of the Jet A-1 fuel used in Southwest Asia (SWA) in
damage or wear-out of fiel lines or fittings. early 1991 is believed to have been lacking in lubricity. It
2. High Thermal E@ciency. The CI engine enjoys was, but other factors were found to be the causes of
good thermal efficiency for three reasons: lean combustion, degraded engine performance. “Quick fixes”, such as add-
high compression ratio, and low pumping work. Due to the ing a lubricant to the fuel, resulted in more severe problems
nature of the Cl engine, it can run with no lean misfire limit (Ref. 12).
of the fuel and air mixture. Thus the combustion can occur A typical diesel fuel injection system is supported by a
with very lean mixtures. The leaner the combustion, the fuel-water separator, a primary fuel filter, and a secondary
higher the themal eftlciency. Lean combustion is the pri- fuel filter. lhe fuel-water separator acts as its name
mary reason that diesel engines are more fuel efficient than impties-it separates water from the fuel. These devices use
gasoline engines. The compression ratio can be much higher centrifugal force and coalescing materials to provide good
than it can for a spark-ignition engine. This also has a direct separation. A prinmy filter catches the largest contaminant
effect in raising engine thermal efficiency. The diesel engine particles. Many primary filters use a depth-type medium and
does not have a throttle to restrict airflow into the engine, filter down to 70 pm. The secondary fiel filter is in series
and this lack of pumping work reduces energy losses due to with the primary filter and emplaced just before the injec-
friction. tion pump. These tilters normaily use barrier-type media
3. Wiie Fuel Tolerance. Because the CI engine is not and filter to 10 pm.
as explosion limited as the spark-ignition engine, the fuel The specific layout of these components varies fim one
requirements are somewhat rdaxed. Fuels for CI engines make of engine to another and in many cases from one vehi-

,, have a cetane number requirement rather than an octane cle to another, but all components have a common functiom

O number (Ref. 11). The band of fuels that can possibly oper-
ate in diesel engines is wide. Although the most commonly
used i%els in Cl engines are distillates, or kerosene, undez
l%ey must providecleanfuel to the injection pump at ade-
quate flows and pressures. ‘lltis function normally requires
additional pumps to push the fuel through the filter system

4-11
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MIL-HDBK-684 ~
Sometimes fuel heaters are included to aid in cold weather 4-2.1.1 Fuel Feed
operation by preventing fuel waxing, and often a fuel-burn- The components of the fuel feed system were previously
ing intake heater is used to aid cold starting. mentioned. ~Bnefly,(1) the fuel cell stores fuel, (2) the fuel a
There are several features that distinguish combat diesel transfer pm$p pushes fuel through the fuel-water separators
engines from commercial diesel engines. Engines of combat and filters ~ ‘m injection pump, (3) the injection pump
vehicles must be protected from ballistic impacts. This pro- times, meas~es, and delivers fuel under pressure to the cyl-
tection leads to armoring and placing the engine in a rather inders through injection nozzles, which atomize and spray
small compartment and thereby reduces heat transfer to the fuel into the cylinders, and (4) when an excess fuel flow is
atinosphere. This heat transfer provides the bulk of the cool- needed for heat transfer or other reasons, plumbing is pro-
ing, of commercial engines. Fans are used to increase the vided by which the uninfected fuel is returned back to the
heat transfer to the forced-air coolant. Usually very high fuel cell. In addition, there maybe other fuel transfer pumps
output is required from a small package for combat vehi- used to relocate fuel within or between fuel cells.
cles. To reach this output, most engines are modified for Obviously, at a junction of each of these components with
increased power output with sacrifice in engine life. Nor- the fuel feed lines, there is a potential for leaks. The follow-
mally, this means the engine is operated at higher brake ing are reasons why this is an important concern in combat
mean effective pressure (BMEP)—a term for thermal load- vehicles:
ing—and at higher piston speeds. Both factors have a detri- 1. There is severe vibration in combat vehicles (partic-
mental effect on engine life, the extent of which is ularly trackkd vehicles) due to the operating environment
determined by individual engine designs. Since the combat and the drive train.
diesel is operating under higher power than a commercial 2. Because the components are enclosed in an armored
diesel, it will normally have higher component tempera- hull, it is m~ch more difficult to detect leaks, and the leaked
tures. A diesel engine for a commercial tmck can be fuel tends to collect within the vehicle rather than drain
expected to last from 8000 to 12,000 h, whereas the specifi- overboard.
cations for future combat diesels are for 2000 h. This is a These difficulties me true not only of the lines as they attach
very strenuous requirement based upon the power output to each of $ese components but also with the removable
required. componentdi particularly the fuel filters.
Since the US Army has a mission to operate in all theaters In a typical 560-kW (750-hp) diesel engine used to power
of the world, the engines and their support systems are some main ~attle tanks, the engine burns approximately 136
a
designed to operate under a wide variety of environmental k@h (300 lb/h), or 163 L/h (43 gaIih), of fuel. Some diesel
conditions. ~ese engines must start unaided at –32°C fuel injecti~n systems, however, require as much as 2.5 to 9
(-25”F) within five minutes and be able to operate with suf- times as much fuel as the engine burns to be circulated
ficient cooling at full power to’ 52°C (125*F). The dirty through the pump for cooling—a factor largely dependent
environment encountered in many locations places a great upon injectdr type and engine make. The problem occurs
deal of emphasis on air filtration equipment. when the ~el used for cooling is returned to the fuel cell
The capability of US equipment to perform well under and heats up the fuel stored in the cell. In many instances,
adverse conditions was amply demonstrated in Operation the bulk fuel in the storage cell can reach temperatures
Desert Storm. Combat and tactical vehicles designed and higher than we flash point of the fuel. At”the flash point the
prepared for use in Central Europe were shipped to South- fuel vapors ~formcombustible mixtures that can be ignited
west Asia and without major modifications for acclimation by an exter$d source, such as ballistic impact or an electri-
were used in a major combat operation with no massive cal spark. p the fuel cell, e.g., the cell of the APC
breakdown of vehicles. This major operation included a M113A3, isl:exposed to hostile observation, the heated fuel
sweep through extremely hostile terrain by a highly mecha- cell can be much more readily detected by hostile observ-
nized force, and the following comment was made: ers’ infraredsensors than a heated fuel cell buried within the
“Throughout the theater, there appeared to be an vehicle. Some of these infrared sensors, however, are sensi-
above average amount of engine fires. The extended tive enough to detect a vehicle with buried heated compo-
use of the vehicles, the heat and sand, all probably nents. For ~s reason, consideration has been given to using
contributed to those fires.” (Operations Officer, First a cooler in’ the return line to reduce the temperature of
Armored Division Artillery, Ref. 13) stored fuel. This procedure, incidentally, would be counter
The tremendous amount of dust undoubtedly contributed to to the desires of diesel engine designers because some die-
engine overheating because this dust would coat the engine sel engines perform better when the fuel is injected at a tem-
and reduce heat transfer to the surrounding air. Another perature of! 54°C (130°F); therefore, diesel engineers
officer from the same organization stated that because the welcome wdrm diesel fuel.
dust almost clogged the radiators and filters, the crew were The nominal pressure through the fuel filters is approxi-
required to clean dust from these components every time the mately 345 to 689 kl?a (50 to 100 psi). This again is depen- a
vehicles stopped [Ref. 14). dent on engine design and vehicle configuration, but it does

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offer possibility of leakage. The high-presme injection ture in the fuel return system could become (Ref. 15). This

o lines, as found in some engines, carry fuel at approximately

103 MPa (15,000 psi). T%e fuel return, or leak-back, lines
then operate anywhere horn Oto 276 kPa (Oto 40 psi).
te% conducted with a lightly loaded vehicle on a flat track
and on a cool day, showed that the return fuel temperature
can reach the flash point of DF-2 and can exceed the tlash
Three fuel injector types used in US combat vehicles fol- point of JP-8 at k.ast somewhere within the fuel system.
low:
1. Jerk pump, or pump-line-nozzle, system 4-2.12 Hot-Surface Ignition
2. Unit injector system ‘Ihe potential for hot-surface ignition of leaking fuel is
3. Common rail system. very high in combat vehicles. Since the engines run at very
The jerk pump, or pump-line-nozzle, system is used on a
high load, many of the components operate at higher tem-
variety of both combat arid tactical vehicles. b combat
peratures than theti commercial counteqxms. Heat that
vehicles the primary example is the A~S- 1790 engine
commercial vehicles would lose to the environment is
used in the M60 series and in the diesel-powered M48A3
tmpped in combat vehickts and increases the need for cool-
and A5 main battle tanks. In the jerk pump there is a plunger
ing air and the power required to supply that air. The confin-
that pumps fuel through individual high-pressure lines to a
tiel injection nozide at each cylinder. This system has the ing armor and the close packing of components within the
disadvantage of more areas for potential fuel leakage due to combat vehicle limit air movement through the vehicle to
the muhimde of high-pressureinjection lines. An advan- cool these components. To minimize the weight of the
tage, though, is that sometimes engine control is better due encompassing armor, space in combat vehicks is also mini-
to the governing and advance features built into this type of mized. A major requirement in combat vehicle design is to
he] injection pump. This system has the even greater reduce overall vehicle volume; thus the compartments of
advantage of having no need to cool the injector head. the engine propulsion system are very compact- The air
l%erefore, a much smaller quantity of slightly heated diesel requirements for these combat vehicles are extremely high
fuel is returned to fuel cells, and overall vehicle fire surviv- e.g., the MBT M60 uses more than 706 std m3/min (20,000
ability is greatly enhanced. scfhnin) at high rpnt. Because any air that enters the com-
l%e unit injector has the advantage of inco~orating sev- partment must be forced through ballistic grills, the power
eral components of the pump-line-nozxle system into one required to move air through the engine compartment is
0 unit. In this case, there is an individual metering pump that
is part of the injector itself for each cyliider located in the
increased over that required for commercial vehicles.
Two major areas for hot-smface ignition are the mrbo-
cylinder head. This compact arrangement eliminates the charger casing and the exhaust manifold. Exhaust gases of
need for high-pressure injection lines and therefore elimi- combat diesd engines reach temperatures as high as
nates areas for potential leakage. This type of system is used approximately 649°C (1200’’F). A fuel leak onto surfaces at
on the 8V-71T Detroit Diesel engines found in the M 109 this temperature can easily result in a fire. However, this fire
and Ml 10 self-propelled howitzers and the 6V-53 engines need not be started by fuel alone. Engine lubricating oil in
used in the Ml 13 family of vehicles and the light-armored combat vehicles tuns as hot as 121° to 132°C (25U’ to
vehicle (LAW 25. This type of engine is also used in many 270°~, and transmission oil reaches a high temperature of
tactical support vehicles. One disadvantage of the unit injec- 149°C (300”F). This oil moves through coolers, which are
tor is the high flow rate of fuel required through the cylinder
sometimes integral to the engine. At each of these coolers
head. This results in increased heat rejection to the fuel and
are junctions that are potential lealmge paths. A vehicle fire
thus increased fuel cell heating.
can start by ignition of oil and then spread to the fhel tank
common rail systems use a constant-pressure feed line to
area. IJIsome vehicles hydraulic fluid lines are located in the
supply individual injectors at each cylinder with a constant
engine area ‘IIIese Litmsprovide another source of combus-
fIow rate. There is a timing device (in most cases, a rocker
tible fluids.
am aad plunger) at each cylinder to increase the pressure of
A significant consideration in the design and material
the fuel and time its injection into the combustion chamber.
‘l’he components are machined to close clearances; hence selection of engine compartment components is that the
they are less tolerant to uneven heating and require more highest temperatures are experienced after the engine has
cooling than the jerk pump system. The VTA-903 Cummins been shut off by the master switch. ‘IMs effect results from
engine used in the M2/N13Bradley F@hting Vehicle SysEm the sudden cessation of forced air cooling. If the master
us= this type of common rail injector systerm This system switch simultaneously dkengages the automatic fire-exdn-
incorporates many of the advantages and disadvantages of guishing system, a fire resulting from poor design or mate-
the unit injection system. It eliminates the high-pressure rial selection could produce severe damage. For proper fire

0 feed lines yet has high heat rejection to the return fuel.
A test was conducted using the AR Ml13A3, which
uses the 6V-53T engine, to establish how high the tempera-
survivability the fire suppression system should remain
engaged at least until the engine has coded off and prefera-
bly should be in an alert standby condition at all times.

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4-2.2 SPARK IGNITION the fuel into that cylinder by controlling the injection pres-
Although the spark-ignition (S1), or “gasoline”, ergine sure, the time of valve opening, and the time of valve clos-
has the advantages of increased power-to-weight ratio and ing. This control can assure that the proper quantity of fuel a
power-to-volume ratio over the diesel, it has one key feature is injected ~t the optimum time with the proper pressure to
that prompted its removal from combat vehicles. Its com- assure corr~ct atomization. Fuel injection systems as used in
bustion system requires a volatile fuel for proper operation. combat ve~cles should not be contised with current elec-
This fact and the desire of the Army to reduce’logistical bnr- qonic fuel Iinjection systems used for automobiles: The
den by supplying a single fuel have prompted the US Army automobile isystems have been developed pnmaril y to meet
to eliminate gasoline-fueled vehicles from current and emissions and fuel economy requirements and in some
future combat, tactical, and support vehicle fleets. The cases to improve performance. Their operation depends
engine is discussed here, though, for completeness, histori- heavily on electronics and is much different from the
cal value, and the potential for use in specialized situations. mechanically based systems previously used on combat
The four-stroke spark-ignition engine operates similarly engines.
to the four-stroke diesel engine. During the intake stroke, a Of particular concern in gasoline engines is routing the
mixture of fuel and air is drawn into the combustion cham- fuel supply line. The fuel line must be routed away from hot
ber. This mixture is compressed to high pressures; at an components not only due to the possibility of&e but also to
appropriate time in the cycle, the fuel-air charge is ignited prevent “vapor lock”, which occurs when fuel boils in the
by a spark plug. The combustion of this fuel-air mixture feed line an~ stops flow to the engine.
causes hot gas to expand and pushes the piston downward
on a power sfroke. T’he combustion products are then 4-2.2.2 ~ot-Surface Ignition
exhausted from the combustion chamber. Hot-surf+ ignition is a greater problem with spark-ignit-
There are limiting factors for this combustion system: ion engine; than with compression-ignition engines. The
1. The fuel-air mixture must be held within a narrow primary reason is high relative temperatures. Because the S1
range of flammability limits for adequate combustion. engine ope&es with a very narrow fuel-air ratio band and
2. The fuel ~ust have specific properties (high octane this band is near the stoichiometric condition, the exhaust
number) to prevent self-ignition (knock) that can quickly gas temperature is higher. Exhaust gas temperatures of
destroy the engine. 8160(2 (1500°F) are easily reached. Thus exhaust system
componen~, such as manifolds and in some cases turbo- -
4-2.2.1 Fuel Feed charger turbine casings, achieve much higher temperatures,
The components of the fuel feed system in gasoline and these temperatures offer greater potential for fire haz-
engines are much simpler than those in diesels. The extreme ard. The autoignition temperature of gasoline, however, is
level of fuel cleanliness necessary because of the close tol- higher than that of diesel or turbine fuel.
erances in the diesel fuel injection pump are not required of Another area to be considered in reducing hot surface
gasoline engines. Although the, magnitudes of fuel flow areas is the ,engine structure itself. Many of the previously
rates are only slightly higher than those in diesel engines, fielded mi\tary gasoline engines were air-cooled. Air-
the pressures in fuel lines are in many cases two orders of cooled engines generally have higher surface temperatures
magnitude” less than those in diesel engines. The tempera- than water-cooled engines; thus the engine surface creates a
ture of the fuel is generally near ambient condition because potential hot source for fuel ignition and vaporization. A
the fuel is usually not used to cool any engine components. significant consideration in the design of and material selec-
Carburetors or fuel injection systems are used to intro- tion for engine compartments is that the highest tempera-
duce the fuel into the combustion airstreani. These devices tures are experienced after the engine has been shut off.
have three functions, namely, This effect results from the sudden cessation of forced air
1. To meter the fuel accurately according to the air- cooling.
flow to maintain the fuel-air mixture within a narrow margin
2. To mix this fuel with the air and vaporize it 4-2.3 TURBINE
3. To control the quantity of fuel-air mixture entering With the fielding of the Ml Abrams MBT, the US Army
the engine and thus control the load. took a significant departure from traditional combat vehicle
Carburetors are relatively simple and generally use a ven- power plank. The turbine engine used in this tank offers
turi principle to determine engine airtlow. A float bowl, or several advantages over the previously used diesel and S1
diaphragm chamber, normally is used to store fuel prior to engines. Al$ough the final determination for the “best” tank
its introduction into the combustion chamber. power plant has not been made, the turbine engine shows
Fuel injection systems are generally much more sophisti- several advantages, such as increased power-to-weight
cated than carburetors. Fuel injection systems have the ratio, increased power-to-volume ratio, potential for quieter 4
capability to measure the air into the cylinder, then meter operation, less vibration, and decreased fuel sensitivity.

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MIL-HDBK-684
‘hew advantages, however, are accompanied by some tial fire hazard when excess fuel collects within the combus-
,, disadvantages. Fuel economy of turbine engines is generally tor can and ignition does not start when intended. The
o poor, particularly under light loads and especially at idle. potential problem of excess fuel in the combustor can is
The engines generally operate poorly under variabte speed even more dangerous under a hot restart condition. Fuel
and load conditions, which are required in ground vehicles. puddling within the turbine compartment is vaporized by
These engines are sensitive to the torsional vibrations of the hot surface components and can ignite quickly. Ignition of
drive train caused by high rotational speeds, although there fuel vapors within the engine compartment also occurs dur-
are. ways to overcome these. The turbine engine requires ing flameouts, because if the engine is operated through a
much greater quantities of air for combustion and internal transient situation and the combustion rate does not keep up
cooling. Large quantities of clean air in a combat environ- with the airflow rote, a flameout causes excess fuel to be
ment am difficult to obtain, and when contaminated with ~ped within the engine.
fuel or oil, the large air filters can become combustion
chambers. Finally, the turbine combustion cans are hot spots 4-2.3.1 Fuel Feed
without equal for igniting spilled fuel, lubricating OA or
The components of the turbine fuel system are very simi-
b@3diC fluid.
lar to those of a diesel. The ntxxsary components include
Turbine engine operation is very simple. A compressor,
feed pumps, fuellwater separators, fuel filters, and an injec-
sometimes multistage axial or cenuifugal, compresses a
tion system. Thus the areas of potential leakage are essen-
constant flow of air. This air enters a combustion can or
tially the same as in a diesel engine. ‘l%e primary
chamber into which fuel is injected. Tltis continuous com-
differences in the fuel system are the constant flow process
bustion process with ho~ expanding exhaust products drives
required versus the intermittent injection in the diesel
a sties of turbines that power both the compressor and tbe
engine and the fact that injection pressures am normally an
outputshaft.
order of magnitude lower than for diesels.
There are some differences in turbines used in ground
Another difference in the he] feed system for the turbine
vehicles fkom the gas turbines typically used to power air-
engine is that tie combustor can is so hot during normal
craft One of the main differences is the incorporation of a

o device recuperator or regenerator in the ground vehicle. This

is used to incxease fuel economy by faking part of the
waste heat in the exhaust and adding it to the air before
operation that it can bake the rubber fuel hose into a
ceramic-like state so that the hose can fracture from normal
shock andlor vibration. This provides a leakage path for the
combustion. This component is expensive, bulky, and oper- fuel to spray on the combustor can. T%e fuel ignites upon
ates at a high temperature, so it constitutes another hot sur- contact with the combustor can, as is described in subpar. 4-
face area for possible ignition of spilled or sprayed 2.3.2.
combustible fluids. Some typical iiow rates follow. A gas turbine engine of
One of the primary differences between the turbine and 1120 kW (1500 hp) flows approximately 306 kgh (675 lld
the piston engines is the nature of the combustion process. h) of fuel. With most turbine engines there is no fuel return.
-.
Combustion in lmtb the Cl and S1 engines takes place Pressures in the fuel line are on the order of rnegapascals.
within the cylinders of the engines, whereas combustion in Some turbine engines have other uses for pressurized
the turbine engine takes place within a special chamber, the fuel. The AGT-1500 gas turbine engine in the Ml MBT uses
combustor can. Because combustion is continuousin the fuel pressure to control inlet guide vanes and power turbine
turbine engine, peak combustion temperatures must be held stators. These movable devices in the engine airflow tract
much lower than in piston engines. Since there is no coding help the engine run efficiently over a wider speedhad
system, the temperatures are controlled by using excess air mngrz however, they also require more fittings and seals
through the combustion process. In other words, the turbhte and thus offer more areas of potential leakage.
engine operates at approximately a 501 air-to-fuel vapor lltere are significant differences in the combat vehicle
mass mtio as compared to 25:1 for the diesel and 15:1 for gas turbine operating in a groupd vehicle environment fivm
the gasoline engine. Therefore, an increased volume of air is the gas turbine in aircraft practice. Engine vibration is much
rmeded to maintain the same power as in other engines. For more severe in the ground environment It is due not only to
this increased quantity of air, large air cleaners are added in torsional vibrations on the drive train but also to vehicular
the Ml MBT. These air cleaners are in a companrrtent par- vibrations caused by a tracked vehicle operating in an off-
tially separated tint the engine. Cornbusdble fluids can col- road environment. These vibrations must be considered not
kc~ so the air cleaners are subject to fires. (See subpar. 4- only from engine design and structural standpoints but also
23.2.) The air cleaner compartment is not protected by the with regard to the.possibility of vibrating loose fuel fittings,
fixed fire extinguisher system, hence a fire in the air cleaner filters, or other componetm around which a leak could

o compartment requires manual extinguishment.

There are also some difkences in the way a turbine
engine starts and stops. Failed cold starts represent a poten-
occur. Not only is there more potential for leakage, but also
maintenance is much more difficult. ‘he combat vehicles
must be maintained “in the field”, in mu& snow, dusL and

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MIL-t-lDBK-684
other poor conditions. The engine is enclosed in an armored The fuel system consists of one or more tiel cells, a
compartment, so parts are difficult to access for inspection transfer subsystem, and the fiel lines, which connect the
and maintenance. The potential for undetected fuel leaks fuel cells t? the engine. The vulnerability of the fuel system 9
increases as the components are covered with dirt and reside of armorecl~vehicles has been documented for both World
in dMicult-to-access places. War II and ;rnorerecent contlicts. “The petrol [gasoline] car-
ried on thej~[BroneTRansporter] BTR-60 makes it liable to
4-2.3.2 Hot-Surface Ignition ‘brew up’ I[burn] if hit. This has earned it the nickname
Potential areas for hot-surface ignition on gas turbine ‘wheeled doffin’ (kolesniy grab) in Afghanistan. White
engines include the combustor can, recuperator, and the phosphorus shells can ignite fuel, especially in external
exhaust ducting system. Although temperatures of the com- tanks.” (Ref. 17). The BTR-60, Fig. 4-5, has two 145-L
ponents, other than the combustor can, are slightly less than (38.3-gal) fuel cells located on the floor of the troop com-
those of a diesel, the size of these components makes shield- pqtrnent, one on each side of the vehicle in the rear. The
ing difficult. For example, a 559-kW (750-hp) diesel general design of the fuel system is shown on Fig. 4-6. This
exhaust system produces approximately 4220 ,kgih (9300 lb/ wheeled v&icle often caught fire’ when it initiated a land
h) of hot exhaust products. By comparison, the 1120-kW mine in Afghanistan.
(1500-hp) gas turbine engine produces 15,615 kglh (34,425 A simili$ vulnerability to fire was shown by Russian
lb/h) of exhaust. products. The size of the duct must be tracked ill?~s. The Bronevaya Maschina Pickhota (BMP)
larger for a turbine engine; thus routing it away from fuel series of yehicles is tracked and diesel powered. These
system components is more difficult. Since the amount of BMPs have a total fuel capacity of 460 L (121.5 gal), 55 or
ducting is high and recuperator’ size is. huge, the stored 70 L (14 or 18 gal) of which is carried in each of two inte-
energy in these components adds to engine heating after gral fuel cells, which are in the rear doors of the crew com-
shutdown and provides pot surface”areas for fuel ignition, as partment, as shown in Fig. 4-7. The remaining fuel is
is described in subpar. 4-2.1.2. In the M 1 series MBT the II cell located between the seats in the passen-
carried in a!fuel
heat from the cornbustor can is so intense mat it has ignited ger cornpm$nent, as in Fig. 4-8. This vehicle is equipped
or melted the rubberized-fabric-covered, steel-braid-pro- with the fire extinguisher system described in subpar. 7-
tected, polyethylene fuel line when the line was mounted 5.1.3.4.2. Ih the Middle East and Afghanistan these BMPs
improperly. The rubberized fabric ignited and the fuel line were repo{~d to have a propensity to burn or explode when
ignited or melted and allowed the diesel fuel to spray onto hit, particu{,a.dyby HEAT warheads, due to the dense pack- 9
the combustor can. This fuel promptly ignited and resulted ing of armqursition and to the fuel-filled rear doors (Ref. 17)
in an engine compartment free. This fire also spread in the and intem~ fuel cells, which form the benches on which the
air cleaner compartment. The tank crew extinguished the air passengers sit.
cleaner compartment fire by pouring water from a 19-L (5-
gal) can through the grill to the air cleaner (Ref. 16). 4-3.1 FUEL STOWGE
4-3 ETJ13LSYSTEM All com~at kehicles use hydrocarbon fuel. This fuel, i.e.,
gasoline, d$esel, or turbine fuel, is liquid and is stored in a
Most fires; even of mobility fuels, can be precluded.
cell*. These fuel cells have been made of steel, aluminum,
Flammable fluids, in fact, almost all combustible materials,
bum only in the gaseous state and then only within a rather
narrow range of fuel vapor to air mixture ratios. A fuel
vapor to air mixture ratio can be too fuel rich or too fuel
lean to bum. A designer should not depend upon. keeping a
mixture ratio too fuel rich because as that mixture spreads
away from “thefuel source, more air is available; this addi-
tional air assures that somewhere the mixture will be com-
bustible. Once a fire starts, the heat increases convection;
thus tie mixture becomes more combustible. The more vol-
atile the fuel, the more probable the presence of a combusti-
ble vapor mixture somewhere in a vehicle. This is the
reason gasoline is more hazardous than diesel fuel. When
diesel fuel is heated, however, it can become almost as vola-
tile as gasoline. Therefore, it is not safe to use diesel fuel as
an injector coolant unless the fuel is injected into the engine Fi&e 4-5. Rear View of BTR-60
I
and burned directly after it is heated. Recirculating heated *In this handbookthe fuel containerof a vehicleis refened to as a
diesel fuel to a fuel cell is a poor practice from a survivabil- ‘<cell”;the te~ “tank”is reservedfor a heavily armed and armored 4
ity point of view. combatvehicle.

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MIL-HDBK-684

Crimped Hose 9 StoPcOck

1
3
Fi!lPipe
GasolineLevelktdexRod(dpstkk) 11
10 GasolirIe FuelCell
GasolineFuelCell
4 AirVent 12 FilterHolder (damp)

0,,
5 Fill Gap 13 Filter
6 GWa&inmno:ump 14 Dmin PI
7 15 Gasoliie? Fuel) Ltie
8 Gasotiit3S@ment Pump

Figure 4-6. BTR-60 Fuel System Schematic

4-3.1.1 Current US Fuel Cell Desigo

Allcwent US combat vehicles use a kerosene-type die-
sel fuel or jet propellant ‘I%e Ml $eri&”MBTs have six
intcmrd fuel cells made of highdensity polyethylene-two
forward (one on each side of the driver) and four to the rear.
There are an upper and lower rear fuel cell on each side of
the engine. l%e two forward and rwo upper rear sponson
cells are cotnpamnented, whereas the two lower rear cells
are in the engine compartment. T%eM 113A2 APC and the
AAV7A1 have one welded, light-gage aluminum fuel cell
high on the left mar side of the troop compartmen~ The
M113A3 APC has two heavy aluminum external fuel
ceils-one at each side in the rear, above and behind the
-4-7. Rear View of BMP-2 tracks, as shown on Ftg. 4-2. The M60 MBT has two
fiberglass, rubberized fabric, or plastic. A combat vehicle welded, light-gage aluminum fuel cells within the engine
may contain one or more fue! cells located anywhere within compartment. The M2 infantry and M3 cavalry fighting
or on the vehicle. These iiel cells are usually vented but may vehicles have two internal fuel cells made of rotary-molded
be pressurbd. The primary t%elcells are fixed within or to nylon 6. I%e upper cell is centered high on the right side,
the vehicle, but the Russians have used supplementary jetti- and the lower cell is on the hull floor in the center of the
sonable fuel drums, primarily to extend the range of the ve- vehicle. Both cells are in the troop compartment. Carbon
hicles for movement 10the battle area. steel fuel cells were used ffom World War I (US heavy tank

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MIL-HDBK-684

26
Fine Fuel Filter , Drain !Pipes
;“
3
Engine
Engine Fuel Feed I%rnp
Ri Door Fuel Tank
LeP @xy’ Fuel Tank
4 Injector Pipeli@
5 Preheater Fuel Pump Fuel @nk Accms Hole Cover
6 Reheater Pump Unit Plug :,
7 Come Fuel Filter Left-fbnd Bench Fuel Tank
8 Right-l-land Bench Fuel Tank Drain pipe
9 Drain Pipe Fuel Qevel Indiior
10 ~; R#J Pump P@ j“
11“ Fuel Valve “
12 : Drain Valve 26 Preheater Fuel Valve
Pipe!ine 27 lnject~r Fuel Return Pipes
;: Fuel Filler Neck
Figure 4-8. BMP-2 Fuel System

Mark VIII) until the US Army switched from gasoline- than an ad~-on componen~ hence fuel cell requirements
fueled to diesel-fueled engines about 1959. The Landing should be considered during vehicle design. The integrity of
Vehicle, Tracked, Personnel (LVTP)5 is an example of a the fuel cell is a major concern with respect to fire safety
vehicle using rubberized-fabric fuel cells (Ref. 18). US and surviva~ility. Fuel cells should be designed to withstand
Army helicopters and counterinsurgency (COIN) aircraft the pressur~~stkges and impingement forces associated with
use crashworthy, self-sealing fuel cells, per MILT-27422 rapid refieling-up to 38 L/s (600 gpm j-and to withstand
(Ref. 19), which were originally developed for racing cars. an internal ~ve~ressurization of 14 kpa gage (2 psig) with-
Self-sealing fuel cells are often considered for use in US out permanentdeformation. It is advisable for fuel cells to
combat vehicles but are not adopted because of their inef- be able to withstand the explosion of ullage vapors. This
fectiveness against antitank projectiles. feature is currently .a requirement for external aircraft fuel
cells, particularly the composite, filament-wound ones. Fuel
4-3.1.2 .l?uel Cell Design Criteria cells shouldllbeprovided with baffles to reduce fuel sloshing
For m~imum performance and safety the fuel cell and aeration, and the LYTP5 and the M 110 SPH both have
should be considered an integral part of the vehicle rather reticulated form in their fuel cells to do this. Both of these

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MIL-HDBK-684
vehicles usc the early Type I, reticulated, lo-pores-per-inch location for the fuel cell(s), the folIowing should be kept in
@pi) orange foam. The latest versions of this foam-MlL- mind:
o B-83054 (Ref. 20), Type m ltl-ppi, dark Wlge, and Type 1. An antitank gunner will normally aim at the center
W, 25-ppi, light beige-have a much longer life, which is of the presented area of the target vehicle, but that target
amnated az 20 years, and are conductive, which prevents vehicle may be at any attitude or partially obscured by dusL
buiidup of a static electric charge during high-speed refuel- fog, or underbrush and probably will be visible for only a
ing. very short time. Usually the gunner will have WtIe choice of
A plastic lining on the interior walis of the fuel cell may where the munition will hit the target. This fact has been
be used to reduce seam leakage and ti hazard in the event borne out by the impact patterns on M48A3 MBTs, M551
of a rupture. Bottom fittings and valves should be installed AR/AAVs, and Ml 13A1 APCs, Figs. 4-3 and 4-4, from the
in a flange or spud designed to accommodate them, should SEA BDARP data and is also discussed in subpar. 4-6.21.
not extend mom than 19 mm (0.75 in.) below the lowest The only diHerence for terminally guided missiles is that
part of the he] cell or sump, and should be protected against they are directed toward the strongest signature on which
damage. The fiel cell should be clean and not prone to rust the seeker guides, such as the source of infrared (Ill) tila-
or corrosion. Coatings, if used, should cover the inttior sur- tion for a heat-seeking missile.
face of the entire fuel celk should not deteriorate in the Iiel, 2. Antivehicular mines can penetrate the bottoms of
and should not degrade or contaminate the fuel in any way. mnoredvehicles, as was shown in other SEA BDARP data
Joints of a metal fuel cell body should be closed by arc-, and in tests of the LYTP5 (Ref. 18). T:lt rod fuzed mines,
gas-, sean-, or spot-welding, by brazing, by silver solder- such as the Russian TKM-2 or AKS, the Hungwian UKA-
ing, or by techniques that may provide heat resistance and 63, or the Czech and Slovak plate charge mines with a side-
mechankd socurement at least equal to those specifically mounted tilt rod, are directed at the bottom of the hull (Ref.
named. Joints should not be closed solely by crimping or by 21). Therefore, no place in an armored combat vehicle is
soldering with a lead-based or other soft solder. truly “safe” for locating fuel cells.
Each fiel cell should be equipped with a nonspil.1opera- A better approach is to locate or design the fuel cell so
tional vent that adequately permits the passage of air and that when it is perforated, fuel is not sprayed or dumped

,:
o the other gases dining operation and that is protected against
entry of ti water, and other debris. The vent should be
adequate to vent gases and air without creating back pres-
within the vehicle. Any spilkcl fuel is directed overboard or
into a reladvely safe sump such as a closed bilge (Ref. 22)
so that ignition within the vehicle of this spilled or sprayed
sure. Each fuel cell should also have a safety venting sys- fuel is improbable. Examples of such designs are given in
terIL which in the event the cell is subjected to fire, will subpars. 4-8.1.3 and 4-8.3.1.
prevent internal cell pressure from rupturing the body of the
cell or body openings (if any). The safety venting system 4-3.1.4 Hydraulic Ram Loads
should activate before the internal pressure in the cell When a fuel cdl is pierced by a shapeddarge jet or
exceeds 345 kPa gage (50 psig) or 5090 of the rated burst high-velocity ICE penetrator, extremely high hydraulic ram
press-, and thereafter the internal pressure should not pressures are generated. In a series of tests descxibed in Ref.
exceed the pressure at which the system is activated by 22, the hydrrdic ram pressures were measured These pres-
more than 34.5 kPa gage (5 psig), despite any further sures provide an indication of the magnitudes that can be
increase in the temperature of the fuel. Any venting of liquid expected. In one case, a jet from a US Army Ballistic
fuel should be overboard and, if possible, not underneath Research IAcmtto~ (BRL) 81-mm, precision shaped
the vehicle. charge generated a peak hydrauiic ram pressure of approxi-
l%e cell and other fuel system components must be mately 49.1 MPa (7126 psi) in a plastic fuel cell when the
designed to operate throughout the range of vehicle atti- siug from the shaped charge was stopped in the simulated
tudes. The design and construction must assure that the cell vehicular armor. in a second case, the same type of shaped
cannot be fiIkd in a normal filling operation with a quantity charge generated a peak pressure of approximately 64.9
of fuel that exceeds 95% of the liquid capacity of the cell MPa (9408 psi) when the shaped-charge slug passed
and thaL when fillerL normal expansion of the fuel will not through the armor into the plastic fuel cell. Impulsive pres-
cause fuel spillage or interfere with cell venting. sure loads like these can rupture many t%el cells. Simiiar
Metal cells and metal fittings of nonmetal cells should be tests with the warhead from an 89-mm (3.5-in.) M28A2
grounded to the vehicle main frame or chassis by electrical rocket resulted in damage to a welded 6.4-mm (0.25-in.)
conductors to prevent buildup of static charges. tick Al 6061 fiel cell shown on Figs. 4-9 and 4-10. These
figures show that the weldments were the principal failures

o ‘, 4-3.13 Fuel Cell LOGitiOll

Much time and effort has been expended to locate fbel
cells where they are less likely to be hit. In selecting the
of the aluminum Advanced Survivability Test Bed (ASTB)
engine compartment fuel cell. A weld expert examined
these faihtres and stated that the welds lacked penetration

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MIL-HDBK-684

Figure 4-ril. Stainless Steel Engine Compart-

ment Fyel Cell After Penetration by a Shaped-
figure 4-9. View of Ahmirmm ASTB Engine Charge/,Jet From an M.2$A2 Warhead
Compartment Fuel Cell Bottom and Rear @cf. 24)
Showing Weld Failures (Ref. =)

Figure 4-10. Front View of fihminpm ASTB

Engine Compartment Fuel Cell Showing Weld
Figure 4-12. Ruptures in a Plastic (Nylon 6)
Failure at Seam Between Front and Bottom
Fuel CeU After Penetration by a Shaped-
Faces (Ref. 23)
Charge~lJetFrom an f$l-mm BRL Precision
Warh~d (Ref. 22)
into the base material of the faces. This illustrates that
welds of metallic fuel cells must be complete and must
MIL-T-274fi2 (Ref. 19) are cored* by shaped-charge jets,
have the maximum strength possible. There were large illustrated ii Fig. 4-13, ~d hence do not necessady pro-
holes at both the entry and exit points, and the aluminum vide a seal. These observations indicate some of the prob-
was not able to withstand the blast and hydraulic ram lems encountered during selection of a fuel cell material and
forces. A similar cell made of 12-~age (2.67-mm or 0.105- configuration.”Some fuel cell designs that have sustained a
in. thick) corrosion-resistant steel (CRES) 304 sustained shaped-charge jet perforation without a conflagration are
the damage shown in Fig. &l 1.Note that the welds held described ti;Refs. 22 through 24. These designs include the
damage was due only to the jet punctures. use of a double wall, as shown in Fig. 4-14, and the confin-
ing of a cell ‘toprevent gross rupture, as shown in Fig. 4-15.
4-3.1.5 Fuel Cell Survivability Enhancement
Where gross fuel cell ruptures occur without fire preven-
tion devices, a conflagration normally ensues. Plastic fuel *?Vhena sharp-edgedpenetratoror a shaped-chargejet perforatesa
self-sealingconstruction,some of the materird is removed, as a
cells have also been known to rupture, as shown in Fig. 4- corer removes the core of an apple. TM action mechanically
12. Crashworthy, self-sealing fuel cell conspwctions per removesmaterialrequiredfor formationof a mechanicalseal. 9

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MIL-HDBK484

(A) Exit Hole

Figure 4-14. Exit Holes in Jacket and Fuel Cell

Wall After Penetration by the Jet of an M2SA2
Warhead (Ref. U)

0
,’
(B) Entry Hole
I?@we 4-13. A Cmsshworthy Caliber 30 Fuel
Cell Penetrated by a Jet From an $1-mm BRL
Precision Shaped Charge @f. 22)

lle vake of this confinement was illustrated in two tesrs

with actuaJ vehicuhr fueJ ceJJs. In one test without the con-
finernen~ the fueJ cell failed at the access porL illustrated in
Fig. 4-16, anda catastrophic fire ensued; in another test with
Figure 4-15. Confinement Box Used With Test
confinement the fiml ceJl failed near the access pcul ilhts- Cells (ltd. 22)
trated in Fig. 4-17, but no sustained life ensued, i.e., the fire-
hdJ, spacer, and fuel ceJJ, as in J?@ 4-i8*, but the fuel,
baJJsdf+xtinguished in 64 ms.
which had been pressurized by hydraulic ~ impinged on
h a series of tests involving extemaJ l%el ceJJs for
the gravel and then poured out through drain holes in the
armored combat vebicJes, use of a barrier between the fiel
bottom of the spacer, iJJustrated in Fig. 4-19. It did not spew
cell and the vehicle provided the protection needed to pre-
into the compartment (Ref. 23). Thus external fuel ceJJs
vent injection of the fiel into the vehicle. In tests in which
with fiei bankra have been shown to provide “safe” stor-
the fuel ceJJ was fastened diredy to the externaJ surface of
age.
the JmJl of the simuJated vehicle, the fbeJ spewed into the
A shaped-c-e jet can darnage fueJ cells severely and
vehicle through the hole perforated by the shaped-charge jet
cause a fuel spray that is ignitable by hot particles coming
in the huJ1. This resuJt occwred (1) when the jet passed from impacts of the paetrator on other vehictdar compo-
through the fuel ceJl, tJte huJJ, and into the vehicle compart- nents. Fig. 4-20 ihstrates the severe damage KE penetra-
ment and (2) when the jet passed through the hull, the v&i- tors can cause to fiel celJs that rdso results in fire.
cle cornpamnen~ the huJJ, and into the fuel celJ. This
spewing of he] into the vehicle compartment did not occur
when a spacer, or banier, containing gravel was emplaced *Fig.U-18 showsthe incandescentglow rwulMg when a shaped-
chargejes passesthrougha vehiclehulLa 1.8-m(tLit)wide com-
between the hull and the fiMJ cell. The shaped-charge jet -n~ - moe vehiclehull. Note that the jet entered the
still passed through the may of lndl, vehicJe compartmen~ fiel cell, whicheon.taittedNo. 2 dieselfuel, but did not exit k

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MIL-HDBK-684

Figure 4-16. Fue!Ceti F@ueat Acc~P1ati Figure 4-~9. Fuel Drainage From Fuel Barrier
(Ref. 22) @cf. 2?),

a
Figure 4-17. Fuel Cell Failure lWarAccessP1ak
!.
.(A) Example A

j (B) Example B
Figure 4-20. Two Examples of an Aluminum
Figure 4-18. Jet Penetration Through Stiu- Engine Compartment Fuel Cell Hit hy a Kine-
lated Vehicle Armor, Crew Compartmen& and tic Ene~ Penetrator After the Penetrator
Fuel Barrier Into Fuel Cell (Ref. 23) P-~Through the Veficle H~ ~ef’. ~~
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MIL-HOBK-Wl

,:
O
Tlw survivability enhancement criteria for fuel cells that
should be used by designers are the following
1. Assure thatthe fiel cell will not suffer gross iupture
9. U a fuel cell is mounted on the external stuface of
an occupied compartment, a baffle should be emplaced
between the fuel cell and the hull to prevent fuel horn pass-
upon ballistic irnpac~ or if the cell does rupture grossly, ing into the occupied compartment through a hole made in
assure that the fuel will not spray into an occupied or engine the hull by a penetrator (Ref. 23).
compartment. 10. Designers of light-armored vehicles must consider
2. Assure tit there is a safe collection location for the the effect of the shqed-barge slug within the vehicle, as
fuel and that the fuel has a path by which it can flow to the well as the je~ (Heavy armor usually traps the slug, but light
collection location or overboard drain. armor does no~) The slug is relatively massive (170 g was
3. Assure either that the fuel cell cannot be pressured the mean mass of 43 copper sIugs from M28 HEAT war-
and then spray fuel into an occupied compartment or that heads.), is hot enough to ignite DF-2, and tmvels approxi-
sprayed fuel cannot reach an occupied compartment. mately 244 rds (800 fth) (Refs. 22,23,24,26, and 27).
4. Assure that the fuel cell is strong enough to wirh-
stand explosion of uliage vapor/air mixture. 4-3.2 FUEL TRANSFER SUBSYSTEM
‘l’hefuel transfersubsystem generally is defined as all of
4-3.1.6 Comments on Fuel Cell Design the components required to rransfer fuel from rhe onboard
TEefollowing observations apply to the design and bca- fuel cells to the engine. These include’ the fuel transfer
tion of fuel calls: pumps, strainers, filters, fuel-water separators, fkel heaters,
1. A fuel cell incorporated into the wall of or within a and lid lines (tubing, hoses, fittings, crossovers, and vents)
compartment occupied by personnel presents a hazard to but do not include the fuel injection pump or carburetor or
those?ersonnel. other nonengine, fbd-consuming equipmen~ such as smoke
2. Location alone cannot be depended upon to *’p- generators, starting aids, or persomel compartment katers.
tect” a fuel cell because vehicles can be hit from any direc- Tltese latter items interface with the fuel transfer systerm
tion by direct-ilre weapons; the probability of being hit fkorn and if not properly designed and mainrainrxL they can have
the rear is somewhat less than it is tiotn the front or sides. a significant impact on overall fire safety. W]th respect to
Although the bottom of a vehicle is not often exposed to the fuel transfer subsystem, the major areas of concern are

0 direct * it is exposed to mines. The top of the vehicle is

exposed to bomblets and to attack from above.
3. External fuel cells should not be detectable by
connector and fitting compatibility, line routing and mate-
rial, and fuel demand and duty cycle requirements. Perfor-
mance and envimnmerttal specifications for these items
thermal sensors. Hot fuel should not be recycled into should consider fire safety and fire stivability by empha-
exposed external fuel cells because hostile personnel using sizing k.akage resistance upon rupture or puncture and
Ill &rectors can easily locate these vehicles. resistance to hea~ particularly when the component is to be
4. Upon balhstic penetration, a double-walled fhel located near an intense heat source.
cell incurs signifimntly less damage to rhe wall in contact ‘l’he location<and placement ‘of fuel system”components
with the fuel than a single-walled fbel cell (Ref. 24). are important fkom both functional and tire safety points of
5. The bilge, if covered to preciude free entry of air, view. Subpars. 4-2.1.2 and 4-2.3.2 state that particular care
is a relatively safe collection location for fuel (Ref. 22). must be taken when routing fuel lines through the engine
6. A plastic lie] cell with an intact containment wfl compartment or when lines are located near exhaust compon-
will not spray fuel into an internal compartment even ents or other heat tmnsfer surfaces. Fuel cdl filling ports
though the wall is perforated and the cell fails grossly (Ref. should be easily accessible and located so that spilled fuel
22). will not contact any part of the exhaust system manifolt.i-
7. A fuel cell should not be adjacent to an air-fiIled ing, electrical components, or other ho~ or potentially ho~
compartment containing a strong ignition source because a surfaces or sparking locations. This fact applies to other fuel
threat could perforate through both the fuel cell and tk system components as well, particularly filters and fuei-
compartment wtlll and provide a passage by which fuel water separators, which require access for element replace-
could reach the ignition source. An example of such an ment and drainage. If these items are located above wiring
undesirable design is a vehicle that had its muffler compart- harnesses or other electrical equipmenh care should be
ment separated from a fuel cell by a 19-mm (0.75-in.) alu- taken to shield or isolate the electrical components since
minum wall at one location and had a cutout in the plastic fuel spilled during element servicing could permanently
fuel cell containing a fbel-iired space heater wirhin a 3.12- damage electrical insulation and present a fire hazard.
mm (0.125-in.) thick aluminum box at another location Normally no part of the fuel system should extend

0
,,’
(Ref. 22).
8. Fuel cells should not be pressurized or allowedto
pressurize.
beyond the widest part of the vehicle nor should t%el tines
be outside the armor envelope. If external he] cells are
used, ingress for the fhel lines must be provided through the

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M[L-HDBK-684
armor. Lines or components extending below the bottom on from the fuel-carrying components under all operating con-
the sides, the rear, or the deck of the vehicle must be pro- ditions and temperatures.
tected from impact. Sturdy shrouding or guards must be Guidelines for the design of the compression-ignition 9
provided where fuel lines or components tie exposed to engine and ~as turbine fuel systems used in military vehi-
stones thrown by vehicle wheels or tracks or where they can cles are giv~n in the Fuel System Design Handbook for Mil-
be stepped on by operating personnel. Elec@crd wiring and itary Vehic!es Applicable to Standard Army Re~eling
connectors must also be protected to prevent abrasion and Systems (S.L$?S)Compatible Vehicles (Ref. 28).
breakage, which, in addition to negating the circuit, could i
become a source of ignition. 4-3.3 F~L LINE CONSTRUCTION AND
lle probability of diesel fuel spray from a fuel line can ROUTING
be decreased by reducing the pressure in ~e fuel line. If
Fuel lines and other fuel-carrying or -containing compo-
atmospheric pressure is used to force the WI to flow, there
nents should, in most cases, be isolated from hot surfaces.
is a much smaller probability of fuel spraying out following
The exception is the primary fuel filter that is often located
a ballistic impact. Fuel system components should be
i~ the engine compartment as close to the engine as possible
designed and packaged, e.g., in a single casing; insofar as
so it will benefit from the radiant heat emitted by the engine
possible to reduce the number of connecti~ points so that
during cold \weather operation,
the number of potential leakage “points c~ be decreased.
Fuel linds can be either first-quality steel tubing (pre-
Components should also be designed to produce the ~~-
ferred) or fle~ble hose and should be designed for two
mum pressure drop attainable. Suction or low-pressure,,fuel
times or more pressure than is expected in normal operation.
systems are preferred because they are less’ likely to. leak
Copper and~copper alloys should not be used, Flexible hose,
fuel or rupture during operation. In most cases, suction ~d
if used, must have a fuel-resistant synthetic rubber inner
low-pressure fuel are possible from the fuel cell to the fiel
tube, reinfo~g inner braid, and a cover resistant to fuel,
injection pump.
Locating fuel lines and hydraulic lines in the bilge is a lubricating ,Ioils, mildew, and abrasion. As a minimum
requirement, the flexible hose must be able to withstand a
less vulnerable solution than routing them through the crew
suction of 6,7.7 kPa (20 in. Hg) without collapsing, a work-
compartment. Any spray would most probably be deposited
on the walls, top, or bottom of the bilge; however, the bilge ing pressu#e of 1.7 MPa (250 psi), and temperatures
is less likely to promote a sustained fire (Ref. 22). If, how- between -5 1°C (–60°F) and 121°C (250”F), although some
applications may require withstanding wider temperature a
ever, a pressurized line is used from the fuel cell to the
engine or if a suction line could result in siphoning, an auto- ranges. The hose should not crimp due to bending and
matic fuel line shutoff that responds to significant pressure should be resistant to bending. When steel tubing is used,
changes should be provided. Such an automatic shutoff sys- short pieces of flexible hose often provide the relative
tem, i.e., one that senses pressure in the return side of a fuel motion of vhrious elements of the fuel system. Flexible hose
system, is not recommended because it would immediately is often use~ at the inlet to the injection pump to serve as a
cripple the mobility of a vehicle that otherwise would be surge dam~er to smook out pressure pulsations. Careful
able to move to safety to effect repairs. routing of’ fuel lines cannot be overemphasized. Lines
The design and use of fuel system heaters require careful should be routed where they are protected from damage due
attention because they introduce energy into the fuel system to hazards or heat and where the fuel will not spray onto hot
and can bring electrical components into close proximity to spots after accidental or ballistic puncture of the line. Care
the fiel. free types of fuel system heaters—in-fuel cell, in- must be t~en, however, to keep the number of bends and
Iine, and filter-are comrhonly used to ass~e adequate fuel fittings to a minimum. The tubing or hoses should be
fiow during cold weather operation., In-fuel cell and filter secured to the vehicle at regular intervals to prevent failure
heaters rue, used mainly to assure fuel flow during engine due to excessive load and vibration and to avoid shifting
start-up, whereas in-line heaters are used to maintain fuel while in seqvice. Flexible fuel hose per MIL-H- 13444 Type
temperature during engine operation. In-fuel cell and filter 3 (Ref. 29) has proven quite span resistant. In fact, it has
heaters are usually electrically operated; in-line heaters may withstood ~e impact of a shaped-charge slug (Ref. 22), but
be all-electric, all-coolant, or combined electric plus cool- the fuel line couplings are not self-sealing as was demon-
ant. Electrical units often start to heat fuel the instant the strated in a lest, shown in Fig. 4-21. Fuel line fittings should
ignition is turned on. All coolant units rely on heat trahsfer be of top quality, and all connections should be capable of
from the coolant and therefore reiyire an operating engine. withstandi~~ a pressure of 1.7 MPa (250 psi).
Electrical units should automatically switch on or off as the Fuel sys~emcomponents should be readily accessible for
fiel temperature passes through preset liniits. They should inspection land maintenance. Fuel system design should
have integ@ circuit breakers with a reset switch to prevent carefully consider the need for fuel line redundancy, a fea-
overheating in the power assembly in case of an electical ture that can work for or against vehicle fire survivability. 9
short. All electrical components must be physically isolated Although redundancy can be a strategy to increase fuel sys-
,’
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fWIL-HDBK-684
.—— . . ... . . . ... ..—..—-—.-
Either DF- 1 or DF-A could be supplied in winter rather than

o DF-2. Where JP-8 is normally used in summer, it will also

be usable in winter. An alternate solution for winter opera-
tions would be to include a fuel heater in the winterir.ation
kit for the vehicle concerned.

4-3.S LESSONS LEARNED

Many ‘lessonshave been learned on the subject of making
the fuel system of combat vehicles less vulnerable to fire.
These lessons concern (1) design of the vehicular bilge, (2)
Repxintedwith permission.CopyrightG AeroquipCorporation. selection of engine types, (3) design and Iocation of fuel
Fii 4-21. Perforation in Se&Sealing Hose cells, (4) design and location of fuel lines, and peripherally,
(h@in#j -t Did ~Ot $&d (Ref. ~) (5) design and location of space heaters and (6) design and
location of smoke generators.

tern reliability and decrease combat vulnerability, redun- 4-3.5.1 Design of Vehicular Bilge
dancy can also increase the potential for fire if not carefully In a series of tests to establish the propensity of a v&icu-
designed and implemented. By definition, redundant sys- lar bilge to sustain a DF-2 ftre, the following conclusions
tems can double the area presented for hits, provide ttddi- were established
tional sources of fuel leakage, and greatly increase system 1. A fire ignited with a propane torch would not be
complexity. Redundant systems must have control valves to sustained in a covered bilge even with DF-2 near its flash
isolate damaged components in order to control fuel leakage point if there were floor plates covering the bilge, even
so that the operational circuit can continue to function. though there were finger holes in these floor plates as well
These systems require sensors and fast-acting valves, as as leakage paths around the edges (Ref. 22).
well as a preconceived battle damage control strategy.
2. A rag protruding above the surface of the DF-2
could provide sufficient wicking to support a sustained fire,
0 4-3.4 FUEL TYPES
The propensity of gasoline to ignite readily over the tem-
but the DF-2-wetted wall of the test fuau.re would noL Also
reticulated foam or aluminum mesh (Explosafe? could not
perature ranges ncnmallyencountered incomb~ from -40°C provide su.t%cientwickage to sustain combustion (Ref. 22).
(-40°F) to 49*C (120XF), was a major factor in the decision 3. Hot DF-2 sprayed on the steel walls of a test fixture
in 1959 to convert all US combat vehicles to diesel fuel. Sim- would not burn unless there was a strong fire within the fix-
ilarly, to lessen the hazardthat gasoline-type fiel pnx.eute& ture that heated the fixture sufficiently to vaporize the fuel.
the US Navy converted fkom WI toJP-5 for all carrier-based
‘II& sprayed fuel would be.dd and then flow down the wall
aircmftafterdisasuous iires in the USS Lexington in 1965 and
into the bilge where it would pool but not burn. Once the
the USS Forrest/din 1967.
fixture was heated sufficiency for the DF-2 to vaporize, the
l%e decrease in vulnembility of diesel-fueled US combat
DF-2 would burn.
vehicles is due solely to the fact that kerosene-type fuels
The lessons learned are
must be at a higher temperature to vaporize sufficiently to
1. The use of high-flash-point fuel can make fuel fires
have a combustible air-fuel-vapor mixture above the surface
more difllcult to ignite and easier to extinguish in the early
of the fiml. Heated DF-2 provides just as ignitable an air-
stages than the use of low-flash-point fuel.
fuel-vapor mixture as cold gasoline. Also DF-2 sprays are
2. Rags and other wickhtg materials must be kept out
almost as ignitable as gasoline sprays given a ballistic
impact through a fuel tank. Burning DF-2 produces almost of the bilge and out of open crew compmments.
the same quantity of hea& 4A537 kJ/g [18s00 BTU/lb), as 3. The bilge is a relatively safe location for collection
gasoline, 44,164 kJ/g (19,000 BIW/’lb). Therefore, once a of leaked fuel when air convection is minimized. (Retention
&e starts and burns long enough to heat the DF-L a DF-2 of leaked fuel in the bilge, however, is not recommended.
fim is as hazardous as a gasoline fire. ‘fltis collected fbel should be drained overboard at the first
When more volatile liquids are mixed with less volatile Oppomlnity.)
liquids, the flash point of the resulting mixture is basically 4. A fire within a combat vehicle should be extin-
that of the more volatile liq,ui4 as described in subpar. 3- guished long before the vehicle heats sufficiently to vapor-
25.7.1. Therefore, use of a mixwre of DF-2 and JP-4 for a ize the fuel.

0
,!. winter fuel would be a poor practice. Instead, a fuel with the
volatility of JP-8 over the range of winter temperatures
should be supplied for winter use rather than field mixtures.
5. The fuel should be kept as cool as practical because
cod fuel provides less vapor to ignite. Heat must be added
to fuel before it can burn.

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I
I

MIL-HDBK-684 ~
4-3.5.2 Selection of Engine~es cell was ~de of the same armor plate as the tank itself,
Ettgines are not selected for fire safety. I%e safety, how- 12.7-mm (0.5-in.) steel plate, and the feed system was
ever, should be considered in engine selection, design, and changed from gravity to pump. Even though the tank 4
installation. The main features th~t should be considered are designers dad learned this lesson, the men in the field did
that the fuel should not be returned to the fuel cell when not, as is il~kstrated by the following story.
heated, the engine should not present hot spots for fuel igni- Tanks w~re first used in combat toward the end of the
tion, and the fuel lines should have minimum exposure to Battle of t$ Somme in September 1916. Forty-nine Mark
ballistic darnage. IV tanks were assigned to attack German lines between the
Preferably, if the fuel is used as a coolamt, the heated fuel Combes ravine and Martinpuich. The Mark I tanks had a
should be consumed, not returned to tie fuel cell. A diesel single gasoline cell liigh within the driver’s compartment to
engine that uses a jerk-pump injection system hea~ the allow the use of gravity feed, and this internal fuel ceil was
stored fuel much less than a diesel engine bat uses either a found to be excessively vulnerable. (The Mark II and HI
unit injector or a common rail injection system. For fire sur- tanks were interim models with somewhat heavier armor.)
vivability, diesel engines that use a jerk-pump injection sys- The Mark IV tank incorporated all the changes found neces-
tem are prefemed to ones using either a ttqit injection or a sary in the Mark I. Among these changes were that the
common rail injection system. If a diesel e~gine does use an petrol* fiel cell, now with a 227-L (60-gal) capaci~, was
injection system that returns heated fuel, that fuel should be moved to tl$ rear of the tank and made of 12.7-mm (0.5-in.)
cooled before it is returned to the fiel cell. armor platet and the fuel feed was by vacuum. The exhaust
Another lesson is that hot spots should be either elimi- was moved~to the top of the tank and a silencer (muffler)
nated or shielded, or he] and other combustible fluids installed. me armored, external fuel cell on the rear pro-
should be routed so they cannot contact the hot spots given vided a ~e survivability enhancement, but sometime
any combination of component malfunction, accidental or before the Battle of Carnbrai, someone decided that 227 L
ballistic damage, or mechanic’s error during maintenance (60 gal) w+ not sufficient. A field modification was made to
,“ operations. install a res,erve cell on the roof of the vehicle, adjacent to
the muffle~l over the rear personnel exit. The armored,
external fuel cell can be seen on Fig. 4-22, as can the muf-
4-3.5.3 Design and Location of Fuel Cells
fler and re~l exit. The added reserve fuel cell was in the rect-
One of the first lessons learned by the British in 1916 was an=tiar boil enclosing the muffler, and it protruded upward
that a gasoline fuel cell made of light gage steel should not 9
out of the rectangular box approximately the height of “tie
be emplaced over the engine within the combination engine box. Thus ~ added fuel cell was an easily hit target.
and crew compartment, as was done in the Mark I tank. In During the Battle of (htnbrai, one of fie Mmk ~ ~nks
the next model in which a change could be introduced,, the entered the ~village of Havrincourt. A bullet hit the reserve
Mark IV, the fuel cell was relocated from inside the vehicle petrol cell &n the roof, the petrol ignited, and the flaming
to the exterior rear; see Fig. 4-22. The rear-mounted fuel petrol streamed down inside the tank. The crew tried to
extinguish @e fire, but the fumes eventually forced them to
evacuate arid take cover in a shell hole. The Germans tried
to rush the tank, but the tank commander climbed back
inside and lield the Germans off by firing through the door-
way. He ki~led eight Germims with his revolver. He then
managed to~bnng the fire under control and called the crew
back (Ref. 31).
This sto~ illustrates the value of amnored, rear-mounted,
external fuel cells. It also illustrates how an excellent sur-
vivability enhancement device can be negated by the poorly
conceived a’tidltion of another device. The reserve fuel cell
was not ~ored and was located where it could easily be
hit, and fuel leaking from the cell would ignite because the
adjacent mu~fflerwas a strong ignition source. The resuhing
fire could ~ender the vehicle uninhabitable and block the
primary exi~.
After the shooting stopped in 1918 even the tank designer
~ Armored, External Fuel Cell forgot this $uel location lesson because the tanks again had
light gage s~eel fuel cells located within the vehicles when
F@re 4-22. External, Rear-Nlount@ Ar- /
a
mored Fuel Cell of the Mark IV Tank *TheEnglish:refer to gasolineas “petrol”,

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the next major war began. Generally, all US and British but is exterior to the vehicle and to provide a barrier to pre- .
armored vehicles continued to use internal fuel cells tmtiI chtde the fiel spray and an extinguishant to preclude a iire-
the development of the Ml 13A3 armored personnel camier. ball from an initial spray (described in Ref. 23 and subpar.
The Ml 13 MW was initially gasoline powered, but to 4-8.3,1).
reduce the potential for fire and to reduce the logistic
requirements of stocking two types of fuel, the M113AI 4-3.5.4 Design and Location of Fuel Li.rses
was diesel powered. The diesel engine selection, however, During a visit by this writer to Fort Wed, TX, a rrminte-
was the Detroit Diesel Allison 6V53, which has a unit injec- nance sergeant explained how an engine fire had occurred in
tor system that returns heated fuel to the fuel cell. This an Ml MBT when an elbow connecting the fuel line to the
engine selection partially negated the fire safety advantage fuel regulator was rotated 90 deg (Ref. 16). Due to the rotat-
of using diesel power. The fuel cell was located in the upper ing of the elbow, the fuel line passed the combustor can at a
Iefi rear wall of the troop compartment immediately adja- distance of approximately 51 mm (2 in.). (The fttel line is a
cent to the stnall door in the samp. On the night of 3-4 rubber hose covered with a woven wire sheath) The heat
November 1969, Troop I of the 3rd Squadron, 1lth Armored from the combustor can was so great that it baked the rub
Cavalry l?egirnen~ was in a night defensive position. The her, boiled off the volatile constituents, and left a brick-like
North Vietnamese attacked shortly after midnight (DAM* residue. This brick-like residue cracked ffom engine vibra-
381,383, and 385) and by coincidence hit the right sides of tions and provided passages throu@t which the fuel sprayed
three Ml 13A1 APCs with RPGs at almost the same location on the combustor can and ignited- The sergeant stated that
and angle of obliquity. In at least two vehicle% a shaped- this series of events had occurred on more than one Ml
charge jet traversed the troop compartment and entered the MBT to his knowledge. This improper elbow installation is
fuel cell on the left wall of the vehicle. The teds of these not precluded by fuel line length or component design.
two attacks were described by the BDARP investigation When such a potential hazard exists, either a fuel line that
‘“l%ese are the worst damaged vehicles we have looked at. can withstand the elevated temperature should be used or
‘I%eii.rewas so IIOLthe hulls melted and dripped. It was also the fuel line, the elbow, and/or the fuel regulator should be
the first time that we have seen an MC that caught fire designed to preclude incorrect assembly.
because of a hit in the fiel [cell]. Is there any evidence of a In two instances in SEA (lX$l’Js 312 and 388) M113A1
wadwad for the RPG other than the HEAT type? Possibly a APCs were hit by shaped-charge jets, and hydraulic fluid
delay fuze or something that would explode after penetra- fuel lines, bcawd within a covered bilge, were severed. In
tion was made.”. The third vehicle had a stnd fire, which neitJter case, however, was fire reported. This preclusion of
apparently initiated explosives stowed within; the vehicle a sustained fire within a covered bilge was also demon-
was completely destroyed by the explosion.
strated in tests (Ref. 22). llte lesson to be learned is that a
‘fh.issame circumstance of a shaped-charge jet traversing covered bilgeis a comparatively safe location for fuel lies.
an open compartment to enter a fuel cell was repeated in a
series of tests performed in 1986 (Ref. 22). In Test 26 of that 4-3.5.S SeIection, Desi~ and Location of Space
series, shown in Fig. 4-23, the jet traverses the compart-
Heaters
mertq aImost immediately a spurt of fuel, burning on the
~hery, comes back across the compartment in Fig. 4- In several incidents reported by the US Army Safety Cen-
23(D). l%is is undoubtedly the phenomenon that occwred ter, fires have occumed where a fuel line to a space heater
intwoofthose three APcs. had leake~ where space heaters had not been purged after a
At least three vehicle modifications using passive fire previous use, or where objects had been placed on or near
prevention or suppression techniques have been effective the space heater or its ducts. In most cases, the soldiem
for this event- The first technique is to constrain or reinforce using the vehicle were not taking proper care of the equip
the fuel cell so that it will not rupture with a hole larger than ment; however, these troops are expected to use these vehi-
that punctured by the shaped-charge jet and to provide an cles for extended periods, under the most stressful of
extinguishant and/or inerting agent for the jet to release, conditions, and when they are probably extremely
which prevents ignition or suppresses combustion (Test 27 exhausted. l%erefore, the equipment must be designed to be
of Ref. 22). The second technique is to replace the existing user-liiendly, i.e., to require a minimum of maintenance or
fuel cell with a double-walled fuel cell and locate the extin- adjustment to be fail safe, and to prevent the placement
.@hant or inerting agent between the two walls, as is thereon of what could be hazardous items. There is some
described in Ref. 24. (T%e double-walled fuel cell is evidence (Ref. 32) that some of these heater fires may be
described in subpar. 4-8. 1.3.) The third technique is to relo- due to an emor in qualifying heaters for use from a second
cate the fuel cell so that it is not within a vehicle side wall source even though the operator’s instructions apply only to
heaters from the first source. Whatever beaters are used
*Refers to document acquisitionnumbers in the SURVWCfiles; must be simple and safe. Heaters are essential because the
see -subPar.4-1.2 temperature tilde armored vehicles usually is colder than

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MIL-HDBK-684

(A)t=O (D) t= 20 ms

II

(E) t= 35 ms
.,
t

(C)t=7ms (F) t= 100 ms

1

Figure 4-23. Progression of Combustion in ~est No. 26 (Ref. 22)

,,

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MIL-HDBK-684
the temperature outside in the winter. The lesson learned is uid. Pneumatic systems can be affected by condensation and

o to design the heater to preclude fires or explosions as well as

to heat the vehicle.
fleezing of moisture in the gas or by oil in the gas. The
mechanical elements of all three types of systems can be
affected by m and all three types of systems and their
4-3.5.6 Smoke Generators mechanical eIements can become inoperable by ballistic
Modern armored vehicles need to be capable of Iaying damage. AN tie types of systems must have power
both an immediate small-scale smoke screen and a heavier sources.
long-term obscuration. For the fit purpose, a cluster of The basic choice for power in combat vehicles is either
smoke grenade launchers are mounted on the turret of most electric or fluid power. A shorted electric power line is a
combat vehicles. For the second purpose, a smoke screen strong ignition source that can ignite hydrocarbon fluids and
can be laid by spraying diesel fuel in the m~er or exhaust other combustible materials, and elecrnc shorts have ignited
pipe of the vehicle. This is the system used for both the MO the propellant of cartridges, cased and uncased. Leaked
and Ml series of MBTs and for the BFVS. hydraulic fluid can flow or spiny over large areas and when
In the iire incidents database collected by the USASC, ignited, burn vigorously. GeneraIJy, the fire hazard potential
there are at least two incidents of the fuel line to this smoke is not the dominant determinant for the choice of an ancil-
generator leaking and permitting diesel fuel to collect in the lary power system. This paragraph contains information on
rnuffier or exhaust pipe area that later ignited and resulted in fluid power systms. Electric power systems are discussed
a t%e where there was no fixed tire extinguisher or fire in par. 4-5.
detector. T%edesigner must assure that fluid systems do not
permit collection of combustible fluids where combustion 4-4.1 POWER MEDIA CHOICE
can occur that will damage the vehicle. Fluid systems can be either liquid or pneumatic. The liq-
uid systems usually use a hydraulic fluid, which can be
4-4 HYDRAULICANDANCILLARY petroleum bas~ water base@ or synthetic. Each liquid has
POWER SYSTEMS its own peculiarities, which require additional system com-
Ancillaryproversystemsare used to rotate turrets; to lay ponents and design features. Since hydraulic systems have

,,
0
weapons; to move ramps, dozer blades, and cranes; to lay
and retrieve bridges; to operate munition handling equip-
ment; to apply brake% and to perform other tasks.
been used extensively, designers and maintenance persomel
tend to favor them. Pneumatic systems often use air for the
fluid; steam or the products of combustion of a rnaterid
AIIcillary power systems require power elements and such as solid propellan~ have also been used.
mntrol (e.g., sensing and signaling) elements. Both types of
elements use energy from electricity, pressurized or flowing 4-4.1.1 Liquid Systems
liquids (hydraulic) or gases (pneumatic), or a combination Liquid fluids include the petroieum-based MIL-H-5606
of these sources. Most electrical power systems are wholly (Ref. 37) and MIL-H-6083 (Ref. 38) described in subpar. 3-
electric for both power and control elements, but most 3-3, the fire-resistant ML-H-83282 (Ref. 39) and MIL-H-
hydraulic power systems use elecrnc control elements. 46170 (Ref. 40) described in subpar. 3-3.1, and the nonflam-
Pneumatic systems are used least (Refs. 33-3S). The fuel mable MIL-H-53119 (Ref. 41,) described in subpar. 3-3.2
regdation and inlet systems for the X211 nucka.r-conven - Water-based hydraulic fluid MIL-H-22072 (Ref. 42) is used
tional turbojet engine (Ref. 36) used pneumatic power and in Navy aircraft catapults. The petroleum-based MIL-EI-
control elements. A combination of hydraulic @wer and 5606 and MIL-H-6083 burn readily in spray or mist form
pneumatic controls was used in both the bellrnouth bypass and will burn sustained from a pool. The tire-retardant fluids
syslem for the air intake of the F4 Phantom aircrdi and the ML-H-83282 and MIL-H-46170 will burn readily in spray
inlet spike control of the GAM 77-A Hound Dog missile. or mist form but will self-extinguish in a pool. The nonfhm-
All of these systems convert to mechanical motion eventu- mable M3L-H-S3119 will not burn as a mist or spray or
ally. fimm a pool, but it is toxic and harmfid to personnei on con-
All fluid power systems am hybrid because they all use tact and has not yet received Environmental Protection
mechanical devices. Most sensors have a mechanical out- Agency (EPA) approval as being benign to the ozone layer
pw which usually is transduced to an electrical signal. Most of the earth. Water-based MIL-H-22072 is approximately
output from these systems is converted into mechanical 50% ethylene glycol. Thus once the water is removed, the
motion, usually linear or rotary. ethylene glycol will burn. Also the ethylene glycol is toxic if
Electrical systems are subject to electromagnetic interfer- swallowed and otherwise harmiid to personnel upon skin
ence (EMl) and can become inoperable by exposure to contact. Sohnions of potassium acetate or calcium chloride
strong electrical inputs, such as a lightning srnke or shotting could be used to satisfy low-temperature requirements,
of an ekxmicai power line. Liq,uid systems can be affixxed would be nonflammable, could be benign to humans, cart be
by excessive heat or cold and by contamination of the liq- made benign to metals and elastomers, and could have addi-

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MIL-HDBK-684
tives for lubricity, but these solutions have not been tested matic bottles have been demonstrated not to project frag-
as hydraulic fluids. ments when!lpunctured (Ref. 43). * The Russians used an air-
Most hydraulic fluids have additives to provide the bottle-powered system to start T55 MBTs. The bottle could
needed lubricity,. oxidation and corrosion’ resistance, and be pumped ~up by hand so that the noise of an auxiliary
sometimes the needed viicosity.’ Some have additives to engine wou{d not disclose the position of the MBT, and the
raise the boiling point or to lower the freeze”point. Very few air system could better withstand cold than could electric
liquids are usable neat, i.e., unadulterated. These liquids batteries. \
have different operational temperature ranges based prima-
nl y’upon their freezing and boiling points mid how tempera- 4-4.1.3 System Specifications
ture changes alter them chemically. The power source for When a ~ye~cular fluid power system is selected and
these liquids is usually a pump. The systems often use accu- installed in a vehicle, it is imperative that the fluid for that
mulators—reservoirs that use a pressurized g~ to maintain system be specified in considerable detail. If a nonflamma-
a high pressure on the Iiquid-and sumps-reservoirs to ble fluid is desired, it must be specified, and the military
collect the liquid at low pressure to feed to the pump. There specification must contain firm test requirements to assure
are also filters, valves, piping, actuators, gears, vane or that the fluid is truly nonflammable. Therefore, the vehicle
nu~ting disc motors, sensors, and other devices. Elasto- designer must specify the fluid that should be used in a com-
meric items, such as seals or diaphragms, rnu~t be compati- bat vehicle to obtain the necessary fire survivability.
ble with the liquid used and able to. withstand: the Government purchasing agents are not allowed discretion
environment in which the system operates. “ in selecting: the materials to be used in equipment. The
agents mus{ijustify purchasing any material that is not on
the publish$d qualified products list (QPL) of the military
Pneumatic systems can be made for air, steam, products specification, or equivalent, for the material designated for
of combustion, or other gases. Air systems ‘can operate hot use in a s~cific vehicle. Therefore, if a designer determines
or, with appropriate demoisturizing, cold apd in a radioac- that a spqcl~ fluid must be used to assure fire survivability
tive envtionment. Steam systems operate hot. Products of of a given ~ehicle, he must specify that fluid or prepare a
combustion from these systems start hot and then cool off to specification for it. The designer should also determine that
ambient temperature; these systems have to be designed there are q$dified suppliers of the material or notify tie
accordingly. Power sources for pneumatic systems include equipment program manager that special action must be
ram air for aircraft, pumps, combustion chambers such as taken to assure the needed material is available.
solid propellant cartridges or turbine engine combustion
cans, or any other device or phenomenon that can produce 4-4..2 C&PONENT LOCATION, MATERIAL
quantities of gases at above ambient pressure. The compo- SELECTION, AND PROTECTION
nents of pneumatic systems include plenums, valves,
The locafion of hydraulic components and the potential
motors, actuators, filters, sensors, piping, orifices, nozzles,
for damage ~andsubsequent release of hydraulic fluid are of
bellows, and’ other devices. Again, seals and diaphragms,
prime concern. Extreme care must be taken in designing the
which may be elastomeric, must be compatible with the
system and ~ocating the components so that the risk of fluid
gases and operating environment.
release into ~anoccupied compartment or onto a hot spot in
Pneumatic systems can be temperature compensated and
the engine compartment is minimized. A brief discussion of
are inherently less sensitive to environmental changes, pa-
the general types of hydraulic systems used will aid under-
rticularly air systems, than most other control or power sys-
standing of the associated fire risks.
tems. Air, steam, and products of combustion are not
Hydraulic systems can be described by a few general cat-
combustible. Steam and hot products of combustion are
hazardous. Air can be used in temperature t%nges that are egories that: should be considered when designing the sys-
not hazardous to personnel. Personnel unfamiliar with pneu- tem for fire survivability. First, there are closed-loop and
matic systems may think that a pneumatic system is less sta- open-loop systems. Hydrostatic transmissions are typically
ble or less accurate than a hydraulic system, but this closed-loop i!systems because the inlets and outlets of the
assumption is not correct. VWh proper design, a pneumatic pump and t$otor are connected directly to each other and
system can be,jttst as stable and accurate as a hydraulic sys- the reservoir serves only to collect internal component leak-
tem, amdit can have a faster response (Refs. 34 and 35). For age, condttlon the fluid (filter, cool, etc.), and provide
example, flowing air systems are not sensitive to dust con-
taminants in the air. As a contaminant, oil might be differ- *A fiberglassireinforcedspherical bottle, approximately457 mm
ent, but even oil would tend to pass throtigh the system, (18 in.) in di~eter, was pressurizedto 9.38 MPa (1360 psi) with
gaseous nitdgen and perforated by a 7.62-mm (0.30-cal) arrnor-
particularly through pressure dividers, and not affect perfor- piercing (AP) bullet traveling 792 nis (2600 fbk). There was no
mance. Air motors are well-developed and air-powered explosion or \productionof secondary missiles. The bullet perfo-
actuators are in use in many places. Filament-wound pneu- ratedboth sides of the bottle.

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MIL-HDBK-W4

,,,i replenishment fluid. Hydrostatic transmissions usually have

the capability to reverse direction of the fluid flow so that
ural. Pamsitic shielding is protective shieMing that has no
load-bearing m other subsystem function. Convemely, natu-
O the low-pressure line in one flow direction becomes the
high-pressure line in the reverse flow direction.
ral shielding is protective shielding that is primarily struc-
tural or load bearing.
Open-loop hydraulic systems are the most common type Parasitic shielding offers no secondary benefits and has
used for actuation of hydraulic cylinde~ motors, and other disadvantages such as an increase in system weight and in
actuators. In open-loop systems the low-presswe return time and effort during inspection or maintenance. Natural
flow from the actuators is usual.Iy ported back to the reser- shielding is the preferred method to shield hydraulic com-
voir. The pump provides flow in only one ditwtion, ponents. To take advantage of natural shielding, directly
although the direction of flow to an actuator may be vulnerable hydrauiic components are located away fi-om the
reversed by means of a directional control valve. The actua- periphery of the vehicle in more protected areas witin the
tor may contain a spring or springs to provide a fail-safe inner stmcture of the vehicle. Such a technique eliminates
feature. most of the disadvantages associated with pamsitic shieldi-
There are two main ~s of open-loop hydradic sys- ng. Burying hydraulic components within the vehicle struc-
tems: open center and closed center. The open center desig- ture, however, has a disadvantage in accessibility for
nation refers to fimction of the directional control when in maintenance and inspection unless adequate provision is
the neutral position. When actuation is not reqti full made for access.
pump flow is returned to the reservoir under low pressure The hydraulic system for the M109A6 SPH was made
tRrough the “open center” of the directional control valves. less vulnerable by moving the hydmulic accumulator to a
These systems usually have a fixed displacement pump so separate comparttnen4 which is illustrated in Fig. 4-24, in
t.bat when only a pornon of the flow is required for actua- the left tint of the turret. ‘his change shortened some
tion, the remaining flow must pass through a relief valve to hydrmdic lines and enclosed this accumulator with steeI.
prevent overpressurization. The hydropneumatic recuperator for the cannon was also
The second type of open-loop hydraulic system has a placed within this compattmen~ therefore, the largest
closed center, i.e., when actuation is not required,the center hydraulic fluid and recoil fluid containers were compart-
of the directional control valve is closed and blocks pump mentalized Access to this compartment is provided only
flow. The pump in this case is usually a variable displace- from the exterior of the vehicle.
ment pump that will automatically adjust itself to prwluce
zero flow when the flow path is blocked. There are many 4-4.2+1 Fump
different variations-e.g., pressure compensated, pressure
and flow compensated, and power limiting-+f this type of When a hydraulic pump converts mechanical power into
system. The most common function that is usually present fluid power, it must be located close to a mechanical power
in any of these variations is pm.ssure compensation. Under source. Generally, hydrrmhc pumps are driven by the engine
pressure compensation, displacement of the pump is regu- or aansmission of a vehicle: Sometimes for Iow power
lated to provide a constant pressure regardless of what frac- requirements hey are driven by an ehm-ic motor using the
tion of the full flow capacity of the pump is required. In a electrical power of tie vehicle. This method of driving the
purely presumcompensated system, the high-pressure side pump by the engine or tmnsmission uses either an internai
of the system is always at this pressure-compensated level, lubricated coupling or an external unlubricated coupling or
except when flow demand exceeds the fiow capacity of the belt.
pump. A common source of slow leaks in most hydmulic sys-
Reducing the physical size of components of a hydraulic tems is the rotary shaft seal of the hydraulic pump. ‘IMs seal
system reduces the probability of the system being hit by a wears due to abrasive dus~ v~ing temperatures, and fric-
threaL Secondary bene6tS bm this system shrinkage tion iiom high speeds. In addition, the shaft may not rotate
method of vulnerabtity reduction incIude (1) reductionof exactly concemxically with the seal. Any one, or any combi-
the amount of vehicle space required to contain the hydrau- nation, of these factors often conrnbutes to a slow leak of
lic system, (2) weight reduction, and (3) ease of installation the seal. For an internally driven pump, this leakage is con-
and maintenance. Specific techniques include relocation of tained in the engine or transmission. For an externally
lines, manifolding, and fluid volume reduction. Since the driven pump, this Ieak first creates a wetting around the
system with the small components has to work against the pump shaft and eventually leaves a puddle. This leak must
same lo~ the hydraulic pressure would have to be be handled in the same manner as similar engine oil, uans-
increased. This increased pressure would produce a greater mission fluid, fuel, and lubricant leaks.
spray given a line puncmre, which could produce a greater When the hydraulic pump is located in the engine com-
probability of igpition. ment. it is subjected to tie ambient conditions of the
Shielding can be provided to fimher reduce direct contact compartment, Under nomrd operation the pump shouId not
vulnerability. Shielding can be classified as parasitic or nat- be subjemed to temperatures exceeding the temperature lim-

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ML-HDBK+84
M182 Gun Mount
(ModifiedM178) Microdrnate
M284 Cannon ‘ydp
( Keviar Span
(Modified M185) su~~ssion
\ \ \

Hydradic ~ Secure Voice

/
COmpartmerJ Driverk Night and Digital
Vision Dewe Communications

Courtesyof BMYCombatSystems,a Divisionof HarscoCorporation.

Figure 4-24. SPH lM109A6 Paladin $hlifkations

,
its of its elastomers. Embrittlement of elastomer material To reduce the weight of vehicles, hydraulic reservoirs
due to excessive heat can result in a slow leak and subse- were made, of lightweight aluminum approximately 6.35
quent fire hazard. mm (0.25 in.) thick. In one series of tests shaped-charge jets 9
Unless the pump receives direct physical damage, it is passed through such reservoirs (Ref. 25). These lightweight
unlikely to be a direct source of a gross hydraulic fluid leak. reservoirs disintegrated, and the hydraulic fluid became an
T.f,however, a condition exists in which the normal pressure extremely hazardous fireball. This result occurred in five of
control valves become disabled and allow the pump to over- six tests. Inlthe sixth test, from the description of the dam-
pressurize, the drive mechanism may fail, an internal failure age, one would suspect that the jet entered the ullage, i.e.,
of the pump may occur, a hydraulic line may rupture, and/or the air space above the hydraulic fluid. In four more tests, a
a high-pressure cavity of the pump itself may rupture. In the 6.35-tnrn (0.25-in.) thick mild steel jacket was emplaced
latter two situations the pump will continue to pump fluid over the alpm reservoir. In all four tests the aluminum
until the reservok is drained. One level of redun~c y reservoir chsintegrated, but the steel jacket maintained suffi-
should be available to avoid such an occurrence, or another cient integr$y to reduce the resulting fireball greatly. The
weak link must be designed in the system to prevent an rpaterial of the reservoir was changed to 6.35-mm (0.25-in.)
external rupture. This weak link may be in the pump drive, thick mild steel. In a subsequent series of seven tests, the
e.g., a soft keyway or shear pin, or it may be internal to the steel reservoir: were perforated by shaped-charge jets; fires
pump or valving, e.g., intentionally thin or weak sections occurred but were again much reduced in size and violence.
that separate outlet from inlet. In another series of tests the addition of powder packs con-
taining powdered potassium bicarbonate reduced the dura-
442.2 Reservoir tion of the fireballs below 250 ms (Ref. 44). Consequently,
The hydraulic fluid reservoir usually contains the largest steel reservo’iri should be used in combat vehicles, and con-
concentration of hydraulic fluid in the vehicle. The same sideration should be given to incorporating a threat-released
care must be taken to protect it as is used to protect the fuel fire extinguishant, unless a nonflammable hydraulic fluid is
cells. The hydraulic fluid reservoir should be located in used.
close proximity to the hydraulic pump to minimize the pres- Also associated with the reservoir are other components
sure drop in the suction line to the pump, especially in cold that condition the fluid. These include the filtration system
weather. The most probable location for the reservoir “isin and the cooling system, Very basic, low-performance
the engine compartment or close to it. Location in personnel hydraulic s~stems may rely on the reservoir for cooling by 4
or ammunition compartments should be strictly avoided. convection land radiation and as a place for contaminants to

4-32
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MIL-HDBK-684
settle OULIn systems that rely on the reservoir for cooling, difficult to clean up can be avoided If an open drain over-

o the reservoir must be placed where it can receive sufficient

air circulation. Air cooling requires a strong flow of air over
a hydraulic fluid container. This provides a si@ificant
board is not possible, a length of line should be run fi’omthe
bottom of the reservoir to a place where it can easily be
drained externally. This drain valve or plug must be pro-
amount of atmospheric oxygen in a region in which a ballis- tected to minimize the possibdity of the hydraulic system
tic perforation could cause a spray or mist of combustible being inadvertently drained.
fluids and could provide a strong ignition source. Thus there
is an increase in vehicle vukrability, which could require 4-423 Accumulators
armor protection for alleviation. Hydraulicaccumulators are used primarily for two pur-
A similar problem exists with reservoirs that use air cool- poses, namely, as a fluid power storage device and as a pres-
ers. The reservoir itself may be smaller in size than convec- sure attenuator to absorb pres.sum spikes. They exist in
tion-cooled systems and be placed in a more protected various configurations for storing the energy. The most
location; however, the cooler must be located in a high-
common method of operation is to compress an inert gas,
vekxity airstrearn and may need armor protection.
usually nitrogen. llte pressurized gas and the accumulated
Another option for cooling the hydraulic fluid is to use a
fluid are separated by either a flexible ekistomeric bladder
liquid heat exchanger that uses the engine cooling fluid as
that holds the gas or a piston (much like a hydraulic cylin-
the cooling medium. Tlis would not apply, of course, to
der, but without a rod). In either case the gas is usually pre-
vehicles with air-cooled engines, unless a separate liquid
charged to a preset pressure, which must be exceeded before
system is provided for the hydraulic system. ~ option
the accumulator will begin to accumulate hydraulic fluid.
allows botb the reservoir and the hydraulic fluid cooler to be
A rupture of any of the plumbing that contains an accu-
located in protected areas, and only the radiator for the non-
mulated volume of hydraulic fluid can be very dramatic. If
flammable coolants requires airilow.
not properly contained, the resulting very short duration, but
‘Ihe reservoir fill cap should be located where it can be
extremely high rate of flow of fluid being released can result
easily accessed and where spiils can be easily cleaned up.
in considerable damage and personal injury. The mpture of
The cap shouId have a level indicator on it, or there should
an accumulator carIgreatly complicate an already hazardous
bean easily visible level indicator on the resetvoir. If the fill
fire situation.
cap is located externally to the vehicle, it should be well-
‘l’herisks associated with accumulators can be minimized
0 protected and as rugged as fuel fill caps. Providing ullage is
as important with hydraulic fluid reservoirs as it is with fuel
by using certain precautions in the layout and design of the
sysumt. l%e accumulators should be located remotely fi-om
cells. Fdl caps and breather caps should be engineered to
witistand the pressure surges of the fluid against them when any occupied compartment, and there should be a valve to
a penetrator passes through the reservoir. shut off the discharge of fluid from the accumulator if a tine
All hydraulic systems require some type of breather sys- or fitting bursts. This valve should be located as close as
tem. As tetnperatures change, fluid loss occurs, Wd as actu- possible to the accumulator. One type of valve that can be
atcm are stroked, the volume of fluid in the resetvoir used is a velocity fuse; it is sitid so tit if the flow through
changes. The most common type of breather has a filter in it exceeds a certain level, it will block the flow. Another
the fill cap to ailow free exchange of air. However, leakage possible valve is a pilot-operated check valve that wouId
out of the fill cap through this filter can result due to splash- block the flow of fluid out of the accumulator unless there is
ing of the hydraulic fluid. a sufficient pilot pressure signal applied to it to indicate that
Another type of breather cap is similar to a radiator cap. It the system is intact.
maintains a 34- to 69-kPa (5- to IO-psi) pressure in the res- An accumulator unloading valve should be used as a gen-
emoir, and it allows air to escape when the upper pressure eral safety precaution, as well as a fire prevention measure.
limit is exceeded. It allows air to enter through a filter with This valve gradually releases the fluid fkom the accumulator
no resrnction. (Some provision must be made to exclude thereby relieving the pressure when the vehicle is shut off.
dm such as was encountered in SWA.) This type of Thus unintentional actuation o~a system function is avoided
breather is less susceptible to leakage from splashing when the system is off. Also, when service or repairs are
because there is usually a positive pressure in the memoir made on the system and fiaings are loosened, the risk of
and no free leak path. To use this type of breather, the reser- fluid squirting all over the vehicle due to unsuspected
voir must be capable of withstanding the small amount of trappedpressureisreducedwith this type of valve. Zhus the
pressure involved. 2hk type of sytem can improve the per- chances of spraying hydraulic fhtid onto a hot surface or
formance of the bydrmdic system by providing a pressur- creating a fluid spill that cannot be easily cleaned up are
ized supply of fluid to the pump. reduced. This pxessuredrain system should have a selector

0,,,;,
Provisions should also be made for the crew to be able to valve switch that permits pressure retention in a cambar sit-
drain the reservoir to clean out contaminants or to replace uation when the hydraulic system is needed while the main
the fluid This drain should be located so that spills that are vehicle power is off.

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MIL-HDBK-684
A precaution that should always be taken with accumula- smaller loti~pressure lines and requires additional pilot con-
tors is to mount them and their connecting lines so that no trol valves. ‘Other considerations that impact the selection of
external forces can cause any of the connecting line fimngs the type of ~ontrol valve actuation to be used are function, a
to fati~e and fail. Preferably @e accumulator should be reliability, ~d fluid type.
rubber mounted, and the line joining it should have at least a If it is no~,possible to eliminate the high-pressure hydrau-
short section of flexible hose. lics, including the hydraulic recoil components of main
guns, from ~theoccupant compartment, precautions such as
4-4.3 CIRCUIT’ LAYOU1’ AND LOCATION using nonflammable fluid or span liners should be taken to
The location, routing, and retention of lines, valves, fit- minimize the hazard of impact by span and to prevent the
tings, and other hydraulic system components can contib- spray of fluid within the compartment. These same precau-
ute considerably to the fire survivabilityy of a vehicle. tions should apply to the engine compartment or other areas
Vehicular vulnerability can be reduced and hazardous situa- that may contain ignition sources. Provisions should be
tions avoided by selection of the proper system design ~d made in the circuit to shut off the flow automatically from
appropriate components. each side of the break if a line ruptures.
IsoIwion of hydraulic subsystem damage, is an extremely All actuators should have crossover load-holding or load-
important survivability technique that should be designed controlling ~alves located at the actuator. An actuator that is
into hydraulic systems. The goal of this technique is to pre- supporting a load can act as a pump and discharge its fluid
vent a single damaged subsystem from affecting the opera- contents if a line ruptures. A crossover load-holding valve
tion of an undamaged subsystem if a redundant system is consists of two pilot-operated check valves, each of which
used. The benefits of using dual controls ti voided, how- allows free flow into each side of the actuator. The pilot
ever, if the controls are not isolated from each other, e.g., if pressure for each check valve is sensed from the opposite
a main line is severed, all hydraufic subsystems become side of the actuator. Thus the only time fluid can discharge
nonfunctional. If this condition occurs and the pumps con- from the actuator is when the opposite side is pressurized. A
tinue to operate, a potentially serious ihmrnability lm.zard. crossover load-controlling valve is very similar except that
could develop. a pilot-operated relief valve is used for applications that
require accurate control of high loads.
4-4.3.1 Hi@-Pressure Side
All direc$orsal control valves whose discharge lines pass
Hydraulic fluid lines are usually highly pressurized and through an ~occupied compartment or other critical areas d
are located throughout the vehicle. Therefore, the hydraulic should havel provisions to shut off the flow if a discharge
power system of a vehicle can be more hazardous thq a line ruptures in order to contain the supply side of the rup-
properly designed fuel system. It is highIy recommended, ture. These ~provisions could include pilot-operated check
therefore, that high-pressure hydraulic lines not be located valves or pilot-operated relief valves that shut off the flow at
in occupied compartments of a vehicle. The entire fluid VOL
the directional control valve or even closer to the pump.
ume of the hydraulic system can be pumped into the com- .,
partment in a matter of seconds if proper precautions are not
4-4.3.2 Low-Fressure Side
taken. A pinhole leak or a crack in a high-pressure line can
present several hazards. R can cause a spray of fluid that can The low-pressure hydraulics include all of the returnlines
leave an ignitable mist or fog in the compartment, as well as from all of @e control valves and also the suction line from
create a serious breathing problem for the occupaats. Also the reservoir to the pump. Although these lines are not
high-velocity jets of high-pressure fluid can result in physi- exposed to ~gh pressures, they must be txeated with some-
cal injury, such as cutting the skin and even injecting the what the same precautions as the high-pressure side of the
fluid into the blood stream. If such an injection were to enter system. Although there will be no high-pressure leaks, poor
a vein so that a mass were to enter the heart, death could line and fitting connections can still leak and leave puddles
result. More probabIe, though, would be a spreading of the of fluid, and ruptured lines can allow the release of large
hydraulic fluid through the tissue, which would result in quantities OCfluid.
severe tissue damage. The rupttie of a low-pressure return line can restdt in the
The location of high-pressure hydraulic lines and compo- discharge of all fluid being returned through that line. In
nents in occupied compartments can usually be avoided by addition, the reservoir side of a ruptured return line can
using remotely actuated control valves. Remote operation allow the fluid from the reservoir to be siphoned out since
can be mechanical by using linkages andlor cables. Pilot the return line usually empties into the reservoir below the
pressure for an actuator is controlled by a smaller direc- fluid level to avoid aeration. Each return line to the reservoir
tional control valve manipulated or pedaled by the operator. should have ,,acheck valve to allow free fluid flow only into
Control valves can also be actuated by using a pilot pres- the reservoi;.
sure, usually less than 1.4 MPa (200 psi). The use of pilot To contain the system fluid on tbe control valve side of a e
control valves replaces the larger high-pressure lines with ruptured ret~ line requires special consideration. If the

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MIL-HDBK-684
return line from a directional control valve to the. resemoir CRES 321 tubes had been filled with Oronite 8515, a sili-
,,
O is in a vulnerable location, the potential for that return line
to mpture must be addressed. Since the return line p~sum
cate ester hydraulic fluid with a flash point of 202°C
(395°F), and pressurized to 27.6 MPa (4(M) psi) before
is usually equivalent to atmospheric pressure, it cannot be being hit by bgments fknm a 23-mm HEIT projectile. Tbe
used as a pilot pressure to signal the conuol of the high- Aluminum 6061 tubing was empty when hit by fragments
-pressure side. (he technique is to install a pressure-regulat- horn the same projectile. These tubes had been located
ing valve in the return line at the resemoir after any coolers behind an aluminum box into which the 23-mm projectile
or filters. ‘lb back pressure of the return line could then be had been fired. Fragments from the projectile penet.mted the
regulated at a low level, i.e., below the pressure limits of the bOX,made of 2.29-mm (0.090-in.) thick 2024-’I3 aluminum
cooler and filter, but high enough to provide a reasonable shee~ before sti,king the tubing. The extreme damage to the
pilot pressure signal. A pilot-operated check valve or a larger aluminum tube and to the two CRES tubes was due to
pilot-operated load-controlling valve could be placed in the impact by both the heaviest-some over 6.5 g (1(K)gr) mov-
high-pressure side just foIlowing the main system relief ing approximately 610 rds (2000 ft/s)-fragments and the
valve. T%is valve should be sized so that as long as suffi- blast horn the 23-mm projectile. Note that the 25.4-mm (l-
cient back pressure exists in the return line, unrestricted in.) outside diameter (OD) CIZIX 321 tube was severely dis-
high-pressure fluid will flow to the system. If back pressure torted and ben~ as well as perforated, the 12.7-mm (0.5-in.)
is lost (due possibly to the rupture of a return line), the valve OD Aluminum 6061 tube was severed and a section blown
will close. For a closed center system the pump flow would away, and the 12.7-mm (0.5-in.) OD CRES 321 tube had a
be retuned directly back to the reservoir through the main short section cut ouu as well as being nicked. ‘llese tubes
system relief valve, and for an open center system the pump were located approximately 51 mm (2 in.) behind the rear
would destrolce. For start-up conditions provisions must be surface of the box, and the box immediately in front of the
made to allow some flow to the return line so that back pres- 12.7-mm OD aluminum tube had a 51- x 76-mm (2-x 3-in.)
sure can build up; the interrd leakage past the pilot-oper- hole cut out by the fragment impacts and blase A series of
ated load conmol valve maybe sufficierm titanium 3% by weight aluminum 2.5% by weight vanadium
(T%3AI-2.5V) tubes had been mounted on the right side of
4-4.4 MATERIAL CHOICES

0,;
the box. These robes were filled with silicate ester hydraulic
The materials used in hydraulic systems can have an fluid and also were pressurized to 27.6 MPa (4000 psi).
impact on the iim survivabdity of a vehicle. Material They were subjected to impacts of “side spray” fragments-
choices must be made for the following areas of consider- 0.9 g (14 gr) moving approximately 1220 m/s (4000 ft/s)-
ation: the hydraulic piping, hydraulic- fittings, and elas- but no blast These TG3AL2.5V tubes were merely perfO-
mmers contained in other hydraulic components. ra~ed by the fragments that impacted. In an earlier test sev-
eral lengths of dry 13-3Al-25V tubing located behind the
44.4.1 Hydraulic Piping box sustained multiple heavy fragment impacts, blq and
Ilydraulic piping systems usually are constructed from -damage similar to that sustained by the CRES 32i tubes.
three types of fluid conductors: flexible hose, tubing, and The silicate ester hydraulic fluid sprayed into the test cham-
pipe. A flexible hose is used to accommodate relative move- ber, ignited, and burned explosively.
ment between components. Most of the stationary piping, Stainless steel lines should be used where possible. Any
however, is either tubing or pipe. The advantages of tubing long section should be supported by insulated clamps to
include better qpearance, greater flexibility, better reusabil- stiffen the section in order to prevent excessive vibration
ity, fewer fittings, less leakage, and simpler battle damage and possibly fatigue and failure. ‘f%e insulating material
repair. The principal advantage of pipe is relatively low should be flexiile and nonflammable, but not rubber.
component cost.
l%e use of flexible hose should be minimkd. Flexible 4-4.4.2 Pipe Fittings
hose is susceptible to damage by heat from engine horspots Pipe and tubing fittings can be either threaded or perman-
and from art existing fire; it may begin to leak and thus pro- ent. Pemmnent methods include various forms of brazing,
vide additional flammable liquid to the iire. The hose is also welding, swaging, and adhesive bonding, and these assem-
susceptible to wear from abrasion, and its fittings are sus- bly methods can be applied where low initial COSLreliabil-
ceptible to fatigue from vibration to the point of rupture. ity, and weight are important factors. Permanent
Flexible hose shoukl however, be used where significant installation, however, makes battle damage repair more dif-
relative external loads that cause deflections are applied to ficult.
the hydraulic lines. Thus overstressing and fatiguing of steel Tltnmded pipe-fitting techniques include tapered pipe
fittings and tubing can be minimiztxi. threads, flanges with O-ring seals, Society of Automotive
An appnxiation of the amount of damage time hydraulic Engineers (SAE) O-ring ports, O-ring face seals, and
lines could sustain can be gained by examining some CRES straight thread ports with metal seals, which include flared
321 and Aluminum 6061 tubing. shown on Fig. 4-25. The fittings.

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MIL-HDBK-684

CRES321,25-mm(l-in.) OD x 1.25-mm (0.49-in,) Wall

T
\r N 6061,12.7-mm(0.5-in.) OD x 0.89-mm (0.035-in.) Wall ~,
II

/ CRES 321, 12.7-mm (0.5-in.) OD x 1.2~mm (0.49-in.) Wall

AI.6061, 6.35-mm (0.25-in.) OD x 0.89-mm (0.035-in.) Wall

Figure 4-25. Damage to Stainless Steel and Aluminum Tubing

mere are several concerns in selecting fitting types with ally cause most elastomeric materials to swell; most seal
regard to fire survivability. T~ica.lly, fittings that contain an designs assume that the elastomeric material swells approx-
elastomer seal are less likely to weep aqd leak over fi imately 59?o~me elastomeric material is selected to minim-
extended period of time. If subjected to high temperatures, ize dissolution in the fluid. Hence butyl and natural
however, the elastomer compound can break down and the rubbers are excluded. Chlorotrifluoroethy lene (CTFE)
seal can fail. On the other hand, fittings that rely on metal- swells, softens, and dissolves rubber, both natural and syn-
to-tnetal sealing are less susceptible to failure under high thetic, and reqqires the use of vinylidene fluoride-hexafluo-
temperatures, but they have a tendency to’ develop weeps ropropylene copolymer Grade G, low temperature (GL~
and leaks under normal operation, particulmly when they for elastomeric seals. CTFE also attacks pure aluminum. As
are subjected to high vibration levels. Because of their his- for water-based fluids, water hydrolyzes the outer surface of
torical tendency to leak, tapered pipe fittin’gs should be r&rile and natural rubbers, i.e., water leaches the plasticizer
avoided, especially on the high-pressure side. ., and causes surface hardening and crazing. If salts are used
What type of fittings to use depends upon which is more to suppress the freeze point of the water, the alkaline salts,
critical, elimination of any continuous leaks or weeps that such as potassium acetate ( KC2H~Oz)*, could attack pure
may provide fuel for an ignition source or ininimization of aluminum, but could passivate steel, whereas the acidic
the chance for subsequent leaks given the presence of ~gh salts, such ai calcium chloride ( CaClz)*, could corrode both
temperatures and an existing fire. steel and aluminum. Neoprene is not recommended for use
with either ~petroleum- or water-based fluids because it
4-4.4.3 Elastomeric Seals swells in the presence of the petroleum component. Simi-
!,
One challenge of designing hydraulic fluid systeny is
*lWheneither~,potassiumacetate or calcium chloride is used in air-
ensuring the compatibility of the fluids with’the elastomeric craft or ground vehicles, the formulation used should include cor- 9
seals and metals. The pemoleum-based hydraujic fluids usu- rosion inhibitors.

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MIL-HDBK-W4

,,
o
kirly, both natural rubber and butyl swell. The capabilities of
elastomeric materials with various types of hydraulic fluids
are shown in Table 4-3.
4-4.5S Hydraulic Fluid Line Protection
The test program involving simulated behind-antmr
debris impacting pressmized fire-resistant hydmulic (FRH)
fluid tubing (Ref. 46) (described in subpar. 3-3.4.1) provides
4-4.S LESSONS LEARNED design information and potential survivability enhancement
4-4.5.1 beating Hydraulic Lines Near Hot Spots techniques. I%merty et al found that FRH fluid per MIL-H-
The USASC records document sevetid incidents of Ml 46170 would emerge from a 304 stainless steel tube in the
Iv13T engine compartment fires that occurred when a form of a misL ignite when exposed to an ignition source at
hydmulic line fitting failed due to fatigue and provided a a temperature below the FRH fluid flash poinL and bum to-
completion. They also established that tubing perforation
spray of hydraulic fluid onto the hot combustor can. The
could be predicted using a simpte extrapolation of THOR
spray ignited on contact with the hot can, the fire bunted
equations (Ref. 47) by assuming that the CRES 304 would
through the hydraulic lines and increased the leakage, and a
react as does mild steel. ‘I%eyfound that the tubing was less
major engine compartment fire ensued. The HaIon fire
likely to be perforated when the fragment size approached
extinguisher extinguished the fire, but as soon as the Halon
the tubing diameter. They also found that perforation of the
concentration dropped to the point at which it no longer
tubing was not a function of the internal pressure.
inhibited combustion, the iire reignited since there was still
llte two sunivability enhancement techniques that they
hydraulic fluid in contact with the hot combustor can. This
tested, but did not optimize, were (1) using steel shielding
process was repeated for a second lire extinguisher action over the hydmulic tubing and (2) enclosing the hydraulic
(manual this time); then the crew used portable fire extin-
fluid tube in a layer mbe and packing the annular space with
guishers on the flm andlor summoned other help.
a powdeted fire extinguishant. ‘I’heshielding was to prevent
Solutions to this challenge include (1) not locating
rupture of the hydraulic fluid lines. Tbe fire extinguishant
hydraulic lines where they can spray fluid onto hot spots, (2)
jacket was to preclude sustained combustion. Both tech-
using nonfhmmable hydraulic flui~ (3) eliminating or cov-
niques were effective.
ering the hot spots, (4) using electric power instead of
hydraulic power, {5) designing better lines and fittings or 4-5 ELECTRICAL SYSTEMS
their installation, andlor (6) using a more effective fise-
0 eminguishing system, i.e,, one that cools the heated metal
items below the ignition temperature of the combustible flu-
The design of wiring for military vehicles shouJd be
addressed fkom the inception of the vehicle design itself.
The appropriate military standards should be consulted dur-
ids. ing all design phases. Easy accessibility to all electrical sys-
tcm.components for ease of field service and repair must be
4-4.52 Hydraulic Fluid Line Cut Wlt.b a Toreb addressed. Methods to prevent the electrical system from
In one incident in the USASC database, a mechanic sev- becoming thejgn,ition s~urce for.bs W be integmted tito .
eredapmssuriz ed hydraulic fluid line with a cutting torch the system design. Abrasion and breakage of wiring have
while working on an M 110 SPH. The hyd.rtudic fluid always been a problem. Corrosion of electrical contacts and
sprayed out and ignited. l%is error might not have happened wire surfaces produces resistance heating, which can be an
if the lines containing ikmmable fluids were color coded ignition sourtx. These problems should be addressed during
red. the ckwign phase to circumvent future problems and help
prevent fires.

TABLE 4-3. ELASTOMERIC MATERIALS CONIPATIBILITY (’Ref. 49

H%’DRAUUC FLUID NATURAL NEOPRENE NITIUI& BUTYL FLUOROCARBON
RUBBER
Petroleum-based* P F Ex P Ex
Cl-FE”” P P P P G
Watex-basedt F F G F Ex
Ex=excellent. G=mo&F=fair,P=poor
*Basedupon oil resistancedata in TableA3-10,Ref. 45.
**Based upon Parker ReportDD3562 Ref. 45.

0
~Basedupon wwer%teamresistancedata in TableA3-10,Ref. 45.
Reprintedwith permission.Copyright@Parker Hamifin CorporAon.

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MIL-HDBK-684
Future electical and electronic subsystem requirements Germans had to recharge the batteries in the tank to con-
and functions of combat and tactical vehicles are to be tinue operating their radios (Ref. 51).
defined in accordance with the Standard Army Vetronics Electric power is a feasible alternative to the hydraulic @
Architecture (SAVA) (Ref. 48). SAVA provides more effi- power system currently used in US combat vehicles; the
cient integration of the vehicle electrical systems and real- details have~ be worked out.
time integration with the electronic battlefield: ~,
The four functional SAVAsubsystems are (1) data control 4-5.1 V~LTAGE CHOICE
and d.isrnbwion, (2) power generation and management, (3)
Presently; US military vehicles use a 24-V dc system.
computer resources, and (4) crew contro~s and displays.
There are pros and cons to going to a higher or lower volt-
SAVA is to be implemented as a family of basic modular
age circuit for power. A higher voltage circuit is more effi-
hardware and software elements, i.e., building blocks, that
cien~ can lower contact resistance, and decreases current
can be assembled in a variety of configurations tailored to
requirements. Shock hazard and arcing, which may cause
the requirements of a specific vehicle. SAVA permits the
fires, however, become a much greater risk. A lower voltage
designer to select a higher voltage level (270 V dc) in addi-
circuit increases current flow, and wire sizes would have to
tion to the nominal 24 V dc under the power generation and
be adjusted~for this increase in current. With a lower volt-
management subsystem with accompanying safeguards.
age, contact resistance or any corrosion on the wiring can
The capability is achieved through conversion or dual gen-
cause exce$sive heating and result in insulation melting,
eration.
arcing, or. fike. The 24-V dc system is a compromise estab-
Vehicular subsystems, such as, fire detection and extin-
lished as a\ standard for military vehicles. Some combat
guishing, should consider the interface requirements of
vehicles, hdwever, also have higher voltages for special
SAVA. SAVA has the ability to recognize Wd service a
equipment. ~Asof May 1993, combat ground and air vehi-
vehicular fire emergent y, but the agency responsible for
cles being ~esigned may use 270-V dc for some of their sys-
procuring a specific vehicle must approve the SAVA design
implementation because of the stringent time and reliability tems. For example, some of the newer combat vehicles
might use 270-V dc electric power for turret drive and/or
requirements for firing the extinguisher using a bus system.
Finally, SAVArequirements should be considered in making power loader for the main gun.
choices regarding the voltage of the system, circuit desio~, Storage batteries located on modem combat vehicles
and interconnecting wiring, including material. (Ref. 49) must provide both the power required to start the engine and
the considerable power required by the many systems of the a
h. alternative to the hydraulic power system for gun and
turret is an electric power system. The French use an elec- vehicle during extended periods of use when the engine is
tric power system for turret and gun in their latest MBT, the not operating. In some vehicles the storage batteries provide
Leclerc, and the Israelis have selected an electric power sys- power during load peaks while the engine is operating.
tem for their Merkava III. These requ~ements, combined with the vehicle requirement
The US Army Armament Research, Development, and for operation. in a wide vtie~,of severe environments, pose
Engineering Center has explord” the feasibility of using a significarit challenge to combat vehicle designers. Two
electric power for the timet and main gun of the MIA1 types of storage batteries are commonly used to provide the
MBT with the following results (Ref. 50). The electric necessary power, narnely, lead-acid and nickel-cadmium.
power system could achieve a 20 to 30% decrease in power Lead-acid batteries are the primary reservoir of stored
system weight and volume over the current hydraulic power power because they are best able to provide the large
system. The electric system has higher efficiencies for amounts of power over extended periods at environmental
dynamic loads, but the hydraulic system performs better for extremes. For a variety of reasons, modem combat vehicles
static loads. A comparative evaluation of electric versus use several lead-acid batteries wired together in series and
hydraulic power systems indicates that an electric system p~allel to provide the necessary power at the 24-V dc sys-
should be easier to maintain. An electric system might be tem voltage. Several disadvantages of such batteries, in
subject to EMI, whereas a hydraulic system would not, addition to; the large volume they occupy, relate to their
except for the electric controls of the hydraulic system. potential for being an ignition source for fire. Lead-acid bat-
T’here are advantages and disadvantages stated in Ref. 50 teries must! be kept charged at all times to preclude early
for each system, such as quiet operation for an electric sys- failure. Thus a spark hazard can exist if the batteries are
tern, especially in a static situation, but batteries must be overcharged. Overcharging the batteries can also result in
recharged. In Cassino in March. 1944 some New Zealanders the genera\~ of combustible gases. During servicing or
detected a German tank that had been built into the cellar of replacement, connections can generate sparks if a load is
a budding by hearing the tank motor running. The tank crew present, or $inadvertent shorts can occur. Battery connector
had been dwecting artillery fire onto the New Zealanders corrosion cim cause excessive heating and become an igni-
from within the New Zealand position for five days, but the don source. Finally, the corrosive nature of the electrolyte a
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MIL-HDBK-684
combined with the need for battery servicing can lead to operational, point of view. For further information on the

o accidental spills of acid on adjacent components.

Nickel-cadmium batteries use an alkaline-based electro-
lyte. Such batteries are used in a wide variety of special pur-
properties of insulators, see subpars. 3-6.1 and 3-6.6.1.
Connectors must withstand the rigors of military opera-
tion and meet the operational requirements of voltage, cur-
pose situations. They can be charged or discharged at high ren~ mechanical strength, vibration resistance, water and
rates without fomnation of the corrosive fumes that are char- corrosion resistance, and serviceability. To facilitate field
acteristic of a lead-acid cell. If a nickel-cadmium battery is maintenance in a combat envirotrmen~ sepamble, quickdis-
sufficiently discharga however, a reversal of chemical conneq keyed connectors that provide stmin relief to the
action can occur and be accompanied by a release of hydro- wires should be used to allow quick electrical component
gen and oxygen, a highly fiammable or explosive mixture. replacement. Connections meant to be permanently installed
For some very high-voltage applications, lithium batter- should be made with a high-pressure joint or solid metal
ies are being considered for use (Ref. 52). For low-voltage joint that is both mechanically and electrically stable.
(24-V de), but high-amperage, use, lithium sulfur dioxide or Printed circuit vehicle wiring should not be considered
lithium thionyl chloride batteries are under consideration, as because it is not readd y field repairable nor carI it withstand
are other batteries (Ref. 53). heavy vibration.

4-52 MATERIAL CHOICES 4-5.3 CIRCUIT DESIGN

Considerationmust be given to the materials used to wire Electricalcircuits within a military vehicle must be prop-
military vehicles. Each wire that delivers electricity to the erly designed to meet operational capabikies safely. ‘fhe
various electrical accessories must be capable of carrying correct wire material, size, and insulation must be seiected
the amount of electricity required by M of the accessories for each circuit. Fuses, circuit breakets, or ground fault
serviced by that wire. Momentary peak current and sus- interruptrxs (GFI)* must be used to protect the various cir-
tained current must be considered for each circuiL ~i that cuits. These fuses, circuit breakers, or GFIs must be rated at
is of too small a size for a circuit can be a potential fire haz- a curreq value above the normal operating current of the
ard due to overheating. Copper should be used as the pri- line they are protecting, but not so high that damage or fire
mary wiring because of its conductivity, durability, and can occur because of an underprotected circuit. M three
devices must be fast acting and sealed to prevent ignition
0 resistance to corrosion. The choice between using solid or
stranded copper wire must be made while considering both
corrosion and fatigue resistance. Solid wire is more resistant
due to an exposed arc in a combustible atmosphere. The cir-
cuit bnsakers should reset automatically when the excessive
to corrosion; stranded wire is more resistant to fatigue load is removed fictm the circuit. l%e use of fuses that must

caused by vibrations and flexing. Aluminum wire should be be replaced when they fail should be avoided if possible
avoided due to its rigidity and the fact that its electric cur- because stocks of fuses would have to be carried and per-
rent densities are 75% of those permitted in copper. The sonnel trained in the properreplacement procedures.Viible
maximum cument capacity for stranded copper wire is a arcing can recurif the reasoi the device malfunctioned was
fimction of many things, such as insulation, temperature, not fixed prior to fuse replacement or circuit breaker or
ventilation, wire length, and bundling, as discussed in ground fault interrupter reset.
AMCP 7t16-360 (F&f’. 54). Coaxial and special purpose Diode protection devices are available to ensure that bat-
cabling must not only meet the operational and current teries are installed with the correct polarity of voltage for
capabilities of the circuit but also should be flexible enough their respective circuits. Wting cables for battery compart-
to withstand the constant vibration. Broken wires and cables ments should be designed so that it is impossible to install
can lead to arcing, which can ignite combustibles. the batteries incorrectly. W~ numbering and circuit tagging
Insulation used on wire and cables should (1) be impervi- should be done to facilitate maintenance. Judicious use of
ous to all of the fluids typically used in military vehicles, (2) connectors in the wiring scheme is imperative. Ehxxrical
remain flexible at low temperatures and throughout its life systems that provide survivability should be redundan~ and
cycle, (3) be flame resistnn~ (4) not produce toxic products circuit breakers should protect the redundancy. An ‘H” pat-
when exposed to fire, and (5) possess high abrasion resis- tern with circuit breakers at the ends of the cable and one in
tance. Some types of insulating materials contain added the center tie cable provides a much greater redundancy
chemicals that inhibit combustion and may reduce or nearly than two separate circuits. Redundant cabling should be
dimirtate smoke. Smoke and noxious fumes from burning kept separate from primary cabling. Ilte redundancy should
or smokking insulation and adjacent materials can induce
personnel to evacuate combat vehicles prematurely. Ww *At%seis a piece of metalthat willmelt whenheated by excessive
current. A circuit breaker is a bimetallic elemen~ whiclL when
and cable insulation used in modern combat vehicles heat~ springsto anotherpositionand opens an ekctric tiIL A
includes neoprene, nylon, and Teflonm. Insulation proper- groundfaultinterrupteris a circuitbr~er, the elementof whichis
ties must be considered from a safety, as well as from an heatedby a current flowto ground.

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MIL-HDBK-684
be automatic so that no mechanical switching is required insulation been nonflammable* or at least self-extinguish-
when a primary line is lost. Redundancy of critical circuits ing**, the !Ivehicles could have been repaired much more
should be evaluated during the circuit design. The type of quickly. t
power plant to be used must be considered when discussing i
redundancy of wiring and ““limp home” capabilities. Diesel 4-5.4.2 Electrical Fusing Improperly Sized,
and turbine engines generally keep running after loss of bat- !&Iected, or Located
tery systems; gasoline engines, however, require some bat- .In approximately 77 of the 237 incidents of fires in the
tery support. All three types of engines need battery support USASC data packet, the fires were ignited by electrical
to restart after a stop. The ability to switch a battle-damaged short circuits. In the vast majority of these incidents, the
electrical circuit easily to an undamaged vehicle system short circuit had to dwell a significant time before the com-
would be an asset. Designs for redundant circuitry should be bustion was well-seated. This fact indicates that whatever
kept simple yet provide the necessaty power to a critical cir- current-interrupting device was used was either not located
cuit should one line be damaged. Wiring should be routed so to react to ~~e short circuit, was not properly sized, or did
that it is protected from damage caused by normal vehiculm not have ~ adequate response. Better circuit design or
operations and normal loading and unloadhg of equipment, selection of a more responsive device could prevent such
as well as from battle damage. If possible, electrical cables vehicular d~age.
should be routed away from hazardous fuels and combusti- In three~ of these USASC database incidents, jumper
ble fluids and sharp implements that carI cause insulation cables conkected to other vehicles were overloaded and
darnage. A conduit can provide protection, but maintenance resulted m,“ II”
~gnition of the jumper cable wire insulation.
of a wire within a conduit can be difficult. Cable troughs When a ve$cle needs a jump-start, personnel in any nearby
with easy-opening covers may be a better Solution. The wir- ve~cle will attempt to provide that jump-start, and the vehi-
ing should be retain~ in place by cable ties or clamps to cle will often draw much more current than usual. One way
eliminate wire breakage or insulation damage due to vibra- to protect tie jumper cables would be to build in a circuit
tion. The wiring should not be stressed by the retention breaker. !
device, and adequate slack for expansion and contraction In two o’per USASC database incidents, radio antennae
must be provided. Cabling that requires constant flexing, contacted e,xtetnal power cables. Antennae could also be
should be able to withstand this abuse. provided with excess current interruption capability, i.e., an
in-line fuse located, preferably, within the vehicle. A fuse
4-5.4 LESSONS LEARNED will not catise undesirable radio “noise”.
Most of the lessons learned are from the USASC data
packet. There were 77 incidents ~om a total of 237 in which 4-5.4.3 Electric Short Melts Through Combusti-
the fires were ignited by the electrical system of the vehi- ~le Fluid or Gun Propellant Container
cles. In twelv~ of the incidents of elecrncal shorts in the
USASC database, the electrical discharge caused a melt-
4-5.4.1 Flammability of Electrical Wire Insula- through in ~afuel cell wall or a fluid line and ignited the
tion combustible fluid, in five other incidents the electrical dis-
h at least 18 of the USASC fire incidents, the only com- charge resulted in a melt-through in a main gun cartridge
bustible that, burned was the wire insulation. case and ig#ted the gun propellant. These cases occurred in
Three incidents in the SEA 13DARP database illustrate Ml, M48A3, and M60 MBTs and in M88 TRVS. In an inci-
the flammability of electrical wire insulation. In two inci- dent that ~curred in Amberg, Germany, in 1966, the elec-
dents (DANs 463 and 670)ARIAAVM551s were hit in the rnc power ~shorted in an M 109 turret ring and ignited
turret by RPGs, and in the other incident (DAN 671) “an propellant. The crew chief could not extinguish the resulting
APC Ml 13A1 was hit by an RPG; the electrical wiring har- fire with a p~rtable carbon dioxide tire extinguisher. The fire
ness was damaged and the insulation was ignited. In two of continued u~l some of the high-explosive-filled munitions
these three incidents the vehicle sustained major damage !1
due to the insulation fires; in the third incident (DAN 670) *At the present time the only truly nonflammable electric wire
the damage was minor because the vehicle commander insulation is la combination of ceramic beads strong on the wire
extinguished the fire with a handheld extinguisher. In and a metallic sheath. This type of insulation is not flexible; it
would be insialled in the same manner as stainless steel hydraulic
another incident in SEA (DAN 632) the jet from an RPG tubing.
passed into the battery box of art~AAVM551 and again **Sdfinated ,cMoro@ycarbonate and Sdfinated polyvinyl c~o-
caused the electrical wiring insulation to burn. Had the wire nde wire insulations are self-extinguishing under most conditions.

$ c
I

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MIL-HDBK-684
stowed aboard started to explode and blew the turret from jet of an RPG-2. ‘Ihe resulting flash &e severely burned all

o the vehicle. The local fire department managed to extin-

guish the fire by using a water cannon iiom behind cover.
The vehicle was a total 10ss (Ref. 55). Vehicular desigm
four crewmen. The vehicle suffered major damage (200
man-hours of repair time), but it was repairable. Form-
nately, the rest of the ammunition did not ignite. k another
should assure b electric power cables are isolated fiorn such inciden~ again involving an M551 hit by an RPG-2
fuel-containing components and stowed ammunition. (DAN 1550), the crew was not as fortunate. AU four crew-
men were killed and the vehicle was destroyed. me jet
4-5.4.4 Ehx&ic Spark Ignition of Flammable apparently hit rounds in the right front ammunition rack.
Fluids Whesse.s said that a huge fireball engulfed the vehic~e and
was followed in 3 to 5s by an internal explosion, which was
b anothernine incidents in the INASC data packet
in turn followed in another 3 to 5 s by a second internal
invoking M60 MBTsandM113seriesvehicles*,flammab-
explosion. The jet might have hit more than one cartridge
le fluidsweresprayedon electricgeneratorswhosesparks,
case, all of which are combustible.
which are normally emitted when a rotor spins past brushes,
Even vehicles that use main gun caMxtrs smaller than rhe
ignited the combustible sprays. ‘fltese fires could have been
105 mm are not immune to the explosion of cased propel-
prevented by installation of a cover over, or explosion-
lan~ as was shown in Southwest Asia in 1991. ~ M2A2*
proofing, the generator or by routing the plumbing contain-
infantry fighting vehicle @V), which mounts a 25-mm
ing combustible fluids so that any drip or spray could not
main gun, was outmatched by an @i T-72 mounting a 125-
contact the electric motor or generator. mm main gun (Ref. 57). ‘Ihe 125-mm projectile penetrated
the IFV M2A2 frontal armor and initiated the propellant
4-5.4.5 W- Iloutig and Fas@ting charge(s) of one or more 25-mm cartridges. Some of these
In a fire incident in the USASC database, the power cable cartridges deflagrated and ignited a fire that quicldy
near the bottom of the turret basket of a BFV was not fully destroyed the vehicle. ‘l%e driver was hit by large frag-
clamped down after a maintenance operation. This cable ments, and the gunner, in an open hatch, was ● ’lified off” the
protruded so that the turret basket abraded the insulation, vehicle. (Two other crew membem, tie vehicle commander
&en shorted the cable, and a fire of the wire insulation and another soldier, evacuated the vehicl% the TOW mis-

0,,
resulted- Use of nonflammable insulation would have siles were apparently not involved until after the persomel
reduced the resulting repair effo% but a better solution is to evacuated the vehicle.) As a result of the fire and expl~
install the cable where contact with other items is not proba- sions, the largest piece remaining of the vehicle “could
ble and to use a conduit or metal cover (which wou~d also probably fit into your briefcase.” (Ref. 58).
provide protection from span) to protect the cabIe so that Solid rocket motor propelknts, and to a lesser degree,
even a sIoppy maintenance openuion could not cause a solid gun propellants, and high explosives contain most of
component to contact the wire or cable. the oxidizer, as well as the fuel, needed for combustion. For
this reason, propellant or explosive fires are more likely to
46 ~oN occur given a ballistic hit than are liquid fuel fires. Solid
A description of the effect of antitank iire on tanks in rocket propellants are usually closer to a stoichiometric oxi-
North Africa (1941-1942) follows: dizer-to-fuel mixture ratio than are high explosives; there-
“A dirwx hit in the fuel [cell] was crippling, but more fore, they are more susceptible to reacting violently given a
dangerous was the shot m penetrating the main armor, set ballistic impac~ Methods for enhancing crew and vehicle
fire to the cartridges of the gun amntunition. In a few sec- survivability after solid propellant or high-explosive initia-
onds, the tank became a furnace.” (Ref. 56). tion due to ballistic impact usually are containment and/or
This effect has not changed with time. In one of the inci- rediition of the explosive effects away from critical areas.
dents in the SEA BDARP database (DAN 157), an RPG-2 lhe subsequent subparagraphs identify various munitions
jet hit the case of a stowed 9&nm cartridge in an”M48A3 types, the types of storage provisions and locations in use,
MBT. There was a flash fire followed in approximately one and the potential types of fire damage. New propellant
minute by an explosion. The dtiver was Icille&and the tank developments that reduce the possibility of a catastrophic
commander and Ioader, who were standing partially out of fire are discussed.
their hatches, were blown out of the vehicle. The vehicle
was damaged so severely that it was not worth repairing. In 4-6.1 AMMUNITION TYPES
a second incident involvinganAFUJ%AVM551 (D~ 3 10), I%e ammunition stowed in combat vehicles is either for
the charge of a single 152-mm cartridge was ignited by the onboard use or is being transported. Its stowage must be
planned to rninimhe the haard it presents, as well as to

0
,,
!,,

*Usualty the M577 command vehicles, which have an ekctric

generatorwith associatedengineand gravity-fd enginefuel sup-
ply mountedaboveand fonvardof tbe troopcompartment
*his IFV M2A2 was assigned to the armored cavatry unit
becauseCWs M3A2 were not available.

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IWL-HDBK-684
assure its availability foruse. l%e ammunition foronborird The sensitivity of these munitions to ignition or initiation
use is either for the main weapon or for a secondaxy weapon must be considered, as well as the effects the ammunition
or ancillary device. The ammunition for the main weapon could have upon the personnel and the vehicle if the ener-
usually presents the more severe hazard; both the type of getic mater$ls were ignited or initiated. With regard to sen-
propulsion and warhead must be considered. Secondary sitivity to initiation or ignition, the threat impacting the
weapons are usually small arms, but they may also be small cartridge or w is of greatest importance. The capability
mortars, semiautomatic grenade launchers, or light antitank of a shap~lcharge jet to ignite or initiate energetic materi-
weapons (LAWS). Ancillary devices include smoke grenade als can be eijualed only by a strong electrical discharge. The
launchers. The individual crewmen’s weapons are also detonation of a high-explosive shell is a close third in its
included. The ammunition being kansported must be con- capability to initiate explosives. Kinetic energy penetrators,
sidered primarily for the types of hazards presented. ~ese however, have a lesser ignition capability.
hazards are due to the contents, explosive or chemical, of The initiation and ignition agents to be considered are (1)
the transported ammunition. a shaped-charge jet, (2) the arc from an electrical short, (3)
the detonation of a small high-explosive projectile (20 mm,
4-6.1.1 Ammunition for Onboard Use 23 mm, 25 mm, 30 mm, or other calibers that would not
Ammunition for onboard use must be readily available. severely distort the vehicle structure), (4) the impact of a
Primarily the main weapon must be serviced. This main KE penetrator or a fragment horn a high-explosive shell, (5)
weapon can be a high-velocity gun, as for the Ml MBT, a spdl from vehicular components that results from a ballistic
lower velocity howitzer, as for the M109 .SPH (155 mm) penetration,(6) the impact of the slug from a shaped charge,
and the Ml 10 SPH (203 mm or 8 in.); a combination gun (7) fiagmen~s from a bursting cartridge case, and (8) heat or
and missile launcher, as for the M551 ARIAAV (152 rmp); flame from \bu&ing items within the vehicle. In general, a
or a missile launcher. There can be two primary weapons, shaped-cha.mgejeq small HE projectile, or KE penetrator
e.g., the Bradley fighting vehicles that have both a TOW must perfo~ate the case or body surrounding the energetic
launcher for antitank use and a 25-mm automatic cannon. material for it to be affected. Usually the more energy
Vehicles are designed to carry a given quantity of ammun- imparted to the energetic material, the more violent the
ition based upon specific needs; however, the ammunition reaction. In jaddition, the reaction can well increase in vio-
needs frequently change. Although the ammunition mix to lence as it ~roceeds, i.e., a combustion can increase to a
be stowed at any particular Mure time cannot be.predicted, deflagratiod, andfor a deflagration can increase to a detona-
ammunition stowage capability to handle any mix within tion. ~
current ammunition availability should be provided in the When K: S. Jones (Ref. 59) conducted tests in which
design. TNT- or Composition-B-filled aerial bombs were hit by bul-
lets, fragments, or even small, superquick fuzed, high-
explosive projectiles, only one detonated immediately in
4-6.1.2 Transported Ammunition
641 tests in which the casings were perforated, although in
Some vehicles are intended to transport bulk ammunition, two tests the high explosive detonated after it burned for 25
and on some occasions any vehicle may be required to or 50 min. ~n422 of these tests there were no chemical reac-
transport such ammunition. The ammunition can be for tions, in 13,tests fires ignited but self-extinguished, and in
onboard use in any of the combat vehicles, for use by infan- 203 tests p~ of the HE deflagrated (Two to 90% of the HE
trymen or artillery, and items such as ammunition for air- burned.). In an additional 245 tests the impacting object
craft or bulk explosives. Transported ammunition need not failed to perforate the bomb casing-214 were ricochets
be available for use within the transporting vehicle or and 31 were s~ck in the casing—and no chemical reaction
readdy available when the troops dismount. Therefore, occurred.
reduction of the hazard presented to the vehicle and its crew On the other hand, Beale, Roe, and Bailey (Ref. 60)
should be the primary stowage design goal. In fact, these reported that in all 39 tests in which aircraft missile rocket
iterns could be carried in a trader, the loss of which would motors, were hit by a bullet or small HE projectile, a fire
not have anywhere near the import of the loss of the vehicle. resulted, and in 3 tests with delay-fuzed projectiles, the pro-
pellant detonated.
4-6.1.3 Relative Ammunition Hazard Assessment Reeves and Anderson (Ref. 61) had results similar to
To assess the relative hazards presented by different types those of Jones and Beale et al. In 85 tests in which frag-
of ammunition, the means of propulsion and the types of ments or p~ojectiles impacted rocket motors, there were 12
warheads must be considered. The means of propulsion are in which de case was not perforated (no chemical reac-
rocket mo~or, gun propellant, or none, e.g., bulk explosives tions), 18 in which the case was perforated but did not
or hand-thrown grenades. Warheads are high explosive chemically ~,react,43 in which the propellant ignited and
(HE) filled, pyrophoric chemical filled, reactable chemical burned wit.$out exploding, 11 in which the propellant defla-
filled, toxic or irritant chemical filled, inert, or radioactive. grated at lehst partially, and 1 in which the propellant deto-

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MIHIDBK-684

,,,
,
O
nated (with a Russian rocket motor). In 41 tesrs in which
fragments or projectiles penetrated into warheads, there
were no chemical reactions in 21 tes~ but there was burn-
DAN 1839) or for 45 to 60 min (in three M113A1 APCs
containing cases of Claymores, small arms ammunition or
bulk C4 explosive-DANs 381, 383, and 385) before the
ing in 8 tests, deflagration in 6 trots, and detonation in 6 explosives aboard exploded. This was not the case when a
tests @ll six occumed when a delay-fuzed projectile deto- shaped-charge jet hit the main gun cartridges (as in one
nated within the warhead.). M48A3 MBT, DAN 157, and in two M551 A.RIAAV,DI%Ns
These three programs demonstrated that a ballistic pene- 310 and 1550). In al] three of these incidents, an explosion
tration into a warhead or a rocket motor does not inevitably occurred almost immediate y. In two incidents tires were
ause an explosion. The faster the penetrator is moving, the ignited within Theturrets ofM551 AR/AAVs. In one (DAN
greater the probabilhy of a violent reaction. fiat spill pre- 463), the fire burned for a considerable time without Ignit-
sents a lesser hazard than the residwd pieces of the impact- ing the combustible cartridge cases of stowed ammtmitiow,
ing projectile is assumable. the crew had evacuated the vehicle in fear that the onboard
Art estimate of the sensitivity and probable reaction to ammunition would explode. In the other case (DAN 670),
impact by the threats is provided in TabIe 4-4. The probable the vehicle commander extinguished the fire with a portable
mitigation by component conslrttction is included, ie., a fire extinguisher.
projectile body is probably made of steel and is thicker than In the incident in SWA described in par. 4-6, although the
a rocket motor casing and would therefore resist span gunner was “lifted off’ the vehicle, at least two other crew
impact better. The rocket motor is not, however, assumed to members had time to evacuate the vehicle before it was
incorporate the new, insensitive designs. Pyrophoric fillers destroyed, probably by explosion of onboard ammunition
are assumed to burn whenever the shell casing is ruptured, cooked off by internal fhel and propeUant fire (Refs. 57 and
and fires are assumed to burn long enough to ignite or ini- 58).
tiate the explosives.
Fires in combat vehicles do not necessarily cause an 4-6.2 STOWAGE LOCATION AND DESIGN
immediate explosion of onboard ammunition; US Army The most dangerous item stowed within a combat vehicle
policy assumes that after being engulfed in flame for five is the ammunition for the main weapon. Thereforq the
minutes, high-explosive-filled projectiles are liable COdeto- stowage of this ammunition receives the highest priority in

0 nate (Ref. 55).

In four incidents in SEA a shaped-charge jet initiated a
fire in fuel or some combustible other than gun propellan~
design consideration. At the same time, the ammunition
must be readily available for loading into tie weapon.
Design of these ammunition magazines requires consid-
aad the fires burned for 10 to 15 min (in an M48A3 MBT— eration of the threats, tactical usage of the vehicle, and

TABLE 4-4. ESTIMATES OF SEN SITIWIY OF EXPLOSIVE-FILLED OBJECTS AND

PROBABLE REACTION ~ POTENTIAL THREA~
EXPLOSIVE- sHAPED- ELECTRIC HE ICE SPALL SLUG HEAT OR
FILLED CHARGE JET ARC* DETO- IMPACT IMPACT’ IMPACTt FLAMMA-
COMPONENT NATION BILITY
Sens.** Prob. Sens. Prob. Sens. Prob. Sens. Prob. Sens. Prob. Seas. Prob. Sens. Prob.
&c.*** RW. Reac. Reac. Reac. Reac. I&w.
Rocket motor H LO-HO H LO I-I LO-HO H L()-C L ~NR.LO M LO-C H c
cased gun propellant H~LO H C-LO H LO-C M C-LO I LV[ C-NR L LO-C H C-LO
Caseless gun H LO H c H c M LO-NR L c-m H c H c
propellant
Bagged gun H LO-C H c H c M c-m L c-m H c H c
propellant
High-explosive filkrs II ~ HO-C H C-HO M C-HO M HO-NR L c-m L[C H IC-HO
Pyqhoric fillers 1+ c H c H c H c L c L(C H c
Other energetic fillers H c H c H c ~M c-m N c-m L~C H c
Bulk explosives H HO H C-HO H H.O-NR~ M NR-HO L NR-HO M INR-C H C-HO

,,
0,“
),
*Meh-rhoug.hof case is assumed.
mwti~~
***-~e
(~.> H = high, M = ItEdilllll,L= ]OW,~ = d
R~tion ~~. ReacJ: Ho= high order (or detonation),LO= low order (or deflagration),C = combustion,NR = no -on
fThe stug nsuallydeviatesfirm thejet trajectoryafter passingthtuughthe armor.
~~kmnws a steel-casedcaruidga a brass-casedcamidge wouldbe M.

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MIL-HDBK+684
ammunition response to b~listic effects. Two trends are 4-6.2.1 Sfowage Locations
obvious from any analysis of threat weapons? i.e., increas- Data obtained from a different conflict and with different
ing penemation capability and increasing, accuracy. Over weapons (Ref. 62) verify that the impact scenarios shown
tirrie, the penetration capability of weapon systems will be on Figs. 4-3 ~d 4-4 are also applicable to impacts on MBTs
improved to overcome improved vehicular y-mor. What @e in the defe~ that were experienced from higher velocity,
vehicle designer must recognize is that in the”fielded life of direct-tire ~.capons and from wire-guided, rocket-propelled
any vehicle, there will come a time when widely available missiles, sh~.wnon Fig. 4-26. These tanks were generally in
threat munitions will be able to defeat .We vehicle armor. fixed defenswe positions; most of them were probably in
Consequently, the design cannot rely solely upon the vehi- hull defilade, i.e., the lower portion of the hull was protected
cle armor for protection of internally stowed munitions. The by. earth fr~m direct antitank fire. Therefore, these tanks
other long-term trend is improved weapon accuracy. This received most of the hits above the deck. In addition, the
trend is the result of higher projectile velocities and tanks were generally stationary. Tanks in the attack had hits
improved projectile design with consequent flatter trajecto- disrnbuted dll over, as shown on Fig. 4-27. Figs. 4-26 and 4-
ries, improved targeting, and improved terminal guidance. 27 indicate that even with weapons that have more in-flight
The logical product of this trend is greater tit probability on sta~ility, flatter trajectories, and improved fire control sys-
a target vehicle. tems, the impact still is probably going to be anywhere on
the expos~ portion of the target. Thus, improved accuracy
,

(A) Front’ 10 Hits, High-VelocityGun (B) Lefl Side ~18 Hits, High-VelocityGun
4 Hifs, Rocket-PropelledMissile ; 5 Hits, Rocket-PropelledMissile

II
(C) Reac 5 Hits, High-VelocityGun (D) Rightsip: 9 Hits, High-VelocityGun
O Hits, Rocket-Propelled!vlissile I 5 Hits, Rocket-PropelledMissile

i
@ High-Vekxity Gun
~ Rocket-PropeUedMissile

Figure 4-26. Hit Pattern, IWBTim,Defense, Direct-Firq High-~elocity Gun ad Rocket-propelled Mis-
,.
sile (Ref. 62)

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MIL-+tDBK-684

o
●

(A) Front 55 Hits (B) Left side 30 Hits

(C] l?ean 8 ~ik (D) Right Side: 51 Hits

0 Tank (ittm
Vvim-mhd ?&sties
Antitank(Ms
AntitankI%c&ets

I@re 4-27. Hit Pattern, From T- Antitank Gunq and WmGuid~ Rocket-Fropelkd NIksiles
Upon MBTs Usually in the Attack (k&62)

usually means the weapon will be fired at a greater disrance hit disrnbution toward higher locations on tbe vehicle.
and tie impact pattern wilJ probably remain the same. Also Some stowage conch.sions can be drown from consider-
onbtwd terminal guidance means that the missile will be ation of threat accuracy and penetration, namely, that items
directed toward a set source of emissions (heat or infrared located low and to the rear of the vehicle are somewhat less
or rebounding radio or laser radiation) and may not have the Wely to be hit.
net effect of having the missile impact upon a selected weak Guidance given in World War II was to locate the main
point. On t&e other hand, tdevision-guided missiles have gun ammunition below the turret ring. Other guidance was
the potential to be guided to a selected point. to protect the cartridges from the impact of span and I%om
Direct-fire threats will probably hit the vehicle on tbe the f@ments and flash of exploding adjacent cartridge
fkont m either side. The top of the vehicle will be the target cases (Ref. 63).
of indirect or aerial threats and of some guided threats. l%e Extermll stowage of some munitions is also worthy of
bottom of the vehicle, particulady the front one-thir& will consideration. ‘he obvious disadvantages of exterior
be subjected to mine threats, e.g., blas~ explosively formed ammunition stowage are the uttavailabiIity of the ammuni-
projectiles, and shaped charges. l%e least likely part of the tion during an engagement and the need for adequate hull
veticIe to be hit will be its rear. The other major factor strength to preclude vehicle damage if the ammunition is bit
affecting threat weapon hits upon a vehicle is defilade. Defi- and explodes. Exmrnal stowage does provide more ammu-
lade is sufficiently important that it is sought or created for nition-carrying capacity, and creative design can make the
vehicles, both attacking and defending. Its effect is to skew ammunition part of the vehicle protection.

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NU-HDBK-684

Stowage of ammunition within mobility fuel cells, as was tion could $e incorporated in the tank design. The “better
done in the Russian T62 MBT, as shown on Fig. 4-28, may modification” was to remove the ammunition from the
not be a good practice. The probable concept was to have sponsons, place the stowage racks low in the vehicle, and
the diesel fuel quench the combustion of the solid gun pro- incorporate ~vvaterjackets into the stowage racks (Refs. 64
pellant, but indications are that instead the solid gun propel- ~d 65). For the 75-mm ‘Wn on the M4A3 medium tank, 10
lant exploded and atomized the diesel fuel, which then storage bom!s were emplaced in the hull floor containing 10
burned violently. Some data from Near Eastern conflicts 75-mm rou~ds each and required a total of 37.1 gal of water.
indicate that T62 MBTs have had a very high incidence of The four 75!rrqn rounds in the ready rack on the turret floor
destruction from fire and explosion (Ref. 62), ‘whereas most were protected with one gallon of water. For the 76-mm gun
US-designed M13Tswere lost toeither fire or explosion, not on the M4AI, A2, and A3, a rack for 30 rounds was on one
to both, unless the fire went unchecked so that the explo- side of the driveshaft, and a rack for 35 on the other side on
sives later cooked off. the hull floor. A total of 34.5 gal of water was used. A ready
Armored personnel caniers or cargo carriers often must rack on the Ifrmet floor held six rounds and used 2.1 gaI of
transport munitions or other energetic materials, and either water. This rater contained some ethylene glycol to reduce
strong, vented magazines or munition trailers should be its freeze point and a proprietary compound, Ammu-
used. Such trailers should protect the ammunition from damp@*, to!inhibit corrosion (Ref. 66). These water racks
II .
small arms fire and shell fragments. delayed the,. Ignition of the propellant charges and also
reduced thel intensity of the fires. The ignition delay, how-
4-6.2.2 Ammunition Stowage Designs ever, was p~obably not long enough to allow the crew to
escape from the vehicle, and the intensity of the fire, even
4-6.2.2.1 Eakly Designs
though reduced, was still sufficient to cause serious darnage
In World War II the M4 Sherman medium tank had to the vehicie and injury to its crew (Ref. 63).
gained an unenviable reputation for burning when hit by In the 19~Osa series of tests showed that armor-piercing
antitank fire. In fact, it was called the “Ronson lighter”, cartridges could be protected by covering each cartridge
because it could be guaranteed to light the first time (Ref. with a 6.35~rnin (0.25-in.) thick mild steel cover. Basically,
64). Also apparently 95% of irreparable tanks were due to the cartridges were being protected from span and fratri-
ignition of the main gun cartridge propellant (Ref. 63).* To cide, i.e., sympathetic detonation, by use of individual car-
reduce this probability of igniting, additional outside armor tridge armor. This method effectively reduced the incidence
was scabbed onto the tank at the iummmition stowage loca- of fire due to span impact, but the armor racks tended to
tions. This solution was tempormy until a better mo&,fica- break up aqd form dangerous flying fragments when car-
tridges were jrnpacted by residual penetrators (Ref. 63).
Another series of tests conducted during World War II
demonstrated that munition boxes that were strong
enough to withstand the explosion of the cartridges within
them and @at were vented overboard would effectively pro-
tect the ve~cle from fire. These boxes were made of 6.35-
rnm (0.25-ip.) thick steel and could withstand the explosion
of the pro~ellant of 16 75-mm armor-piercing M72 car-
rndges (Ref. 63).

4-6.2.2.2 1’Ammunition Magazines for the Ml and

~1
MIA1 ~Ts
Conflic~in Southeast Asia, Palestine, India, and Afghan-
istan demonstrated that high-explosive sheIls stowed in
armored vehicles are extremely hazardous, especially given
a shaped-charge impact. Magazines could be designed to
Figure 4-2S. Ammunition Stowed i5 Recesses in contain the ‘detonation of one warhead, but not 40 warheads.
Fuel CeUofT.-62 lM13T A program was initiated at the US Army Ballistics Research
Laboratory to establish the causative phenomenology for

*Whenthe explosionoccurredis not available.Mostof theseexplo- *Use of the, registered name does not constitute Government
sions probably occurred after the ammunition cooked off, as approvalof $E product.
opposedto being directlyinitiatedby the threats. ,.

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MIL+DBK-684

fratricide of warheads and to devise preventive techniques impact. For example, if a HEAT warhead is hit by a shaped-

o for use in the Ml MBT, which uses 105-mm ammunition

(Ref. 67). This study established that it is necessary to per-
forate the case of a warhead to get a quick, violent reaction
charge jet at Point A and the jet trajectory is as inditmed on
Fig. 4-30, the ~T warhead itself would launch a jet that
could achieve close to design penetration in the magazine
and that the scaled impulse density is tbe most pertinent wall. (This information indicates that the designer would be
parameter for fratricide. For the impact of single figments, well advised to have these cartridges pointing overboard in
the most pertinent parameter is the areal or specific impulse tbe magazine.) If the warhead is hit at another location
to target casing thickness ratio. (where peripheral initiation* is not achieved), such as Loca-
A protective tedmique devised was to p~acea low shock tions B through F on Fig. 4-30, however, the penetration
impedance material between warheads to reduce the rate of drops dramatically. Such infomtation is needed to design
defomnation of a warhead impacted by fragments. A polyvi- onboard magazines. Penetration is not as important to mag-
nyl chloride bar, 5 x 5 x 40 cm, was found to be sui%cient to azine design as are the loadings due to explosion of the war-
prevent fratricide of 105-mm HEAT M456 projeailes, This heads. These explosions must be minimized, primarily by
technique was incorporated into the two magazines of the preventing fratricide.
Ml MBT shown on Fig. 4-29(A). Tbe ready rack, which is a llte three devices used to preclude ihricide of warheads
basket located on tbe floor below the breech of the weapon, are buffers, deflectors, and spoilers, Fig. 4-31. ‘ilse buffer is
is protected by location only. There are no restricdons on a solid shield heated between the donor, “the warhead initi-
the type of camidge that can be placed in the three-round ated by the ballistic impac~ and the acceptor, an adjacent
ready rack. warhead. This buffer captures or deflects tigments and
Further work performed at BRL provided nonbamrdous bkis~ Tbe buffer itself may impact the acceptor, but this
ammunition magazines for tbe M IAl MBT, which uses type of impac4 which is slower and more massive, is not the
120-mm ammunition, and is applicable to other armored type of impact that results i.n acceptor warhead detonation.
vehicles (Ref. 68). Ammunition compartments obtain wl- A deflector is a shield that is at an angle to the more danger-
nerability reduction through improved engineering in the ous figments and defiecrs these figments and their accom-
stowage of ammunition. The basic principles used follow:

0:. 1. Remove the ammunition from the crew compart-

ment by using a separate ammunition compartment.
2. Prevent fratricide of the ammunition by reducing or
panying blast tier than stopping them. The spoiler, on the
other hand, affects only those fragments and blast that
would actually impact the acceptor. Tbe spoiler employs a
combination of geometry and material to trap or deflect tbe
eliminating sympathetic reactions of warheads and propel- fragments. Of tbe three devices, the spoiler is the most
lant charges.
effective, particularly on a weight basis. All three &vices
3. Provide vents to preclude pressure buildup and to
provide good protection, even with sensitive explosive ilil-
vent noxious gases to tbe outside of the vehicle.
ers in the acceptor warheads. Some of the more rezently
4. Provide armor to reduce the severity of tlte impact
developed insensitive expl~sives could withstand fragment
upon the explosives and thereby reduce the violence of their
impacts and blast loading with much Iigbter devices or even
reactions.
with no devices.
5. Protect the ammunition fiorn span and thetwby
Spoilers are used in the MIA1 MBT bustle and hull mag-
reduce the number of reacting items.
azines, which are shown on Fig. 4-29(B). This andfratricide
me vehicle stmcrure must be strong enough to withstand
device and the vents and sliding doors have been proven in
internal as well as external explosions. In many current
tests to protect occupants of the vehicle from the detonation
vehicles the armor forms an exoskeleton with primary con-
of a HEAT warhead. This 120-mm HEAT warhead contains
sideration given to being mcmg enough to carry vehicular
approximately twice the quantity of high expiosive as the
loads and secondary consideration given to withstanding
105-mm HEAT warhead of the Ml MBT. Tbe MIA1 has, in
external blast loa& but litde consideration is given to inter-
addition to the magazines shown on Fig. 4-29(B), a ready
nal blast loads. In attempting to reduce vehicular weight and
rack for two additional rounds kxated on tbe floor of the
production labor, manufacturers often use “ballistic welds”,
turret basket below the breech of the weapon. Guidance
i.e., partial or shallow welds, which can c.amy vehicular
loads and prevent direct bullet penetration, but which fail to liom the M 1 Project Office is that no HEAT cartridges are
camy blast loads, particularly imernal blast loads. Vehicles to be placed in that rack-only KE ammunition should be
must be designed to cany gross overloads (particularly of placed therein.
internal blast loads), which may be alleviated by venting.
The blast loads fkom stowed rsnrrnunition must be mmil- %Shaped-chargewarheadscan be initiated around the outer edge
tather than in the centerof the end of the charge.7his tecbrsiqueis
able to the designer to analyze stress properly on an ammtt- calledptxipheralinitiationand is usually achievedby use of wave
nition magazine. In addition, the designer must know tbe shapers,i.e., inert inserts, in the explosive. h Wows desigaers to
probable warhead and propellant load reactions to ballistic usc shcnterchargesthan those requiredfor base initiatio~

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MIL-EIDBK-684
;“
.
AmmunitionStowage,55 Rounds

[A\
,.., Ml
... . MB?Wb105-mm
...- . .. . . ..- Gun -A!G~~Fe’40R0unds
●

120-mmWeapon

-.
.Lilh

(B)
,,
Figure ‘4-29. Ammunition Stowage in MNand MIA1 MBTs
(,

4-6.2.2.3 Advanced Survivability Test Bed dation of operational effectiveness and were to provi~e
Ammunition Stowage armor prot~tion against a 30-mm ICE*round (Ref. 7 1).
The AST/3 ‘TOW missile stowage system, Fig. 4-32(A),
A thorough reevaluation of one veticqlar design to
accommodated seven TOWS: two in the launcher, three in
increase. survivabili~ was made with the’ ASTB veticle.
external stc$vage, and two (either TOWS or Dragons) under
This vehicle was designed by a special task force (Ref. 69).
the crew compartment deck. Access to the externally stowed
The design of the ammunition stowage system was domi-
missiles W* through w outwardly opening door at the top
nant since the ammunition was the most hazardous material
of the compartment. To reload the TOW launcher, the loader
stowed aboard the vehicle. The ASTB was a crew-protec-
would stand in the cargo hatch, reach over the 25-mm stow-
tive version of the BFV. The ASTB was to meet all the BFV
age compaktrnent, remove the top TOW assembly, and
performance requirements except those for air transportabil-
ity and swimming. Four ASTBS, 2 infantry and 2 cavalry
*Thethreat presentedby the Russian30-mm2A42 gun (Ref. 70),
versions, were built by August 1987 and were submitted for mounted on the BMP-2 and BMD-M-1981, fires either API or
bo+ operational and live-tie tests. The ASTB gross vehicle Frag-HE with a muzzle velocity of 1000 mk at a cyclic rate of
weight was limited to 26,760 kg (59,000 lbs): The ASTB either 200 to 300 rdhnin or 500 rdhnin selectable.The effective
was to stow seven TOW missiles; the infantry version could rangeis 1000m, andthe maximumpenetrationis 55 mm (of RHA)
at 500 m. It ;Sbelievedthat the same gun is used on the Zenitnym
have five TOWS and two Dragons. The cavalry version was Samokhodnaia Ustanovka-antiaircraft self-propelted mount—
to stow 1500 rounds of 25-mm ammunition’ (The infantry ZSU-3@2—30-rnrndual gun, which uses high-explosive tracer
version carried a total of 891 rounds, 300 ready and 591 (HE-T), HE~, and APIT, and probably APHEI cartridges (Ref.
stowed.), and both versions were to have a minimal degra- 17).Thus any of these projectilescould be encountered.

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IV!IL-HDBK-684
insert the TOW assembly into the launcher, which could be fratricide, and an antifrarncide material package was
swung” rearward for easier access. The next TOW in the e~placed between adjacent missiles. An energy-damping
exterior stowage compartment would be cranked up to the “crush” package was placed between the missile compart-
upper position ready to be loaded next (Ref. 72). The TOWS ment and tde 25-mm ammunition compartment. Within the
stowed within the vehicle were located below the decking 25-mm ammunition compartment fratricide was precluded
within the bilge. The on]y protection afforded these two by antifra~de design techniques, such as rounds being
missile assemblies, other than the vehicle’ skin, was their located in ~ys with an antifratricide device between adja-
location. The TOW launcher was spaced far enough from cent rounds} which were all pointed in a single dwection (as
the side of the turret that if the TOWS within the launcher opposed to being tip to toe).
were initiated by a shaped-charge. hit, the vehicle would not The 25-mm ammunition stowage provided 300 rounds in
suffer catastrophic damage. The stowed missiles in the a ready rack immediately below the weapon, 358 rounds in
external compartment were staggered so that the warheads a left compartment, and sometimes more as shown on Fig.
alternated facing forward or aft to reduce the potential for 4-32(B). The unique design feature was that the left com-

2TOWor J ;
2 Dragons :

(A) TOW and Dragon Stowage

.,. .

308 Rounds
M3 Only

(B) 25-mI Cartridge Stowa~e

—.
Figure 4-32. Ammmition Stowage for the AST’B (Ref. 71)
I
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partmmt acted as a buffer between the external TOW stow- a gelling agent like napalm to maintain a liquid jet. These
age compartment and tie crew compartment. Thus the k flamethrowers wem usually used against field fortifications
O
!,, ;

hazardous 25-mm caraidges were used to protect the crew

and vehicle horn the more hazardous TOW missiles. This
whose main defense was smalJ arms fire, against which the
vehicle armor was adequate protection. Wkh the advent of
function was successfully demonstrated in tests. rhe %nzerfaus~ however, these mechanized flamethrowers
became mom vulnerable.
4-6.224 Armored Mobile Flamethrowers The Russians have a flamethrower version of the T-55
Flame is an excellent weapon. It is highly effective for MBT (Ref. 75) designated the TO-55. The flamethrower,
killing or disabling persomel even in areas protected fi-om ATO-200, fhs a burst of 35 L to a maximum range of 200
direct and indirect fire of KE or HE weapons. Flame also m. A total of 460 L of fiel is camied (Ref. 17). The Russiaa
flamethrower consists of one or more fiel storage cells con-
has a profound psychological effect on enemy troops. In
World War II the IX and Britain mounted flamethrowers in nected to a cylinder-piston assembly, which in turn is con-
nected to a nozzle with igniter, using appropriate plumbing.
M3 and M4 medium tanks (Ref. 66). The US had two types
Prior to use, the fiel is ported into one side of the cylinder,
of flamethrowers: one had the nozzle fitted into the location
and a small quantity of fuel is injected into the cylinder on
of the bow machine gun, and the other had the nozzie fitted
the other si& of the piston. To use, the small quantity of fuel
into the 75-mm main gun. The US and British flamethrow-
is ignited and forces the piston to eject the large quantity of
ers usually consisted of a fuel storage bottle, a high-pressure
fuel through the nozzle. This fuel is ignited as it leaves the
gas bottle, a pressure regulator, a nozzle with igniter, and
nozzle (Ref. 74). The flamethrower is also reported to be
associated plumbing. Prior to use, the fiel storage bottle
used in the T62 MBT.
was pressurized to a preset pressure. To use, the nozzle was
In Korea flamethrowas wae mounted in M26 tanks. In
directed toward the targe~ and a valve in the nozzle assem-
Merriam flamethrowers were mounted in APCs by the US
bly was opened. The igniter, located at the outlet of the noz-
Army and on M48 MBTs by the Marines. The four 19(LL
zle, could be started either before the valve was opened so
(50-gal) pressurized fiel stomge bottles, used for the US
that the fuel stream was initially burning or after a desired
Main Atmament Mechanized Flamethrower M1O-8 (Ref.
quantity of fuel had reached the target. Experience has
76), are the singly most vulnerable item, especially to a
shown that a burning jet of gelled gasoline has a s~ghtiy

o longer range than a jet that is not burning. On the other

han~ more gelled gasoline can be placed on 3 target if some
is not burned enroute.
shaped<harge threaL A shaped-charge jet could not only
puncture the bottle but would also provide a means to spray
the fuel and ignite it. b the self-propelled flamethrower
M132, a version of the Ml 13 APC, these large vulnerable
The British used a trailer towed by their Churchill VII componems were stowed witbjn the vehicle and almost
medium tank to provide fuei for their Crocodile filled the cargo space. In addition, the single 19-L (5-gal)
flamethrower (Ref. 66). The Germans had a flamethrower igniter gasoline can, located immediately in front of the
that could be used in an armored vehicle or a traiier and flamethrower operator, added to the hazard. An RPG attack
used a gasoline, engine-driven cent.rdbgal pump to pressur- on such a vehicle would probably have resulted in cata-
ize the fuel. TIE Germans also had tank flamethrowers with strophic fires. ‘Rtese vehicuku flamethrower used fiel bot-
either externally or interndl y mounted fuel cells, at least tles that were pressurized to 1.40 to 2.1 MPa (200 to 300
one of which pressurized tie fuel with nirrogen (Ref. 73). psi) to force the gelled gasoLine through the flamethrower
This fluid pumping system would present a much smaller nozzle.
vulnerable area than the pressurized bottle systems used by In the mid-1960s the Lhnited Warfare Laborato~ flmded
the US Army. Also, conceding the fuel ceils and disguising a program to demonstrate that the turbine-driven fuel pump,
the projector reduces the probability the enemy will realize illustrated by Fig. 4-33, for the Ramjet RJ43 engine of the
that the vehicle is a flamethrower. Bomarc Missile (Ref. 77) could successfidly power a mech-
During World War IL the Russians equipped some T-34 anized flamethrower. This dernonsuation was accomplished
tanks with flamethrowers. This Ognemetnyy tank (OT)-34 successfidly, as shown on Fig. 4-34. The centrifugal pump
(flamethrower tank) was fitted with an Avtomaticheskiy did not shear the napalm-thickened gasoline to an ungelled
Tankovyy Ognemet (ATO)-42 (automatic tank flame- state. Such a system could be powered by a low-temperature
thmwm) with the nozzle replacing the bow machine gun. gas generator in order to provide a detachable mechanized
The 200-L fuel cell in the fighting compamrtent used some flamethrower to be mounted on a standard vehicle for spe-
of the space normally allocated for the main gun ammurti- cial use. The fuel cell and gas-generator-turbopump systems
ticm. Some OT-34S had additional flamethrower fuel cells could be mounted on a trailer, and the nozzle-ignition-con-
mounted externally (Ref. 74). trol system could be attached to the vehicle. This setup
The fiel used in these mechanized flamethrowers was a would ~vide a much less hazardous mechanized
munition. The usual he! was gasoline that had been modi- flamethrower for special use than one using pressurized bot-
fied eilher by the addition of lubricating oil or diesel fuel or tles.

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,.

IWL-HDBK-684

4-6.3.1 Insensitive Munitions: Background and

Requirements
One of the reactions of the US Navy to the disastrous fire 9
on the USS\Forrestal in 1967 was to conduct a program to
develop m@ions that would not contribute to the effects
of an accidental fire. That effort was the first to attempt to
render or~!ance relatively insensitive to pool fires but has
since progressed to many other phenomena. MIL-STD-
2105 (Ref. 78) provides test criteria for a fast cook-off, such
as ffom a hydrocarbon fuel pool fire, multiple impacts of
12.7-mm bullets, an impact by a 16.2-g (250-grain) frag-
ment at 253’0@s (8300 fls), the sympathetic reaction to the
detonation of a similar warhead, an impact by a shaped-
charge jet, &d impact by span from a 25.4-mm (1-in.) thick
Courtesyof The MarquardtCompany. RI-IAplate hit by a shaped-charge jet, as well as for environ-
mental and~shipping extremes. The munition is to have no
Figure 4-33. ‘hrbime-lhiven Fuel-p for the reaction mire violent than combustion of the explosive fill-
Ramjet RJ43 Engine er(s) from {~y of these loadings. These IM requirements
have also b$en adopted by the Army and Air Force.

+6.3.2 ~iquid Gun Propellants

Liquid gun propellants (LGPs) were first explored
because of @eir potential weight, volume, and cost savings
for artillery; For large caliber guns LGPs offer the potential
to reduce the vulnerability that results from the extreme sen-
sitivity of solid propellant to ballistic impacts. In general,
LGP ammunition is separate loading; therefore, the propel-
lant can be stored compactly in one, two, or more locations
rather than be attached to each projectile. These fewer com-
pact locations, can be better protected than the much larger
Courtesyof The MarquardtCompany: magazines needed by solid propellant cartridges. Also the
l?igme 4-34. ‘h-uck-Mounted Flamethrower particular LGP currently being developed by the Army,
Powered by the ‘Turbine-Iltiven Fuel -p’ LGP 1846, is much ‘less sensitive to ballistic impact than a
typical soli~ gun propellant M30 if the LGP 1846 is prop-
The use of a pump system rather than pressurized bottles erly contairied (Ref. 79), i.e., within a container that has at
is recommended for inclusion in the design’of flamethrower least one dihension smaller than the critical dimension nec-
vehicles. Mounting the fuel cells on a trailer rather thz!non ess@ to piopagate a detonation wave. LGP has no voids
the combat vehicle is also recommended. and is more dense as packed than solid propellant (which
contains p~sages in each grain plus voids between grains);
4-6.3 NEW DEVELOPMENTS hence it c+ be stowed in a smaller volume. LGP requires
New developments are mainly in the field of insensitive the use of ~umps, lines, valves, and a storage bottle, which
munitions (IM). These munitions will not explode given solid propellant does not need, but the solid propellant is in
accidental or combat loadings or at least will withstand a case or bags, which are stowed in a magazine with divert-
these loadlngs for longer periods before exploding. This ers, shields; and other antitiatricide devices.
subparagraph’ presents the background and requirements for LGP 1846 is unaffected by tlie compression of vapors,
insensitive munitions and then covers some specific types of does not react violently when stored in a container that has
munitions that meet or approach tl?ese requirements. at least one dimension smaller than an established critical
These new developments are promising but are not yet dimension ‘1,‘hnd is resistant to reactions given hydraulic ram
developed sufficiently to be used in combat, vehicles; The (Ref. 79). It has demonstrated a desirable lack of response
designer must be alert to the stage of development of these to shaped-~harge jet impact tests and the span test of MIL-
items so that developed IMs can be used when available. STD-2105.$ (Ref. 80).
4

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4-6.3.3 Insensitive E&b Explosives on low-vulneraldity ammunition (LOVA) propellants for

o The sensitivity of plastic-bonded explosives (PBXS) has

proved to be less than that of trinitrotoIuene (TNT) based
explosives. This difference is attributable to the use of poly-
gun propulsion.
The Navy has successfully reduced the violence of the
response by rocket motors to pool fires (fast cook-off) by
meric binders that result in nearly voidless, pliang rubbery building in means for actively reducing case confinement
materials with fewer discontinuities than granular solid pm under fast cook-off temperature conditions. This technique
pelkm~ and hence low-energy breakup characteristics and can also apply to the slow cook-off scenario. Some work
reduced tendency to form hot spots. An additional feature of has also been successful to counter bullet impact. Ail of
some composite PBXS is the separation and sealhtg of fuel these efforts, however, are design sensitive. In slto~ every
and oxidizers, which possibly simultaneously increase the rocket motor is different and will probably need a different
chemical energy output and decrease the sensitivity to technique by which to become insensitive. Pursuing a tech-
impact loadings. Some insensitive explosives are warhead nique to separate the oxidizer and the fuel seems worth-
design sensitive, i.e., the explosive passes the test criteria in while. Also some new rocket motor case concepts, i.e., strip
one warhead but not in another. llese high explosives have laminate, composites, and hybrids, are encouraging.
been classified by application. III each classification at Ieast More success has been obtained in compounding LOVA
one explosive shows promise, and these explosives are gun propellants. IM vulnerability testing of LOVA propel-
shown in Table 4-5. One major problem has been to estab- lants for the Navy 7&nm and 127-mm/54 (5-inJS4)* guns
Ikh warhead-loading techniques usable in mass production. was compIeted in FY87, but efforts to develop insensitive
71te development status of these explosives is published primers were stopped in FY88 by a major budget cut.
annually in a document similar to “The Insensitive Muni-
tions Advanced Development FY91 Development Plan” by 4-6.4 LESSONS LEARNED
the Naval Sea Systems Command (Ref. 81). l%e hazard presented by ammunition was recognized as
A BRL program to protect armored vehicles developed 3 early as 1942. Reports fbm US sources indicated that 90 to
protective tedm.ique to rednce the incidence of violent reac- 95% of all nonrepairable tanks were butned out and that

,,
0
tion given a 13aIlisticimpact on a high-explosive munition
by preventing the rapid extmsion of the =plosive through
the cracks generated in the warhead casing of the acceptor.
To prevent this rapid extrusion of the acceptor explosive, a
practically all of thxe were from ammunition fires.** The
standard practice for US combat vehicles was to store
ammunition without the protection of armored containers
(Ref. 63). The magazines of the Ml MBT, described in sttb-
thiI%pliable layer of a plymeric material was placed on rhe par. 4-6.2.2.2 were the first well-designed ammunition stor-
inside surface of the acceptor warhead. Tests were con- age concept to be incorporated into a US combat vehicle.
ducted with 105-mm Ml casings lined with 3 mm of celhl- Also the concepts for the ASTB, described in sub~ 4-
lose acetate butyrate. This Iining increased the 50% 6.2.2.3, are novel and worth considering.
threshold input velocity of fragments for reaction tim 1470 l%e lessons learned were drawn from experience in
mls (4823 ftls) to over 1740 m/s (5700 ftk). Mild burning Southeast Asi& as well as development programs in the
reactions were obrained at higher velocities, and even at United States and elsewhere.
impact velocities near 1980 m/s (6500 ftk), the warhead
reaction was not sufficiently violent to split open the casings me US Navy designationfor guns is the gun caliber.fn rhis case
5 in., i.a, the distancebetweenrilling lands, followedby the barrrd
(Ref. 68}. hmgdlin calibers,in this case 54 calibersor270 in.
*@Thisattributionmustbe consideredcautiously.A sustainedfiel
4-6S.4 Insensitive Propellants and/or PropuIAorI fire wouldcook off the ammunition.Examinationof the tank rem-
Systems namsoften wouldnot disclosewhichcombustiblewasignited firsL
the mobilityfuel or the gun propellant,and tbe personnelexamin-
The US Navy has done considerable work to make rocket ing tie vehicle probably would merely look to see whether the
motors less sensitive to pool fires; the US Army has worked vehiclewas repairable.

TABLE 4-5. IFJSEMWI’IVE HIGH EXPLOSIVES (Ref. 78)

CLASSIFICATION EXPLOSIVE
General-purpose explosive for fragmentation and blast PBXN-109
Metal accelerating explosive (shaped charge, antiakmft) PBXN-109 Type II, PBXN-106, PBX(AF)-108, PBXN-1 10,
PBXC-121, PBXW- 114, PBXC-126
IMercvater explosives PBXN-103, PBXN-105, PBXN-1 15
‘,
0 Booster explosive
Initiation train and primary explosives
PBXN-5, PBXN-6, PBXN-7
PBXN-301, DXW-1

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MIL-I-IDBK-684

4-6.4.1 Stowage of Main Weapon Ammunition explosive, which has a TNT equivalence* of 1.101, and a
The lesson learned from several incidents in Southeast propellant dharge of 5.22 kg (11.5 lb) of M30 propellant,
Asia is that ammunition is too hazardous to be stowed which has ~ TNT equivalence of 0.895, within a steel case. 9
unprotected in the crew compartment, as was done in the The 105-@ APFSDS-T M833 cartridge has an inert war-
M48 MJ3T and theM551 ARIAAV. head and a~propellant charge of 5.81 kg (12.8 lb) of M30
Propellants, particularly those in caseless or combustible- propellant, ~ ammunition load for the Ml MBT main gun
cased cartridges, can be much more prone to fratricide t&n is strictly aqtttank, and the ratio of HEAT to KE is not spec-
warheads. Solid propellants under pressure bum more rap- ified. ~
idly, and the bum rate increases almost exponentially with The bustle and rear hull magazines are designed so that if
increased pressure. In addition, the solid propellant used in one HEAT’wmhead were to detonate within either maga-
rocket motors is now primarily a high explosive. The old zine, the crew of the tank would not be affected. This pro-
solid gun propellant would bum when impacted by a tection is accomplished by precluding fratricide between
shaped-charge jet. If it were in a cartridge case, it would w~heads, by providing a blowout panel for each magazine,
rapidly. pressurize the case and ~s increase the bum rate. and by placing sliding doors between the magazine and the
This increased pressure in a magazine has a synergistic crew compsytr-nent.The bustle has two internal dividers pro-
effect on the, warheads and it increases the probability of viding, in emence, three separate compartments; therefore,
their detonating even with the use of antifratricide devices. there are three separate blow-away panels on the top of the
This situation can be remedied by venting the combustion turret, one for each “compartment”. The blow-away panel
products: A properly designed vent can prevent such maga- for the rem~hull magazine is on the bulkhead separating the
zine overpressure. Current designs provide that one or more engine and crew compartments. In case of a greater-than-
faces of the magazine will be blown open to relieve over- 11
design pressure or impulse, the bottom side of each maga-
pressure. Care should be exercised to direct such venting zine is pu@osely weaker than the sides that must remain.
overboard so it does not inhibit o~er vehicular functions. In Rupture ofl:the magazines would vent explosion products
particular, the magazine vent should not dump the combus- downw~d from the turret or into the engine compartment.
tion products into the engine air intake, because there would The pro~ell~t charges were not considered for the explo-
bean adverse effect upon vehiculu mobility. sive loading, but other programs have indicated that a
Propellant combustion can be controlled by compartmen- shaped-ch~ge jet passing through the case and propellant
talization and/or other means. No longer should entire crews will cause. a violent reaction, as shown on Fig. 2-18. The @
and their vehicles be lost, as happened in SEA with both the steel cartrtdge case will rupture and provide many large
MBT M48A3 (DAN 157) and ~e AR/fiV M551 (DAN fragments, fvhich cart impact on surrounding cases. The heat
1550) when the propellant deflagrated. Now that warhead generated tiy the combustion of the propellant can, after a
smtifratricide techniques are under development at the US period of ~nutes, cook off the propellant in intact cartridge
Army Research Laboratory (formerly the US Army Ballistic cases and, after approximately 20 rein, cook off the explo-
Research Laboratory), Aberdeen Proving Ground, MD sive of the HEAT warheads. -
(Refs. 67 and 68), the warheads should no longer present
such a potentially catastrophic hazard. *The methodused to compareexplosioneffects is to establishthe
Starting in World War II, the British placed water jackets quantity of TNT that woutd have the same explosion effect. The
around the main gun ammunition in their MBTs, but this equivalencebetweena given explosiveand TNT can be estimated
practice has been abandoned with the latest Challenger by using the ratio of the heat of explosionof the explosiveto the
MBT. At present, Fire and Safety International (FSI) is heat of explosionof TNT, e.g., the equivalenceof CompositionB,
using data fromTable 3-12, is 5.02 MJ/kg dividedby 4.56 MJ/kg,
developing a system that would inject water into threatened which equals 1.101.The TNT equivalencecan be computedusing
combtistible-cased main gun cartridges (Ref. 82). l%is either calculatedor experimentalvalues of the heats of explosion,
water injection technique is intended for use with the 120- but these vqlues usually vary. For example, for TNT when the
‘m combustible-cased ammunition. waterproducedis still gaseous,Ref. 83 gives a calculatedvalue of
The protective designs for both the M 1 MBT and the 5.40 MJ/fcg,but.anexperimentalvalueof 4.27 MJ/kg. For Compo-
sition B-3 uhder similar circumstances,the values are 5.86 and
MIA1 MBT, described in subpar. 4-6.2.2.2, were based 4.69 M.T/kg.!TheTNT equivalenceof CompositionB-3 foundby
upon the assumption that the detonation of a single HEAT using computedvaluesof the heats of explosionis 1.085,whereas
-warhead has to be contained. Note on Fig.”4-29(A) that the by using experimentalvalues it is 1,098. ‘Ilis is a variation of
stowage configuration of the 55 rounds of 105-mm ammu- M).6%from~themean. If a combinationof calculated and experi-
nition is 44 rounds in the bustle magazine, 8 rounds in the mental valut$ were used, this equivalencecould vary as much as
from 0.869 ~o 1,372, or a variation of t22.4% from the mean.
rear hull box, and 3 rounds in the ready rack, and there is no When comp~tmgthe TNT equivalencefor a given material, use
restriction on which type of ammunition can be in any of the eithercomputedvaluesof the heats of the explosionfor both mate-
three locations. The 105-mm I-IEAT-MP M456 cartridge rialsor the experimentalvaluesfor both, but do not use a combina-
warhead contains 0.971 kg (2.14 lb) of Composition B tion of these~values. @

II
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MIL-HDBK-684

The gun used on the h41Al MBT is the 120-n2m Rhein- this ready rack for KE cartridges only; HEAT cartridges
mall smooth bore. As in the Ml MBT, the ammunition should not be placed in this ready rack (Ref. 85). The ready
0 camied is entirely armor-piercing-both the APFSDS-T and rack is protected only by locatiom
the HEAT-MP rounds. The cartridge cases of the 120-mrn me high-explosive and propellant masses and power
rounk however, are combustible, except for a stub base indicate that the design of these magazines should consider
made of steel, and the propelhmts for the two types of car- the effect of propellant charge initiation, as well as explo-
tridges are different. In general, the propellants for the 120 sive warhead initiation. The blow-away panels could vent a
mm cartridges are more energetic-TNT equivalence for propellant explosion, but this fact has not been established
JA-2 is 1.029 and for DIGL-RP is 0.941 compared to M30, in tests.
which is 0.895-and there is more propellant per cartridge, Some other ammunition magtine design features have
8.128 kg (17.92 lb) of JA-2 per ICEround or 5.40 kg (11.9 been explored but not yet incorporated into the design of
lb) of DIGL-RP per = round. Further, the propellant in any MBT.
a combustible case is ignited more readily by an external E. H. Waiker (Ref. 86) suggested that the rear surface of
ignition source than that in a steel case. The high-explosive the bustle & hinged so that an explosion of even a portion
charge in tie 120-mm HEAT warhead-1.91 kg (4.2 lb) for of the contents of a magazine would eject the remaining
Composition A, T@e 3-ii greater in size and specific contents of the magazine out of the vehicie. Tlis concept
enmgy-lNT equivalence of Lllo-than that of the 105- was tested and performed excellent y.
mm HEAT warhead. Thus an MIA1 magazine is designed Dr. A. E. Fmnerty (Ref. 87) demonstrated dtat injecting a
to withstand the detonation of 2. ] 2 kg of TNT compared to fire extinguishant into a magazine could reduce the reaction
1.07 kg of TNT for an Ml magazine. The equivalent TNT of rhe propellant. He also tested the effect of having a
mass for a 12kun KE cartridge propdlant is approxi- shaped-charge jet perforate a container of fire extinguishant
mately 8.4 kg, and for the HEAT cartridge propellant it is before entering a 105-mIn cartridge case containing M30
approximately 5.1 kg. Both of these exceed the 2.12 kg of propellant (Ref. 88). In both of these programs the fire
TNT equivalent for which the magazines were designed. extinguishant reduced the violence of the reaction, i.e.,
Also the Iatera.1area presented by the 120-mm cartridge pro- aqueous extinguishants reduced the violence more than did
pellant charge is significantly ,gnmter”thanthat presented by powdered extinguishants, but neither technique eliminated
the HEAT warhead-approximately 0.160 ma for the pro- the reaction.
pellant charge compared to approximately 0.023 tn2 for tie J. F. Mescall and D. P. Macione (Ref. 89), in a program
o H&Kf warhead*-and offers a larger target area. for the Progmrn Manager, Cannon and Weapons System,
For an MIA1 where a bustle magazine can be hit so as to demonstrated that by enciding the propellant charge of
ignite the propelkmt charges, which can generate sufficient each round with a cylinder of inturnescent material, flames
heat energy to cook off the HEAT warheads in approxi- from a similarly protected, but ignited, propellant charge
mately 20 tin, the crewmen are taught to rotate the turret would not induce ignition of neighboring charges. The test
before they evacuate so that the bustle protrudes over one results indicated that jn~escent cylindgrs could be used as
side of the MBT. This procedure is followed so that the antifratricide devices within magazines of rhe MI09 SPH to
products of combustion are not vented onto the hull or into reduce ignition by combustion from an adjacent propellant
the engine air intake. T%USwhen the HEAT warheads deto- charge analogously to the antifiatricide devices used in the
nate, the explosion would demolish no more than the turreq Ml MBT for explosive warheads.
the vehicle body could be salvaged and the tank rebuilt. The tests were performed on bagged M3, M30, and M31
There are spaces for forty-two 120-mm camidges in the propellant stowed in sleeves. These propellant bags were
MIAI MBT. Fig. 4-29(B) shows the location of the bustle placed in three parallel sleeves laid in close contact on a flat
magazine, which has a divider separating it into cwo com- surface. One of the outer sleeves was unprotected, wher~
partments. Each compartment holds 17 cmtridges, and each the other was protect~ and the propellant in the inner
compartment has a blow-away panel on its upper surface. sleeve was ignited by a long fuse. In the eariy tests the
Fig. 4-29@) also shows the location of the rear hull box sleeves were made of ahunintmL steel, or fiberglass-epoxy,
magazine that contains six 12&nrn cartridges. The blow- and the ends were sealed with rubber stoppers. Two typs of
out panel for this magazine is in the bulkhead sepamdng the materials were used to protect the propellan~ an intumes-
crew compartment from the engine compartment. These cent material manufactured by 3M known as INTE&OP
magazines, i.e., the bustle and the rear hull box, can contain and a foamed material manufactured by Ethyl Corporation
either ICE or HEAT cartridges without restrictions on the known as EYPEL-Am, which were strapped onto the out-
mix or the relative locations of the two types of cartridges. side surface of the “protected” sleeve. Each test was con-
Not shown on Fig. 4-29(B) is the twwound ready rack ducted with one or the other material, not with both
located on the basket floor. Crewmen are instructed to use materials in the same test. In every test the propelbmt within
1’
o the unprotected sleeve ignited. The lNTERAIvP success-
*Basedupon measurementsmadeon an illustrationin Ref. 84 fully protected the propellant evety time it was tested and

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MIL-HDBK-684 ~

sustained so little damage ,@at it. was deemed capable of third crew member wounded by small arms, fire. This action
reuse. The EYPEL-ATMfailed to protect the propellant in its not only incapacitated the crew but also left an otherwise
first two tests, but after the addition of an overwrap of fiber- usable M48~3 sitting without a crew. The lesson learned
glass fabric, it successfully protected the propellant in sub- here is not/ to carry unnecessary chemical ammunition
sequent tests. Of the two, INTERANTM appears to be the within an ~ored vehicle. If such ammunition has to be
more satisfactory because it has the sturdiness to withstand carried, it +ould be stowed in external boxes so, if hit, it
the vibrations and impacts to which it would be subjected cannot affe$ the crew, or an overboard-ventable compart-
within a combat vehicle. (Ref. 89) ~ ment should be provided for smoke or incendiary items.
DesigneH should provide a protected box on the exterior
4-6.4.2 High-Explosive Stowage of the vehicle for such items, or these items could be
High-explosive stowage is more difficult to design than shipped in special boxes to be attached to the exterior of the
low-explosive stowage since a detonation imparts a blast vehicle. There may be a bonus for such external stowage of
wave of energy rather than an extreme] y rapid impulse of some chemical devices. When an RPG-2 hit an AR/AAV
quasi-static pressure, as does a deflagration. The blast wave M551 on the side of a sponson, the jet entered a smoke gre-
shock passes through the wall of a container, whereas quasi- nade launcl/er but did not exit (DAN 1696). Could that
static pressure builds up within a container. If a pressure smoke greqade have functioned like a reactive armor
relief device is built into the container, the quasi-static pres- packet? II
sure can be relieved, as is done by the blow-off panels of the (
separate magazines of the M 1 series MBTs. The shock wave 4,-7 MA~ERIALS SELECTION
from a detonation, however, cannot be relieved by such a Selectioni/of firesafe material products for the interior of
pressure relief device. Thus the container must be strong combat vehicles must have a high priority. A small fire
enough to withstand the shock wave. Such a container has inside an ~~closed environment can quickly and easily
been demonstrated (Ref. 90), but it is heavy. A buffering spread by means of flammable materials and create unsafe
system has also been demonstrated (Ref. 91), but the vehi- conditions and possibly necessitate evacuation from the
cle must be able to withstand the momentum imparted; See vehicle. Mi/~erials that smolder rather than burn can also
subpar. 4-8.1.2. The lesson learned is that the vehicle must produce an ]untenable environment in a slower, insidious
be designed to withstand detonation of onb@d high explo- manner. Smoldering is often harder to detect and more diffi-
sives and that this design must be started with the first vehi- cult to extinguish than flaming combustion. Currently used
cle concept. extinguisha$s, HaIon 1301 and carbon dioxide, are not
Gun-carrying vehicles, such as IvIBTs, B12Vs,and SPHS, effective ag~nst smoldering tires. Under certain conditions
usually carry @gh-explosive projectile APCS also carry smoldering fires may progress to i-lamingfires. Materials are
high explosives in the form of mines and explosive charges desired that ‘kionot ignite or bum given a flash hydrocarbon
for use by the troops. Many Ml 13A1 APCS were destroyed fuel fire or k.imilar gun propellant fire or given continued
in SEA when the onboard explosives were cooked off by con~ct witlyparticles from the shaped-charge jet.
diesel fuel fires or other fires after the vehicle was hit while Actual fires may grow very rapidly by feeding on the heat
transporting explosives. These explosives could be stowed produced arid may quickly become out of control. Further-
in a trailer, or special, vented compartments could be pro- more, toxic smoke from such fires may be highly dependent
vided. on the combustion conditions and the surrounding atmo-
sphere. Simulation of these conditions for smaller scale
4-6.4.3 Chemical Ammunition Stowage flarpmability and toxicity test procedures is difficult; there-
h Southeast Asia the Viet Cong (VC) often dug extensive fore, data from these tests must be analyzed and carefully
tunnel systems (Ref. 92). These tunnels went down to three interpreted before product selection. Perhaps newer test
stories in depth and often contained booby traps for unwary methods should be developed, e.g., one for fire resistance to
visitors. Chemical agents, such as smoke,”were often used a”short, intense flash fire or prolonged contact with heated
by US troops to incapacitate or drive out the VC. Some- copper.
times tear gas was used for the humanitarian reason that In the paragraphs that follow, flammability properties and
noncombatants were often forced into the tunnels by the pyrolysis add combustion product evolution from materials
VC. Therefore, there were tear gas grenades in the combat that =e typically used in the interiors of combat vehicles are
area. discussed. It should be emphasized that fire tests on the con-
For unknown reasons several of these chloracetophenone stituent materials of components may produce a different
solution (CS) grenades were in the turret of an M48A3 result from ~e same test on, a finished product composed of
MBT when an RPG struck (DAN 153). The shaped-charge multiple m~terials, e.g., a seat cushion made of a fabric
jet perforated two CS grenades. The crew abandoned the exterior and;a foam interior.
M48A3 so quickly that one crew member was injured dur- The ultimate selection process for materials in a critical
ing dismounting. A second crew member wfi killed and a environment such as a combat vehicle should involve an

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assessment of the potential hazards of the materials in likely would be suitable alone for evaluating the unique properties
fire scenarios. This assessment need not be delayed until of fabric and foam combinations, such as in upholstered
computerized hazard and risk analysis procedures have seats.
been developed. Such procedures can be developed by Caution must be used to assess the “ignitability” of mate-
using the data and test methods presently available. rials. This property is very dependent on the test method
For example, a material that would not ignite under certain
4-7.1 FLAIMIWAJ31U’IY flame exposure may ignite readily under a higher heat flux.
There are sew-al different flammability properties that Fro-retardant treatment causes materials to self-extinguish
in certain tests; however, in other tests these materials may
must be considered in the selection of materials for combat
vehicles: burn readily. The term “flameproof’ (presently in Methods
5900, 5906, and 5908) must not be used. “This term was
1. Ease of ignition
2. Rate of flame spread originally used to describe the treatment of textile fibers or
other organic products to make them resistant to ignition.
3. Rate of heat rekase
However, the term has been misunderstood to mean an
4. Rate of smoke evolution (including toxic gases).
absolute or uncondkional property, and therefore, the use of
All of these properties are important and must be sub
the term. flameproof, is inappropriate and misleading.”
jetted to a hazard analysis in order to define the most impor-
(Ref. 94)
tant factors for any given fire scmmrio. For example, ease of
The method currently used to assess the rate of heat
ignition is an obvious property to consider for any rnaterid
release of materials on a laboratory scale was &veloped at
likely to be the “first object to ignite”. Resistance to ignition
Ohio StAte University, ASTM E 906 (Ref. 95), and is cur-
in a laboratory tesq however, does not necessarily mean that
rently a requirement for materials used in commercial air-
the material will not ignite readily in a larger scale scenario
craft. This test method is valuable for assessing key
with an external heat flux horn other burning materials or
fhunmability parameters, i.e., the quantity and rate at which
from prolonged contact with heated particles from impact-
heat is rekased fkorn a burning material. Selection of the
ing warheads. Rate of smoke evolution is also an extremely
heat flux for imadiating the specimen must conform with an
important criterion for fire in an enclosun% however, the
analysis of the potential fire environment for the material.
rate of evolution and the composition of the smoke are
Determination of the quantity of “smoke” produced from
highly dependent on the other flammability propem.ies and any given material is listed here under “flammability”
on the particular fire environment beingconsidered because it is an important fire parameter related to the other
Rate of heat release is a significant property in determin- flammabilAy characteristics of a material. Test Method E
ing &e spread This value is important in computer fire 906 for rate of heat release can also measure the rate of
modeling calculations and may determine in large part how smoke release. Test Method E 662 (Ref. 96) is designed to
hazardous a material would be in an actual fire. Rate of heat measure the total smoke evolved from a material under a
release is dependent on the applied heat flux; therefore, constant heat flux condition. Criteria used to evaluate smoke
interpretation of the data as related to anticipated iire sce- optical density should be based on consideration of the pos-
narios is essential. sible quantity of material and the size of the compartment in
There are many laboratory test methods for evaluating which the smoke will be collected Arbitrary standards for
flammability properties of matwials. Some of the more smoke should not be used because smoke evolution is so
common standard procedures for flammabfity and smoke, dependent on tie other flammabiliV properties.
including those used by the military, are listed in Table 4-6. There are other tests for the flammabiliV properties of
Included in tie table is a brief description of the types of materials than those listed in Table 4-6. Furthermore, larger
materials tested and the flammability property measured scale flammabili~ tests are available or could be developed
The test methods listed in Table 4-6 under Fedeml Test that subject materials to the more rigorous fire conditions
Method 191A (Ref. 93) illustrate the complexity of testing a which may exist in a real-life situation. Different results are
material @ this case, cloth) for %ame resistance”, which likely when full-size products are used in larger scale flam-
includes ease of ignition aad frame spread ‘l%etests cover mability simulations. Ideally, all materials should be tested
ignitability; horizontal, vertical, and 45deg angIe burning; for tire performance properties either in a full-scale mock-
a test for field use; and a higher heat flux flammability test. up or under conditions conducive to a hazard assessment of
The procedure for horizontal burning is the least rigorous of the fire scenario under consideration. T%is testing is not
these wts; the method that uses the larger burner, i.e., the always practical, however, and small-scale tests are used.
%@ heat flux” test, is probably the most rigorous. lhe Caution must be exercised against possible misinterpreta-
applimion of the fabric and consideration of the relative tion of the results of standard laboratory-scale flammability
importance of flame resistance in that application must be tests.
considered in the selection of standard flammability test The relative flame response properties of materials typi-
protocols. None of these fabric fhmtmability test methods cally used in combal vehicle interiors are presented in Table

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TABLE 4-6. ST~ARD LABORATORY-SCALE FL AMNL4BIUTY TEST PROCEDURES

STANDARD COMMON TllTX OR MATE~S TESTED FLAMMABILITY
DESCRWITON ,, PROPERTY
ASTM D 6351UL 94 I%mrnability of rigid plastics Rigid plastics, usually Ignitability, bum time
for elec~cal housing
ASTM D 2863 oxygen index test Rigid pla~tics, also used Oxygen concentration
for fabrics, thin films required to sustain combustion
SAE J369fFMVS302 Motor vehicles interior materials Foams for seat cushions Bum rate (horizontal)
ASTM E 162 Vertical radiant panel test Rigid plastics, fabrics Flame spread (vertical)
ASTM E 136/ASTM D 1929 Setchkin ignition apparatus Ahnost ariy material Ignition temperature
Federal Test Method 191A: Methods for testing flammability
properties of flame-retardant fabrics: ,’
Method 5900 Flaine resistance of cloth, horizontal Fabric ‘ Outward flame spread
Method 5904 Flame resistance of cloth, vertical, Fabric I Flame time, char length
for field use :1
j
Method 5905.1 Flame resistance of cloth, high heat Fabric Reaction to flame
flux flame contact (burn, melt, etc.)
Method 5906 Burning rate of cloth, horizontal Fabric “ Burn rate
!
Method 5907 Flammability test for sleeping bag Fabric Burn time, char length
cloihs, tablet method :
Method 5908 Burning rate “ofcloth, 45~deg angle Fabric ~ Bum rate
ASTM E 662 Smoke density chamber All mate+ds Smoke evolution
ASTM E 906 Ohio State University rate of heat Most materials Heat and smoke evolution
l!
release
I
4-7. Included are seat materials, materials for electrical wire be evaluated carefully, preferably under simulated or actual
coverings and instrument housings, and fabfics for clothing, full-scale te$ conditions. Fire-retarded materials are gener-
sleeping bags, tents, equipment covers, tarpaulins, etc. ally more ~difticult to ignite than comparable nonfire-
Materials that melt, as illustrated in Table 4-7, present a retarded materials. Once ignited, however, fire-retarded
particular problem in evaluation of flammability test results. materials ~ill bum and may produce more noxious and
This is due to the fact that melting removes heat from the toxic products than the nonretarded base material. Fire
flame and may enable a specimen to “pass” a small-scale retardants may tie appropriate dad beneficial from a fire
controlled test procedure; however, melting in a larger scale safety point of view in many situations. These should be
he may spread the flames and add to the intensity of the fire reviewed on a case-by-case basis.
by creating a pool of liquid fuel. Thus the physical proper- Foam ma~rials, e.g., seat cushions, may bum rapidly and
ties of the material must be considered in any selection pro- should be pqotected by a fire-blocking layer or covered by a
cess based on flammability considerations. highly fire-~esistant.fabric. (See subpar. 3-6.3.) Evaluation
Materials that form a char often bum more slowly than of the fab~ and foam composites should be conducted
those that do not because the char protects its substrate from under procedures such as ASTM E 906 or full-scale simula-
the heat and flame. However, such materials, e.g., cellulosic tions. I
materials such as cotton or burlap, may propagate a smol- Clothing ~d miscellaneous debris pose a fire hazard that
dering fire by forming a self-propagating char. The applica- is dMicuh t! predict and/or to regulate because the quantity
tion of such materials determines whether or not char and types o~materials are so variable. General flammability
formation is an acceptable characteristic. considerations and knowledge of fire property data by
Selection of naturally flame-resistant materials, e.g., designers @d users of combat vehicles are valuable in
Nomex@ and Kevkir@, which are resistant to ignition developing w awareness of the potential hazards of these
because of their thermalIy stable polymer structure, should materials.
be made wherever possible and with due consideration for
the performance of these materials under large-scale test 4-7.2 PYROLYSIS AND COMBUSTION PROD-
procedures and in smoke toxicity evaluations. Also materi- UCTS
als containing fire or flame retardants (either “added” to the When a natural or synthetic polymeric material under-
polymer marnx or “reacted” into the polymer chain) must goes pyrolysis (nonoxidative thermal decomposition) or

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MIL-+IDBK-G84

TABLE 4-7. FLAMMABILITY PROPERTIES OF MATERIALS TYPICALLY USED IN

o MATERIAL
COMBAT VEHICLES
REACTION REACTION USE OF MATERIAL

Vinyl (PVC) fabric Self+xtinguish Seat covering

Polyurethane foam (flexible) Melt Bin@** Seat cushioning
Wool batting Bum Slowly seat cushioning
PVC (polyvinyl chloride) Char Self-extinguish Electrical wire insulation
Nylon Melt Bum Electrical wire insulation
Teflon@(polytetrafluoroethylene @TFE)) Melt Self-extinguish Communications cable insulation
ABS (acrylonitrile butadiene styrene) Melt Bm**x Elecrncal/electronic housing
High-impact polystyrene (HIPS) Melt Bin*** Electrical/electronic housing
Fabrics: Fabrics for clothing, sleeping bags,
tents, and equipment
Nylon Melt Burn
Cotton char Bin***
WOOI Bum
Nomex@ Melt Self+xtinguish
Kevk# Melt Bin***
Polyester Melt BW***
Burlap
Fiber@ass (polyester or epoxy resin on Melt Does not readily burn
glass fiber)

0
,’ *Ahigh—tempemmre
**~r p~~
is shown.
environmentor contactwith a hot objectis assumed.
of comp~n, the expectedreactionto flamein a ~ical kboratory fl~l@ tCStwith COIIUtlOttly
avail~le -~

***~y ~~ ~~ - fi= ~-~ e.g., Polyurethmefoam, will“self-extinguish”undersome test procedures.

combustion (iicluding oxiclative pyrolysis, or smoldering, which include the applied heat flw the availability of air to
as well as flaming), the resulting smoke probably conrains the combustion site, and flaming versus nonfh-iming com-
toxic or corrosive products. The common synthetic and nat- bustion. Thus any labomtory test protocol for evaluating the
ural materials that may typically be found in the interior of a composition of the smoke, e.g., by analytical procedures or
combm vehicle are listed in Table 4-8. All carbon-contain- smoke toxicity experimentation, must be evaluated in terms
ing materials (even simple fueIs) produce carbon dioxide, of the test conditions relevant to the actual fires possible.
an asphyxiant and have the potential to evolve Ietlud carbon ‘Ilte smoke products, however, cannot be predicted fkom a
monoxide and partially oxidized hydrocarbons, such as given set of combustion conditions without extensive
aldehydes, many of which are toxic. Also nitrogen-contain- empitical data. All smoke may be toxic and many smokes
ing materials might produce toxic gases, which include are corrosive. Tlterefore, any smoke in an enclosure is a
nitrogen oxides, hydrogen cyanide, and organic nitriles, potentially serious problem. The toxicological significance
mines attd isocyanates. Materials that contain halogens, of the gases listed in Table 4-8 is discussed in par. 5-6.
i.e., fluorine, chloM~ bromine, or iodine, may produce cor- Smoke also contains aerosols (liquids in suspension) and
rosive and toxic gases, such as phosgene (COCQ or the soot (carbonaceous sofids) in addition to the gaseous prod-
halogen acid% e.g., Ml. The possible smoke products must ucts previously described. Generally, pyrolysis-in this
be considered in the selection of materials for the interior of =e, either nonoxidative or oxidative pyrolysis, including
a combat vehicle; preferably, materials that generate nox- “smoldering’ and “non,flaming combustion’’-produces
ious products will not be wed. aerosols. Only flaming combustion produces soot. The aero-
‘he term “smoke” is used here as defined in ASTM E sols are often white or yellow in color and comprise poly-
176, Sian&zrd Tenninoiogy Refaring to Fire Standards (Ref. mer fragments, such as a.ldehydes from cellulosic materials

,,
0
94), as %e airborne solid and liquid particulate and gases
evolved when a material undergoes pyrolysis or combus-
tion.”. The composition of the smoke horn individual mate-
rials is highly dependent on the combustion conditions,
or isocyanates from polyurethane. SooL on the other han~
is composed almost exclusively of muhi.ring aromatic mole-
ctdes, essentkdly graphite or carbon, and is always a sec-
ondary combustion producq i.e., it does not arise dwtly

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TABLE 4-8. TOXIC PRODUCTS THAT MAY BE P$QD?XED FROM SELECTED

MATE W UNDERGOING PYROLYSH!OR COMBUSTION
MATERIAL (CONSTITUENT ELEMENTS) HAZ+DOUS COMBUSTION PRODUCTS
PVC (C1H+21) H~C:B!O C() :1;?
Polyurethane foam (C~,~H,,lN02,1) H~, NQX, JO, C+, NCO
wool (N, c, H, o, s) HCN, CO, CO,, N~~
Nylon (CbHllNO ) NOX, HCN, CO, C~2
Fluorocarbons, e.g., Teflon@) (F,C) HF, peffluorocarbon compounds, CO, C02
Nomex@, Kevlar@ (C,gH100zN2) NO=, HCN, CO, COZ
polyester (C5,77H,.2501.,,) NOX, CO, C02
Burlap (C, H, O) co, C02
Fiberglass (Resin Coating: C, H, Si, N, O) CO, C02, NOX, HCN, NCO
ABS (C, H, N) HCN, CO, COZ, NOX
HIPS (CgH8) co, co,
Note: Fire extinguishantscan add to the numberof hazardousproductspossible.

from the polymer structure. Some aerosols are also pro- 4-7.3 L~SSONS LEARNED
duced during incomplete flaming combustion. Thus the 4-7.3.1 B&listic Fabric Selection
composition of “smoke” from any given material under a
Three unbended ballistic fabrics were used as span cur-
given set of fire conditions is difficult to predict and com-
tains in several tests described in Refs. 22 and 23. These
prises a mixture of many products. fabrics were Kevlar@ 29, ballistic nylon, and highly ori-
Other items that can be included with “smoke” are parti-
ented polyethylene, Spectra@ 900. These span curtains were
cles of the fillers added to new composites. Items such as intended not only to trap span but also to confine fires to a
carbon or boron filaments can become airborne when the small comp~ent. In general, the Kevlar@was highly sat-
composite ,bums or is pyrolyzed and can alter chemically isfactory. E@listic nylon melted when the fire had enough
and change shape to become small airborne particles, which duration tu$ intensity to heat the nylon above its melting
camcause damage to unprotected eyes, skin, or lungs (Ref. point. The tighly oriented polyethylene ignited and burned.
97). Again, composite materials must be tested to determine In an additional effort to make the polyethylene fire-retar-
whether there are potentially hazardous co~bustion prod- dant, som~ polyethylene material was treated with an
ucts or by-products, and if there are, those composites enzyme solution that, bad made certain other fabrics more
should not be used in combat veficles. fie-resistant. This enzyme solution made the polyethylene a
Fire extinguishnts, e.g., Iialons, may produce toxic or little more difficult to ignite, but once ignited, it burned as
corrosive products, e.g., halogen acids or phosgene, upon rapidly as it had in an untreated condition.*
reaction with a fire (Ref. 98). Presently, the use of many of The less+ learned is to select fabrics that will not burn
the common extinguishing agents that have been recom- for span ctiains in combat vehicles. Kevlar@ is highly sat-
mended for enclosures is being re~sessed; toxic and corro- isfactory, fiberglass or Nomex@ should be satisfacto~,
sive effects are coming under more careful scrutiny. nylon will ~melt, and polyethylene is not recommended.
Because the pyrolysis and- combustion products gener- These recommendations are for unbended fabrics only;
ated are functions of the type of combustion, the interior bonded fabiici should be tested for fire resistance.
materials present, and the extinguishant used, a recom-
mended list of interior materials cannot be given. Instead 4-7.3.2 Hazard Potential From Use of Composites
the designer should have potential interior materials tested The crash of a Royal Air Force (RAF) Harrier on the
to establish the pyrolysis and combustion products horn the island of h$oess in Denmark, 17 October 1990, brotight
various types of combustion, mixes of other materials attention to the production of noxious particles through
present, extinguishant-s to be used, and climatic conditions. combustion’ of a carbon-filament-reinforced composite.
Then he should preferably exclude any materials or material Investigate@ were forced to wear protective. clothing,
combinations that produce noxious products. Any remain- including dust helmets, to avoid particle ingestion (Ref. 97).
ing noxious products can be removed by the extinguishing
techniques incorporated in the vehicle design and/or by *Test conductedby W. A. Mallow and P. I-LZabel at Southwest
appropriate vehicular ventilation. ResearchInstitute, 1987.
,.

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This example illustrates that reinforcements used in com-
TABLE 4-9. CHAR YIELD FOR

o posites can become small, hazardous airborne particles

upon combustion of the composites. The lesson learned is co
&termine what can be produced by the combustion of comp-
osites and to avoid the use in combat vehicles of compos-
SELECTED POL=RS

POLYMER
(Ref. 102)
CHAR YIELD, %
AT 800°C IN AN N2
ites that produce noxious particles. ENVIRONMENT
Phenolics 45
4-7.3.3 Fire-Resistant Polymers aud Po&menc Phosphorylated epoxy 1 38
composites Polyphenylsulfone 48
l%ere is a pressing need to improve substantially the fire Bismaleimide 50
resistance of po@mrs and polymeric composite structures. Phosphorylated epoxy 2 56
For thermoplastic polymers there are really two applica- Cyclophosphazene polymer 82
tions. The fi.mtis in the internal cabin fitting and fixtures.
This application may not be a ptiary concern in combat
vehicles, but it is likely to become more important as the 4=8 SYSTEM INTEGRATION
applications of polymers increase. The second application To obtain a system that prevents the occurrence or contin-
relates to the control of elecrncal fires and the critical role uation of fires, a designer must consider the threat effects
polymeric materials play in insulating tke electrical cables. and the combat vehicle response to those effects for all of
The general approach to making polymers h-resistant the systems, subsystems, and components involved. The
has been to formulate the polymers with additives that designer must also consider combustion and explosion and
inhibit oxidation of the polymer. The addition of red phos- the phenomena that affect ignition of a iire or initiation of
phorus to polyethylene reduces flammability and increases an explosion. Combat vehicles must carry fuel for their
chaning. The detailed mechanism is not known, but it is internal combustion engines and ammunition for their
plausible that phosphorus oxidizes to the large number of weapons, and they must go where the enemy will do its best
plmsphorous oxid% which have high heat capacity and to destroy those vehicles. To depend upon armor to defeat
high latent heat of fusion. all hits or countermeasures to avoid being hit in all instances
,,,
0
The use of’phosphorus-containing flame retardants is one
of the best known methods for improving the resistance of a
is poor practice. As was stated by the ASTB T3sk Force,
“Combat vehicle survivability discussions frequently
large class of polymers to combustion. This technology is center on this survivability rule:
mature, and an extensive body of literature is available, as - Don’t be detectti but if you are,
exemplified by a number of recent contributions (Refs. 99 - Don’t be acquired; but if you are,
and 100). - Don’t be hic but if you are,
Also, the use of polymeric composite structttms provides - Don’t be penetrated; but if you are,
significant weight benefits and future combat vehicles will - Don’t be killed:’ (Ref. 69). .
contain more structural composites. Fortunately, there is Since combat vehicles contain flammable mobility fuel and
reliable evidence which suggests that the fire dynamics may higldy flammable solid propellants and high explosives, a
h quite manageable from the materials point of view (Ref. “simple fix” will not be adequate to prevent Ii.res.Advantage
101). should be taken of any fire prevention potential presented
Parker et al (Ref. 102), have reported a new class of res- by the materials present.
ins, which incorporate the phosphorous-nitride ttimer to
yield polymers that will not burn even in pure oxygen. 4-8.1 COMPARTMENTALIZATION
A number of bmaleimide polymers, which incorporate Most combat vehicles are compartmentalized, at least
the phosphonitrilic trimer, generate fire-resistant po@mers into an engine compartment and a fighting or crew compart-
that have good thermooxidative stability in air at temperat- ment. ‘he crew of a combat vehicle is protected best by
ures Up to 816*C (15003. Chemical hkages, which are placing the most hazardous materials—arnrn unition and
_tible to thermal degra&tion by the methylene units in mobility fuel—in separate compartments. ‘fhe crewmen do
methylene dianaline, have been replaced by phosphonates not have to handle tie mobility fuel when operating the
and cyc~otriphosphazenes. This replacement has resulted in combat vehicle, so compartmentalizing the mobility fuel is
the development of virtually completely tie-resistant poly- a design challenge in engine and fuel cell placement.
mers with Iimiting oxygen indices of 100 and residue Ammunition stowage is different.
weights in excess of 80% h air at 871“C (1600*F). Table 4-
9, &rived from data in Ref. 102, compares the thermooxi- 4-8.1.1 hununition Magazines
dative stability of incydophospbazenes with state-of-the-an An excellent use of compartmentalization is the separa-
b~ixnides and aromatic marnx resin polymers. tion of ammunition magazines from the occupied compart-

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MIL-HDBK-684

ment of the Ml and MIA1 MBTs and the AST? as

described in subpars. 4-6.2.2.2 and 4-6.2 .2.3,, respectively.
On these vehicles there are exterior blow-away panels that
permit venting of the products of explosion to the outside.
Thus an explosion in any magazine will probably result in
the loss of the remaining cartridges in the affected magazine
only. Of all rounds carried, however, only the few in the
ready rack present a danger to crewmen. Surrounding these
ready rounds with a water jacket could reduce the explosion
effects”but not eliminate them.
Unless there is an automatic loader, ammunition must be
handled by personnel. The rounds for tank guns must be
readily available to the loader, who must physically insert
the cartridges into the breech. The main gun c@dge maga-
zines therefore must have a sealable access strong enough to
withstand the explosion of the stowed ammunition propel-
lant. These magazines should be vented to the outside to
reduce quasi-static pressure resulting from explosion of the
contents. These vents and the other components of the vehi-
cle should be located to preclude undesirable interactions,
such as those described by Watson and Gibbons in Ref. 68,
as well as the dumping of propellant products of combus-
tion into the engine air intake. Descriptions of potential
improved designs are given in subpar. 4-6.4.1.

4-8.1.2 External Ammunition Stowage

Early in the ASTB program, plans were made to stow
some of the TOW missiles externally. These TOWS were
mounted on we upper rear side surface of the crew compart-
ment. A ballistic shield was placed over the missile assemb-
lies to provide protection from 7.62-mm or smaller small
arms fire and from artillery shell fkagments. A layer of cush-
ioning material was emplaced between the inissiles and the
hull to prevent damage to the hull if the missile motors and/
or warheads were initiated by a shaped-charge jet or other
ballistic penetrator that could defeat the shield. Tests and
analyses showed that a cushioning layer consisting of
approximately 25 mm (1 in.) of an elastomeric material, 102
mm (4 in.) of aluminu~ honeycomb, and 38 mm (1.5 in.) of
steel was needed to prevent rugm+reof the hull. But even i’
with this buffering material in place, in a test the hull was permit bet?.~endsto blow out and vent the quasi-static over-
still distorted to a parallelogrammatic shape so that the rear pressure. Tlh concept was tested in a subscale model and
ramp door became jammed. A scale model test was per- has been demonstrated to be feasible in six scale model
formed in which a single missile motor and warhead were tests, but it @s not been optimized for size and weight. By
detonated under a ballistic shield but without the buffering using a scaled missile simulant of the same design and size
layers. Fig. 4-35 shows the pretest configuration and Fig. 4- as the one $at destroyed the model structure, the missile
36 the posttest condition. container s~own on Fig. 4-37, i.e., the lower one, was
A different solution was demonstrated in which the bulged, but the structure of the model was unaffected (Ref.
impulsive loading from the exploding energetic materials is 91).
diverted so that the structure on which the missile assembly I

holder is mounted will not be subjected to loading (Ref. 90). 4-8.1.3 Jacketed or Doubie-Walled Fuel Cells
This solution is to install each missile assembly within a In a sen~e, a hollow wall or jacket is a compartment,
cylindrical shield that is strong enough to contain the blast which can contain a liquid, added to another compartment.
impulse and quasi-static overpressure radially but also to The use of!!a double-walled fuel cell with extinguishant

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,’

Chrtesy of FMC Corporation

I?@me 4-37. Posttest Condition Showing
Bulged Missile Container (Ref. 91)
within the jacket provides multiple benefits. Not only may Figure 4-39. Fuel Cells From Tests No. 4 and 5
this double wall provide a threat-rekased fire extinguishant (Ref. a)
in the exact region in which ignition would occur, but also
the presence of the fire extinguishant on the outside surface
of the fuel cell wall greatly reduces hydraulic ram damage Fig. 4-38 and the lower cell in fig. 4-39 were jacketed on
to the wall and thereby reduces the amount of fuel thrown two sides with 18-gage stainless steel with water as an
into the compartment housing the fuel cell. F@ 4-38 allows extingui$uant placed between the jacket and the fiel cell.
comparison of the lower fuel cell to the upper fuel cell, and From these and other tests described in Ref. 27, the follow-
Fig. 4-39, the upper fuel cell to the lower cell. In all four ing can be established:
‘, 1. The&e extinguishant was effectively dispersed by
0 tests the shaped charges were M28A2 HEAZ warheads fkom
the 3S-in. rocice~ the diesel fuel was from the same batch
for all four tests, and the i%el cells were all the same size
the threat and extinguished combustion of the fuel- The tests
showed that water and the dry chemical lire extingu.ishms
(Ref. 24)- The fuel cells in Fig. 4-38 were made of 16-gage were highly effective in extinguishing the fires.
stainless steel, and of 12-gage winless steel in Fig. 4-39. 2. ‘Thejacket and extinguishant greatly reduced dam-
The lower fuel cell in Fig. 4-38 and the upper fiel cell in age to the fiel cell due to hydraulic ram. Both the liquid
Fig. 4-39 were welded with single walls. The upper cell in (water, water-based extinguishants, or bromochloromerh-
ane) and solid (pulverized potassium bicarbonate or granu-
lated monoatnmonium phosphate) extinguishants in the
jackets acted to reduce the hydraulic ram damage to the fuel
cetl walls.
3. The hole caused by the jet enhanced by fuel hydrau-
lic ram can be much larger for thinner skin materials than
for thicker. The weaker the cell wall, the larger the hole that
can be expected; however, the cell wall thickness or
strength can be increased to a point at which hydraulic mm
no longer has an eflec~
The double-walled fuel cell concept is very prornisiig,
but there are cumently no established design parameters for
which an optimal design can be made.

4-8.1.4 Storage Compartments and Bilge

Most combat vehicles have many small cubbyholes for
storage of incidentals. ‘RIUSwithout too much effo~ the

,,
0 Figure 4-38. Fuel Cells From Tests No. 2 and 3
compartments and the items themselves can be converted
into traps for he] spray, span, flash, and fragments of pene-
trators. ‘fbese small compartments can also trap whatever
(Ref. 24) fuel combustion may occur.

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The key design features of these small compartments are source gen//rapd by penetration impacts and providing a
simple. The compartment should be at least 152 mm (6 in.)
deep to permit fuel droplets in the wake of the jet to move
out of the path of the jet or to permit span to spread out. The
sepaxate cornpdent for innocuous combustion.
The designer should assure that the original capabilities
of the vel&cle are maintained when span curtains are
a
compartment cover should be made of a material that does installed. F$r example, the ambulance version of the M 1I 3
not emit a flm,h when impacted by a jet or KE penetr+or APC ongint~y, was capable of having four litters installed,
and should be strong enough to stop span. These compart- but after sp~l hners were incorporated, the litters could not
rnems are made to store items such as those given on Fig. 3- be installed without removal of the span liners (Ref. 103).
I“
4. Most of the items shown on Fig. 3-4 are not readily flam- Provisions should have been made so that litters could be
mable; therefore, they can be used to trap span and flash installed without removing the span liners, which protect
and, if between a fuel cell and an occupied compartihent, the wounded during evacuation.
fuel spray. Storage compartment ,,walls and doors can also
serve as span curtains. 4-8.2 S@ERGISM OF FIRE PROTECTIVE
Liquid DF-2 was dd?ficult to ignite when it had been 60MP0NENTS
sprayed onto the walls or into the bilge of a test fixture sim- The design of the fire protective components of a combat
ulating the crew or engine compartment of w armored vehi- vehicle must be such that each component aids in prevent-
cle (Ref. 22). In fact, DF-2 in the bilge did not ignite even ing fires so ~~at the sum of the contributions of two or more
with a conflagration within the fixture as long as the deck component preclude the fire, even though any one compo-
plates were in place. The DF-2 vaporized and burned within nent alone may not. A good example is two of the compo-
the fixture after the fixture had been heated above the vapor- nents descr$bed in the immediately preceding paragraph.
ization point of the fuel, but combustion did not occur The double~walled fuel cell could prevent an immediate fire
below the decking. The bilge was the space between the hull tlom a hit ~y a shaped-chage jet, but unless there is a safe
and decking, and this bilge was not airtight. There were fin- collection location for the sprayed fuel, another fire could
ger holes to facilitate decking removal, and the interstices start and ig~ite the fuel. If fiel can flow into a covered bilge,
between fixture walls and deck plates perrr@ted the ready however, a sustained fire could not exist because the major-
flow of liquid DF-2 from the interior of the test fixture to the ity of the fuel would have collected in the bilge. Some other
bilge. These tests indicate that the bilge, if covered, is a rel- synergisms ‘hredescribed in the paragraphs that follow.
atively safe collection location for combustible liquids, such II a
as diesel fuel or hydraulic fluid. Tests should be performed 4.8.2.1 I$ess Hazardous Ammunition
using IT-8 or Jet-Al to establish whether or not the lower To prevent a fire, the designer should assure that there is
flash point fuel should affect the design. insufficient lhel or oxidizer, that the oxidizer and fuel do not
II
mix in fl~able ratios, that an ignition source is not strong
4-8.1.5 $pall (hrtains enough for ignition lo occ~, or that the ignition source and
Span curtains are intended to capture small projectile flammable @ixture do not meet for sufficient time for a fire
fragments and span particles, whi,ch would injure personnel to kindle. ~f ignition cannot be prevented, the designer
or damage hardware. These curtains can also trap lyger should assu~rethrough starvation of fuel or oxidizer that the
projectile fragments after they have slowed down. Material fire will nof be sustained. If the fire becomes sustained, it
chosen for span curtains should be “nonsparkkg” and non- should OCC$in an innocuous location and not catastrophi-
flammable. The location of span curtains, i.e., their dk.tance cally affect the vehicle or its occupants. The latter solution
from the compartment walls, should be selected to capture is highly a~propnate for solid gun propellants, rocket pro-
span most effectively. This distance, estimated at a mini- pellants, or~high explosives. The fuel or the oxidizer cannot
mum of 152 mm (6 in.) from a penetrated wall, should also be exclude~ because both are already present in an intimate
provide space to store some of the impedimenta carried in mixture tha~ is imminently combustible. If a ballistic pene-
the combat vehicle. By rigidizing the span curtains, a useful tration occ~s, particularly by a shaped-charge jet, the igni-
storage compartment results, but there is reduced ballistic tion source IISpresent in sufficient strength and duration for
performance of the curtains and a lesser dampening of ignition. ~~e explosive cannot be made inert with an extin-
noise. If the storage compartment is inside the vehicle hull guishant. ‘J%erefore,the best solution is to isolate the explo-
with an energetic material container, such as a fuel cell, sive-contai~ing objects.
directly on the outside of the hull, ,1.hecompartment contents The ASTB design solution for main weapons ammunition
should be materials that are relatively inert, can act as fire storage in the ballistic boxes described in subpar. 4-6.2.2.3
extinguishants, or at least can collect droplets or particles of is an excel~t solution. The TOW missiles presented a far
the energetic material and the span or flash from the hull. gxeater hazard than the 25-mm cartridges, so the 25-mm
Thus the span curtains serve multiple purposes, which cartridges were used as buffering material between the 9
include separating the flammable mixture horn the ignition TOWS and the crew compartment. See Fig. 4-32. Any TOW

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MIL-HDBK-664

missile motor or warhead reaction could be a low-velocity, the water is not essential to the immediate combat capabili-

o high-mass push against the 25-mm cartridge box; such a

loading has a low probability of initiating reactions by the
2.5-mm cartridges. The compartment for the 25-mm car-
ties of the vehicle or crew. Water is a convenience, not a
necessity, for a short-term fight. When an external fuel cell
is traversed by a shaped-charge jet a water cuntainer
tridges was made strong enough so that if some cartridges located on dte inside of the penetrated armor can provide a
exploded, personnel in the crew compartment would not be quenching agen~ (As a bonus, in the summer the drinking
ai%cted. An explosion in the TOW compartment would water would stay cder within the vehicle than it would
destroy dl the TOW missiles therein and would probably om.side in the sun. Also, in winter the water would be less
damage many of the 25-mm cartridges in their compartment likely to freeze.) In the ASTB a 5 l-mm (2-in.) thick layer of
but wotild not seriously affect persomel within the vehicle. gelled water was so emplaced for each external fuel cell
Funher the TOW explosive-filled components and the 25- (Refs. 23 and 71). Those layers of water were unnecessarily
mm cartridges would probably behave somewhat like reac- added weight because there was a water container present
tive armor to inhibit the jet and thereby protect other com- on the vehicle elsewhere that could have been divided and
ponents and personnel that are fartheraway but in the path placed in those two locations. This water container was on
of the jet. TINS less hazardous ammunition was used to pm the outside of tie vehicIe, so it did not contribute to the
tect personne~ from more hazardous ammunition. This con- solution of a specific fire survivability problem. Due to con-
cept was verified in live-fire testing. sumption by the crew, drinking water should not be a pri-
mary lire-protective componen~ but its placement should be
4-$2.2 Water Storage considered during design. See subpar. 4-8.4.4 for incidents
The efficiency with which water prevents ignition was in Southeast Asia that demonstrated the effectiveness of
demonstrated in one of the external fuel cell tests described water in protecting against shaped-charge attacks.
in Ref. 23. Test 10 in that program demonstrated that Some combat vehicles also carry coolant water. When
although the M28A2 jet passed through an external fuel cell consi&ring coolant water, the designer should assure that if
made of 25.4 mm (1 in.) of aluminum 5083 and an internal a fkeeze point suppressant is require~ it wilI be nonflammab-
compartment containing a 5-grd can of water, there was no le; othenwise, it will bum in a fireball if hit by a shaped-
visible flash from fuel or Al 5083, but a strong flash fiwm charge jet. Care must also be taken so that the crew will not

0 the aluminum 6061 mounted on the far wall of the test was
visible. The water-filled can, shown on Fig. 4-40, was
destroyed but would have protected occupants. Every com-
be sprayed with heated coolant if the cooling system is pen-
etrated.

bat vehicle carries drinking water for the crew, and many 4-8.2S Space Heaters and Exhaust Systems
have additional coolant water for either the engine or the Combat vehicles must operate in winter, even in arctic
engine oil or for some other item. The crew’s water con- regions; therefore, space heaters are provided. Because it is
tainer is often pIaced on the outside of the vehicle because not desirable to have the engine run continuously when the
vehicle is not moving, ~pike heaters”often burn fuel to pre-
vent frostbke of crewmen, to assure proper functioning of
vehicle hardware, and to prevent fkezing of liquids within
the vehicle. l’%esespace heaters should not add significantly
to the maintenance m operational workloa& and they espe-
cially should not present a hazard. There have been many
instances of space heaters in combat vehicles exphding or
catching fire because they were turned on when the fhel
fkom a previous use had not been fully purged. See subpar.
4-3.5.5. A space heater requ$ing that degree of operator
maintenance should not be used in a combat vehicle. “User-
-friendly” equiprnen~ as computer buffs would say, is
needed.
If fuel-burning heatm are used in combat vehicles, the
burner should not be located where fuel from a perforated or
ruptured fiel ceil could spray or pour on it. This event
would provide a source of certain ignition for spilled fuel,
particularly if a shaped-charge jet or KE penetrator could

0
,’!’
Figure 440. Five-Gallon ll%tter-l?iied Can
After Test No. 10 (Ref. 23)
perforate the heater and puncture a nearby fuel cell. In addi-
tion, stowed ammunition, particularly in combustible con-
tainers, should not be located close enough for the heater to

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ignite the container and cause the stowed ammunition to egress from’a 25-m rifle range (Ref. 104). This box was the
explode. size of the area of contact of the fuel cell and the vehicle
Even in World War I, mufflers ignited spilled fuel (Ref. hull. These are the design criteria followed:
31). The muffler of the Mark IV English tank was placed on 1. T’m#individual stones were to be larger than the
the roof, as shown in Fig. 4-22, to prevent adding to the heat hole the jet ~ould make in the walls of the box. The stones
within the vehicle; emplacing an unarmored fuel cell beside were to be rounded to facilitate repacking by gravity after
that muffler was not a well thought out field modification. the jet fra~ented or pulverized the stones in its trajectory.
See subpar. 4-3.5.3. Currently, exhaust systems are buned The stones were to be hard enough not to pulvefize quickly
within vehicles to avoid broadcasting an infqmed signature from the jolting received during the cross-country traveling
that could identify the vehicle. Exhaust systems and fuel of the vehicle and not to be subject to interpiece welding
cells, however, should not be located so that a ballistic per- from the ballistic impact.
foration would provide a path for fuel to the e~aust system. 2. Thei sides of the box were not to distort from the
(The results of providing such a path are described in Ref. ballistic impact so that fewer than two pieces of gravel
22.) The exhaust system is too certain an ignition source. could be a~reast between the surfaces of the fuel cell and
the vehicle~,hull. Such gravel piece packing would be
4-8.3 EXAMPLES OF SYSTEM INTEGlk4- deemed suf$cient to interrupt a fuel jet and allow gravity to
TION force the fuel to flow downward.
3. The bottom and lower portions of the outer sides
Some examples of system integration, such as (1) locat-
were to have drain hoIes so that the fuel flowing out of the
ing the magazine containing less volatile ammunition
fuel cell would drain onto the ground.
between more highly volatile ammunition and the crew
Tests es~blished that 37-mm (1.5-in.) gravel (maximum
compartment (subpar. 4-8.2.1), (2) the use of storage com-
diameter) Wlasappropriate. A box constructed of 6.25-mm
partments and their contents as additional shielding (subpar.
(0.25-in.) t$ck steel sides, top, and bottom and with 3.125-
4-8. 1.4), and (3) the use of water storage to protect the crew
mm (O.125-in.) thick faces against the fuel cell and hull was
compartment (subpar. 4-8.2.2), have been presented. In all
adeqtiat~ to!withstand the ballistic impact of the 88.9-mm
of these examples, items installed within a combat ve~cle
(3.5-in.) w~head jet, and there should be a layer of gravel
are made to serve an additional function.
76’~ (3 in.) thick. Further, these tests showed that a box
Mobility fuel is a necessary evil in combat vehicles. me
which protiided a gravel space 41.4 mm (1.63 in.) thick
next three examples provide good and bad techniques of
would defo~ under ballistic impact to the point at which
fuel storage to assist vehicle designers.
the gravel could not settle freely and properly to fill the pas-
sage the jet~made. Also porous lava rock would pulverize
4-8.3.1 Advanced Survivability Test Bed (ASTB)
too readily ~and would not gravity pack as would the
FueI Barrier rounded rip gravel given the same ballistic impact. An
When a material is placed in a separate compartment to empty box proved to .beinadequate because the.fuel, given a
avoid hazardous effects, the designer must assure that bal- fair head, c~ld traverse the gap and pass through the hole
listic damage does not allow em.ryof the hazardous material made by the, Jet. Further design optimization was not pur-
or its effects into the protected compartment.’ sued. ,
Early designs of external fiel cells mounted on the rear of This desi~, which was used in the ASTB (Ref. 71), was
the ASTB vehicle allowed a significant amount of fuel to tested successfully for both forward and reverse trajectories
enter the troop compartment when a shaped-charge jet (Ref. 23). J@ the reverse trajectory, a baseline test with no
passed through the external fiel cell into the troop compart- fuel barrier produced a conflagration, whereas the protected
ment (referred to as “forward trajectory”) (Ref. 23). Simi- version pro$uced a short-lived fireball. In some earlier work
larly, when the shaped-charge jet passed through the vehicle by Dunn (Ref. 105), the shaped-charge slug plugged the
hull, the troop compartment, the vehicle hull on the other hole in the @hicle hull, as shown on Fig. 4-41, but plugging
side, and then into the external fuel cell (referred to as by the slug ~cannotbe depended upon since it occurred only
“reverse trajectory”), shown in Fig. 4-23, the jet pressurized three times ~ 30 tests (Refs. 23,24, and 105).
the t%el via hydraulic ram and fuel spewed back into the A supplementary ASTB system design feature was place-
troop compartment through the hole made by the jet. In both ment of a ~compartment covered with a ballistic fabric
cases the flash and/or splash back of the hull ignited the fuel immediately inboard of the hull wall to which the gravel
spray and conflagrations occurred. box and fu~l cell were attached. The compartment contained
The means used to preclude these “fuel injections” into a 5 l-mm (2-in.) layer of gelled water. Examination of the
the troop compartment was placement of a box containing ASTB vehi~les’after several months revealed that a fungi-
flint river gravel between the vehicle hull and the external tide andlor~bactencide
/ should have been used in the gelled
fuel cell. ~s setup was a larger version of a bullet baffle water. The \ballistic fabric traps both span and spray. The
developed earlier to trap 5.56-mm bullets to prevent their gelled water quenches fire and remains in place, even with
I

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MIL+MDBK-684
mm (0.188-in.) thick comugated steel, which had 19- x 76-

o
‘1 mm (0.75- x 3.O-in.) slots to pass sand so that the bladders
would not abrade.
Each fuel cell had a capacity of 144 L (38 gal). ‘l%efuel
cells in these tests were usually filled with gasoline to 25 or
62.5% capacity and in some tests to 0.6, 37.S, or 75% of
capacity. The fuei cells were approximately 965 x 762 x
193 mm (38 x 30x 7.6 in.). The reticulated foam was fully
packed in each cell. The less than fulI level of gasoline in
these cells translated to the unweaed foam thicknesses in
the ullage of the test cells from 48 to 193 mm (L9 to 7.6
in.).
When the simulated mine exploded under the vehicle, tie
shaped-charge jets passed vertically in turn through the hull,
the penetration detector, a fuel cell, and a floor plate. In
addition, the blast from the remainder of the simulated mine
heaved everything upward, including numerous pieces of
span from the hull. Gasoline from the ruptured cell was
Figure 4-41. Slug Plugging Hole in Troop Com- sprayed into the vehicle and burst into flame. On some oca-
partment Wall of the APC Ml13A3 (Ref. 105) sions the atmosphere within the vehicle was too fiel rich for
ignition (Ref. 107).
small punctures in its container, but a shaped-charge jet Several fire suppression techniques were tried. Some of
passing through fiel and gelkd water disperses the water these restricted the quantity of gasoline thrown into the
through the same region in which the fuel is dispersed. crew compartment. These tests used a fire suppression sys-
tem that consisted of numerous Freon@* (Halon 1301)
4-8.3.2 LVTF-5A1 Fuel $ysteiri Reticulated Foam extinguishers, that were activated by optical sensors. The

o
When a device is described as providing a given benefi~ sensor system signaled the extinguisher system within 3.5 to
the designer must establish the conditions and ckcum- 4.0 ms after fire initiation. The Halon was discharged into
stances under which that benefit was obtained and then the troop compartment about 20 ms after hull penetration
evaluate whether the device will provide the same benefit with a discharge duration of 20 to 120 ms {Ref. 18). h dl
given the conditions and circumstances prevailing with the tests a penetration detector (break-wire type) provided addi-
new application. tional data. This penetration detector system was tested as a
Explosive tests were perfotmed on the LVTP-5A1 in the potential replacement for the optical sensor system. Not
late 1960s to establish crew stivability given detonation enough tests were conducted to explore each parameter sep-
of a beach or htnd mine under a track (Ref. 18). The beach arately, but in general, when no HaIon was used there was
mine was simulated by two white phosphorus grenades usually a conflagration. When IZalon was used, there was
above a box that contained 4.54 kg (10 lb) of Composition nomnally a 457-mm (18-i,tt.) diameter fireball approximately
C-4, 1.134 kg (40 OZ)of which were packed into two Mark 1.22 m (4 ft) above the deck. When there was no reticulated
3 shaped charges. These Mark 3 charges are Explosive Ord- foam in the fuel cell, the fireball expanded to the deck but
nance Disposal (EOD) devices consisting of a can with a when there was reticulated foam in the fuel cell, the iireball
shaped-charge iinex in one end into which a plastic explo- did not spread. If there was not reticulated foam in the cell
sive, like C3 or C4, can be hand packed- These simulated where the shaped charge perforated the he] cell, tAe exit
mines were placed underneath the hulI of the LVTP-5A1. hole was approximately 305 mm (12 in.) in diameter. If
The space between the 9.53-mm (0.375-in.) BHN 300 steel there was reticulated foam in the fuel cell, the exit hole was
hull and the 4.8-mm (0.188-in.) BHN 120 correlated steel approximately 5 I to 76 mm (2 to 3 in.) in diameter (Ref.
dedting contained 12 bladder fuel cells with a total capacky 107). When the fuel cell was 62.5% fill (a fuel depth of
of 1726 L (456 gal) of gasotine. These bladders were con- approximately 121 mm or 4.75 in.) and there was reticu-
structed of relative] y lighmveight rubberized fabric 0.81 mm lated foam in the cell, a great amount of span was captured
(0.032 in.) thick with a heavier layer of polyurethane within the fiel cell (Ref. 18).
approximately 3.2 mm (O.125 in.) thick on the exterior to The reticulated foam was credited with reducing the size
provide abrasion resistance. These bladders were not self- of the fireball, reducing the effect of blast upon the bladder,

o(, sealing or even tear resistant (Ref. 106). 3n some tests these
bladders were filled with Sc@t Type 1,0.4 pore per mm ( IO
pore per in.) reticulated foam. ‘I%e fuel cell bladders were
*Tltesetests were performed before the generic term Halon bad
been adopted.The mattiaI used was Freon@FE 1301,which was
held 38 mm (L5 in.) above the hull by trays made of 3.18- tenamed‘HaIon1301.

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and capturing fragments from the charge assembly and span

from the hull. However, these charges were pointing
upward; thus there was an unwetted thickness of reticulated
foam above the fuel level. Since the shaped-charge jet
would core out reticulated foam, the foam surrounding the
hole undoubtedly captured the fuel droplets that would
travel in the wake of the jet and move radially outward from
that wake. In addition, the hole in the bladder was signifi-
cantly smaller when the foam was present. Undoubtedly the
fuel was effective in stopping most of the span, and the
foam impeded the liquid fuel, which otherwise would have
splashed against the bladder and increased the size of the
hole.
At a much later date, the use of reticulated foam was sug- Figure 4-42.’ Russian T34/85 Tank Showimg Jet-
gested to reduce the size of the fireball generated when a tisonab~e Fuel Cell
shaped-charge jet perforated a fuel cell because the foam
had worked so well before. However, this time the jet was
traveling horizontally, not vertically, so that there wak no
unwetted foam and no rubberized fabric with a urethane
coating backed up with mild steel to capture some of the
fuel spray. Therefore, no decrease in fireball size due to the
reticulated foam was noted. In fact, there appeared to be
numerous sparklers present in the fireball that were absent
in the tests without reticulated foarm thus these sparklers
were assumed to be minute burning particles of the reticu-
lated polyurethane foam (Ref. 24). ,

4-8.3.3 Wtkomakde Fuel Cells

Practically all Russian tanks have provision for attach-
ment of jettisonable fuel cells orI the rear. These fuel cells
are thin steel drums, which, on the most recent vehicles, are
cantilevered off the rear. These drums are intended to pro- (A) Overall View
vide fuel to enable the tank to reach the battle area where
the drums are then jettisoned. The jettison is done when the
tamk is stationary because a crewman has to disconnect the
fuel line ‘and unbolt the drum-holding straps. Since these
di-ums are cantilevered off the rear of the vehicle, the possi-
bility that a ballistically generated fuel ~e will affect the
vehicle is remote unless the threat throws the fbel onto the
vehicle. The situation was different with the T34 tank and
the JS-3 tank because the drums were mounted on the rear
fenders, as seen in Figs. 4-42 and 4-43(A), and spilled fuel
could enter the engine compartrqent.” As illustrated on Fig.
4-43(B), fuel flowing out of perforations would not travel
downward into the engine compartment, but a rupture of
these drums could result in fuel being thrown onto the rear
deck. The latest MBTs are built so that these jettisonable
fuel ,@ums are cantilevered off the rear; therefore they can
be perforated and the fuel ignited without endangering the (B) dose-l,lp of External Fuel Drums
vehicle or crew. An explosion from below and to the rear of
the vehicle, however, could throw diesel fuel upon the vehi- Figure 4-43. Russian Joseph Stalin III (JS-3)
cle. If the hatches were open, this fuel could incapacitate Heavy Tank
exposed personnel, and if sufficient fuel entered the hatches,
it could damage the vehicle.

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Mlt.-HDBK-684

One test described in Ref. 23 illustrates the advantage of bustion of the diesel fuel within or kaked fkom the fuel cell

o using a jettisonable fuel cell. l%e external fuel cell was held
by a steel platform held by two bolts that had been weak-
ened by previous tests. In Test 3 the bolts failed and the fuel
did not occur (Ref. 108). lltis test showed that diesel fuel in
a fender fuel cell will not necessarily burn, even though it is
ignited by a material hot enough to melt through a thin steel
cell dropped. (See Fig. 4-44.) llms fuel stopped flowing shee~
through the jet perforation in the simulated vehicular hull. In another test program an extemaily mounted frangible
With this cessation of fuel the fire within the simulated vehi- fuel cell had a shaped charge fired through the fuel cell.
cle burned out. It also illustrated that if the external fiel cell ‘Ihere was a fireball within the fixuue. The external iire was
were removed after it was hit by a projectile that would spectacuhu, but the burning within the fixttne was not sus-
overwhelm the vehicular armor, no more fuel wotdd flow tained. In other tests the external fire was a little less spec-
into the vehicle to burn. ‘fhis same result was obtained in tacular when the fkangible fiel cell was covered with
five more tests with frangible or jettisonable fuel cells (Refs. packets of dry powder fire extinguishant, i.e., Purple ~.
26 and 27). Another test demonstrated that if three hngible fuel ceils
Use of jettisonable fuel cells could provide a means to were separated by metal dividem, only the fuel cell hit by
have a combat vehicle wavel to a combat area without using the shaped charge would be 10SLas shown in Fig. 4-45. Use
the internally stowed fuel and without requiring a refueling of frangible fuel cells is promising, but another device must
operation before it could be committed to action. Also the be used to eliminate the internal firebal~if the compartment
jettisonable fuel cell would not make the combat vehicle is occupied (Ref. 26).
more vulnerable while traveling. Jettisonable fuel cells ‘I%epotential use of such fuel cells requires further evalu-
could be considered for use on US vehicles. ation.

4-8.4 LESSONS LEARNED 4-8.4.2 We of Mumescent Coatings

Several lessons have been learned in combat and in The main bustle magazine for the MIA1 MBT is divided
development or qualification tests. into two separate compartments, each of which contains 17
combustible case cartridges. Each KE cartridge has an 8.1-
4-8.4.1 hSSODS Learned FrmI Tests of External kg (17.9-lb) JA-2 (Ref. 109) propellant charge, and each

0,,
Fuel CelIs HEAT cartridge has a 5A-kg (12-lb) DIGL-RP propdlant
In a recent program to explore the vulnerability of exter- charge (Ref. 84). Both are in combustible cases with metal
nal fender-mounted fuel cells to incendiaries, response to an bases. lhe magazine is designed to withstand the detonation
incendiary grenade was tested. The incemiiuy grenade of one warhead-the high-explosive charge in the HEAT
products melted through the upper fuel cell surface, passed warhead is much smaller than the cartridge propellant
through a 51-mm (2-in.) layer of diesel fuel, and made a charge-and the explosion of all 17 propellant charges with
small hole in the lower t%elcell surface, but sustained com- only the loss of two blow-away doors, one on the top of the
magazine and tie other on the-bottom. Access to this maga-
zine is prvvided by two sliding doors-a %ady” door at the
loader’s station and a “storage” door at the commander’s
station--which are opened or closed by hydraulic power
operated by the loader’s knee switch (Ref. 11O). These

Fud Cell ~ -

Fii4-44. Test No. 3ShowingJet&onedF@

,,,
0
Cdl (Ref. 23)
Figure 4-45. Posttest cOrditiOII of l?rangibl~
External Fuel Cells (Ref. 26)

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,.
MIL-I+DBK-884

doors are made of 1020 mild steel 28.6 mm (1. 125 in.) thick have a diffi~uh enough job just to keep operating as is. They
and measure 762 x 762 mm (30 x 30 in.) (Ref. 111). ~o not need items that require constant attention. A fire pre-
In some tests these doors appeared to leidc combustion vention device that does not require daily maintenance and 4
products due to heat distortion. Blackbody temperature in a that does nbt require a crewman’s conscious action to be
propellant fire is a function of the propellant type, and for activated ii preferable to one that needs testing and has
this propellant it is approximately 3092°C (5598”F). The manual initiation.
duration of the fire was from 8 to 30s. The temperature and For the second lesson Phillips provides two passages,
duration of the fire could result in a t@ermaI gradient wl$ch are highly illustrative:
through the door thickness, which in turn could caqse the 1. “In, terms of human casualties, however, the tank
door to warp temporarily and thus allow the leakage noted crews were far more fortunate than the infantry and the gun-
(Ref. 111). ners who accompanied the infantry. The man with the rifle,
This thermal gradient could be reduced by coating the the artillery [forward observation officer] FOO and the anti-
inside surface of the door with an intumescent material, and uuik gunner had no shield against the flying shell-splinters
several candidate intumescent materials were recommended and the bulleti. But tank wounds could be shocking.”
(Ref. 112). In tests after the intumescent coating was 2. “To the surprise of the garrison, a number of Ger-
installed, the leakage did not. recur. This intumescent coat- man panze~s which had halted in dead ground after their
ing also kept the temperature of the’doors low. This intu- attempted move in the night suddenly broke cover at ranges
mescent coating was incorporated into the Ml series MBT of horn 6~1 to 800 yards. They thus offered highly tempting
design. rev and fla$k targets at killing ranges to the riflemen’s gun
detacbment~ as they peered out in the biting wind.
4-8.4.3 Lessons Learned From North ‘Africa, 1942 ., “In ~uch circumstances, it was perhaps not in accord
There were two lessons—well-illustrated in Phillips’ either with $octrine or with their mission for the garrison to
Afarnein (Ref. 56j-which have been taught and retaught. disclose th~~ positions and engage. But they did not feel in
These lessons are (1) combat vehicles should be as mainte- a calculating spirit that day and could not resist the tempta-
nance free as possible and (2) vehicle armor is too protec- tion to attack. fie dawn was shattered as eight or nine guns
tive, too safe, for the crewmen to abandon their vehicle too barked witlj ~e 6-pdr’s sharp, high velocity crack. The
quickly. results were spectacular. Eight tanks and self-propelled guns
Writing of operations in North Africa, Phillips stated: were destroyed to the north (all being found derelict on the 4
‘“Tankscould carry only a limited amount of fuel and battlefield subsequently) and a further eight were claimed
ammunition and these had to be renewed in’a long action. horn Teege~s battle group to the southwest of which three
For this purpose regiments had a special echelon of unar- were still derelict on the ground a month later. Upon the
mored lorries (‘soft skins’ ). When ammunition was needed, unfortunate ~crews who attempted to escape the machine
they might often be required to drive right up into the heart guns pouref their streams of bullets.”
of a battle and unload, round by round, by hand. For fuel These passages illustrate-not only that the tank armor pro-
replenishment, however, the tank had to withdraw.,. Except tects the crt!w from artillexy shell fragments and bullets, but
in the most critical situations, it also had to withdraw every aiso that in the confusion of battle, combat vehicles can be
night for mechanical maintenance tasks, for general replen- hit from the side or rear and that where there are antitank
ishment, for food, and for such rest as was possible. weapons, ~ere will also be machine guns. Colonel Teege,
“Withdrawal was usually into a ‘leaguer;’ which in the of the Stifflemayer Battle Group of the Deutsch Afrika
open desert, meant ‘close leaguer,’ with all the tanks, soft Korps, would not have taken his panzers in front of the
skins, field and anti-tank artillery and infantry in a solid English posltion “Snipe” if he had known it was there. The
phalanx, defensively disposed. Whhdrawal, which might best survivability enhancement feature that can be given a
involve an hour or more of cautious and difficult driving, combat veliicle is the capability to continue to move until
could not take place until well after dark. Maintenance by the vehicle leaches a location where the crew can safely dis-
the crews and repairs by the [Royal Electrical and Mechani- mount or to~preclude fire within the vehicle so that the crew-
cal Engineers] REME detachments would go on far into the men can stay within their vehicles to defend against
night. The crews were often too dog-tired at the end of itto attackers. Since most vehicles in World War II stopped
bother about cooking a meal aqd would eat nothing but a lit- when the aiiununition exploded or the fuel ignited, preven-
tle hardtack before bedding down where they were. tion of the+ e,vems can do a great deal toward providing
“Each man then had to stand an hom”s guard, so that this movement-to-cover capability or the capability to fight
about three hours was the maximum of sIeep before @e from within, an immobilized vehicle.
crew had to be up again, and after tea and a biscuit, drive
back to their battle or patrol position.” *’Thesewere six-pounder antitank (AT) guns (The US used this
This quotation illustrates why combat vehicles should be same gun, the 57-mm AT gun.) manned by men from the 60th 9
designed to be as maintenance free as possible. Crewmen Riflesof the ~fle Brigade.

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4-8.4.4 Protection Afforded by Water and Other ysis Center of the Southeast Asia Ground Vehicle

o Materials in SEA
There were several incidents that occurred in SEA which
may pmvi& lessons for fire protection.
database for incidents on M113, M132, M106, M125,
M528, M48, and M551 vehicles, plus the User Guide
for the Southeast Asia Ground Vehicle database, and
In one irtcident an RPG hit an Iv1551in the rear.The jet applicable Data Acquisition Number files of selected
passed through a Marmite can containing food and into a incidents, Wright-Patterson Air Force Base, OW 1989.
19-L (5-g@ water can. The jet stopped in the water (DAN 7. D. A. Starry, Moumzd tlbnbat in Wtnam, Vlemam
333). In three incidents in which RPGs hit PiPCs M113AI Studies, Department of the &my, Washington, DC,
arid the jets entered radiators, the jets stopped in the radia- 1978.
tors or were othemise ineffective (DAN 360, 331, and 8. Armor Reference Note, RNT7510 T7512, US Army
1874). These incidents indicate that locating items contaitt- Field Artille~ School, Fort Sill, OK, February 1969.
ing water within a vehicle may increase fire survivability. 9. War Department Pamphlet No. 20-17, Lasons
In one incident an RPG hit an AR/fiV M551 smoke gre- Learned and E.rpedients Used in Comb, July 1945.
nade launcher and the jet stopped in the grenade (DAN
10. Department of the Army Pamphlet No. 20-269, His-
16%). In another incident (DAN 336) a shaped-charge jet torical Study, Small Unit Actwns During the German
entered through the side of an APC Mll 3A], hit a k
Chnpaign in Russia, July 1953.
extinguisher bottle, and stopped. These incidents indicate
11. MJL-HDBK-1 14, Mobility Fuels User Handbook,
that there are a number of items that, when mounted on the
exterior surface or the inside of the wall opposite that sur- January 1984.
f= can prevent fire by stopping the jet. 12. A. D. Rasbeny, CPT J. H. We.athenwix, W. J. Butler,
Jr., E. A. Ftame, P. I. Lacey, and S. R. Westbroo~ Per-
4-8.45 Engine Compartment Design fomw.nce of Fuels, Lubricants, and Assoca2r.tedPrvd-
ucts Used During Operation De.rert.Shiel&&onn, US
For several reasons and regardless of engine type, there
Army Belvoir Research, Developmen~ and Er@neer-
should be no gravity flow path for liquid fuels horn the
ing Center, Fort Belvoir, VA August 1992.
vehicle deck to the engine, the air intake, or the mdiator.
Elimination of such flow paths precludes contamination of 13. Letter from MAJ E. F. Fagan, FA, to P. H. Z&A,

0 these components by accidental combustible fluid spills and

wouid render Molotov coclmils ineffective.
Southwest Research Institute, Re: Fires in FAASVS in
SWA, 17 May 1992.
14. Conversation between L’IC R. B. AndersoL FA, and
REFERENCES P. H, Zabel, Southwest Research Institute, 21 June
1992.
1. Tracked Vehicle Fire Analysis, Attached to Letter,
15. J. Tury, Erternal Fuel T& Temperatures, Bradley
Subjecc Tracked Vehicle FE Analysis, To Com-
Fighting Vehicle Technical Report 4487, FMC Corpo-
mander, US by Materiel Development and Readi-
ness Cormnan& From PESC-GS, US Army Safety tition, San Jose, Q D&ember 1986;
Center, Fofi Rucker, AL, 16 May 1980. 16. P. H. Zabel, Southwest Research Institute, Intemiew
with maintenance personnel, Fort Ho@ ~ July
2. D. S. RicketsOn, Jr., J. M. Segraves, and LTC F. G.
1988.
SislG Tracked Vehicle Fire Analysis: 1984 Update,
USASC TR 84-2, US by Safety Center, Fort 17. D. C. Isby, Weapons and Tmrics of the Soviet Army,
Rucker, AL, June 1984. Jane’s Publishing Co., Ltd., London, England, 1988.
3. Extracts ffom Amy Accident Reports involving fires 18. M. J. Cosgrove, IL C. McMahon, and R. T. O@ Final
in armored vehicles and Navy Shore Fm Management Repon LVTP 5Al Vehicle Fire Suppression System,
Reports also involving fires in armored vehicles made Tkdnical Report No. 1666, FMC Corporation, San
during Fkcal Wars 1983 through 1987. Colkxted by Jose, CA, March 1967.
US Army Safety Center, Fom Rucker, AL. 19. MJL-T-27422B, T~ Fue~ Crash-Resistant, Aircrafi,
4. P. H. Z&.+4and J. M. Vlc% “Fii Survivability Issues 24 Febtuary 1970.
From Southeast Asiau Experience”, Ptwceedings and 20. MIL-B-83054B, Bajj?eand Inerting Materia~ Aircraj?
Repon Fire SafeqXSurvivabiiity Symposium-’9O, Fuel T&, 17 May 1978.
lklexancki~ VA, November 1990, Defense Fiie Pro- 21. T. Hansbaw, Mine Da.tzJBase Warsaw Pac~ 2nd Edi-
tection Association, Alexandria, VA. tion, Countennine Laboratory, US Amy Mobility
5. Telephone conversation, P. H. Zabel, Southwest Equipment Research and Development Comman&

0,,
Research Institute, with W. Haggerty, FMC Coqxxa- Fort Belvoir, VA January 1983.
tion.31 July 1991. 22. P. H. Zabel, Test Prvgram to Demonstrate Enhanced
6. Data searches by Survivability ‘Information and AMI- Survivability of Amwred Aluminum Vehicle Fuel Sys-

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MIL-HDBK-684

tern to Shaped-Charge Attack, Report No. 06-8899- Parameters, and Design Considerations for Pneu-
001, Southwest Research Institute, San Antonio, ‘IX, matic Inlet Control Systems, presented at the SAE
prepared for US Army Ballistic Reseatch Laboratory, Natio~ Aeronautic Meeting, Los Angeles, CA, 4 9
Aberdeen Proving Ground, MD, 31 July 1986. Octo~er 1957, Society of Automotive Engineers, War-
23. P. H. Zabel, Shaped-Charge’ Test Pe~ormance of Fuel rend~e, PA.
Tanks for the Advanced Survivability Test Bed Vehi- 34. R. Y. i~oshida, Synthesis of Pneumatic Networks, MS
cles, Report No. 06-8899-003, Southwest Reseirch Thesis, University of Califomiz Los Angeles, CA,
Institute, Sah Antonio, TX, prepared for US Army Februhry 1960.
Ballistic Research Laboratory, Aberdeen Proving 35. N. Lockman and R. Y. Yoshida, The Application of
Ground, MD, 27 Februwy 1987. Pneuktic Stabilizing Techniques and Network Shap-
24. P. H. Zabel, M. J. Lewis, Jr.; and B. Bonkosky, Surviv- ing for Pneumatic Servo Systems, Paper presented at
ability Enhancement of Advanced Survivability Test the Fluid Power Control Seminar, 14-24 June 1960,
Bed Vehicle Given a Slmped-Charge Hit Through the Massachusetts Institute of Technology, Cambridge,
Engine Compartment Fuel Tank, Report No. AS~- MA. 1
87-2, US Army Tank-Automotive Command, Warren, 36. P. H. ~bel, “Temperature Control and Measurement
,,
MI, 31 July 1987. by a ~neumatic Bridge”, Temperature, Its Measure-
25, T. E. Sanderson, Special Study of M60A3 Automatic ment and Control in Science and Industry, Vol. 3, Part
Fire-Extinguishing System (AFES), Report No. 2, A~plied Methods and Instruments, Reinhold Pub-
USACSTA-6564, US Army Combat Systems Test lishing Company, New York, NY, 1962.
Activity, Aberdeen Proving Ground, MD, August 37. MIL-~-5606F, Hydraulic Fluid, Petroleum Base: Air-
1987.
crajt, Missile, and Ordnance, 6 December 1990.
26: P. H. Zabel, B. Bonkosky, and M. C. Artiles, “An
“38. MIL-~-6083E, Hydraulic Fluid, Petroleum Base, for
Alternate Approach to the Halon Fire-Extinguishing
Preservation and Operation, 14 August 1986.
System”, Paper presented at the ADPA Combat Vehi-
39. MIL-H-83282C, Hydraulic Fluid, Fire-Resistant, Syn-
cle Survivability Symposium, Gaithersburg, MD,
thetic;Hydrocarbon-Base, Aircraji NATO Code Num-
1992, American Defense Preparedness Association,
Arlington, VA. , ber H-537, March 1986.
40. MLL-H-46170B, Hydrau!ic Fluid, Rust-Inhibited, 9
27. P. H Zabel, Passive Techniques to Counter Ballisti-
cally Initiated Fuel Tank Fires, Script and Video Synthetic Hydrocarbon-Base, August 1982.
Report, Fjnal Report 06-4838-001, Southwest 41. MIL-H-53 119(ME), Hydraulic Fluid, Nonflammable,
Research Institute, San Antonio, TX, February 1992. Chlorotrijuoroethylene-Base, 1 March 1991.
28. S. R. Westbrook, L. L. Stavinoha, and M. B. Treuhaft, 42. MIL-~-22072(AS), Hydraulic Fluid, Catapult,
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55. Telephone conversation between P. H. Zabel, South-
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60. G. A. Beale, W. E. Roe, and K W. Bailey, Impact 74. J. Magnuski, Combat Vehicles of the People% Polish
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Turbine-Driven Fuel Pump for the XRJ-43-MA-3
Ramjet During the Period April 1951 to November

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a
85. Telephone conversation between T. Mihmov and S: J. Facility, Las Cruces, NM, 12 August 1985.
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0 jea General Dynamics Purchase Order DEM- Proving Ground, MD, August 1987.

. . . -.

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,,
O CHAPTER 5 .

CREW SI.JRVIV” CRITERIA

27ueat@ects tar they@ecr crew survival are described The need for emu perfomcrnce criteria is smea! Crew survival
cn”teriaare givenfor thed ecw lung, and eye injuries. cn”ter~ Coneerniflg ~phy~ ~ to~”c t?~es ~ p~-c~e SO~-
ids are given. Finally, the effects of these threats on human performance are described The Surgeon General has not reviewed
thir chupter; thertfore, the recommendations given should not be considered oflcicd Department of the Army poiicy.

5-0 LIST OF SYMBOLS scaled positive duration, ms

A = cross-sectional area perpendicular to the heat scaled time (using SwlU practice),
flow, rn2 Pa8~z.s.kg-1’3
AP = pupil area, 2nm2 positive duration of pressure (measured at test
Al = total area of body contacted by flames, m2 site), rns
a. = velocity of sound in air, m/s shock wave velocity normal 10jet trajectory,
di = distance between the pointof entry of the jet and m/s
plane of transducer Pj, m jet tip velocity, rnh
d’, = distance between jet and axis of transducer Pi, m fragment velocity, mls
h = film coefficient of heat transfer, W/(m2 “K) thiCk32eSS of material through which heat is
hl = film coefficient of heat aansfer between flames transfesr@ m
and body, W/(m* “K) angle between jet trajectory and shock wave,
$ = specific impulse, Pas deg or rad
“ = scaled speciiic impulse, Pa*a”s” kg-*fi differenm in time of arrival of shock wave at
; = thermal conductivity, W/(rnK) two uansdncers P; and Pj, s

o :’ O/d= penetrator length-to-diameter ratio, dimensionless

m = 332aSS of body, ‘kg
ma = 33MSSof test animid, kg
. =n2assofan average mat2=70kg
emissivity or absorptivity of t12ebody, dirnen-
sionkss
Scefan-Boltzmann constan~ 5.67 x 10q W/
(m’. K’)
:o~ = reference pressure, usually 20 pPa (2.9x 10+ lb/
ilL2) 5-1 INTRODUCTION
P, = peak incident overpmssure, Pa 5-1.1 PURPOSE
P,t = mean atmospheric pressure at sea level, Pa
‘Ms chapter” provides a statement of the crew survival
~, = scaled incident peak overpressure, Pa criteria and describes the ori@n of these criteria and the
F$.u = sailed incident peak overpressum (using South- bases for them.
west Research Institute (SWRI) practice), dimen- Lngeneral, the survival criteria are the liits of the co32di-
siordess tions to which men can be subjected and still continue to
P. = ambient atmospheric pressure, Pa perform their functions as crewmen of combat vehicles.
Pm= @P=- at which SO%of the exposed popu- These criteria are established by the Surgeon General,
lation *1 die, Pa United States Army, and are usually based upon test data
P(I~H) = probability of incapacitation given heat exposure, (Ref. 1).
dimensionless
p = sound p~ being measured, Pa (h/in?) 5-12 THREATS
q = ram of heat transfer, W
‘Ilte primary combat threats to crew and/or vehicle sur-
SPL = sound pressure level, dB vivability are those that penetrate through the armor into the
Tb = body temperature, ‘C
vehicle. These threats are ballitic penetrators that can ignite
T. = measured air temperature, ‘C
cminitiate explosives or ignite mobility fuel or other com-
T] = heat source temperature, K
bustibles, as well as kill or injure personnel and destroy or
Tz = heat sink temperature, K

o
,
=
f=time, s
time of arrival,s
(t=); = time of anival of shock wave at pressure trans-
damage equipment within the vehicles. These ballistic pene-
trators also can project span. The two types of balliitic pen-
etmtors are the kinetic energy (ICE) projectile and the
chemical energy (,CE)high-explosive antitank (K&W) prm
ducer Pi, S
jectile. Some KE penetmtors contain a small high-explosive
ti = ternperamre-time integral, 0C5
J charge in the base, which hgments the rear of the projectile
5-1
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MIL-HDBK-684

and projects .fiagments in a radial patte~. Currently, the Threats ~at are no longer effective against main battle
shorter hard steel or tungsten carbide subcaliber penetrators tanks (MBTs) can be highly effective against more lightly
with a length-to-diameter (t!/d) ratio of approximately 5:1 armored vehicles and may well be encountered. Further, a
are being replaced with finned, long-rod penetrators made weapons th~ are no longer effective against the main armor
of tungsten or depleted uranium (DU), which have an W of the MBT~can be highly effective against the more lightly
-Ored po~ons of *e ~BTs
ratio nearer 20:1. These long-rod penetrators are referred to f
as armor-piercing, fin stabilized, discarding sabot
(APFSDS) projectiles (Ref. 2). 5-1.2.1 Threat Effects in General
The United States (U.S.) and Russia have cluster war- The threats previously described provide kill mechanisms
heads that provide many small bornblets, some of which are that can @ect combat crewmen differently. These kill,
HEAT warheads that can srnke combat vehicles ~om injury, or dapage mechanisms follow:
above. One used in Operation Desert Storm in 1991 was the 1. Large, fast-moving particles of metal that can kill,
Mark (MK) 20 amtitank cluster bomb (Rockeye). injure, or d@ge by simple mechanical impact, e.g., resid-
Another type of threat that has been used is the spaWgen- ual KE pen~etrators, shaped-charge jets or slugs, plugs or
erating, high-explosive plastic (HEP) projectile, called central spal~ from the armor, or fragments from ati armor-
high-explosive squash head (HESH) by the British. Upon piercing, ti~h-explosive incendiary (APHEI)-type projec-
impact on a hard target, these projectiles deform plastically tile (Ref. 6)~
or squash prior to detonation and provide an intimate con- 2. Sm+l pieces of metal, ceramic, or glass, such as
tact with the armor over an area larger than the projectile span or splmh, projected peripherally, forward along the
caliber. These high-explosive (HE) projectiles are intended trajectory of the projectile, or rearward toward the weapon
to generate span from monobloc armor. Ordinary high- during ballistic penetration
explosive projectiles can also generate span but less effec- 3. Sh~ck waves that result from the passage of a
tively. HE, HEP, and HEAT projectiles can remove items shaped-chmge jet or high-velocity penetrator
mounted on the exterior of the vehicle. The blast alone from 4. Blast waves and overpressure from explosions
these projectiles can damage or destroy lightly armored 5. Heat from explosions, combustion, and/or other
combat vehicles., Also the blast and fra~ents from these chemical reactions including those from fireballs that result
warheads can damage or sever the tracks of heavily armored from perfor~on of cells containing combustible liquid
vehicles. 6. Tox}c, asphyxiant, or irritant gases, vapors, liquids,
In World War I the Germans found that the explosion mists, or solid particulate liberated by ballistic impacts or
from four stick grenades clustered together could break the explosions dr by the combustion that can occur afierward
track of a Mark I tank (Ref. 3). This discovery led to the use 7. Th~ flash or light generated by or resulting from the
of land mines, some of which are designed and fuzed to other effect5.
launch a missile (flyer plate or jei) upward to penetrate the The entire antitank projede does not usually penetrate
bottom of a tank (Refs. 2 and 4). Another, type of “land through the’kgrnor; Only the jet! core, or penetrator does so.
mine” is the rocket-propelled HEAT missile with a trigger Once the @nor is perforated, however, not much can be
set so that the tank itself will fire the missile into the side of done to pro~ect against the large metallic penetrators except
the vehicle. Thus land mines are not only a threat to the to inhibit ri~ochet. The smaller penetrators, span, etc., can
tracks of the tank but also to the bottom and sides of the be trapped; ~,therefore, a vehicle can be designed to protect
tank. personnel ~om span or to trap ricocheting particles. Shock
Another means used by the Germans in World War I to waves and ~ash can be mitigated, explosions can be limited
,,
attack &e British tanks was to spurt bur&ng liquid from or made less probable, and the presence of toxic, asphyx-
their man-portable flamethrowe~ onto the tanks (Ref. 5). iant, or irri~t gases, mists, or solid particles reduced. Toxic
However, these flamethrowers were not effective because it chemical, biological, or radiological threats are not consid-
is difficult for a man to leave cover and pursue a tank with a ered in this handbook, except as incident to fires.
36-kg (79-lb) item strapped to his back. In addition, the The mos~hazardous secondary effects are those resulting
burning gasoline would not have been very effective even ~om explosions and fires. There is little reason to quantifi
on those. early tanks, but it gave the Germans’ morale a explosions in this chapter. Explosions are best eliminated by
boost just to think that they had such an impressive weapon the means i/escnbed in Chapters 4 and 7. The most serious
to use. tires, i.e., propellan~ mobility fuel, and hydraulic or recoil
In the Russo-Finnish War of 1940 the Finns were highly fluid fires, should be precluded by passive fire prevention
successful @ using hand-thrown gasoline bombs, “Molotov designs. ~~ only the smaller or slow-growth fires would
cocktails”, against combat vehicles. These Molotov cock- remain to be extinguished. Quantifying or describing heat
tails were effective. because they were thrown on the grille from these fires, combustion products, shock waves, and the
over the engine and would ignite oil and wiring in the light from flash is useful because it provides designers with
engine compartment. quantities to reduce.

5-2
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~:
o
‘,
5-122 Shock PresstIre antior Impulse
The most severe shock waves are generated by the fastest
moving items, e.g., the tip of the shapeckharge jet. This
effects can cause nonfatal injuries that may degrade the
crew’s perfonrmnce if crew members do not evacuate the
vehicle. These cument survival criteria were developed for
shock wave is initially an aerodynamic shock fonxted at the combat vehicles which use fire extinguishants that should
tip of the jet. The initial shock bounces off the internal sur- not be breathed for long periods of time, i.e., carbon dioxide
faces, reinforces or mitigates other shock waves within the or Halort 1301. ‘llte formation of products of incomplete
vehicle and results in a cacophony of shocks on occupants. combustion, such as carbon monoxide or smoke, could be
Jet velocity is a fimction of shapedduwge design and mate- hazardous. If an extinguishant were used that would not
rials, i.e., primarily from the cone angle of the liner, the provide noxious products and would flush toxic and irritant
cone malerial, and the detonation velocity of the explosive gases out of the air, the crew could remain within the vehi-
used. More information on shaped-charge warhead design cle and continue to fighL Such a system has been demon-
and functioning can be obtained fkom Refs. 7, 8, and 9. strated for commercial aircmft (Ref. 12). The purpose of
The shock pressure and/or impulse due to the jet fkom an this handbook is to show how to design vehicles to absorb
M28A2 HEAT warhead (used on a 3.5-in. baxooka rocket) hits without losing their viability as effective military assets
apparently is not a fimction of material properties of the due to fire. As viable military assets also, the crew membem
inside surface of the targe~ however, the emitted flash and must retain their major assigned functional capabilities.
spa.11and the reflected shock waves certainly are (Ref. 10). There is little that can be done to protect crew members
The initial shock wave from the jet passage, which is dis- from primary penetrators that have breeched the vehicle
cussed in subpar. 5-3.4.1, has neither the greatest peak pres- armor. Crew members, however, can be protected from the
sure nor the greatest impulse. The greatest peak pressure secondary effects, i.e., the span, flash, fireball, explosions,
and greatest impulse usually occur when shock waves and, ptiCdi3rly, i.ke.
“reflectfrom various surfaces and combine. This action sugg- crew-member-worn clothing is not discussed in this
ests that vehicle designers might obtain benefits tint handbook as a device that can be used by vehicle designers
using materials or surface finishes that have sounddeaden- to achieve a vehicle survivability goal. Clothing and per-
ing features. sonal equipment are designed or specified by Government
agencies other than those responsible for the design of com-

o 5-1.2.3
The light
Light
generated by ballistic penetrations has not been
quantied in tests. A shaped-charge jet passing through an
bat vehicles. Clothing and personal equipmen~ however, are
extremely important to the severity of injtuy to a person
subjectedto fire, and spareclothing carried in vehicles can
affect the survivability of the vehicle and its crew. l%ere-
aluminum-walled chamber would emit enough light to satu-
fore, the potential benefits and hazards of clothing and
rate motion picture tilm for three to five frames at a rate of
equipment are included here.
1000 frames per second and do the same to real-time video
Soldiers must “be able to see, hear, thiti and communi-
tapes. Figs. 2-14 and 2-15 provide qualitative evidence that
cate with others-in an active stress situation” (Ref. 13).
such flashes and fireballs can be reduced by selection of the
The senses that infantrymen and other soldiers in combat
proper interior material for the vehicle. The shomsr duration
must be able to use to the best of their ability are sight, hear-
and less intense flash would probably present a lesser igni-
ing, smell, and touch. A soldier must be able to see to aim a
tion soume, as well as have less effect on eyesight. (Materi-
weapon or to detect most targets; he must be able to hear
ais thattend to di.fi%seor absorb light would reduce the
oral communications and enemy activity; he must be able to
effect of these strong flashes on the eyes of crew members.)
smell to detect some tires or some toxic gases, fuel leakage,
andlor many other phenomena present on the battlefield;
5-1.2.4 Vapors, Mists, and SoUd ParticuJates
and he must be able to operate the equipment and weapons
Way mists. vapors, and solid particulate are broadcast and often receive tactile feedback from them. The threats to
within combat vehicles from ballistic impacts, from fires, sight are small flying objects, flash, and very small objects
and fiorn the extinguishment of fires. These mists, vapors, in great quantity, such as smoke, dus~ or misL that can irri-
and particulate are described in Chapters 3 and 7, and their tate the eyes, cause teting, and thereby obscure visicm. l%e
effects upon crewmen, in par. 5-6. Although phosgene threats to hearing, once explosions have been precluded, are
(COCIJ is a potential product of combustionor reaction of shock and aftershock-shocks reflected from the surround-
the various materials caried in combat vehicles, little evi- ing walls-waves. In addition to affecting a person’s hear-
dence of the presence of phosgene has ever been identified ing, extremes of shock to the body and aftershock waves
in instrumented tests (Ref. 11). can affect a person’s sense of balance. The threat to smell is

,,
0 5-1.3 CREW PERFORNLMNCE
Current crew stival criteria assume that fatalities fkom
secondary effects are preventable, but these secondary
satumaon of the nasal receptors and taste buds that can
occur from prolonged exposure to ties, especially those
fkom mobility fiel and some fire extinguishant by-products.
Another threat efftxx similar to those attacking the sense of

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MIL=4-U2BK-684 ‘

smell is irritation to nasal passages and breat@ingpassages, armored personnel carriers (APCS), Ml 13 and Ml 13A1.
which would cause troops to sneeze or cough. Extremes of .These studies used pigs and sometimes rabbits (Refs. 25
either sneezing or coughing render personnel incapable of through 27]; In the 1970s some studies were performed to a
performing their tasks.’ evaluate the protection provided by helicopter crewman
clothing in a fuel fire (Ref. 28); these studies also used pigs.
5-2 THERMAL INJURY These anin!al studies are reviewed in subpar. 5-2.2.3.
Recently there have been studies on smoke inhalation that
5-2.1 BACKGROUND
used sheep @efs. 29 through 31).
The modem study of lethal factors associated with expo- Thus much of the experimental work on bums in the past
sure to fire in wartime was begun in this country in 1944 by 50 years has not directly addressed the problem of predict-
Dr. Alan R. Moritz and his colleagues at Harvard Univer- ing the degree of incapacitation in humans due to heat
sity. First, they studied the effects of heat on the air passages injury. The reactions of animal models (rabbit, dog, goat,
and lungs of dogs (Ref. 14). Then they studied thermal dam- sheep, and pig) to heat stress were certainly useful in these
age resulting from excessive heat applied to the skin (Refs. sk@ies. The pig, in particular, has been extensively studied
15 through 22). These later studies primarily involved pigs, (Refs. 15 though 22,24 through 27), and in many respects
but some human volunteers participated also. is an excellent model for human skin bums. The fact that
Shortly thereafter, the US Army studied @e kill mecha- pigs do not~lsweat,however, limits their usefulness in tests
nisms associated with flame weapons. Initially, the scope of requiring prolonged high heat loads because the sweat
these investigations was limited to determining what the mechanism /in”humans is important. In fact, none of these
lethal factors were and ranking their relative importance in animal mo~els sweat the way humans do. There is no gener-
conditions of poor, moderate, and good ventilation (Ref. ally accepted model of the degree of incapacitation caused
23). Commentary on the cause of some fire-related deaths by heat, especially when conduction, convection, and radia-
during World War D was confusing; some soldiers appar- tion can each furnish significant heat flux and when the
ently killed by fire in bunkers and other enclosed- spaces common c~mplicating conditions found on the battlefield
were ~oted to have no evident burns. In the absence of are supe~posed on the heat injury. Data from the South-
wounds of any kind, a lowered partial pressure of oxygen or east Asia (SEA) conflict are reviewed in subpar. 5-2.2.4.
the breathing of toxic gases generated by ‘the fire quickly General he~th, the presence of certain drugs (such as atro-
became suspect. Later work, however, showec! that pooled pine) that can alter heat tolerance, fractures, dehydration, 9
gasoline-fueled fires in poorly ventilated spaces will self- hemorrhag~~crush and penetration injuries, and blast over-
extinguish while, the oxygen content of the ambient air pressure cat all be expected to change the predicted degree
remains above 14% (which will support life), and measured of incapac~~ from heat exposure, but the relationship
concentrations of common toxic gases are frequently not among the~ is not described in the available literature.
sufficient to cause the deaths that were observed. Of course, When the c~nfounchg variations of indlvidua.1responses to
vigorous agitatioh of the fuel-air mixture (as effected by a heat (Ref. 32) are added to the poorly understood interac-
flamethrower spurt) can cause consumption of virtually all tions of heat with other stress factors, it becomes apparent
available oxygen and produce lethal concentrations of car- that extrapolation of existing data is problematic. Therefore,
bon monoxide, carbon dioxide, and other noxious gases. predictions ~~ffuture levels of disability, either on the battle-
This work, however, suggested that heat alone could be a field or dun~g recovery, should be expected to contain sig-
lethal factor, whether or not skin bums were evident (Refs. nificant error on this basis alone.
18, 20, and 21). Most of this work involved goats. Obvious There is la problem defining thermal injury. The com-
burns then must be regarded as indicators of excessive heat monly used ‘benchmark has been a second-degree skin bum.
but not necessarily as accurate predictors of the total The second~degree bum is associated with a wide range of
amount of heat damage that has been done or the perfor- disability Ad recovery times because it includes all depths
mance degradation that may result. of skin b~s from shallow to deep. Degrees of a burn are no
Studies have been performed” to assess how effectively longer considered in bum clinics, such as the US Army
fire-extinguishing systems protect occupants of combat Brooke Bd Center, which now classifies bums by whether
vehicles from a fireball that results when a shaped-chwge jet or not-the ~~ darnage extends through the skin (Ref. 33).
passes through a hydrocarbon fuel cell and then enters an Ftist-degre~ bhs, e.g., mild sunburn, are not considered
occupied compartment. These studies usually involved the because they should not require hospitalization. Excessive
placement of animals, usually pigs, within the vehicle. The heat intake can be fatal even without visible skin bums, as
first such study was in 1967 for an automatic fire-extin- has been s~own by animal tests. On the other hand, when
guishing system planned for the Landing Vehicle, Tracked, personnel a~ the US Army Aeromedlcal Research Labora-
Personnel (LVTP)’5A1 (Ref. 24). In the late 1960s, and tory developed a computer model to predict the severity of
early 1970s, studies were performed to evaluate the ade- bums behl~d clothing, they used a 16-point clinical bum 4
quacy of the fire detection-extinguishing systems for the grading system, a 10-point micrograde system, and a mean

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burn depth determination to resolve better the relative effi- toxic or asphyxiant gases and noxious liquids and parricu-

o cacy of fabrics to provi& protection (Refs. 34 and 35).

5-2.1.1 problem Magnitude

The degree (depth), location, and incapacitating potential
lates that can be introduced.

5-2.L2.1
5-2.L2.1.1
Skin Burns
Heat ‘bnsfer
of thermal burns-based on commonly measured parame- I-kat energy transfers into the skin by conduction, con-
tem-that may be suffered by crew members in armored vection, and/or radiation. When hot solid objects or droplem
vehicle fires are highly variable and not precisely predict- of hot liquids contact the skin, heat is transferred by conduc-
able. Ignition of solid gutI propellant produces gas tempera- tion through a film. The film heat transfer coefficient is a
tures of approximately 2527°C (4580”F) for M30 propellant function of the intimacy of contact between the hot object
or 2256°C (4093W) for M26 propellant (Ref. 36); the and the skin. Where there is intimate contacL the h resis-
resulting short-duration, high-intensity mdiation can cause tance approaches zero; where there is a gap, the film resis-
flash burns that may vary in character from those produced tance approaches that of conduction through the thickness
by nuclear weapons to those produced by a carbon arc. Tests of air or fluid within the gap. The film coefficient for trans-
with aerial bombs and flamethrowers suggest that tempera- ferring heat from a stationary hot liquid droplet to skin is
tures in fzres that follow rupture of fuel cells or injection of roughly equivalent to the lesser values for water or oil given
burning liquids into the crew compartment can exceed in Table 5-1. The form of the equation for conductive heat
1000eC (1832”F) (Ref. 37). The Army currently uses the mansfer ~m a heat source to a heat sink is
time integml of teznporature difference, i.e., measured air
tenzperatum minus skin temperature, to predict risk of ther- q = X24(T, -T2)/x, w (5:1)
mal injury in vehicle fires (Refs. 1 and 37). If the integral where
over 10s exceeds 1316°C,s (2400%s) for unprotected skin, 9 = rate of heat transfer, W
the occurrence of second-degree burns or worse is IikeIy. K = thermal conductivity, W/(m-K)
However, the presence and type of protective clothing or A = cross-sectional area perpendicular to the heat
heat shields, amount of ventilation, duration of heat expo- flow, mz
sure, temperatures and types of hot materials, and initial T, = heat source temperature, K

0 conditions determine the final injuries and the degree of

incapacitation. Each of these factors is discussed in this
paragzaph. Problems associated with the heat content of
gases generated during armored vehicle fires are discussed
T1 = hem sink tetnpemture$ K
x = thickness of material through which heat is
transferretL m.

in this paragraph, but the discussion of problems associated T%is equation applies when the heat source and heat sink
with their toxicity is reserved for par. 5-6. stay at constant tmzqmatures. This equation does not apply
to a small fkagment or droplet that has a finite quantity of
heat available for ~fe~ ~ t$e heat is tmnsferred, T1
5-2.12 Medical Considerations
q~ckly approaches T2 (Ref. 38).
The heat effects or thermal injury to personnel that con-
cern the survivability engineer are divided into five catego-
ries:
1. Skin Burn. The degree of a burn can range from
sunbuzn to chiming of muscle or bone. TABLE 5-1. APPROXIMATE RANGE OF
2. .&@ Overtenzperanue (Hyperthennia). Hyperther- VALUES OF TEE COEFFICIENT OF HEAT
mia is a form of heatstroke in which the overall body tem- TRANSFER BETWEEN A SOLID SU’REACE
perature fises. (For adults a core temperature over 43*C AND A FLUID (Ref. 38)
(110”F) is usually fatal.)
3. Localized Overtemperature of Body Parts. This
heat effect results in heat exhaustion or in hypexkalemia
(excessive potassium in tie blood), which causes central
% (h;~°F)
circulatory failure me heart slops pumping effectively.) Air, Heating or Cooling 1.14-57 (0.2-10)
that often results in shock Oii, Heating or 57-1700 (10-300)
4. Upper Respiratory Tract Damage. When over- Coding
heate~ the tissue swells (edema), the throat (pharynx), Water, Heating 284-17,000 (50-3000)

;~
0
vocal cords (larynx), andhr windpipe (tzachea) close, and
the hrngs do not receive air.
5. lung Damage. Lung damage is caused by smoke
inhalation, whiclI may later develop into prteuznoni%and by
Steam, Film-Type
Condensation
Steam, Dropwise
Condensation
5700-17,000

28,00@l 14,000
(1OOO-3OOO)

(5000-20,000)

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MIL4-IDBK-684
The primary means of heat mmsfer to the skin from mov-
ing fluids is convection. Convection is related to the move- q = AI GO(T:– T~ +hlA1 (Tl –T2) (5-4)
ment of fluids, both gaseous and liquid. Fluids that we where
stagnant, i.e., are not flowing laterally or through a passage, hl =1film coefficient of heat @ansferbetween flmes
expand or contract as they gain or lose heat and thereby 1!and body, W/(m2.K)
become less or more dense and move vertically because of A, =1area of body contacted by flames, mz.
changes in buoyancy. This transfer process “iscalled natural
convection. If the fluid is forced through “apassage or is oth- 5-2.1.2.1.2 pegree and Extent of a Burn
erwise imparted motion, the heat tr~sfer process is c~led The degree of a bum is defined in older literature (Ref.
forced convection. In both cases heat is transferred to a solid 39) as
object through a stagnant film, which is in intimate contact 1. First Degree. Redness of skin (erythema) without
with the object. This film has zero velocity immediately blistering
adjacent to the surface of the solid object. The faster the 2. Second Degree. Redness of skin with blistering
3. Thi~d Degree. Destruction of fill thickness of skin
fluid flows, the thinner the thickness of this stagnant film.
and often o~deeper tissue.
Rather than compute the thickness of the film to compute
A fourth degree is referred to in some references. This
heat transfer, empirical relationships are used to establish a
fourth degree would be a very severe bum in which charring
film coefficient of heat transfer for each fluid. This film
occurs well into the muscle or to the bone. The current clin-
coefficient contains both the thermal conductivity of the
ical divisio~~of bums is either as partially or wholly through
fluid and the thickness of the film, therefore, Eq., 5-1 the skin (~f. 33). “Partial” is the old second degree;
becomes “wholly” is the old third degree. The extent of a bum can be
e@mated b; using Table 5-2.
q = hA(T1– T2), W (5-2) Data preymted by Dressier et al (Ref. 40) suggest that
where mortality fr{m skin bums has decreased markedly as better
h = film coefficient of heat transfer, W/(m* -K). treatments ~ been developed. The fatality rate when
third-degree~bums cover more than 75% of the body surface
Because the fluid is moving, Tl can be considered con- is nearly 1~% (Ref. 41). In the period 1956 through 1964,
stant. Relative values of the film coefficients for heat trans- second- and@hird-degree bums over 2670 of the skin area of
fer are given in Table 5-1. The lesser value is for slower the”entire b~dy had a 50% probability of fatality. In the
period 1965jtbrough 1968, bums over 38% of the total body
moving fluids, the greater value, for fast-moving, turbulent
skin area had the same probability of causing fatalities,
fluid flows. Convective heat transfer applies to the exposed
whereas in the period 1980 through 1981 this result was
surface only. If clothing is the outer surface, the heat trans-
caused by bums covering 65% of the skin area. (Ref. 40) In
fer from the fluid to the clothing is by convection, but the
these cases,: infection of the bums was not always deemed
heat transfer from the clothing to the body is by conduction.
The”tid means of heat transfer is radiation. Ml bodies
radiate heat as a function of their temperature and the emis- TABLE 5-2. PERCENT OF BODY
sivity of their external surface. These same bodies receive SURFACE AREA FOR ADULTS
radiated heat as a function of their temperature and the (Ref. 40)
absorptivity of their external surface. The for!n of the radi- EACH, TOTAL,
ant heat transfer equation (Ref. 38) between a body and a 70 %
blackbody is Head 7.0 7
Neck 2.0 2
(5-3) Half Trunk, Anterior or Posterior 13.0 26
where Buttock, Right or Left 2.5 5
E = emissivity or absorptivity of the body, dimen- Genitalia 1.0 1
sionless Upper Arm,’Right or Left 4.0 8
~. Stefan-Boltzmann constant = 5.67x 10-8
Lower Arm; Right or Left 3.0 6
W/(mZ. K’).
Hand, Right or Left 2.5 5
Heat transfer to a body engulfed in flame is through a Thigh, lligh~ or Left 9.5 19
combination of radiation and convection. The equation Leg, Right or Left 7.0 14
(Ref. 38) is Foot, Right or Left 3.5 7

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MIL-HDBK-684

the primarycause of death- Shock or respiratory complica- Similar exposure time data are available for radiant

o tions were often rhe primary cause of death, but the burns
were at least contributory factors.
energy. For example, Fig. 5-2 shows the radiant energy ver-
sus time needed to obrain moderate fit-, second-, and
third-degree burns (Ref. 42).
5-2.121.3 Results of Skin Burn Tests
Some results of sld.rt bum tests are shown on Fig. 5-1. 5-2.122 Hyperthermia
‘I’he threshold first-degree and second-degree exposures, 5-2.1.221 Body Temperature Regulation
shown as lines, were obtained using flowing water on limi- Wit is added to the body fkom the basic metabolic pro-
ted areas of pigs. Similar tests wem conducted with human cesses (breathing, blood circulation, alimentary traq food
volunteers, indicated by symbols on Fig. 5-1, using flowing movemen~ etc.), food intake, and muscular activity. Heat is
writer or oil (Ref. 16). These burn thresholds were later lost from the body by radiation, convection, and conduction
duplicated using radiant heat instead of flowing liquids horn the skin; vaporization of sweat; respiration; and by uri-
(Ref. 18). In short, the method used to transfer the heat to nation and defecation (Ref. 41). In an environment of 21°C
the skin is not important. Only tie temperature of the skin (70W) approximately 97% of the heat is lost from the skin.
and the length of exposure are important in determining the Heat is brought to the skin horn the body core prirnady by
resultant skn burn. the blood,

70
i HumanSkinHeatedWti Flowing
0 First-DagreeBum
Water
65 { @ Sword orThi@4?egree
Bum .
~ OFirst-UegreeBum
{ *Sword- orThii-Dqee Bum

0 for !%eond-f)egreeBurn
Threshold
~ (P@SkinHeatedWti FIo+vhtg Water)
.

45 .

40 I 1 1 1 11111 1 1 k 111111 t I # 1 Iflll 1 i 1 1 1 4111 1

10 100 1000 10,000 30, Clos

J i 1 1 I 1 1 I I I I 1[
1 2 345710152030406U mFn

1 1 1 1 II
1/2123 5 6h

0:
,: Figure 5-L
Time a! Temperature

Skin Response From Temperature &posure (Ref. 16)

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MIL-I-?DBK-684

Raising body temperature 1 deg C (1.8 deg F) requires

adding about 251 kJ (238 Btu) of heat per 70 kg (154 lb) of
body weight. Pigs exposed for varying lengths of time in air
temperatur~~ ranging from 70 to 550”C (158 to 1022”F)
have been ~~died (Ref. 22). Pigs exposed for 15 min to an
air,temperat~e of 80°C ( 176°F) and for 30 s to an air tem-
pe~ature of ~500°C(932°F) while breathing cool air (20”C
(68°F)) suffered acute hyperthermia and death. In each case
there was c~culatory failure. During the longer exposures,
peripheral vascular control was lost; this loss resulted in
lethal drops in blood pressure. During the short exposures
+ere appears to have been failure of the heart to continue
10C
effective pumping action. Each of these exposure models is
considered ~ greater detail in the paragraphs that follow.
I During prolonged exposures the effects of body cooling
0 2 4 6 “B 10 should be ~onsidered. The same 251 kJ (238 Btu) of heat
DutationPammetsr= Kme Ior D#hwY
of80%
of Total
FIssh
Enerw,
s that can rai~e body temperature by 1 deg C (1.8 deg F) in a
70-kg (154~lb) person can be removed by evaporation of
Reprintedwith permission.Copyright@byNewYorkAcademy of 100 mL (3.~8 fl OZ)of sweat. Under favorable temperature
Sciences
and humidit’yconditions, a 70-kg (154-lb) person can main-
Figure 5-2. Radiant Energy Required to Cause tain a stabl~ body temperature while producing and absorb-
Flash Bm (Ref. 42) ing a total of 1.26 to 2.09 M.T/h(1191 to 1985 Btu/h) during
strenuous exercise. Thus existing animal data must be care-
fully interp~eted when predicting the work capacity of peo-
ple under ~~ high heat loads. The normal oral body
The human body regulates its temperature within a very temperature is 37°C (98.6*F). Although a core temperature
narrow band, i.e., usually within 0.5 to 0.7°C,(0.9 to 1.3°F); of 39.5°C (103. 1‘F) means collapse is likely, a core temper-
‘the core temperature is approximately 37.5°C (99.5”F). ature of 43°C (110“F) is lethal. Effective cooling through
Heat that is transferred to the body from external sources is normal mechanisms is highly dependent on the relative
retained until it is transferred from the body by the normal humidity ~~ velocity of the ambient air over exposed body
body processes. The primary means used by the body to parts. Avo@mce of incapacitating heat loads during normal
lose excessive heat is sweating. The heat loss from sweating operation of a vehicle may, by providing reserve heat stor-
is due to evaporation of the water in the sweat. Vaporization age capacit~ in each person, lengthen the period of useful
of one gram of wa(er requires approximately 2512 J (2.379 function w$ler emergency high-heat conditions. By pro-
Btu) of heat, which would normally come from the skin. longing the ,penod before cell injui-y or serious performance
Sweating is not effective when the sweat glands are dam- degradation; becomes inevitable, the likelihood of survival
tid success~l escape or fire suppression increases.
aged, the person is dehydrated, the humidity is high, the per-
son ii immersed in moisture-saturated air or a liquid, or the
5-2.1.2.2.3/ Localized Overtemperature of Body
person is wearing clothing impermeable to moisture, such
Parts
as certain chemical warfare protective clothing or even rain
gear or arctic outer clothing. Exposure to severe heat can also cause heat exhaustion,
which is due to inadequacy or collapse of the peripheral cir-
culation w~h associated salt depletion and dehydration.
5-2.1.2.2.2 Reaction to Excessive Heat
Mental coifusion and muscular incoordination may also
The reaction of the human body to excessive heat is occur (Ref. 39).
either to elevate the body temperature (hyperthermia) or to EIyperpotassemi4 which can result from localized over-
suffer local injury. Elevating the body temperature results in heating, is {aused by the release of potassium by damaged
drowsiness and loss of mentrd control with death a possible muscle tissue (Ref. 39). When it reaches the heart, this
result; for adults a core temperature of 43°C (110°F) is usu- potassium cw cause shallow, rapid, and irregular heartbeats
ally fatal. Hyperthermia is basically heatstroke and is char- (ventriculavt,achycardia) and fluttering of the heart muscles
acterized by loss of consciousness and failure of the heat- (ventricular: fibrillation), which result in failure of the heart
regulating mechimism (Ref. 39). Local injury can be skin to pump blood and possible death (Ref. 41).
burns, local swelling (edema), or heat damage to the muscle Heating ~f the skin can result in expansion of the under-
tissue beneath the skin that results in rapid liberation of lying blood vessels (cutaneous vmodi~ation). ~s can result
potassium, which can result in hyperpotassemia. in shock. ~

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MIL-HDBK-684

The cell damage and death that result from thermal injury studies were made of the effects of heated fluids or smoke
,, on the lungs, either an insulated tube was emplaced in an
are in turn associated with increased pemtteability of cell
o membranes and capillaries. The potential for incapacitation animal so the researchers could preclude beating of the
due to a burn injury is highly dependent on its location, throat or the vocal cords (Ref. 14) or the smoke was cooled
depth, and area. For example, the tissue swelling that to ambient temperature before it was inhaled (Ref. 3 1).
accompanies burns may be relatively inconsequential if it All inhaled fluid that includes a mist or spray of hot Iiquid
occurs on a small portion of the baclG but the same amount droplets contains much more heat than gas molecules do.
of swelling may be lethal if it occurs in the airways. Therefore, the spiny transfers a greater amount of heat to the
Depending on the temperature of the heat soume, radiant air passage tissue, so it greatly shortens the time required for
energy may penetrate well below the skin surface before the passage to close. This reaction is also true for live steam
being converted to lteat (Ref. 43). Experimental work with a (Ref. 14). Inhalation of hoh dry gases causes heat injury
carbon arc source applied to rats at energy densities between mainly to the mouth and windpipe (trachea); however, inha-
0.33 and 0.67 J/mra2 @ and 16 Cal/cmz) showed that most lation of steam, small solid particles, or other components
of the damage was done after 0.5 to 1.0s of exposure.l%e with relatively high specific heats compared to the specific
author of Ref. 43 observed that contact burns with the same heat of air causes tissue damage that extends into the lungs.
appearance as fiash burns are not associated with the same Except when accompanying lung damage is extensive, the
deep tissue damage. Thus brief exposure to tigh-tempaa- physiological response to upper ainvay burns may be
ture (radiant energy) sources may result in flash burns that delayed for several minutes to several hours. The delay is
leave little or no evidence of skin injwy but cause both due in part to the fact that though swelling @ins almost
acute and delayed destruction of muscle cells. Death may immediately after a bunt, it does not reach a maximum until
result due to the release of potassium horn the hatdam- the second postburn day. ‘Rius crew members may have
aged red blood cells (Ref. 40). The excess potassium causes time to execute escape maneuvers even after they have sus-
changes in heart rhythm that reduce the pumping efficiency tained potentially lethal burns. After upper airway or lung
of the h- and it causes death due to shock (inadequate burns, obstruction of respiration may develop acutely and in
blood circulation to vital organs). Incapacitation from ther- conjunction with delayed swelling of Iung tissue (puhrm-
mal burns may be immediate or delayed. nary edema).
,. Shock may also ensue if the peripheral circulation is
o damaged by heat that is more slowly applied. h may result 5-2.1.2.2.5 Lung Damage
primarily from the shift of fluid out of the bloodstream into
5-2.1.2 .2.5.1 Smoke Inhalation
the surrounding tissues bectmse of capillary kaks. Follow-
ing more prolonged heat exposure, shock can aho be caused The most serious problem for paple caught in fires is
by imperceptible water losses, e.g., perspiration and mois- smoke inhalation. One of the most hazardous materials that
ture in the breath Crew members may lose more than 2 IA can be breathed is carbon monoxide (CO), which results
(2.1 qt/h) of fluid through perspimtion.To a person who had from incomplete tmmbustion of many materials. Another
a mild fluid deficit before entering the vehicle, the loss of an hazardous condition is the reduced oxygen level caused by
additional 2 L of fluid could be incapacitating or even fatal. the combustion,. Table S-3 provides a relationship between
The Combat Lifksaver program was started to reduce the CO concentration and human response. Ildu&tion of smoke
incidence of shock in US casualties. Special training teaches and other materials present during combustion of most com-
participants how to reduce shock, and supplies of water and bustible items can have similar noxious or toxic effects.
intravenous injection devices and fluids are provided (Refs.
44 and 45). If fire-fighting and escape procedures occupy 5-2.1.22.52 Heated Air
more than a few minutes, crew members who were not fidly Inhalation of hot air that actually reaches the lungs would
hydrated Mltial.lycan be expected to suffer rapid and severe probably have little effect upon the lungs. This conclusion
performance decrements. was demonstrated in several tests with dogs, seven of which
inhaled clean hot air at 159 to 291°C (318 to 556°F). At
521.22.4 Upper Re.spimitory Wet Damage most these temperatures caused moderate injury to only the
The tissue lining the throat (pharynx) and the vocal cords upper windpipe (trachea). One dog inhaled 106 breaths of
(@nx) is particularly sensitive to heat. These tissues swell 350”C (662”F) air and survived. In these tests the throat and
readily when exposed to h- e.g., when a person breathes vocaI cords were protected by an insulated tube (Ref. 14);
heated air. lle swelling can be great enough to close the air otherwise, the dogs would probably have been choked by a

o air -e (upper respiratory tract obstructive asphyxia} then

cannot reach the lungs (Ref. lLI). For this reason when
throat swollen shut. Hot air alone would not contain enough
heat to damage the lungs, but live steam would.

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MIL-HDBK-684

TABLE 5-3. RELATION BETWEEN oped and contains most of the supplies needed (Ref. 45).
These suppljes are used for all types of casualties not only
CARBON MONOXIDE CONCENTRATION
@e injuries because fluid replacement is a first principle of
AND HUMAN RESPONSE (Ref. 46) combat casualty care (Ref. 48) and the best preventative of
co heat exhaus~on. Combat vehicles should carry a supply of
CONCENTRATION, SYMPTOMS OR REMARKS drinking water. Because of the high percentage of wounded
ppm arriving at field hospitals during the Vietnam conflict in a
25 T’LVfor conditions of heavy labor, state of sh~ck from which approximately 15 to 20% died,
high temperatures, apd decreased, the US Army introduced the Combat Lifesaver Program in
air pressure 1982 (Ref. 47). The Army has approximately one trained
50 TLV and MAK value Medical Corps person for every 40 frontline soldiers. This
100 No poisoning symptoms, even for ratio, however; is not sufficient to provide fust aid to the
long periods of time wounded, who’often need treatment sooner than the Medi-
200 Headache &er 2 to 3 h cal Corps @rsonnel are able to provide it. All soldiers
receive trair$ng in first aid, but the only equipment provided
300 Distinct poisoning after 2 to 3 h
to individu~ combat arms soldiers is a tirst aid packet suit-
400 Distinct poisoning after 1 to 2 h
able for bullet wounds. As long as individual soldiers had to
500 Hallucinations felt in 30 to 120 min carry all the~ equipment, it was not practical to issue infan-
1000 Difflcuhy of ambulation; death after try or cava~men with the items needed to treat shock. W]th
2 h of inh~ation me high level of mechanization today, however, such items
1500 Death after 1 h of inhalation cm be stowed aboard vehicles. The equipment fiunished by
3000 Fatal in 30 min the US Army Academy of Health Sciences includes the
8000 + Immediate death by suffocation items neede~ to administer intravenous solutions and other
more advanfed first aid treatments. The intent is that one
TLV = tentativelimit valuein a workingarea (US)
crewman on each vehicle be trained in the use of the medi-
MAK = maximumallowableconcentrationin a workingarea
(Germany) cal supplie$. This program operated outstandingly well in
Panama in ~989; there was only one incident of shock in
Reprintedwithpermission.CopyrightGTechnornicPublishing 250 cases of wounded evacuated to the rear from clearing
co., Inc. stations. Re~ords are not available to evaluate results from
Desert Stor&, but a total of 36,000 kits were sent to Somh-
5-2.1.3 I%o@c%ive Equipment and Protection l?ac- west Asia (SWA), which included an ins~ctor’s manual
tcms (Ref. 49), two student’s manuals (Refs. 44 and 45), and the
5-2.1.3.1 Vehicular Requirements equipment and supplies necessary for this expanded first aid
treatment.
BUS overlarge areas of skin result in the rapid depletion
Another aspect of thern&l bums-that may delay recovery
of circulating blood volume with accompanying hernocon-
or cause death is the possibility of contamination of open
centration. Rapid infusion of replacement fluids can delay
burn wounds by common disease-producing (pathogenic)
the incapacity that will inevitably accompany the slow heal-
bacteria or chemical warfare agents. Incapacitation due to
ing process characteristic of bums. However, the immediate
these exposties maybe abrupt or delayed by several days,
return-to-duty rate for crew members with bums of bands, depending on the general health of the crew member and the
face, feet, or the genital area is low. Many of these patients type and concentration of the contamination. Consideration
are at risk for kidney (renal) failure and wil~ require long- of these factors is governed by current medical and chemi-
term, intensive care. caI defense ‘doctrine and the threat assessment. Nearly all
The complications crewmen suffer and the length of their modem armored vehicles contain toxic gas filtration sys-
hospital stay can be reduced through appropriate early med- tems that function in both offensive and defensive chemical
icaI intervention. In the early management of burns there are warfare operations. At least one recent war (the Iran-Iraq
three priorities: (1) maintenance of an airway, (2) control “of war, 1980 to 1988) reportedly produced large numbers of
blood loss, and (3) fluid replacement (Ref. 47). Depending chemical agent casualties. The most likely materials to be
on the current doctrine in far-forward medicaI care, certain encountered are persistent agents such as thickened mustard
instruments and supplies to accomplish these tasks may be (I-ID) or soman (GD), and nonpersistent agents, such as
carried in the vehicles. Combat medics carry the special sarin (GB) or hydrogen cyanide (AC). AII of these chemical
equipment needed, but the number of these medics is lim- agents, except perhaps hydrogen cyanide, axe absorbed at
ited. A special kit, which weighs approximately 4.1 kg (9 lb) accelerated ‘!rates through burned or otherwise damaged
and has a volume of 0.125 m3 (0.44 ft3), has been devel- skin.

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,,
O !
5-2.L3.2 Protective Clothing
Mtho@I a detailed discussion of protective clothing is
not within the scope of this handbook it is appropriate for
imat.dy 3290 (2.5 x 1316)”C+ before second-degree burns
are likely. If radkmt energy is an important factor, as it is in
armor-penetrating events, evahatom must consider the use
designers and crew members to remember the substantial of heat flux calorimetry to measure total heat transfer.
reduction in burn severity that can result from the proper Heat flux was not measured in early vehicle fire tests, but
use of protective clothing. Survivors of fires routinely repart recent tests of the Ml MBT included it. Calorimeters were
the importance of protecting exposed skin areas, often with placed at face, waisq and calf levels. For these and similar
relatively I@ materials. The very brief duration of expo- tests the criterion for significant thermal injury has been
sure to high temperatures that chamcterizes some munitions 0.15 to 0.17 J/mm* applied to unprotected skin within 10s.
&es emphasii this point. Thus it is important that the Two layers of light clothing would provide protection
vehicle &signer, who is not expert on the types of protec- equivalent to about 0-23 J/mm2. Thus the thetmml criterion
tive clorhing availabI% should nevertheless have an uttder- for injury of a protected person would be 0.38 J/mm2, i.e.,
standing of the physiological heat loads the clothing 0.15 + 0.23, within 10s. These values represent only rough
imposes, as well as other factors that may affect perfor- guidanc% however, they do illustrate the substantial protec-
mance of the wearer. If design options can alter the expected tion that relatively simple clothing can provide. Thus insur-
~ of tiJV, the type of protective clothing available ing s@cient cooling in the crew and passenger
may influence the final vehicle configuration choice. It is compartments to allow use of at k.ast the minimal protective
impractical to protect people against sustained high temper- clothing described should be a minimum design goal. In
atures in the crew compartment but it appears feasibIe to addition to reducing the debilitating effects of heat stress,
offer some protection with two light Iayers of clothing (Ref. this capability would also prevent the accumulation of per-
50), which should incIude gloves, caps, and goggles. A spiration on clothing. Damp clothing tends to defeat the pro-
computer model is available to predict the burns to bare skin tective characteristics of the chetical warfare protective
(Ref. 34). There is a potential to expand this to include pro- ensemble, and it subjects the wearer to steam burns if the
tection from heat provided by a fabric (Ref. 51). In the outer garment flames or heats above 10&C (212”F) or if

,, absence of more sophisticated guidance, each vehicle there is contact with hot surfaces.

o
should have sufficient ventilation andhr cooling to allow
the crew members to wear this minimum protective ensem- 5-2.1.4 FulI-Scale Tests
ble comfortably. hsttumentation requirements and injury criteria to be
Table 5-4 provides the reactionof fidnics to heaL All fab- used in a medical evaluation of nonfragment injury effects
ric in modern battlefield garments can be expected to react in live-fire tests of armored vehicles have been prepared by
eventually in a vehicle fire, but until the fabric is consumed personnel al the Walter Reed Army Institute of Research
two light layers of fire-resistant fabric offer a skin protection (Ref. 1). l%is document (Ref. 1) was reviewed by the
t%ctorof about 2.5. This mess that the time integral of tem- Armed Forces Epidemiologic@ Board of the Department of
perature difference previously described may rise to q?prox- Defense (DoD) which has made the following statement

TABLE 5-4. REACTION OF’FABRICS TO EEAT (k!&. 52 through 55)

FABRIC MELTS DECOMPOSES IGNITES BURNS CHARs LOI* OTHER
“c {“l=) “c (T) “c (“F) “c (“F) “c (W) “c (“F)
cotton — 305-320 255-400 850 16.0-19.0
(5S0-610) (490750) (1560)
Wocd — 57(MOO 23.8-28.0
(HI) (1060-1100) (1%0)
Acrylic — 285-310 460-560 850 17.3
(540-590) (860-1040) (1520)
Nylon I 215-255 315-420 450-s70 875 20.1-26.0
(420-490) (60@790) (801060) (1600)
Kevlar@ 29.0
Nomex@ 371+ 26.7-30.0
(700+)
Polybenzimidazcde 540 41.0-58.0 425**
(PBl) ;3) (1004) (797)
0 km] = limitingoxygea indecqi.e.. the percentoxygenin a nitrogen-oxygenmixturethatjust sustainscombustion
*Wemperaruxeat whictItensileand compressivestrengthsboth approachzero

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IVHL-HDBK-684

“The technical document outlining the criteria for After penetration of an ACV, the first 10 s are critical to
estimating nonfragmentary injuries behind defeated the risk of ~ermal injury. A significant temperature eleva-
armor represents an appropriate and systematic tion beyond~this time would compel the crew to evacuate
approach on this topic. The Board further recommends @e vehicle unless they could control the fire. Slowly devel-
the use of animal subjects in any continuing studies. oping therm!l events could be identified by the crew, which
Failure to do so would ultimately risk the possibility of could then j~son the burning material, control the fire with
subjecting human occupants of armored vehicles to, handheld fir? extinguishers, or evacuate.
serious injury or death.” (Ref. 56) !,
5-2.2.1 Da&-Gathering Techniques Used in Llve-
Full-scale vehicle tests have been limited in scope to con-
Fjre Tests
siderations of air temperature, heat flux, and damage to ani-
mal models or manikins (Refs. 24 through 27). At the time The best; measurable, environmental correlate of burn
of those tests, criteria used to assess the severiV of thermal potential is heat flux calorimetry. In early live-fire tests
bums were general in nature and provided little guidance (LFTs) thk parameter was not measured. In the Ml LIT,
regarding the incapacitating effects of the different types of however, heat flux measurements were taken that allowed
bums that can be expected. An approach that would yield ~e surnmati~ of radiant, conductive, and convective, ther-
more useful results would describe the crew and passengers mal loads. The source and duration of the thermal exposure
of the vehicle realistically with regard to cloting, state of were found ~$obe quite important. In the Bradley fighting
health, heat tolerance, and ability to act to l@it bum injury vehicle (B~) LIWs most of the heat recorded during
after a fire has started. Minimization of injury will be depen- armor-penetrating events came from convection of heated
dent on all of these factors plus training in the proper emer- g~es and i~adiation by long-duration, infrared energy (Ref.
gency procedures: Appropriate use of animal models would 1). [
require extension of experimental work to combined injury During @e Ml and MIA1 tests, exposed calorimeters
models including hot liquids, flame, radiant heat, hot solid were placed~at the face and waist region of each manikin,
surfaces and particles, and the related trauma, i.e., fractures, and addition? calorimeters were located beneath clothing in
bruises, penetrating wounds, crush injuries, and blast dam- the chest an? calf regions. To assess injury, the criterion of
age, observed in manikins. No controlled human trials are 0.16 J/mm* \(3.9 cal/cm2) applied over 10s was used. This
reported with this type of data, and it is unlikely that any procedure was judged reasonable by a group of bum experts
will be conducted. Review of combat records, some of (Ref. 1). ~~
which are in the Battle Damage Assessment and Repair Pro- Witness boards developed by the US Army Environment
gram (BDA.RP) database described in subpar. 4-1.2, can Hygiene Agency (AEHA) were placed at the head, waist,
provide guidance on the general classes of injury that and calf locations for each crew position. Although they are
should be represented, but further part- and full-scale tests calibrated to indicate the presence of heat flux below the
will be needed to collect the quantitative data necessary to level capable of causing second-degree bums, they were
draw conclusions on vehicle design. It will be especially used in this test to tisure that bum data were obtained even
important to characterize completely the physical environ- when electronic instrumentation was lost.
ment in the vehicle through improved heat-sensing instru- The instr@nentation recommended by the Surgeon Gen-
mentation. In this respect, use of animal models should be eral is described in Ref. 1.
II
reduced by, use of more and better instruments. Existing
data and mathematical models can provide most of the 5-2.2.2 Second-Degree Burn Criterion
information needed to locate a bum physically and to The Army’s second-degree bum criterion uses free air
describe it grossly (Refs. 51 and 57), but more precise mea- temperature and is correlated loosely with heat flux criteria
surements of the vehicle environment combined with simu- (Ref. 1). As in the BFV Phase II LITs, continuous free air
lation trials are required to allow reaIistic extrapolation of temperature ~~
measurements were made at calf, waist, and
the animal data to quantifi human incapacitation. eye levels f~r all crew positions. Free air temperatures and
exposure tinjes were related to second-degree burn predlc-
5-2.2 THERMAL INJURY ASSESSMENT tions for exqosed bare skin by using the time integral ri of
Accurate prediction of crew survivability from fires measured ~ temperature T. less body temperatureJ T~
wi@in armored combat vehicles (ACVS) is difficult because (37°C (98.6°F)) according to the following equation:
of complex interactions between the thermal environment,
biologic response, and clothing protection. This subpara-
.o~aph addresses the technique used in tests to predict a
crewman’s receiving second-degree (or worse) bums (Ref. where
J J (Tm – Tb)
ti= ; dt, ‘C.S (5-5)

1) and provides the available combat data and descriptions t = time over which temperature is measured, s.
of the combat vehicle tests conducted to date.

5-12
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Second-degree burns to bare skin were predicted if the 5-2Q3.1 Tests of the LVTP 5A1
integral of temperature over 10 s excee&d 1316eC.s The first
setof two tests was conducted to establish the
o (2400°F.s). Since convective and conductive heat Lransfer eficiency of the Freon@* fire-extinguishing system with an
are nwxly linearly correlated with he air ternpexature, the optical tire-sensing system plus other miscellaneous devices
temperature-time integral should also be linearly related to to protect occupants of an LVTP 5A1** from fire ignited by
the measured heat flwx. the explosion of a beach mine (Refs. 24 and 58). The LVTP
Unless it catches fire or melts, any type of clothing offers 5AI was a steel-hulle& gasoline-fueled amphibious vehicle.
some protection in a brief thermal exposure. In a significant Six anesthetized weanling Chester white pigs, plus several
thermal enviromnenl however, no presently used battlefield window display manikins dressed in Marine Corps fatigues
garment will resist igmition for longer than 10s. As noted in or Non2ex@uniforms, were emplaced for each test In both
the BFV Phase II LFf mpq either battle dress uniform tests each of the eight fuel cells located beneath the troop
(BDU) or Nomex@, plus either an air space or an under- compartment contained 94.6 L (25 gal) of So-octane gaso-
SM affords 0.22 J/mmz of protection-an amngement line, i.e., 83% full. These fiel cells werw fully packed with
that protects tie skin by a factor of 2.5. This protection fac- Type I (orange) reticulated polyurethane foam. ‘fbe bladders
tor can also be used for helme~ goggles, boots, balliitic were made of conventional aircraft bladder material with a
ves~ etc, even though these materials are expected to pro- urethane coating to provide abrasion resistance (Ref. 59).
tect crewmen more than clothing does. To predict the sec- The troop compartment 6re-extinguishing system used four
ond-degree burn protection provided by clothing, 0.22 J/ CO1 cylinders each containing 4.5 kg ( 10 lb) of Freon@ FE
mmz should be added to 0.15 J/mm*, and the time-temper- 1301 per MIL-M-12218B (Ref. 60), This system had six
ature integral before the garment ignites should be multi- opticnl detectors, which provided the sigtud for the control-
plied by the protex%on factor. If the measured heat transfer ler to initiate the extinguisher squibs. A wire-grid penetra-
exceeds 0.37 J/mm2 or if tie value of the corrected integtal tion sensor system was also installed to test an alternate
exceeds 3300°C.s (WXPF.s), seconddegree burns are system, it supplied a signal to a recorder to establish com-
likely (Ref. 1). parativetimes. AU hatches were closed in both tests.
A thermal equivalency chart that compares the time-tern- ‘Ilte explosive charge used for the first test on 28 Febm-
perature integral and the hat transfer required to obtain a ary 1967 included two MK 3 shapeddarge cans, each of
second-degree burn on skin is presented in Table 5-5. Other which contained 0.57 kg (20 OZ)of Composition C4 explo-
0 units of heat transfer measurement were reported in the data sive. The MK 3 demolition charge container is a 7&mn (3-
and were converted as indicated in this table. i,n.) diameter can 102 mm (4 in.) long with an 80-deg

5-223 Vehicle Tests Involving Animals WIMSexri,nguishan~bromotrifluoromethane,was a Du Pent prod-

uct, Freon@I%1301;this wasbeforethe gemic nameHalon 1301
llree sets of vehicle tests involving animal models were was adopted.
conducted in the late 1960s to middle 1970s. lltere were **US M~e ~rp~ L~ 5A1s were never rntiiified tOhciUde
also tests of aircrew uniform materials during this period. this tire-extinguishingsystem

TABLE 5-5. THERMAL EQUIVALENCY ‘IABLE FOR

SECOND-DEGREE BURN OF SKIN (Ref. 1)
EXPOSED UNDER
mm CLOTHING
TIME-TEMPERATURE
lNTEGIUL: 1300”C-S 3300°c-s
240&’F.s 6000%

=T TRANSFEk 0.035 cal/mm2 0.088 cWmn2

0.15 J/rnmz 0.37 J/mmz
12.9 Btu/ft2 32.5 Btu/ft2
1.46 x 10$W.s/m2 3.68 x 10s W.s/m2

o
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NUL-HDBK-684 ‘

included angle copper liner in one end and a filler of hand- in Ref. 58. A program was started in 1968 to provide such a
picked Composition C4. TTie two shaped charges were system. As was described in subpar. 4-1.2, the APC M113
placed under the LVTP 5A1 below the second port fbel cell; was used as@n armored cavalry assault vehicle (ACAV) in
one MK 3 was at a 63.5-rmn (2.5-in.) standoff, and the other
at an 88.9-mm (3.5-in.) standoff. These two improvised
II
SEA at that bme; hence most of the testing was done with
open hatches. After completion of the development program
shaped charges were initiated simultaneously. The optical in which the fire-sensing system was redesigned (The LVTP
detectors began sensing light above the deck in 3 ms. The 5A1 had the breakwire between the hull and the fuel cell,
extinguislxmt valve squibs were initiated at 18 ms, and the but the Ml ~~3had the breakwire between the fuel cell and
fire was out in 64.5 ms. the occupant compartment.) and the extinguishant system
All six pigs survived. Pigs” 1 and 2 were singed and sized, three confirmatory tests were performed, which
soaked with gasoline but had no skin bums. Pig 1 had a included animal models. For the first test eight pigs with an
small span injury. Pigs 3 and 4 also had small span injuries average m~s of 17 kg (weight of 37.5 lb) were placed in the
and some tiny bums from hot metal bits. Pigs 5 and 6 had crew compartment or suspended over open hatches of an
no apparent injuries. All of the pigs were sacrificed, half APC Ml 13A1 (Ref. 25). In order to determine their physio-
immediately and the other half 24 h later. None of these pigs logical reactions, these pigs were not anesthetized. The fire-
had injuties to the respiratory tract or lungs that could be extinguishing system consisted of two 5.4-kg (12-lb) COZ
attributed to the test. Examination of the manikins indicated bottles, each containing 2.3 kg (5 lb) of HaIon 1301 pressur-
that personnel would not have sustain~ skin bums. Several ized to 5.2 ~Pa (750 psi) with dry nitrogen, and a grid-acti-
manikins showed evidence of a fireball. Three manikins vated initiation system. The grid was mounted on a 0.76-
were sprayed with gasoline, and four had span hits. mni (0.030-@.) thick sheet of aluminum that fidly covered
The disc-shaped explosive charge used for the second test the side and{forvvard end of the fuel cell exposed within the
on 2 March 1967 was 4.5 kg (10 lb) of Composition C4 in a troop compbent. This aluminum sheet served as a shield
wooden box with two white phosphorus grenades secured to to prevent a;gross spray of fuel into the troop compartment
the top of the box. There was no discernible fire seen in the upon fuel cLI1‘mpture. For the first two tests the fuel cell
high-speed motion pictures taken within the LVTP 5A1, nor located in the rear left interior of the vehicle contained
was there any signal from the optical detectors. The amplifi- approximat~y 227 L (60 gal) of DF-2 heated to 57 A 3°C
ers used with the optical detectors apparently actuated due (135 * 5°~f A 3.5-in. HEAT M28A2 w~head w= deto-
to shock from the explosion and activated the extinguisher nated static~ly. so that the jet passed through the fuel cell
squibs 6 ms after the charge detonation. The reason for no into the troop compartment.
fire within the vehicle could not be established. The strong In the first test the pigs had been kept in the open in the
ignition source that the shaped-c~arge jets provided in the sun with a surrounding air temperature of 35.6 to 37.2°C
earlier test was absent, and the ‘released Freon” FE 1301 (96to 99°~~and high humidity for approximately 3 h before
could have caused the inside of the vehicle to become tem- being placed in the APC. The temperature within the APC
was 33.9 to 35.6°C (93 to 96°F). These conditions were
porarily inert. The fuel cell and ~e deck plate immediately
severe enough to affect the pigs’ reactions but would proba-
above the charge were thrown rearward in the vehicle. Pig 2
was dead, apparently the victim of impact by the fuel cell bly not cause death. Upon detonation of the M28A2 war-
head, a very large fire ensued within the vehicle. The AFES
and/or deck plate. Neither the pigs nor the manikins showed
extinguishe~ the internal fire in approximately 200 ms; the
any evidence of fire.
Aberdeen ~oving Ground (APG) fire department extin-
Conclusions derived from this program included (1) that
guished the~adjacent ground tire in approximately 1 min.
the fire suppression system tested is capable of extinguish-
Two pigs located inside the crew compartment died shortly
ing fire in time to protect occupants of the vehicle from skin
after the tir<lapparently from extreme heat stress and lack of
bums without producing lung injury under the conditions
wateq both ~d smoke inhalation damage to lheir upper res-
tested (Ref. 24) ahd (2) that the optical sensing system used
piratory tracts. The pig suspended over the commander’s
was not adequate even as modified during the program due
hatch was t~ only pig actively moving; all the other sslrviv-
to lack of reliability. The evaluation personnel also estab-
ing pigs—four inside the vehicle and one suspended over
lished that the wire-grid penetration detection system was
the cargo hatch—were subdued*. These five subdued pigs
adequate; they recommended that the wire-grid penetration
had been e~posed more directly to the events within the
system be used (Ref. 58).
vehicle than,had the one active pig. When be surviving pigs
were releasbd 7 to 10 min after the test, their activity
5-2.2.3.2 Tests of DieseM?ueled APC, M113AI
appeared nokmal. They exhibited no visible loss of equilib-
Due to incidents in SEA, an automatic fire-extinguishing rium nor any sign of eye irritation, and none had any visible
system (AFES) for the APC M 113 series was needed. The
design of the AFES for the APC Ml 13 series was initially *“Subdued”bas been equatedto “shellshocked”by one Ofthe vet-
based upon that recommended for the LVTP 5A I described erinariansinvolvedin thesetests (Ref. 61).
 Downloaded from http://www.everyspec.com

skin burns. Later, when they were sacrificed, their htngs and Two of these pigs died shordy thereafter. The survivors

o upper respiratory tracts did not exhibit any life-threatening

conditions (Ref. 25). ‘l%etwo pigs that died were the only
ones with blackened larynxes; apparently they breathed
were aroused 15 min after the test. They lacked muscular
coordination but were able to stand. The two pigs that died
had first-degree burns, but none of the others had any skin
something that was extremely injurious. This test indicated burns. All of the pigs exhibited some respiratory tract injury
that those pigs subjected to thermal stress prior to the test (Ref. 27). ‘lltis test indicated that ventilation within the
and to severe thermal conditions during the test were at the vehicle was inadequate for rhe situation.
survival-nonsurvivtd point. Only the pig subjected to the In the second test six pigs were suspended in harnesses,
leas stress during the test was apparently still fully active and the upper hatches were closed. The commander’s hatch
immediately after the test. and the cargo hatch blew open after the charge detonation.
In the second test again a veg large fire ignited within the The internal fire was extinguished in 190 ms, and the exter-
vehicle; this iire was extinguished in approximate] y 150 rns. nal fitE was extinguished and the ramp door opened in 2 to 3
The pigs for this test had been subjected to much less pre- min. When the pigs were removed after 4 to 6 tin, they
bminary thermal stress. One pig died shortly after the test; it were all breathing normally, their color was nomlal, and
had been located immediately beside the fuel cell and had they acted normaUy in the field pen. When they were sacri-
been drenched with hot fuel AN the otier pigs were moder- fiq there was some indication of breathing tract injury,
ately subdued after the test. The pig that died bad third- but none that was life threatening (Ref. 27). This test indi-
&gree burns on the ears and second-degree bums on its cated that because the hatcttes were blown open, the veruila-
snout and exhibited burns and damage to its breathing tract. tion was much more adequate.
None of the others had any skin bums or discolored lar- In the third test the upper hatches were open, and a total
ynxes (Ref. 25). This test was much less severe than the ear- of 8 pigs were suspended within the vehicle or over open
lier test primarily because the pigs were not subjected to hatches. Upon detonation of the charge, the ahmtinum sheet
severe thermal conditions before the tes~ and only the pig on which the grid was mounted came loose and was thrown
subjected to extreme conditions, including breathing some- to the deck when 8 of 10 bolts securing it to the wall
thing extremely injurious, such as hot fuel, died. sheared. This situation permitted gasoline to spray into the
The next test differed from the two er@er in that the troop compartment the aiuminum sheet had acted as a baf-

0
>1’
vehicle was being towed at 24 krtth (15 mph). In this test
the ambient temperature was O to 3°C (32 to 37’3F),and the
DF-2 had been heated to 57 A 3°C (135 k 5°F) prior to firing
fle and trapped much of the gasoline spray in the other tests.
The extinguishant bottle mounted on that sheet discharged,
but the flow of HaIon was not effective, i.e., the Halon
flowed out between the aluminum sheet and the deck Also
the charge. Again a very large fire was ignite~ it was extin-
the personnel door in the ramp came open and permitted the
guished in approximately 125 ms. All the pigs .sumived but
Halon to exit the troop compartmen~ llte initial fire was
appeared moderately subdued. None of the pigs were
extinguished in 892 rns but reignited after 4s. The tire was
burned. UporI sacrifice, none exhibited any life-threatening
reextinguished and then reignited in 2s. This fire was again
breathing tract damage (Ref. 26). T%istest indicated that if a
extinguished but reignited in 1 s. Neither automatic nor
fire is quickly extinguish- it should be survivable by
manual systems were abie to extinguish this fire; it had to be
unprotected beings, but it also indicated that the beings
extinguished by APO firemen with portable extinguishers
probably would not be capable of performing their duties.
approximately 1 1/2 min after the charge detonation. Fhe of
the pigs dietl and the other three were moribund. Six had up
5-2=3 Test of Gasoline-Fueled M113 AFCS
to fourth-degree burns* over 90% of their bodies. The other
The AFE.S usd was basically the same as the one for the two were also badly burned. All suffered extreme injury of
dieseMuekd Ml 13A.1(Ref. 25). In the four tests the 22710 the respirauny tract (Ref. 27). This test demonstrated that
265 L (60 to 70 gal) of gasoline were heated to 35 * 3°C (95 the Halon extinguishant had to be contained and circulate
A 50F) before the test The shaped charge used in each test within the compartment to be effective.
was the M28A2 warhead. ‘l%efoutth test was a repeat of the third. This time, how-
In the tit test six pigs had their feet lashed together and ever, the bobs holding the aluminum sheet with the wire
were laid on the deck within the vehicle. The upper hatches grid and extinguishing bottle did not shear. The AFES extin-
and ramp door were closed. The internal fire was extin- guished the fire in 100 ms. The six pigs, whose average
guished in 212 ms. ‘llte APO fuemen extinguished the mass was 15 kg (weight of 33 lb), were removed horn the
external fire 3.5 min after the test. ‘he hatches were opened vehicle in approximately 6 min. The cable suspending two
5 min after detonation. The pigs, whose average mass was pigs was severed by the shaped-charge je~ so the pigs
25 kg (weight of 55 lb), were removed 5 to 8 min later. ‘l&y dropped onto the deck. These pigs were welkturated with

0 ‘; were all bhisk tithing at the mouth, and gasping for air
@cf. 27). The veterinarian who was handling these pigs
later described them as being “shell shocked” (Ref. 61).
*Founh-degreeburnsare thosein whichthe skin is chimed and the
bum extendsintothe muscleand sometimesthe bone.

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MIL-HDBK-684

gasoline. One of these two pigs had breathed gasoline and

lWJ
was dead when removed. The other pig that had been
dropped was prostrate, unconscious, had a first-degree burn,
I
F—————— ShulterCjmn
-.-_.._<._ ‘7 - lwl
and bad difficulty breathing when removed. The other six
ml
pigs had no skin burns, and three of them suffered some res- I

piratory tract injury. None of the seven surviving pigs’sgf-

fered injuries that would have proved fatal (Ref. 27). This psoo
~estraises the question of whether being on me floor, being
dumped into the gasoline spray, or breathing the gasoline
spray is the most hazardous. The fast fire out time was not
the deciding factor.

5-2.2.3.4 Tests of Aircrew Uniform Materials 200

Several series of tests were performed by the US Army

Aeromedical Research Laboratory in the late 1960s and the ‘--- Nom&/Sandwd

1970s. These tests were to determine the protection cloti-!ing o 2 4 6 B 10

!
provided the crewmen from a JP-4 fie in a crashed hel~cop- Time, s

ter (Refs. 35,62, and 63). The heat source used in these tests
was a modified gun-type conversion oil burner burning JP- Figure 5-3. Temperature Traces for 7-s Expo-
4. The device delivered 159 * 6 kW/m2” (14 * 0.5 Btu/ sure T@ts (Ref. 62)
h 2.s), which simulates the worst credible ihermal environ-
clothing or ,Ibetweenthe clothing and the skin, should pro-
ment in a helicopter crash fire (Ref. 62). This amount of
vide much }etter’ protection from flame than “formfitting”
heat would also simulate a fuel fire within a well-ventila~d
clothing. A ~rneasureof the protection afforded by the most
combat vehicle.
lire-resiN.an~fabrics is shown on Fig. 5-4. For each fabric or
A shutter covering six holes in an insulated plate was
fabric and cotton T-shirt combination listed, the gross bum
used to control bum location and duration. Each hole pro-
grade for a~5-s exposure to JP-4 flame is shown (Ref. 35).
vided a single skin burn specimen. These holes could be left
The control specimen Groups 3 and 4 provide a measure of
empty to provide a baseline bum, could contain fabric spec- a
the protecti~n afforded by the cotton T-shirt alone. Note that
imens, or could contain a heat flux sensor (Ref. 35). Many the multiple layers of loose-fitting clothing provide’ the best
fabric combinations were tested including Nomex@, poly- protection.
benzimidazole (PBI), an exper@ental high-temperature Because !hey are hotter, solid gun propellant fires would
polymer (HT4), and cotton. be even more hazardous, as indicated by an incident in Iraq
In one series of tests (Ref. 62), the fabric samples were
held against the pig’s skin to preclude an air gap between 16
r
fabric layers or fabric and skin. A thermocouple was
emplaced between the skin and the fabric at the center of
each skin bum specimen. The thermocouple sensed the sur- A
face temperature of the skin for three different exposure A A A A
time intervals. I%g. 5-3 shows the skin temperature versus A b
o 0
time for one of these tests. Note that the temperature trace .e o
$
for the single-layer Nomex Q follows that for the unpro-
tected specimen but lags it by 1.9 s. This lag is the ‘time
required for the approximately 1500”C (2732”F) JI?-4 flame A Gmr$
1:
%7@ @IW
to remove, at least partially, the single layer of Nomex@.
After removal of the single layer of Nomex@fabric, the skin
heated at the same rate as did the unprotected.skin (Ref. 62).
These tests demonstrated that a.single layer of even a highly
1“ 4’

1
!,

I
A GroI@2: Sie

I
Layer/Space
O GmW 3 Skrgle LaywT.Shiri
● Groi.p 4: Siie LayarlT-Shir@ace

I I t
omtm4 Naw? NewWeave Palytemim&mM Ei@Iw@I
fire-resistant fabric will not resist flames from a hydrocar- ..lmmd Nanm?kmid H@h-Tnmpmiura
bon tire for more than approximately 1.0 to 2.0 s. These P+mfr (HT41

y. tjam#.4 + Fabric
tests also showed that two’layers of material, particularly a .
fire-resistant layer over a standard cotton layer, would pro-
vide superior protection. Figure 5-!. Mean Clinical (Gross) Grade for
Later tests indicated that “loose-fitting” clothing, i.e., Each @gh-Temperature Fabric and/or Con-
9
there is an air gap between the outer clothing and the inner figurat~on (Ref. 35)

5-16 (

I
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MIL-HDBK-684
in which a ’172 MBT hit an M2A2 BFV and initiated pro- Three of the behind-armor casualties suffered burns ffom

o
!,
pellant which in turn ignited the combat vehicle crewman
(CVC) uniform of a trooper (Refs. 64 and 65). This uniform
did protect the crewman from receiving fatal burns.
diesel fuel fires, and one soldier was splattered with white
phosphorous particles. Five casualties were caused by
shoclq blw or flash. Diesel fuel that splattered the person-
nel and burned orI their clothing caused two of the burn
5-2.2.3.5 Overall Evaluation of These Ma! casualties; these two men were not evacuated beyond the
Tests clearing station (DAN 672). Another bum casualty was
‘fhese tests indicate that a shortduration hydrocarbon fire caused by a vehicle that was hit by a shaped charge on the
extinguished by Halon 1301 is not lethal as long as the ani- right side, and the jet passed through the troop cmnpamnent
mals are removed from the vehicles quickly. Thus, if the before impacting the fuel tank on the left side (DAN 381).
personnel evacuate a vehicle rapidly, the fire and extinguis- One burn casualty was in the 81-mrn mortar carrier, M125,
hant by-products may not be lethal or incapacitating. This in which tie RN-2 shapeddarge jet passed though two
white phosphorus (lVP) projectiles. The gunner, who was
evacuation won14 however, expose the crewmen to small
arms and artillery fire. sleeping in the vehicle, was burned badly by the white phos-
Orte test showed that ifanimrds remain within a buttoned- phorus (DAN 301).
up combat vehicle for five or six minutes, they will be inca- Most of the fiash or blast casualties were caused by the
pable of effective action. This result indicates that even if detonation of the shaped-charge warhea4 not from any
crewmen are not burned within combat vehicles protected internal explosion; none of th~ casualties were caused by
by a HaIon 1301 AFES, they will probably succumb to exploding stowed ammunition. None of the casualties were
‘%moke inhalatioit” (1) if they do not evacuate or (2) if the caused by i,nhalktg combustion products, sprayed fil, or
products of combustion are not purged either by ventilm.ion the fire extinguishan~ COZ. None of these vehicles were
buttoneckqx all had their hatches open when hit by the
or by extinguishant spray flushing. Soldiers cannot effec-
tively operate their equipment under the conditions that pre- shaped-charge warhead.
vailed in these tests. This scenario illustrates the need for
5-2.2.42 Ca.sunkies in MBT3 M48A3
either a highly effective ventilation system or an extin-
guisher system that can flush noxious fumes out of the air. The M48A3 MBT was diesel fi,teledand had a manually

o (A means to flush smoke and noxious gases out of the air is

described in subpar. 7-2.3.1. Vehicle designs that preclude
the burning of great quantities of fuel and/or hydraulic flu-
activate4 fixed fire extinguisher system (FFES), which used
COa, in the engine compartmen~ The crew compartment
had two portable CO* fire extinguishers. Crewmen of the
ids within the occupied compartments are covered in Chap- M48 were trained to evacuate their vehicle when it was hit
Ier 4.) and stopped. They were also trained to take their personal
?M fabric tests indicated that multdayers of loose-fitting weapons and the coaxial machine gun, defend the vehicle
cJo?hing are best and that we do not have a truly llreproof from further attack and assist in the evacuation of the vehi-
fabric in use in the Army. cle. ‘fhey were trained not to stay within the vehicle because
it would probably be subject to additional hits (Ref. 67).
The BDARP database for SEA had a total of 19 iacidents
5-224 Combat Data from Southeast Asia
in which shaped-charge warheads hit MBTs h448A3, and 32
There is a very limited database available from Southeast
casualties resulted. Tlte hatches were open in 17 of those
Asia on tire casualties from combat vehicles hit by shaped- incidents, the driver’s hatch was cIosed in one me vehicle
charge warheads. ‘llte data available in the BDARP data- was parked for the night.), and the other was unknown.
base at the Survivability Information and Analysis Center When the hatches were open, the commander and loader
(SURVIAC) are described in subpar. 4-1.2. were usually standing with their upper torsos exposed, and
the driver usualiy had his head exposed. Nine (28%) of the
5-224.1 Casualties in ACAVS and Other APC casualties were thus exposed aad were hit by fkagments or
Ml13 vehicles bullets. Twenty (62.5%) of the txtsualties were caused by
A review of the 47 reported incidents involving 43 behind-armor effects. l%e other three casualties were due to
armored cavalry assault vehicles (ACAVS), 2 mortar cami- evacuating the M48A3 after two tear gas grenades were
ers (an MI(M and an ML25), 1 cargo carrier M548, and 1 punctured by a shaped-charge jet (described in subpar. 4-
M113A1 in which 78 casualties resulted indicated that 21 6.4.3). One soldier injured a leg afier running ofl the vehi-
casualties were caused by fragments or small arms bullets cl~ the other two were shot by small arms.

.,
impacting personnel exposed in open hatches or on top of At least 13 of the behind-armor casualties were due to the
the vehicles, 53 casualties were caused by impacts of jets or je~ span, or splash. In one incident (DAN 157) the jet hit a

0 span or by other behind-armor effects, and 4 casualties were

dismounted troops near the vehicle (Ref. 66). Time inci-
dents are tiled by document acquisition number (DAN).
90-mm cartridge case and ignited the propellant. One man
was killed in the resulting explosion, and another was
burned and bit by S@~.

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MIL-HDBK-684

-5-2.2.4.3 Casualties in ARfAAV M551 5-2.2.4.4 Evaluation of SEA Armored Vehicle

The armored reconnaissance/airborne assault vehicle Fire Casualties
(M2/AAV) M551 is a diesel-fueled alu~num armored 9
The fire casualties from all three vehicle types were com-
vehicle. The ammunition cartridges used have combustible pared to the animaI caswilties in the tests described in sub-
cases and are loaded with M26 propellant. The M551 is p~. 5-2.2.; to see whether the test results could be
divided into three compartments to accommodate the driver, validated. During evaluation of these results, it should be
the rest of the crew, and the engine. A fire barrier is located noted that tie M551 had Halon 1301 and the M48A3 and
between the crew and the engine compartment. No fire M 113A1 ACAV had COZ extinguishers, whereas all of the
warning or sensing system is. provided, but “both the crew animal tes~ were with HaIon 1301.
compartment and the engine compartment have a dedicated There were ,very few incidents in SEA”in which crewmen
FFES. The FFES in the crew compartment has one 3.6-kg were subjected to hydrocarbon fuel fires within vehicles. In
(8-lb) EIalon 1301 bottle that is manually activated by pull- all of those incidents the crewmen evacuated the vehicles
ing a handle located on the right side of the turret. The very quickly, probably within seconds. In all of the animal
engine compartment has a 1.47-kg (3.25-lb) Halon bottle tests the animals remained within the vehicles for at least 5
with one activation handle near the driver and a second han- min. ‘Ihus the animals had much more time to breathe nox-
dle on the exterior of the vehicle. There is one portable ious combustion products and vapors than the humans. In
1.25-kg (2.75-lb) Halon fire extinguisher in the driver’s almost all of the incidents in SEA, the vehicles were well-
compartment. Fuel is carried in tliree cells. Two are located ventilated, ~.e.j the hatches were open and usually the men
on the right sponson in both the crew and engine compart- were brea~g outside air. Most of the pigs were breathing
ments, and the third is across the engine compartment adja- air from w~thin the vehicle. The men did not suffer exces-
cent to the fire wall that protects the crew compartment. sive heat input in the vast majority of incidents, nor did they
There were 16 incidents in the BDARP database in which succumb t~ smoke inhalation or air passage edema. Some
M551s were hit by shaped-charge warheads. There were 22 pigs did. If~~ vehicles had been buttoned up in SEA, how-
ever, there ~~good reason to believe the men could have suf-
casualties in these incidents. Six (27%) of these casualties
fered the same breathing passage injuries as the pigs.
were personnel exposed in hatches or on top of the vehicles,
Therefore, although the combat incidents do not validate the
four of whom were hit by fragments from the warhead cas-
test data, they do not contradict it. The animal tests illustrate
ings and two were injured by the blast or flash of the war-
the import~ce of ventilation. @
head detonation. T’heother 16 casualties (73%) were caused
There were no automatic fire-extinguishing systems in
by behind-mmor”effects. Eight were caused by bums and/or
SEA. The incident reported in DAN 1839 with an M48A3
blast effects from explosion of stowed cartridges hit by
MBT was one in which the shaped-charge jet probably hit
shaped-charge jets, and the other eight were caused by
one or more cartridges in a ready rack and ignited the pro-
impacts of spail or splash from the jet or direct impact of the
@lant. This scenario could cause the burns experienced by
jet itself. The hatches were open in 14 incidents, closed in
the crewmen. “The”jetprobably also penetrated the fire wall
one incident, “andwere probably open in the other incident.
between the crew and engine compartments and the right
There were two hits in the engine compartment that
fuel cell and started a fuel fire in the engine compartment
resulted in hydrocarbon fuel fires. In one (DAN 1532) the
(Ref. 67). The combination of propellant fire in the crew
FFES in the engine compartment was activated, and the fire
compartment and fuel fire in the engine compartment proba-
was successfdly extinguished by the FFES plus portable bly caused $e ammunition to bake o%, the resulting explo-
extinguishers: All four crewmen, however, evacuated the sion demolished the vehicle after the crew had evacuated.
vehicle. In the other (DAN 1879) the fire had self-extin- The commander undoubtedly had his upper torso out
guished but the crew did not realize there had been a fire through his hatch, the driver undoubtedly had part of his
until later. ~ey knew only that the engine had stopped run- shoulders out of his hatch, and the loader was probably sit-
ning. ting on the /edge of his hatch with his legs in the turret and
There were three other hits that resulted in fires. One hit his hands ?n the hatch combing. This would explain the
was in tie rear in the battery box. Electrical insulation amount an~ location of first- and second-degree burns on
“burned “md the fire self-extinguished (DAN 632). The other each, i.e., 45 Yofor the commander, 80% for the driver, and
two were into the turrets. In both incidents the crew evacu- hands and legs only for the loader. Also the facts that they
ate~ the fires were of electrical wiring only. In one (DAN suffered only first- and second-degree bums and did not die
670) the fire was extinguished by a crewman using the por- were probably due to the protection afforded by their uni-
table extinguisher, whereas in the other (DAN 463) the fire forms. (- uniforms were probably cotton fatigues,
self-extinguished. In none of these incidents was the crew which afforded much more protection than bare skin.) Note
reported to have breathing tract injuries. that a prop&ant flash fire can produce second-degree bums.
1! @

5-18
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III one ACAV incident the legs of two crewmen were ductive, and convective) for exposed skin in a given
sprayed with hot fuel that ignited (DAN 672), but their environment expressed by the integral of the air temperature
o clothing protected them.* This incident illustrates the pro- versus time in “C-s. l%e biological response to rhermal
tection that clothing provides. These men were returned to overload is similar to the response to sunstroke and is char-
duty horn the clearing station; therefore, their burns could acterized by the same progression of symptoms, i.e., dizxi-
not have been serious. ness, ataxia (loss of muscle coordination), disorientation,
The incidents in SEA have shown that if several propel- prostration, and ultimately death if the core tempemtttre of
lam charges ignite, the crewmen within rhe vehicle are usu- the body .is raised above its critical tempemrure. ‘l%ermal
ally 10SLwhereas those in the hatches are usually blown out overload can be correlated with a given end point biological
and may be fatally injured. If the propellant explosion is response. The predicted thermal overload value required to
tired to a single charge, the crewmen are usually burned. produce prostration in 50% of an exposed population within
Since no ftre-extinguishing system, except one that floods 2 min is approximately 16,000 to 18,000 ‘C.s when the
water directly on the burning propellant grains, would be exposure time is 30s or less (Ref. 37).
able to preclude the explosion, the only vehicle design that The phenomenon of thermal overioad has been reported
could protect the occupants would be one in which the pro- in human subjects and was obsenwd in tests involving pigs,
pellant is compartmented away from the occupants as is which were conducted during evaluation of the M9-7
done in the Ml MBT. flamethrower and the M202 multishot flame weapon (Ref.
37).* In the first 30s of exposure to flame born two M235
5-2,3 JIUiMAN INCAPACITATION warheads fired from an M202 flame weapon at a tw~sec-
T%e criteria for human incapacitation due to thermal ond interval, heat energy was provided at a rate of approxi-
injury are taken horn Ref. 1. These criteria have been mately 9500°C.s, but no pigs collapsed. Four rounds fkom
approved by the Surgeon General of the &my and are the M202 flame weapon provided approximately
intended to be used to evaluate injury effects in live-fire 16,000”C.S ffom which 54% of the pigs .collap~ and in
tests of armored vehicles. In general, these criteria are to another test the M9-7 flamethrower provided in excess of
establish the potential for second-degree burns. If that 20,000”C.S from which all the pigs collapsed (Ref. 37).
pxential exists, the thermal injury criteria given in Edge- mere are limiting combinations of temperature and time
,!’ wood Arsenal Publication EB-SP-7601 1-7 (Ref. 37) should that provide a critical constant value, expressed as “C.s, that
o be wed. ‘l%e second-degree burn criterion is given in sub is required to produce collapse in 50% of the exposed popu-
p= 5-2.2.2 lation. This appears to b at a level slightly in excess of
If short-temn diversionary effects, flash blindness, psy- 18,000°C.s for the asymptote that delineates the high-tem-
chological effects, and the effects of oxygen depletion and perature case for which the exposure time is 30s or less.
toxic by-products are excluded, human incapacitation tim
thermal events can be predicted by three methods: thermal 5-2.3.2 heal Site Disability
overload, local site disabiity, and systemic disability. l%ese Incapacitation can be estimated fkom the disability or
methods am described in the subparagraphs that follow. dysfunction of specific sites of the body that have been
burned. The terms “disability” and “dysfunction” refer to
S-2.3.1 Thermal Overload the decrease in functional capacity of a given local site.
Because heat input into a human body is difiicttk to quan- Nineteen nationally and internationally known surgeons
tify in a tes~ investigators have developed a means to esti- who specialize in the treatment of burn casualties and 22
mate injury due to thermal overload by relating the thermal surgical residents at four major burn centers were inter-
injury to the integral of the exposure of bare skin to heated viewed to derive local site and systemic disability estimates
air. Personnel at the former US Biomedical Laboratory, for humans (Ref. 37). These estimates were based upon the
Edgewood Arsenal, established that approximately 99% premise that soldiers are fully motivated and will perform
incapacitation of approximately 99’% of the population can theix duties as long as they are physically able. Human dis-
be achieved in 2 min or less through the phenomenon ability estimaux for seven postburn time periods ranging
known as Wtermal overload”. In this sense, thermal over- front 30 s to 5 days were determined, and mission-related
load is the accumulation of thermal events (radiative, con- incapacitation levels were calculated. Disability estimates
for only two time periods-30 s to 5 min and less than 5
*Thetwo men were the right and left machinegunners.IIIey were

left
rear
observingwhile their vehiclewas bmking up, so their heads were - M9-7 ftsmethrower burned thickened gasoline, and the
up through the open cargo hatch.The RX jet passedthroughthe M202 flame Wqmn burned thickened rnethytahmlinum(TEA).

o
surfaceof the vehicleand exited throughthe fuei cell. As ‘he flame temperatureof neat gasoline is approximately743Z
,, thejet exited, hot diesel tiel spmyedon the legs of the two men. (1369T) (Ref. 68), and the flame temperamre of neat TEA is
‘fhe fiel and cloth ignk~ but the trouser legs srill protectedthe approximately1204°C(22WF) (Ref. 69). (The flametempemmre
menfrom the heat and the. of thickenedfueiis less than that of the neat fuel.)

5-19
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MIL-HDBK-684

min to 30 rein-were prepared. The less-than-30-s time and then cause second- and third-degree burns on the skin
period normally used in antipersonnel evaluation was o@- underneath (Ref. 72).
ted since it is believed that soldiers who receive burns Also pho~phorus oxide fumes are very poisonous. The
would be made partially or completely ineffective by the maximum allowable concentration for an 8-h exposure is
concomitant diversionary effects for a short time period. * 0:1 mg/m3 $& 72).
The exact length of this time period would depend upon
several factors including the type of flame source, proximity 5-2.3.4.2 ~Oxygen Depletion and Toxic By-Prod-
to the affected area, and the military stress situation. The ‘Ucts
two time periods are equivalent to the assault and defense There is evidence of effects from oxygen depletion and/or
stress situations used to ewiluate kinetic energy missiles, as toxic by-products upon the animals in the test described in
‘described ih Refs. 13 and 71. subpar. 5-2.2.3.3, which was the only test in which the
Two interrelated methods used to predict the degree of hatches remhed closed and the animals were not anesthe-
incapacitation or the probability of incapacitation given heat tized. This test illustrates the importance of ventilation in
exposure— P(l\ H)-values ascribable to burns of the
preventing ~ertnal injuries due to smoke inhalation. This
human body have been developed (Ref. 37]. If it is known
subject is discussed more fully in par. 5-6.
with some degree of certainty that a flame or incendiary sys-
tem produces burns of specific body areas, the P( I IH) can
5-2.3.4.3 ~Flash Blindness
be calct,dated by an equation that, allows calculation of the
reduction of the individual’s competence ‘to continue his There we~e at least two temporary casualties in SEA due
mission by a portion of the essential function of each burned to flash blin~ss. Both of these were caused by the detona-
site in a given situation and the number of sites burned. tion flash ofkhaped charges, as described in subpar. 5-5.2.4.
/
The method used to estimate the incapacitation of a fully
motivated soldier when a flame or incendiary system pro- 5-2.3.5 Ability of Dynamically Launched Flame
duces burns of specific body areas is described in Ref. 37. ~d Incendiary Agents to Produce Burns
There are~several methods by which flame or incendiary
5-2.3;3 Systemic Disability agents can $e used against combat vehicles and their crews.
Incapacitation can also be estimated froti known sys- One of these.is by use of flamethrowers, the type that spurts
temic responses to bums that exceed the critical percentage a btirning liquid jet and the type that projects a warhead
of the body surface that must be burned to initiate these sys- which bursts and spews out a burning liquid. There are also
temic responses. land mines @at contain a combustible liquid and a propel-
If it is known or assumed that a flame or incendiary sys- ling charge plus an igniter near the open end, which can be
tem will provide randomization of the burned areas of the observer in@ated when an appropriate target enters the
body, a system to prorate these effects is provided as a rela- lethal area of the device. These flame or incendiary weapons
. tionship of percentage of body area burned versus P(I1 H), (and Molotov cocktails) Are effective only against exposed
“which for systemic effects is the incapacitation fraction combat ve~cle crewmen or against other crewmen if the
described in Ref. 37. flame or incendiary can enter an open hatch. The burning
incendiary rpust contact exposed personnel or enter an open
5-2.3.4 other Thermal Effects hatch or grill to affect crewmen or the vehicle (Ref. 69).
5-2.3.4.1 White Phosphorus Burns During ~ Korean conflict there were attempts to use
aerial-delivered external aircraft fuel cells containing
These thermal injury estimates are not valid for est@at-
napalm agdinst North Korean T-34/85* tanks. The tanks
ing disability or incapacitation produced by WP burns,
protected their crew when the hatches were closed, and they
which, are more disabling than thermal burns in general
could be dr@en out of the napalm, which was burning on
(Ref. 37).
the ground. @ one test napalm had to burn on a stationmy
White or yellow phosphorus is pyrophoric. Its autoigni-
T34/85 tank for over half an hour before crew members
tion temperature in air is 30°C (86CF). On bare skin WP
would have ~beenseriously affected (Ref. 73).
droplets usually cause third-degree burns. On clothed tar-
gets WP droplets tend to permeate through the cloth, char it, Cannon ~lcan fire white-phosphorus-filled projectiles
against combat vehicles, but again, unless the personnel are
*Thisbelief is counterto the experienceof a youngsecondlieuten- exposed or the white phosphorus particles enter through an
ant who was severelyburned when his M4Ltankwas hit by a pan- I
zerfaust in 1944. He evacuated hk tank, attempted to evade *The origin~ T34 tank mounted a 76.2-mm gun. Since this 76,2-
capture, was capturedand marchedto a prisonerof war stockade, mm gun could defeat German Panther tanks only at close range,
but had not realizedthat he was burned until the interrogatorsent the Russians~modifiedthe T34 to take an 85-nun gun in late 1943.
hlm to an aid stationwithoutinterrogatinghim becausehe was so This newer ~!ersionof the T34 was called the T34/85; the older
badly burned (Ref. 70). versionwas called the T34176.
I

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MIL-HDBK-684

open imtch, the persomel will probably not be affected. The 5-3 EM? DAMAGE
white phosphorus can ignite exposed combustibles and is
O
r ‘;
particularity effective when exposed light gage fuel cells
have been psmctured (Refs. 74 and 75).
Current doctrine includes the use of the CVC helmet for
all combat vehicle crew members. A panei of blast experts
estimated that rupture of the crew’s eardrum would be
All incendituy devices can ignite combustible items on unlikely with the standard use of these helmets (Ref. 76).
the exterior of the vehicle, but the incendiaries seldom burn The panel fitrther estimated that eardrum rupture should not
long enough on the vehicle to affect the personnel within. be considered incapacitating.
The key to the protection afforded by the combat vehicies is Most ruptured eardrums can heal-the membrane knits
that the flame or incendiary cannot readily enter the crew back together-in two to four weeks if none of the mem-
compartrnenL and the fire does not last long enough to brane is tom out (Ref. 77). On the other hand research labo-
transfer heat through the vehicle hull. Also the incendiaries ratory personnel in informal discussions with field forces
do not burn long enough to consume all available oxygen in representatives have established that to be able to function
and around the vehicle, and the vehicle can usualiy be in combat activities, soldiers must not only be able to move
driven away from the burning incendiary. Ignition of com- and operate weapons but must also be able to see, hear,
bustibles stowed on the exterior of the vehicie extend the think, and communicate with others (Ref. 71). Titus injury
burn time. to the ears thaKaffects hearing &grades the soldier’s ability
to accomplish his mission.
5-2.3.6 I%ychologkxd Effects
Therefore, it is advisable to review briefly tbe availabIe
~ insight into the psychological effects of thenml information on hearing loss for biasts impinging on immans.
weapons was obtained by examining and analyzing inter-
Some crew members ignore instructions and fail to wear
views of burn casualties, repotts of firebomb incidents, and heimets with ear protection, and some passengers may not
interviews of military personnel concerning the effwtive- be equipped with CVC helmets.
ness of the current use of flame weapons. All of rhese
sources show trends and/or personal impressions, but stone
5-3.1 THE EAR
provide a quantitative evaluation technique (Ref. 37). Per-
sonnel will norxrd.ly move away from fire. The human ear, shown on Fig. 5-5, is divided into the
external, middle, and inner ear.

o 5-2.3.7 Quaiity of Estimates

‘Ihe data presented represent a considerabk amount of
detailed Laboratory and field work in support of the disabil-
Sound frequencies of 20 to 20,000 Hz am audible to
humans, but the greatest sensitivity is in the range of 1000
to 3000 Hz. The ideai threshold of hearing is shown on Fig.
5-6(A). ‘I%eaudiometer test shows a higher threshold than
ity and incapacitation estimates. Nevertheless, the link
between either animal data or anecdotal reporis of human the ideai due to test conditions and human response deiays.
The eardrum can respond to pressure leveis as low as
exposures and actual field performanceis tenuousor nonex-
2.0265 x 10-s Pa (0.2 billionth atm), and the malieus head
istent. In the reports reviewed on this subjecL no exampies
were found of formal attempts to extrapolate performance can move to its maximum displacement in approximately
data quantitatively from animals to man. Ind~ there are 25 ms (Ref. 78).
very little performance data of any description presented. It The moving parts of the ear are nearly critically damped;
appears that the investigators whose work was reviewed therefore, the eardrum stops moving almost as quickly as
adopted a very crude measure, e.g., the number of pigs liv- Maws
Semidmlpr
C.ma&
ing afier a tem to the task of predicdng disabllty and inca- *

pacitation. References to bodies of expert opinion are

rsoticeably lacking in descriptions of how the conclusions
were derived. No mention is made of formal procedures to
remove bias fiwm the panel that polled results; conse~
quently, the recommendations must be questioned on that
basis as well as on the fimdamentai adequacy of the data
considered.
llte impossibility of doing controlled observations in
hmuans suggests the need for behavioral observations in
primate models, but no such observations are described. ‘Ile
investigators appear to have focused on quantification of
certain heat injuries rather than on considemtion of the

0 totality of physiological and pSyChOIO@Xd StrtXSeSiMpOSed

on humans exposed to fire. ‘lb results therefore cannot be
expected to pmiict actual combat experience accurately.
Reprintedwith pesmissiomCopysighte by Appleton& Lange.

Figure 5-5. The Human Ear (R% 41)

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MIL-HDBK-684 j
I

the sound wave stops. The middle ear also contains two pressurized \slowly to rupture. The ears were characterized
small skeletal muscles that contract when exposed to loud by sex and age of individual, whether right or left, and con-
sounds and thus prevent strong sound waves from exces- dition, i.e., ilnormal or evidence of infection or damage, @
sively stimulating the auditory receptors (Ref. 41). Very w~ch woul~ have resulted in a weakening or strengthening.
strong sounds, however, can also rupture the eardrum. Zalewski found that the eardrums of men and women rup-
In addition to being conducted through these membrames tured at es~kntially the same pressure and there was little
and ossicles, sound can be conducted by vibrations of the difference ~tween the rupture pressure of right and left ear-
secondary tyrnpanic membrane and by transmission through drums. He @so found that accidents, sicknesses, or infec-
the bones of the head. This latter mechanism is involved in tions can weaken the eardrums. The most significant
transmission of extremely “loudsounds. difference in ~pture characteristics is due to age, as is
The external ear amplifies the overpressure of the sound shown on Fig. 5-6(B): The mean rupture pressure of normal
wave by approximately 20% and detects the location of the
source of sound (Ref. 41). Ruptufe of the eardrum (or tym-
panic membrane), which separates the external ear from the
middle ear, has captured most of the attention of clinicians,
although it is not the most severe type of ear injury. The ear-
drum and ossicles of the middle ear transfer acoustical
enerb~ from the external ear to the inner ear where mechan-
ical energy is finally converted into the electrical energy of
’40-
100

m
-a
the nerve impulse. The middle ear is an impedance-match- _-
~
ing device as well as an amplification stage. The middle ear
-3
contains two dampers, i.e., the stipedes muscle and associ- >
.=
ated ligaments, which limit the vibration of the stapes when m U
g
subjected’ to intense signals, and the tenser tympani muscle & ofHearing, Audiometer
?hreshold
and its adjoining ligaments, which limit the vibration of the ~
eardrum. The first damper is the more important. These I
dampers have a reflex time of approximately 0.005 to 0.01
S, which is longer than “fast” rising air blasts. The manner
in which the malleus and incus are linked allows far more o- “
resistance to inward displacement than to outward displace- 10 “ Id Id 104 2X104
ment. If the eardrum ruptures, however, after inward, dis- Frequency,Hz
placement during the positive phase of loading of the blast
wave, the malleus and incus we less likely to displace as far
outward during the negative phase of loading of the blast (A) Audibility
CuryeforMan(Ref.41)
wave as they would if the eardrum remained intact. The Reprintedwi;~permission.CopyrightQby Appleton& Lange.
maximum overpressure and its rise time control the charac-
teristics of the negative phase and are therefore of prime
importance. In this case, eardrum rupture could be benefi-
cial. The ear&urn would rupture before the round window,
which could result in the release of the penlymph fluid, or
the oval window, which could result in the release of the
same fluid. Either of these eventualities would be much
more severe than the rupture of the eardrum. When the ear
bleeds, the probable sources of the blood ‘are the eardrum
and/or the wall of the external auditory canal. Thus rupture
of the eardrum becomes a good measure of serious ear &un-
age.
t
5-3.2 EAR IN~L.JRY LEVELS ‘“o~
so 70 80
5-3.2.1 Eardrum Rupture Age,
yr

The quasi-static eardrum mpture pressure of man was (B)Eardrum

RuptureOverpressureVersusAge (Ret79)
determined by Dr. 1“.Zalewski in Lemberg, Galicia, Austria-
Hungary, circa 1906 (Ref. 79). Complete ears from fresh Figure 5-6. Audibtity Curve and Eardrum
cadavers were removed and mounted in a fixture and then Ruptm% Pressure for Man

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specimens for each decade is lumped at the mid-age, except young adult human can suffer without permanent injury

o for the two newborn infants. ‘Ikse data are from 59 male
and 52 female subjects, all with normal eardrums. For nor-
mal eardrum 10.8% ruptured at an overpressure less rhan
(Ref. 80).
In geneml, intermittent exposure to noise requires a
higher noise level to produce ‘ITS than would continuous
101.4 kPa (1 atm), 65.8% at overpressures between 101.4 to expostne Wuh impulse noise, the higher the peak pressure,
202.7 I@a (1 to 2 M@, and 23.4% at overpressures above the greater the probability of ‘ITS (Ref. 80). A trace of
202.7 kPa (2 atm). Tbe least rupture overpressure was 37.3 impulsive sound versus time is shown on Fig. 5-7. Ref. 81
kRz and the greatesg 304.1 kPa. provides two techniques for evaluation of sound pressure.
T%esimpler of the two techniques is to consider the princi-
5-3.22 Temporary Threshold Shift pal sound peak only, which is the ‘~ duration technique.
When a combat vehicle is bit by a ballistic projectile that T%e more complex technique is to consider all sound
is capable of igniting a fire, both the impact and the subse- impulses with peak magnitudes within 20 dB of the princi-
quent combustion are accompanied by sound Airborne pal sound peak leve~, wbicb is the ‘%” dumtion technique.
sound is a rapid variation in ambient atmospheric pessure. For an “A” dumtion evaluation, a point representing the
Noise is unwanted sound. Noise can cause temporary or principal positive peak pressure and the “A” duration time,
permanent loss of heming, can adversely affect the ability to which are taken .fiom a trace similar to that shown on F@. 5-
communicate, can distract a person, and in extreme cases 7, is plotted on the graph in Fig. 5-8. If the point so plotted
can adversely tiect people’s physiological processes (Ref. is to the left of or below “A” Duration Curve i on Fig. 5-8,
80). the TI’S bas not been reached For an explanation of the
Steady state noise is a periodic or random variation in more complex “B” duration technique, see Ref. 81.
atmospheric pressure that has a duration in excess of one Curve 1 shown on Fig. 5-8 is the lTS for 75% of young
second. Impulse noise is a short burst of acoustic energy adults exposed to side-on impulsive sound pressure that is
consisting of either a single impulse or a series of impulses. repeated at a rate between 6 and 30 impulses per minute for
The amplitude of sound is expressed as a sound pressure a total of 100 impulses (Ref. 82). ‘flux are the assumptions
level SPL and is measured in decibels (dB) (Ref. 80). SPL that are normally used for bearing protection design, but
can be calculated from they are not used for vulnerability reduction design. Coles et

0
al in Ref. 82 provide advice by which the TTS can be modi-
‘, fied to represent a more desirable set of assumptions. The
SPL = 20 log(p/PoJ, dB (5-6) tnce oflTS shown as Cuwe 1 on Fig. 5-8 can be modified
where to represent the other assumptions that follow
p = sound pressure being measured, Pa (Win? ) 1. To have the lTS for 90T0 rather than 75% of the
P = reference pressure, usually 20 ~Pa exposed population, Coles et al recommend lowering the
‘s (2.9x 10-9 lb/irt~ ). curve by 10 dB, i.e., Curve 2 represents 90% rather than
75% of population coverage. .
The sensitivity of human hearing is established with an 2. Because the crew of a combat vehicle would proba-
audiometer, which establishes the threshold sound level in bly be subjected to one, two, or three hits rather than 100
dll for selected frequencies for each ear. The degradation of over 10 to 17 min. the TTS curve should be raised 10 dB
hearing sensitivity can be attributed to some diseases, to from Curve 2. Curve 3, which coincides with Curve 1, rep-
aging, and/or to exposure to excessive noise. Exposure to resents ‘ITS for 90% of population coverage and the reduc-
noise cart cause a lessening of baseline hearing sensitivity tion in number of primary impulses received from 100 to
tit is either temporary-the hearing sensitivity can recover fewer than 6.
in hours or days-or is permanent. A temporary change in 3. If the TTS were to be for ears receiving reflected or
the hearing threshold temporaty threshold shift (TM), can normal stagnation pressure instead of side-on pressure, the
k established by use of an audiometer. When a current test curve would have to be lowered 5 dB. Therefore, Curve 4
is compared to the audiometer test results in a soldier’s represents the ITS for normal rather than side-on pressure.
medical file, the differeme provides a measure of any See Fig. 5-9 for bead orientation. Fig. 5-8 presents the TTS
change in hearing sensitivity. Thus TI’S can be used as a of 90% of young adults, who are most likely to be combat
limitfor the maximum allowable noise (Ref. 80) and is a vehicle crewmen and who thus could be subjected to six or
useful design tool. fewer principal pressure pulses in a few minutes. Curve 3
A hearing loss that is not recoverable with time is a per- should be used if their heads are oriented for side-on pres-
manent threshold shift (P’RS). llte exact relationship sure, whereasCurve 4 is representative if their more vulner-
between ‘ITS and PTS bas not been established. l%is rela- able ear is oriented for normal pressure.

0 tionship should be established before programs using ‘IT’S

of human volunteem can be performed safeIy. The ‘iTS of
humans has been explored and represents the most injury a
Although the method to obtain the ‘%” duration is not
described in this handbook (Refer to Ref. 81 for that
method.), the values of the “B duration and the peak pres-

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NNL-HDBK-684

“FY Duration II ~
10.0 h

t-
7.5

T
20 dB

, I
Last Peak Above L+
/

-1 l’-”’”””ra”on
i
I B 1 s s # r’ 1 r 8 !
o 20 40 6~” 80 100
Time, ms ~
L+= tine 20 dB below the positive peak overpreasure and parallel to the baseline ~
,,
L- = reflection of L+ through the baseline

Figure 5-7. Representative Trace of Sound Pressures Showingl Both “A” anal ‘%” Durations (Ref. 81)

I
L’ JetTrajecMry
IL
,,

I
Impackd Sie
04wr WI
al Vehicb
f~kb “o o HA
[ ttt ;“$
I
i’
;!
(A} (B) (c)
Crswnrsn Crr?msn Sh& From
Facici;y FasmgJst J::”%
it
! inti
\ f
Hesds Ars \I IIar3 Fk3cakhg Lsf!Esr Raxiws
Mew From S&on Pr6ewm Nmmal(R3tlsctsq
Above; Pr6ssu!3

r (WI = %Ei.ws .9WS

Bouncing
FromChsmtsfWsllr)

Figure 5-9. Shocks From Jet to Ear Aspects

Ouration; m

Figure 5-8. Teqmary Threshold Shift Curves

(Ref. 82)
I
1,

!!
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MIL-HDBK-6a4
sure are described. The TTS associated with the “B” dura- sure wave and the given peak pressure and “A” duration

o tion is shown on Fig. 5-10. All of these curves are for the
TTS of 75% of the population receiving a number of side-
on pressure pulses daiiy. Line W is the peak pressure level
shown on Fig. 5-8. lhe resulting plots of lTS are shown on
Fig. 5-11 for both the side-on and reflected pressure loading
modes.
under which no ear protection is needed even when the
number of sound impulses is unlimited. Curve X is the ‘ITS 5-332 Eardrum Rupture Criteria
for an individual protected by either earplugs or earmuffs The eardrum mpture criteria are from Ref. 79 and are
who is subjected to 2000 impulses daily or protected by independent of pressure loading mode. The threshold for
both earplugs and earmuf% who is subjected to 40,0W eardrum rupture is 181 dB, i.e., 23.4 kPa (3.4 psig), which is
impulses daily. Curve Y is the TTS for an individual pw @ PmssW. me pressure peak for 50% probability of
tected by either earplugs or earmuffs who is subjected to eardrum rupture is 195 dB, i.e., 110.3 kPa (16 psig). These
eardrum rupture titeria are also shown on Fig. 5-11. Tlte
100 impulses daily or protected by both earplugs and ear-
titeria given on Fig. 5-11 are more usable for engineers
muffs who is subjected to 2000 impulses daily. Curve Z is
because the tneasurittg and recorthng of peak pressures and
the TTS for an individual protected by either earplugs or
the calculation and summing of impulse are well within the
earmuffk who is subjected to 5 impulses daily or protected
current state of the art of test insoumentaion.
by both earplugs and earmuffs who is subjected to 100
impulses daily. Effectively the CVC helmet is a pti of ear- 5-3.4 PRESSURE WA~S ASSOCIATED WITH
muffii.
SHAPED-CHARGE JET
Pressurewaves associated with jets horn four different
5-3.3 EAR DWI.AGE CRITERIA
shaped charges were measured with two different types of
The ear damage criteria recommended by the author of instrumentation in four programs. Ballistic Research Lab
this handbook are criteria for ‘lTS of unprotected crewmen ratory (BRL) precision 8 l-mm shaped charges were used in
for both side-on and reflected sound pulses and criteria for the first program (Ref. 83), in which side-on pressure was
the threshold of eardnm rupture. measured wirh pencil gages. Nonprecision Slam shaped
charges with trumpet liners or nonprecision 105-mm shaped
S-33.1 TTS Criteria charges with conical liners with spit-back apexes were used

0 The criteria for ‘ITS in terms of peak pressure versus time

duration is shown on Fig. 5-8 for 90% of young adulrs
in the second program (and later described in Ref. 84), in
which side-on pressure was again measured. Nonprecision
exposed to less than six impulses as Curve 3 for side-on 81-mm shaped charges from the M28A2 HEAI’ warhead
~ and as Curve 4 for reflected pressure. wete used in the third program (Ref. 10), in which side-on
These criteria can be recomputed in terms of peak pres- pressure was again measured. The M28A2 H warheads
sure versus speciiic impulse by assuming a triangular pres- were also used in the fourth program (Ref. 85), but the
i,nstrttmentation was changed so that reflected pressure was
miasured. In ali cases the pressure transducers were
installed to monitor the pressures generated by passage of
the shaped-charge jet in the chamber. The results of these
four programs show little difference among the shocks pro-
duced by the jets, especially since these jets had already
penetrated relatively light armor, i.e., 25.4 mm (1 in.) of alu-
minum plus 6.25 mm (0.25 in.) of steel plate at mos~ and a
fuel cell containing diesel iitel.
An evaluation was performed (Ref. 86) (1) to ascertain
that the pressure recordings were meaningful and correct
and (2) to determine the impulses to which persomel within
the simulated troop compartment of a lighting vehicle
would be subjected when a shaped-charge jet passed
w through the walls of the compartrnen~ ‘Ibere was no signifi-

l.,~
I cant difference when the jet passed through fuel prior to
entering the test fixture or through the lid cell within the
lono fixture either before or after traversing the fixture; therefore,
WLkn3tknms the shock is deemed due to jet passage only. A plan view of

0
:’
F- 5-10. Peak Sound Presure L4W?.k and
‘%” Dumtion Limits for TR3 (Ref. 81)
the test chamber for measuring shock efkcts of shaped-
charge jets penetrating into the chamber is shown on Fig. 5-
19
.&.

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MIL-HDBK-684

‘“r

I
160 dB @ide-On)
!8
:11
m
155 dB (Reflected)
i!
I t 1 1 1 1!11 I n ! 1 i !111 i 1 I I ! ln~

0.1 1 too 1000

Impulse, Pass

Figure 5-1% Ear Injury Criteria

5-3.4.1 Description of Events aO = velocity of sound in ti, mh

When a shaped charge is fired, the jet from the charge Vj = jet tip velocity, m/s.
moves along the axis of the charge at a velocity of 6100 to
7600 mls (20,000 to 25;000 ftfs). As the high-speed jet trav- Suppose the jet tip velocity .Vj is 6100 IWs (20,000 tis) and
els through the air in the test chamber, it generates a shock at standard ~temperatureand pressure aO = 340.4 m/s (111‘7
wave. The jet tip moves forward at essentially a constant ft/s); therefbre, the angle between the jet trajectory and the
velocity while the shock front, detached from the tip of the shock wave cone is
jet, moves perpendicularly to the jet axis at the same veloc-
$
340.4
,()
ity. Because this shock is continuously caused by the jet tip
as it passes through air, the shock front propagates radially cl = $IC1 — = 3.2 deg or 0.056 rad.
6100
in the form of a cone. The general geometry of that shock II
‘1 (5-8)
(ignoring wall reflections) is as shown on Fig. 5-13 where V
is the shock wave velocity normal to the jet trajectory. Only
in the imedlate vicinity of the jet tip is the shock strength The shock front propagates as a very small half-angle coni-
great enough for higher shock propagation speed. A vector cal surface,: which is not greatly different from a cylindrical
wave front.’
diagram for shock front propagation is shown on Fig. 5-14.
The shock fkont forms a cone with an included angle ct Estimate@times of shock arrival based on an estimate of
Vj and the ~givenshock geometry can be determined. This
estimate is done for a given transducer Pi by calculating the
a.

()
time for th~ jet to travel to the plane of the transducer and
a = tan-l — , deg or rad (:-7) then using sound speed to calculate the time to propagate
Vj
from the je:,axis to the transducer (to) ~,, i.e.,
where 1
cx = angle between jet trajectory and shock wave,
deg or rad

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MIL-HDBK-684

O
,’

External Fuel Tank -

\
shaped
charge

-d —
‘etT-v
/ Smukited
Compartment

.
Storage

(6 it) 1.629 m

1
-!3

Jll
0.914 m (3 it) Simulated Troop Compartme

--.---+0 -.. *
-Pressure Transducer 3 (P.J

Pressure Transducer 2 (PJ

Figure 5-12. Test Imtallation (Ref. 86)

,,
0 (t=),
i
d.
= ;+;
d’.
,s (5-9)
jo
where
di = disrmtce between the point of enrry of the jet
and plane of transducer Pi, m
#i = distance between jet and axis of transducer Pi,
m
t= = time of arrival,s. “

Given V’ = 6100 UI/Srad = 340.4 ds, and clz = d’l =

0.914 m (from Fig. 5-12), the time for the shock wave to
Figure 5-13. SImck Wave From Shaped- reach Pa is
Charge Jet (Ref. 86)

~ +~ = 0.0028 s.(5-1O)

w’ -
(ta)p =
2

Similarly, the time for the shock wave to reach PJ given ~ =

a.
6100 ill/S, dP9= 1.829-0.305= 1.S24 m and d’P~= 0.914m
(fiornFig.5-12)is
Figure 5-14. vectorD~ of Vek)dties
of
Shaped-Charge Jet and Shock Wave (Ref. 86)
1.524 + 0.914
(tJp = — — = 0.0029 S.
3 6100 340.4

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MIL-HDBK-684

The difference in time of arrival (Atd), ~ of the shock Given fa = 0.9 ms and di = d’, = 0.914 m (from Fig. 5-12),
2’ 3
wave at the two transducers P2 and P~ is estimated to be 1 @

[. [ (0.914)2+ (0.914)2] 5
(Ata)p ~ = (t~)p - (f~)p ,S (5-11) yf =
2’ 3 3 2 0.9 x 10-3
= 0.0029 – 0.0028 = 0.0001 s or = 1436 111/S(4714 ftis).
0.1 ms.
This is a reasonable velocity for a high-speed span ffag-
For weak ballistic shocks, reflections off chamber. sur- ment, and @ere was a fragment impact dent in the pressure
faces can be traced as if they were sound waves, at least to transducer &sing,
estimate arrival times of reflected shocks at gage locations. Test No. 2, Fig. 5-15(B), shows signals ahead of initial
Some incremental arrival times are given in Table 5-6. and reflected ballistic shocks, which start at different times
on different channels. me early signal for P2 is probably
5-3.4.2 Interpretation of Gage Records electrical norse associated with the exploding bridgewire
An evaluation (Ref. 86) effort was undertaken to assure (EBW) firing circuit. This noise is not as visible on P3
that the pressure recordings were correct and meaningful. because of fa lower sensitivity setting, but the signal ahead
The same test fixture was used in all four programs. With of the initial ballistic shock may again be a fragment strike.
Test No. 13,Fig. 5-15(C) has clear initial ballistic shocks,
the help of the estimated times of arrival (t=) ~, at specific
1 but at least ~onereflected shock is hard to identify. Test No.
pressure transducers, signals on the pressure gage records 4, Fig. 5- 151P), shows shocks reflecting horn the top of the
may be interpreted. Fig. 5-15 shows pressure gage records fixture.
with notations to indicate probable signal sources. From thi~ evaluation the conclusion is that the data gener-
Test No. 1, Fig. 5-15(A), presents a problem because ated in Refs. 10, 83, 84, and 85 were valid and meaningful.
there is a large-amplitude signal for P3 prior to the signal on Reviewing ~pressurerecords and discarding the records that
P2, but the ballistic shock should arrive first at Pz. The first appear dou$tful because of possible fragment strikes, instru-
signal on P~ is probably caused by the impact of a piece of ment noise~or other unidentified problems provided the data
span from the back surface of the simulated hull material used in Fig:. 5-16 for side-on pressures and in Fig. 5-17 for @
upon the gage housing. By using the distance from the entry normal pre#res.
point of the jet to the transducer and the measured time of
amival t., the fragment velocity Vfmay be determined: 5-3.4.3 +sessrnent of Potential Injury to Humans
in the Referenced Tests
1 Data arelavailable to establish the overpressure or noise
generated when a shaped-charge jet passes through the crew
(d;+ d’:) 2 ~s compartment of a combat vehicle. Effective sound-deaden-
(5-12)
‘f = la ing design rcan reduce reverberations, but the initial shock
wave from the jet will always be present when a shaped-
charge jet perforates the armor. Examples of the shock over-
TABLE 5-6. TIMES FOR REFLECTIONS pressure versus time and impulse, which is the integral
OF SHOCK WA= TO REACH PRESSURE thereof, are, shown on Figs. 5-7 and 5-15. Fig. 5-15 shows
TRANSDUCERS side-on pressure and impulse versus time horn the jet of a
BRL precision 81-mm shaped charge that perforated 6.25
(Ref. 10)
mm (0.25 in.) of rolled homogeneous armor (RHA) steel
Ata, ms REFLECTED WAVE and 25.4 gun (1.0 in.) of aluminum. Sometimes both the
From To peak pressqre and the impuIse were greater for the reverber-
ations thm’~for the initial shock. Also a triangular approxi-
2.7 I Right End I
I
P,. mation of iithe integral of the pressure would be very
I

0.9 Right End I P, representat&e.

5.4. I Opposite Side I P, The data;fiom the first three test programs referenced can
be convert~d from side-on pressure to normal pressure.
5.4 I Opposite Side I P, Similarly, the data from the fourth program can be con-
2.7 Left End. P* verted to side-on pressure. Thus the potential for ear injury
4.5 Left End “P, to crewmen within the simulated vehicle from the noise c

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MIL-HQBK-684

,,
~, Tme Zero

O I
Initial
wisk
Shock -

Shock Reflected
From End
Fragment
End
Strikes

Probable lnkal “Shock Reflected

BaltisticShock From Right End

(A) Test No. 1

0 I Time Zero

?robable
Electrical
Noise \

P2

Shocks Reflected
P3 From Left End
Probable %
Fragment
\
Strike

Ballistic Shocks

o I?@re 5-15. I%esmme

(13) Test No. 2
Versus Tim~ Tests 1, Z 3, ad 4 (Ref. 83)
(cent’d OKI
next page)
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MIL-HDBK-684
Time Zero
I

P2
Initial
Ballistic
Shocks

Shock Reflected
P3 /From End
/

This appears to be a reflected shock,

but it is hard to estimate the source.
his probably from the top of th~ fixture.

(C) Test No. 3

.

Time zero
II

initial Shock Reflected

Shocks From End

Shw’k Reflected!
From Top
(D) Test No.4
F&we 5-15. (cont>d)

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MIL-HI)8K-684

1E6

O
,’

0 Ref. 83 Line of Regression of Pw on l=

A Ref. 85 \ d
13 195 CM (xl%)
o Ref. 10 \ /
1E5. :
O Ref. 84 a o

’181 dB (Threshold),

0
1E4=

180 dB (Side-On)
r

1000
0.01 0.1 1 10 100 1000
Impulse 1~0Pas
Figure
o 1 E6
5-16. SidAn Pressure Versus Side-on Impulse for Ears

n 1

~ “ Eardrum Rupture

~ ,- “- ,. .“. .-... ”.r,

1/
1000 r I
I w: *:; !
0.01 0.1 1 10 100 - 1(I )0

0 Figure 5-17. IMected Reswres

impulse I., Paas

Versus Reflected Impulse for Ears

5-31
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MIL-HDBK-684
generated by passage of the jet alone can be evaluated. All posed, i.e., they emanate from the jet traversing the vehicle
of the side-on data from the first three tests plus the reflected ifiterior, the exit site penetration, and multiple internal
pressure &ta converted to side-on data for the fourth pro- reflections. ~fter several milliseconds, a quasi-static pres-
gram are plotted on Fig. 5-16. Also the side-on data from sure may ocimr due to heating of the air in the crew space of
the first three programs converted to reflected pressure plus the vehicle ~d the accumulation of combustion products.
the reflected pressure data from the fourth program are plot- ~s quasi-si#ic pressure, however, depends upon how rap-
ted on Fig. 5-17. These two figures show that there is a high idly ventin~ can occur through vents and breaks in the
probability for ear injury from the passage: of a shaped- ifitegrity of @e;vehicle. Potentially, additional internal blast
charge jet approximately 0:61 m (2 ft) from ~e crewman’s events may occur from explosion of explosive-filled
unprotected head. This ear injury, however,’ would more devices, vaporized fuel, and./or hydraulic fluid.
probably reduce the crewman’s efficiency, not incapacitate
him. The lines of regression of the pressure upon: +e 5-4.1 EX.JN~ DAMAGE CRITERIA
impulse are shown on both Fig. 5; 16 and Fig. 5-17 to pro-
Widely accepted injury criteria have been developed for
vide an appreciation of data correlation. :
simple (classical) blast waves, such as the dashed curve on
There would, however, be an even higher probability of
Fig: 5-18. These blast waves have been defined in terms of
injury from reflected sound waves. In all cases the ~em
pik pressure, impulse, and duration. The interaction of a
pressure and impulse due to the “passage of the jet alone
human body’ with complex blast waves, however, has not
were much lower than the peak pressure and impulse due to
yet been completely defined. Extensive data to support
later shocks reverberating from the walls of the simulated
injury crite~~afor complex wave environments do not exist.
troop compartment. Thus, if the’ sound can be deadened
As a result, ~blastinjury assessments inside the reverberant
rather than reflected from the interior surfaces of the vehi-
space of a perforated armored vehicle must be related to the
cle, there will be a significantly lower probability of damage
to unprotected ears. criteria dev~loped for Friedlander blast waves. Ahhough
Eardrums were ruptured in several incidents in SEA. This several met/mdologies have been suggested, none has
type of injury was reported for the left gunner of au ACAV proved sat.k~tory for all conditions. The technique pre-
from the nearby hit of a rocket-propelled grenade (RPG)-7 sented in Ref. 1 for estimating nonauditory injury in live-
(DAN 101), the gunner of an M551 from the explosion of fire tests is dwcnbed.
the propellant chtuge of a nearby 152-mm canister cartridge Based OR current understanding of the interaction
(DAN 310), and the vehicle commander of an ACAV from between the~body and blast waves, a set of injury assess-
the detonation of an RPG-7 on the far side of his vehicle, ment guidelines was developed for the BFV L~ (Ref. 1).
even though the other three members of his crew did not First, the t&d positive duration is determined, and an
suffer similar injury (DAN 336). In addition,’ the loader of “effective peak pressure” is graphically extrapolated (shown
an M551, who was on top of his hatch, suffered ear “injury” on Fig. 5-18) by drawing a “best fit” curve (Ref. 90). The
(not otherwise specified) from the nearby detonation of an “effective peak pressure” and the “best fit” curve are highly
RPG-7 (DAN 463). All of these incidents involved the dependent on the’person who establishes them. Thus con-
explosion of warheads or propellant. There were no inci- clusions based upon them must be used with caution. The
dents in which “buttoned-up” ve~cles were traversed by a total positive duration is likened to the duration term of a
jet and very few in which a shaped-charge jet passed near an classical blast wave. The “effective peak pressure” ignores
unprotected crewman within a vehicle. the random ~pressure spikes that do not contribute signifi-
cantly to the overall impulse. Pressure pulses are not cor-
5-4 LUNG DAMAGE rected for tr@ducer orientation relative to the direction of
Incapacitating primary blast injury is limited to the air- travel of the;,blast wave. In an ACV gage position and orie-
containing structures of the bodyYi.e., the lungs and gas- ntationrela~~e to the recorded shock waves cannot be deter-
trointestinal tract (Refs. 87, 88, and 89). Blast injury occurs mined accu~ately, but the pressure reflections are already
as a result of an incident pressure wave directly loading the accounted for in the pressure trace. The “effective peak
body. The resultant loading is distributed over the entire pressure” and duration are then compared to the Lovelace
body surface in some manner and depends on the orienta- pressure-duration injury criteria for a prone body in a free
tion of the body to the propagation of the incident wave. field blast wave environment (Ref. 91), as shown in Fig. 5-
The exposure conditions that result in primary blast injury 19. Becauseithe “effective peak pressure” technique consid-
have been roughly determined; however, the precise inj~ ers the total ~uration, quasi-static pressure is included in the
mechanisms are not clearly understood. injury predictions. A similar plot is presented for the case in
‘A complex pressure wave simila.i to those shown on Figs. which the @rson is near a surface subject to blast wave
5-7 and 5-15 occurs inside an armored vehicle penetrated by reflections, Fig. 5-20. Injury predictions with this technique
a HEAT jet. There is an initial fast-rising wave emanating have correlated well with injuries observed in studies for
from the point of penetration. Other shocks are superim- w~ch anesthetized large animals were exposed to complex

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MIL-HDBK-684

~ Peak Pressure

~“Ef!ecW Peak Pressureg

h
>1 ClassicalBlastWave

?. Y. f Impulsefor ClassicalWave

-- QIJasi-StaticPressure
P%
L

— Positive Phase
Duratiun -—————1~

Tme

Figure 5-1S= I!kmmple of Graphic Extrapolation of ’affective Peak Pressure” (Ref. 90)

blast waves from point source explosions in enclosures and 5-4.2 EFFECT OF WEARING BALLISTIC
from HEAT round pmetrahons of APCs. VEST
In 1983 a panel of blast experrs estimated incapacitation Military personnel usually wear a cloth ballistic vest
predictions based on classical blast wave environments (CBV) ptiarily for protection against shell fragments.
(Refs. 1,76, and 90). These guidelines were based on exper- Vests containing ceramic andlor metal hem can provide
imentally obsenfed physical damage from classical blast protection against small arms fire also. Normally, however,
waves and are shown on Fig. 5-21. Accordingly, affected an armored vehicle provides protection against shell frag-
soldiers can be expected to have a 1% incapacitation under ments and bullets. Thus only troops who dismount from
conditions that result in threshold injury to the lung. Sirni- armored vehicles, e.g., infantg or armored cavalry scouts,
lady, conditions that cause death in 1% of the exposed pop wouid normally need ballistic vests unless the combat vehi-
ulation, or lethal dose for 1% (LDI ), are equated to 50% cie in which they fight is prone to span. The most common
incapacitation. An exposure lethal for 50%, or lethal dose ase of blast within armored vehicles is explosion of
for 50% (LDn), is assumed to cause 99% incapacitation of stowed munitions.
the exposed population (Ref. 1). Intermediate degrees of Wearing of a Kevlar@ ballistic vest has been shown to
incapacitation are estimated by assuming a lognorrmd prob- increase both motmlig and morbidity for large animals in a
ability disrnbution based on these three points as shown in strong blast environment (Ref. 92) and to increase intratho-
Fig. 5-22 (Ref. 90). The injury predictions determined fim racic pressures (ITi%) in humans at low overpressure levels
application of the “effective peak pressure” tectilque were (Ref. 93). This effect has also been demonstrated in com-
applied to this curve to determine the anticipated levels of plex wave experiments with animals. Estimates based on
incapacitation (Ref. 1). limited animal experiments with simple waveforms have

o
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M[L-I+DBK-684

or
107

.-—.--_4—---
.
E 106
43
———
—.
---------
-
.- ----- ——
g
E
-—
--——
-—— —-

1
.-i?
g

105

b I I I I 11111 I I I 1 Ill] I I I I [[111 1 I I

02 1 10 ) 1000 5m
Duration of Positive Incident Overt ssure, ms
I
Figure 5-19. Lung Survival Curves W~th Free-Stream Pressure l%pagating Parallel to the Long Axis
I
of the Body (Ref. 91)

indicated that the use of a ballistic vest reduces the over- other test p] yams and is shown on Fig. 5-23* (Ref. 92).
pressure necessary to cause a certain leve~ of mortality by The mech~ m for this lung injury is not known, nor are
about 25510.These extremely adverse effects were for the the reasons ]at some clothing combinations enhance or
cloth ballistic vest, but the most severe tests were conducted attenuate th :xtent of injury. ‘I’hissubject is being investi-
with fatigues and cloth ballistic vests only (Ref. 92). In gated fiu-the kCV crewmen, however, wear a Kev@’ bal-
another progr~ intrathoracic pressure changes due to air listic undergarment rather than the bulky ballistic vest. The
blast were monitored while five human volunteers wore dif- ballistic undergmment has not been evaluated for its effect
ferent uniform combinations. A transducer was emplaced on blast inj~ry but is thought to be less hazardous than the
near the gastroesophageal junction of each of the volun- ballistic vest because it is lighter, 1.7 kg versus 2.9 kg (3.75
teers. The uniform combinations were (1). fatigues, (2) lb versus 6.1 lb). To estimate the effects of protective cloth-
fatigues under a field jackeg (3) fatigues under a cloth bal- ing on blast injury for evaluation of the LIT program, the
“effective p~ak pressure” was assumed, by representatives
listic vest, (4) fatigues under a ceramic vest, and (5) fatigues
of the Surg#on General, to increase by 33% when the ballis-
under a cloth ballistic vest under a ceramic ballistic vest
(Ref. 93). The mean maximum H’Ps of these combinations
1
were 7.4 ItPw 7.9 KE&8.7 ItPa, 7.2 kpa, and 7.4 kPa, respec- *OnFig. 5-23mortalityrates for the 420-kPagroup are plotted for
tively. These test results, each the ‘meimof five tests on dif- animalswith‘~d withoutthe cloth ballisticvest.LethaIitylines are
ferent individuals, show basically the same results for drawnusing the commonprobabilityslope (5.593)determinedfor
combinations (l), (4), and (5), a slightly higher result for 13speciesoff@imals(Refs.92 and 94). In tests with sheepat peak
overpressureloadings of 420 KPa, 5 of 6 sheep in cloth ballistic
combination (2), but a significantly higher result for combi- vests (CBV),,diedwithin 30 minutes of the blast, but in similar
nation (3) (Ref. 93). The increase in the probability of injury tests of sheep!withoutthe CBVSand with the same peak overpres-
caused by use of the cloth ballistic vest was shown in two sureloadings;only 3 of 11 sheepd]ed of the blast effects.

5-34
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MIL-HOBK-684
#
,,
O

—___ -— -- ---- ————

----- -. --——
~ t-
“9 ---- ,
---- 4 ---- -—. 4. --—.
& I@ , \ . b ——-— . ~_
I

I ! 11111 I I I 11111 I 1 1 i Itll I 1 I i 1!11 I I I

02 1 10 100 1000

Duratjon of Positive Incident Overpressure, ms

Figure 5-20. Lung Survival Curves With Body Near a Reflecting Surface (Ref. 91)

0 10,000

1000
LethalDose for So%ofthePopuialicur

*
a- Lethalhe for1%ofthe POpufatiorr
2 100
m
g Threshcdd
&

10 dllllllll- --

11 I 1 i 1 1 1 Ill 1 1 I ,,,,,1 I I I 1 1 111 1 1 I I !111

0.1 1 10 100 1(
Time, ms

F- 5-21. Bowell Prmure-Duration Iqjury Criteria (Refs. 1,76, and 90)

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MIL-HDBK-684

Probability of Nonlethal Lung D&nage

99.9 99 90 50 20 2 0.5
1000 I I I I I I I I I I I I I I
800 1
~
/
600

400

g
a-
% ---

.
80 40ms - ~\\
50ills ~
KM)ms I
60

ii
40 I 1 i i i I 1 I I I I 1 I
0.1 1 10 5P 80 98 99

Probabirty of Lethal Lung Dahage

Figure 5-22. Probability Plot of Percent Incapacitatiorqfor Lung Injury (Refs. 1 and 90)

tic vest is worn and by 1790 when the ballistic undergarment scaled for an average person of 70 kg mass at sea level
is worn (Ref. 1). (Refs. 88 ~d 91). The scaling techniques used are described
On the other hand, the ballistic vest worn by ACV crew- in Ref. 95. lfl%etwo scaled parameters used are scaled inci-
men can protect those crewmen from span and other behind dent peak overpressure ~~ expressed as
armor missiles, as was shown in SWA in 1991 where the
vest is credited with saving the life of a BFV driver hit by a 1,
large piece of metal launched by the explosion of onboard
ammunition (Ref. 65).
F. = P,:,Pa (5-13)
o
where
5-4.3 SCALING OF PRESSURWIMP?.JLSE
P$ = peak incident overpressure (measured at the
LOADS test site), Pa
5-4.3.1 Scahg of Peak Pressure Versus Duration P,l = mean atmospheric pressure at sea level
by Lovelace ‘ = 101,353 Pa
Richmond et al (Ref. 94) and later White et al (Ref. 91) P. = ambient atmospheric pressure, Pa
discuss the tendency of the lethality curves to approach iso-
pressure lines for “long” duration blast waves. Therefore, and scaled @sitive duration 7 expressed as
the lethality curves shown in Figs. 5-19, 5-20, and 5-21
demonstrate dependence on only pressure and duration.
Data from impulsive loading tests on animals conducted
at the Lovelace Foundation in Albuquerque, NM, were

5-36
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MIL-liDBK-684

too
1- 1
~ 10
1 10 S0 93 Ss
al 1 I
1.7
t
2
1
2.s
1
3
1
4 5t 1 !
a
I
10
t ! I
a
I
t.imahy,
%
Sc3M Tm, m
YancyY. Phillips,ThomasG. Mundie.J. T. Yelverton,andDonald
Response to Blast”,
R RichmorId “ClotlI Ballistic Vest Alters Reprintedwith permission.Copyright@byNew York Academyof
Jmwnalof Trauma,VOL28,No. 1 Supplement,pp. 149-15LGWfl- sciences.
liams & IV- 1988.
Figure 5-24. Scaled ~ktiOIB and
Figure 5-23. Log Probit Plot for Lethality Fol- PartiahImpt,dse Analyses of Animal Tolerance
lowing Blast Expmure (Ref. 92) (Ref. 95-)

where 10~ (Pm/PO)= 0.3639+ 1.0595t;’

r+= positive duration of pressure (measured at test
site), ms x (?rtano)’n (lol,353/Po)ln,
mm = mass of an rtverage man =70 kg .
dimensionless. (5-16)
m. = mass of test animal, kg.

Fifty percent mottality curves and data points for both

O
,’! These scaling factors are applied to data described in Ref.
91 and scaled for standard sea level pressure, i.e., 101,353
Pa (14.7 psi), and for the approximate mass of a human
‘large” and “small” animals are plotted versus peak pres-
sure on 13g. 5-24. The experimental data for all animaLs
body, i.e., 70 kg (weight of 154 lb), to obtain the equations were obtained by exposing the animals near a reflecting sur-
for a peak pressure of Pm, exposure to which results in the face to shock-tube- or high-explosive-charge-generated
probability of death of 50% of the exposed population: blast waves, and rhen the data were converted matbemati-
1. For hinge* animals (q monkey, dog, goa~ sheep, caily to the peak pressure that would be attained at sea level.
cattle, swine, man) the curve in Fig. 5-24 is The datum for man was obtained by analysis of an incident
in World War II.

log (Pw/PO) = 0.6146 + 1.4492r;* 5-43.2 Scaling of Peak pressure Versus IsnpuLse
x (r?t=no)ln (lol,353/Po)ln, by SWN
An alternate presentation that relates morbWy to blast
dimensionless (5-15)
wave overprwssure and impulse rather than to overpmssure
and duration was developed by Baker et al (Ref. 96).
2. For small* animals (mouse, hamster, raq guinea
Because specific impulse is dependent on pressure as well
pig, rabbit) the curve is
as duration, pressure-impulse lethality or stu-vivrdility
cmes appear to be more appropriate for use. Also values of
% adjectives “large” and “small” for animats are unfortunate peak pressure and impulse are routinely reported in blast
becausethe monkeysand mbbk. for example.are the same mean wave measurements or predictions.
weightand cars arejust sli@Jy heavier.The “Earge”animalshave The following relationships or scaling laws were derived:
lung densitim (averageof 194kg/m’) that are approximatelyone- 1. For the ~cakxl incident peak overpressure (using
half those of the “small” animals (average of 367 kglm’), and
“targe” animals have normalized lung volumes-lung volume SwRI practice) P*W~,,the effect of incident overpressure is
divided by body mass--(average of 29.8 ntUkg) approximately dependent on the ambient atmospheric pmmtre and
the times those of the “small” animals(averageof 9.08 nWkg).
(Ref. 95) D
F~wR,= ~, dimensionless (5-17)
o

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NML-HDBK-684

where which the long axis of the body is perpendicular to the

P, = peak incident overpre5sure, Pa direction of ‘propagation of the blast wave so that the axes
PO = ambient atmospheric pressure, Pa. are scaled incident overpressure and scaled specific
impulse. To ~mplish this modification, it was necessary
2. The effect of blasit wave positive duration is depen- to determin~ the pressure and duration combinations that
dent on ambient atmospheric pressure and the mass of the produced each survivability curve, calculate the scaled inci-
body. Scaled time (using SWRI practice) ~~.~lis dent overpre!ssure and scaled specific impulse by using Eqs.
5-17 and 5121, and reconstruct the survivability curves
accordingly. ~These reconstructed curves are shown on Fig.
t+ P~
?~wR1 = ~, Pain .s. kg-’n (5.18) 5-25. l%es~ curves represent percent survivability, and
m higher scal~d pressure and scaled impulse ,combinatiom
where allow fewerj survivors. Presenting the curves this way is
m = mass of body, kg. advantageous because they apply to all altitudes with differ-
ent atmosp~ric pressures and all masses (or sizes) of
3. Specific impulse i, can be approximated by human bodies. Once the incident overpressure and specific
impulse for ~ explosion are determined, they can be scaled
by using Eqs. 5-17 and 5-21. The value for mass used in the
is = ~ P~t, Pa-s. (5-19) scaling is d~termined by the demographic composition for
() crew members. Suitable averages for body mass are 55 kg
(weight of 121 lb) for adult females and 70 kg (weight of
The use of Eq. 5-19 assumes a triangular wave shape. For 154 lb) for ~dult males. It should be noticed that the smaller
“long” duration blast waves, which approach square wave bodies in th$ case are the more susceptible to injury.
shapes, this assumption is conservative from an injury
standpoint because the assumption of a triangular wave 5-4.4 LCjADS FROM A SHAPED-CIL4RGE JET
shape underestimates the specific impulse required for a Fig. 5-25 is used to evaluate the probability of lung dam-
certain percent lethality. Eq. 5-19 is also a close approxima- age. The dafa from the four test programs (Refs. 10, 83, 84,
tion for “short” duration blast waves, which characteristi- and 85) described in subpar. 5-3.4 were scaled by the tech-
cally have a short rise time to peak overpressure and an nique described in subpar. 5-4.3.2 and are plotted on Fig. 5-
exponential decay to ambient pressure. The total wave is 26 for nor&al pressure. Scaled overpressure and scaled
nearly triangular. By application of the blait scaling devel- impulse values were calculated using Eqs. 5-17 and 5-21.
oped at the Lovelace Foundation for peak overpressure and These calculations were for a human with a mass of 74.8 kg
positive duration to the conservative estimate for specific (weight of 1165lb). All data fall entirely below or to the left
impulse determined by@. 5-19, the scaled specific impulse of the impulse asymptote for the threshold of lung damage.
;. can be determined: Thus no luiig injury is predicted for that shock from the jet
of a warhead passing 610to914 mm (2 to 3 ft), i.e., the dis-

“is= ;P~wR1.
i~wR,,
Palfl -s. kg-lB. (5-20)

Substituting Eqs. 5-17 and 5-18 into Eq. 5-20 and then
using Eq. 5-19 provides ~, in terms of is, Po, and m

i$
+= , Pa*n.s.kg-lB. (5-21)
P? rrlln

As indicated by Eq. 5-21, the effect of scaled specific

impulse j, is inversely dependent on ambient atmospheric
pressure and the mass of the human body.
As mentioned earlier, the air blast damage survivability 10’ ‘“ ,.O 10’ Id 10
curves constructed by researchers at the Lovelace Founda- Scaled Specilic Impulse ~ PalR.sl&
tion (Refs. 88 and91) are based on incident overpressure at
sea level and duration. It was, therefore, necessary to mod- Figure 5-25. Survival Curves for Lumg Damage
ify the survival curves for free-stream applications, for to Mm(Ref. 97)

5-38
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MIL-HDBK-684

o IE6 ~

Legend
o Ref. 83
u

Q Ref. 85

1 E5 0 Ref.10
0 Ref. 84

1E4 I

1000
0.01 0.1 i 10 100 1000
Impulse i, Pas
Figure 5-26. Lung Damage Poteidial From ?&t Data of Reflected Presure Vemus Reflected Impulses
0 tame of the pressure transducers tim the jeq from an em studies as was derived from combat records of the two
exposed crew member. world wars. A new threat to the eye is damage caused by
hers, which are being used in increasing numbers on the
5-5 13YIZ DAMAGE modem battlefield (Ref. 100).
5-5.1 BACKGROUND Throughout all of this worlG several themes have per-
The potentiaJ for incapacitating eye damage in war has sisted. The primary one is that prevention is better than
generated a large amount of research and writing. Because cure, and a corollaty is that very little can be done on the
of the sensitivity of the ey~ there is a higher rate of ocular battlefield to treat a seriously injured eye. ‘he early treat-
injury than one might expect for the surface area exposed ment goal is to avoid further injury and transport the casu-
TEe eyes account for about 0.3’%of total body surface arq alty to a medical facility as soon as possible. The opinion of
but eye injury is present in nearly 1(Moof nonfatal battle W. T. Lister (Ref. 101) recorded in 1915 is still applicable to
casualties (Ref. 98). Prior to World War II, bullets, shrapnel, frontline medical carE of eye injuries
shell fragments, .spall, bayonets, chemical warfare agents
(especially mustard), blunt objects, flame, and blast were “In reviewing the ophthalmic injuries in warfare, the
the main causes of injury. Because of the wide use of armor- outstanding features are their severity and the impossi-
piercing ammunition in World War Ii and the threat of expo- bility, in almost every case, of employing conservative
sure to nuclear weapons after the war, there was increased surge~. If the eye is toucha it is spoilt.”’
emphasis on flash bums and flash blindness. During the
Vietnam conflict the widespread use of mines and booby- Of course, modem ophthalmic surgery has much to offer
traps resulted in a dramatic increase in eye injtie-about even severely injured casualties, but it is still necessary to
three times that for World War II (Ref. 99). ‘l%ecombination transport the patients to locations where the surgery can be
of greater risk and better methods of diagnosis and treat- perfonrted First aid for eye injuries is still limited to fhsh-

,,,
0
inem has maintained a high level of interest in eye injury
and eye care, but expeti,emal work in battlefield trauma
associated with ACVS has not kept pace. In many cases the
ing with water and then protection of the eye horn further
damage by careful patching and the use of rigid shields. The
complement to modem surgery in preservation of vision
same type of eye injury risk data is being generated in mod- cannot be a dramatic improvement in frontline medical

5-39
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M! L-HDBK-684
.SClera
&re; it must be prevention of the injury through better vehi-
cle design and protective eyewear.
Crew members and passengers in armored fighting vehi-
cles exposed to hostile tire have virtually the entire range of
battlefield threats previously mentioned, which include flash
that causes bums and blindness. Exploding munitions may
produce gas clouds at temperatures of approximately
3000”C (5432”F) (Ref. 23), and penetration of armor plate
may produce a ballistic impact flash with & effective tem-
perature of approximately 3100 to 3700”C (5612 to 6692°F)
(Ref. 102). Much of the work on modeling ke physiological
effects of such sources has been conducted with carbon-arc
sources with temperatures of about 5500”C (9932”F) (Ref.
103). Consequently, a number of unanswered questions
remain:
1. What is the full range of flash temperatures and Fi&me 5-27. The Eyeball (Ref. 100)
durations seen in ACV fires including those produced by
shaped charges, KE penetrators, conventional artillery, and closes to ad$nit less light. The lens focuses the light onto the
mines? retina, which contains rods, cones, and nerves that react to
2. How can the actual environment in the ACV be the light received to present a picture to the brain.
t,
measured, thoroughly documented, and then reproduced
under controlled conditions? 5-5.2.1 Foreign Bodies
3. How can the effects of each factor on vision risk be Injuries ~aused by foreign bodies are expected in ACV
evaluated separately, and how can the combined effects be tires associated with exploding munitions or armor penetra-
realisticallyy represented? tion. Mani~ns and pigs both showed evidence of penetra-
4. What are the cost and./or benefit factors for each tion by sm$ll mettd fragments (span) when placed in test
proposed vehicle design change, and what are the principles vehicles and subjected to explosive force created by shaped
of risk avoidance that suggest the type of design changes charges an! a simulated beach mine (Ref. 24). Ballistic
that will be most efficacious? impact from armor-piercing projectiles may produce a simi-
The answers to these questions cannot be found in the lar effect. l@e interface between projectile and armor plate
cument literature for several reasons, the most important of is hypothesized to be liquid (Ref. 102) and thus increases
which is that an experimental pro~am to describe the inca- the likelihood of a shower of hot metal fragments entering
pacitating effects of eye injury would be complex, costly, the vehicle.;,The velocity of these fragments is of consider-
and necessarily multidisciplinary. It would require study able interest. Although they ‘“notedthe disrnbution of pene-
techniques and instrumentation not available as recently as tration andl:burn evidence from small metal fragments,
10 years ago. Reduction in performance by a human opera- neither the ~edlcal personnel (Ref. 24) nor the engineering
tor.cannot be uniformly related to only one adverse medical personnel (Ref. 58) described either the size distribution or
condition or a set. Although evaluation of the medical con- the terminal ballistics of these missiles. Both characteristics,
dition(s) must play a role, the entire environment of the however, me of great interest in assessing the likelihood of
ACV must be considered. Because the vehicle environment ocular injuiy. Particles less than 0.5 mm in size and less
is cuirently defined rather narrowly for only a few opera- than 0.5 mg in mass are rarely found within the eye because
tional ‘conditions, the broad study cannot be done until the they usually lack the kinetic energy required to penetrate the
missing data described by the previous quesiions are ‘sup- tough outer covering (sclera) of the eyeball (Ref. 99).
plied. Some data are available in Ref. 1; these are presented Designs that favor the generation of many small, low-
in subpar. 5-5.2.4. energy p~cles might be advantageous compared to those
that produce a lesser number of high-mass, high-energy par-
5-5.2 IJIJURY MECHANISMS ticles. Whatever the description, accurate characterization
The eyeball, Fig. 5-27, is cont@ed within the cavity of of the expected particle size and velocity dkribution would
the orbit in the skull, which protects it from most damage. aid in specifying practical protective eyewear. Much work is
The eyeball is covered by the sclera or sclerotic coat, i;e., a being done on predicting span quantity, size, and velocity.
dense, hard, transparent material, which protects the internal Another design consideration for material likely to
parts from most penetration injuries. The cornea is another become an intraocular foreign body is its reactivity within
hard, dense, transparent material that protects the iris and the eye. Even a material that is considered inert may cause
lens. The iris is a shutter that opens to admit more light or degeneration of the retina and viaeous substance of the eye

5-40
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(Ref. 24). If the foreign material is at all reactive, local liq- of clothing and equipment in the vehicle. l%e heat ihm fire
uefaction of the vitreous gel (vitreous humor) will lead to could also vaporize chemical agents carried into the vehicle
,,!,’
0 leaching of the material and rapid dissemination of active on the boots and clothing of its crew and passengem; mus-
ions throughout the eye. Iron and copper are examples of tard would be especially dangerous in this regard because it
common reactive materials that are also quite destructive is persisten~ stable, and still regarded as a likely chemical
and eventually lead to widespread liquefaction of the vitre- threat agent Gas masks would furnish good protection for
ous gel and to intetierence with membrane function in the the eyes afyinst this threa~ but they would have to be put on
eye (Ref. 99). In every case of foreign body penetration, the before any exposure to the chemical agents. The need for
best course is early removal. In this regard, personnel such protection, however, might be overlooked because
should be aware of the ease with which fragments within exposure to dangerous concentrations of mustard may not
the eye can be located by sonography, X ray, magnetic reso- be noticed for two to six hours, by which time severe dam-
nance imaging (MlU), or related techniques and. removed age could be done (Ref. 104). The incapacitation that fol-
with magnetic probes or other devices. There is a possibility lows 6 to 12 h after exposure to mustard can be very severe
that an ophthalmologist would recommend materials be initially, i.e., it can effectively blind the casualties (Ref.
used for an inside vehicle liner that are not reactive whb eye 105). Because the time required to cause injury decreases
liquids and are easily detected and removed from the eye. wirh successive exposure% even of a mild nature (Ref. 106),
The best solution, however, is to use materials that will not detection of low concentrations of such agents maybe par-
span or be pulverized. This solution poses a potential prob- ticular y important in an ACV due to the possibility of recir-
lem because liner materials that will not span or be pulver- culating contaminated air and vaporizing any mnaining
ized are apt to become a focusing medium that confines agent should a fire occur.
spdl and pulverized armor into a smaller cone than other-
wise generated. l%is action, much I&e a choke on a shot- 5-5.2.4 Flash Effects
gun, focuses the debris and thus increases the potentiaJ for
Eye damage caused by radiant energy has been studied
the debris to injure personnel. This effect has been observed
extensively since World War II (Refs. 107 and 108) but usu-
in tests of both armored vehicles and aircraft canopitx.
ally with regard to nuclear explosions. The applicabiMy of
WbiJe consitkxing this guidance, design persomel should
this work to the environment in ACV fires remains unclear.
alsOobtain @OdiC UptkS OtlMkMKXSin O@ltklkOtO@-
,,” It is unlikely that the effective temperatures in ACV flashes
cd science. ‘fhe potential to protec~ maintain, and restore
o reach the Ievel of those of a carbon arc (about 5300”C or
sigh?is far greater now than it was 50 or even 20 yr ago, and
as the underlying science continues to evolve, the design 9572”F), and the different effec~ that might be expected on
the human eye are not defined. Investigators have assumed
techniques used can be expected to change. This situation
that animal eyes, e.g., rabbits and monkey$ are good mod-
will also exist for other types of injuries including those
els for human eyes, but the criteria for comparison are not
caused by imitant chemicals, e.g., if dry chemical fire extin-
well-developed (Ref. 108).
guishant is used in an active or passive fire extinguisher sys-
Neverthdess, the US Army currently bdieves a huni-
tem and if it is thrown in the face of a crewman, it could
nance level of 20 mJ/mm2 .sr for 5 ms in the wavelength
irritate his eyes.
range of 400 to 1400 nm causes permanent retinal injury
(scotoma). Injury to the cornea due to a welder’s fiash may
5-5.2.2 Elot antior Burning Liquid Droplets
be expected at a kuninance of 0.1 mJ/mm2s at wave-
Prompt degradation of fighting or escape abilitia would lengths of 200 to 320 nm. Similar to sunburn, thouglL this
likely be caused by exposure to burning fuel droplets in the
effect will be delayed for several hours. Crew members or
fireball that follows the penetration of an ACV fuel cell.
passengers who are vulnerable to exposure to these light
Because its temperature may be 1000”C (18323 (Ref. 83),
energy levels are assumed likely to be severely injured by
contact of the fireball with any tissue-including the eye-
related effects, such as blast or fragment penetration- Others
would result inan immediate bum with instantaneous pain.
may be affected by tempormy flash blindness similar to that
Lossof vision would be immediate. These fuel or hydraulic experienced by looking at a No. 2 Sylvania photoflash bulb.
fluid droplets could have a bulk temperature of 71 to 177°C
Luminance measurements in the BFV live-fire tests showed
(160 to 351°F) as well as be surrounded by burning hy~
fiash btindness could last up to 3 s in daytime and up to 6s
carbon vapor.
at night. Approximately two minures* are required to
recover fully to the dark adaptation levels that existed prior
5-5.2.3 rrritantchemicals
to the flash. In surnm.my, the US Army currentiy believes
DuringWorld War I and more recent conflicts, the promi-

0
::
nence of eye injuries involving chemical agents reflects the
great sensitivity of the eye to irritant chemicals. % ACV
the could produce gases irritating to dte eyes by the burning
~s time estimmeis related to an ACV cmxman who has red
tightsand other visionaids withinhis vehicle.There is furtherdis-
cussionof dark adaptationin subpar.5-7.1.3.

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MIL-HDBK-684
that survivors of ACVS attacked by antiarmor munitions ral and synthetic polymers contain carbon and, when com-
will not have permanent eye injuries from flash (Ref. 1). busted, evolve carbon monoxide and/or carbon dioxide. The
There was considerable experience during World War I relative qu~tities of gases generated by a material depend
with temporary blindness in patients who had been close to primarily on the amount of oxygen present during combus-
exploding artillery projectiles. In most cases’this condition tion and tde combustion temperature. Gaume and Bartek
cleared within a week (Ref. 109). This type of injury also (Ref. 112) ~ite the type of material burning, its combustibil-
occurred in SEA, as has been noted in subpar. 4-1.2. In ity, the tem~rature reached, supply of oxygen, air currents,
DAN 101 the left gunner of an ACAV suffered temporary and fire-rekdant treatment. Bebrauskus et al (Ref. 113) cite
‘blindness from the nearby burst of an RPG-7. In DAN 670 a literature that references over 400 compounds evolving
crewmam of an AWAAV h4551 suffered eye damage from from the decomposition of wood and 400 compounds from
the flash of a bursting RPG-2; he was reported to be unable the decom~osition of plastics. Material burned at one tem-
to see and was evacuated by helicopter. perature might yield one set of gases and, when burned at a
different te~perature, yield another set of gases (Ref. 114).
5-5.2.5 (hIKWSSiOllS and Contusions A harrnless~gas might become toxic when combined with
Concussions and contusions are fieqtiently closely another hat@less gas (Refs. 115 and 116). In addition to
related, they originate from an explosion or the impact of or gases prevalent in smoke, thermal decomposition products
on a blunt object. Both can result in deformation of the eye, may include simple saturated and unsaturated hydrocarbons
tearing of internal blood vessels, and/or detachment of the (e.g., met.h~e, ethane, and ethylene), partially oxidized spe-
retina. Any of these conditions would result in decreased cies (e.g., acetaldehyde and acrolein), and more complex
vision or even blindness, and the problem could be tempor- aromatics (e.g., benzene and toluene). Materials also may
ary or permanent. Because of the relatively small amount contain ni~ogen, sulfur, and halogens and, when thermally
of space in an ACV, avoidance of concussion injuries is rjif- decompose@,may generate additional toxic gases including
ficult when an explosive charge enters the vehicle. ammonia (NH~), hydrogen cyanide (HCN), nitrogen oxides
(NO=), isoqyanates, nitriles, sulfur dioxide ( S02 ), halogen
5-5.3 SUI$!M!ARY acids (HCl~ HBr, and ElF), and other halogenated species.
Eye injuries experienced during fires in ACVS have been (See also Refs. 117 and 118.)
well described in the literature. Projection.4 of the incapaci- ‘l%elarge number of diverse chemical species present in
tation caused by these injuries can be expected to be in error smoke affe~ts many organs and/or systems in the body and
to the extent that the acnml environment in the vehicle is causes myrjad physiological and biochemical alterations.
unknown. Because the human capacity to function requires Many of ~ese alterations are masked by the effects of
hypoxia-producing and irritant gases, which are the most
the integration of many individual capabilities, it should be
prevalent tixicants in smoke and generally are present in
considered in the context of the whole ACV environment,
the highest concentrations. Some gases might have more
not individual parts. In the case of eye injury, common bat-
thw one physiological effect. Some toxins can have differ-
tlefield experience suggests that damage to or loss of sight is
ent effects ‘that depend on dosage. For example, nitrogen
one of the most traumatic events that can happen to a per-
dioxide (N02) is an irritant, but at high doses it can create
son. Whether temporary or permanent such a condition can
mechanicdbarriers to oxygenation and become a mechani-
be expected to have a severe adverse impact on every per-
cal asphyxiant (Ref. 112). Consequently, fire scientists often
son’s ability to carry out instructions and perform a mission.
categorize the major ‘fireeffluents into two main classes the
Therefore, eye protection, or eye armor, must be provided.
hypoxia-producing gases (also referred to as narcotic or
5-6 ASl?HYxMmON, TOXIC GASES, asphyxiant igases) and the irritants. Examples of common
hypoxia-prdducing gases and a hypoxia-producing condi-
AND PARTICULATE SOLIDS tion are carbon monoxide, HCN, and reduced oxygen.
Smoke is commonly defined as a complex mixture of the Examples of prevalent irritants are HC1, HF, acrolein, and
airborne solid particulate, liquid drops, and gases that solid partict$ates. A third catchall class has been designated
evolve when a material undergoes thermal decomposition for those c~emicals with “other and unusual specific toxici-
(Ref. 110). Thermal decomposition of a material may occur ties” (Ref. 119). Many components of smoke may fit into
as a result of anaerobic pyrolysis, oxidative pyrolysis (comm- this category, but these compounds generally are present in
only referred to as “smoldering”), and/or flaming combus- low conceri~ations and are not analyzed. Whh few excep-
tion. Although all of these processes could conceivably tions their effects are not monitored in laboratory exper-
occur at some stage of a real fire, few fires start or progress iments. Nevertheless, it is possible that some of these
without oxygen (Ref. 111). Exceptions are fires fheled by compouncki contribute to the incapacitating and lethal
gun propellants and monopropellant that contain sufficient effects of smoke inhalation, even though the effects of the
oxygen or other oxidizers to combust. hypoxia-pr~ducing toxicants and irritants predominate.
The thermal decomposition of any material results in the Few studies have been conducted with controlled combi-
evolution of a wide variety of chemical species. Both natu- nations of gases and with observation of the resulting addi-

5-42
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tie, synergistic, or antagonistic interactions(Ref. 120). One communication tasks necessary to move the vehicle to

o
,1,
interesting model, however, is currently being pursued*
(Ref. 113). The hypoxic environment and heat of a real fire
might intens~ the effects of the toxins, especially asphyx-
iants (Ref. 116). Belles (Ref. 121) showed that laboratoty-
cover or to continue to fight in the vehicle.
The most prevalent asphyxiant gases and/or condition in
smoke are carbon monoxide, carbon dioxide, HCN, and
oxygen depletion. Each is discussed in the paragraphs that
scrded smoke toxicity tests do not predict toxicity in fuli- follow.
scale smoke toxicity tests. Different time courses for differ-
ent toxins make it difficult to assess their combined effects. 5-6.1.1 Carbon Monoxide
AIso toxins have been shown to have both immediate and Carbon monoxide, the most ubiquitous product of com-
deIayed effects (Ref. 120). Add to these chemical, physical, bustion of both natural and synthetic materials, is formed
and/or physiological complexities another layer of animal when there is incomplete combustion of carbonaceous
and/or human perfotmmce complexities, and it is easy to materials. ‘Ilk colorless and odorless gas combines with the
see why scientific progress in predicting human perfor- hemoglobin of red blood cells to form carboxyhemoglobi.n
mance during fires has been slow. Revalent gases in smoke (COHb) and interrupts the normal supply of oxygen to body
atmospheres generated by the combustion of natural ador tissues. The affinity of hemoglobin for carbon monoxide is
synthetic materials and the gas concentrations considered more than 200 times greater than it is for oxygen. Even par-
hazardous are shown in Table 5-7. tial conversion of hemoglobin to COHb reduces the oxy-
gen-transport capability of the blood and results in a
5-6.1 HYPOXIA-PRODUCING GASES JWD decreased supply of oxygen to critical body organs+such as
CONDITIONS the brain and the heart. In addition, carbon monoxide
For obvious reasons, there is little experimental data on impedes the dissociation of oxygen fiwm oxyhemoglobin in
the effects of various contaminants restiking from cotnbus. the capillaries and thus further decreases the availability of
tion on human performance. In addition, most of the litera- oxygen to body tissues (Ref. 128).
ture on the effects of such contaminants on animals has used The asphyxiants am some of the most deadly toxins.
the lethal concentration at which 50% of the exposed sub- Belles (Ref. 121) found that in full-scale toxicity tests, car-
jects expire (LCW) as the dependent variabie. Wkh a few bon monoxide was the major toxicant. It is especially lethal
notable exceptions (Ref. 126) most of these investigators in fires because of its insidious nature. Cagliostro and IAas

0 have used nonprimate animal models.

.Some rese.atchers have repotted behavioral measures
(Ref. 129) reported that the general effects of carbon mon-
oxide on Iwrnans reported in the literature include headache,
such as the toxin concentration at which 50% of the animals lack of coordination, dizziness, weakness, blurred vision,
became incapacitated (ICM), i.e., the time of useful ftmc- naus~ vomiting, collapse, 10SS of consciousness, and
tion, or the effective concentration (ECW) at which animals death. The effects of carbon monoxi& on the performance
produce a response 50% of the time. (The “time of useful of lower animals, e.g., mice, are better known than for many
function” was originated by Gaume and Bartek (Ref. 112) other toxins (Ref. J29). ... .
to index the length of time during which an animal could The toxic effects that result from exposure to carbon
escape from a given concentration of contaminant.) In a monoxide are due to hypoxia and depend primarily on the
comprehensive review of various approaches to combustion concentration of the gas, the duration of exposure, and the
toxicology, ~phtl, Grand and Hartzell (Rd. 127) alveolar ventilation. Although other factors including the
described 22 different combustion toxicology methodokt- age and health of the individual may increase susceptibility
gies. Of those, 16 involved measuring some end point short to carbon monoxide intoxication, the symptoms produced
of lethality. l%e definitions of incapacitation and types of by exposure to carbon monoxide are directly t-dated to the
behavioral taslrs, however, have varied greatly, and ahhough amount of hemoglobin that is converted to COHb and thus
such information might be relevant for predicting how long is unavailable for oxygen transport. The symptoms and
a soldier might have to escape fkom a vehicle, it is question- effects that have been reported in humans with various
able whether such data could help Prdict how long a sol- COHb saturations are shown in Table 5-8. These data indi-
dier and.lor a crew could perform the cognitive, motor, and cate rltat at COHb levels below 30% the effects in most
individuals would not be sufficiently severe to prevent
*&ibrauskas,Levim and Gann have kid OU1an approach co use escape from the fire environmen~ but at levels above 30%
fire toxicity data systematicallyco applyavailable data to a new the effecm could incapacitate some individuals. At COHb
situation.These data am to be used in theirN-gas Modelcoevalu- levels above 50% very severe symptoms occur. Some inves-
ate the toxicity hazard in a newly detined sitt@on. This modelis tigators consider that a blood COHb level of 50% or greater
intendedto reduce the need to conductUsts with animalsin order is evidence that carbon monoxide was the primary cause of

0 ,,”
to esrabtish the concentrationof combustionprtxkm needed to
cause 50%ofanutnber of animalsto die. ’fit. istnodelh asbeen
adapted to buildings but is not currently adapted to cotnbat vehi-
cles.
death (Refs. 131 and 132), whereas others believe that death
may be attributed to carbon monoxide when the COHb satu-
ration is 60% or greater (Ref. 133).

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MIL-HDBK-684

TXBLE HAZARDOUS CONCENT&YIIONS OF M@OR TOX.ICA~S

5-7. GENERATED BY
THERMAL DECOMPOSITION OF MATERIALS (~efk. 115 and 122 through 125)
9
‘1
TOXICANT ACGIH / HAZARDOUWLETHAL WITHIN
TLV-STEL, IDLH, Smcj A FEW MINUTES*,
ppm ppm ppm 1! ppm or %
Carbon monoxide 400 1500 5000 [ 8000
Hydrogen cyanide — 50 350 280
Carbon dioxide 30,000* 50,000 . 12%
Oxygen depletion — — <1270
Hydrogen chloride . 100 >500: 1000-2000
Hydrogen bromide 50 >500 —
Hydrogen fluoride 20 -400 50-100
Ammonia 35 500 >1ow~ 2000
Acrolein 0.3 5 30-100 >10
Formaldehyde ‘2** 100 . >50
Suhltr dioxide –t 100 600-800
Nhro.gen dioxide 5 50 >200 i 250
Styrene 100 5000 —r —
Toluene-2, 2- 0.02 10 - 100; —
Diisocyanate 1
AmericanConferenceof GovernmentalIndustrialHygienists(ACGH-1) thresholdlis$itvalue(TIN) (Ref. 108),short-termexposurelimit
(.STEL)= The concentrationto which workerscan be exposedcontinuouslyfor a shortperiodof time (15 tin) withoutsufferingfrom
irritation,chronicor imeversibletissue damage,or narcosisof sufficientdegreeto in~ase the likelihoodof accidentalinjury,impairself-
rescue, or materiallyreduce workefficiency

ImmediatelyDangerousto Life or Health (ID~H)= The maximumconcentrationfromwhichone could escapewithin 30 rain withoutany a
escape-imparingsymptomsor any irreversiblehealtheffects.TheseIDLHlevelswerepublished(Ref. 1,24).
i
Short-Term(10 rnin)Lethal Concentrations(STLC),ie., fromTernll and others(1918)(Ref. 122)

*FromRef. 115exceptfor hydrogen.chloridevaluesfromRef. 125

X+oposed changev~ue
.’, .
?Proposeddeletionof STEWvalue

5-6.1.2 Hydrogen Cyanide Since cytochrome oxidase is involved in the use of oxygen
Hydrogen cyanide (HCN) is one of the most rapidly act- in practically all cells, its inhibition rapidly leads to loss of
ing, toxican~. HCN causes h,istotoxic ~oxia, in which cellular functions (cytotoxic hypoxia) and then to cell death.
enzyme irshibition prevents normal cellular metabolism In contrail with carbon monoxide, cyanide does not
(Ref. 127). According to Terrill et al (Ref. 122); HCN is a decrease tlie availability of oxygen; it prevents the use of
rapidly fatal asphyxiant that resulis from the combustion of oxygen by the cells. The heart and brain are particularly sus-
wool, silk, paper, polyacrylonitrile, nylon, and polyure- ceptible to ‘inhibited cellula respiration. Although cardiac
thane. Because HCN causes increased respiration, it could imegularitiep are often noted in EICN intoxication, the heart
also cause increased intake of other airborne toxins. Inhala- invariably outlasts respiration, and death is usually due to
tion of HCN vapors can cause severe toxic effects and death respiratory arrest of central nervous system origin.
within minutes to a few hours, depending on the concentra- The physiological responses of a human to various con-
tion in the atmosphere. ‘he toxicity of HCN is due to the centrations of HCN are shown in Table 5-9. According to
cyanide ion that is formed by hydrolysis of the chemical in these data, approximately 50 ppm may be tolerated by a
blood. Unlike carbon monoxide, which remains primarily in human for ~0 to 60 mitt without difficulty, 181 ppm may be
the blood, cyanide ions are distributed throughout the body fatal after ~0 rein, and 270 ppm or more is immediately
water and thus come in contact with the cells of tissues and fatal. !~
organs.. Cyanide reacts readily with the trivalent ion of the Because carbon monoxide interferes with the transport of
cytochrome oxidase enzyme to form a cytocbrome-oxidase- oxygen by ]the blood and HCN interferes with the use of @
cyanide complex and thereby itilbits cellular respiration, oxygen by Icells, it might be expected that simultaneous

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MIL-HDBK-684

‘lXBLE 5-8. HUMAN RESPONSE TO TABLE 5-9. PHYSIOLOGICAL RESPONSE

OFHuMANs
ToVARIOUS
O
,!, VARIOUS CONCENTRATIONS Ol?
CARBOXYHEMOGLOBIN (Ref. 130) COIWENTRATIONS OF XYDROGEN
BLOOD
CYANIDE IN AIR (Ref. X23)
SATURATION, RESPONSE OF CONCENTRATION
Corn, % HEALTHY ADULP
RESPONSE mgfL ppm
0.3-0.7 Normal range due to endogenous CO
Immediately fatal 0.3 270
productions; no known &trimmmd
effect Fatal after 10min 0.2 181
Fatal after 30 rain 0.15 135
1-5 Selective increase in blood flow to Fatal after 0.5 to 1 h or later, 0.12-0.15 110-135
certain vital organs to compensate for or life threatening
reduction in Oz-carrying capacity of Tolerated for 0.5 to 1 h without 0.05-0.06 45-54
the blood immediate or latent effects
Slight symptoms after several hours 0.024).04 18-36
5-9 Visual light threshold iItClW3Sd
Reprintedwithpermission.copyright *by American Conferenceof
GovernmentalIndusrxialHygienists,Inc.
16-20 Headache; visually evoked response
abnormal
5-6.1.3 Carbon IXoxide
20-30 l’hrobbing headache, nausea, fine Carbon dioxide is a colorless, odorless, noncombustible
manual dexterity abnormal, judgment gas. Carbon dioxide is less lethal, but the presence of other
and calculation ability impaired toxicants intensifies its effect (Ref. 113). It stimulates the
rate of breathing and thus can increase intake of other con-
30-40 Severe headache, nausea and vomiting, taminants in the air (Ref. 124). When inhaled in elevated

,;
o 50-60
and SyDCO~

Coma and convulsions

concentrations, carbon dioxide may produce mild narcotic
effects, stimulation of the respiratory center, and asphyxia-
tion, depending on the concentration present and the dura-
tion of exposure (Ref. 131). Although an increase in
67-70 MIA if not treated pulmonary ventilation may result from inhalation of 1% or
less+the initial effect of carbon dioxide is noticed at concen-
*Exposmeto carbon monoxideconcenaationsin excessof 50.000
ppm can result in fatal cardiacarrhythmiabeforethe earboxy- traaons of about 2$70(20,000 ppm), at which breathing
knoglobin saturationis significantlyelevated, becomes deeper and the tidal volume increases. The depth
of respiratioti increases with irkreasing concentrations of
Modifi@ with permission,from theAnnualReviewof Phanna- the gas and at 4% is markedly increased. M approximately
cofogyund Tom”cology,
Vol. 15, G 1975by AnnualReview%Inc.
4.5 to 5% breathing becomes labored and distressing to
some individuals. This information basically agrees with the
exposure to the two gases would result in additive effects. symptoms given in Table 5- IO.
Experimental studies of the combined effects of I-ICN and There we conflicting reports regarding the concentrations
carbon monoxide have yielded conflicting results, although of carbon dioxide that may present a serious hazard. One
most of these studies indicate additivity when carbon mon- source (Ref. 131) has stated that concentrations of 8 to 10%
oxide and HCN are both present in cenain concentrations have been inhaled by men for periods of up to one hour with
(Refs. 134 and 135). In a significant study by Higgins et al no evident harmful effects. According to another source
(Ref. 120), however, LCn dues for a 5-rein expmure to (Ref. 136), carbon dioxide is weakly narcotic at 3% and
HCN of rats {503 ppm) and mice (323 ppm) were not statis- causes reduced hearing acuity and increased blood pressure
tically different from thrme for both HCN and carbon mon- and pulse, and at 7 co 10%o it can produce unconsciousness
oxide. The concentration of carbon monoxide in the mixture within a few minutes. The American Council of Govern-
was sufficient to produce a 25% blood COHb level. There mental Industrial Hygienists has recommended a threshold
was no evidence of additivity of effects even when animals liit value for a short-term exposure limit of 15 min for
were exposed to HCN after an exposure to carbon monoxi- 30,000 ppm (3%) of carbon dioxide (Ref. 123).
de that produced blood levels of 25 or 50%. Despite the

0
,,!’
!,
Higgins study, the majority of available evidence indicates
that the effects of @orI monoxide and HCN are additive,
except possibly at a low concmtration of either toxicam
5-6.1.4 Oxygen Depletion
Oxygen is consumed from the atmosphere during com-
bustion. A reduction of the oxygen concentration in the air

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MIL-HDBK-684

TMLE 5-11. HUMAN PHYSIOLOGICAL

EFFECTS OF REDUCED LEVELS OF
TiilM/E 5-10. HUMAN PHYSIOLOGICAL
~ OXYGEN (Ref. 46)
EFFECTS FROM VARIOUS LEVELS OF
CARBON DIOXIDE (Ref. 46) SYMPTOMS OR REMARKS

CONCENTRATION
SYMPTOMS Normal
IN AIR, ppm
250-350 Normal concentration in air
Respiration volume increases, muscular
900-5000 Wh,hout effect coo~dination diminishes, attention and
5000 TLV and MAK value clear thinking require more effort
18,000 Ventilation increased by 50%
25,000 Ventilation increased by 1009o 12-15 Shortness of breath, headache, dizziness,
quickened pulse, fatigue occurs quickly,
30,000 Weakly narcotic, decreasing hearing
muscular coordination for skilled
acuity, increased blood pressure and
movements lost
pulse
40,000 Ventilation increased by 300%,
10-12 Nausea and vomiting, exertion impossi-
headache, weakness
ble, paralysis of motion
50,000 Symptoms of poisoning after 30 rnin,
headache, dizziness, sweating
6-8 Collapse and unconsciousness occur
80,000 Dizziness, stupor, unconsciousness
90,000 Distinct dyspnea, loss of blood 6 or below Death in 6 to 8 min
pressure, congestion, fatal within 4 h
Reprintedwi$ permission.CopyrightO by TechnomicPublishing
120,000 Immediate unconsciousness, death Co., Inc. ,
in minutes
200,000 Immediate unconsciousness, death 5-6.1.5 f$mergistic Effects
bv suffocation
Kaplan et al (Ref. 137) demonstrated a relationship
TLV= thresholdlimit value in the workingmea(US) between rodent performance and nonhuman primate perfor-
MAK= maximumallowableconcentrationin the workingarea
mance during exposure to different concentrations of carbon
(Germany)
monoxide, ~crolein, and HC1. Such an approach could pro-
Reprintedwithpermission.Copyright@TechnomicPublishing vide more ~curate estimates of human performance, and a
co., Inc. cost-effective research approach to predicting human per-
formance capabilities dqring’exposure. Animal models offer
inhaled results in a decreased oxygen partial pressure in the a solution, but care must be taken to avoid overgeneraliza-
blood stream and a decreased supply of oxygen to tissues. tion. For example, Kaplan et al (Ref. 127) noted that
Although all cells of the body require oxygen for proper although the effects of carbon monoxide and HCN on
functioning, the brain and the heart are particularly suscepti- humans and mice are believed to be relatively comparable,
ble to a reduced oxygen supply. Oxygen depletion, however, the effects of HC1 may actually be far less severe for mice
generally does not result in noticeable syrpptoms until the than for humans.
oxygen concentration is reduced to approximately 1670 or To evaluate the potential hazard of a smoke atmosphere,
less. The symptoms exhibited by humans as a result of inha- the possible interactive effects of all of the asphyxiant gases
lation of air with reduced oxygen content are shown in as well as the reduction of oxygen in that atmosphere must
Table 5-11. be considered. The effects of these gases and oxygen deple-
Whether due to asphyxiants or to the low-oxygen envi- tion should be considered additive and may under some
ronment associated with tires, the effects of lack of oxygen conditions even be synergistic. Until there is evidence of
are worth noting. Phillips (Ref. 114) reported a general psy- synergism, ~however, assessment of the hazard should be
chological effect due to lack of oxygen: Individuals may based on s@nmation of the asphyxiant effects contributed
~-think they are rational while exhibiting irrational behavior. by the concentrations of each of these gases and the reduced
~ Cagliostro and Islas (Ref. 129) reported that the general oxygen concentration. For this summation the ACGIH addi-
effects of low oxygen on humans include decreased night tive formula (Ref. 123) for hazardous substances that act
vision, stupefication, impaired coordhation, malaise, loss of upon the s~e organ system may be modified to allow
consciousness, and ultimately death. assessment ‘ofthe hazard from acute exposure to mixtures.

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MIL-HDBK-684

5-6.2 THE IRRITANT GASES AND PARTICU- Any of these disorders can disrupt human performance,
,,
O LATE SOLIDS
Smoke atmospheres contain a wide variety of irritant
especially when the tasks are highly cognitive or complex-
i%udly, any foreign matter inhaled in sufficient quantities
irritates tissue and results in coughing and nasal discharge
gases and particulate solids. Examples of irritant gases pro-
even though it might not formally be classified as a toxin.
duced by combustion of many materials include hydrogen
All smoke atmosptteres contain pardcukue solids that
chloride (HCl), hydrogen fluoride (HI?), and acrolein. In
may initate the eyes and respiratory tract. In additiotL the=
addition, burning materhls may produce ammonia (HN3),
particles may obscure vision and clog nasal passages. The
sulfur dioxide ( SOZ), isocyanates, and various aldehydes
size (aerodynamic diameter) of these partictdates is a pri-
and orgaaic acids.
mary demtninan t of the extent of their penetration into rhe
twpiratory tract and their potential toxic effects. In general,
5-6.2.1 Irritant Gases
panicles with a diameter greater than 5 ~m are removed in
Irritant gases have been differentiated on the basis of their the nasopharyngtd region, and particles with a diameter of
site of action as sensory imitanrs, pulmonary initants, bron- less than 1 pm may penetrate to the alveoli of the lungs. If
choconsrnctors, and respiratory irritants (Ref. 138). Senso~ imitating or corrosive chemicals are adsorbed onto particu-
idants, e.g., HCl, NH3, S02, and acroleirt, are highly S-Ol- late that reach rhe alveoli, these particles may severely
uble and primarily affect the upper respiratory tract. When damage the lungs. Consequently, any airborne, fire-related
inhald these gases stimulate the rngeminal nerve endings substance inhaled in laxge quantities imitates the respimt.ory
of the noa evoke a burning sensation, and inhibit respira- system or the eyes and causes performance disruption.
tion. T&se gases also induce tearing, may cause a burning Materials used to control the fire, although not normally
sensation in the skin, and most will produce laryngeal stim- toxic, could significantly disrupt performance if present in
ulation and coughing. Some sources indicate that the con- Iarge quantities. This disruption occurred in the test pro-
centration is of far greater significance than the duration of gram described in Ref. 83. l%e technician was sweeping the
exposure in estimating the hazards of exposure to sensory dry chemical fire extinguishant out of the test fixture, he
irritants (Ref. 139). raised a cloud of Purple K*, which imitated his breathing
Pulmonary imitants IikE nitrogen dioxide are less soluble passage, and he started coughing and had to leave the test
than sensory irritants, penetrate more deeply into the respi- fixture in order to breathe normally.

0 ratory tract and cause rapid, shallow breathing and a sensa-

tion of labored breathing (dyspnea) and breathlessness.
Exposure to these gases also may result in development of
5-6= Toxic Effects
Nlost irritant gases exert their toxic effects locally on the
pulmonary edeu which is accompanied by painful breath-
skin, eyes, and respiratory trac~ although some, such as HF
ing, and may lead to deati These gases cause little or no and HBr, may be absorbed into the body and produce sys-
irritation to the eye or nasal passages at concentrations sufil-
temic effects. llte irtitant gases do not act on the same organ
cient for pulmonary irritation, and their odor cart be dis-
system or have the. same -mechanisms of action as the
guised among all the other odors within a combat vehicle. asphyxiant gases. Consequently, the effects of imitant gases
Therefore, there can be little warning of their presence. and asphyxiant gases are not additive. Obviously, high con-
Bronchoconstrictors (HCl, NH3, and toluene diisocym-
centrations of irritant gases markedly affect respiratory
ate) are those gases that induce increased resistance to air- fimction and blood gases and impair an individual’s toler-
flow within the conducting airways of the lung. Most of ance to other toxicams including the asphyxiant gases. To
these chemicals also are sensory irritants and act on the evaluate tJte toxic hazard of an aunosphere containing a
bronchial mucosa to produce a painfid sensation. mixture of asphyxiant and irritant gases, the effects of the
When inhalet$ some gases can act as a sensory irritant, a two classes of chemicals should be considered indepen-
pulmonary imitanL and a bronchoconshictor &f. 130 dently as recommended by the ACGIH for toxicartts with
Those titants capable of all three actions are referred to by dissimilar effects (Ref. 123). It is necessary in this evahta-
the general term “respiratory irritant”. Examples are chlo- tion, however, for the designer to take into account the fact
rine and vwy I@ concentrations of acid gases. that when present in stdlicient concentrations, irritant gases
produce physiological changes to the body, which may ren-
5-6.22 PticuIate Solids der the individual more susceptible to the incapacitating and
Phillips (Ref. 114) argued that although the effects of Iethal effects of asphyxiants or other classes of toxicants.
-es in smoke have received much attention, he noted that There could be indirect effects of ties on the }ethaIity of
little has been done to determine the effects of particulate any biological or chemical agents in the area If persistent
reamer. Particles too large to be inhaled can lodge in the chmiczd nerve agents, such as thickened sornan (GD), or
nose, mouth, and tltrww and when swrdlowe~ their alde-
byde and acid coatings may cause nausea and vomiting. *A trade-namedpowderedfire extinguishantcontainingprimarily
Acids absorbed in smoke particles might cause choking. potsssiumbicarbonate

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MIL-HDBK-684

vesicants, such as mustard (HI)), are being used in a con- lytical studies of smoke atmospheres using mass spec@os-
flict, they can be brought into a combat vehicle on the cloth- copy, however, have shown that many chemical species
ing and boots of crew members and passengers. Persistent which are neither asphyxiants nor irritants are generated by a
agents have relatively low vapor pressures at temperatures the combu~on of materials. These combustion products
under 40QC, but the higher temperatures expected in a fire may be of a wide variety of chemical structures including
would convert more of the agent to a gas and, therefore, it saturated ~d unsaturated aliphatic hydrocarbons, ketones,
becomes a more dangerous inhalation threat. Even if decon- aromatic h~drocarbons, etc (Ref. 117). Generally, these
tamination procedures are followed, it may be a practical chemicals are produced in much lower concentrations than
impossibility to remove, all chemical agent ‘contamination the prevalent asphyxiant and irritant gases. In a study of the
that a soldier might pick up from the ground, foliage, and thermal decomposition products of polyvinyl chloride
the vehicle itself. The remaining amounts could be expected (~VC) (Ref. 136), the quantities of the organics, i.e., satu-
to be sublethal, but they might cause significant perfor- rated and unsaturated hydrocarbons and aromatics, from
mance decrements in survivors of the fire. burning PV,C were 36 mglg or less each compared to 583,
Profound behavioral changes that result in a total loss of 729, and 442 mg/g of HC1, carbon dioxide, and carbon mon-
normal aggressiveness have been noted in baboons sub- oxide, respectively, Table 5-12. Although all of these organ-
jected to sublethal doses of GD (Ref. 140). Reports of con- ics depress the central nervous system, it is doubtfid
trolled human exposurti to GD are almost nonexistent, but whether their combined effects would be significant relative
one of the early senior investigators accident@ly ingested a to the effects of the major toxicants. For other materials the
small amount and lived to describe his feeling afterward as results of s~all-scale laboratory tests have shown that prod-
one of profound sadness (Ref. 141). Notwithstanding the ucts of decomposition other than asphyxiant and common
current attempts to eliminate chemical weapons, which date irribnt gases could contribute significantly to the toxicity of
from the time of World War I, the Iran-Iraq conflict of the the smoke produced. Two examples of these materials are
mid- 1980s and the Persian Gulf conflict of 1991 demon- polystyren~ and Teflon@, which under certain conditions
strate the ease with which nerve agents and mustard agents may generate styrene and an unidentified highly toxic
can be obtained and, as demonstrated by the Iran-Iraq con- chemical (~ossibly hexafiuorobutylene), respectively (Ref.
flict, used in modern warfare. Designers of m@ry vehicles 110).
should be aware of this threat to performance as well as the
lethal effects posed by these agents. 5-6.4 DESIGN CRITERIA FOR SMOKE INHA- 9
L@ON REDUCTION
5-6.3 OTHER NOXIOUS PRODUCTS Computer models of combustion and egress (Refs. 142
Asphyxiants, irritant gases, and particulate solids are the and 143) offer a useful tool to designers concerned about
most prevalent toxicants in smoke atmospheres. The effects fire in vehiqles. Any such models with human performance
of these gases undoubtedly dominate the toxicity of the components, however, have to be generated from a relative
smoke produced by most, if not all, materials. Limited aria; paucity of ~ta, and most of that is from animal models.

TABLE 5-12. VOLATILE COMBUSTION PRQDUCTS OF POLYVINYL

CHLORIDE SAMPLE (Ref! 136)
COMBUSTION PRODUCT QUANTITY, mg/g’ COIW3USfiON PRODUCT QUANTITY, mg/g
FIydrogen chloride ‘ 583.0 Bu~e ~ 0.28
Acetic acid . Isopentene i 0.02
Carbon dioxide 729.0 l-Pentene “ 0.06
Carbon monoxide 442.0 PenLane ‘, 0.16
Methane 4.6 Cyclopentene 0.05
Ethylene 0.58 Cyclopent~e 0.05
Ethane 2.2 l-Hexene ,( 0.05
Propylene 0.47 Hexane ~ 0.12
Propane 0.84 0.04
Vinyl chloride 0.60 ;:n:pnme 36.0
l-Butene 0.18 Toluene ~ 1.3
I
*Withthis PVC sampleno residueremained.
9
Reprintedwith Permission.Copyright~ by TechnomicPublishingCo., Inc.

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Because methodologies are still in a developmental state, Smoke generation should be precluded. Fmxtinguisb-
animal models for pefiorrnance effects in the presence of ing systems should be of the type that flush smoke particles
combustion-generated toxins appear to be the only reason- and noxious gases out of the air. F~e extinguishams should
able approach. Mitchell et al (Ref. 144) and Rogers et al be benign, i.e., have minimal toxic, noxious, or anesthetic
(Ref. 145) investigated the effects of combustion of natural properties. The soldiers should be trained to combat the fire
fiber and synthetic polymeric furnishings on rat behavior. first and consider evacuation of the vehicle only after they
Mitchell et al found rats were able to perform various tasks realize that the lire cannot be extinguished or that rlteir
three to five times longer during the combustion of wood safety is jeopardized by fire products. Power ventilation
and natural fiben than during the combustion of synthetic should be improved. Combustible materials should be elim-
polymeric tilings. In addition, they found that factors inated from within occupied compamnents, particularly
correlating with time-t~behavioral incapacitation differed those materials that burn rapidly. Materials used within and
for the two 6re sources. For combustion of natural fiber h- possibly adjacent to occupied compartments should be
nishings, carbon monoxide, cmbon dioxide, and toud hydro- selected to preclude emission of noxious products when
carbon concentration yielded the highest correlations, subjected to high temperatures.
whereas for combustion of @ymeric substances, tempera-
ture, hydrocmbons, carbon dioxide, and oxides of nitrogen 5-7 EFFECTS ON HUMAN PERFOR-
yielded the greatest correlations. In related work with tie MANCE
same subjects, Rogers et al conducted blood analyses after h 1916most of the crewmen in an English Mark IVtank
exposure to natural fiber and synthetic polymeric combus- fell asleep during an attack due to the heat and fumes from
tion for different behavioral criteria and found physiological the engine (Ref. 3). This drowsiness is typical of the reac-
comekttions to the behavioral and physical relationships tions of humans to moderate heat and fumes.
described by Mitchell. More such research that links physi- ‘I’hereis no question that a fire in a combat vehicle will
cal, physiological, and behavioral measures is needed. have a significant effect on the performance of the crew and
There are not many design criteria concerning equipment any passengers. Although the physiological effects of vari-
that would reduce the possibility of personnel suffering ous stimuhrtt components of combustion are often known
smoke-inhalation-type injuries. Some localities prohibit the for lower animals and to a lesser extent for humans, there is

o
use of polystyrene foam for building insulation because it an unfortunate lack of information on their psychological
produces toxic gases when burne~ but such prohibitions and performance effects. The question thus becomes more
should be in local building codes. The Federal Aviation complicated since most research has used escape response
Authority prohibits use of some materials in commercial as the critical dependent measure, and that measure might or
aimrafi, but the prohibition generally is of readily combusti- might not be appropriate for combat vehicle fires. For exam-
ble materials or of materials that lose strength ple, if the vehicle has a minor iire while engaged in heavy
The primary mason that the troops in Vtemam did not comba~ evacuation from the vehicle might be more hazard-
sui%r smoke inhalation problems was the practice of oper- ous to the soldiers than continuing operation of the vehicle
ating with open combat vehicle hatches. The combat vehi- to effect evasion (as described in subpar. 4-8.4.3). Such
cles simply had more than adequate ventilation and/or the vehicular evasion would require that the event and its con-
troops had their beads outside. Therefore, they cmld sequences, such ns the combustion components, not signifi-
breathe fresh air, and smoke inhalation injuries were not cantly affect the cognitive and/or motor functioning of the
considered a problem. Troops did, however, suffer a very crew members.
high incidence of fragment or bullet impacts that would not
have occurrd if they bad been with.in the vehicles. In other 5-7.1 KNOWN EFFECTS OF COMBUSTION-
theaters or under other circumstances, combat vehicle crews
RELATED STIMULI
will have to stay within the vehicles. When they do, ventila-
tion will become a much greater problem. Specific effects of various combustion products are dis-
The design objective for producers of combat vehicles cussed in this subparagraph along with the likely implica-
should be to maintain h habitability of the vehicle in spite tions for human performance. The effects of intense sound,
of ballistic and fire damage. This would mean preferably not intense l,igb~and intense beat are not usually investigated in
to have a &e ignite. Tfa fire should igtite, it should not prm combustion-related research but they are included here
duce noxious fumes, or if noxious fumes are produced, the because of their obvious implications for combat vehicIe
air witbin the vehicle should change quickly enough so that fires. Although they are discussed separately, these effects
the occupants would not be forced to evacuam or a h would probably be combined in a real combat vehicle fire.
extinguislumt shoidd be used that removes noxious products

0 fmm the air- This concept also applies to particulate. The

overall objective is to maintain vehicle habitability so that
the occupants are not forced to evacume.
S-7.1.1 Effects of Contaminants
Gaume and Bartek (Ref. 112) place contaminantts physio-
logically into one or more of the following categories

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MIL-FIDBK-684

asphyxiants, irritants, anesthetics and/or narcotics, systemic 5-7.1.2 ~ffects of Sound or Blast Waves
poisons, and particulate matter other than systemic poisons. According to Scharf and Buus (Ref. 147), the threshold
These contaminants cari have effects that disrupt petior- for feeling sound waves is between the 120- and 130-dB
mance in a number of ways. For example, irritants and sys- sound pres~he levels. Less-than-painful auditory stimuli,
temic poisons can cause attention to @ift from primary however, c+ cause both temporary and permanent loss of
tasks, asphyxiants can distort reality and result in a physical hearing tha~ could impede the crew’s performing subse-
inability to perform tasks, and anesthetics andlor narcotics quent tasksj especially communications. Jones and Broad-
can distort realhy or numb sensation and perception. bent (Ref. 148) discussed three types of hearing loss that
Although many of the irritants are extremely unpleasant follow exposure to loud stimuli; two of the three are rele-
and painful, at least their presence is known. Often more vant to this discussion.
dangerous is the insidious nature of some toxins, especially The first relevant effect of exposure to loud noise, tempo-
carbon monoxide and carbon dioxide, because the victim is rary threshold shifi, is transient and recoverable. The magni-
unaware of their presence. According to Phillips (Ref. 114), tude of TTS depends on intensity and duration of the
II
some irritants, e.g., overheated chlorinated hydrocarbons exposure. For example, data from Ward, Glong, and Sklar
such as carbon tetrachloride or tichloroethylene, can go (Ref. 149) {~dicate that 100 min of exposure to a 105-dB
undetected until it is.too late. Many of the psychological or noise band ~sults in a 40-dB TT’S. Recovery depends on
performance effects of various toxins are ‘unknown, but a both the intensny and duration of exposure but usually is at
brief review of some of their more immediate physical least a number of hours for the kinds of loud stimuli to be
effects is worthwhile. expected in II ,Iacombat environment. The hearing loss might
As a group, irritants are likely to have profound ~edi- be accompti~ied by subjective ringing in the ears (tinnitus)
ate effects on ongoing performance because attention is (Ref. 150), {which also could disrupt subsequent perfor-
flmost certain to be diverted to more primary physiological mance.
needs. Known behavioral effects associated with various The seco~ relevant effect of exposure to loud noise is
irritants include laryngeal and bronchial spasms, increasing acoustic tr~~rna, which results from short exposures to
hypoxia and asphyxia, blindness, rubbing of eyes, scratch- intense stimuh, such as those that might be experienced in a
ing, rubbing of skin, coughing, increased or decreased respi- combat ve~le. Such noises might pass the pain threshold,
ration, grand mal seizures (Ref. 146), and other abnormal could exce~d the “elastic limits” of the auditory system,
behaviors that would interfere with normal operational or cause perm~ent damage, and disrupt subsequent perfor-
escape behavior long before a lethal exposure is reached. mance of m’ost tasks. Of course, crew members of combat
Some irritants occur more frequently, so they have received vehicles should be wearing protective headgear that would
more attention (Ref. 122). Nitrogen dioxide and other attenuate the effects of loud stimuli to varying degrees (Ref.
oxides of nimogen are s?rong pulmonary irritants. Ammonia 151). The headgear of the crew members contains ear-
causes primary damage to mucous membranes, skin, and phones nee$ed for communication as well as protection.
eyes. If absorbed, monia produces some systemic effects. Passengers, ~primarily troops carried in APCS or IFVs,
Hydrogen chloride gas is corrosive and can cause incapaci- whose principal task is performed after dismounting from
tation long before death. On the moist eyeball, the resulting the vehicle inight not wear headgear that protect hearing. In
hydrochloric acid is an irritant, and pain and/or tearing are fact, such gear wouId inhibit the hearing of dismounted per-
great. Ten-ill et al (Ref. 122) noted that HC1 may be more sonnel and reduce their effectiveness. Headgear, amplitude-
toxic when coated on smoke particles. The halogen acid sensitive e.~lugs (Ref. 152), and other protective mea-
gases, e.g., HF and HBr, are sensory and respiratory irri- sures-wide protecting hearing+an have subtle detri-
tants. Sulfur dioxide is a. pungent intolerable irritant. Both mental effects on human performance by reducing
isocyanates and acrolein are strong respiratory irritants. communication and the salience of alarms, warnings, and
Kaplan et al (Ref. 127) report that the literature indicates important a~ditory cues. Henry (Ref. 77) pointed out that of
that a decrease in respiration rates caused by some irritants 292 men sustaining blast injuries to the ears during HI,
can result in a longer period of useful function. 70 suffered ~vertigo. Most of these 70 had stated that they
Hypnotic, narcotic, and anesthetic gases can cause irra- had been unsteady on theti feet for a few minutes or perhaps
tional behavior, mood swings, or numbing of sensation and/ an hour or Jwo. A few had been unconscious for a short
or perception, which can interfere with escape or other time. Only bee gave a history of a short, acute vestibular
tasks. Examples would include ketones, such as methyl attack, i.e., damage to the inner ear. Sixty-four of the 70 had
ethyl ketone and isobutyl ketone, which do not affect the a perforate~ eardrum, and 14 of the 70 men complained of
lungs, but when they reach the brain, they can cause ccinfu- continuing @casional attacks of unsteadiness.
sion and unconsciousness (Ref. 114). Bromides have well- In summ%zing the effects of noise on human perfor-
lmown sedative effects.. mance, K@er (Ref. 153) described the general disruptive

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MIL-I+DBK-684
effects of noise on mental and motor performance. In addi- degrade if sokiiers are wearing their nuclear, biologicrd, and

o tion, he noted tha individual differences have btxn reported

in the literature with regard to the disruptive effects of
noise. For example, there is evidence that persons with high
chemical (NBC) protective clothing qualified per rnission-
oriented protection posture for threat level four (MOPP-IV).
Of the critical thermal determinants (Ref. 160), which are
anxiety exhibit more performance disruption due to noise. dry-bulb temperature, water vapor pressure, mean radiant
temperature, air velocity, operating temperature, clothing
5-7.1.3 Effe@ of Flash or Flying Pticulatea metabolism, physical activity, and time, all are potenaaUy
For combat vehicles that are on fire, the two extremes of relevant for assessing the effects of a iire in a combat vehi-
light intensity are relevant. For one extreme an intense flash cle. When the heat flom a fire is added to what is likely to be
might be present and have physiological, behavioral, and already a ho~ humid, and poorly ventilated environmen~
cognitive effects on the crew. The intensity of light incident profound performance decrements or collapse are likely,
on the cornea of the eye is not the same as the intensity at especial]y when the probable combat-related mentaI and
tbe retire ‘i%eamount of light arriving at the retina depends physical exhaustion of the crew is considered.
orI a number of factors, which include the size of the pupil. The most obvious effects of a bunt other than pain are an
The larger the pupil, the more light enters the eye. A unit of increase in general rwousal and decrease in motor contro!
retinal illurninance, the troland (td), is based on the fact that and tactile feedback. Both motor and cognitive performance
the iight passing into the eye is proportional to the area of will undoubtedly be affected. The amount of disruption is a
the pupil. The troland is defined as the retinal stimulation function of the severity and location of the burn, the difli-
provided by a source of 1 Cd/m* viewed through a pupil of cuIty of the ras~ and the relationship of the task to the
1 mmz. The troland value for the stimulus is given by td = 1 burned area-
(cd/m2).AP (mm*), where AP is the pupil area in mm*. Hughes and Cayaffa (Ref. 161) reviewed the literature on
Auording to Hood and FinkeLstein (Ref. 154), physical the effects of bums on the cenhal nervous system. They
damage can occur to the eyes if they are subjected to a log found that even minor burns were known to be associated
luminance greater than 8 Cd/mz or a retinal Wn,inance with delayed decrements in motor and cognitive perfor-
greater than 8.5 trolands. Flashes below this intensity can mance. In addition, personality changes, e.g., hostility,
cause temporary loss of visual acuity that ,would interfere aggression, hyperactivity, and emotionally unstable or
with performance. assaultive behavior, often follow burns. Another notable
0
,,;’
On the other extreme, smoke and i%mes can obscure
vision and create physiological impediments to good vision
delayed effect of burns is the occurrence of seizures, which
are found to follow even minor burns, fkom 12 to 48 h fol-
because of the toxic gases or panicles in the smoke. Smoke, lowing the mishap.
d~ andlor solid panictdates can also cause eye irritation
which results in tearing. Jin and Yamada (Ref. 155) showed S-7.2 GENERAL EFFECTS OF HIGH
that visibility, e-g., ability of subjects to read emergency exit AROUSAL ON HUMAN PERFOR-
signs, significantly decreased due to excessive tearing, itch- MANCE
ing, and burning when subjects were in a room filled with an The Yerkes-Dodson Law describes the classic “inverted
imitant smoke more than when subjects were in a room U“-shaped relationship between level of arousal and perfor-
filled with equally dense, nonirritant smoke. In addition, fire mance. In general. as arousal born any source increases,
or explosive damage to the electrical system of a vehicle performance proficiency initially increases and then
might interrupt normal light sources and disrupt human per- decreases. Spence (Ref. 162) and Spence, Farber, and
formance until light is restored or until adaptation to the McFann (Ref. 163) have theoretically and empirically
darkoccurs after 15t020mirt.” extended the relationship to include difficult tasks. Essen-
tially, high levels of arousal have been shown to disrupt per-
S-7.1.4 Effects of Heat ad Bums formance of difficult tasks more than of simple tasks.
‘fbe variables affecting heat stress and the corresponding Consequently, the inevitably high levels of arousal that
detrimental effects on perhmance are well-known for the would accompany most of the specific effects of combust-
general work population (Refs. 157 and 158). Kobrick and ion-related stimuli would have marked detriment effects
Sleeper (Ref. 159) have shown that perfonmmce can further on most human performance for all but simple, well-known
tasks. Because of the highly cognitive and difficult nature of
*Adaptationto the dadr is greatIyaffectedby what ttw individual the tasks involved for many combat vehicles, marked deter-
is doing. An ACV crewman, who has many vision aids built into iorationmust be predicted. In extremely arousing situations,
the vehiclq can adapt more quicldy than a person who is tryingto
tonic imrnobltity, i.e., a catatonic-~ paralyzed state, has

a
,,
1,’
get out of a dark building. A scout wtto is going on night parrol
reqpireseven more time-the time requiredfor such wlaptationto
thedark wasgivento belhforprsomwl
WMd WarII (Ref. 156).
inthe US Armyduring
been observed (Ref. 164).
Jones and Broadbent (Ref. 14$) discusd the general
effects of loud noise on human performance. Portions of

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MIL-HDBK-684

their discussion can be extended beyond noise stimulation showed that exposure to other individuals who do not react
to other intense stimuli, e.g., light flashes, irritant gases, and to smoke can greatly reduce the panic reaction. Phillips
burns, that have precipitous, often’ unpredictable onsets. (Ref. 114) qeported that it is a common military experience 9
They noted three immediate reflexive responses to such for individuals who are normally brave in the presence of
stimuli: fellow soldiers to freeze or run when suddenly isolated.
1. The startle response that is a protective reflex mus- Phillips not~ that important individual differences in reac-
cular response tion to fire situations inciude physical fitness, emotional fit-
2. The orienting reflex that is a “general alerting ness, education and training, past fire experience, presence
response (a ‘what is it?’ reaction)” or absence of others, intelligence, physical reaction to con-
3. The defense reflex that describes more protective taminants ~m the combustion, and the individual’s sense
reactions to intense stimuli. of responslbdity. Keating (Ref. 166) reported that rational
Any or all of these reflexes would almost certainly disrupt behavior is likely during ilres; Glass (Ref. 168) reported that
ongoing performance, and even a momentary disruption in a fire e~gency about 1% of the population exhibits
could seriously affect the crew’s proficiency if it occurs dur- denial and withdraws from reality and either shows inappro-
ing a lengthy or complex procedure.
priate activity or becomes motionless.
Another effect of an unpredictable intense stimulus is the
sense of reduced control and increased uncertainty. When
5-7.3 O+ERVIEW OF DESIGN COUNTER-
subjects have been subjected experimentally to env.~on-
MEASURES
ments in which they have no control or lose control, perfor-
mance of various subsequent tasks has been shown to This paragaph is intended to reinforce the importance of
degrade (Ref. 165). In addition, increased uncertainty can human fact~ considerations in system design to maximize
lead to bad decisions and performance, e.g., “We have been performance m the event of fire. Because it is impossible to
hit can I trust the instruments now?”. Keating (Ref. 166) anticipate all the specific human performance questions that
argued that another effect of increased arousal is a narrow- might emerge for various combat vehicles, the reader- is
ing of attention. referred to ~specitic military (Ref. 169) and nonmilitary
Jones and Broadbent (Ref. 148) described the following (Refs. 17010 172) human factors and human performance
classes of tasks that are especially vulnerable to loud and references. Campbell and Cook (Ref. 173) reported that
unpredictable noises: more nonc~mbat fires (32.8%) in Army ground vehicles
a
1. Those requiring steady.. motor performance such as were started~by soldiers than by any other source; thus vehi-
tracking a target cle designers should be aware of the specific soldier errors
2. Those occurring infrequently, such as engaging a involved and attempt to design vehicles to minimize the
surprise target, or those that are unimportant effects of th~se errors.
3. Those demanding immediate actions required by
aImost all ACV crewmen 5-7.3.1 l?aci~tatirtg Cognitive and Motor Perfor-
4. Those requiring comprehension of meaning, such ~ance in a Crisis
as a gunner or loader responding to a fire command
When the combat vehicle is designed, a task analysis
5. Those requiring flexibility of response such as
should be conducted to determine what decisions and/or
selecting the appropriate round, e.g., HE, HEAT, sabot, bee-
actions are demanded of the crew in a fire situation. The
hive, shot, or smoke.
resulting trkk demands should be addressed during the
Unfortunately, most of the these tasks are required of sol-
design process. Many assumptions should be avoided, e.g.,
diers in a combat setting.
Another potentially counterproductive reaction to high assuming all sensory systems are functional, assuming
arousal is the “panic response”. Keating (Ref. 166) rational decision making, and assuming full motor dexterity
described the widespread belief that panic is an inevitable of crewmen ieven while something in the vehicle is burning.
reaction to fire as a myth. He. argues that true panic is The designer should consider potential crisis environments,
defined by the presence of aIl of the following four criteria: training implications, human expectancies, human anthro-
perceives chances for escape are decreasing, models others pometry, and human performance variables when allocating
who demonstrate extreme behavior, displays aggressive functions ~d when specifying instrument and control con-
concern for own safety, and responds tiationally. After figurations. When designing akirrn systems, designers must
reviewing various reports of actual fires, he reported that by ensure that soldiers are warned, but the designers ako must
his definition panic is the exception rather than the role. be aware that the loud cues and bright lights typical of some
Other impommt variables known to affect both the panic warning sy$ems can themselves disrupt human perfor-
response and subsequent probability of survival are the mance by increasing anxiety and making concentration dif-
social context and individual dMferences. Kelley (Ref. 167) ficult. 4

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MIL+IDBK-684

5-7JL2 Facilitating Escape and Subsequent Sur- least the steel covers used in WorldWaru subpar. 4-

o Vival
Combat vehicles should be des@ed to enable crewmen
to continue to fight or, if necessary, to expedite human
6.2.21.

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0,,
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o 6 ~U~ll
FIRE DETECTION SYSiEMS
Fire detection sysremr are descra”bed.Optical and thermal de~ectorsare described and their tinu”ng,false alarm su.rceptibil-
iry,sensitivity, ahrabiii~, and suitability for use in combat vehicles are covered in detail. The optical detectors include irg%mecf
(IR), visible light, and ultraviolet (UV) types. The thermal &tecrors discussed are con~inuom thermal detectors, and rhey
include therrnistoq themwcouple, eutectic salt, and pneumaric types. Other sysrems, such as thermocouples, thermopiles, and
pertetran”ondetectors, are described

6-1 INTRODUCTION
A fire detection system establishes that a fire is present ous chapters fail to suppress these extraneous tires, properly
within a given compartment of a combat vehicle and pro- designed fire detection and extinguishittg systems provide
vides a signal to the fire-extinguishing system (be it the crew the final measure of fire survivability. l%e savings in person-
or a fixed fire extinguisher) to extinguish that fire. To estab nel and equipment can be significant and can result in pre-
Iish the presence of a fire, the detection system uses sensors served battlefield capability. Combat Ioss data from %lernam
to monitor parameters that are signatures of the fire and showed 2207 armored personnel carriers were battlefield
sends signals propornonal to, or indicative of, the presence losses in one year, 16% of which were desiroyed by sus-
of the signature to a controller. This logic-following element tained fire. Subjective assessment indicatsd that half of these
may be remote, within the control module, or it may be vehicles could have been saved if they had been equipped
local, within the sensing module. The logic element follows with a 100% effective fire suppression system (Ref. 1,).Sim-
a preset logic pattern to establish whether there are signa- ilarly, assessment of combat loss data ~m V~etnam indb
tures present that indicate a fire rather than otkr phenom- cated also that 13% of the M48A3 tanks subjected to direct-
ena, and then it selects and signals the action to be &en to tlre kills and 2% of the tanks subjected to mine kiils could
control the fins. have been saved had they been equipped with a 100% effec-

,,
0
In this chapter, potential tire situations are described in
order to provide insight into the signatures present for differ-
ent types of fires and to estabIish the system timing tteeded
to respond to each type of fire. Other background phettom-
tive fi,msuppression system (Ref. 2). An assessment of the
MO series tank against kinetic energy (K.E) and shaped-
charge weapons indicated that 4.8% would probably be
destroyed by sustained fitel or hydraulic fluid fires if a 100%
ena and conditions am described to provide information effective automatic fire suppression system is not used (Ref.
needed to prevent ermmeous system reactions. Descriptions 2).
of the various types of detection systems are given that Fii detection is a function of the signature of die fire,
inchtde details of the key components and provide informa- layout of the compartmen~ sensitivity of the sensors, and
tion on their capabilities and limitations. Other i,nfotmation the logic followed by the detection device. l%e signatures of
is provided on &tails needed to assure that these systems are a tire are commonly thought of in terms of hea~ ligh~
suitable for use in combat vehicles. smoke, and sound. A broader view, however, includes
detectable pre-fire phenomena such as the imminent pene-
fL1.1 BACKGROUND tration of a fuel celi. A fire detector functions by responding
The design of a combat vehicle is the product of the com- to one or more signature elements of a fire. That information
promises necessary to assure accomplishment of its batde- is provided through a controller to actuate the extinguishing
field mission. Fire survivabili~ can be enhanced by system, which discharges an extinguishant. In its simplest
optimization of design, location of vehicular components, form det.eden consists of a combat vehicle crew member
and materials selection, as described in other chapters. Cur- who sees, feels, smells, or, in isolated cases, hears a fire. The
rent combat vehicles are divided into compartment, each crew member responds by detemining the location and
compartment has different contents, characteristics, and nature of the fire hazard and then taking action to extinguish
operational requirements that affect fire survivability. The the fire, perhaps with an onboat@ portable fire extinguisher.
combustible contents of these compartments vary from The range of the crew’s senses, however, does nol extend to
explosives through readily ignitable materials subject to all compamnents of a combat vehicle. The engine compart-
rapid combustion or less red] y ignitable materials, which ment for example, is usually isolated from the crew. It is for
normally burn more slowly, to items that are difficult to these isolated compartments that remote detectors and fixed
ignite and tend to smolder for a long period of time until extinguishers were developed. The detectors sense one or
changing conditions enhance theix rate of combustion. more of the signature elements of a fire and convey that
fWhin these compartments different degrees of combustion information to the crew, perhaps by an alarm. Extinguishant
0 can be tolerat~ but normally any extraneous fire is undesir- is then released into the compartment either automatically or
able. When the fire prevention techniques described in previ- by the crew. Experience and evahation of dte increased

6-1
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MIL-tiDBK-684
,
complexity of modem combat vehicles have. demonstrated partment. The jet appears as a very short duration rod of
the importance of sensors providing timely, reliable infor- white light ~~ that is visible for 1 to 3 ms. Where the jet
mation. Obviously, a remote sensor that signals a fire after encounters solid layers of material, particularly metal, the 9
considerable damage has already occurred is not very effec- material is splashed backward toward the source of the jet
tive. Similarly, a remote sensor that reports a fire where and spalled ~forward following the jet. Both the splash and
there is none may cause prematurely emptied extinguishers. the span, which are hot particles, usually emit strong flashes
This situation unnecessarily exposes the crew and the vehi- of light. l%+ flash from aluminum is much stronger and has
cle to a greater risk of injury or damage due to a subsequent a longer dukation than that from steel. This splash and/or
fire. span is normally the ignition source for a fuel spray fireball.
Selection of the technique and equipment to be used to This fuel spray when ignited emits an orange to yellow
detect combustion or combustion products should be driven light. This incipient combustion normally spreads rapidly
by”the type of fire and its signatures, the combustible, the throughout the spray. Unless extinguished, this fireball heats
,,
characteristics of the extingulshant and extinguishing and ignites other combustibles, and a catastrophic fire
method used, the characteristics of other materials or phe- results. To prevent burn injury to the occupants, this tlreball
nomena present, the resistance to heat damage of the items must be ext~guished within 250 ms, a time to which the US
to be protected horn the fire or its products, and the configu- Army Surgeon General agreed after considering both
ration and contents of the volume in which the fire would human reaction to heat and tire suppression equipment
occur. A fast-growth fire would require a fast-response capabilities{ The emr emitted by combustion of a hydrocar-
detector system. Therefore, a sensor that requires a fairly bon liquid ~ been characterized and is discussed in subpar.
large mass of material to rise in temperature would probably 6-1.4.
i
have too slow a response, but a detector system that uses 2. Case 2. The circumstances are the same as those for
incident electromagnetic radiation (emr) to heat a fairly Case 1 except that the compartment is unoccupied by
small mass would probably have an adequate response. On humans, e.g., an engine compartment, and the fire can burn
the other hand, a detector system for a smoldering fire longer because the items within the compartment are not as
would have to sense the presence of smoke or the absence vulnerable as a human. For example, the fireball can be
of emr due to the absorption of that emr by the products— allowed to~self-extinguish, but sustained combustion of
probably carbon monoxide or smoke-of that smoldering other combustibles within the compartment is not permissi-
combustion, and the response requirement’ would be much ble. An en~ine compartment differs from an occupied com-
slower. A steel hull can tolerate a higher temperature for a partment in that there are usually exposed hot surfaces, a
longer time than an aluminum hull, electrical insulation and which will Iignite sprayed or spurted combustible liquids
I
hydraulic fluid hoses can withstand flames for a few min- upon conta~t. Those hot surfaces, such as the combustor can
utes, but a human cannot withstand the temperature of a in turbine-~lowered vehicles and the exhaust ducting in die-
hydrocarbon fuel spray fireball for more than a fraction of a sel-powere~ vehicles, also radiate heat, which can compli-
second. Therefore, a steel-hulled vehicle can use a detector cate fire detection. The rupture of the combustible fluid
system that is slower, has a higher reaction temperature, and container c~.also be due to an accident, fatigue failure, or
requires a greater change in temperature than an aluminum- some other Ihlure.
hulled vehicle can without risking excessive damage. Also 3. C&e 3. A shaped-charge jet or a KE penetrator
an engine compartment can resist a fireball and a short dura- passes into,,a compartment and encounters an explosive-
tion fire, but a human cannot. A fairly open compartment filled object. The results can be (a) a detonation of the
can depend upon a detector system that senses incident emr, explosive, (b) a deflagration of the explosive, (c) a less ener-
but a cluttered compartment requires either a great number getic comb% of the explosive, or (d) a mechanical rup-
of incident emr sensors or a detector system that either ture of the casing of the explosive with no subsequent
senses ambient temperature or draws air samples represen- chemical reaction or with chemical reaction of only part of
tative of the entire compartment. the explosive charge. Result is a self-announcing and would
probably ~~ completed before a fire suppression system
6-1.2 EXAMPLES Ol? FIRES TO BE
could react~ hence it need not be detected. Results b and c
ENCOUNTERED should be detected and would cause emr to be broadcast. In
The following are examples of fires that must be detected, some situahons, the emr emitted by Results b and c have
the signatures of these fires, and other signatures that com- been chwa~terized. Result d needs no response by an auto-
plicate detection. While considering these cases, the design matic fire suppression system because a partial chemical
engineer must keep in mind the events that are occurring, reaction self-extinguishes or ceases.
the reason the fire is being detected, and the capabilities of 4. Cap 4. A shaped-charge jet or a ICE penetrator
the fire-extinguishing equipment. enters a compartment, and particles from either or their
1. Case 1. A shaped-charge jet passes through both a associated span make contact with a slow-burning combus-
hydrocarbon liquid in a container and an occupied compart- 9
tible. Com@stion starts either immediately or later. The sig-
ment so that the hydrocarbon liquid is sprayed into the com-

6-2
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natures of this combustion maybe ernr, smoke, products of The radiation emitted by a hydrocarbon frame consists
combustion, heaL and/or sound. primarily of continuum radiation ffom minute sw~ i.e., car-
5. Case 5. Combustion initiates or becomes hazardous bon, particles and infrared radiation from the hot gaseous
without a ballistic impact. An electric wire may sho~ or products, which are mostly water vapor and carbon dioxide.
some nonballistic phenomenon may cause sparks or gener- An example of this radiation is shown on Fig. 6-1 for sus-
ate heat and then ignite some slow-burning combustible tained combustion of JP+ (Ref. 3). Other hydrocarbon f3u-
material. ‘Ilis can be caused by shorting of a wire bared by ids have similar emissions (Ref. 4), and their spectm have
ballistic impac~ accidental abrasion, fatigue failure, or peak excitations at the same wavelengths but with slightly
some other failure. The signatures can be emr, smoke, different magnitudes.
sparking, products of combustion, heaq ardor unusual
ekctric power loss or variations. 6-1.4 DEVELOPMENT OF AUTOMATIC FIRE
DETECTION AND EXTINGUISHING
6-1.3 FIRE SIGNATURES SYSTEMS FOR COMBAT VEHICLES
The signatures of a llre-mesas by which a fi can be Serious development of totally automatic fire detection
discerned-follow: and extinguishing systems began with the acceptance of
1. TWe 1. Electromagnetic radiation, which normally Halon 1301 extinguishant for use in combat vehicIe crew
is lower uhraviole~ visible ligh~ andlor infrared areas (Ref. 5). These systems are capable of automatically
2. T}pe 2. Smoke, combustible vapors, and products detecting and extinguishing a rapid-growth, hydrocmixm
of combustion, which include water, carbon dioxide, and fuel spray fire within 250 ms of its initiation. Such auto-
carbon monoxide matic systems vimually eliminate hydrocarbon spray fire-
3. Ijpe 3. Radiated hea~ heated air, and heated prod- balls as a major casualty producer during comba~ a level of
ucts of combustion
4. T~e 4. Sound. Wor
All of these signamres change with the intensity or rate of
combustion. The intensity of Signatures 1, 3, and 4
inmeases with the availability of oxygen. It is common
knowledge that an oxygen-tich 6re burns h,otter, whereas a
fuel-rich fire is Srnober. A common example often given is
that a Buusen burner, a propane torch, and a natural gas
burner will produce yellow flame when the fuel valve is
fully open; as tbe fuel supply is reduced, the flame will
become blue-almost invisible-and the blue flame is hot-
ter than the yellow flame.
When thermally excita atoms and molecules emit or
absorb emr when electrons within a molecule are excited
iimm one quantum state or relax to a lower quantum state. Wmlqm m
Since the energy levels associated with an atom or molecule (A) lhe Ultraviolet
13nksii FnmJP4 Buntingat SeaLavel
are uniquely defined, the energy spectrum associated with
aansition between these levels is unique, and the frequency
of the radiation thus emitted is considered characteristic of
that particular atom or molecule. As more heat energy is
absorbed by the atom or molecule, however, electrons that
are more finrdy held will “jump” and cause emr of other
frequencies to be emitted also. This additional energy also
swains the bonds between atoms of the molecules, which
may break. Since the emr frequency emitted by the constit-
uent atoms can differ ilom that of the molecule, with added
energy the spectrum emitted may change. Also molten par-
ticles of uncombusted material may be thrown off, and may
radiate other frequencies or absorb some frequencies. This
action in turn further alters the spectmm of tlequencies that Wa-vdq?hm
EM impinge on the detector. Thus emr liom a slowly com- of JP4 Burning
(B)Spectd RadiantIntensity at Sea lava!@tH20 rnn)
busting fire differ from those of a violently combusting fire.
The incipient rapid-growth tire, such as that of a hydrocar- 6-1. Electromagnetic Radiations From
Figure
bon fuel spray, would initially broadcast emr that are differ- WA Burning at % ~Vt31 @#. 3)
ent from those of a sustained fire. (cent’d on next page)

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NUL-I-U3BK-684 !

2.0 UV detector and the IR detector. There are also combina-

tion-type detectors that sense both W and IR signals.
I
6-2.1 GIXYMZAL CIIARACTERISTICS
Optical d~tectors are selected for their sensitivity to spe-
cific wavele[n=g bands and their responsiveness. Incident
.
radiation op@calsensors are of four basic types: photoemis-
sive, photoc~nductive, photovoltaic, or photodiode. (Ref. 7)
The phot~emissive type has a cathode-anode set encased
witfin an evacuated, transparent container. When emr
impinges upon the cathode (which is coated with a material
containing excess electrons), it emits electrons that can flow
in a circuit to the anode. The output of this device is a cur-
rent proportional to the intensity of the incident ernr. This
device is bulky and requires a high voltage to function. At
present, this type of sensor has been supplanted by solid-
state devices,.
The photoconductive-, or photoresistive-, type sensor has
an emr-sensitive resistor between electrodes on a transrxir-
1

ent plate and provides a change in resistance as a function of

0
4,0 ao 80 10.0 12.0 14.0 16,0 the intensity’of incident ernr. This type is relatively slow due
Waveierrgth, pm
to thermal i~ertia.
The photovoltaic-type sensorar solar cell—uses a
(C) Far Intrared Emissions From JP-t Burning at Sea Lwel
sandwich o! unlike materials that develop a voltage across
Fi@ 6-L (COllt’d) the junction l,whenirradiated with ernr. This is the only type
that req~ires no external power, and although fast, it is not
effectiveness that cannot be approached by manual or semia- as fast as td~ photodiode type. This photovoltaic type can
utomatic systems (Ref. 6) but can be achieved by a passive develop 0.4 to 0.5 mA in bright sunlight.
system. Par. 4-8 and subpar. 7-3.2.3 describe such a passive There me ;four major versions of the photodiode-type sen-
system. sor: (1) wi~ a PN junction, (2) with a PIN junction, (3) a
The phenomena upon which combustion detectors are phototransistor, and (4) a photodarlington. The simplest is
based are (1) an increase in molecular activity when heat the PN junction photodlode in which an N-type semicon-
energy is absorbed, which is manifested as expansion of ductor, witlia donor impurity that causes the matrix to have
solid materials, (2) an increase in pressure by a confined a negative charge, is abutted to a P-type semiconductor with
fluid, (3) a change of resistance to electric cument flow in a an acceptor ~kmpuritythat causes the matrix to have a posi-
material, (4) a change in electric potential at the junction of tive charge (Ref. 8). When this PN junction is irradiated, a
two materials, (5) and/or emission of electrons from materi- current can vow. ‘Ilk photodiode is faster than the photoe-
als that normally retain them. rnissive, thel,photoconductive, or the photovoltaic types. The
6-2 OPTICAL DETECTORS PIN junction photodiode has an additional layer between
Optical detectors have been widely applied in combat the P-1ayer @d the N-layer. This I-1ayer, or intrinsic layer,
vehicles and are well-accepted throughout industry. The expands the, range of sensitivity to emr of longer wave-
optical detector systems, e.g., MIL-S-62546 (Ref. 4), used lengths. The PIN-junction photodiode is faster than the In-
in the fast response automatic tire detection and extinguish- junction photodiode. The phototransistor is basically a pho-
ing systems sense emr from the fire that are dwectly incident todiode wi~ one stage of amplification, and the photodar-
on the sensor window or eye. These optical sensors are lington is ~ne with two stages of amplification. The
well-suited to situations in which speed of detection is criti- photodarlington is slower than the phototransistor, which is
cal. Optical sens,ors are selected or adjusted to sense specific slower than ;ihephotodiode (Ref. 7).
spectral emissions that are characteristic of.combustion but These phi$oelectric devices can be made selectively sen-
not normally present in ambient condhions. These emis- sitive to different wavelengths of emr by the choice of the
sions may be absorbed by smoke, dust, vapors present in the base materials (the donor and/or acceptor material), by fil-
air, or deposits on the sensor eye and thus reduce the capa- tering the eti, and/or by design of the detector circuit.
bility of the detector to identify their presence. Similarly, Table 6-1: provides the relative requirements for detector
objects may mask the emanating source. These detectors ys- system respl~nse and extinguisher timeliness; the cases of
tems must be powered, and the detector output must remain fires are matched to the required detector response and
connected to the control unit for the systems to be func- extinguisheti timing. Detector response is characterized as
tional. me two primary types of optical detectors are the ultra ultraf~t (UUF) in microseconds, ultrafast (UF) in rnil-

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MIL-HDBK-684

lX13LE 6-1. FIRE CASES, SIGNATURES, AND REQUIRED DETECTOR RESPONSES

O
,!,

FIRE CASES
(see Subpar. 6-1.2.)
SIGNATURES USED
(See Subpar. 6-1.3.)
DETECTOR RESPONSE
(In Compartment)
EXTINGUISHER TIIvfRWG

1 1,3 UF UF

2 3,1 F,UF,S F

3a * W* w“

3b 1 UUF,WF UF

3C 2,3,1 F,S,UF F

4 %3,1 (Occupied)-S,F,UF F,S

(Unoccupied)-F,UF,S F,S

5 (Occupied)-S,F,UF F,S

(Unoccupied)-F,UF,S F,S

perforationof contaimr
*hmninent
**~si- ~ is ~~ge in resistanceor vol~e

Iisecomfs, fast (F) in seconds, and S1OW(S), which is slower sensitive if it could not sense a iire through a certain density
than the others but less than a minute. Extinguisher timing of smoke. Similarly, it would not be considered sensitive if
would be in the same time regime as the detector or slightly its viewing window became opaque and thus precluded
slower. The signatures used by the detectors are also indi- detection of a fire. Since the intensity of light from a point
cated. The matchings are shown in Table 6-1 ordered from source varies inversely as the square of the distance born
best to adequate; capability and expense are fwtored in. the source, the distance between the fire and the sensor
In a manual iire-extinguishing system, detectors must adversely affects the sensitivity of the detector, particularly
transmit llre information (perhaps via an rdatm) to the crew, when the fire il.rststarts. Finally, the sensor must be able to
which actuates the extinguishers. Operation of an automatic sense fire signatures tit am not directly in tint of the sens-
system adds additional requirements for electrical compati- ing element, i.e., at some angle to the sensor.
bility and false alarm rejection. MIL-S-62546 is for optical Sensitivity requirements are derived from the intended
fire sensors, which are components of the automatic fire- purpose of the fire detection and extinguishing system.
extinguishing systems used in military ground combat and Because it is desirable to minimize the types and numbers
tactical vehicles. This specification &tails optical sensors of sensors used, the detector selected shouId be able to de-
that can detect rapidly growing hydrocarbon fireballs within tect more than one type of tie. As shown by Table 6-1, an
4 ms. This detector senses incident ernr. The requirements optical detector that has a UF response and senses a Type 1
of this specification are independent of the extinguisher and signature would be the detector of choice for a Case 1 ftre,
can apply to sensors using extinguishers such as the water- could be usable for a Case 2 fire or Case 4 or 5 fires in unoc-
filled, explosion-pressurized, void-space extinguishers cupied compartments, and possibly could be usable for a
developed for the Air Force (Ref. 9). MIL-S-62546, includes Case 3C fire or Case 4 or 5 fires in occupied compartments.
both the technical requirements (Many of which are dis- In order to calibrate a detector that is eminently suited to de-
cussed in subsequent subparagraphs.) and the standardiza- tect a Case 1 iire and is usable for a Case 2, 4, or 5 fire, the
tion fea~ which facilitate interchangeability. requirements of ML-S-62546 are stated in terms of thresh-
old bands. Above the upper end of a threshold band, an
6-2.1.1 Sem.itivity automatic fixed fire extinguisher would be actuate~ within
The sensitivity of a fire sensor describes its ability to
the threshold band an alarm would sound or ligh~ and
react and its degree of susceptibility to the stimulation of a
below the lower end the detection system would assume the
fire. That reaction abi~ity and degree of susceptibility are
signature was from an extraneous source and do nothing.
results of the design+ the technology, and the environment.
T?te width of the threshold band is &termined by consid-
A fire detector must be sui%ciently sensitive to senw a fire
eration of the consequences of a false alarm as well as the
during all of the operational circumstances the vehicle
results of a fire in the specific compmment. If the conse-
encounters. For exampl% a sensor would not be considered
quences are not significan~ the threshold band can be wide.
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MIL-HDBK-684
,. In a military environment (particulmly in ground combat nomena sigp.ificantly faster than akemative detectors. This
vehicles with automatic fire detection and extinguishing ability is cri~cal to their application in automatic fire detec-
systems), consequences are usually significant. Hence the tion and extinguishing systems for crew-occupied compart- C
threshold. band is made as narrow as the technology allows ments of ~odern combat vehicles that are subject to a
in order to minimize false alarms. The consequence of a combustibl~~liquid spray fireball.
slow-growth fire false alarm could be increased crew stress Quick detection is required in order to respond effectively
if the warning signal were a loud horn. In addition, false to the rapid~growth fire described in Chapter 2. The rapid-
alarms could lead the crew to lose confidence in the system growth fires of particular concern are those induced by
and to ignore a subsequent potentially hazardous fire. A threat munitions that breach protected compartment armor
fast-growth fire false alarm would release extingttishant and encounter the hydrocarbon fluids contained in the vehi-
when it was not required, and if released into the crew com- cle. These fires pose such catastrophic risks of crew and
partment, the crew could be forced to evacuate the vehicle weapon system losses that they must be detected and extin-
or to cope with the extinguishant atmosphere to the detri- guished in a fraction of a second. The fire-out time limit for
ment of mission performance. By wasting extinguishant, Army grou~d combat vehicle crew compartments has long
such false alarms unnecessarily expose the crew and vehicle been mandated to be no more than 250 ms (Refs. 11 and 12)
to the damaging effects of a subsequent fire. Knowledge by based upon ~protecting the crew from second-degree bums
an adversary that a combat vehicle used a system suscepti- and the effects of severe overpressure (Ref. 6). This tie-out
ble to false ahrms could be exploited, as was planned in time limit has been questioned as not being adequate to pre-
Ref. 10, and thereby would increase the vulnerability of the vent seconci- or even third-degree bums (Ref. 13). A better
vehicle. criterion is the time-temperature inte~al described in sub-
Sensitivity is determined by the fire signatures (emr in pars. 5-2.2.; and 5-2.3. If the desi=wer considers the time
this case) and the intensities of the emr that a sensor can required fo~ the extinguisher to open, for the halon extin-
detect. Fire signature intensity is a function of the physical guishant to flood the compartment, and for complete extin-
size of the fire, the fuel, and the distance of the fire from the guishment of the fire, the time available for the sensors to
sensor, i.e., a small fire close to the sensor and a large fire function is very short. MIL-S-62546 requires detection and
far from the sensor can register the saine signature intensity. appropriate ~ignaling in 3 ms. (4 ms is allowed for discrimi-
It is not desirable to have an automatic fire-extinguishing nating* dete; see subpar. 6-2. 1.4.)
system (AFES) actuate to extinguish a small fire that does Optical sensors have also been tested in a variety of other
not present a hazard to the vehicle or crew and could be military rol~ with responses of less than one second. Proto- @
readily extinguished by the crewmen. Efforts have been type photoemlssion-type ultraviolet detectors for fuel leak
made, therefore, to distinguish between a small fire, for fires in airc~aft turbojets responded in 200 to 1000 ms (Ref.
which an AFES should not actuate in the automatic mode, 14). These ~tectors were designed to monitor a large air-
and a large fire that presents a hazard to crew and vehicle craft engine’’nacellefor combustion of leaked fuel, i.e., JP-4.
and thus would require automatic actuation of the AFES. The senso~~ a type of Geiger-Mueller counter tube,
The requirements for such a system are given in individual responded to radiation wavelengths from 190 to 290 nm
vehicle specifications and for the optical sensor in MIL-S- (1900 to ,2~00 angstroms), which are in the ultraviolet
62546. The specification definitions of large and small fires range. T1-usIdetector was well-adapted to detect propane
are not quantifiable, and the techniques for differentiating flame but lad difficulty with JP-4 flame (Ref. 15). The
between these fire sizes are not defined. In these specifica- longer count time for the latter was probably due to lower
tions a small fire is identified as the flame from DF-2 in a intensity in ~kheshorter wave lengths, ie., UV, the detector
130-mm (5. l-in.) diameter pan at a distance of 1200 mm senses. Rev~w of the spectra of JP-4, JP-8, JP-5, DF-2, and
(47.2 in.) from the sensor or detector. A large fire is the MIL-H-5606 hydraulic fluid flames (Refs. 3 and 4) implies
same flame at a distance of 380 mm (15 in.) from the sensor. that this p@icuhr detector would be insensitive to the DF-2
The goal to differentiate between a fire that does not repre- and MIL-H~5606 flames and only marginally sensitive to
sent a present threat and a fire that must be extinguished the W-4 flahe, Infrared sensors for hydrocarbon tires result-
quickly is a good one, but either the current technology ing from ballistic impacts on helicopters responded in less
needs further development or the vehicles must be designed than 50 ms (jRef. 16).
to preclude catastrophic fires so that such a device is not Response time requirements for slower growth and small
necessary. (See pars. 4-3,4-4,4-6, and 4-8 and subpar. 7-3.2 fires are si.@ificantly longer. Both MIL-F-23447 (Ref. 17)
for descriptions of such design features.) (for use in ~S Navy aircraft) and MIL-S-62546 (for use in
US Army ~litzuy vehicles) have established a time require-
.6-2.1.2 Response Time
ment of 5 s for detection of a small fire.
One major advantage of optical fire detectors is their abil- (!

ity to detect, i.e., sense signatures and then follow a logic !1

sequence to discriminate between fire and extraneous phe- *A “discriminating”detector igtores the signature of a shaped- a
chargejet bu~lreactsto a hydrocarbonspray fireball.

6-6
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6-2.13 False Alarm Rejection not to give a false alarm when the electric power of the

o Full exploitation of the optical detector technology that

afforded the rapid response was significantly delayed by its
tendency to give false alarms (Ref. 18). Unfortunately, the
vehicle and detection system is turned on or if the battery
power decays due to prolonged operation. Nor is the detec-
tor system to give a fake alarm when subjected to these
faIse alarm problem was not confined to the issues of fire environmental exposures:
intensity and thresholds. Instead the problem encompassed 1. Temperature of 125°C (257°F) or -51*C (-60”F) or
numerous nordire sources of similar signatures. Some faIse rapid temperature changes between these extremes
akum sources were discovered during vehicle testing. Dur- 2. Shock or vibration to which the vehicle may be
ing the durability phase of a military potential test of optical exposed
deteetors on an Ml 13 in the late 1960s, a crew member 3. Immersion in water, mobility fuel, or salt fog or
entered the crew compartment wearing a maroon shirt and exposure to fungus, humidity, or sand and dust
cased the extinguishing system to discharge. h was sttbse- me consequences of false alarms are important in peace-
quently determined that the cause was sunlight reflecting off time and potentially fatal in combat. Depending on system
the shirt. This false alrum led to additional testing of that design, in peacetime a false alarm could sound art slam or
detector, which showed it susceptible to sunlight reflecting discharge extinguishant into crew-occupied space. Such
off red objects, to white light reflecting off the red Halon actions interrupt the mission, reduce confidence in the sys-
1301 extinguisher cylinders, and to a standard Army two- tem, and increase vehicle maintenanm requirements. The
cell flashlight with a red filter (Ref. 11). current training procedure is for the crew to evacuate the
MIL-S-62546 contains an extensive list of phenomena vehicle as soon as practicable after the AFES discharges. I.II
that have been found to cause false alarms in the past or combat a discharge would immediately reduce crew perfor-
sources of radiation that will be encountered routinely. mance while they coped with the haion-extinguishant-rich
These false alarm stimuli are given in Table 6-2. in addition atmosphere. Equally important is that the extinguishant
to not responding to the radiation signatures, the detector is would not be available for a real iire. This fact would have a

TABLE 6-2 F’ALSEALARM STIMULI (Ref 4)

o RADIATION SOURCE DESCRWTION

DETECTOR SYSTEM
IMMUNITY DISThTCE,
mm (in.)

Vehicle headlight (low beam) conforming to MS 53023-1

2 Sunlight-direcL indirec4 or reflected * *

t
3 Incandescent frosted glass ligh~ 100 W 150 (5.9) I 25 (1)

4 Incandescent clear glass ligh~ rough service, 100 W 225 (9) I 50 (2)

Fluorescent light with white enamel reflector, standard office or shop, *

5 150 (5.9)
40 Wor20f20W each

6 Electric arc, 12-rnm (15/32-in.) gap at 4000 V ac, 60 Hz 25 (1) I 25 (1)

7 Vehicle IR light conforming to MS 53024-1, low beam 600 (23.6) 300 (11.8)

8 Arnbiem light extremes (vehicle darkness to bright light with snow, * *

water, rain, desert glare, or fog)

9 Sunlight or artificial light reflected fkom brightly colored clothin~ in- * *

cluding red and safety orange at 1500 mm (59. 1 in.) and to near zero

10 Electric flash (180 J minimum output) 450 (17.7) I 225 (9)

i I )

*Irnnnmeal any distance

(cent’don next page)
 Downloaded from http://www.everyspec.com

MUA-IDBK-684

TABLE 6-2. (CO?lt’@

ITEM tiDIATIO~ SOURCE DESCRIPTION !,

‘-
I SMALL FIRE LARGE FIRE

11 Movie light, 625-W quartz DWY lamp (Sylvania SG-55 or equiva- 1200 (47.2) 600 (23.6)
lent)

12 Red or blue-green dome light conforming to MS 51073-1 * *

13 Flashlight (MX 991AJ or other) I * I *

14 Chopped light—individual sources, such as Items 1,2,9, <nd 13 ** **
II
Chopped light-combination of sources, such as Items 1,2:3,4,5,7, ** **
15
and 8

16 Radiation heater, 1500 W 900 (35.4) 450 (17.7)

17 Radiation heater, 1000 W with fan 600 (23.6) 300 (1 1.8)

18 Arc welding-4-mm (5/32-in.) rod, 300A 1500 (59.1) 300(11.8)

19 Acetylene welding-00 tip, 16-”x 150-mm 1500 (59.1) 300 (1 1.8)

(5/8- x 6-in.) flame

20 Muzzle flash from M16 rifle 250 (9.8) 50 (2)

21 Muzzle flash from 105-mm gun 7 ?

22 Lit cigar or cigarette 100 (3.9) 25 (1)

23 Match or wood stick, including flare-up 300 (1 1.8) 100 (3.9)

,.
24 Match or paper, including flare-up 200 (7.9) 100 (3.9)

*Immuneat any distance

**Sameas not chopped
fDktance to be measuredand recorded

measurable impact on the survivabili~ of the crew and include chopped light, combinations of sources, and the
vehicle. muzzle flakh associated with firing weapon systems.
Optical detector requirements include exposure of the Chopped light is the emission from a potential false alarm
sensor to the sources shown in Table 6-2 and the distances source that”is suddenly interrupted by an object passing
beyond which the detectors must not produce false alakrns. between th~ source and sensor. An example is sunlight that
Such requirements represent a compromise between the suddenly hits a sensor when a vehicle hatch is opened (or
false alarm problem and the state of the art of sensor tech- that suddenly is cut off from a sensor by a hatch being
nology. For example, a flashlight must not be a false alarm closed). Combinations of sources occur frequently in com-
stimulus to the sensor, no matter what the distance. The bat vehicles, and have produced false alarms. Because of the
detector technology reflected by Table 6-2, however, cannot different distances at which each source must not produce a
distinguish between a large real fire and an incandescent false alarm;, requirements are set at the greater distance for
frosted light closer than 25 mm (1 in.). As the technology the combixiation source. For example, in Table 6-2 the
improves, the distances decrease, and such changes are requirement for the combination of an incandescent clear
reflected in detector requirements. glass light and a flashlight (MX 991/U) would be 225 mm
Other sources of false alarms that must be considered (9 in.) for a small fire. Muzzle flash from weapon systems

6-8
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MIL-HD8K-684
presents a difficult challenge to those charged with setting or bottle** and did not continue into the vehicle. ~us the bot-

o complying with the fake alanrt requirements for sensors.

The cost of testing to determine the source-to-sensor dis-
tance at which detectors are immune to false alarms can be
tle apparently saved the vehicle fkom further damage in that
incident. The only “bad” result was that the bottle was not
available if there had been a subsequent hit.
prohibitive, and this cost is compounded by the need to test The ability of a detector to dkcriminate provides several
sensots throughout theix field of view. Consequently, advantages that enhance the capability of the vehicle to fight
requirements frequently specify testing at two distances with and survive. Crew performance is enhanced, aside from the
the results being recorded. Such results provide information damage and shock of a nonfire-producing penetration, by
to vehicle designers and users regarding whether there is a not also having to cope with an extinguishant-rich environ-
problem. The designer could then, if necessaty, provide ment during a combat engagement. The crew’s continued
additional masking or filtering for the sensor to reduce the abiiity to engage the enemy conrnbutes to sm%valility,
effect of the muzzle flash or move the sensor to a location which is also enhanced by the retained extirtguishartt capa-
from which the muzzle flash could not be seen. Muzzle flash bility. Discriminatory detectors provide other advantages
is virtually the same as the flash from a hydrocarbon fireball. because they make no additional claim on the scarce inter-
The greatest H? radiation peak is at a wavelength of 3.0 pm nal volume of a combat vehicle.
with secondary peaks at 2.2 and 4.4 pm for a 155-mm M2 A system inco~rating both discriminatory detectors and
artillery weapon (Ref. 19) backup bottles offers maximum fire-extinguishing capabil-
ity. Its application is most appropriate if the risk of a pene-
&2.1.4 Discrimination
tration-induced hydrocarbon fire is high and the surviv-
Discrimination is the capability of a detector to respond to
ability of the vehicle is sufficiently critical to offset the
a hydrocarbcm fire and not respond to the high-intensity,
increased extinguisher volume and increased cos~
short duration emissions caused by penetration of aluminum
‘I%evalue of discriminatory detectors and backup bottles
or steel armor by kinetic or chemical energy ammunition
was indicated in studies that compared alternative fire-
(Ref. 5).
extinguishing systems @efs. 20 and 21). ‘l%estudies com-
As discussed in subpar. 4-1-2.3, gunners will continue to
pared the cumulative probability of survival of alternative
fire at a combat vehicle until they see evidettce of a kill.
extinguisher systems for rhe M992 Field ktillery Ammuni-
., Consequently, multiple penetrations of a combat vehicle are
almost as likely as a single penetration. Automatic h detec-
tion Support Vehicle (FAASV) given one, two, and three

0 tion and extinguishing systems that incorporate nondism”mi-

nating detectors will respond to the fi,mtpenetration without
penetrations of its armor. l%ese studies were based upon a
vulnerability assessment performed at the IX3Army Ba.Ilis-
tic Research Laboratory (BRL) in which shothes were
regard for whether hydrocarbons were encountered, and
passed through every square inch of the presented area of
extinguishant will be expended. If the vehicle survives the
the vehicle at aspects eveg 30 deg around and above the
tit penetration, extinguishartt may not be available to
vehicle to estubiish the probability of hitting ammunition,
respond to a subsequent penetration that does encounter
fuel, or hydraulic fluid. ‘flte vehicle was assumed to have a
hydrocarbons. As a resulL the probability of the vehicle or
fulJ basic load of ammunition 10% of the time, half full
crew’s surviving the second or subsequent penetrations is
80%, and with no ammunition 10% of the time. A fire was
rtduced Potential solutions include a “backup” extinguisher
assumed to occur in either the engine compamnent andlor
equivtdent in capacity to the fitst sho~ discriminatory sen-
tie crew and ammunition compartment if either fuel or
sors, or a combination of both.
hydraulic fluid was hit, and an explosion was assumed to
The advantage of backup bottles compared to discrimina-
occur if ammunition was hit. Fire detection and extin=tish-
tory detectors occurs when first one and later a second pene-
ing systems were not assumed effixtive against ammunition
trator encounter hydrocarbons. A system with backup bottles
explosions but were assumed 100% effective against a fuel
has the capability to extinguish both resulting fires. Such a
or hydraulic fluid fire. Averaging all the shotlines produced
system, however, is at a disadvantage when there are fires
a probability of 0.66332 of encountering no energetic mate-
restdting from any third, or subsequent penetration because
rial, of 0.2276 of encountering ammunition, of 0.0465 of
there is no extinguishant remaining. Other disadvantages
igniting a fire in the engine compartment only, of 0.0320 of
include the additional space required for bottle storage and
igniting a fire in the crew compartment only, and of 0.0307
the increased probability the bottles will be hit. The disad-
of igniting fires in both the engine and crew compartments.
vantage of a fire extinguisher bottle being hit is not wholly
The vehicle probability of survival given one, two, or three
apparent. In the only incident in Vietnam (DUN 336)* in
hits is shown on Fig. 6-2 for no fire protection, for a single-
which an extinguishant bottle was hiq nothing untoward
shot AFES in each compartment artd for a two-shot AFES

:,
0,,
,,,
happenetX the shaprxkharge jet apparently stopped at the

~ documentacquisitionnumber (DAN)refersto filesin the Sur-

vivability Inftxrnaiion and AttatysisCenter (SURWAC)described
irt par.4-12
**No fi~ multi in this incident. The fm.r crewmen were all
wotmded--probablythree by span and the fourthby the blastdama-
ging his eardrums.Noneof the woundswere attributedto the fire
extinguisherbottleor its contents(DAN336).

6-9
 Downloaded from http://www.everyspec.com

M! L-HDBK-684
peratures as low as –51°C (-60”F) and as high as 125°C
4 fin
(257”F), vibration, shock, temperature shock, salt fog, fun-
.ws, sand, !dust, humidity extremes, and electromagnetic 4
interference. The vehicle environment is the nominal 28-V
dc military I vehicle electrical system. Response require-
ments, how~ver, must be met at voltages from 16- to 30:V
dc. Sensors~,mustnot produce false alarms if the input volt-

“
age decays, “andthey must not be damaged by voltages up to
40-V dc. Detectors must withstand reverse polarity and
direct shorts without damage (Ref. 4). Finally, they must
function following immersion in diesel fuel, water, a pres-
TwtAMAFESWith
D~crimination surized water jet, or salt fog.
\
TwoShotAFES
WflhoutDiscrimination
SiqMotAFES Wtiout Diwimindkrr 6-2.2 wES
All currently used emr sensors, i.e., W, visible light, and
No,FireProtection
IR, use the same basic physical phenomena to function. The
~ materials us,ed in these sensors differ because of the differ-
.2 20
s ent reactiork of these materials to emr of different wave-
3 lengths.
I 6-2.2.1 ~traviolet Fire Detectors
I
o 1
I I
2
J
3 Ultraviolet radiation sensors function similarly to visible
Numberof His, dimensionless light and in~ared sensors. W sensors differ primarily in the
materials used, the materials are sensitive to UV radiation
Figure 6-2. Probability of Vehicle Survival rather than ~ or visible light radiation. Many materials are
Given Multiple H&for Three AFES opaque to UV radiation, especially many types of glass, as
configurations (Ref. 21) shown in F&. 6-3. Thus the types of glass that can be used
to make or Iprotect UV radiation sensors are limited (Ref.
in the crew compartment and a one-shot AFES with a one- 22). On the ~otherhand, the W-opaque glasses can be used
bottle manual backup in the engine compartment. This last c
to filter out; unwanted UV radiation, such as sunlight. The
alternative was conducted with nondiscriminating and dis- designer had a choice of both glass filters, which can remove
criminating detectors in the crew compartment. T%eplots in radiation of undesirable wavelengths, and transparent
Fig. 6-2 show that the addition of extinguishers and use of shields, which can protect the sensing element from dust
dkcriminating sensors increases the probability of vehicle and other contaminants and still permit transmission of radi-
survival of subsequent hits. Unfortunately, the studies from ation of des,med wavelengths. Fig. 6-3 shows that even in
which these data were derived did not consider a system 1929 designers had a good selection of glasses that were
with discriminatory sensors but no backup bottles. Conse- transparent or opaque to different wavelengths of light. This
quently, there was no direct comparison between backup selection has undoubtedly increased in the succeeding
bottles and discriminatory sensors. years. W radiation causes photochemical change in many
In subpax. 2-2.1.2 the differences in .fiash intensity and materials that can reduce the useful life of items using those
duration between steel and alufi.num armor when pene- materials. Because UV radiation causes fluorescence in
trated by a shaped-charge jet and other penetrators were some materials, its presence can be detected. UV radiation
briefly discussed. The type of rmqor and/or hull material can be readdy absorbed by many gases and other materials.
used by a particular vehicle incorporating a ML-S-62546 This phenotienon can limit the distance at which UV sen-
sensor requires specific features in the sensor wiring har- sors are useful, but it is also useful in enabling detectors to
ness, i.e., the connector pin assignment code. This informa- discriminate, between a nearby fire and solar radiation. W
tion is provided to assist the detector designer in designing sensors are used in military equipment such as the LM2500
logic for detector discrimination ~d in facilitating the gas mrbine engine on 13DG class destroyers and in the F-
required interchangeability of detectors between steel- 14D, F-15, F-16, F-18, and F-22 aircraft as light-off moni-
armored and aluminum-armored vehicles. tors in after~mers. W sensors are not often used alone in
6-2.1.5 Durability military eq~pmenq they are sometimes used in conjunction
with IR sen$,orsto discriminate better between fire and solar
An optical fire detector should function flawlessly in the
environments experienced by and in the combat vehicle. radiation. UiVsensors are used primarily in industrial appli-
--
cations.
The reliability requirement in MIL-S-62546 for sensors is
not less than 100,000 h between failures. The physical envi- UV sensors currently use a Geiger-Mueller-type output 9
ronment experienced by the combat vehicle includes tem- (Refs. 23 arid 24). A Geiger-Mueller device contains a cath-

6-10
 Downloaded from http://www.everyspec.com

MIL-HDBK-684

LowerLimitof

o .nrl
LowerLimitof
Solar Smxtrum\
WirtdowGlass
&f)ITIOfI
/
Lower Limitof
VisibfeSrxxirum

‘ v-c,cam$la!vi!ass.23mm-
f C, CowAm, f.26 mm”
~i . D,CefesD~t. Z+Omfn
H,%-, t=230mm
4“ dh { v,vda@as%fmz’3omfn
Fo, Fused Oua@t.4.mmm
KL0xr13w Heat FMstlIwt=2.Olmm
CULMQ$ass
ET—1—m—n 0.L(lsMt24ita,
w-& w*
t=1911Ttm
G!sssNa. i?, r.3z?mm
W-2, Csk Tr. tarf= amm”
iP..l W-4, Wtndcw Glass No. 4, I = 3.45 mm
w-lqqf=2Tsmm
l?wwhdmvghss Isstamtald
“dcubte S?n?n@.
d ... A LLm%Res.lib. t=zoImm -

LJl I 1 m Wm r [ 1 1 n c * u

2002202402e0280300320w 3LX13f304004204404eo$ )

me mean thickness tof the sample tfta~ since these glasses are handb!own, often varies
0.5 mm in the samples. This variationcan cause a variationof 6% in WVradiationtransmission.
‘Calculated transmis@onof thicfcnesssequals 2.30 mm of Window Glass No. 2.

0 Fi@re 6-3. Ultraviolet Spectral Transns “ ion Through Various Window Glasses WheII New (Ref. 22)

ode and an anode separated by a dielecrnc. A vokage is designer should contact manufacturers to km what fea-
placed across the cathode and anode. The cathode is made of tures are available before selecting a specific device to use.
a material that emits electrons when imadiated by UV radia-
6-2.2.1.1 Ornnigttard@ W Detectors of Armtec
tion. The dielectric becomes excited when irradiated by that
Armtecproduces a line of detectors based upon its Edi-
same wavelength, andlor by the electrons emitted by Fhe
sone solar blind UV sensor tube; Fig. 6-4 shows an early
cathode, and acts as a photomttkiplier to increase the num-
version, and Fig. 6-5 shows an OmniguardaModel 652 UV
ber of he electrons. ‘R2esefree electrons travel to the anode
Fw Detector. This device has a conicai field of view with
and reduce the voltage between it and the cathode in a sud-
up to 70 deg of off axis area coverage. Fig. 6-6 shows the
den burst. The abrupt voltage change is detected by the Gei-
detection distances for the Model 652 detector for a 0.093 -
ger-MueUer circuit as a single count- The frequency of these m2 (1-fia gasoline fire, the average response time is 1 s if
counts is a measure of the quantity of mdiation received. All
the flame is close enough to achieve sensor saturation. The
the current UV sensors used in fire detection are based upon
time constant is 60 ms. The Matel 652 &tector responds to
these phenomena. The design of different manufacturers’
mu in the wavelength range of 0.19 to 0.26 p.m. This sensor
sensors varies with the shape of the anode and cathode, the wi,ll respond to fuels that produce W upon combustion,
selection of anode matenat, the dielecrnc in the cell, and the such as diesel fuel and other hydroc=bon liquids, alcohols,
con.@ration of the cell. There are also differences in the
acetone, hycfrazine, wood, hydrogen, and plastics including
logic element of the detector and in features such as self-
epoxy. Detector response wiSlbe affected by W@ smoke,
testing devices and contamination resistance features. and angle of detection. Detection distances for combustion
Examples of detectors of some competing manufactumss
of some materials are given in Table 6-3.
follow.* l%is technology is continually changing, so each

,,, *Descriptionsof specific devices do not constitute Govetnmenc

0 endorsementof the devices; they are merdy to iliustnw some of
the feamresavailable.

6-11
 Downloaded from http://www.everyspec.com

MIL4+DBK-684
~ ..,.
-..,..
w,.:,,,
T2kBLE 6-3. TYPICAL ARMTEC UV/IR FIRE
+<,,
~ET13CT10N DIsTANcE

DETECTION
9
DISTANCE
DF-2 0.30+ x 0.305 m (1 x 1 ft) pan 9 m (30 ft)
Gasoline 0.30$ x 0.305 m (1 x 1 ft) pan 13.7 m (45 ft)
F-4 0.30$ X 0.305 m (1 X 1 ft) pan 13.7 m (45 ft)
Methane 152 x 229 mm (6 x 9 in.) 7.6 m (25 ft)
sheet flame
Wood 0.30~ x 0.305 m (1 x 1 ft) 8.2 m (27 ft)
Courtesyof ArrntecJRagen,Inc. exposed ~ea
Figure 6-4. Edison@ W Detector Courtesyof Armtec/Ragen,Inc.
Tube I

6-2.2.1.2 ~lDetTronics AOP Ultraviolet Sensor by

!Detector Electronics
Detector Electronics produces a line of UV detectors that
use its pate~d tube, shown in Fig. 6-7(A), mounted in the
housing, sh~wn in Fig. 6-7(B) (Ref. 23). The Det ‘1’ronics
W detector cone of vision is shown in Fig. 6-8. These
devices respond to irradiation in the wavelength range of
0.185 to 0.2/15 ~m. Shown in Fig. 6-8 are the count rates—
in counts pe~ second (cps)-for distances at which standard,
i.e., 0.3- x 0r3-m (1- x l-ft) pan, gasoline flames are set for
calibrating the device. The sensitivity of this device to a gas-
oline flame ~ shown in Fig. 6-9.

‘::---acat”o
Courtesyof Arrntec~agen, hzc.
Figure 6-5. Omnieb!lodel 652 Ultraviolet
Fire Detector

(A) Sensing Tube

UV SensoI
Outical .--’

u UV Radistion]
From Fire ,,
IMana, m (H) Madmum MUM N@?,
den
*
3.(U (lo) \io

7.e2 (25) 140

24.2S (w ! 10
Window
22.s3 (110) w

20 k
36.57 [l’xl)
Reprintedwithpermission.Copyright0 DetectorElectronicsCorpo-
Courtesyof Armtec/Ragen,Inc. ration. :
Figure 6-6. Series 650 Fire Detector Horizontal Figure 6-7. Geiger-MueUer-Type Sensor (Ref.
Performance Envelope (Cone of Vision) 24)
6-12
 Downloaded from http://www.everyspec.com

MIL-HDBK-684

,: 6-2.22 Infkared Fire Deteetors

O The most commonly used detectors for combat vehicle

applications are the infrared (IR) detectors. In the past II?
detectors have been unsuitable for general applications due
to the number of R radiation sources that can be found in
. nature and thus mate a tremendous false alarm problem.
‘..
Improvements in the ability {o discriminate between the
=.. radiation tim a fire and the radiation from other sources,
however, have resulted in the IR detector becoming very
reliable. IR is detected by either an optical sensor or a ther-
rnopilq thermopiks are desm”bed in subpar. 6-3.3. L Opti-
m cal IR detector systems normally use sensors that have been
designed to respond to a specific IR frequency. By adding a
a% second or third sensor element each tuned to a different fre-
quency and/or with a different filter, it is possible to
Reprintedwith permission-Copyright0 DetectorElectronicsCor- improve the ability of the system to distinguish ftre condi-
poration. tions from extraneous blackbody radiation. Since most non-
Fii = W Fire Sensor Cone of Vision (Ref. fire stimuli do not radiate in all of the spectral bands
m monitored, false alarm susceptibility has been greatly
reduced-
6-2.2.2.1 Dual Spectrum@ Infrared Sensors
The Santa BarbaraResearch Center (SBRC) Model PM-
Dstance,R 34 Dual Spectrum@ Discriminating JR detector monitors
~tl 20 m 60 W 100
, x radiatioq in two spectral bands to detect intensity above
preestablished levels and uses a third IR sensor to provide

,,
0
other fire signature information. The two spectral bands are
ones in which radiation is emitted by hydrocarbon fires but
not by most nonfire stimuli. The sensors will respond to an
explosive fire in 2 ms. (Ref. 27)
6-2.2.22 HTL Optical fire Sensor Assembly
The HTL optical l%e Sensor Assembly (OFSA), shown
in Fig. 6-10, combines two narrow band optical sensom,
one visible and one IR and a narrow thermopile. Two of dte
_ ..__-—..—.—— -—-——-—. —.— .. . ... .. .
. ... .
-----
\ /“-- ““

Distance, m

with pemissiou
Repinted Copyright~ Detector~ectroti= Cor-
pomioIL I

FiguI-e6-9. WDe@ctor Sensitivity toa Gaso-

line Reference Fii (Ref. 25)
The Det Tronics detectors have a standard self-test ele-
ment to establish whether the sensor is functional. This
fimctionality is primarily a matter of lens cleanliness. There
is also an optional device, a detector air shield, that catI
maintain a flowing air curtain over the lens to preclude
.,,,.,,,,, [
deposit of eomamina.nts. (Ref. 26) TWical response to an
intense W source is less than 25 ms. Systems are available Courtesyof HTIJKin-TechDivision.PacificScicndfic.
for applications in which response times of less than 10 ms Figure 6-10. Dual IR Sensor Plus a Thermopile
are needed. Sensor Assembly

6-13
 Downloaded from http://www.everyspec.com

MIL-HDBK-684

optical sensors are photodiodes with filters. One senses radia- ~Th~ough-the-Lens Checks
.-
tion at a nominal wavelength of 0.6 pm with a bandwidth of
AO.05Km, tie other at a nominal wavelength of 0.9 m with a
bandwidth of tO.05 pm. These two signatures establish a
sensed blackbody temperature which is used to discrim@ate
between fire and nonfire emanations. The them-m-pile has a fil-
ter, which views the radiation present at a nominal 4.3 pm with
a bandwidth of *0.5 pm and senses radiation from carbon diox-
ide. The HTL OFSA senses radiation in these three bands, pro-
cesses these data electronically, and signals when a fire
involving a hydrocarbon is present. It will detect explosions
within 2 to 4 ms from receipt of radia~on generated by a hydro-
carbon explosion. A fire-extinguishing system (Ref. 28) con-
trolled by this OFSA has passed both the discrimination and
fire detection tests in a live-fire system test and thus meets the
requirements of MIL-S-62546A. This HTL OFSA is used in
the M992 FAASV (Ref. 29). Analyzer

6-2.2.3 Corrnbirtation UV and Ill Detector Courtesyof ~tec/Ragen, Inc.

Combination detectors have been developed that incorporate
Figure 6-til. Combination W-lR Elaine lletec-
both IR and UV sensors; thus they discriminate between a
tir, Ch@p.m@ o Model 750 (Ref. 30)
nearby fire and sunlight or many other stimuli by requiring that
II
both heat and IR signature be present. The IR sensors are opti-
cal types or thermopiles. The IR sensor has a high signal-to-
noise ratio but reacts to background radiation. The thermopile IR

is not generally sensitive to X rays, lightning, or arc welding.

The UV sensors are usually Geiger-Mueller types. Because
each type of fire has its own unique signature and, therefore, a
distinctive ratio of W or heat and IR, most false alarm signals
can be screened out by making the combination detector sensi-
tive tot@ ratio of signals.
6-2.2.3.1 Ommiguard@ Model 750
Omnigwird@ Model 750 by Arrntec Fig. 6-11, combines a IR Detection
Region
UV sensor and a thin-film thermopile. The thin-fihn thermo- -+

pile, senses the narrow band of the carbon dioxide spike at an

O.@ 0,29 ~ 0,’4 0.8 4.3
approximate’ wavelength of 4.3 Lm, and the UV sensor senses Wavelength, pm
at a wavelength of 0.22 pm, as shown in Fig. 6-12, which is Reprintedwitd~pennission.Copyright@Armtec/Ragen,Inc.
above that of solar radiation reaching the surface of the earth.
These sensors provide an excellent means by which to discrim- Figure 6-12. Typical Hydrocarbon Fire Emis-
inate between fire artd solar radiance. Through-the-lens checks, sion Spectrum Showing Detection Regioms of
which provide a self-test capability, are provided for both the Omniguard@ Model 750 (Ref. 30)
IR and W sensors. The proprietary logic system Fire Event
Analysis (FEA) by Armtec is performed within the Omni- 6-2.3 APPLICATION
guard@detector assembly to ensure discrimination against non-
As discu~~edearlier in this chapter, a number of reliable,
fire radiation sources by establishing that the ratio of W to IR
efficient, mid quick-responding optical detectors exist for
is within the range representative of a hydrocarbon fire (Ref.
use in suppression systems for combat vehicles. The IR and
30). The typical overallresponse time is 150 ms for a saturating
UV sensorspre capable of responding in the few-millisec-
signal.
ond range. me E? sensor has the fastest response time of all
6-2.2.3.2 Spectrex Optical Fire Detector the sensor types, and its IR sensor response time should be
Spectrex provides a dual spectrum W and IR detector that in the 4- to 6-ins range. The necessity to discriminate
monitors a UV wavelength beyond that of solar radiation between e+ signatures can increase the response time of
reaching the surface of the earth and the II? wavelength emitted this sensing~system to a range of 9 to 150 ms with an aver-
by carbon dioxide. For a fire signal to be given, this IR racha- age somewhat greater than 30 ms (Ref. 32). All three types
tion must have flickers (Ref. 31). This detector can signal a of detectors are susceptible to certain extraneous stimuli; 9
hydrocarbon fire in 5 ms.

6-14
 Downloaded from http://www.everyspec.com

MIL-HDBK-684
thusthey can gjve false alrmns. The IR and combinationUV field of view must be changed to avoid that object. Redun-
and Et detectors can be designed with built-in tests or co be dancy of sensor coverage must be provided to assure com-
O
,!,
.’,
checked manually. Of the three types of detectors, the comb- plete coverage given nomxd operational failure of, or battle
ination IR and W has the lowest fake alarm rate. The damage to, individual sensors or their wiring. ‘he number
multiple lR detector also has a low false alarm rate. of sensors used in combat vehicles varies considerably. See
The disadvantages of the optical detectors follow: Fig. 6-13 for sensor locations in the Ml MBT engine com-
1. Susceptibility to opaquing of their windows by oil, partment and Fig. 614 for the locations in the BFV crew
dirt, and other contaminants. (During travel-worthiness tests compartment.
of the A.FES pkmned for use in the M60A3, the engine com-
pmtment optical sensors had to be cleaned after a mean of
82 km (51 xniles) of travel. The minimum distance traveled
before dust opaqued the lens was 14 km (9 rndes). For opti-
cal sensors mounted within the crew compartmen~ the
mean travel distance before cleaning was necessary was 137
km (85 miles). The minimum distance was 16 km (10 miles)
(Ref. 33).)
2 Restricted fields of view, particularly in engine
compartments or other crowded compartments 1
*
3. Selective absorption of emr by smoke, vapors, and t
other airborne materials, which reduce radiation intensity. I
I-
The most commonly used type of detector in US ground I
combat vehicles is the dual IR detector, such as the Dual L . ---- \\ -_——— —

Spectrum@PM-3C detector. l%e Ml MBT uses the PM-3C -k- P’%

dual spectrum IR detector. The M2M3 Bradley fighting
HMdqm?f ‘ExkaiwMallalR$msa
vehicles and the US Marine Corps (USMC) amphibious
assault vehicle (AAV)7A1 (Ref. 34) use the PM-34C dual Figure 6-13. Fire Suppression System of the Ml
spectrum Ill detector and the necessary electronic controls

o
MBT Engine Compartment (Ref. 35)
to sense a fire and dispense halon fire extinguishant. Most
currently produced LJIV-25s, but not those of the USMC
use a Dual Spectrum@PM-34CBEH optical LRdetector with
a discrimination feature.
623.1 Number Required
The mrmberof optical sensors required is governed by
the field of view and range of each individual senso~ the
space to be monitored, masking of space by objects, and
location of extraneous radiation sources within the cornpart-
men~ needs for redundancy of coverage; and potential
sources of obscuring materials within the compartment.
Each sensor has a specific field of view and range, an
example of which is shown in Fig. 6-6. Both of these char-
acteristics are built into the sensor optics, and these optics
may or may not allow adjustmerm The range is vitally TtnnMe&ated
important if the fire &tection system is expected to distin- VaiVeard SUn&

guish between “smtdl” and “large” fires. The space to be

Valwardaanie
covered has to include not only the locations of combusti-
ble-fluid-containing objects but also the locations combusti- IlltwicuMl
ble liquids can spray or flow and collem When the view of
some iocation that cart contain combustible ffuids is masked EXteliorP@
by some objec~ another sensor maybe required to cover tbe [:
masked area Also some provision must be made to dissetn- Lsefsa
inate materials or gasesthat can reduce the sensitivity of tbe

,.,
0
sensorsand thereby rtxiuce their range of coverage. When
an object that can emit radiation in the wavelength to which
the sensorwill respondis located within the field of view of
Colutesy of FMccorporation.
Figure 6-14. Fire Suppression System for Al and
A2 blf@I%itiOllS of BFVs M2 and M3
a specific sensor, either the object has to be masked or the

6-15
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MIL-HDBK-684
6-2.3.2 Location Selection tors are thermocouples or thermistors, but there are also
The same factors that govern the murnber of sensors to be pneumatic devices and resistance thermocouple detectors
used affect selection of the locations of the sensors. Loca- (RTDs). The relative ranges and gains of most of these are 9
tions are selected also to minimize cleaning and maintenance shown in Fig. 6-15. The thermistor has the highest gain, and
efforts, potential ballistic damage, contamination of the win- the thermo~ouple, the largest range. The RTD is in between.
dows and/or obscuration, effects of hot spots, and exposure II
6-3.1 CONTINUOUS THERMAL DETECTORS
to potential sources of fake alarms.
Several hfferent continuous thermal detectors (CTDS)
When selecting mounting locations, the designer must
me used in !~firedetection systems for combat vehicle appli-
assure that all potential fire locations are covered. The M 1
cations. ,These detectors include the thermistor, thermocou-
MBT requirements specified that detectors must view a n@-
ple, eutectic salt, and pneumatic types. These detectors are
imum of 95% of each compartment. In the initial design of
normally used to protect engine compartments. The contin-
the fire detector coverage for the M 1 MBT, three sensors
uous fire detector is a long capillary tube filled with a tem-
were placed in the engine compartment. The air intake and
perature-sensitive material, and it senses a temperature
its large filter were not considered vulnerable to a hydrocar-
change along its entire length (for overtemperature)--called
bon liquid fire and therefore were not covered by the sensor
“averaging” mode—and/or somewhere along part of its
arrays. Unfortunately the designers did not consider that
length (for flame or spot temperature)-called “dkcrete”
these filters do an excellent job of removing hydrocarbon liq-
mode. The sensor tube can be strung about the hazardous
tids from the air passing through and that after a period of
area, such as inside the engine or cargo compartments of a
time these combustible liquids accumulate therein. There
vehicle, so pat it is highly likely that the heat generated by a
have been several instances in which such accumulations led
fire would ~ansfer through at least some portion of the sen-
to sustained fires in these filters. Subpac 4-2.3.2 records’such
sor tube. Mpst CTDS provide an analog electrical signal, but
an incident.
the pneumatic detector furnishes a pressure that is converted
Specifically, the field of view of a sensor should not be ori-
to a digital electrical signal at the connection to the control-
ented through opened hatches. During the development test
ler. Signal ~onnectors are normally provided at each end of
program, a sensor was mounted in the M60A3 driver’s com-
the sen;or tube. These detectors, except for the pneumatic
partment so that when the hatch was open and the main gun
type, are generally .connected in a loop with each end being
fired, the sensor would falsely alarm. To solve this problem,
connected to the control unit, which monitors the thermally
a visor was placed over the sensor to obscure its view of the
responsive ,property of the sensing element. If the loop is 9
main gun (Ref. 36). During the development testing of the
severed, boih sections can still function. The following sub-
AFES for the Ml MET, a false alarm was caused by the
paragraphs ~present brief details of the operation of each
muzzle flash from a nearby gun (Ref. 29).
type of thermal detector.
Sensor locations should be selected and reviewed when
the vehicle has all contents fully stowed and all crewmen
present so that all obstructions are identified. Also sensors
should be placed high within the compartments so that added
objects will not obscure their view.
6-2.3.3 Standardization
The objectives of standardization follow:
1. Reduction of acquisition costs by obtaining a large
quantity of a single model
2. Reduction of replacement stockage requirements
3. Reduction of training requirements
4. Reduction of mainten~ce and repair labor’
5. Enhancement of the capability to replace existing
units with newer units that have upgraded capabilities.
he technique used to stattdardlze fire detectors is to
establish a single, standardized mount design, which is a
common size and uses a standard fastener. In addition, a sin-
gle, common electrical power and signal connector with !I
Temperature T
standardized signals and pin assignments must be used.
Reprinted w~$h permission.Copyrighto Hewlett-PackmdCompany.
6-3 T~1311NlAL D13TECT01ZS
This paragraph introduces thermal fire detectors that can Figure 6-15. Comparative Outputs Versus In-
be used in combat vehicles. Brief introductions of the actual puts fo$ Thermistors, Resistance Thermo-
types of thermal detectors, including continuous thetmal couple ~etectors (RTD), and Thermocouples a
detectors arid thermocouples, are given. Most thermal detec- (Ref. 37)
6-16
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MIL-I-IDBK-684

6-3.1.1 Types Another version of a continuous thermistor cable (Ref.

o 6-3.1.1.1 Thermistor-me Continuous Detector

The thermistor-type detector has a capillary tube filled
with a semiconductor or thermistormaterialin which one or
39) uses a family of manganese oxide thermistors to provide
sensors that operate in the six different temperature ranges
shown on Fig. 618. In a thermistor-type detector system, a
control unit monitors the resistance and signals the alarm
more electrical conductors are embedded. I%e material, when tie resistance drops to the preset value that come-
which has a negative temperature coefflcien~ reduces the sponds to the predetermined alarm temperature. Became the
ektritxd resistance between the conductors when it is element is essentially art infinite number of thermistors in
heated and increases dte resistance when it is cooied. Fig. 6- parallel, the resistance of the system is a tlmction of the
16 shows a thermistor-type continuous detector called length of element heated and its temperature. The output is a
Firewire@(Ref. 38), which is used in fire detector systems nonarithmetic average temperature indication weighmd to
for engine compartments. This detector is manufactured for the high-temperatureareas. Even if the cable is severed,
three basic temperature ranges by varying the filling rnate- such a Ioop system is still able to sense temperature
nal (and for intemtediate temperatures for customized increases because each end of the cable is connected to the
installations) and will react to temperatures as indicated in control ttnit.
Fig. 6-17. Fmwire@ not orIly senses changes in resistance
bat also changes in ctqmcitwtce, which increases as temper- Ioe 1 I I I
ature increases, to make it less susceptible to false alarms. r
The connector design includes a hermetic seal to eliminate
cxmtamination by dirt and/or moisture.

0
,!,

-Typa2

outersheath ‘Type3
Reprintedwith permission.Copyright@Kidde4raviner Ltd.
-Type4
Figure 6-16. Graviner Firewire@(Ref. 38)

10’
m
s
o,~
1 L
0 200 400 am 800 1000
mo msmosm
I@ritued with permission.Copytight0 ArtntedRage&Inc.

0,,
MatedEta7rMLangttt,
mm
Reprintedwith permission.Copycighto Kidde-GtavinerLtd Figure t$-1~ Family of Curves From Armtec
Figure 6-17. Typical Ternperatum Ranges for Continuous Thermistor Sertsor IUememts (Ref.
Graviner Fnwires (Ref. 3$) 39)

6-17
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nmlL-HDBK-684

6-3.1.1.2 Continuous Therrnoeouple Cable alumel wires are embedded in a closely packed ceramic
The continuous thermocouple transducer cable shown in powder that has a high negative temperature coefficient.
Fig. 6-19 consists of a protective stainless steel outer sheath When heat is applied to the sheathing, it is transferred to the a
within which chromel and constantan wires or chromel ~d packed cerdmic powder insulation, the electrical resistance
of this insujmion decreases so that temporary thermocouple
junctions ~e formed at “hot spots”. The outpttt of the hot-
test signal; the temperature. When the heat source is
removed, the cable returns to its original state. This cable
generates a millivolt output proportional to the highest tem-
perature.in contact. The cable is not damaged by exposure
to a temperature up to 899°C (1650”F) and has a nominal
low operating temperature of O“C (32°F). The sheath of the
cable has aiI expected life of 20 years, The weight is 0.037
kg/m (0.4 oz.lft). The minimum bending radius is 12.7 mm
(0.50 in.). The output voltage is +0.6 mV dc at O°C (32”F)
(A) Type 100 to +68.7 my dc at 899°C (1650”F) (Ref. 40).
6-3.1.1.3 ‘ Eutectic Salt Continuous Detector
The eutectic device, as shown in Fig. 6-20, has the capil-
lary filled ~ith porous insulators impregnated with a eutec-
tic salt that melts at the desired alarm temperature (Ref. 4 1).
When the @lt melts, it conducts electrical current and
becomes a low resistance path, and it changes from a very
high to a vety low resistance over a very narrow tempera-
ture range. & alternating current potential must be used to
operate the detector element because direct current will
cause met~lic plating to deposit on the insulator and result
(B) Type 200 ‘ in permanent shorting of the detector. The melting salt cre-
9

(C) Type 300 ~

A= Negative Conductor
B = Positive Conductor
C= Inner Sheath
0 = Outer Sheath Wi
G= ‘C’ Wall Thckness ic
tp= “DmWall Thickrtess
N = Negative Temperature Coefficient lnsutaiion
O = Mineral Oxide Insulation
T= Teflonm Overcoat (Optional)

Sh@t#
Reprintedwith permission.Copyrighto HTL/Kin-TechDivision,
PacificScientific. Reprintedw@ pertnission.Copyrighto Walter KiddeAerospace,
Inc. ‘
Figure 6-19. Continuous Thermocouple Cable
(lRef. 40) Figure 6-20. Eutectic Sensing Element (Ref. 41)

6-18
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MIL-HDBK-684
mes a very sharp switching action; therefore, the detector the metal. The hydrogen remains adsorbed on the titanium
opera~es at a discrete temperature, which is virtually unaf- until it is heated above a critical &sorption ternperaw,
fected by the length of the eIernent being heated. This then it will outgas heavily and provide a “discrete function
device is essentially a fixed-temperature device that is non- mode”.
avemging, i.e., the eutectic salt detector is discrete mode There are many designs available for different all point
functioning only. Kidde-Graviner has a family of eutexxic and discrete settings depending on the exact requirements of
sensors developed for nominal alarm values from 102”C a specific installation. Fig. 622 is a spectic example of a
(21ST) to 332°C (630*F); there are presently 12 alarm tem- perfonmnce tune for a typical fire detector used in the
peratum. This manufacturer also has a hybrid. detector, engine compartment of commercial or military aimaft.
which combines the eutectic and thermistor features. When the entire detector is heated to 260”C (500’’F), the
pressure in the sensor increases to approximately 345 kPa
6-3.1.1.4 Pneumatic Continuous Detector
(50 lb/in.V, which closes a switch that signals an alarm con-
Two variants of the pneumatic overheat and fire detector,
dition. If a much shorter length of sensor tube, e.g., 152 mm
one of which is shown in Fig. 621, consist of a sealed stain-
(6 in.), were heated to 538*C (l OOO°F’), sufficient hydrogen
k.ss steel tube, or capillary, pressurized with helium, that
would be released to provide the same internal pressure in
contains a titanium wire saturated with hydrogen and
the sensor, and the alarm would also be signaled. A void
wrapped in a molybdenum spiral (Ref. 42). When the entire
space is maintained between the outgassing material and the
sensor tube is subjected to low-level hea4 the helium
capillary wall by a spiral wrap of molybdenum. ‘llte spiral
expands ad thus increases the internalpressureof the tube,
wrap on the titanium core wire provides a passage for the
which uiggers the overtemperatureahum for an averaging
helium andhr hydrogen if the outer sheath collapses onto
function mode, also called the “all point” mode. This pres-
the core when fiattened or crushed during twisting, bending,
sure is dependent on the volume of gas heated and thus
or mishandling. This wrap makes the sensor tube resistant to
directly on the length of element heated. As a resulh the
the wear and handling it would experience in the fie~d(Ref.
detector will provide an arithmetic average of the tempera-
42). When outgassing occurs, a pressure buildup is transmit-
tures of the element. Lengths of this detector cannot be con-
ted along the capillary to a pressure switch at one end,
nected in series as some of the other continuous detectors
which then signals the alarm. Once the detector has had a
can, so these detectors are generaily built to a specific length
chance to cool, the hydrogen is readsorbed in the titanium.
for an application. If more than one detector is desired in an
‘Ihe reduction in internal pressure allows the alarm switch
are% they are wired in parallel. llte core material is a
to return to its normally open position and thereby rearm the
sefected metal hydride, which will desorb into hydrogen and
Ch2iL I%e volume of actual outgassing of the hydrogen is
—-. —. . ...d.._.
so great that it is almost independent of the length of the ele-
ment. A digital output is provided by the responder end of
this assembly, which contains two snap action diaphragms.
The set pressure within the sensing tube is 111.5 to 192.6
I&a (16.17 to 27.93 Win?). One diaphragm is attached to
the akwm switch, which closes normally open contacts
when subjected to an internal pressure of 241 to 586 kPa (35
to 85 UYkt.y, depending on the set alarm poinL l%e other
diaphragm is attached to the integrity SWML which opens
normally closed contacts when the internal pressure drops
below 110 to 193 kPa (16 to 28 lb/in.2). T%eintegrity switch
signals the crew when the pneumatic themml detector is
inoperable. Tltese switches cannot be readjusted after the
detector leaves the factory. The reaction points and the
detector response are established by flame test to be within
specifications before the detectors are delivered. The sensi-
tivity will not change even though the set point could shift
slightly. This sensor is subject to malfunction if the capillary
is ruptured. This failure could be a loss of integrity or a
reduction in the sensitivity of the sensor, such as could
occur given a balhstic perforation that results in a small hole
in the sheath.
ML-F-7872 requires a iire signal when 150 mm (5.9 in.)
Courtesyof SystronDormer.
of cable is exposed to a flame at I IOO”C(2012°F). A pneu-
Figure 6-2L Sysmm Dormer Model 808-DRV matic detector can be set to provide such a signal and has
Pneumatic Continuous Detector done so in 5s.
6-19
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MIL-HDBK-684

Alarm
Switch~ “ InertHeliumGas
(Cksses) \
d 7
50 ~,
g
OvettwJal
(Aveiage)

ActiveI-lydrogeh
CoreGas
Fd\(Dmete)
/ Tvdcal
138 Neahiiardws
Operating—
Integrii Cendtion
Switch
(RemainsClosed)
a —
-54°C ‘c 538Qc
(-yyq (500”F) (looo”q

Exposure Temperature, ‘C (“F)

Reprintedwith permission.Copyright@SystronDormer.

Fi@re 6-22. T~ical Pm+unatic %msor Performance Curve (Ref. 42)

Tlis pneumatic sensor can be fabricated to have its dis-

crete function occur over other temperature ranges, and the “ ~ ,
values shown in.Fig. 6-23 are the approximate temperatures “6
required to generate an alarm for given exposure length.
They are not intended or implied to be a specification (Ref. ~ ~
43).

6-3.1.2 (lenerid Characteristics of Continuous ii-

‘l%emal Detectors
‘ 100!:,,,,,,:
;
6-3.1.2.1 Response Time :1
o
The response time for all CTDs is long in comparison to 0 \l 1 2 3 4 :
opticaJ detectors, which respond in milliseconds. In tests “of 1
two therrriistor-type (Systems A and B) and one therrnocou- EqxwureLertgrh,
m
pie-type (System C) CTD of the fire detection and extin- Reprintedwitk persnission.Copyrighto SystronDormer.
guishing system of the Small Unit Support Vehicle (SUSV)
F@.we 6-23. Typical 6-m Long Pmeurnatic
M973 (Ref. 44) in which a propane torch was used to apply
heat to a short section of the sensor cable, “the responses in Detecto$ Performance (Ref. 43)
three trials were System B: No alarm, 44s, and 34 s
2.
1. System A: 82s, 28s, and 26s for a mean of 45s 3. Sys$m C: 32 s, 24 s, and 24 s
2. System B: 18s, 18s, and46s foramean of 27 s 4. System D, a pneumatic-type CTD: No alarm, 48 s,
3. System C: 24s, 18s, and 16s for a mean of 19s. and 32 S.
In some engine burn tests in that same program, the See subpar;, 6-3.1.1.4 for discussion of pneumatic-type
responses in three trials were C’I’IJSand subpar. 6-3.1.3.2 for more information on this 9
1. System A: No alarm, 46s, and 34s test progmq.

6-20 ,1
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MIL-HDBK-664

6-3.12.1.1 l%errrtistor-~e Detector later traced to an improperly designed mounting device.

o Because the thermistor cable must increase in tempera-

ture before alarm output will be generatetL thermistor detec-
tors have an inherently long response time. The typical
%%.hinstallation of propdy designed clamps and Teflon@
insulators, the problem has disappeared. (Ref. 45).
6-3.122.1 Tkrmistor-ljqw Detector
rwsponse time for a continuous loop thermistor detector is
A detector system that senses resistance and signals an
about 5s; a 30-s response time is not unusual (Ref. 38). alarm when the resistance drops below a preset value is sub-
6-3.1.2.1.2 Continuous Thermocouple Cable ject not only to failure but also to giving false alarms if the
The time constant-i.e., the time required to reach 63.2% detector element becomes shoned. Such a short could result
of the final voltage for the temperature sensed-of the con- fiorn impact by a shaped-charge je~ KE projectile, fiag-
tinuous thermocouple cable is comparable to a conven- tnen~ span, or chafing during normal opemtions. Dirt and/or
tional, ungrounded thermocouple of the same diameter. This moisture in connections is also a major potential cause of
would be a shielded thermocouple with a sheath diameter of false alarms. To eliminate the problem of false alarms, a dis-
2.5 mm (0.1 in.). The time constants graph in subpar. 6- criminating circuit is used in rhe control system which wiIl
3.2.2 indicates an approximate time constant of 10s for a test for a short circuit condition and, given such a condition,
bare thermocouple with a sheath diameter of 2.5 mm and a will prevent the fake ahmrt.. Typical discriminating circuits
time constant of 15 s for a shielded thermocouple with a currently used not only will prevent a false alarm but also
sheath of the same diameter. will conven the false warning mode of failure to an “inoper-
ative” faihue signal.
6-3.1.2.1.3 Eutectk Salt Detector The Firewire” (Ref. 38) system provides two parameters
In a flame test the response time of this type of detector for fire detection. In a fire condition, the resistance between
would probably be faster than that of the thermistor-type the central electrode and the sheath drops, and the capaci-
detector (which is approximately 5 s) because the short tance rises. If the resistance and capacitance do not change
immersion length in the flame need not be tteated as high as simultaneously, the signal is treated as a false alwrn, and no
the averaging thermistor element. The response of a eutecric extinguished are activated. The electronics provide a built-
salt detector without air movement across the sheath versus in self-test. lf the resistance is out of tolerance, a fault is
temperature is shown in Fig. 6-24. indicated, and fire signais are ignored until the fault is cor-

0
.i 6-3.1.2.1.4 Pneumatic Continuous Detector
A typical pneumatic detector responds to a 152-mm (6-
in.) ion-gthe&ml input at 11OO°C(2000W) in 5s. Once the
rected. This setup assures positive fire detection and dis-
crimination between a fire and a fault. If both ends of the
cable are connected to the controller when tie cable is CUL
t%esource has been removed, it will return to a normal con- each segment of the cable remains functional.
dition in appmximatcdy 30s. (Ref. 42) 6-3.12.2.2 Continuous Thermocouple Cable
63.1.2.2 False Alarm Rejection The continuous thermocouple cable is subject to false
The causes of frdse alarms for each type of CID are dis- alarms when electric currents are induced in the wires.
cussed in the following subparagraphs. The methods used to Since the wires are installed within a stainless steel sheath,
Educe false alarms include elimination of the causes, use of the probability of inducing electric current in the wires is
discriminating circuits, and redundant systems. low. Cutting the cable by ballistic action can be readily
The potential sources of false alarms for CfI)s are noted by loss of continuity; however, cutting the wires or
objects that become hot in use, such as the combustor a of shorting them does not render the thermocouple inoperative.
the turbine engine of an M 1 MBT or the exhaust manifold Also, if both ends of the cable are connecmd to the conrrol-
of a died engine. ?lte CTDs should be routed so they are Ier, each segment of the cut thermocouple cable remains
not in contact with or ciose enough to be affected by hot fictional.
spas and maintenance personnel should be conti-nuously 6-3.1 .2.2.3 Eutectic Salt Detector
alert to assure &al the CTDs are not inadvertently moved to The eutectic salt detector is prone to false alrum problems
such locations. when it is shorted. The ekxronic control monitors the resis-
In general. all continuous rhemtal detectors rely upon tanc~ and a low resistance condition is interpreted as a fire.
convective heat transfer for averaging functioning and upon Since the rate of resistance change of the melting salt
flame transfer for discrete fimctioning. They must be approaches that of a short circuit, distinction between a
located where flames can reach them, or the fire will not be short circuit and a fire condition is difficul~ Consequently, a
detected expeditiously. With CTDs, failure to alarm is as shon circuit discriminator becomes quite complex, and dis-
great a problem as false alarms. The ekcrnc CTD used in crimination may be unreliable. False alarm problems can be
the A-10 aircraft reportedly failed due to shorting and/or reduced by the use of redundant detector loops, which
chafing of the thermal cable. Sixty-seven of 87 unscheduled inherently provide electrical short circuit discrimination and
maintenance actions on the fire detection system were thus reduce the need for actual discrimination circuits.
reported to be due to that cause. This chailng problem was

6-21
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MIL-HDBK-684
of even a short portion of the cable length results in a con-
W
-1 siderable inverse change in overall resistance (Ref. 37).
Loss of sensitivity in a thermistor-type CTD can be due to
moisture collecting within the electrical connector. This a
type of los~ can be prevented by having an effective seal in
the connec~~r. In some cases, use of lug comectors with a
proper loc~ng device on the fastener assures a good electri-
cal connec~on. Sensitivity can be maximized by selecting a
CTD with the greatest gain at the temperature selected for
system activation.
6-3. L2.3.2 Continuous Thermocouple Cable
Temperature,“C
The sen#ivity or accuracy of the continuous thermo-
couple cable in detecting a desired temperatureis*14 deg C
Reprinted with permission.Copyright0 WalterKiddeAerospace,
(t 5 deg F); The repeatability is kO.6 deg C (+1 deg F) after
Inc.
thermocycle to 538°C (1OOO”F),and the drift is similar to
fi~~e 6-24 Typical Eutectic Response Times that of a mineral-insulated thermocouple.
W~thout Air Movement Across Se~ors for a“ In a series of tests for the SUSV program (described in
Specified Alarm Temperature of 2Q4° C subpar. 6-3.~1.3.2) to establish the effects of contaminants in
(4W”F) (Ref. 41) the electri~~ connections of a continuous thermocouple
cable, the q~ntarninants tested did not affect the capability
6-3. L2.2.4 Pneumatic Detector of the cable connected to the controller to signal a fire or
The pneumatic detector is prone to false alarms only cause a fal~~ alarm. The contaminants tested included dis-
when the electrical interface wires are shorted to each other tilled wate~i tap water, saltwater, Jet A-1 fuel, antifreeze
without shorting to ground by saltwater, moisture, or other (50% ethylene glycol and 50% water), and dirty grease,
conkinants. The’ detector design has minimized such Only when ~ere was so much contaminant that the thermo-
problems with contamination. The only other way a false couple-conpoller circuit was incomplete and an open circuit
alarm could be generated would be to short the electical signal was !Icaused was the fire detection system affected
power to the alarm circuit. (Ref. 46). ~
9
6-3.1.2.3 Sensitivity 6-3.1 .2.3.3 Eutectic Salt Detector
The sensitivity of the various types of CTDS to fires and This type,of detector requires that when the eutectic salt
fire stimuli is discussed in the subparagraphs that follow. A melts, it operates as a conductor with a low resistance path
common cause of degradation of sensitivity for all CTDS is and, in effect, acts as a switch that can change from a very
for the cable or tube to become coated with a mixture of oil high resistance to a very low resistance over a narrow tem-
and dust, which can reduce heat transfer to the cable or tube. peraturerarigeof approximately 6 deg C (10 deg F).
This reduction of heat transfer increases the time required !
for the sensor to heat. This problem is alleviated by proper 6-3.1 .2.3.4 Pnemnatic-’&pe Detector
cleaning and maintenance. Another common cause of sensi- The pneumatic continuous detector has both an averaging
tivity degradation is moisture or other contaminants in the and discret~ mode of operation. In the averaging mode the
electrical connections. This contamination can be prevented detector h~, a fixed volume containing pressurized helium.
by proper sealing of the electrical connectors. A third poten- If @e press~e exceeds a desired value, a diaphragm snaps.
tial cause for sensitivity degradation is a CTD installed too The sensitivity of the detector in the averaging mode of
low in an engine compartment so that liquids collected in operation is governed by Charles’ and Boyle’s laws in
the bilge contact the CTD. The corrective action for this which the volume is constant, or P2/Pl = T2/TI. Therefore,
problem is to itistall the CTD high enough so that increased there is a linear change in pressure P with a change in tem-
levels of bilge liquids or sloshing of liquids cannot contact perature T For the discrete mode of operation, the increase
the cable or tube. in pressure depends upon the resorption of hydrogen from
titqnium h@-ide, which starts at approximately 399°C
6-3.1 .2.3.1 Thermistor-Type Detector (750°F). The snap point of the diaphragm can be adjusted to
Thermistor-type detectors respond to temperatures any- AI 070 of the desired temperature.
where in the range of 124 to 1093”C (255 to 2000”F). The
thermistor material is selected for the temperature at which 6-3.1.2.4 ~Durability
the detector is to operate, and the temperature thresholds for All of the CTDS currently available are designed to be
alarms are individually preset. When this temperature rugged and corrosion, vibration, and shock resistant. Some
threshold is exceeded, the alarm is triggered. The gain on detectors u~d in milita-y equipment have already demon-
strated theq capability to meet the environmental require- 0
thermistors is quite high, as shown in Fig. 6-15, so heating
ments found in military specifications,
1
6-22
 Downloaded from http://www.everyspec.com

Some of these CTDs have been used in akraft long opened very quickly after the fire was removed tim the

o
‘, enough to have established a rnean-time-between-hilure
(Ref. 45). For an 1l-yr period from 1972 through 1982+the
pneumatic detector of Ref. 42 showed a mean time between
tube, but the integrity switch remained cIosed and indicated
appropriate pressure for 12 min. The switch would have
remained closed longer if the sheath had not been cm t%r-
false alarms of 803,800 h for single-loop pneumatic systems ther by the test personnel (Ref. 49).
installed on Boeing 727 engines. TM same detector has
logged over 200 million flight hours in military aircraft with 6-3.1.3 Application Suitabfity of Continuous
an average mean-time-between-failure in excess of 100,OUO Thermal Deteetors
operating hours (Ref. 45).
The pneumatic CXD has a characteristic that is unlike any 6-3.1.3.1 CTD Installation
of the other types of CTDs: It is dependent upon trapped Because thermal detectors do not have as fast a response
gases to expand or desorb in order to generate the pressure as the optical detectors, they are not well-suited for systems
that provides a iire signal. Thus losing integrity of rite smt- designed to extinguish flash fires, such as combustible liq-
sor tube should affect its capability to function. To wam the uid spray fireball fires in crew compartments. For vehick.s
crew when the sensor tube loses integrity, i.e., loses its designed to preclude the occtmence of hy&ocanbon liquid
internal helium pressure, an integrity check is provided. spray fireballs (discussed in Chapters 2 and 4), however,
When tbe internal pressure drops below its nominal 34.5 CTDs could be appropriate for crew compartments if over-
kPa (5 psig), a snap action diaphragm snaps open and temperature is the primary concern. CTDS are also ideal for
causes a warning lamp to light. installation where there is a very high ambient temperature,
ME-F-7872 (Ref. 47) requires that where detachable a dirty environmen~ and a risk of fiuid spills and where the
sensing elements of a control unit break, the break will not equipment can withstand flash fires, such as in the engine
cause the system to become inoperative and hat if one or compart.metm Continuous thermal detectors can be routed
more breaks occur, those pornons of the sensing element away fkorn I@-temperature equipmen~ such as tiine
still connected to the control unit shall retain the ability to engine combustor cans, to avoid the false alarms caused by
detect and signal a &. Other requirements in Ref. 46 those objects. Detector cables can also be strong about the
hazard area and across the airflow patterns so that it would

,,.
include that such breaks will not cause false &mns. To

,,,
O
establish that the pneumatic CTD meers these requirements,
a series of tests (Ref. 48) in which breaks were made using
five different techniques was conducted:
be highly unlikely for a fire to exist and not have the result-
ing hot gases come in contact with the thermal detector.
Thermal detectors such as the Gravinefl Fwewire”, which is
1. Cutting the sensor tube with tube cutters a semiconductor thermistor type of detector, and the Sys~n
2. Shearing the tube with diagonal-cutting pliers Dormer pneumatic detector are routinely used in the engine
3. Severing the tube by impact with a 7.92-mm bullet compartments of combat vehicles. These detectors are
4. Shearing the tube with a hammered blunt rod routed within the engine compartment and in conjunction
5. Flexing the tube until a fatigue failure occurred. with their associated control electronics and fire extinguish-
All of these severing techniques tended to close the ers create V- efficient and responsive fire suppression sys-
sheath and obtained at least a partial seal, which was mini- tems. Fig. 6-25 is a schematic drawing of the Firewire*
mal for flexing to fatigue, but these techniques simulated detector, control electronics, and the fire suppression system
most of the damage that this sensor tube would be expected as installed in a typical combat vehicle.
to receive in combat or normal operations. Tlte blun~ high-
speed penetratorand the shaped-chargejet were almost sim- 6-3.1.3.2 Comparative Tests of Several CTDS
ulated by the flexing-to-fatigue failure because for that fail- The US Army has lost nine M973 SUSVS to fires, most of
ure the sheath did not effectively block the gas flow passage which occurred in the engine compartment. By the time the
(Ref. 49). occupants realized there was a fire, the fire had developed
These tests did not show that punctureof the sensor tube too far to be extinguished with the onbo@ portable extin-
results in loss of the averaging function, but the crew did guishers. A series of tesrs was performed at the US Army
receive warning that tube integrity was lost. On the other Cold Regions Test Center to evaluate candidate fire.detec-
hand, these tests indicated that if the sensor were severed, a tion and extinguishing systems for the M973 SUSV (Ref.
fire could be sensed if it contacted the tubing at least 305 44).
mm {12 in.) from the cut. ‘Ilk phenomenon is due to the The systems furnished for this program included three
great quantity of hydrogen desorbed shortly after a high- thwtnistor-type CTDS, one thermocouple type, and one
temperamre flame contacts the tubing. The sensor would not pneumatic type. All five of these sensors can function with a
be My operational, i.e., it would signal a fire, and that sig- discrete mode, and all except the thermocouple cable can

0
nal would be lost after the hydrogen leaks out through the function in an averaging mode. Generally speaking, the
cut. This leakage of hydrogen, however, can take consider- thermistor- and thermocouple-type sensors obtain their dis-
able tirnej as was demonstrated by the tests in which the
*lJse of the fabricator’s - does not constitute Government
tube was cut with a hammered blunt rod. The alarm switch endorserneruof the products.
6-23
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NllL-HDBK-684

4. CTDS should be rugged enough to prevent electrical

shorts of the CTD circuit if the cable is accidentally twisted.
5. Thedesign of the mounting system is very critical.
6. Exc~ssive slack in the CTD cable can lead to break-
age (Ref. fi).
Another lesson learned is that more thorough guidance must
be given b~ designers when a fire detection system is
1, I Iu $ 1 Y needed. Pa&cularly, the desired temperature range in which
E CcOlm~ Mt — Dktnbuikm PiPewofk
the device is to function should be specified, or sufficient
@ IMinguMers --- FireWire*
information ,on the desired application should be given so
that the sensor system supplier can establish the necessary
Reprintedwith permission.Copyrighto Kidde-GravinerLtd. temperature range.
l?@.me 6-2S. Typical Firewire@ Installation in
Combat Vehicle (Leopard II) (Ref. 38) 6-3.2 T~RMOCOUPLES
crete function mode through the choice of the insulation A thermocouple is another thermal sensing device that
material between the core wire and sheath or between the can be used to detect a fire. Thermocouples are simple, rug-
dissimilar core wires. The pneumatic-type sensor obtains its ged, and inexpensive. They have a slower response than the
discrete function mode through the choice of core material other combustion- or temperature-sensing devices already
and the gas it adsorbs. Initially, all five of the detector sys- covered, but the response of a thermocouple can be fast
tems furnished were factory set to respond to a temperature enough to ~~otect an engine compartment. A thermocouple
better suited for a steel-hulled vehicle than for a fiberglass- is a point temperature measuring device unless a continuous
reinforced, plastic-hulled vehicle. Most of these factory set thermocouple cable is used.
systems were not capable of having the response tempera- 6-3.2.1 I/asic Functioning
ture changed, although one system, the thermocouple-type
In 1821 Thomas Johann Seebeck discovered that when
t2TD, was modified at the request of TACOM to provide the wires of di@rent conductive materials are joined and the
capability to readjust its response temperature ,set point. The
connected ~oint is heated, an electric current flows in the
SUSV fire detection”and extinguishing systems were tested wire circuit. ~l%isfact also means that if the circuit were bro-
for their response at a desired reaction temperature within ken at other than the heated connection, there would be a
the range of 204 to 232°C (400 to 450”F). Three of the sys- voltage across the open ends of the wires. All dissimilar
tems could function in the discrete mode or could be set to
metals exhi~it this effect, but certain combinations of metals
respond within the desired temperature range, and these
produce a @eater current or voltage than others given the
three systems performed superbly. The other two systems same thermal input to the connected point. This connected
could not be reset in the available time to function in the
point is called a thermocouple junction.
discrete mode within that temperature range. .These two sys-
Every connection of dissiinilar metal wires is a thermo-
tems did not perform satisfactory y because they were not
couple, but if connections are made at locations that are not
originally designed for this application, not because they
exposed to ~reat temperature variations or that are exposed
were incapable of adequate performance. After modification
to known or constant temperatures, only the purposely
of the set point temperatures, these two systems were
exposed thermocouple will produce the electrical output
retested and performed satisfactorily. significative of a temperature change. When a reference
6-3.1.3.3 Lessons Learned junction is ~dded to the circuit, the output voltage of the sys-
The lessons lek-ned from that SUSV program follow: tem is a thnction of the difference in temperature between
1, Discrete functioning is preferable to averaging the thermocbuple and the reference junction. Normally this
functioning for CTDS, and CTDS mw.tbe designed and fab- reference teihperature is that of an ice water bath, which is
ricated to function within the desired temperature range. O“C(32”F). ~Leadscan be attached to this thertnocouple-ref-
2. CTDS should not be installed in locations that erence junction array by using an isotherrmd block, which in
require significant labor to access for maintenance. In this essence provides two more thermocouples, the outputs of
case the engine had to be removed before the CTD could be which cancel each other. The ice water bath reference junc-
installed or removed. tion can be ieplaced with an electronic ice point, which pro-
3. CTDS, except for the Systron Dormer pneumatic vides a voltage equal to that which the reference junction
detectors*, should be grounded, and they should not have a would produce. The voltage produced by this combination
floating ground such as a sheath because accidental ground- thermocoup~e-reference junction and lead wire array can be
ing of the sheath can affect sensor performance. converted t$ a temperature by referring to a temperature-
input versus voltage-output relationship, which is peculiar
*The pneumaticdetectorsare at abovegroundpotentialand are not to the thermocouple materials used.
referenced to sheath ground. They are monitoreddifferentlythan
transistor-typeelectricalunits.
6-24
 Downloaded from http://www.everyspec.com

IIML-HDBK-684

,, 63.2.2 l’ilermocouple Types these types, so they should be used only with nonmetal
sheaths. Type T (copper-constantan) is recommended for
O The six most commonly used thermocouple material
combinations are shown in Thble 6-4, and the temperature-
voltage relationships for these six thermocouple types are
use in mildly oxidizing or reducing atmospheres and is suit-
able for use where moisture is present. (Ref. 37)
shown on F]g. 6-26. ‘Ilte thermocouple junction can be bare or shielded, as
Chrome] is an alloy of 90% nickel and 10%0chromium. shown in F~g. 6-27. Bare thermocouple junctious, shown in
Alumel is an alloy of nickel that contains approximately (Figs. 6-27(A) and (C), can be eifher butt-welded or beaded-
2.5% manganese, 2% aluminum, and 1% silicon. Constan- Shielded thermocouples can be either grounded to the
tanis a copper-nickel alloy that differs for the various ther- shield, as shown in Fig. 627(B), or insulated from i~ as
mocouple types. One of the constantan alloys is 55% copper shown in Fig. 6-27(D). The bare thermocouples have a
and 45% nickel. faster response but are more susceptible to damage than the
Tjqe E (chromel/constantart) may be used at tempera- shielded. When the shield is grounded, the thermocouple is
tures up to 871*C (1600’33 in an inert rnildly oxidizing or less subject to noise pickup. Shielded thermocouples have
reducing atmosphere. TWe E thermocouples are recom- time constants, i.e., the time required to reach 63.2% of the
mended for use in subzero applications. Type J @on-con- final output given 3 step chaage in inpug approximately 15
stantan) is recommended for reducing atmospheres only, times those of bare thermocouples. l%e time constant of a
and T~ K (chromel-alumel) is recommended for use in bare thenrmcouple is given versus the wire or sheath diame-
chmn oxidizing atmospheres. Types R (@atinum-platinm ter Din Fig. 628.
13% rhodium) and S (platinum-platinum, 10% rhodium)
have high resistance to oxidation and corrosion. However,
hydrogen, carbon, and many metal vapors can contaminate

TABLE 6-4. THERMOCOUPLE MATERIALS

(I&f. 37)

,,;
0, TYPE
E
J
Posm
Chromel
Jron
Constantan
Constantan
NEGAITVE

D
K Chromel Alumei
R Platinum Platinum, 13% Rhodium (A) (B) (c) (D)
s Platinum Platinum, 10% Rhodium BareWire Sttielded Bare Wire SM$ded-Tyjw
&At Welded G-
T Copper Constantan a~-TYP mrmocqe
Junction Thermocoucde
Sourceof informationOmegaEngineering Inc. Usedwith permis- O. diameier
sionof OmegaEngineering,Inc.. Stamford,Cl’ 06907.
Reproducedwirbthe pennksion of OmegaEngineering,Inc., Stam-
so foti m 06907.

1
TWIE

p d
i’ F@re
(Ref. 37)
6-27. ‘1’hermocoup!e Sensing Elements

{ ‘“r

o t I I

o F-6-26. ‘1’y@d Thermocouple Tempera-

ture and voltage Ranges @f. 37)
F-
o

(Ref. 37)
6-2$.
M=d or Wke Sl% Diameter,’;m
Thermocouple Time Constants
100

6-25
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!,.

MIL-HDBK-684 ‘

6-3.2.3 Application Suitability of Thermocouples be caused by overheating, cold working the wires, or by
introducin~~ contaminants into the junction. TMs type of
&3.2.3.l Reduction of Noise malfunction cannot be as readdy detected as the open junc-
II 9
Tree switching, analog filters, integration, or guarding tion.
techniques can be used to prevent receipt, of noise from I
external sources. Tree switching is a method of organizing 6-3.2.3.2.? Shunt Impedance and Galvanic Action
thermocouple channels into groups. Each group has its own Shunt impedance results when the thermocouple wire
main switch and a tree switch capacitance. Wkhout tree insulation $ails and thus creates alternate electrical circuit
switching, every channel can contribute noise directly paths. Galtianic action occurs where wire insulation materi-
through its stray capacitance, but with tree switching, als react tiith moisture to generate an electric current or
groups of parallel channels are in series with a single tree voltage, which may exceed the currentor voltage generated
switch capacitance’. This technique greatly reduces cross by the thermocouple.
talk in a large data acquisition system caused by reduced
6-3.2.3.2.4 Thermal Shunting
interchannel capacitance.
A thermocouple generates a specific current or voltage
An analog filter can be used directly at the input of a volt-
when the temperature of the dissimilar material junction is
meter to reduce noise; however, this filter causes the volt-
raised or lowered. Therefore, factors that affect the heat
meter to respond more slowly to step inputs.
transfer be~w the material from which the temperature is
Integration is a technique used to average noise over a
being sensed and the thermocouple alter the temperature
full line cycle and thus eliminate power-line noise and its
indicated. These factors include a drain or addition of heat
harmonics.
energy from the thermocouple junction through thermally
Guarding is used to reduce interference from any noise
conductive paths or from thermocouple extension wires to
source common to both high- and low-measurement leads.
extraneous ~heatsinks or sources.
The guard is a floatjng metal box that surrounds the entire
voltmeter circuit. The box and the connected shielding sur- 6-3.2.3.2.5 Noise and Leakage Currents
rounding the thermocouple wires shunt interfering currents. The effe$s of noise were discussed in subpar.6-3.2.3.1.
Another way to reduce noise pickup is to use twisted The introductionof stray dc inputs into a thermocouple cir-
pairs of thermocouple extension wires. cuit resultsIinan erroneous output.
6-3.2.3.2 Performance Degradation Problems 6-3.2.3.2.1 Physical Damage to the Thermocouple
@
Most thermocouple measurement errors can be traced to Physical’!damage to a bare wire thermocouple can result
one of the following sources: ii a short to the case, which can introduce stray elecrncal
1. Poor junction connection inputs, stray thermal inputs, or additional dissimilar metal
2. Recalibration of thermocouple wire junctions OJan intermittent nature. Damage to a thermocou-
3. Shunt impedance and galvanic action ple sheath can produce thermal or electical shorts.
4, Thermal shunting
6-3.2.3.3 ,, Advantages and Disadvantages
5. Noise and leakage currents
6. Physical damage to the thermocouple. The advhtages of using thermocouples follow:
1. They are self-powered.
6-3.2.3.2.1 Joint Connection 2. They are simple.
A good thermocouple occurs where there is an intimate, 3. They are rugged.
secure junction of the two materials. Acceptable thermocou- 4. They are inexpensive.
ples can be obtained by silver soldering or welding. Weld- 5. There is a wide variety from which to choose.
ing is the better method, but care must be exercised because 6. They can cover a wide temperature range.
the wires can be degraded by overheating. Any welding The following are the disadvantages:
fluid or the atmosphere in which the welding is performed 1. Their response is slower than that of diodes.
can result in diffusion of extraneous materials into the weld 2. They are nonlinear.
that change its characteristic voltage versus temperature. 3. A reference junction or subsystem is required.
Poor welds can result in an open connection; these, how- 4. The output is not as stable as that of other types of
ever, can be readily detected. Commercial thermocouples temperature transducers.
are usually produced on special machines that use capaci- 5. Their gain and, therefore, sensitivity are not as great
tance discharge techniques. as those for other types of temperature transducers, e,g.,
thermistors;
6-3.2.3.2.2 Recalibration
If the ch~acteristics of the thermocouple have changed 6-3.2.3.4 ~ Recommendations
so that the electric current or voltage generated for a given Overall, ~ermocouples could be used to detect a fire in a
temperature input is no longer within the tolerance allowed, combat veliicle. Each thermocouple would detect the pres- 9
the thermocouple has been recalibrated. Recalibration can ence of a #igh temperature at a selected discrete location;

6-26
 Downloaded from http://www.everyspec.com

MIL-HDBK-684

therefore, several thermocouples could be required to cover

o a given compartment. ‘l%ermocouples would provide a sim-

ple, rugg@ and inexpensive system that would have a
slightIy slower response than the continuous thermal detec-
tors already discussed.
6-3.3 TEERMOPILE
A thennopile is a number of thermocouples wired in
series so that tbe voltage produced is additive. Some k
detectors made in the US use a thermopile to establish that
heat is present when Ill rad~ation is sensed by optical sen-
sors, as discussed in subpar. &Z2.3.
6-33.1 Thin-Fihn Thermopile
Anmtec Industries offers a thin-film fhermopiie, which
can be made in different geomernes for specific applka-
tions. The constituent bismuth alloy and antimony alloy F@m 6-29. Typical Thermtopile Sensor Used
thermocouples are connected in series with the cold junc- in Russian T-55 MBT
tions in contact with an electrically nonconductive, but ther- raised to the flame temperature, and the device would not
mally highly conductive, mass of beryllium oxide (BeO) need power to operate. llte chromel and constantan wires
that essentially keeps the cold junctions at ambient tempera- me 0.41 to 0.43 mrn (0.016 to 0.017 in.) in diameter, and
ture. The hot junctions are coated with blaclq oxidized metal each bead is approximately 1.35 mm (0.053 in.) in diameter
for high-speed performance or with black organic oxide for (Ref. 10). There is reason to believe that this device is bektg
maximum spectral flatness. These hot junctions view the used as a heat flux sensor. See subpar. 8-2.1.3.3 for a
potential ilre site through a window that filters out all but a description of heat flux sensors.
desired narrow band of wavelengths of radiation, and this

0
,; window can be faceted to provide a wider range of view.
The thin-film thermopile generates a voltage. In an example
in which the ambient temperature is 20°C, an object at O°C
would produce -1.93 mV, and an object at 200°C would
6-4 OTHER DETECTORS
t%l.1 PENETRATION DETECTOR
A continuous wire grid system, which was designed to
produce 45.58 mV in a PS-15 thermopile, which has 28 hot sense combat vehicle hull penetrations by exploding mines,
junctions and a time constant of 20 to 40 ms (Ref. 50). was successfully demonstrated on a landing vehicle tracked
Armtec is developing a thermopile better adapted to combat personnel (LVTP) 5Ai vehicle (Ref. 51). Discharge of a
vehicles that will have a time constant of approximately 10 shaped charge upward into the hull of this vehicle usually
ms. Armtec thermopiles are currently used in intrusion results in a fuei cell being punctured and fuel beiig injected
detectors for indoor and outdoor surveillance. Thin-film into the vehicle. The ilel mixes with air and becomes an
therrrmpiles with similar characteristics are also tnanufac- ignitable mixture. This system is used to prevent or extin-
tured by other suppliers. guish the fire that could resul~ The continuous wire system,
as illustrated in Fig. 6-30, was installed in the vehicle, as
6-33.2 Russian Thermopile shown in Fig. 6-31, and consisted of a nerwork of wire gds
l%e Russians use a themnopile, similar to that shown in Iaminated between two sheets of a glass fiber. These wire
Fig. 629, for the sensing element in their combat vehicles
(Ref. 10). TM Russian thermopile consists of 15 chrornell Atltpmf
constantan thermocouples wired in series. The arnblertt tem-
perature junctions are embedded in a block of transparent
plastic within the housing. Such a device should increase S.5ms
the voltage output over that of a single thermocouple by f+
almost a factor of 15. This device does not produce a volt- Pefhatbn I
age proportional to absolute temperature; it produces a volt-
age when the exposed beads are subjected to flame and the Oms
embedded beads are at the temperature of the plastic mass.
The plastic does not heat ve~ much or very rapidly even =
WmGrid

,,
,,
0 ‘,
though the housing is exposed to flarw thus the sensor is
used to detect a sudden increase in temperature. Depending
upon the voltage needed to trigger the controller, the mtdti-
ple beads would tend to improve the sensor response by
HuO
*
Reprintedwith permission. Copyright FMCQCorporadon.
providing a usable signal sooner, i.e., before they have been Figure 6-30. WR Grk? Detector (Ref. 51)
6-27
 !1
Downloaded from http://www.everyspec.com
,,

MIL-HDBK-684 ;
~.—.-_.—r_.._.-:__ r._.,,_r.-_.—.—-—--,, since the system is a positive-type response requiring the
breaking of a wire, the system will not respond to fires initi-
ated by im~acts or penetrations that do not break a wire, ini- 9
tiated by p~netrators that impact an area of the vehicle not
equipped wnh wire grids, or resulting from fuel line leaks or
breaks. All ~f these fire conditions would not be detected by
the wire grid system but would be detected by either optical
or thermal !detectors. Another problem associated with the
L.._.-_._.-__.—.—— /–.=---—-–-> wire @“d system involves accidental or inadvertent damage
Hole in Grid for Access to Drain Plug
or breaking of a wire by personnel or other noncornbat-
,.--—-— — --—--—..*__ ._
related situations that would result in the system actuating
~=’~=:”]~~’=~,,:;,;;;-’--~ and releasing the tire suppressant into the vehicle (Ref. 11).
This potential problem can be overcome, or at least the
~..=.~i= .’ =.-.i::i:””=i Corrugated Steel Deck
‘\ Fuel Cells- probability~of occurrence can be reduced, by proper protec-
._— J_L s
I II ..,,_,_,..J’. tion of the wire .tid. *
‘“L ..
--._&+!-_..L _+~j.-.-L
The wird grid system to protect the areas of a vehicle vul-
/ 3.2-m(n (O.125-in.)Corru ated
Grid Between Fuel Cell \ Stee! Tray nerable to Iprojectile, fra=went, or shaped-charge impact
and Tray 9.5-mm 0.375-in, )BHN300
Steel Hul[ combined ~ith either an optical or thermal detection system
to protect the other areas of the vehicle and to provide over-
Reprinted with permission. Copyright FMC GCorporation.
lapping co~age appears to be a practical and effective way
Figure 6-31. Continuous Wire Grid System of to provide fire detection coverage.
L%’l? 5A1 (Ref. 51)
6-4.2 ShhOKE DETECTORS
~tid assemblies were connected to silicon-control-rectifier
Smoke detectors currently in use are based upon one of
(SCR)-type amplifiers, which, when activated, supplied a
two basic pl~nomena (1) photoelectric, which is due to the
current to one or several squib valves that released a fire
scattering of infrared radiation by combustion products or
suppressant into the veh~cle. The system was activated when
(2) a chan~ in the passing of a currentbetween the anode
the gid circuit was opened, i.e., when a wire was broken
and cathode thatfollows the ionization resulting from expo-
after the grid screen was perforated. When the hull was per-
sure to a radioactive source. a
forated by a shaped charge, the system response time from II
detection of the perforation to a level sufficient to actuate 6-4.2.1 ~hotoelectric Smoke Detector
the amplifier was established experimentally at 1.5 to 2.75 ![
ms. Total system response time including the time required 6-4.2.1.1 !I,Photoelectric Smoke Detector Used in
by the SCR amplifier to produce an output signal to the
squib firing circuit was 3.5 to 4.0 ms after initiation of the lcargOAircra*
The Sy~~on Dormer** photoelectric smoke detector
blast. operates on the TyrIdall effect. Thus in simple terms the
This system has been shown to be very reliable and to
smoke detector is a particle detector. As such, an alarm
have a fast response. The response time of the wire grid sys-
occurs when reflectance of these particles reaches a preset
tem compares favorably with that of the optical detector sys- value whether the particles are smoke, moisture, or dust.
tems and is much faster than that of the thermal detectors.
There are t~o versions of this type of detector, i.e., draw-
Detection of fire and release of the fire suppressant requires
through and free convection.
that one of the wires be broken, so the typical obscuration
The sensitivity of the detectors in light transmission Tg05
and false alarm problems involved with opticaI detectors are
percentagefifined as the percentage of light falling on a
obviated.
photoelectric cell through a 305-mm (1-ft) distance occu-
In tests of the APC Ml 1-3 and Ml 13A1 AFES in the
pied by smoke particles-is 94 to 96% TqO~for the draw-
1969-1972 period, the penetration detection system that had
through deiector and 80 to 9070 T“O~for the free convection
been proven on the LVTP 5A1 performed well (Refs. 11, 12,
detector. (~~f. 53) The operating temperature range for both
and 52). The penetration detector also reacted to penetration
by a 14.5-mrn armor-piercing incendiary bullet as well as to *This wire g~d penetrationdetector is reputed to have been field
penetration by a shaped-charge jet (Ref. 11). The penetra- tested in SE} and rejected as being too susceptible to fatigue or
accidental dqnage, but no records of such testing could be found.
tion detector was placed on the personnel side of the fuel Similar “problems” were encountered at both FMC Corporation
cell in the Ml 13 rather than on the hull side as in the LYTP and Aberdeen Proving Ground but were “solved” at both places and
the wire .tid$ then performed excellently. Thus the author of this
5A1. This placement rendered the penetration detector of handbook recommends reserving judgment on the results of the
the M 113 more subject to accidental damage than that of the reputed field tests until records of that work can be found and
LVTP 5A1 . assessed 9
The major disadvantage of the wire grid system is that **Identification of this supplier does not constitute Government en-
dorsement of the specific proiduct.

6-28
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devices is -30 to 70°C (-22 to 158°F), and the nonoperating and when the unit was cleaned (a simple operation), it oper-
temperature range* is -55 to 70”C (-67 to 158*F).The input aled properly again.
O
,’ :
voltage range for both is 18.0 to 32.2 V, and these devices
draw ks.s than 50 m% l’1’ievolume requirements fOr both 6-4.2.12 Photoelectric Smoke Detector Used in
devices are 102 x 178 x 76 mm (4 x 7 x 3 in.), and their Cosnmeraa.1 Buildings
masses are 610 g (1.34 lb) and 550 g (1.21 lb), respectively. Barksdale* fabricates a photoelecrnc-light-scattering
The draw-through detector has an optimum response time principle-smoke detector (Ref. 55) that has a normal sensi-
of 30s and a be mounted anywhere the sampling line and tivity of 3.3% per 305-mtn (1-ft) obscuration. This value
pump can draw enough air to ensure that the maximum sys- translates to 96.7% T3Min the rating system used in subpar.
tem response time is 60 s. The Systron Dormer draw- 6-4.2.1.1. The photoelectric smoke detector is available
through-type smoke detector has an opto-electronic response with and without a bimetallic strip heat detector, which trips
time of less than 2s. The time to alarm is a function of how at 57°C (135W. This smoke detector uses natural convec-
long it takes to get the concentration of smoke to the optical tion scanning and is quicker to react to smoke than tlte ion-
“chamber” to rngger the alarm. During six tests with smoke ization-type sensor described in the next paragraph.When
at 86.9% T3M and flow at 0.000142 rn3/s (0.3 ft3hnin), the the particles are in the range of 3 to 10 pm, the device has
ahmn times were between 2.53 and 6.71 s. the optimum reaction. The bimetallic Srnp heat detector
Mounting of the ~e convection detector is recommended assures that both heat and smoke are present before the
to be in the same comptument as the hazard. For optimum detector signals a fire.
performance this detector should be located ciose to the ceil-
ing widI the perforated cover fully exposed to the ambient 6-422 [onization Smoke Detectors
air. The system response time should again be approximately An ionization smoke detector contains a small quantity of
30 s. radioactive material that ionizes the air in a sensing cham-
A photoelectric smoke detector has been used in the cargo ber and makes the air conductive. This conductivity permits
bays of some Boeing, NlcDonstell Douglas, and Fokker air- a ctumnt flow through the air between an anode and a cath-
craft. The detector (Ref. 53) has three modes of operation: ode in the chamber. Smoke particles that enter the chamber

0,, off, armed, and tes~

The detector can provide three possible signals: armed
mode Iight on or off, test mode light off, and test mode light
blinking.
attract the ions and reduce the effective conductance (Ref.
56). The detector notesthe decreasein current flow by using
a Whetstone bridge-type circuiL
Ionization smoke detectors can react to particles in the
In the armed mode, if the alarm light is off, the detector is range of 0.1 to 3 pm and thus are quicker to react to a iknn-
signaling that smoke is not present above the threshold SeL If ing fire than the photoelectric sensor described in subpar.6-
the alarm light is ou the detector is signaling that there is 4.2.1.2. The ionization detector is more sensitive than the
smoke present above the threshold. photoelectric; the sensitivity of the ionization &tector is
h tie test mode, if the alarm Iight stays off, the detector is 1.5% per 305-mm (1-ft) obscuration, or 98.5% T3ti trans-
indicating a mdfitnction. If the alarm light blinks on and off mission. The ionization smoke detector is not as sensitive to
at a 5-H2 rate, the device is indicating that there is a buildup dust as the photodecrnc smoke detector, but excessivedust
of dust either in the sensing labyrinthor on the optics or that deposits can reduce its sensitivity.
smoke is present at less than the alarmlevel.
6-4.3 VAIUOUS GAS DETECTORS
Nfoisturecaused a problem for cargo aircmftsmoke detec-
Not too many years ago miners camied canaries down
tors because they would alarm after being cooled in tight
into mine shafts to establish whether or not the air was
and then subjected to high-humidity air on the ground. This
breathable. Canaries have now been replaced with many
problem was corrected by the addition of a heater block
devices that can determine why the air is not breathable.
which is designed to keep the sensing portion of the smoke
Small devices can detect the presence of carbon monoxide
detector above the dew point in humid environments.
and other noxious gases, they can determine breathability of
The possibility of detecting smoke while operating in
airby the percentage and partial pressure of oxygen and
dusty environments, such as on ground vehicles, by using
they can determine whether a combustible or explosive
these detectors would have to be demonstrated.The Systron
mixture of vapors exists in the air (Ref. 56). Use of devices
Dormersmoke detector, however, has been tested to par.46,
similar to these could permit monitoring of the air within
‘Dust Test”, of Underwriters Laboratories standard UL 268
the crew and engine compartments so thatan incipient fire
(Ref. 54) with no false warnings. This result is attributed to
situation or smoldering fire could be discovered and preven-
the patented labyrinth design, which houses the smoke-sens-
tive action taken before afire flames.
ing elements. A fail-to-test condition did eventually occur,
In general, small, portable devices are available that can
*Nonopesat@ (stomge)ternpemturerange is the rangeof tentpera-
tures to which the device can be subjected and remain functional, Wtentitication of this supptier does not constitute Government
bxnthe device does uot have to function rhrougttout the entire range. endotsemeruof the specificproduct.

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MIL-HDBK-684
detect various gases, but they would have to be modified for TABLE 6-5. INTERFERENTS FOR CARBON
use in combat vehicles. MONOXIDE DETECTOR (Ref. 57)
6-4.3.1 Noxious Gas Detectors SENSOR
Small, portable devices are available to detect carbon !1 INTERFERENT
INTERFE~NT CONCENTILATION, ~Es~o~sE
monoxide (Ref. 57). The sensor is an elec~ochemical s ppm
polarographic cell. Samples are drawn past a porous tet- .tmm
.
rafluoroethylenemembrane. Carbon monoxide is electroox- Ammonia ~ 100 –4
idized to carbon dioxide in proportionto the partialpressure Benzene ~~ 17.7 0
in the sample area. The electrical signal thatresults from the Carbon dioxide 5000 –4
ensuing elec~olysis is temperaturecompensated and ampli- Carbon disulfide 14.5 i-2
fied to drive the meter.The response is 90% complete in.less
Chlorine 5 o“
than 30 s. This detector can detect carbon monoxide to one
Dimethyl sulfide 4.5 +2
part per million @pm). The operating temperaturerange “of
the instrument is O to 40°C (32 to 104”F) and the relative Ethylene 50 +100
humidity range is 5 to 95Y0.It was designed for use in nor- Freon 12 1000 -2
mal civilian working areas and would require more engi- Hexane 500 –2
neering and testing before it could be used in a combat Hydrogen ~ 500 +70
vehicle. There are several materials that can cause a false Hydrogen cya- 42 +30
indication of carbon monoxide; these materials and their nide
effect upon the reading by tie device are given in Table 6-5. Hydrogen sul- 40 +170
6-4.3.2 C@gen Detector fide I
The capacity of the air to supply the necessary oxygen Isopropandl 50 +40
could be established rather than the presence of asphyxiant Mercaptan !
;!
gases. A human’s lungs require oxygen to be available at a ethyl 4.4 i-6
partial pressure of at least 13.3 kPa (1.93 lb/in.2 or 100 mm methyl 5 +7
Hg) (Ref. 58). ,
Methane 50,000 -3
A family of instruments is ,available that directly senses
Methanol ~~ 50 +130 9
oxygen by a galvanic cell containing a gold anode and a
Nitric oxide 100 +260
lead cathode in a basic electrolyte (Ref. 59). This electrolyte
is on one side of a fluorocarbon-polymer diaphragm, and the Nitrogen dioxide 100 +80
air sample is on the other side. Oxygen diffuses through the Sulfur dioxide 150 +30
diaphragm and initiates an otidation reduction reaction that
Reprinted with permission. Copyright o Mine Safety Appliances
generates an electric current proportional to the partial pres- Company. ,,
sure of the oxygen. These devices are accurate to MI.3%
oxygen at constant temperature and pressure over a range of and air. One~tinstrument uses the catalytic action of a heated
O to 25% oxygen. They reach 90’70of full response in 20 s platinum fil~ent in contact with the sample of gases (Ref.
over the temperature range of O to 40”C (32 io 104”F) agd 60). The filament is heated to operating temperature by an
within 3 min over the temperature range of-18 to O“C (Oto electric curr~. The gas sample in contact with the filament
32”F). The relative humidity operating range is 10 to 90910, bums and thus raises the temperature of the filament propor-
and the operating temperature range is O to 40°C (32 to tionately with the amount of combustible in the sample. ‘l’his
104°F) or –18 to 40°C (Oto 104”F) if calibrated at the tem- filament is in one leg of a Wheatstone bridge, which pro-
perature of use. vides a sigrial proportional to the temperature of the fila-
ment. This ~device can be calibrated with any desired
6-4.3.3 Combustible Vapors and Their Potential combustible gas or vapor and can provide a signal at any
Hazards point between O and 100% of the lower explosive limit
If the coolant air leaving the engine compartment were (LEL) of the combustible vapor used for the calibration.
monitored for combustible vapors, incipient combustion There am!some limitations with this equipment. Sihmes
could be detected prior to ignition. An engine fire due to and silicon$s and other compounds containing silicon can
nonballistic causes could be prevented if the combustibility rapidly “poison” the platinum filament. Leaded gasoline
of the air in the engine compartment were monitored and vapor can also “poison” the filament. Atmospheres deficient
appropriate action were taken if required to lower the oxy- in oxygenJless than 1OTO—maynot indicate the proper
gen concentration or cool the compartment. concentrations of combustible gases, but that omission
There are many devices available to establish the exist- would not be important since such atmospheres do not sup-
9
ence of a combustible or explosive mixture of fuel vapor port fire.

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MIL-HDBK-684
A version of the combustible vapor detector can sense automatically resetting unit routed through the engine com-
,, molecular oxygen (Ref. 56). The time to 90% of full partment. This detector signals a warning at the control unit
‘,’
o response for this device is 15s within an arnbkmt tempera- if the temperature in the fire zone exceeds a set maximum
ture range of O to 40°C (32 to 104”F), the normal operating operating temperature. The warning is cancelled automati-
temperature range of the instrument. The accuracy of this callyy if the temperature subsequently drops below the set
detector is W% for oxygen at consistent temperature and maximum operating temperature. See subpar. 6-3.1.3 for
pressure and fi~o LEL for the combustible gas. ‘I%eoperat- discussion of continuous thermal detectors.
ing humidity range is 10 to 9070 relative humidity. This
6-5.2 BRADLEY FIGHTING VEHICLES
device was designed for use in a normal civilh.n work area
The fire suppression system far the Bradley fighting vehi-
(Ref. 61). Further engineering and testing are needed before
cles is shown in Fig. 6-14. This system has a dual spectrum
this device could be installed in a combat vehicle.
infrared sensor system in the crew compartment but no fire
Devices are available with sensors that determine the
detection system in the engine compartment.
presence of oxygen, combustible fuel vapors, and carbon
dioxide (Ref. 62). 6-5.3 MBT M60A3
From 1981 through 1987 a product improvement pro-
6-5 EXAMPLES gram was conducted for the M60A3 MBT that included an
6-5.1 LEOPARD II MAIN BATTLE TANK AFES, shown in Fig. 6-33, used opticai sensors. Many tests
The fuel explosion and fire protection system for the of the system were perfotmed (Refs. 64 through 68), and
several interesting conclusions were drawn fkom this pro-
Leopard H main battle tank is shown schematically in Figs.
gram. The independent evaluation report (Ref. 13) con-
6-2S and 6-32 Included are the detectors, control uni~ and
cluded that engine compartment optical sensors get dirty
extinguishers. T%eengine bay system is shown in Fig. 6-25,
often and easily and will not function properly when dirty
and the crew bay system in Fig. 6-32. Infhred radiation is
and that their locations made them difficult or hazardous to
sensed in the crew bay by four sensors located fom and aft
clean. Subsequently, a thermal detection system was evalu-
Under noncombat operating conditions the control unit
ated for the engine compartmen~ An AFES was not fiekkd
operates the extinguisher system only if simuhatteous sig-
for the M60A3 due to its phaseout fkom the active Army.
nals are received fkom at least two detectors, whereas umier
battle conditions the control unit can operate muhiple extin-

o,.,+K
guishers upon receipt of a detection signal from only one
detector.
The fire detection and extinguishing system for the
engine compartment of the Leopard U uses the Fmwire@
thermistor-type continuous thermal detector. Fhewire@is an

H&km Botl!ss

Test and
AMrn Panel

E L?WctorsLocaed In Turret _ Control MI ● SUpwsssors

Four
Reprinted witi permission Copyright 0 Kidde-Graviner Ltd.

Hgure 6-32 Leopard 31 Crew Bay Fm Detec- Figure 6-33. Fire Detection System Designed for
tion and Suppression $ystern (JM. 63) the N160A3 NIBT (Ref. 13)

,,
,:
O
6-31
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MIL-HDBK-684 “

REFERENCES ing Ground, MD, 4 March 1987.

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6-32
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,,
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0!,
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,,
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6-33
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61. MSA Data Sheet 08-01-08, Portable Indicator and and Ultqviolet Detection”, Fire Journal (July 1983).
Alarm, Model 261 (Combustible Gas and Oxygen), Fire and Explosion Protection Systems for Aircraj? Engine
Mine Safety Appliances (MSA) Company, Pittsburgh, and Dry ~y Compamnents and Vehicle Crew and Engine a
PA, 1990. Bay Compartments, HTL/Kin-Tech Division, Pacific Sci-
62. MSA Data Sheet 08-02-08, Portable Indicator and entific, ~dvanced Technology Group, Duarte, CA, Undat-
Alarm, Model 360 (02, CO) and Combustible Gas, ed. ~
Mine Safety Appliances (MSA) Company, Pittsburgh, Ml TANK! PROGRAM-Sensor, Fire Detection Critical
PA, 1990. Item Product Function Specification, SC-X 15220D, Gen-
63. Military Vehicle Protection, Crew and Engine Bay Fire eral Dyntics Land Systems Division, Warren, Ml, 13
Detection and Suppression, Kidde-Graviner Ltd, Coln- Februq, 1984.
brook, Berkshire, UK, Undated. Hybrid Explosive Fire Sensing System for Armored Vehicle
64. J, L. Chabot and R. Rernicci, Product Improvement Test Engine ~ompartment, Dual Spectrum Brochure, Hughes
of Trek, Combat, Full Tracked: 105-mm Gufi M60A3, Aircraft Company, Santa Barbara Research Center, Gole-
Report No. APG-MT-5543, US Army Test and Ev@ua- ta, CA, ?_fnd&ed.
tion Command, Aberdeen Proving Ground, MD, June
1981.

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MIL-HDBK-684 -

CHAPTER 7
EXTINGUISHING AGENTS AND SYSTEMS
Fire extinguishants and their uses and hazunir are discussed Xhe extinguishants are given in order of their prineipaf
fhe-extinguishing phenomenon Exn@aishants for a deep-seated celhdosic, such as rubber or wood or combustible metals
jires are &scribed Both ad”ve and passivefire-extinguishing systems are presenled The principal components of each type
of system are discussed The use of handheld extin@shenr is descn-bed System dem”gnfeatures, such as the dkn’bution sys-
t~ the automatic contrvl system and the means of activatio~ are covered, artd the basic design and design objecn”ves
given.

ftE = number of moles of extinguishan~ mol

7-0 LIST OF SYMBOLS no = number of moIes of oxygen, mol
~b, c.d= converted empirical constants in Table 7-4,
= number of moles of residual products, mol
J/@K) ‘P
nw = number of moles of water, g
Cp = specific heat at constant pressure, J/ (gK)
G. mean of the specific heats at the initial and
Q. = heat involved in chemical change, J
Qh = tpntit’y of heat fiowing into a systeq J
final tempe~ J/(g.W)
cppA = specific heat of potassium acetate and water
Q, = tpntity of heat required for transition, J
solution, J/@K) q = heat involved+ J
T = temperature, K or ‘C
G,l = specific heat at initial temperature, J/@”C)
q = final temperature, ‘C
%2= specific heat at final temperature, J/@-”C)
~ = initial temperature, “C
G= latent specific heat of transformation, J/g
TP = plateau temperature, “C
Cortc = concentration of potassium acetate, % wt
TO = ambient temperature, “C
d = diameter of nozzle orillce, mm
v = voltage between conductor and earth, V
F& = ihexing point of potassium acetate and water
AT = change in temperature from initial to final
solution, ‘C
value, deg C
Hf = beat of formation, J/g.mol
p = specific resistance of water, Skim
H4 . heat of formation of iti substance, J/g.mol
q. = beat of formation ofjti protktcq J/gmol
i= electric curren~ A 7-1 INTRODUCTION
i= substance involved in reaction, dimensiordess The following paragraphs describe the phenomena
.= product of reaction, dimensionless involved and identify the agents “available to extinguish a
J
i = total number of substances or products, fire by (1) excluding oxygen or fuel from the reaction, (2)
dimensionless chemical intervention, and/or (3) cooling the reactants
1 = distance between nozzle and conductor, mm below their ignition temperatures. T~ical extinguisher
devices and systems are also describe~ and examples of
Mw= molecular weigh~ ghnol
existing fire extinguisher systems for vehicles used by the
m. = molecular weight of carbon dioxide, g/mol
various .semices of the armed forces and pertinent civilian
m~ = molecular weight of extinguishmen~ g/mol
organizations are presented.
My = molecular weight of F substance, g/mol
MT = molecular weight of jti produch g/mol 7-1.1 GENERAL
Mwo . molecular weight
of oxygen, 31.9988 ghnol To reduce logistics requirements, the United States (US)
Mw$y = molecular weight of waler, ~mol Army prefers to stock a single fire extinguishan~ which is
m= mass of substance, g intended to extinguish most types of expected fires. When
me = mass of carbon dioxide, g each vehicle is designetL a specitic extinguishant is selected
mi = mass oft% substance, g and specified for use in the onboard fire-extinguishing
/Fljmass of]* produc~ g
=
equipment. This selection is based upon the state of the art
of fire-extinguishing systems and upon existing design
W = mass of atmospheric oxygen, g
mw = mass of water vapor, g tquirements. Because fire-extinguishing system design is
based upon vehicle requirements as well as extinguishant
N“ = number of moles of extinguishant in 1 kg, mol
characteristics, the specified extinguishant is used until a
n = number of moles of subscripted material, mol
vehicle modification order is issued to change the extin-
nc = number of moles of carbon dioxide, mol guishant designation.
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.1=
MIL-14DBK-684
Fwe-extinguishing agents, or extinguishants, used in
‘combat vehicles must effectively extinegish fires from the
combustibles therein, particularly from the’ hy@ocarbon. flu-
ids used as mobdity fuels, hydraulic power fluids, and lubri-
cants. Explosives, both low explosive;, e.g., gun
~propellants, and high explosives, e.g.; warhead fillers, tie
not usually extinguishable because the reaction rate of many
‘exrdosives is too fast for most practical extinguisher sys-
tems, the explosives contain su&cient oxygen to combust, ..’.
and/or it is difficult to place the extinguishant on the bur-
ning propellant. Currently, the best method to protect the
vehicle fro’m the reactions of explosives is proper magazine
design, v described in subpar. 7-3.2.1.1. For hydrocarbon
fluids the primary agents that will be dischaged within
compartments of the vehicle should not affect occuptits,
equipment, or cargo since use of some agents can generate
o
0“5
I I
10
Nontlamrnable
!
15
I
20
1
25
I30
toxins, asphyxiants, or irritants ‘for humans, and some Mole PercentW ater
Vapor, O /.
agents or their by-products will corrode, coat, short out, or Figure 7-1. Flammability Envelope Illustrating
otherwise afTect critical equipment.’ On the other hand, some
Influence of Water Vapor on Diesel-Fuel-
secondary agents may be needed to extinguish comb~tion
Vapor-Air Mixtqre Flammability
of mate&ls for which the primary fire-extinguishing agents
are not ‘effective. Secondary extinguishants may be. neces- “for all fuel+$r extinguishant concentrations. As an illus-
sary ‘“wd should be provided in portable extinguishers for .. tration, reported values of the flammability. peak for+hys-
electrical fires, liquid hydrocarbon. pool fires, deep-se+ted ical-acting agents with hydrocarbons typical of mobility
cellulosic ties, and combustible metal fires. fuel vary from about 24% for added water vapor (Ref. 1)
‘ Knowledge of fire-extinguishing agents and detection to about 45% for added helium (Ref. 2). Reported values
and suppression systems is important in the design of com- for chemical intervention agents with similar hydrocar-
bat vehicles. Vehicles should be designed using appropriate bons vary from 4.2% for added Halon 1202 (dibromodi-
0
fire prevention principles, and personnel must be trained in fluorometharie) to about 18% for ...added ....Halon 121
the” use of the fire prevention systems because crew and (chlorodifluorometharte) (Ref. 3). ~~
vehicle survivability may depend. upon the crew’s knowl-
edge of extinguishment techniques, especially during com- 7-1.2 PAST EXPER.I13NCE
bat. The US Army Safety Center (USASC) data (Ref. 4),
The flammability-principles discussed in par. 2-2 provide-,,. described in subpat 4-1.1, also provide information-on the
a sound basis for a discussion of fire extinguishment princ- effectiveness, of the vehicular fire-extinguishing devices, as
iples and the desired characteristics of extin~ishing agents. shown in Table 7-1. The-extinguishant used in the M 1 main
The phenomena involved in fire extinguishment may ,be battle tank (MBT) and the M2/M3 Bradley Fighting Vehi-
divided into two basic categories, namely, (1) cher@cal cles (EWV) wv Halon 1301. The extinguishant used in the
mechanisms and (2) physical mechanisms. “The chemical other vehicles was carbon dioxide. To be rated effective, the
mechanisms capture free radicals or use oxygen in a &ldly extinguishant has to extinguish the fire without reignition.
exothermic or, hopefully, “endothermic process. The physi- The vehicul$ fire-extinguishing provisions include both
cal mech~isms insert a barrier between the reactants and fixed fire-extinguishing systems and portable extinguishers.
the reaction, dilute the oxidizer or the fuel, or. cool the reac- The data for onboard systems in Tables 7-l(A) and (B)*
tion below the temperature needed to sustin the fire. indicate that overall the fire-extinguishing devices provided
For vaporized fuel and either a physic~ mechagism or were at best “4470 effective, systems using Halon 1301,
chemical mechanism extinguishing agent, the extinguish- which include portable extinguishers, were approximate] y
ing properties may be represented graphically, as illus- 45% effective, and systems using C02 were approximately
trated for diesel fuel vapor and “’water vapor in Fig. “7-1. 43% effective. Automatic Halon 1301 systems were 28%
The left side of the flammability envelope shows the effective, and manual initiation Halon 1301 fixed systems
upper and lower limits of flirnmabil$y, whereas the. bal- were 24% effective. Note in ‘Table 7-l(C) that of 212 inci-
ance of the flammability envelope exhibits me efficacy’ of dents in which the means of final fire suppression was
the extinguishing agent., The tip of this envelope on the given, in only 124, i.e., 58’%, did the onboard fire-extin-
right (commonly referred to as the “flammability peak”)
denotes ‘the added quantity “of extinguishing agent or con- *The data given are too sparse for this to be other than an indica- 9
,, centration required to prevent combustion, i.e., to inert, tion.

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MIL-HDBK-684
guiding system extinguish the fire. Thus there were 88 inci- destroyed. However, in 69 incidents (33%) a lire department
dents reposted in which onboard portable extinguishers or had to extinguish the fire using a great volume of water.
tied fire-extinguishing systems (FFESs) either were not T&se data indicate that in 56% of the fires successfully
used or were not effective. As described in Table 7-l(C), of extinguished-38 using manualIy activated FESS and 81
the 212 incidents for which data are given, onboard pmable using portable fire extinguishers or other mean+e crew-
extinguishers were effectively used in 79 of the incidents to men were actively involved. ..
accomplish or finish extinguishment of the fire and other I%e data fkorn Southeast Asia (SW) given in Table
means used in 2 incidents for a total of 38% extinguished 4-2 provide another indication of rhe effectiveness of the
manually by crewmen. In 14 incidents the 6res self-extin- fire-extinguishing systems. previously &cuss@ 26-inci-
guish@ and in 3 incidents the vehicle was totally dents are included (Ref. 5). Halon 1301 was used in the

‘IXBLE 7-L FIRE EX’ITNGUISEER SYSTEM EVALUATION (I&f. 4)

A) Effectiveness of Onboard Fire Extinguisher Systems or Equipment
FFESAUrOMATtCtMIMTtON FFESMANUAL tNMATtON PoRTABtx
r41.MBEit
OF NUMBER OF NUMBER OF NUMBER
OF NUMBER OF NUMBEROF
vm’tIcfz* . TIMESINrrtATEDTtMm EFmcm—E TtMEstNrnATED TtMEsEmXmvE TIMEsUSED -mvtEsEtmXtWE
Ml MBT 22 7 20 5 20 16
M2 and ND BFV 3 0 1 0 7 5
M60 MBT 66 14 53 35
M48-MBT 4 2 3 2
M113APC 8 I 14 7
M88 TRv 34 14 14 9-
AVLB, CEV, and 8. 2 3 1
DIVAD
M109 and Ml 10 SPH o 0 4 4
Totals 2s 7 141 38 118 79
Effectiveness. ?0 28 27 67
*AN = armored personnel carrier CEV = combat engineer vehicle
TRV = mtcked recovery vehicle SPH = self-propelled howiuer

(B) Effectiveness of Extinguishartt in Onboard Systems or Equipment

FFEsAutmtAnc
tNrmmoN
FFEsMANUAL
tNmATIoN I PotrrABLE
I AU ONBOARD

NUMBER OF NUMBER
OF NUMBER OF NUMBEROF NUMBEROF NUMBEROF tWMBEROF NUMBER OF
TnuEs
lNmAIED EFFEcm% m=lxmvE USEO ElmXrWE USED ElmrrtW
I%lon 1301 25!7 21 5 27 21 73 33
o I o 120 I 33 I 91 i S8 1. 211 I 91
28 24 78 45
Not Applicable 27.5 64 43
~Total Incidents 2517 141 I 38 118 I 79 284* I 124
Overall
Effectivens %
*Each fire-extinguishing system usage is considered a sepamte evem Thus if an automaticdy initiated system ftis to extinguish a tire and
- tbe manually initiamd backup system also fails and then the portable extinguished are use& these three attempts are treated risthree
incidems.

(cent’d on next page)

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MII.,-I-NX3K-684

,. TABLE 7-L (cent’d)

. ..
C) Extinguisher
.. . .... . -+,-.
Used for Find Suppression of Fire e
I 1“ I FIXEDFIRE I I I I
VEHICLE NUMBEROF NOT SELF- EXTINGUISHER PORTABLE OTHER FIREDEPT VEFUCLE
EWJDENTS REPORTED EX~GUISHEO *~ ]; MANUAL DESTROYED
3
Ml Tank 39 2 7 “1 5 16 0 6 0
M2 and M3 9 ‘1’ ‘1’: o 0 5 0 2 0
BIW
M60 Tank 88 8 “3 * 14 35 0 28 0
M48 Taqk 5 0 ‘o ““ * ‘2 2 0 1 0
*, 1**
Ml 13 APC 40 7 6 1 7 15” 3
* 14 g. o 13
M88 TRV 38 ,-2’ ,’ 0 0
AVLB, CEV, 8, 0 0 “ * 2 1 It 4 0
and DIVAD
M109 and 6 ‘o ‘2 * o’ 4 0 0 0
M11OSPH
-:Totak- 233 ,21 14 ‘7 38 79 2 69 3
, I
212 incidents in”which 124 incidents total using onboard
data are given free-extinguishing equipment
. ----
. ..
*no automatic fixed fire extinguisher system
**~s& snow
lused water from a garden hose

●
armored reconnaissanceh.irbome’ assault vehicle (i nition, was on .a test drive. in Iraq after being repajred. ‘l%e
~V),M551, and C02 was used in the. other vehicles. In ambient temperature was approximately 32°C (90°F). A fire
the six M551 fires the fixed fire extinguisher system was started in the engine compartment. The fixed EMon 1301
used in two cases (Document Acquisition Numbers system, described in subpar. 7-5.1.1.6, temporarily extin-
(DAM) 463 and 1.532) without success, and po~able guished the fire, but the fire later reignited. Due to the large
e&guishers were used in two cases (DANs 670 ~d amount of ammunition in the vehicle and to the 1st Armored
“1532) with success. In addition, one.fire @AN 632) self- Division Artillery policy to evacuate burning tracked vehi-
extinguished after burning” all “me avtilable- fuel (wire. cles immediately, the crew initiated the fixed fire. exting-
insulation in the battery box). In the sixth incident (DAN uisher system and evacuated the vehicle. The vehicle
1550) the propellant exploded upon jet impact and burned - for approximately 30 rein; then the contents
des~oyed the ve~cle. In the 20 incidents* involving vehi- exploded. The” second incident occurred in rnid-Apnl 1991
cles. containing C02 fire extinguishers, portable extin- while the division was redeploying from Iraq to Saudi Ara-
guishers were used seven times (DANs 228, 301, 381, bja. The ambient temperature was 43 to 49°C (110 to
607, 671, 728, and 1709) but were successful only @ee 120”F), and the FAASV had been traveling for over 10 h.
(DANs 607, 671, and 728) of those. times. In four other The fire is believed to have started in the crew compart-
incidents other means were. used to extinguish the fires, ment; it was probably due to an electic short in the blower
i.e., water in two (DANs 1666 and 1668), a wool blanket section of the ventilation system. It was reported that a bag
in one (DAN 432), and dirt thrown by a shovel in the of clothing was in contact with the blower motor and that
other (DAN 1709). In the other. nine incidents no extin- the short ignited the bag of clothing. Only the driver and
guishment method’ was listed, but four fires (DANs 117, vehicle commander were in the vehicle. The vehicle com-
169, 756, and 1682) self-extinguished: mander was looking out of one of the hatches and ~eported
In two incidents involving two field artillery ammunition that he did not detect the fire until it was burning well. (The
support vehicles (FAASVS) in Southwest Asia (SWA) (Ref. sand and dust were very thick and probably prevented the
6), both vehicles were. lost. The first incident occurred in commander’s detecting the fire earlier.) Both men evacuated
mid-March ’1991. The vehicle, camying a full load of ammu- the vehicle. ‘I%ey reported that the automatic EMon system
activated but did not extinguish the fire. The vehicle later
*The vehicles were MBTs M48A3 and APCs M113A1. These exploded. In both incidents there was not enough of the
vehicles had fixed C02 fire-extinguishing systems for the engine vehicles left after the explosions to verify “the cause of the a
compartments and portable C02 extin=~ishers in the crew com-
fires or the performance of the fire extinguisher systems.
partment.

7-4
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MIL-HDBK-684
The author-of this handbook can only concur with the
policy of the Lst Armored Division Astillery. Halon 1301 is Q, = . Ct+n, J (7-2)
not the extinguishant of choice to suppress fires in hot diesel where
“engines effectively because the iires will reacldy reignite as
soon as the Halon dissipates, nor is Halon 1301 the extin- C,= latent specific heat of transformation, J/g
guishant of choice to fight a tie in a bag or pile of clothes. Qt = q~tity of heat required for transitio~ J.
This is a Class A lire that requires liquid cooling. la addi-
tion, HaIon 1301 is notable to prevent heated solid gun pro- 3. For a chemical change, the heat ~ involved is. -
pellant from combusting. A vehicle designed to crmy such a
quantity of explosive must be better able to withstand the
ignition of its contents. (See subpar. 4-6.4.1 for such a
design technique.) A better analysis should be made of the
fire-extinguishing or t%e suppression needs of this vehicle, where
Q.=i,[%-i{%m’l’ ‘7-3
and a more appropriate total protection system provided. Qc= heat involved in chemical change, J
Hf = heat of formation, J/gmol
.-..
7-1.3 TECHNIQUE FOR AGENT COMPARI- m= molecular weigh4 g/mol
SON
1= total number of substances or products,
‘l%e following method is offered to provide a means co dimensionless
eompam the performance of potential fire-extinguishing ~{= molecular weight oft+ substance, g/mol
agents. Only the cooling effect, the generation of dilu-
Mlyj = molecular weight of ja produc~ g/mol “
ents, and the removal of atmospheric oxygen by the
tlti = mass of iti substance, g
extinguishant are considered. A case is hypothesized in
ttlj = mass of jti produc~ g . .’-
which I kg of the extinguishant is injected into a volume
that is at a temperature of 177°C. and at constant sea Hh = heat of formation of itisubstance, J/gmol
level pressure. The heat that various extinguishants can H4 = heat of formation ofjb producL J/gmol
absti and the mass of diluents, i.e., water vapor and i= substance involved in reaction, dimension-
carbon dioxi&, generated are calcul~ti in subpars. less
.,:!,
~,
0
,,,,“!, 7-2.1.1, 7-2.2, 7-2.25, 7-2.3.1, 7-2.3.1.2, 7-2.3.2, 7-2.3.4,
and 7-5.1.3.4.3.
j= product of reaction, dimensionless

‘I%e effeets of these thermal and chemical processes can The mass of diluents generated and atmospheric oxygen
be estimated using the following equations: consumed comes from evaluating the chemical process:
1. To heat or cool a substance in a single state, i.e.,
soli~ liquid, or gaseous. the quantity of heat Qh required is

(7-1)
where
where = number of moles of subscripted material, mol
quantity of heat flowing into a systew J ;= extinguishant (carbon based)
mean of the speciilc heats at the initial C+ and O*= oxygen
final ~T2 temperatures, or P= residual product
H20 = water

(Ycp.,)’’i(g”oc)
co~ = carbon dioxide
=: ~ = heat iilvOh@* ~.

m = mass of substance, g The number of moles of extinguishamin 1 kg AfEis

AT= change in temperature from initial Z to final
value ~, or AT = ~-Z, deg C.

ZVE = =, mo 1 (7-5)
h4wE
2. For a change in state of a substance, i.e., melting or where
freezing to change between solid and liquid states or vapor- h!tw~ = molecular weight of extinguishan~ g/mol.
izing or tique@ing to change between liquid or gaseous
states or subliming or solidi~ng to change directly When the process is endothermic, q is positive, when the process
between solid nnd gaseous states, the heat Q, required is is exotkmic, q is negative.

7-5
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r M~L-HDBK-684
l%e mass of atmospheric oxygen in. removed is
these classes. Some blends, e.g., wet powders, exhibit all
.$, .
no three mechanisms. Accordingly, each agent has been classi-
m. = NE— - MWO, g (7-6) fied in Table 7-2 according to its dominant mechanism.
m
nE
7-2.1 OXYGEN OR FUEL EXCLUDERS
where The agents in this subparagraph function primarily by
MWo = molecular weight of oxygen, 3 1.?988 .#mol blanketing the burning fuel with a layer of inert gas (or liq-
no = number of moles of oxygen, rn’ol uid), by diluting the surrounding air with an inert gas, or by
nE = number of moles of extinguishtit, mol. inserting a barrier-between. the oxidizer and the. fuel. .Thus
sufficient oxygen and/or fuel for sustained combustion do
Mnilarly, the mass of water vapor generated rnw is not reach the combustion zone.
For several fire extinguishants, Fryburg (Ref. 7) provided
mw=i%~.mw,g (7-7) a measure of the relative volume percentage needed to ren-
der a fuel-air ~xture nonflammable. A vertical glass tube,
where 1.80 m long and 50 mm in diameter, was prefilled with a
MWW = molecular weight of water, g/mol.
.. mixture of gaseous fuel and air containing a given percent-
age of gaseous diluent. The mixture was considered flam-
Ihe mass of carbon dioxide rnc is mable if a flame, ignited by passing a small alcohol flame
across the bottom, propagated the full height of the tube.
m= = NE~E. MWc, g (7-8j Table 7-3 cont@s properties of the diluents tested as well
as the minimum percentage by volume of each that rendered
where a methane (CH4)-air mixture nonflammable. The investiga-
MWC = moleculrwweight-.of c~bon dioxide, g/mol. . .tors concluded that the following are the factors ,by ~~ch
the noncombustible diluent gases—argon (Ar), helium (He),
While evaluating fire extinguishants, the desia~er must nitrogen, water vapors, ahd carbon dioxide-rendered the
keep in mind the objectives of extinguishing. fires. The rnixt~e nonflammable:
first objective is to preserve life, and to do this, air tem- 1. Reduction of the oxygen content of the air (which
1perature must be kept below approximately 60”C (140°F). primarily affects the upper limit of flammability) .-
The second objective, when a soldier’s life is not endan- 2. Thermal capacity of the diluent a
gered, is to preserve the usefulness of equipment, e.g., alu- 3. l%erm~ conductivity of the diluent.
minum, which is now widely used for ‘US vehicles, must The relative inerting effects of argon, nitrogen, and car-
be kept below approximately 177°C (350”F), plastici or bon dioxide we related to their relative specific heats. The
I;omposites, below approximately 123*C : (254°F), and difference in performance of Ar and He is related to their
steel, below approximately. 538°C, ( 1000°F); Thus a use-. relative thermal conductivities. “Water, however,. would per-
M goal for extinguishants is. to operate over the tempera- form differen~y because of potential cooling due to change
ture range of –54°C (-6501?) to 177°C (351°F); beyond in state. The halocarbons, carbon tetrachloride (CC14), or
that the environment is either too cold for practical opera- Fkilon 104, and dichlorodifluoromethane (CCIZFZ), or I-Ialon
tions or aluminum equipment has been heated beyond sai- 122, showed a “greatly enhanced aptitude for provoking
vage. For” effective extinguishment of deep-seated [we] extinction” (Ref. 7).
celluosic fires (such as bags of clothing), .heat’ must be
TABLE 7-2. DOMINANT
transferred out of the burning” materials. The time
required for heat transfer is directly proportional to the I?IRE-EXTINGUISHING MECHANISM OF
heat tramfer coefficient. Heat transfer from. a, hot solid to AGENTS
a g“meous coolant is an extremely slow process. For exarri-
ple, the heat transfer coefficient for air is very low; as CLASSIFICATION OF AGENTS
shown in Table 5-1, it is in the range of 1.14 to 57 W/
. OXYGEN OR FUEL CHEMICAL COOLING
(mZ.K). The heat transfer coefficient for a liquid coolant
EXCLUSION INTERVENTION
such as water, however, is in the range of 284 to 17,000
W/(m*.K). The cooling effect of an extinguishant from Carbon Dioxide Halons Water
21°C (70°?7) (“room temperature”) to 177°C’ (35 l“F) is Nitrogen Alkali Metals Alumina
evaluated in this handbook. Vitiated Air Hydrated Salts
Noble Gases Carbonates
7-2 AGENTS Steam Phosphates
Foams
Although the following agents are divided into three
Surfactants
classes, (1) oxygen andlor fuel “excluders, (2) chemical
Copper Powder
intervention agents, and (3) cooling agents, some agents I
exhibit multiple fire-extinguishing mechanisms that overlap
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.—
(?) @
—
-—
.(!!9
TABLE 7=3. DIIXJEN’1’ST() RENDIIR A SPACE NONFLAMMABLE (Refs, 7,8,9,10,11,12,13, and 14)*
NORMAL NJrKrPrc Ti-Ii3w MOLECULAR LAmNT VOLUME % NEED133’R3
FORMULA TEMPERATuiUl 1301LlNG HEAT CONDUCI’IWTY WEIGHT HEAT OF RENDER A SPACE!
INDICATED PolNT A1’25°C AT 27*C VAPORIZATION NONFLAMMABLE
AND 1abn (nbp) FOR MEIMANE (C&)
g/rnL ‘c Jf(g.K) W/m.K ghol kJ/mol AT 25”C(7) AT 67”07)
Argon Ar II 0,001 7&4@*at O“c -1 85,4(8J1-R 0.519(9) 0.0178 l@) 3!3.948(9) 6.5@) 51 N/Avl
, 1 1
Helium I He g 0.0001 785(9) -268.9[9) g 5. 197@) o.1499[9) 4,0026(9) 5#97(1~) 38.5 N/Avl

-195.8@) g 1.038(9) 0.02598(9~ 28.01 34@ 5,6(U 38 N/Avl

lfJo(9) g 5040S) 0,018 1(9) 18.0153(9) 40,62(11) 29. I

Carbon CO* g 0.001977(9)at O*C subl g 0.875(9) 0.01660(9) 44.01(?1 sub!25.23 25 27. I
Dioxide triple point is -78.5 (g) (See table of
-56.6°C M 5.2 atm thermodynamic
}ropertiesofCOz
in Ref. 9.)
Carbon g 0.006879 76.8@) P 1.030( 13) 0.01036@) 153.81(91 29.6(Y) 11,5- 12.2 N/Avl
y Tetrrrchlorkle, P 10586720@)at20’C
4 Halon 104
Dichlorodi- CC12F2 g 0.0070 1(9) -29.79m 0.607@) 0.09665(9) 120.9 I@)
fluoromethwre, 0 i .31 1(9)M 25°C
HaIon 122
Inergenw Mixlure(14J 15 MPn (2175 Ib/in?) NIApp N/App NIAvI N/App N/App N/Avl NIAvI
N250 *5% maximum
Ar 40 * 4% containerpressure
C028* 1% at 21‘c (70°F)(’4)
HtO 0.5% by
weight mrrxi-
mum
g = gas Q = liquid
subl = sublimation v = vaporization
N/App = notapplicable N/Avl = notavailable
,
*Supcrscripk+in parcnlhescs inrticate the number Of the referenCe fmm
which the data were cxtmctd, e.g.,@) = Ref. 9.

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Ml~HD131G684
7-2.1.1 Carbon Dioxide X (1000 g).[1.T7°C - (-78.8°C)]
Carbon dioxide (COZ) is an ine~, colorless, odorless gas = 217.3 kJ.
.,
at nomnal ambient temperatures; however, it may be stored
as a liquid in pressurized containe~ at approximately 5.69. .The total heat energy absorbed from the air in the chamber
MPa at 21. 1°C (825 psi at 70”F). When released to flow is Ql+ Q~, or”160.5 kJ + 217.3 kJ = 377.8 ld.
through a nozzle into a large space, liquid COZ stored in a Most agents bat are used in the gaseous state are stored
pressure vessel at 5.69 MPa and 21°C (825 lb/in? and 7~F) as liquids. me fact that C02 can be stored and transported
will decrease in temperature to -78.8°C (-~10.02°F) At as a liquid at normal temperatures is advantageous when
standard atmospheric pressure it. will flash to a mixture of substantial- quantities of inert gas may be required for’extin-
gas (7290) and solid COZ (28Yo). No longef subjected to a guishing purposes since the volume of gaseous C02 at nor-
high pressure, the liquid changes to gas as it flows through mal ambient temperature and pressure is almost a thousand
the, nozzle. The energy required to accomplish this change times larger than that of its source liquid at the same tem-
in sthte, i.e., the latent heat of vaporization of 15.82 kJ/mol, perature. A strong bottle is required to store C02 for a
comes from the C02. Some of t.his energy” is’ generated by vehicular application; this bottle must be able to contain-the
lowering the energy level of the molecules, i.e., by lowering C02 ‘at approximately20.7 MPa (3000 psi), even though the
the temperature from 21 to –78.8°C, and the” remainder is probable storage pressure is 5.69 MPa (825 psi) at 21°C
generated by the change in state of some of ~e liquid to a (70°F).
solid. The change in state provides the latent heat of fusion Carbondlo~de is not effective against deep-seated Class
of 8.33 Ic.Vmol. This isenthalpic process for changes in pres- A fires, nor is it effective to cool heated metal. Once it has
.’sure and the resulting temperature and. svte of C02 are vaporized, ~Oz is quickly convected away from any
shown graphically by a‘ temperature-entropy chart or an exposed fire or from a vehicle engine that requires a high
... ..,. enthalpy-enmopy chart (Mollier diagram).’ These charts are flow rate of coolant air, Carbon dioxide is excellent for
available in standard reference ‘texts-such as Ref. 15 or extinguishing a ‘tie when it first-ignites, but is-very .pomfor
.
through the American Society of Heating, .Refrigerating, extinguishing a sustained fire. It cannot be projected from a
and Air-Condhioning Engineers, New York, NY. ‘ distance as a liquid such as water can. Because C02 is an
The mechanisms by which COZ extinguishes fire include asphyxiant it cannot be safely used in a confined space
., (1) reduced flame temperatures”resulting froln the high heat occupied by humans. Also firefighters should not enter a
capacity of C02, which is caused by dilution effects,. and “cloud” caused by release of C02 (The “cloud” <s actually
from energy absorbed during vaporization of the C02 snow, condensed water vapor, which is visible; the C02 vapor is
(2) blanketing of the burning material with the inert C02, not visible.) because they can breathe enough C02 to lose
and (3) cooling liquid fuel surfaces to below their flash consciousness and possibly be asphyxiated. .
points by contact with the. cold gas and solid particles. The Carbon dioxide is electrically nonconductive; hence it
,“
minimum concentration of added C02 needed to prevent can be used on Class .C fires as well as on Class .B and on
P ignition of all possible. diesel fuel-air mixtures (“flammabil- Class A fires burning on an exposed surface. Because..C02
,. ity peak”) is about 28’% (Ref. 2). can decompose into CO and 02 at temperatures above
~The” cooling effect of COZ can be estimated by using a 1700”C (31 OO”F9,it cannot be used on a Class D fire.
hypothetical case in which 1 kg of liquid CQ2 stored. in a
container at 21 *C” and 5.69 MPa is discharged through a 7-2.1.2 Oxygen-Depleted (Vitiated) Am
nozzle into a large chamber that is kept at 177°C at atmo- When a fiel-air mixture undergoes complete combustion;
spheric pressure. The liquid C02 will flash to 280 g of solid the final mixture contains carbon dioxide, water vapor, and
and 720 g of gaseous C02, which are at –78.8*C. The latent n$rogen. All of tiese gases are inert and hence cannot sup-
specific heat of ,mansformation Cf is equal to the latent heat port combustion. In the practical case of engine combustion,
of transformation H~ kJ/mol divided by the molecular the combustion products also contain. smaller amounts of
weight MW By using the values fiorn Table 7-3 and substi- carbon monoxide, unburned fuel and other pollutants, and
tuting into Eq. 7-2, the energy (heat) absorbed Q, by the unused atmospheric molecular oxygen. A properly adjusted
solid C02 when subliming to a gas is gasoline. engine uses approximately half of the available
Q,= (Hlm)vn atmospheric oxygen; the exhaust gases are primarily nitro-
= (25.23 kJ/mol/44.01 ghnol).280 g gen, water vapor, and carbon dioxide with some carbon
monoxide apd nitrogen oxides. A turbine engine uses
= 160.5 H.
approximately 20’% of the atmospheric oxygen; hence the
By using Eq. 7-1, the energy absorbed by the resulting 1000 exhaust gases include approximately 16’70oxygen as well as
g of gas by heating it from –78.8 (Cp, = 0.761 J/g.°C) to the other gases. A diesel engine uses approximately 10?tO
177°c (Cp = 0.938 J/g”C) is atmospheric oxygen at idle to approximately 65% atmo-
Q,= [(0.761 Jig “C+ 0.983 J/g.°C) /2] spheric oxygen at maximum poweq therefore, its exhaust
gases contain approximately 7 to 18% oxygen. Also there

7-8
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-are nitrogen, water vapor, and carbon dioxide and some car- nitrogen (LN~ usually is used.only to provide a source of
,,,1 , bon monoxide, sulfure oxides, and nitrogen oxides. When- gaseous molecular nitrogen (GN~. Gaseous nitrogen extin-
~‘$
0 ever some of the fuel is not completely burned, there are
SOOLsmalLparticles of carbon, and fuel vapors. Mixed in
guishes fire primarily by diluting oxygen but also by reduc-
ing flame temperatures through energy absorption. The
with these exhaust gases are some lubricating oil and some minimum concentration of nitrogen required to be added to
contaminants fiotn the mobility fuel andlor their combustion air to prevent ignition of all possible diesel fitel-air mixtures
m- (%mrnability peak”) is about 42’% by volume (Ref. 2). In
Tlmse gases that do not contain sufficient oxygen to tests of nitrogen imzrting of aircmft fuel cdl Wage, the
support swtakted combustiort*, i.e., c 14% oxygen by overpressures resulting -horn the detonation of a ZLmm
volume, can be used to prevent fires by diluting high-explosive incendimy tracer (HISIT) projectile were
atmosphericoxygen or to extinguish fires by blanketing the compared to ullages similarly protected by Halon 1301. The
fire and diluting the flame reactants. Such gases can also comparisons are shown in Fig. 7-2. Patt of the explanation
seine to a lesser extent as cooling agents. The vitiated air given in Ref. 17 for these results is that with a test chamber
pmbaldy contains unburned fuel vapor, SOOLand greakr- vohtme of 757 L (200 gal), the 23-mm HEIT detonation
than-atmosphenc proportions of water vapor and carbon would consume approximately 2% of the available oxygen.
dioxide. The minimum cortcerttration of vitiated air required Nkrogen is used in C-5A aircraft to inert the fuel cefl
to prevent ignition of all possible fuel-air mixtures Wages and to extinguish fires in 12 unmanned spaces
(%unrnability peak”) depends upon the completeness of i.nciuding leading edges of wings, wheel wells, underfioor
wmbustion and the fuel-air ratio of tie mixture burned to argo compartments,leading edges of engine pylons, power
form iq and only the spark-ignition engine removes transfer units, and dry bays of wings. Fm in any of these
atmospheric oxygen reliably. If vitiated. air can be obtained - spaces is WMed by separate continuous. thermal det~tors
-reliably, as a diluent the percentage used will be somewhere - that energize alarm lights on the tl.ight engineer’s nitrogen
~ between added water vapor (24$’b) and’ added nitrogen - fire suppression panel. ‘l%e fight engineer then armsand
(42%), both by volume. The water vapor when condensed activates the appropriate iire suppression valve (Ref. 16).
and the soot could present a problem in vehicle compo-
nents.

,,,,:’:;
,M
o I The principal disadvantage of vitiated air from piston
engines is its pollutant and high heat content- Such an inert-
‘‘ ing agent could foul the systems being inerted. This problem
would not necessarily be the case with gas turbine engines.
They, however, do not use sufficient atmospheric oxygen,
and their exhaust gases support combustion. ArI exhaust gas
iaerting system was explored for potential use on the B-52
aircraft but was rejected when development persome} found
d- .. -.
,.
that exhaust gas formed sulfitrous acid (H@03), which
attacked structural members (Ref. 16).

7-2.1.3 Nitrogen
ml.
Mrogen is an odorless, colorless, inert gas tit normal
ambient tempmtures It constitutes 78% of the atm~
sphere. It liquefies at -195.8°C (-320.4°F) at atmospheric m. ~ 11.%mttth ml
pressure and can be stored and transported as a liquid in
vacuum-jacketed or other insulated vessels. At ambie~t
temperatures it is commordy stored and tmnsported as a
compressed gas in high-pressure cylinders. It is commer-
cially available in both forms at reasonable cost. la .
In extinguishing or inerting applications liquid molecular mu- - la
0.—
*.m~m ~r to ~pmn SWstainedcombustion” does not m=
o m [m lW
thal there will be no combustion If there are multiple ignition
rmmlimem%xtlm
sources, such as the incendiary mixture fkom an armor-piercing
(B)L&#3bll!rMWl!ll&ll
130t
~ (~~ projectile m the burst of a high-exp]osiveincendi-
q (l-El) proyxxik combustion within a restricted volume may Figure 7-2. Overpressure Resulting From
t be ~ there may be sufficient products from the multiple
combwions to owrpreswrize the msricted volume
Combustion in Ullage of Fuel Cd Contain-
container. This overpressurimtion has occurred within some air- ing JP4 Given a 23-mm HEM’ Projectile
craft fuel ceIt utlages hit by API or HEl Proj=”ks. Detonation (Ref. 17)
7-9
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iVNL-HDBK-684
The use of GN2 as an extinguishant for engine: nacelle fires tutes 0.9370 by volume of theattnosphere, whereas nitrogen
has been consideredbut not selected. constitutes 7870. Argon liquefies at -185.4°C (–301 .7”F) at
The chief disadvantage of using “GNZ in extinguisher or atmospheric pressure and can be stored and transported as a a
inerting applications is the requirement for expensive: liquid in vacuum-jacketed or other insulated vessels. At
heavy, high-pressure storage vessels and ancillary equip-- ,‘ ambient temperatures it is commonly stored and transported
ment. as a compressed g~ in high-pressure cylinders. The mini-
The chief disadvantage of using LN2 in ext@wisher or mum added argon concentration required to prevent ignition
inerting applications is the requirement for ~expensive ther-’ of all possible diesel fuel-air mixtures -( ’!flmability
really insulated vessels and ancillary equipment. Another peak”) is estimated to be -similar to that for added nitrogen,
disadvantage is that liquid ‘nitrogen surfaces ex~osed to @ i.e., about 40 to 4570. The physical advantages and disad-
become oxygen enriched. Thus, given sufficient exposure vantages of using argon as an extinetishant are the same as
time, the stored LN2 can pose hazards equivalent to those of thoseof gaseous nitrogen.
liquid oxygen (LOX). This phenomenon occurs because the An agent that includes a noble gas is Inergenm, which is
liquefaction temperature of LN2 (-195 .8”C) is lower than .a mixttjre of nitrogen (50 k 570 by weight), argon (40 k
that of LOX (–183.0°C). Hence a portion of the atmospheric 470), carbon dioxide (10 *~ .lVO), and water (0.5% maxim-
oxygen can condense on the LN2 surface. ~ um). Inergenm is stored in the gaseous state at 15.2 MPa
Early in the space program, engineers attempted to utilize (220S lb/in?) in a thick-walled bottle. Approximately a 34%
he great quantities of liquid, nitrogen avtilable as a ... concen@ation of Inergenm is required to extinguish a fire
by-product from the liquefaction of air to ob@in liquid oxy- (Ref. 14).
gen. The LN2 was plumbed to the top of large liquld propel-
Iant engine test stands and released through nozzles when a - 7-2.1.5 Water Vapor (Steam)
‘tie occurred. When released, the LN2 quickly vaporized, Vaporized water (steam) functions solely as an inert gas
and “the”GNZ was rapidly dis~rsed by convection induced during extinguishing and inerting applications., It-.mtes
by the violent oxygen-rocket propellant fire; which effec- oxygen in the region of the flame by blanketing the fuel, ,and
tively removed the nitrogen before it could affect the comb- it lowers flame temperatures, by dilution. The minimum
ustion. added concentration required to prevent ignition of all pos-
sible hydrocarbon fuel-air mixtures (“flammability peak”) is
7-2.1.4 NoMe Gases about 24% (Ref. 1). A plot of Gibbs’ free energy versus
There are only three nonradioactive elements that have temperature (Ref: 18) indicates that water would probably a
been found to be chemically inert: helium, neon, and decompose near 4177°C (755 l“F), which is much higher
aigon, which are among those commonly referred to as than the temperature reached in combat vehicles fires.
noble gases. Each of these is an odorless; ‘colorless, ineq Unless steam is available as a by-product from another
gai at normal ambient temperature. The -temperatures at operation, such as a waste heat recovery system, the equipm-
.. ““which they. liquefy at atmospheric pressure range from ent and” energy required for its generation would b@iffi-
-269°C (-452°F’) for helium to -185.4°C (–301 .7°F) for cult to justify for @litary vehicles, Another disadvantage of
argon. Neon is the “most expensive of these three gases using steam is the requirement that all exposed surfaces be
and offers no advantages over the other two. - above the boiIing point of water, 100°C (212”F), to prevent
Heliumis used as an inerting gas when its low molecular condensation. Additionally, in the design and application of
weight and/or its complete chemical inertr!ess are appropri- steam extinguishing systems, precautions must be taken to
ate. It constihites only 0,0005% by volume of” the atmo- protectpersonnel from steam bums (Ref. 19).
sphere, so it is normally obtained fro~ limited supplies of
helium-rich natural gas. It can be stored and transported as a 7-2.1.6 Foams
liquid in vacuum-jacketed or other insulated vessels. At . . Aqueous foams suppress fires by. forming a blanket over
ambient temperatures it is commonly stored and transported the fuel to reduce or prevent the escape of fuel vapor into
as a compressed gas in high-pressure’ cylinders. The mini- the combustion zone above the fuel surface. ‘l%is action not
mum added helium concentration re,quired to prevent igni- only excludes fuel vapor but also provides cooling ‘of the
don” of all possible diesel fuel-air mixtures (“flammability fuel. For air foains, which are like soap bubbles containing
peak”) is about 4590 (Ref. 2); Helium affects the human air, the water, encapsulating agent, and/or other additives
vocal system and reduces the effectiveness ‘of verbal com- serve as the extinguishing agent. If the trapped gas is nome-
munication. active, e g., carbon dioxide, the efficacy of the aqueous
., Based on relative availability and cost, argon seems to be foam is enhanced relative to that of an air foam (Ref. 11).
the most practical choice as an extinguishant in this group. Aqueous foams represent a major class of extinguishants.
Other than its complete chemical inertness, -however, its Their types range from air bubbles mechanically foamed
characteristics are similar to those of nitrogen, which iS from water containing a foaming agent through bubbles
9
more abundant and less expensive than argon. Argon consti- foanied with an inert-gas blowing agent to air bubbles made

“.
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MIL-HDBK-W4
with a fluotited .swfactant that spark across the fuel sur- 7-2.1.7 Surfactartts .-7

0,:,,~
, face beneath the foam as an inert liquid film (Refs. 10 and
“‘“ 20 through 22). Other types of extinguishing foams include
.nortaqueous liquids foamed with nonaerobic blowing -
Surfactants are chemicals dissolved in water that reduce
the surface tension of the water. Surfactants thus increase
the ti]litv . of water to obtain an intimate contact with solid
agent& but appt&m.ly these have been used only in labom~ materials; surfactants are referred to as “weuing agents”.
tory studies (Ref. 23). Thus they increase the rate at which heat can be transferred.
Tn addition to the identity of tie Iiqui& gas, and foaming Water with a minute quantity of surfactant additive can bet-
agent in foams, other foam properties that may be varied ter soak into fabrics and can enter small passages between
inclu& the expansion ratio (volume of foam per vohmte of solid blocks.
liquid), drainage time (time to bubble coIlapse), and critical Surfactants are nonionic, anionic, or cationic. Nonionic
shear stress (foam stifhess). One or more additional com- surfactants, such as Tnton X-100@, generate fo~ are a
ponents may be added to the foam to enhance i~ effective- mild irritant to man, but are noncorrosive to metals. Anionic
ness. ‘Iltese components include surfactams and surfactants, such as Duponol@, are detergents and are alka-
halogenated extinguishing agents adsorbed on powders, dry line. Hence they can irritate skin and eyes and attack some
powders, or absorbents (Refs. 20,24, and 25). - metals, especially aluminum or magnesium. Cationic- sur-
Foams are arbitrarily classified as (1) low-expansion factants, such as quaternary ammonium sal~ emulsifjf fats
foam, expansion mtio up to 201, (2) medium-expansion and kill gems, are acidic, and hence can irritate skin and
foam, expansion ratio from 201 to 200:1, and (3) high-ex- eyes and attack some metals. Three surfactants that have
pansion foam, expansion ratio from 2(Hll to 10001 (Ref. been used for fim extinguishing are Sorbit ACH?, a mono
22). Foams are typified by protein-based foams having and dibutyl naphthalene sodium sulfonate (anionic) wetting
expansion ratios ranging from about 3: I to about 20 I and agent used in fire extinguishe~, Triton X-lOO@, an alkylated
by synthetic &tergent foams having expansion ratios rang- aryl polyether alcoltol (nonionic) wetting and dispersing
ing up tb 10001 (Refs. 20 and 21). The low-expansion agent also used in firefightin~ and RN-200!?, an alkykaryl
foams are used primady to blanket pool fires, to exclude sulfonate (anionic) detergent and wetting agent used as a
t%el vapor, and to provide cooling. Medium-to-high expan- water spreader for fires (Ref. 27).
sion foams are well suited to ~ cavities and enclosures and When water containing a surfactant is applied to an
,,:,:,, thereby exclude fuel vapor and provide cooling (Ref. 22). ignited oil-fibn-covemd pool of water, the surfactardwater
,,~>~~!,
~ Foams containing a fhorinated surfactant are character- solution spontaneously pushes the layer of burning fuel
o vapor away from the point of applicaaon and thereby pro-
‘ ized by their ability to form a continuous, self-healing film
of surfactant over the surface of liquid fiels and thus retard vides aflame-free region on the pool surface (Ref. 2S). Thus
fuel vaporization. Foams of this type arE refereed to as aque- the fire is either diminished in size or extinguished. Practical
ous film-forming foams @FFF) and film-forming fluor- applications of this phenomenon have not been developed-
protein @FFP) agents. AFFF, also known as “light water”, Some additional benefits from surfactants are given.in sub-
consists of synthetic substances that are basically deter- par. 7-2.3.1.3. --- .. ..
gen~ some of which are fluorinated materials. FFFP is Both surfactants and foaming agents provide a layer over
camp~ed of protein and ti-foming fluorinated surt%c- the fuel. Whh only a surfactant this layer is thin, but with a
tants, which exhibit a fuel-shedding capability, i.e., if the foaming agent the layer is thicker and consists of bubbles
foam becomes coated with fuel, the foam sheds the fuel with inert material that not only inhibits the rking of the
readily. AFFFs and FFFPs can be used in conjunction with fuel vapor into the air but also insulates the fnel. AILfoam-
dry powdm without reaction problems (Ref. 22), but the ing agents contain surfactants.
foams and their water carriers will trap the dry chemicals
away from the flame. 7-2.1.8 copper Powder
Absorbents, such as bentonite, in conjunction with foams, When blown onto burning lithium, magnesium, or orher
have been used only in airdrops on forest and brush fires combustible metals, copper powder or flakes melt and alloy
(Ref. 26). Foams are excellent for extinguishing pool fires, with the moIten metal on the surface of the combusting
but are not practical to extinguish a fireball. Once a t%e has ~metal (Ref. 29). This alloy forms a skin on the surface of the
been extinguish~ the foams do not COOIhot metal objects molten base metal, which prevents ftier combustion.
as effectively as water. Foams, particularly protein foams, Copper powder is the basic ingredient in Navy 125S@,
contaminate the fire site and present a problem in postfk’e which is used for combustible metal fires. (See subpar. 7-2.4
ck.anup. lle greatest advantage of using a foam to extim for the ilre extinguishants effective on combustible metal
guish a pool fire is that the foam will film over the liquid *.)
fuel surface and form a banier between the fuel and the air.
,,,,,,
!: ,: Foams do not enhance the capability of water to extinguish
7-2.2 CHEMICAL INTERVEN9XON AGENTS
o,1,
/, a Class A fire. The chemical intervention class of extinguishing agents
appears to function by interfering with the fkee-radical

7-11
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NIIL44DBK-684
(molecular fragments andlor atoms) chemical chain reac- Having appropriate wilues..for the specific heat of the
tions discussed in par. 2-2 as opposed to extinguishing materials involved is essential to computing the heat
agents mat use physical means, such ~ cooling, diluting, or involved. in this process. Some values for specific heat,
providing a btier, to extinguish a fire. “ which vary with the state and temperature of the substance,
A major disadvantage of chemical intervention agents is are tabulated in Table 7-4. In some instances more appropri-
“ihat we most effective agents form potentially toxic com- ate values of specific heat CP are needed. Empirical fit equa-
bustion or pyrolysis products. Some solid agents, however,. tions for specific heat are given in Ref. 9 and Ref. 33. These
can serve as free-radical traps without’ developing combus- equations are in the form
tion’ or pyrolysis products (Ref. 30).
“ Not all chemicals tested as extinguishing agents are Cp = a + bT + CT= + dlz J/(g-K) (7-9)
included in the following subparagraphs. Only those that
have been shown to, or may be. expected to, have practical where
potential as agents are included. Cp = specific heat at constant pressure, J/ (g.K)
,,Examples of chemical intervention agents are @e halons,
a, b,c, d= converted empirical constants in Table’7-4,
e.g., bromotrifluoromethane (CBrF3)j wfich is known as .
J/ (g-K) “’
I-Ialon 1301, and the dry chemical powders, e.g., potassium
T= temperature, K.
bicarbonate (KHC03). Typically, these materials decom-
pose, when exposed to heat and provide some inert diluents” ,.
and some molecules that attract and trap free radicals and Because the equations are empirical, the coefficients. are
ions. valid only over the range of temperatures from which they
If 1 kg of. potassium- bicarbonate (KHC03) powder at were derived.
21 ‘C were blown into a confined volume maintained at
177°C the powder would heat to 170°C and lower the aver- 7-2.2.1 Alkali Metal Salt Powders .-
age temperature by absorbing energy from the volume. The Alkali metal salt powders are an important class of extin-
KH~03 would then decompose and lower the average tem- guishants, and their role in extinguishing flames has been
pera~e of the volume greatly by absorbing more energy. studied extensively (Refs. 7, 25, 30, 35, and 36). Their
The temperature of the decomposition products of KHC03 extinguishing effectiveness is proportional to the surface
would then increase to 177”C, and they would absorb addi- area of the powder (The powder must be ground into fine
a
tional heat energy. The decomposition process follows this particles.), and it increases as alkali metals of higher atomic
formula weights are employed. Hence the extinguishing effective-
ness increases in this order: lithium, sodium, potassium,
2KHC03 + q + K~coJ + I-I~o + CO*. rubidium, and cesium. (Frartcium has the highest atomic
weight ,but is radioactive.)
By using the values in Table 7-4* atid Eqs. 7-4 through 7-8, The formation’ of decomposition prodttcts, such-X-the
this process is expected to provide a cooling effect and ~~ carbon dioxide produced by pyrolysis of a carbonate
“”result in the removal of approximately O.SW- MJ of heat powder, contributes to flame extinguishinenc however, the
, energy from the volume; it consumes the 1 kg of KHC03 dominant mechanism by which alkali metal salt powders
,and generates 690 g of K2C03, 220 g of C02, and 90 g of extingtiish flames appears to be the interruption of the
H*O. .. free-~adical chain reactions. Also it has been suggested that
flame opacity caused by powders also provides cooling by
*The specific heat CP of KHC03 is not available in any literature shielding the fuel from thermal radiation (Ref. 25). Saks
searched to ‘the “dateof writing including Me reference database “of such- as carbonates and tartrates, which decompose readily,
the National Institute of Standards and Technology (MST) and are especially. effective (Ref. 30). Sodium bicarbonate
Defense Technology Information Center (DTIC) database. There- (NaHC03) and potassium bicarbonate (KHCOQ are the
fore,. for this example, the constant average value of 0.9022 J/(gK)
most commonly used alkali metal salt powders.
is assumed because KHC03 is close in molecular swcture ~to
K2C03 and NazC03. This approximate value of CP for KHC03 A rrtinor”disadvantage of solid extinguishing agent pow-
could be used in. Eq. 7-1 as a “first guess” to compute the heat ders is the residual extinguishing agent that often remains in
required to raise the temperature from Ti to Tf Because the multiple the general area of the fire incident and that can result in
crystalline (solid) states of KHC03 are not stable, a single vatue or damage to fine machinery and a need for cleanup following
an equation for the Cp of KHC03 is not truly vflld. ?hpirical data
the incident.
and experimentation are required to verify any engineering calcula-
tions.

7-12
 @
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-.
c!!?
TABLE 7-4. PROPERTIES OF DRY CHEMICALS AND PRODUCTS THEREOF (Rei%,9,31,32,33, and 34)
(A) PROPERTIES
tlOLECULAR GIBBS
WEIGHT,
ghnol mT:Y
7 IWmol
1I o,99(9)t = 1940 -795.8 -748,1
at I 3QC

7
246.4W -3388.71 -2871.9 c 1.5107(33)

I
T
Magnesium MgSO~.H+2 138.39@) C2,445~g) -1428.8
sulfate
Monohydrnte
Magnesium MgS04 120.37(9} -1147 Hm 14.6 c 0.7593 at 8°C(33~
Sulfate + I C0.9281 at 23-99°C
Ammonium NHiHtPO, I I 5.03(9) C 1.803 d 190 -1145.07 -1210sf c 1.2338
Dihydrogen at 19’JC
Phosphateor
Monoammonium
Phosphnte
(MAP)
Ammonia NH3 17,04(9) -33.35 -45.9 -16.4 Hm 5,652 g 2.0921
at 4°C g 2.2723 at 127°C
-30.9~ Hv 23.35 g 3.315 I at 727°C
Phosphorus P40,fj 283.88(9) 360 -3009.9 -2773.3 Hm 34,3(3’) C 0.7458
Pentoxide subl at 89°C Hv 95.0(3’) c 0.9168 at 127°C
Hs 106.0f3’) c 1.1836 aL327°C

=7- T
98. 15P) -724.7@) c I .14 ftt 20YW)
c i .74 at 40°C
c 2,90 at 10O°C

E=t-
Potassium
Carbonate
KiC03
loo.12~9)

138.20(91 C 2,29
,
901 d to K20
and COZ
-963.2

-1150.2
at21°C
-863.6

-1064.5
I “o.9022tt

-t--

T
94.20 -3221

1 +
_-E!I&& (conl’d on next pngc)
 :,-, ~..,, .3 .’, ,.. .

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,“. ,“, ,, .,

TABLE ‘7-4.(cent’ ,.

===rzF
SUBSTAN~ W7vl130LOR hOLECULAR DENSITY, BOILING HEAT OF G~BS LATENT mzm SPECIFIC
FORMULA WEIGHT, POINT, ?ORMATION, FREE OF HEAT C , J/(gK)
~mol
I “u “c kJ/mol ENERGY,
kJ/mol
IllANSITION**,
IcJlmol
AT ~5°C

Potassium KOH 56.11 1323 -424.7 at 4°C -378.9 Hm 8.6 C 1.1567

Hydroxide Hv 142.7 c 1.2773 at 127°C
1360.4f0.7~9J kk 192 c 1,4019 at 327°C
! 1.4812 at
100-1000”C
Carbon co, 44.01 g 1.975 atO°C –78.44 subl .393.52 at 5°C -1394”.39 Hm 8.33 g 0.761 at –73.3°C(13)
Dioxide C 1.512(31)* HV 15.82 g 0.8437
Hs 25.23 g 0.9389 at 127°C
,. g 1.2340at 727°C
C2.052 at –50°Cf13J”
02.847 at 4°Ct131
t 5,652 at 23°C(13J
t 35.67 at 30°C(13)
c 4.494 at –78.8°C(33)
Hydrogen HZO 18.0153(9) [00.00 -292.72 Hm 6.@9 C2.0599
y“
Oxide + -285.83 -237.14 Hv 40.66 Q4.2159
& -241.84 –228.61 g 1.8651

=1=
Aluminutn 101.96(9) c 3.97(9) 2015+ 15(9) 2980+60{9) -1676.0 -1582.3 Hm 111,0 C 0.1763
Oxide c 0.9424 at’127?C
c 1.2237 at 727°C
Copper Cu 63.546(9) 8.92(9) 1083.4(9) 567@) o o Hm 0,206 C0.3846
Hv 4.727 c 0.4510 at 727°C
10.4937 at 1727°C~g)

T
Nitrogen N2 28.0134(9) g 0.001506(9) –209.86(9) -195.8(9) o 0 Hm 0.0257 g 1,040
[ 0.8081 HvO.1991 g 1.044 at 127°C
at –195.8°C g 1.161 at 727°C
Carbonic HlC03 62.03(9) -698.73 -623.42
Acid (Aqueous at 25°C(9) at 25°C(9J
Solution)
Oxygen 3 1.9988(9) 182.962(9} o 0

*State: c = crystalline or solid, 0= liquid, g = gaseous

-J subl = sublimation
**Heats of Tr&sition: Hm = meltin~, Hv =-vaporizing, HS = subliming nbp = near boiling point
Preference for data is Ref. 34 unless otherwise indicated by the superscript reference number in par’ nthcses. d = decomposes
~tSee footnote to subpar. 7-2.2. ; r I
/
(cent’d on next page)
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I
MIL-HDBK-684

TABLE 7-4. (cent’d)

oi~~
@)
COW-S
J,
---- SUBSTANCE STATE*
FOR EQ. 7-9
CONSTANT a, CONSTANT b, CONSTANT C, CONSTANT d, TEMPERATURE
J/(g,K) J/(gm J/(g.K) J/@K) RANGE, K

Calcium fj.vm” 0.6371 1.455 x Iv o 0 273-1055

chloride
Magnesium @3) 1.5107 0 0 0 291-319
Sulfate
Heptahydrate
Magnesium @3) 0.9977 0 0 0 282
sulfate
Monobydrate
- Magnesium C(.33) 0.9281 0 0 0 292-372
Sulfate
Ammonia gtm 1.6451 1.547 x 10-3 0 0 300-800
Phosphorus &w 0.2317 1.609 X lW o 0 273-631
Pentoxide #u) 1.0848 0 0 631-1371
Potassium ~cw 0.9052 0 0 0 296372
Carbonate
Potassium cm 0.7062 2.843 X 1(V o 0 273-1373~
Monoxide
Carbon Dioxide gm 0.9830 2.605 X ltY o -i.859 X l@ 273-1373~
F) 0.7320 5.039 x lW -7.891 XI@ o
,,,,:,,,,
Hydrogen Oxide l?) 2.601 1.665 x 10-3 0 0 273-373?
fgG3)
o
‘:,j!r
,,!
Aluminum @
1.909
1.072
3.484 X lW
1.801 X 1(P
3.122 X l&7 o
-2.9830 X 10’
300-2506
273-19737
oxide cm) 0.9061 3.681 X lW : -2.1440 x I(Y 273-1973
copper CQ3) 0.3582 9.626 X l(FS o 0 273-1357
cm 0.2700 6.716x I&s o -1.383 X 1(Y 273-1357~
&w 0.4938 o 0 0 1357-1573
Nitrogen #3) 0.9708 1.494 x lti o 0 30@3000 ‘—
P 1.0097 9.051 x 10--$ 1.942 Xl@ o 3oo-3ooot

‘State c = crymdline or solid, Q= I@@ g = gaseous

**sU~@ ~ -~e indj~e the num~ of the ref~m tim which the &ta were exti except for the ternperamre ~ges
estimated by the author.
W&mated by the author.

7-222 U Metal Salt Aqueous Solutions

I%e extinguishing effectiveness of water sprays is alkali metal. It also increases with increasing oxygen con-
enhanced by the presence of dissolved alkali metal salts, but tent of the anion attached’ to the MI metal cation. For
it is not influenced by the salts of other metak (Ref. 7). example, 40% less potassium chlorate (KC103) solution
Table 7-5 presents a summary of the relative effectiveness of than potassium chloride (KC}) solution is required to extin-
experimentally measured minimum masses of alkali metal guish a gasoline pool fire, and 80% less potassium perchb
salts in water in extinguishing gasoline pool fires. In these rate (KC104) solution than potassium chloride solution is
tests a jet of the aqueous solution struck a target above the required. lle extinguishing effectiveness also varies with
w * and droplets of various sizes splattered onto the the type of anion attached to the alkali metal cation. For
gasoline surface. example, the chlorate is more effective rhan the bicarbonate,
::!’ As it does for alkali metal salt powders, the extinguishing
,;::’;, which is more effective hut the chloride, which is more
o ‘ :“ ffe.ctiveness increases with increasingatomic weight of the effective than the carbonate.

7-15
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M[L-~DBK-684

ZABLE ‘7-5.RELATIVE EFFEC-NESS ~FA~UEOUS SOLlkIONS OF ALKALI METAL

SALTS USED TO EXTINGUISH GASOLINE PAN FIRES (Refs. 9,31, and35) @
MASS* OF
,. SOLUTE PER
MOLECUL@ LITER OF
WEIGHT, SOLUTION,
SALT FORMULA g/mol W EXTINGUISHED
Cesium Chloride Cscl 168.36 134.7 Yes
Rubi@m Bitartrate RbHC,H,Oc 234.55’ 17.6 Yes
Chloride RbCl 120.92 120.9 Yes
Carbonate RblCO~ : 230.95 173.2 Yes
Potassium Bitartrate KHC4H406 188.18 14.1 Yes
Perchlorate KClO, 138.55 27.7 Yes
Bichromate K2Cr20T 294.19 29.4 Yes
Hydroxide KOH 56.11 33.7 ,Yes
Fluoride R 58.10 34.9 Yes
Citrate K@H~OT.HzO 324.34 43.2 Yes
Anthranilate KC7HCNOZ 175.22 43.8 Yes
Permanganate KMno4 158.04 ‘ 47.4 Yes
13utyrate CH@Iz.COOK 126.19 50.5 Yes
,, Gallate KC7H~O~ 208.21 62.5 Yes
Iodate K103 214.00 64.2 Yes
Formate KC~O, 84.12 67.3 Yes
Acetate KC2H~02 98.15. 68.7 Yes
‘,
Bicarbonate mco~ 100.12 70.1 Yes
Chlorate KCIO~ 122.55 73.5 Yes
Chloride KC1 74.56 74.6 Yes
Nitrite KNO* 85.11 76.6 Yes
Tartrate KIC&AO#/2Hz0 235.28 94.1 Yes
Iodide KI 166.01 99.6 Yes
.’” Oxalate K2CzOq.H20 184.24 101.3 Yes
Carbonate KzCO~ 138.21 103.7 Yes
Lactate KC3H503.3H20 182.22 109.3 Yes
Nhrate KN03 101.11 111.2 Yes.
Bromide KBr. 119.01, 220.2 Yes
Bromate KBro3 167.01 250.5 Yes
Phosphate K~POi 212.28 283.0 Yes
Hydrogen Sulfate KHSOA 136.17 680.9 No
Sodium Acetate NaCzH~02 83.02 83.0 Yes
Nitrate NaNOJ 84.99 255.0 Yes
.“ Chloride NaCl 58.44 274.7 Yes
,,’.. Potassium Carbonate NaKCOJ.6Hz0” 230.19 287.7 Yes
., Bichromate Na2Cr207-2H20 298.00 298.0 Yes
, Lactate NaC$k~O~ 112.06 392.2 Yes
Tartrate Na2H.C,0b.2H20 230.10 1380.6 No
Diphosphate N@-IPOq ** No
Triphosphate Na~PO1 ** No
Silicate Na2SiJ07 40.070 No
.,
Lithium Acekte LiCzH~Oz.2H20 102.01 510.1 Yes
Chloride LiCl 42.39 635.9 No
,,
,’ Nh.rate LiNO~ 68.94 689.4 No
,. Li2C,#I~07.4H@ 281.98 845.9 No
Citrate

*Least mass per liter of solution that extinguished fire

.,.!.
**Saturated solution a

,,
,, 7-16
.’
.
,.
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MIL-HDBK-684
7-2J23- -Halogen-Containing Hydrocarbon Com- the toxicological effeets rtfdxomochloromerhane and its
pounds pyrolysis products on guinea pigs. l%e pyrolysis studies
Hydrocarbons containing halogen atoms, i.e., fluorine, were conducted with various heat sources including an illu-
chlorine, bromine or iodine, are commonly referred to minating gas flame and gasoline, ethyl alcohol, and wood
generically as halons, halogenated hydrocarbons. Many fires. This conclusion was reached: “Under ordinary condi-
halons are proscribed by the Montreal Protocol of 29 June tions prevailing in fires in well ventilated places, particu-
1990 and subsequent IX Government action. This class of larly in the ease of incipient and small fires, the
compounds exhibits greater flame extinguishment effective- concentrations of Httlon 1011 (bromochloromethane) and
ness particularly when used in a dilute quantity, than could its themxd decomposition products may not endanger life
be attributed to physical effects such as fuel blanketing or on temporary exposure, but in small closed places such as
reduction of flame temperatures by dilution, by increased vaults, closets, or small basement rooms, where the prompt
heat capacities, or by cooling. Extensive research has con- exit of persons is not possible, there is danger.” (Ref. 39).
ilrrned that this enhanced extinguishment effectiveness is a
result of interference with the free-radical chain reactions 7-2.2.3.1 The Seareh for Halon Replacements
proceeding within the flame (Refs. 3, 7, 30, 36, and 37). antior Alternates*
These studies have provided extensive tabulations of the At the time this handbook was written, halons containing
relative effectiveness of various halons. Table 7-6 presents a chlorine and/or bromine were being phased out of use as
summary of the rdative effectiveness of halon agents (Ref. refrigerants, solvents, pressurartts, and fire extinguishants.
3). The relative effectiveness of these agents may vmy Potential alternative materials for use as fire extinguishrutts
depending on the test conditions. were being evaluated for their ozone depletion potential
In tlte absence of extinguishants free radicals (molecular (ODP), global warming potential (GWP), toxicity hazard,
fragments anthr atoms) in the flame react among them- and ftre-extinguishing capability. The ODP was evaluated
selves to form more free mdicals than are consumed in the as a function of chlorine and bromine content. The--model
various reaction steps. Hence the reactions proceed ever for this evaluation was being upgraded to include molecules
faster until all reactants are consumed. A popular explana- containing iodine. Evaluation of global warming potential is
tion of the effectiveness of halogen-containing agents (Ref. dependent upon computer models that are still being devel-
30) is that they are capable of producing relatively inert oped. The toxicity hazard was evaluated using hvo different
,j$ c ogen-containing free radicals thal compete with the more measures. One measure established the lethal concentration
o reactive free radicals and atoms in the flame. Thus the net of the vapor(s) of the agent in air, which is defined as the
rate of fomation of excess free radicals is decreased, and concentration at which half of a number of rats exposed for
the reaction rates deerease until with sufficient agent flame four hours die, the L% The other measure, which is the
extinction is achieved. Table 7-7 compares the characteris- cardiac sensitivity threshold (CST), is established using
tics of selected halons to desired military characteristics dogs exposed to vapors until irregular heartbeats develop.
(Ref. 3). Both of these measures are controversial. The LC50 criterion
When halons are subjected to high temperatures such is better suited for evaluating the hazard in a production
as those reached in ammunition tires. they can decom- pkum and the CST criterion has been questioned for the
pose and yield toxic gases. A study of the use of Halon applicability of dogs’ reactions to humans’ reactions. Tbe
1301 (bromornfluoromethane) as an extinguishant for preliminary criterion for fire-extinguishing capability has
enclosure fires indicated that the concentrations of halo- been the cup burner test, in which the volume percentage of
gen-containing pyrolysis products were less hazardous the extinguishant in air needed to extinguish a heptane fire
than the cormmrations of fuel combustion products pro- is established (Ref. 14).
duced in the tests conducted for the study. It was also
observed that the duration of the extinguishant di@arge ‘*“Replaeement” denotes a fire extinguishant that is cbeniically
detemnined the amount of products formed (Ref. 38).. similar to halorts; “akernare” denotes a tire extinguishant that is not
Resistance to pyrolysis varies among the hrdons, as illus- ehernieally similar [o halons, e.g., water, carbon dioxide, or a pow-
trated by the “white rat” toxicity data of Table 7-8. Refs. 3, der such as potassium bicarbonate or monoamrnonium phosphate
(Ref. 40).
37, and 39 describe a comprehensive experimental study of

7-17
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MIL+IDBK’684

TABLE 7:6. hIDWWUM CONCENTRATION OF HALONS REQUIRED FOR INERTING ALL

CONCENTRA~ONS OF HEFTANE IN .IR (Ref. 3) e
....
MINIMUM CONCENTRATION
COMPOUND FOR INERTION
COMPOti’NAME FORMULA VOLUME, ~0
Dibromodifluorofnethane CBrlF2 4.2
Tribromofluoromethane CBr~F- 4.2
2-Bromo- 1,1, l-trifluoropropane ~ CF~CHBrCH~ 4.9
1,2-Dibromotetrafluoroethane CBrFzCBrFz 4.9
Tetrafluoro- 1,2-diiodo&thane CF21CF*I 5.0
Dibromomethane CHzBrJ 5.2
Pentafluoroiodoethane CF3CFZI 5.3
3-13romo- 1, 1,1-tiifluoropropane CF~CHzCH,Br 5.4
Ethyl Iodide CH@321 5.6
Bromopentafluoroethane CFJCF2Br 6.1 .
Methyl Iodide CH~I 6.1
Bromotrifltioromethane CBrF~ 6.1
Ethyl Bromide CH~CH,Br 6.2
l-BromoT2,2-difluoropropane ‘. CH2BrCF2CH, 6.3
2-Bromo- l-chloro- 1, l-dlfluoropropmie CCIF,CHBrCHg 6.4
Dibromofluoromethane - CHBrzF 6.4
1,2-Dibromo- 1,1-difluoroethane “’ CBrFICHzBr 6.8
2-Bromo-1, 1,1-trifluoroethane CF,CH,Br - 6.8
Perfluoro(ethylcyclohexane) 6.8
Perfluoro(l ,3-dimethylcyclohexane) 6.8
Perfluoro(l,4-dimethylcyclohexane) 6.8
Trifluoroiodomethane 6.8
l-Bromo-2-chloroethane CHIBrCHzCl 7.2
2-Bromo- l-chloro- 1, l-difluoroethane CClF2CHzBr 7.2
Perfluoro(methylcyclohexime) CbFLICFa 7.5
Perfluorobeptane C7F1b 7.5
Bromochloromethane ‘ CH,BrCl 7.6
Bromodifluoromethane . cHBrF2 8.4
1, 1,2-Trichlorotifluoroethane CC1FZCC12F 9.0
Bromochlorodifluoromethmie : CBrCIF, 9.3
Hydrogen Bromide HBr 9.3
Methyl Bromide CH~Br 9.7
2,2-Difluorovinyl Bromide CFz=CHBr 9.7
Perfluorobutane. CIFIO 9.8
1,2-Dibromo-2-chloro- l,1 ,2-trifluoroekane CBrFzCBrCIF 10.8
~,2-Dichlorotetrafluoroethane CCIF2CCIFZ 10.8
Carbon Tetrachloride ccl. 11.5
2-Chloro-’l, 1, l-trifluoropropane CF~CHCICH~ 12.0
3-CMoro- 1,1, l-trifluoropropane cF3c~,cH,cl 12.2
Chlorotrifluoromethane CclI?, 12.3
Hexafluoroethane CF~CF~ 13.4
Dichlorodifluoro’methane CC1ZF2 14.9
Chloroform CHC13 17.5
Trifluoromethane CHF3 17.8
Chlorodifluoromethane’ CHC1F2 17.9
Octafluorocyclobutane C,FB 18.1
Hydrogen Chloride HCI 25.5
Carbon Tetrafluonde CFd 26.0
,....

7-18
,-’,
,,. .
 —.
.—
c!?
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@
.-
@

TABLE 7-7. COMPLIANCE OF SELBCTED EIALONS ‘Ill lWJTAIW CHARACTERISTICS (Ref. 3)

CARBON BROMOCHLORO- BROMOIIUFLUORO- DIBROMODl-
MLITARY MIWHYL 13ROMIIM TIYrRAC1-lLORI1313 MIWHANE MBTHANE FLUOROMETHANE BASIS OF
CHARACTERISTICS (HALON 1001) (HALON 104) (HALON 1011) ((HALON 1301) (HALON 1202) COMPARISON
The agent shall be suit- Apfrroximnkdy twice Compnrntor Approximntcly 1315 Approximately [wice Approximately twice Lnhomtory data
able for use in combating 8s effeclivc nscarbon (13nscline) nscffeciive oscnrbon as effcctivc ascnrbon nseffective oscarbon (Ref. 3)
fires of ChwscsB and C. tetrnchloride tetmchloride tctrnchlori(tc tctrnchloridc
‘l%c agent shall not be 5 limes nstoxic m Comfmrntor Approximately 1/2 ns 1/28 as toxic m carbon 1/2 as toxic nscnrbon Approximate lethal
more toxic lhrin carbon tclrnchloride (Bnscline) toxic as carbon tetrnchloridc tetrnchloride conccntration
cnrbon tetmchloride, tclrnchloridc [Ref. 13)
“Ilw agent shall be suit- Suitable Solidifies at -22*C Suitable over entire Suitable over cn[ire Suitable over entire Cold chamber tesls
able for uscat (cmpcra- (-7.6”F); requires temperaturerange temperaturerrmgc; tcmpcrnturerange
turcsfrom 710 to -54°C wintcrkltion more effective Ihnn
(160° tO -65°f7), dibromodifluoromcth-
nneat -54°C (-65”f9
The ngentshall not deteri- Stablc understorngc SInblc under slornge Stable under stornge Higher stability than Higher stability thnn
omle when tmnsportedor conditions conditions conditions methyl bromide or methyl bromide or cnr-
y when storedfor up to five carbon tctrachloridc bon tctrnchloridebe-
1
years under nny I
bccrwscof fluorine causeof fluorine
G
climatic conditions, content content
The ngcn[may bc in commercial In commercial In commercial Producedby Producedby
producedin quan[ity production production production fluorinnlion processes fluorination processes
within rensonnblecost ‘- ~ as usedfor the as used for the
limi[s and with existing productionof frcon- productionof frcon-
productionfacilities. type refrigerants (ype refrigerants

“I%ecorrosive effects of Noncorrosive10com- Slightly corrosive Slightly corrosive; Noncorrosiveto com- Anticipated to be non- Laboratory dnta
thc ngcrrlshall not bc mon mctcds (negligible when in- most corrosive to mon metals corrosive to common (Ref. 3)
greater lhan thoseof stnn- hibitcd by tmccsof aluminum mcttds
dmd cnrbontetrnchloride CSZ); mos[corrosive
fire to aluminum under
extinguisherfluid. aqueousconditions
The agent shall bc a non- Nonconductor Nonconductor Nonconductor Nonconductor Nonconductor As n clnss,all of
conductorof thesengentsare non
electricity. conductors.

I
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NUL-HDBI$-684

TABLE 7-8. APPRO?@lA~ LETHAL CONCENTRKHON FOR SELECTED HALONS (Ref. 3)

a
APPROXIMATE LETHJWCONCENT’RATION
NATURAL VAPOR VAPOR PYROLIZED IN
AGENT FORMULA HA+ON IRON TUBE AT 800”C
mg/L ppm mg/L. ppm
Bromotrifluoromethane CBrFJ 1301 5075 800,000 86 14,000
Carbon Tetrafluonde cF~ 14 3220 512,000 3220 512,000
13romochlorodifluoromethane CF2ClBr 1211 .2200 324,000 52 7,650
Dibromotetra.fluoroethane CFzBrCFzBr 2402 1340 126,000 17 1,600
co, ‘ ,_ 1180 100,000 1200. 102,000
Carbon Dioxide
Perfluoromethylcyclohexane C,FllCFg GK(M) 1165 81,000 117 7,500
Ethyl Bromide ~ CzH~Br 2001 660 148,000 75 16,500
.. Dibromodifluoromethane Cl?,Qr2 1202 470 54,000 16 1,850
Chlorobromoethane CH2ClBr 1o11 340 65,000 20 4,000
Dibromochlorotrifluoroethane CCIFBrCF,Br 2312 285 25,000 “8 700
Dibromodifluoroethane CH,BrCFzBr 2202 190’ 20,700 110 12,000
Carbon Tetrachloride ccl.. 104 180 28,000 2 300
Methyl Bromide CH@ ,1001 23 5,900 60 9,600
Methvl Iodide CHqI 10001 ““ 22 3,800 350 ,60,500

7-2.2.3.2 Halott.Replacements ., devices, These devices bum a solid mass to produce a dust
Evaluation of halon replacements is hindered by lack of a cloud of dry chemical, which probably contains potassium.
validated means to judge candidates. The NET has docu- These “dus~ generators are cooled, usually with water, to
mented procedures and cnitena for replacements, for Halons preclude adding heat to the fire site. The dust produced
1211 and 1301 (Ref. 41). There has not been a consensus, floods the fire site. Once ignited, the “dust” generator must
however, among the personnel selecting the halon replace-” burn to completion. At this time, no research has been per- 0
ments on how to predict the long-term effects of a material formed on the reactions of humans to this extremely fine
on either ozone depletion or global w@ng. Thus this. powder, which is reported to be micron size, that would be
balon replacement selection effort is in a state of flux at this extremely difficult to keep out of the lungs of vehicle crew-
time. NIST presented an exploratory list of replacements in men. The effects upon crewmen should be explored before
Ref. 8. “Some of the near-term replacements, which. were such devices are installed in crew compartments of combat
under consideration in 1992, are described in Tables 7-9 and vehicles. (See subpti. 5-6:2.2 for discussion of particles-this
7-1o. size.),

7-2.2.3.3 Eklon ANermates 7-2.2.4 Halogen-Containing Nonhydrocarbons

The lack of selected halon replacements has encouraged Various halogen-containing nonhydroc~bon extinguish-
the review of previously used or disc~ded fire extinguish: ing agent candidates have been evaluated in research stud-
ants. These include water, dry chemical ,powders, carbon ies. These included gaseous aluminum chloride, sulfur
dioxide, and other agents that lacked some of the favorable, hexafluoride, sulfuryl chloride, boron trifluoride, phospho-
attributes. of halons. NIST included halon alternatives in” rous trichloride, phosphorous oxychlonde, trichlorosilane,
Ref. 8. Descriptions of the advantages and disadvantages of and silicon tetichloride -(Refs. 3, 7, tid 30). The volatile
some of these alternatives are given, i.e., water in subpar. hydrogen halides were included with the halogen-comain-
7-2.3.1, carbon dioxide in subpar. 7-2.1.1, and dry powder ing” hydrocarbons in subpar. 7-2.2.3. The candidate agents
in subpar. 7-2.2. that appeared most promising rho presented toxicity haz-
Both Spectrex and Kidde-Graviner are developing ards;” therefore, they are not recommended for use in the
extremely fine dry chemical extinguishant generation crew” compartments of military combat vehicles.

7-20
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@ 6!!!9
TABLE 7-9, PRELIMINARY EVALUATION OF HALON REPLACEMENTS COMPARED TO THE TWO PRINCIPAL HALON$
(Refs. 14,42,43,44,45,46,47, WI(I48)
OZONE CONCENTRATION CARDIAC CUP BURNER
“1’RADJ3
NAM13* FORMULA DtZiW3TION L13THAL POR 50% SENSITIVITY (WWTANE),
POTENTIAL OF 13XPOSED THRESHOLD (CST), % vii %
(ODP),
dimerrsionlcss
Carbon Dioxide co~
> 80(47)
II I
1 I
I 28 I
I s, P, Oc
,
Ii
0,80(43)
HaIon 1301 CF3Br 10.0-14. 1(47) 5 7.5 3 5.O-5.2** IF, OC-Bf2sclinc !
HoIon 121I CF2ClBr 2.4-3 .0{41) 8.5- 10.0(4*) nn na 3.8
FE- 13W CHF3 0(46) 65 50 >50 12
1 1 1

FE-25- C&H (3(4s) >70 7.5 7.5 8.1 1 I

PE-232W CP3CHC11 0.02 9,0(43 P 0.02(44)

FE-24 1’” I CF3CHCIF o,02(4~) 23-29 I 2.5 I 2.5 I 6,4
[TM 1009 I CHF,Br 0.19-1.1(47) 10,8 2 3.7 3.9-4.4 (2) s, Uc
FM 2009 CPJCHFCPl ()(41) >80 7 9 5.8 7.9 P, Uc 0.3-0.6(47)
y 1 , I , 1

M PPC 410- c~P,lJ Otda) >80 40 >40 5.5 6.2 F, OC, UC insignilicant[48)
,I ,I ,I I ,
NAF Sill”’ (1) (j~4(43) 32(W 8.6 o,32(dJ) 8.6 F, Oc, Uc ()$1(43)
I I I I
Notes: (1) Mixtureof Ct~CIF1,82%;CI$CIICIP, 9.5%; CP3CIICIZ,4.75%;andproprietarytryrocarbon, 3.75%
(2)Rule of Ttnrrnb: Cup Burner Value + 20%
●Nlcnlion of propriewy subslrmccs does nol consliwc Government cndorsemcm.
** me ctlrren[ Army d~ign vnhre for tiaton 1301 is 7% COrrCc.r2hXitiOrL
OC = recomtnended for use in occupied compartments
P = in[endcd for usc in portable extinguishers
UC = recommended for use in unoccupied comparimcnts
S = streaming, i.e., a spray or stream
P = flooding, i.e., a mist or vapor
na = not available
NOEL = no observable effect level
LOEL = lowestobservable eikct level
Referencefor dala is Ref. 14 unless otherwise indicated by superscript reference number in prmcnlhcsw

I
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,,
,~J :,,

,>

TABLE 7-10. PROPERTIES OF HALON REPLACEMENTS (Refs. 8,9,14,42,43,45,46,47, 48, and 19)
LATENT SPECIFIC
SUBSTANCE FORMULA MOLECULAR DENSITY BOILING HEAT OF VAPOR HEAT AT FREEZING ABSOLUTE
WEIGHT, AT 25°C, POINT, VAPORIZATION, PRESSURE, 25°C AND POINT, VISCOSITY AT
g/mol kglL or g/mL ‘c J/g MPa 1 atm, Jl(g°C) “c 25°C, mPa+
Halon 1301 CFJBr 148.95(43)’ 1,538(W) -57.75(43) 118.8(43) 1.62 at 25”C(45) g 0.469(9) –16$(% o. 159(43)
@0.870(43)
Halon 1211 164.5(42)’ 1’.7973(42) 2(42) 123.4(42) 0.276 at 25°C g 0.450(8) –160
. CF2ClJ3r
,“
FE- 13TM CHF3 70.01 0.6699(4! –82. 1 239.6 4.59 at 25 °C(ib) g 0.737 -155.2 0.083
Q1.549
FE-25TM “ CZF5H 120.02 1.2494(45) -48.5 164.7 1.31 at 25 °C(4s) g 0.800 –102.8 0.145
@1.260
FE-232TM CF,CHC12 ., 152.9(42). 1:4597(4*) 27+9(W 96.00(42) 0.0896 at d0.667(8)
250@Z)

FE-24 ITM CF3CHCIF 136.5 “ -11.0 167.9 0.38 at 25*C go.741 -198.9 0.314
!?1.130
FM 100@ CHFzBr 130.92 1,80(4$9 -15.5 171.9 0.490 at 27 °C(41) g 0,455 –145.0 0.280
y 00.455
N
N FM 200@ CF3CHFCF3 170.03 1.427 at -15.2 133.0 0.405 at210C(47) g 0.726 –131.1 0.183
200CW) 01.102
PFC 4 10TM C4F,0 238.03 P 1.517(48) –2 ,“ 96.3 0.2896 at 25°C g 0.804 –128.2 ‘0.0642(48)
g o.oo9935@) Q1.047 @0.324
NAF SIIITM See Table 7-9 92.9 1.20(0 –38.3 225.6 0,95 at 25°C g 0.67 <–107.2 (),21 (43)
t 1.256
PFC-614 CbF14 338(@ 1,68(W 56(W 884(W 0.31 at 25”C(48) 0.00069

*Reference for data is Ref. 14 unless otherwise indicated by superscript reference number in parentheses.
g = gas
! = liquid

*
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MIL-HDBK-684
7-2.23 Other turned off. US Navy (USN) ~rsonnel have recommended
,:11
,!j i Hydrated alkali metal salts of boron and silicon oxides the use of a freshwate~ mist to extinguish even elecrncal
o“’:”~ including sodium tnetaborates, terraborates, metasilicates, tires (Ref. 51). The shock hazard associated with using
““:’and homologies thereof are effective extinguishing agents -. - water to extinguish fires involving ekxrical equipment has
whose mechanisms include cooling by latent heat of vapor- beerI shown to be minor as long as the electrical voltage is
ization, dehydration, intumescence, and formation of an low, the water is not highly elecrncally conductive, anrUor
irtsolative char or foam. the water is not a continuous medium (Ref. 52).
An example follows of a hydrated salt that could be used Water functions as a fire extinguishant ptimarily -as a
to cool a fire by liberating moisture. Assume 1 kg of magne- coolant. As it impinges on hot surfaces or mixes with hot
sium sulfate heptahydrate, MgS04”7H20, (’Epsom salts) was gases or flames, the resulting steam dilutes the flame gases,
dispensed into a large volume in which there was a fire reduces flame temperatures, and blankets * fuel. Thus
maintaining a tempamtre of 177”C. . ‘he Epsom salts oxygen is diluted, and flame temperatures are thereby
- would heat fkom 21 ‘C to 150°C absorbing 195 kJ of heat; reduced to the point of extinction (Refs. 30 and 53). One kg
At 150”C theEpsom salts would lose 439 g of H20 absorb of water at 21°C sprayed into. a large compartment contain-
ing 1.361 MJ of hea~ The 561 g of magnesium sulfate, ing a fire maintaining a temperature of 177°C would do the
MgS04, and the water vapor would heat to 177°C absorbing following:
37 kJ -of heat. Then a gaseous coolant could be injected that 1. Heat from ambient to the boiling point by absorbing
would absorb a total of 1.593 MJ of heat and release 439 g 0.333 MJ
of H20 diluent. The MgS04 would readily absorb water 2. Boil by using 2.2S7 MJ
when coded and would eventually return to Epsom salts 3. Heat the vapor from the boiling point to 177°C by
(Ref. 31). using O.144 MJ.
The boron salts are active free-radical terminating agents, The sum of these heats is 2.734 MJ, and the water would
a property shared to a lesser degree by the silicate anions. provide 1000 g of water vapor diluenL “ : –
Aqueous solutions of these agents offer enhanced extin- For deep-seated Cellu]osic fires, liquid water wo~~~ 5
guishing ability by both interruption of free-mdical chain to 13,500 times as effective in cooling hot solids, that is in
mctions and energy absorption by the solutions as they quenching a deep-seated celluosic fire, than would gaseous
release their associated water and proceed to calcine and coolants used as extinguishants. On the othenhand several
J$$ intumesce.Thus energy is absorbedas the solute undergoes exti.nguishanrs described- herein could eliminate flames
o more effectively than water.
calcining transformation from solute to hydrated crystalline
solids to expanding viscoelastic, amorphous masses and
finally to rigid cellular foams. The only practical use made 7-2.3.1.1 Forms of Fire Extixtguishant Water
of hate solutions to date has been in airdrops on forest and ‘Ilte form in which liquid water is used to extinguish a fire
brush iires (Ref. 50)- is important in the planning of usage and disrnbuaon sys-
tems. For example, water can be spumd onto a fire in the
7-2.3 COQLENG AGENTS fotm of a JeL This method would deliver a high volume of
Any vaporizing liquid extinguishing agent can provide . water quickly, which would be excellent-to extinguish a
cooling, but many such agents also exhibit chemical inter- . deep-seated Class A &e, such as clothing or a seat cushion,
vention properdes and prevent oxygen access to the fuel. that requires primarily cooling to extinguish A water jet can
Consequently, such agents (other than water) are assigned to travel a long distance quickly: 9 m (30 ft) using a handheld
one of those classes rather than rhe cooling agent class. 63.5-mm (25-in.) hose. A water spray, in the form of many
Likewise, powders such as al.kfdi halides or bicarbonates droplets, can be directed onto a burning pool of hydrocar-
that fimction more as chemical intervention or oxygen-ex- bon fuel (Class B fire) without spreading the fhel pool by
. eluding agents than as cooling agenrs are not included. splashing and can be delivered from approximately 43 m
(14 ft) using a handheld 63.5-mm (2.5-in.) hose nozzle. A
7-2.3.1 Water water m.isL which consists of very small droplets (Sauter
Water represents the most common and most available mean diameters of10 to 200 pm**) of water, would have a
fire-extinguishing agerm Its properties are well suited for very short delivery range, i.e., 305 to 610 mm (1 to 2 ft),
fire-extinguishing applications. It is chemically stable and
nonflammable. It is the only completely nontoxic extin-
*As opposed to seawater, which is notmally used on US Navy ships
guishing agent known, and it doesnot produce toxic com- to fight tires
bustion products. Moreover, it possesses an unusually high *%ese sizes were established using a Malvern particle size ana-
latent heat of vaporization relative to most other potential lyzer. ‘Iltis insautnem uses laser pbotocorrelation spcaroscopy to
extinguishing agents, and this propmy enhances its cooling chmcteriu particle size and distribution. For liquid particles the
effiits. Water should not be used on 6res near high-voltage size is chamcmx. ed as the Satner mean diameter D32 in pi. lle
theory by WhiChtttk ch~Ion is accomplished is described
(>10 kV) equipment until the electrical power has been
in Ref. 54.

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MIL-HDBK-684
and” wouldprobably require some meahs other than residual friction losses in hoses and.,pipes, difficulty forming water
momentum to travel from the nozzle., Final] y, water vapor, fogs, and growth of algae.
, steam, can be used as a blanketing agent, but-steam can be One practical use of water-soluble thickeners has been in e
. ‘pressurized and jetted a greater distance than a mist. airdrops on forest and brush fires (Ref. 50). They are also
For liquid hydrocarbon fuel fires, a smearn of water can- used in a zero gravity environment (spacecraft) (Ref. 63)
not be applied directly to the fire because it would scatter and in combat vehicles (subpar. 7-3.2.4).
the burning fuel. Hence water must be applied to liquid Water treated with friction-reducing additives, in contrast
hydrocarbon fuel fires as a foam, spray, or fog. In special with thickened water, has been tested by domestic firefight-
cases a relatively strong; coarse water ‘spray can be applied ers. “It has been o~semed that fire hoses deliver significantly
to shallow pools of viscous hydrocarbon fuels-to achieve more water and achieve better nozzle pressures when using
emulsification of water in the fuel. The formation of such a such treated water, “rapid water” (Refs. 11 and 26).
water-in-fuel emulsion enhances cooling of the fuel (Ref.
19). The use of water in the form of foam is discussed in .. 7-2.3.1.2 Freeze Point Suppressants
subpax. 7-2.1.6.. ., When exposure of water-base extinguishants to freezing
Ideally, a spray should.penetrate to the seat of the fire and ~‘ temperatures is anticipated, freezing point depressan@mti-
extinguish it at its source. The effectivesiess” of a water freeze) should be included in the water (Ref. 10). The most
spray, however, increases with increasing droplet surface common such additive used in fire fighting is calcium chlo-
area, i.e., decreasing droplet size, but @e ~enetration of the - ride (CaC12) plus a corrosion inhibitor. Sodium chloride
spray into the fire increases wi~ droplet size (Ref. 55). (NaCl) cannot be used because it is not as effective and is
Accordingly, there is an optimum water droplet size for extremely corrosive. Another freeze point suppressant that
maximum fire-extinguishing effectiveness for aqy” fire con- could be used is potassium acetate (KC2H302). TO assure
fi~ation. Experimental and mathematical studies have adequate storage stability, water used in military fue-extin-
been conducted to optimize the mode ..of application of. Wishing apphcations must also contain an.antifungd.addi-
water sprays, the rates and duration of application, and the tive.
properties of the spray being applied (Refs. 56 through 60). Pure water freezes at O“C, well within the temperature
It has been observed in an incident of a bqing liquid range in which combat vehicles must operate. Therefore,
..,’,. lie] flowing as a film, i;e., film-wise, on a solid surface that a freeze point suppressant must be available for use in
the size distribution of droplets in a water spray is not winter in temperate regions and in arctic regions. Combat
*
important. With deep pools of the same fuel, however, the vehicles are expected to operate in temperatures down to
extinguishing effectiveness of water sprays increases with –32°C (–25°F) and down to –54°C (-65”F) with winter-
droplet size (Ref. 60). It has also been observed that the ization kits installed; these wintenzation kits are not sup-
required rate of application of a water spray to liquid fuel posed to include internal heaters.
,.. flowing film-wise on a solid surface increases with increas- The current freeze point suppressant used by the US
ing bum time; hence the surfaces. of solids. are hotter. Also, .. Army is ethylene glycol (C2H60J, per MILA-46L53.(Ref.
,:
when the water’ spray is directed into the suhace of the 64). The lowest freeze point indicated in Ref. 64 for mix-
burning fuel, the extinguishment is “more effective than tures of C2H602 and water is -5 1°C (-60”F) at 90% by vol-
when.lhe spray is used to forma shroud around the fire (Ref. ume. Ethylene glycol is toxic; a lethal dose for humans is
59). about 100 mL. An antifreeze agent recommended by the
The fire-exi.anguishing effectiveness of” water sprays National Fire Protection Association when connecting a fire
improves with inclusion of selected additives. The use of water reservoir to a drinking water supply system is propy-
dissolved salts of alkali metals is discussed i.n subpar. lene glycol (C~H80J (Refs. 10 and 65). Propylene glycol is
7-2.2.2. The viscosity of the water increases with’inclusion nontoxic and is used as an antifreeze in many household and
.,.-” of water-soluble thickeners, e.g., salts of carboxymethylcel, recreational applications. The lowest freeze point indicated
‘,
lulose or alginates (Refs. 50,56, and 57). The advantage of in Ref. 10 for propylene glycol is –5 l°C (-60°F) at 40% by
thickened. water is that such formulations ire much slower volume. Calcium chloride was selected for use in the explo-
to run off the burning surfaces; thus the. cooling and sive-activated linear fire extinguisher discussed in subpar.
fuel-blanketing efficacy of water is enhanced: Recom- 7-5.2.6. The lowest freeze point indicated in Ref. 10 is
mended viscosity increases range from 5- to 200-fold 45°C (-49”F) for a solution of 0.591 kg of CaC12 per liter
(Refs. 57 and 61). For a water-additive combination the of water. The US Navy has developed a lithium chloride
viscosity can be increased by increasing the moleculm solution for fire extinguishers exposed to low temperatures,
weight of the additive. Also additives that cause water to i.e., –54°C (-65°F) (Ref. 10). ‘I%e antifreeze additive used
‘,- gel have been studied (Ref. 57). It has been observed that - in. the portable water extinguisher installed in Trans World
the time to. extinguishment decreases as the viscosity Airlines (TWA) aircraft (Ref. 66) is potassium acetate
increases; hence water consumption is reduced (Ref. 62). (KC2HSOJ. This freeze point suppressant is in the propri- e
Disadvantages of water thickeners include increases in etary material designated GS-4m, which is nominally 50%

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MIL-HDBK-684
by weight-potassium acetate plus corrosion inhibitors, and tate will heat to 292°C (558°@..at which temperature it will
e remainder is water. The lowest iieeze point indicated for combine with atmospheric oxygen, and one of the interme-
s mixture is -60QC (-76’%F), and its range is shown on diate products (KHC03) will decompose and produce end
Fig. 7-3. Information on these freeze point suppressants is products, as shown in this chemical reaction:
given in Table 7-11, and a sample calculation of cooling
capability using potassium acetate as a hem point suppres- 2K~H30z + 401 + g s KZC03 + 3HZ0 + 3COP
sant follows. These equations were taken from Ref. 67 an~ Potassium carbonate (K2CO~ will continue to heat to
where necessary, converted to S1 dimensions. 891°C at which temperature it will calcine:
For the tizing point of a potasium acetme and water
solution FPm, KZC03 + q - K20 + C02

FPm = (-0.167 CUM)+ (-0.0206 CWK?), ‘C If moisture is presen~ the potassium monoxide (KZO)
(7-lo) could combine with the moisture in this process:
where
cone = concentration of potassium acetate, % W KZO + H20 + q e 2KOH.

The relative effectiveness of candidate cooling-type

For the specific heat of a potassium acetate and water SOIU-~ . extinguishants can be estimated. by establishing-the heat
tion ~pA, removed, the atmospheric oxygen consume~ and the dilu-
ent gases-carbon dioxide and water vapor-produced by a
cm= 4.226 + 0.0006025 T- 0.2833 COJIC,J/(g.K) given mass of water plus the fkezing point suppressant and
(7-11) by using the equations in subpar. 7-1.3. Material properties
are given in Tables 7-4 and 7-11. ‘lhe estimation must be
where broken down into steps that are established by a change of
T= ‘c.
temperature state of one of the substances involved or by chemical reac-
tions. For a potassium acetate and water solution of a mass
The process hypothesized is for the solution to heat to its of 1000 g, the steps follow:
ii! boiling poinL which is assumed to be 116°C (241”F) for a. 1. Raise the temperature of the solu;on from the
o solution near that of GS-4W. The water then boils out and initial temperature to tie boding point of the solution.
leaves potassium acetate in a solid state. The potassium ace- (Assume the initial temperature .is 21”C. and the boiling
point is 116°C.) To suppress the freezing point to -54*C
(-dS”F), a 94.5% GS4W solution is used. (The
K~H30z concentration is 47.2S% by weigh~ and water
is 52.75% by weigiw) A mean specific heat can be
obtained from Eqs. 7-1 and 7-1 l;~P = 2.9215 J/(g.K),
‘he heat needed to raise the temperature of the solution
is 278 kJ.
2. Boil off the wateq establish the mass of water vapor
produced by using the latent beat of vaporization of water
2257 J/g. ‘I%e mass of the water boiled off is 527.5 g, and
the energy required is 1.191 MJ.
3. Raise the temperature of the water vapor and potas-
sium acetate solution from its boiling point to 177°C.
Therefore, 527.5 g of water vapor and 472.5 g of K~H30z
are raised from 116°C to 177°C using 0.103 MJ of heaL
These calculations indicate that by using a solution of 1
kg of water and sufficient freeze point suppressant to obtain
a -54°C freeze poin~ a cooling capability of 1.572 MJ as
Gs4”@wmnakm.’?$ well as 528 g of water diluent are obtained Most of this
Reprinted with permksion. Copyright @ by Gyotech Deicing cooling effect is from boiing the water-the best way to
Technolo~, Fort Madisom IA. cool hot solid matti.

F- 7-3. Freezing Point of Water--GS 4m

“!~[ Solution (Ref. 67)
o

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. . . . .,
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,.

TA.~LE ‘7-II. iMTA FOR WATER AND ITS FREEZE POINT SUPPRESSANTS
LATENT COMBUSTION
MOLECULAR TRANSITION HEAT OF SPECIFIC HEAT OF ,OR
SUBSTANCE FORMULA WEIGHT, DENSI~, TEMPERATURE, FORMATION, HEAT, TRANSITION, DECOMPOSITION
g/mol ~mL ‘c J/mol J/(g”C) J/g PRODUCTS
Water HZO 18.0153(9)” c 0,913 at nmp(12) nmp 0(9) g -241.8 c 1.925 at nrnp(12) f 333.2(!0) H2, OH, 02
01.000 at 4“C(12) nbp 100(9) ! 4.186 at nbp(io) v 5010.7( ’0)
g 0.0005799 at nbp(bg) d = 4177( ’8)
Ethylene CzHb02 62,07(@ !. 1088 at 20°C(9) nmp –] 1.5(9) t -455.3(34) f 2.43(6s) at 25oc’ “ f 181 (9),170(69) H20, C02, CO
Glycol –1 2,6(@) g 1.56(68)at 25°C v 80fj@@)
nbp 197,$’38) ‘
197.2(69)
Propylene ~~H@* 76. 11(9) t?1.0361 at 20°C(?) nbp 189(’) [ 485.7(34) v 999.9(9) H*O, co*, co
Glycol
Calcium CaClz 110.99(9) c 2.15 at 25”(Y) tnmp 782(9) _795;8(t~) c 50.68 at 127°C ’34)
.,,
Chloride nbp > 1600(9)
Potassium KC*H30* 98.14(9) c 1,57 at 25”C(9) _723mO(T) : KHCO~, C02, ~
d 292(9)
Acetate H20, CO, KOH, ~
4 K02 x
u
‘b f = fusion Q= liquid c = crystalline or solid nmp = normal melting point m
Cn
d = decomposes g = gas v = vaporization nbp = normal boiling point x
h
*Superscripts in parentheses indicate the number of the reference from which the data were extracted, e.g., (9) = Ref. 9. a
a
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7-23.4.3 ..- Smfactants and Foaming Agents mol of each of. three sal~. be obtained from data in
,,:# Some of the discussion of surfactants is given in subpar. Ref. 9. The three salts are sodium chloride (NaCl), the
, ,\ principal ingredient of seawate~ calcium chloride
o -2.1.7.
- When afire involves a porous fuel, such as a fabric, the (CaCl~, a commonly used fkeeze point suppmssanq and
extinguishing effectiveness of water can be enhanced by the potassium acetate (K~H302), a freeze point suppressant
addition of trace “quantities of a water-soluble stiactant that can meet the -54°C (-65°F) requirement. The ions
(wetting agent). The normally high surface tension of water released when these salts are in solution in water at 25°C
is thereby reduced substantially and allows increased pene- and their equivalent conductance are Na+, 50.9; Cl-,
tration of the fuel mass. This “wet water” is normally used 75.5; Ca+, 120.0 K+, 74.5; and, ~H302”, 48.0. From
in fire situations in which the improved penetration allows these ionic relative conductance, one mol of each salt in
water to reach remote or shielded regions within the fuel solution is: NaCl, 126.4; &C12, 271.0; ~d K~H302,
mass andlor promotes thorough soaking to provide 122.5. A one-molar calcium chloride solution should have
improved extinguishment and cooling and thus prevent a little over twice the conductance of seawater, whereas a
reignition. one-molar potassium acetate solution should have slightly
less conductance than seawater.
7-23.1.4 Coxtduction of Electricity by Water Deposit of sufficient water in liquid form to bridge the
Previous efforts to quantify the conduction of elecrncity gap between the conductors and the vehicle body would
by water were intended to establish a safe distance from provide an electrical path, but such shorts should be handled
which firemen could project water without fear of electrocu- by devices in the electrical circuits. In general, electrical
tion (Ref. 10). Conduction in a water jet is a fimction of the power circuits that handle a high current flow are cumendy
diameter of the nozzle (which controls the diameter of the limited to 28 V dc, but in the future the voltage can be as
jet), the vohage of the electric source, whether the potential high as 270 V dc in US combat vehicles. Circuirs that have
is between tsvo conductors or from conductor to ground, the higher voltage, a maximum of 770 V in lJS combat-vehi-
distance fmm the electric source to the fireman, and the cles, have low amperages. l%us, the electrical systems in
impurities in the wamr. ‘Ihe form of the water is extremely US combat vehicles should have little rrouble if water mist
importam A jet conducts ekcuicity much more readily than were used as a fire extinguishan~ even if fkeeze point sup-
a spray. The criterion used was the distance between the pressants were used also.
lectrical source and the firefighter that was necessary to
nt 1 rnA of current to fiow. For example, witl 115 V of 7-23.1.5 Use of Bulk Water
alternating cument (at) potential to ground or a potential Bulk water is used to fight fires in US combat vehicles
between two bare conductors of 230 V ac, a distance of 0.50 when local &e deparanents are available or when crew
m (1.6 ft) is required for a 7-mm diameter nozzle, 1.00 m members pour water horn water cans. Fire departments are
(3.3 ft) for a lfhun diameter nozzle, or 2.00 m (6.6 ft) for a not usually available in combat situations, but combat orga-
3&mm diameter node through which Seine. River wm.er nizations often carry bulk water in supply wehicles.=For
was flowing, which had a specific electrical resistance of example, the First Armored Diviion took water trucks to
360 Cl mm at 21*C (Ref. 52). SWA to supplement the water tmilers normally used (Ref.
The’specific electrical resistance of water vari= from 107 70). Had emergency fire-fighting pumps, hoses, and nozzles
f2 mm for highly purified water to 2 to 2.5 fl mm for seawa- been installed on those trucks, the FAISVs described in
ter. Potable water varies from 71 to 540 L? mm. The current subpar. 7-1.2 that burned might have been saved. Installa-
i that can flow through such a water jet path is tion of emergency fire-fighting pumps, hoses, and nozzles
on bulk water carriers is recommended.

lrd2v A 7-23.1.6 Use of Water Mist

i= (7-12)
7. ~1’ in ourtechnology-related society use of old-fashioned or
where simple items is highly suspea This proposition is as true
d = diameter of nozzle orifice, mm for fire extinguishers as it is for weapons or communica-
V= voltage between conductor and earth, V tions devices. Yet signal flags are part of the on-vehicle
p = specific resistance of water, Q mm, material (OVM), and bayonets are being issued to riflemen.
1 = distance between nozzle and conductor, mm. Both the knife and the flag have a use on the modern bat-
tlefiel~ and the Fort Hood crewmen (Ref. 71) had to pour
When the water is in spray form, the current conducted water tim a five-gallon can to extinguish a fire in the air fil-
by the spray is of the same order of magnitude as the leak- ter of an Ml MBT, as described in subpar. 4-2.3.2. Water
,~,i age current baause of ionization of the air surrounding the may be old-fashioned but it is good for extinguishing hre.s.
“~’1$ conductor (Ref. 52). Also new ways can be found to use water. The objections to
0
The relative electrical conductance of water with one water are:

. ,.-
I-zl
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MIL-liDBK-684
1. Mreezes. United States (Ref. 76) to demonstrate and evaluate this
2. It conducts electricity. ., concept. In both efforts the washing of pollutants, such as
3. It cannot extinguish a liquid pool fuel ~e or a fire- hydrogen chloride (HC1), carbon monoxide (CO), particu- *
“bill. lates (primarily carbon), hydrogen cyanide (HCN), nitrogen
4. It daniages equipment. dioxide (NOz),. ahd sulfu dioxide (SOZ), out of the air has
5: It has to be cleaned up. been documented, as shown on Fig. 7-4 for carbon monox-
How valid are these objections? In 1977 ~ielding, ‘Wll- ‘ ide and Fig. 7-5 for HC1. The capability of water mist to
liams, and Carhart (Ref. 72) suggested the use of water in remove contaminants from air is no surprise because “wet
mist form “to extinguish fires in” US nuclear submarines. scrubbers” have -long been used to remove particulate and
They assumed that the electricity could be turrsed off in the S02 from smokestack smoke. Babcock and Wdcox (Ref.
fire area, and they calculated that water could cool fire tem- 78) state that wet scrubbers remove up to 995% of particu-
peratures of 1725°C to 1075”C, at which the flames wotdd lates and 859o of S02. What is surprising is that use of a
extinguish. They suggested that freshwater, as opposed to water mist also reduces the amount of C02, as shown on
seawater, would not conduct electrici~’ and would cause Fig. 7-6, thatinfiltrates from.a fire just outside into the cabin
less damage to equipment, particularly in the fo~ of a mist. ~ (Ref. 77). Researchershave established that soluble gases,
They pointed oht that the water mist was not toxic and e.g., HC1 and SOZ, are readily absorbed by water sprays,
would in fact remove smoke and toxic fire products from’ that the concentration of gases having intermediate absorp-
the i.ir. (Nuclear submarines do not have a freeze problem.) - tion rates, e.g.,’ HCN and N02, can be reduced by water
They suggested that the submarine be made less susceptible ; sprays of the proper droplet size and volume, and that gases
to fire through ”identification of alr flammable materials’ and with low absorption rates, e.g., CO and C02, are essentially
their replacement as completely as possible wi~ “firesafe” -. unaffected by water sprays.
materials. They also suggested that a water mist fire-extin- Research efforts in the UK established that the water mist
guishing system be developed for use in nuc~ear subma-. - droplet size is extremely important (Ref. 75);.If .tiedroplets
rines: The US Navy started a program to develop this. are too large (2200 pm), they do not absorb or adsorb the
system. contaminants as effectively. If the droplets are too small (<5
h. this Navy program water mist systems designed to pm), they cannot be filtered’ out by the normal human
blanket a compartment by spraying from the ceiling extin- - breathing apparatus, i.e., probably by the -mucus that is
guished pan fires of hexane, diesel fuel, and lubricating oil secreted by the olfactory cells. These smaller droplets can
m
(Ref. 73) as well as Class A fires of a stack of w’ued paper carry dissolved or trapped pollutants into the lungs. There-
milk cartons and other similarly difficult to extinguish Class fore, mist nozzles must be designed to produce droplets
A fires (Ref. 74). between these two sizes. Ball et al (Ref. 79) showed that
A similar water mist system was suggested for. commer-” nozzle design and pressure affect droplet size the most, as
cial aircraft cabins to provide the passengers time to escape shown in Fig. 7-7, and that the flow rate of the water does
in- the event of fire following a crash. Programs are being’ not necessarily affect droplet -size. In addition, they experim-
‘pursued in both the United Kingdom (UK) (Ref. 75) and the - ented with superheating and gas pressurizing to control

0.3,

0.25

g O.al
~.
E
g
0 0.15
z
E
e
G 0,10

-
O.&s
.,
0 20 mwJlzuls91e32io 200 270.. w)
Time,s
,,
I?@me Difference h (h-bon
7-4. Monoxide Figure 7-5. Difference in Hydrogen Chloride
Buildup Dtie to Water NIist Scr@birig (Ref. @
Buildup Ihe to Water Mist Scrubbing (Ref.
n) 77)
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Row, Umin
NoWaterSpra} A 1.0
0 9.5
v 14.9
n 53.9

I
Osofamlals I$aaoxoaoml
Tm, S
. —.
Figure 7-6. Difference in Carbon Dioxide
Buildup Due to Water Mist Scrubbing (Ref.
77)
water droplet size. Superheating raises the temperature of
the stored water prior to its flowing through the nozzle, and
its effect upon droplet size is shown in Table 7-12. Although ●

it effectively reduces water droplet size, superheating also o 0.2 0.4 0.6 0.8 1.0
reduces the capabdity of the water to absorb heat- lbus
superheating is appropriate where quick blanketing of a
P~ssure, MPa ““
space is desired but not where a tire is to be cooled in order Figure 7-7. Effect of Water Pressure on Drop-
to be extinguished. Pressurizing droplets by absorbed gas let Size for Various Flow Rates (Ref. 75)
was also evaluated Carbon dioxide dissolved in the water
and stored at room temperature, 15°C (59°F) in this case, was a fill water spray within the cabin. There was no
and at a pressure sufficient to keep the carbon dioxide in attempt to extinguish the fire-the intent was to lower the
solution did not greatly affect droplet size, as shown in cabin temperature to enable people to escape horn the fire.
Table 7-13. More evaluation of water mist fotmation is nec- There were 324 nozzles mounted along the cabin. .
essaly. Ball, Smit.lL and Spring (Ref. 75) and Smith (Ref. 79)
How efkctively water mist reduces the air temperature in demonstrated the capability of three different water spray
an aircmft cabin subjected to the effhents. from an external nozzles that produce water. mists d three different droplet
JP-4 fire that is 18.3 m (60 ft) from the thermocouples was sizes to reduce the temperature rise, as measured by twen-
demonstrated by Marker (Ref.-77). IQote on Fig. 7-8 that the . . ty-eight .thermocottples, within a test chamber in which
air temperature was measured at a location 2.1 m (7 ft) . there was a 457-by 457-mm (18-by 18-in.) Avtur (Jet A-1)
above the deck and rose to approximately 165°C in 300s in fire. The tests were compared by summing the temperature
a test in which there was no water spray in the cabin but increases for the 28 thermocouples from ambient terttpera-
rose to only 58°C horn 38°C in 300s in a test in which there ture To to a plateau temperamre TP.The summed excesses of

TABLE 7-12 EFFECT OF SUPERHEATING ON WA~R DROPLET SIZE (Ref. 75) --

..—.
DROPLET SIZE
RESERVOIR STORAGE Dz,
TEMPERATURE PRJ3ssuRE Volume ‘%0
“c (“F) - MPa (psig) <loptn IO@200 pm
-.
15 (50) 2.(W (2!30)” 1.5 52
150 (302) 0.50 (72.5) 46*26 3228
180 (356) 1.00 (145) 31*29 29A 10
*pressurized with GN2
,::lj,
o
,,,,p
Notes Equiprnem used was a 5-L suppressor with a 7%un outlet valve.
Droplet size anatyzer was 2 m from the outlet vatve.

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MIL-HDBK-684

TABLE 7-13. EFFECT OF DISSOLVED

CARBON DIOXIDE ON WA~R D~OPLET
SIZE (Ref. 75) “
Y CoarseFullConeSpray 9

AMOUNT OF RESERVOIR
CARBON DIOXIDE STORAGE DROPLETSIZl
IN THE WATER, PRESSURE, D32, pm b
df- MPa (psig)
0 5.49 (791) 98 k 11
200 5.49 (791) 89 ~ 10

0 8.00 (1160) 76* 14

200 8.00 (1160) 73&5 \
A
300 8.00 (1160) 81 f 10
E 700 Fine Full Cone Spray
Notes: bessurized with nitrogen w I DQ=60pm
Equipment used was a 6-L suppressor with a 38-mm outlet %’ m“
valve. z“ *.
Droplet size analyzer was 1 m from the outlet valve. 1-

NoWaterSpray
600 ~
153. o 20 40 60
Flow. Umin
Figure 7-9. Effect of Water Flow Rate on Heat
“. ‘ Absorption (Ref. 75)
“ .100.-
g’ other researchers. Papavergos (Ref. 80) modeled a fine
~
a. water spray system to replace a Halon 1301 system used to
~ FullSpray extinguish well head (gas flare) fires as well as pool fires *
S9.
and shuttle (Channel Tunnel) fires. Several practical fire
suppression situations were examined, and fixed water
spray systems were designed rmd verified experimentally in
0 a sc~ed test fixture. Papavergos concluded (1) that water
02060901201501s0 210 240 270 30
Trile,’s sprays have the ability to extinguish liquid fuel fires,.(2) that
this extinguishment is accompanied by enhancement of the
Figure 7-8. Tempertit&e Increase With axn~ environment through- smoke scrubbing, effective cooling,
~~
Without Water Mist (Ref. 77) and absorption of water-soluble acid gases, (3) that the
temperatures above ambient are. referred to as the total quantities of water used were significantly less than those
excess temperature function E(TP – To). The total excess used by a conventional water deluge (Thus the concerns of
temperature function was approximately 1300 deg C with- water darnage were also reduced.) and an order of magni-
out any water spray. Note on Fig. 7-9 that a full cone spray tude less than the quantity a similar Halon system would
of coarse droplets (D32-200 pm) caused the total chamber use, ,and (4) that the fine water spray system offers substan-
. :excess temperature function to be approximately 970 deg -C tial cooling of the surrounding solid materials, whereas
at a water flow rate of approximately 31 L/rein and approxi- HaIon 1301 does not.
mately. 890 deg C at a water flow rate of “approximately 47 While. reevaluating the objections to a water fire-exting-
L/rnin: Similarly, with a full cone spray of fine droplets (D3Z uishing system presented at the beginning of this subpara-
= 60 pm), the total chamber excess ‘temperature functiori graph, the reader will find the following:
,. was approximately 725 deg C at a water flow ~ate of 4 L/ 1. Water will tleeze, but just how cold will the intenor
mirs or approximately 665 deg C at a water flow rate of of a combat vehicle be allowed to become? Antifreeze can
,, approximately 7 Mnin. The water mist in this program was be used in the water, as described in subpar. 7-2.3.1.2.
designed to reduce the chamber temperature, not to extin- 2. Freshwater is not an effective conductor of
~fiish the fire. These efforts were for a system that would electricity. A high-amperage electric current cannot fiow
maintain a habitable condition within an aircraft cabin until from its normal circuit without quickly destroying the
passengers could evacuate. shorted circuit; therefore, such circuits are equipped with e
A different use of a fine water spray was developed by circuit breakers. A high-voltage electric circuit has to be

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MIL-I-IDBK-684
z contained to--prevent acing through -normal atmosphtic ever, their pyrolysis pr@ug#.~e potentially toxic. It was
,[~,~, COnUdm31KS; this containment is already done in the concluded that the use of fluorocarbons as extinguishants
electronic components of combat vehicles. Combat would not be feasible (Ref. 61), but with the pending elimi-
---”- vehicles-use a low vohage, 28 V dc or 77 V dc, for circuits nation of halons, these compounds are being reevaluated.
tAat use high amperage. Even if a freezing point PFC 410m { for example, has Environmental Protection
suppressant were used that could lower the electrical resis- Agency (EPA) approval (Refs. 14 and 17). Due to the long
tance of water almost to that of seawater, a water mist atmospheric lifetimes of PFCs, however, their use is limited
would not pass enough current to endanger a crewman to applications in which no other solution exists.
spraying a fire. Ballistic damage has a high probability of
rendering electric components inoperable, and most electric 7-23.4 Other
subsystems must be encased in sealed enclosures anyway. The use of aqueous diammonium phosphate as an extin-
Any problems presented by the use of a water spray, which guishant has been proposed and studied Apparently, this
in many ways is no worse than a high-humidity smog, are agent produces a residue that functions as a fireproof banier
solved either by the normal packaging requirements of the (Ref. 26).
electrical components -or by improved circuit breakm, or . Monoammonium phosphate ~H2P04, referred to as
their equivalerm MAP) powder is effective on Class C as weU as Class A and
3. Water mist systems can extinguish liquid fuel fires Class B fires. his referred to as the ABC powder because it
and fireballs. , can be used on ail three types of fires (Ref. 26). If 1 kg of
4. A water mist without additives will not damage pulverized MAP at 21 “C were injected into a space contain-
equipment within a combat vehicle any more than normal ing air at 177”C, heating the MAP to 177°C would take 193
environmental moisttxe would. kJ of hem If MAP were heated to 190”C, it would decom-
5. Water from a mist extinguisher would not require pose following the process 4NI&.H2P04 + QC-+ 4NH3 +
any more cleaning up than rain or snow inside a combat 6HZ0 + P4010 and would emit 148 g of ammonia (NH3)and
vehicle would. Water, in liquid form, would collect in the - 617 g of phosphorous pentoxide (P401& The ammonia cart
bilge of the vehicIe and could be drained overboard. explode in air, is corrosive, and is toxic to breathe, and
In addition, when effective passive fire suppression tech- P4010 is an initaat to skin, mucous membranes, and eyes
niques are used in a combat vehicle, there shouId be no fires (Ref. 31).
,j~l ‘“’that water, in mist or spray form, cannot extinguish.
0 7-2.4 EXTINGUISHANTS FOR COMBUSTI-
7-2.3.2 A.lunim Powder BLE METALS FIRES
Powdered ahninum oxide (A1203), ahrnin~ is the extin- Combustible metals that may be used in combat vehicles
guishant of choice for use in military aircraft. Alumina was include magnesi~ lithium, aluminunL titanium, and ura-
selected because it is chemically inert, whemns potassium nium. There are other metals that can bum, such as sodium
“b- icarbonate is slightly acidic and monoammonium phos- and potassium, but they are not normally used in combat
phate is slightly basic. Alumina has a specific gravity of vehicles. Aluminum, titanium, and uranium usually will not
3.97, a harthess of 9 mobs, and other properties that are burn in solid form in air without added heat unless they are
listed hi Table 74. The heat-absorbing capability of alumina powder. Magnesium and predominantly magnesium alloys
“- over the temperature range that concerns armored vehicle can generate sufficient heat to sustain combustion in air.
designers is due to its solid-state energy-absorbing ability These have been considered for road wheels for combat
when used as a iine dust. By using Eq. 7-1 and the values in vehicles. Lithium, which can generate sufficient heat to sus-
Table 7-4 for ~ at 25°C and 127°C, the heat-absorbing tain combustion, may be used in some of the newer electric
capability of 1 kg of aluminum oxide, when heated from batteries for combat vehicle systems. Fire extinguishants for
-. 21°C to 177W, is detemtined to be 134 kJ. No diluents.. both magnesium and lithium have special requirements.
would be released, but there would be a problem of cleaning Most currently available fire extin@hants recommended
up the alumina aftmvard. for extinguishing magnesium fires will not adhere to a verd-
cal surface. The effectiveness of Navy 125S* (Ref. 81) to
7-233 Perfiuorinated Carbon Compounds extirt~h a lithium fire has been verified in tests Navy
Volatile pa-fluorinated compounds (fluorocarbons) are 12.5S has also been checked to extinguish fires of magne-
assignedto the cooling agent class becausetheir dominant sium, sodium, potassi~ titani~ and aluminum and is
extinguishingmechanism appears to be reducing flame tem- apparently equally effective in extinguishing fires of these
peratures to the point of flame extinction via increased heat materials. Navy 125S* is a copper powder that melts when
capacity effects. The volatile fluorocarbons appear to be exposed to the metal fire and forms a noncombustible alloy
,!:,1!~~,physiologically
, inert and when mixed with oxygen will sup with the melted combustible metal. This alloy covers the
o‘:~if port lif% i.e., provide habitable atmospheres but will not surface of the base metal and extinguishes the fire. This pro-
support combustion (Ref. 61). As is true of the halons, how- cess does not produce noxious products.

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MIL-HDBK-684
7-3 EXTINGUISHERS -’ Engine
The prime requirement for a fire-extinguishing or sup-
pression system is that it effectively extinguish and/or sup-
press the-fires that can occur within a combat vehicle. .-
Active and passive fire-extinguishing systems are covered
in this handbook. Wndheld extinguishers are also dis:
cussed, Many tire extinguisher systems dispense fluids that
reduce the percentage of atmospheric oxygen present or
interrupt the combustion reaction chemically &d thus pre-
vent or at least reduce the probability of reignition by either nic
ignition sources &eady”present or ignition sources resulting
from additional ballistic impacts. ‘l%e period of time this
reignition preventative is present is a function of the type of’
extinguishant used as well as the airflow through the com- F F
,,partment.

‘7-3.1 ACTIVE SYSTEMS

The system used in the crew compartment to counter a
threat-induced mobility fuel mist or hydraulic fluid mist fire
must react and fimction in milliseconds to prevent bums to .
crew members; therefore, such a system must be automatic.
Cargo
HatchC HT- Battery Box
.Riaht Rear.
~S6kor .

‘ Fast response of an extinguisher system is not only depen-

dent on. fast detection of “tie initial fire but also on the-fast DR = Driver’s Hatch Cover ‘.. .
release of the extinguishing agent. The majority of fire-ex- TC = Troop Commandet’s HatchCover --
tinguishing systems found in combat veticles consist of .
GN = Gunner’s Hatch Cover
either an optical or thermal fire detection system, a control
electronics package, and a suppressant dis~bution system. Figure 7-10. AAV 7A1 Automatic Fire Sensing
Fig.. 7-10 shows the fire-extinguishing system used in the ad Suppression System (Ref. 82)
amphibious assault vehicle (AAV) (personnel) Model AAV
(Halon 1301) into the troop compartment. One of these bot-
7A1 (Ref. 82) as well as the locations of the fuel”storage and
tles distributes the agent through a unique discharge tube
engine. ~s particular system uses optical fire detectors to,
that is directed aft along the starboard side of the crew com-
sense the fire and a the extinguishant distribution system
pa&nent, as shown in Fig. 7-11.
consisting of three bottles that project the extinguishant
., In typical applications the distribution system consists of
agent (depen-

.,
.,, ,

,,

.,
,’

I?igure 7-11. AAV 7AI HaIon Dispersement

.,.
7-32
 Downloaded from http://www.everyspec.com

dent on system requirements) and a distribution piping net- 7-3.1.1 Fast-A&g Vkk.es
; :work that applies the extinguishant at strategic locations.
,Jii’
,:},!,,
:1, Fast-acting valves such as solenoid and squib valves are
,,‘!, e effectiveness of the system is highly dependent on the used in fire-extinguishing systems. Brief descriptions of
0
.- -m-sponse.speed of the quick-release valves, which can be of each type are presented including descriptions of the ancil-
several types and designs including solenoid and squib lary equipmeng valving and piping. Operational details are
valves. In this paragraph the various active fire-extinguish- also presented. Atypical solenoid valve and bottle assembly
ing systems are introduced including single and multiple is shown on Fig. 7-12.
container systems, single+utlet systems and multiple-outlet
systems. Typical fk extinguisher component and system 7-3.1.1.1 Solenoid
coniigumtions found in current combat vehicles are pre- A solenoid valve uses an electrical coil that moves a core
sented in par. 7-5. to open the valve port(s). The solenoid-actuated valve is
most cornmonl y used in fire-extinguishing systems because
of its quick response and capability for reuse. One ~ of
solenoid valve, shown in Fig: 7-13, consists of a cy~&ical
plunger with redundant elas~omeric seals that hol~ pressure
and seals an agent storage bottle pofi The plunger is locked
in place using a mechanical latching system. To operate the
valve, the solenoid coil is activated; the coil pulls the ring
off the lock mechanism and thereby allows the plunger to be

.,..
-.

(A) Closed Position (Front Vtew)

.
,. .,....

ping

courtesy of HTIJKm“ -Tech DMsion, Pacific Scientific. Duarte.

“ (B) Open Position (Side View)

7-XL Typical Solenoid Valve and Bottle Figure 7-13. Solenoid Valve Schematic (Ref.
Assembly 82)
7-33
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MIL-HDBK-684
pushed. down by. the bottle pressure to release the extin-
~gishing agent. The particular valve shown in Figs. 7- 13“
and 7-14 has a valve response time of less than 10 ms. This
valve design also has a manual release lever to. allow rnan~.
ual backup activation by the crew if the automatic actuation
of the fire-extinguishing system should fail or vehicle power
not be available. The valve has been tested at vehicle tem-
perature extremes of –54to71 ‘C (-65 to 160°F) with little
degradation in the response times.
door
Protrac

Hou&ng
P m ~Elec~~ Release
Outlet Connector
Port.’:’
) MechanicalLever
0, Release

““’’’”’+ Q AntirecoilPlug (A) Closed Position (Front View)

d
L
~ ElectricalConnector
/

(!V
“k; Mechanical:
OverrideLever
out
Courtesy of Marotta Scientific Controls, Inc., Montville, NJ.

#?igM~e 7-14.Marotta Scientific Controls, Inc.;

(B) Open Position (Side View) _
Valve With Mechanical Override
Figure 7-15. Protractor Valve Schematic (Ref.
7-3.L%2 squiti
82)
: A squib valve uses some type of explosive squib or
charge to open the valve. Squib valves are not resettable and A second ~pe of squib valve that is used in quick-release
often are not reusable. One type ‘of squib valve “&at is used situations is the explosive-actuated deluge valve shown on
in”.vehicle fire-extinguishing systems is the protractor valve, Fig. 7-16. This valve uses a prescored rupture disk, a spe-
which is shown schematically in Fig. 7-15. This v@e has a cially designed explosive chtige fixed to the rupture disk,
.dlaphragm seal that closes off the bottle opening and is sup- and a detonator assembly. The valve is attached to the extin-
ported by a trapdoor. A small explosive charge referred to as guishing agent bottle or source and the rupture disk is used
the “protractor” is contained within the package and, when to seal the port. When it senses a fife; the electronic control
activated, physically pushes a pin to unlatch the trapdoor. sends a signal to the detonator assembly,, which actuates the
Once the trapdoor has been moved, the bottle pressure tears - squib. The explosive charge forces the rupture disk to fail
open the unsupported, prescored rupture disk or diaphragm. and thus allows the extinguishing agent to flow into the dis-
This particular design uses nonfragmenting rupture disks tribution network.
and protractor and thus prevents any fragments from dis- The Russians use a squib to drive a sharp, hollow punch
charging with the extinguisher agent. The metal-to-metal” through a diaphragm to sthrt the flow of extinguishant into a
seal provided by this valve design virtually ensures a leak- distribution manifold; the system in which this valve is used
proof system while in storage, yet valve ;esponse times are is described in subpar. 7-5.1.3.4.1.
approximately 3.1 rns. This valve design also has a manual The decision to use a single explosive-actuated valve to
rele~e. lever built into the valve to allow manual backup supply an extinguishing agent manifold or smaller, individ-
activation. ual systems, each with an individual squib valve, has to be

-.
“I-34

.,
l“.
 Downloaded from http://www.everyspec.com

relief device is a rupture diaphragm that will fail at a certain

pressure and release the entire contents of the bottle. These
disks are normally designed to be replaceable. The valves
f! Companin Flange :, I used on US Army ground vehicles use the rupture disk
approach.

7-3.1.4 Bottles
Fiie-extinguishing systems for combat vehicles use
high-pressure bottles-to more the agent. These storage lx3t-
tles have a quick-response valve to release the agent Typi-
cally, the storage bottles are Department of Transportation
(DOT) 3A or 3U1800 nonshatterable steel bottles (Ref.
84), as shown in Fig. 7-12. The number and size of bottles
CompanbnRange i used in an extinguishing system vary based on application
rates, size of the fire expecter$ the compartment volume,
vehicle weight and space limitations, and the criticality of
the area being protected, i.e., the more critical the compart-
F&e Metat Products, Division Fike Corporation, 704 South I&h men~ the higher the level of protection required.
Stretx Blue Springs. MO 64013, Teehnical Bnxhure Catalogue Use of multiple agent bottles is a valuable system surviv-
NO. 7387-5. Copyright 1992. ability factor. If the system has only a single bottle and that
bottle is disabled by a projectile hit or by a component rnal-
Figure 7-16. AlO Series Deluge Valve (Ref. 83)
fitnction such as a valve failure, the entire extinguishing
made based on a number of factorssuch as system effective- system becomes inoperative.- W~th muhiple bottles. the:sys-
ness, logistics, system survivability, and cost in dollars, tem would still provide fire protection with extinguishant
space, and weight penahies. Use of a single valve supplying ffom the remaking bottle(s). Current tire-extinguishing sys-
a manifold is the most economic approach from a smnd- tems are designed using multiple bottles of agen~ and the
point of dollar cost and weight savings. From a survivability control electronics are designed to check the continuity and
,,’w’““standpoint however, the singbvalve system is very vulner- pressure of the bottles of agent systematically. The system
0 able and in danger of not functioning. If the valve fails to may include a pressure switch to monitor the pressure of the
open due to an equipment failure or a projectile hit, a cata- agent. When the pressure in the bottle is low bec.mw a pre-
mophic fire ecndd occur. The smaller, individual systems vious- activation or a kak has left it empty, the controller
provide a higher level of sutwivability bemuse if one system selects an alternate bottle.
is lost for whatever reason, the remaining systems will still
be operational and will release the extinguishing agent 7-3.1.5 Linear Fire Extinguishers -. ~
given a signal from the controller. The US Air Force (USAF) has sponsored the devel-
opment of linear ilre extinguishers for use in aim-aft void
7-3.12. IManurd Valves spaces (Ref. 85). These extinguishers are basically a tube
Mechanically actuated valves are used-in manual fixed iil.led with an extinguishant and either a linear explosive
tire-extinguishing systems or as manual ovemides in auto- charge to ntpture the tube and disperse the exdnguishant or
matic fire-extinguishing systems. ‘he bottle and valve a small charge to pressurize the tube and force the extin-
assembly shown in Fig. 7-13 has a mechanical lever that . guishant out a series of nozzles. One extinguishant used is
allows a crewman to pull a htnyard to actuate the valve water containing calcium chloride as a freeze point
manually should the automatic system fail to operate or. suppressant however, JiquiG gas, or.powder.can .beused.
ekcxrical power not be available. ‘I%ese devices have performed successfully in tests. (See
subpar. 7-5.2.6 for more information on these devices.)
7-3.1S Other Valves A similar device was tested at Ballistic Researeh Labora-
In addition to the distribution valves (solenoi~ squib, or tory (BRL) to suppress combustion of exposed grains of
manual), there are a number of other valves and fittings that M30 solid gun propellant (Ref. 86). The tesrs performed
are incorporated into a 6re-extinguMing system. The agent were prelirninruy in mture, and water was used but without
storage bottles are nosmally fitted with a fill valve for a freeze point suppressant The extinguisher consisted of a
recharging. Many bottle designs are equipped with a pres- plastic container filled with water containing an AFFF
sure relief valve that will open and vent should the pressure agen~ 15 to 25’% by volume, with an immersed linear
in the bottle exceed a preset limit. ‘I&se types of relief explosive, Primacord@*. The water-foaming agent solution
valves will reseat and make a complete seal. Thus they was dispemed extremely quickly by the explosive charge-
maintain pressure at an acceptable level. Another type of
*Proctuctof Ensign-Bickford Company, Sknsbury, CT.

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MIL-HDBK-684
the extinguishant-travelled 1 m in. 6 ms .in one test and 2 m fluid. The munitions and mobility fuel can be rendered non-
in 34 m.s in a second test. This technique extinguishes a fire hazardous to personnel and critical equipment by relocating
of exposed propellant grains very effectively as long as the the fuel cells or magazines and by redesigning their com- 0
aqueous -solution ,is delivered quickly. Finnerty hypothe- partments andfor containers. There are several methods that
sized that delivery was so fast that the water reached the can be used to render hydraulic fluid nonhazardous.
propellant and extracted -heat directly from the grains; the
water was not vaporized by the hot products of combustion. 7-3.2.1.1 Nlunitions Stowage
The program described in Ref. 86 should not be confused The most probable source of fire and/or explosion from
with the program described in Ref. 87, in which tie extin- munitions is the-solid-propellant used to launch the -larger
guishant was dispersed by the shaped-charge jet or a t@rd projectiles by either gun or rocket motor. Somewhat less
program described in Ref. 88, in which the fire extinguish- hazardous is the high-explosive warhead, which may not
aqt “was sprayed onto the burning propellant. In neither of detonate upon projectile impact. Incendiary fillers, such as
the latter programs was the fire extinguished, ~~ough the triethylaluminum (TEA), and some chetical. munitions,
‘violence of the combustion was somewhat reduced. such as. white phosphorus smoke, are. hazadous. These
,- munitions become less hazardous when they are stowed in
7.3.2 PASSIVE SYSTEIMS magazines with blowout panels that direct the products of
Passive fire extinguisher systems do not require an elec- explosion or combustion away from critical vehicle
~c andoi mechanical controller or a human operator to compartments such as the crew compartment. This
activate them. In general, passive” systems are either threat redirection of the products of explosion has been accom-
or fire activated; These systems include design features that plished on- tie Ml series main battle tanks, as shown on
inhibit the ignition or propagation of fires and remove corn, Fig. 4-29 and described in subpar. 4-6.2.2.2. The bulk of
bustibles or ignition sources from critical or susceptible. ~~ the majn gun ammunition in these MBTs is carried in a
regions by relocation or compartmentalization. ~ . “bustle magazine that is separated from the crew
Threat-activated passive systems include powdered fire compartment by explosion-resistant doors that are normally
extinguishant layers, double-walled fuel cells, r@d water-gel closed. This bustle compartment has blow-away panels that
subsystems. In World War II the “wet Shermans” had dou- ~~
vent the products of explosion of the munitions outward to
ble-walled ammunition racks ‘&at contained a mixture of the atmosphere. A small number of main gun rounds are
water arid glycerine to mitigate the fires that ignited when carried in a hull compartment similarly equipped with a
the ammunition was hit (Ref. 89). These passive systems compartmentalizing door and a blow-away panel that vents a
function when the threat, either the jet of a shaped charge or into the engine compartment. There are provisions within
‘tie penetiator of, a kinetic energy projectile, perforates the the crew compartment for only three rounds in the M 1 or
passive system and causes the stored fire extinguishant to two in the M lA1. These are low in the vehicle below the
disperse. gun breech in a location that is not likely to be hit when the
“ Other types of passive fire protection systems reduce the vehicle is in hull defilade, and for the 120-mm..gunned
transfer of heat from a fire (intumescent paints or coatings), MIA1 and MIAZ crewmen are instructed to place KE
reduce the probability.. of “combustibles meeting ignition cartridges, . but not high-explosive antitank (HEA~
sources, reduce the ignitability of combustibles, and/or pro- cartridges, in this “ready rack. (See subpar. 4-6.4.1 for a
. vide ~ecollection locations for combustible fluids. Several detailed. discussion of ammunition stowage.) .,
of these systems provide compartments in which combus- Another vehicle that demonstrated this type of munitions
tion can occur without causing critical damage. . stowage design was the Advanced Survivability Test Bed
The best passive means by which to reduce the damage (ASTB) vehicle (Ref.’ 90), which is discussed in subpar.
from a fire if a hit passes through or affects munitions or 7-5.1.1.5. For this vehicle the most hazardous munitions
mobility fuel are to design andlor locate the munition maga-. . were” the - tube-launched; optically tracked, --wire-guided
zinc so that explosions therein will not. affect the vehicle or (TOW) missiles. Missiles not in the launchers were stowcxj
crew’ (described in par. 4-6), to locate and/or design the fuel - either in a magazine over the left rear sponson or in the rear
cells so that there will be no fuel fires with@ critical corn-~ of the vehicle bilge as shown on Fig. 4-32(A). The 25-mm
partments (described in par. 4-3), and to use ancill~ power cartridges were stowed in antifratricide trays, and most were
‘systems that do not include the’ hazards of the current used as an additional buffer between the TOWS and the
hydraulic fluid systems (described in par. 4-4). troop compartment, as illustrated on Fig. 4-32(B).
A possible means to reduce the explosive effects within
7-3.2.1 EIazamhms Nlaterials Stowage magazines was demonstrated by Finnerty (Ref. 86). He
Vehicle design features can provide passive protection explored the use of explosively launched fire extinguishant
horn hits by kinetic energy (KE) projectiles or shaped to reduce the combustion of exposed propellant grains. This
charges. The three most hazardous items. carried in combat could ,& adapted to prevent fire propagation among corn- a
vehicles are the munitions, mobility fuel, and hydraulic bustible cased cartridges. Another means, devised by Ball

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MIL-I+DBK-W4
(Ref. 55); is to inject water into specific cartridge cases. In the BFS!S the largest~sented area of the main fuel
Both of these techniqu~ however, require much more ceil is on the hull bottom. This could leave a large area vul-
development. A third means is to combine the antifratricide nerable to land mines projecting a jet or flyer plate upward.
-:. ‘“-.itmnnescent cylinders tested by Mescall and Maciorte (Ref. .. . In tes~ of the Landing Vehicle, Track@ Persomel (LVTP)
91) (The inturmscent cylinders must be supported by metal 5A1, fuel cells &tween the hull and the deck were suscepti-
cylinders as described by Cox (Ref. 92).), and the hinged ble to perforation by such a threat (Ref. 96). The deck plates
rear of the magazine described by Walker (Ref. 93) to above these cells should be lirmly secured to prevent per-
obtain a secure propellant or cartridge stowage area. Subpar. sonnel injury; the potential for injuty caused by loose deck
7-6.4 describes some additional innovations in ammunition plates is described in subpar. 5-2.2.3.1 (Ref. 97). - ----
stowage. Another technique used to render fuel cells less hazard-
If a flamethrower is mounted on a combat vehicle, means ous is to install a double-walled fuel cell with a fire extin-
other than pressurized bottles of gelled fuel should be used guishant within the hollow wall. This technique is described
to project the Iiquid incendiary. The flamethrower shown on in subpar 7-3.2.3 and Ref. 98.
Fig. 4-34 used a turbine-powered pump to project the liquid Another source of mobility fuel in the crew companment
incendiary. Such a flamethrower presents a much smaller is the hydmcarbon-fitel-fired troop compartment heater.tiat
hazard to the vehicle and occupants than the pressurized is currently used. This heater is described in subpar. 4-8.2.3
metal bottles used previously by the US Armed Forces as being inappropriate for use in the troop compartmen~
(described in subpar. 4-6.2.2.4). Tests of the automatic fire-extinguishing system (AFES) for
the M60A3 (Ref. 99) indicated that the cumently used troop
7-3.2.1.2 Mobility Fuel Storage compartment heater could be a hazard bwause it can rup
Mobility t%el is carried in metallic, plastic, or composite ture when-impacted by a penetrator. or hgments and thus
fuel cells. Threats that penetrate combat vehicks are introduce a combustible fluid, e.g., DF-2,. into the. crew
shaped-charge jets or massive KE penetrators and cause .- compartment. A di.ffkrent source of troop compartmentieat
severe damage; therefore, self-sealing t%el cells have been should be used or the current heater should be placed in a
ineffective and have not been used in US ground combat separate compartment.
vehicles. Further, because the effects of the threat would
probably result in cored perforations in fuel cell walls, air- 7-3.2.1.3 ~yd.HIhC Fluid SJ@fXttS . .
@ ‘‘ ti-qrp seIf-*g cells of conventional construction Hydraulic hid power systems are hazardous because
o would not prevent fuel loss in combat vehicles. they generally contain a flammable fluid in pressurized con-
In most current US combat vehicles, e.g., the M 1 and tainers or lines, i.e., fluid sprayed from a ruptured line can
MIA1 MBTs, the BFVS, most of the M113 APCs, and the produce a flammable mist. If a hydraulic ffuid container is
MO MBTs, the fuel cells are within either the crew or metallic, rupture of the container can be violent and can pro-
engine compartment. In the Ml 13A3, as shown on Fig. 4-2, duce not only a mist or spiny but ako metallic fragments,
..
and the ASTB vehicIe, the main fuel cells were mounted en. which-can be hazardous secondary projectiles. Tests ~ the
the rear in external fuel cells. AFES for the M60A3 (Ref. 99) indicate that the presence of
: l%e Ml 13A3 external fuel cells were tested using either - a hydraulic reservoir and accumulator in the crew compart-
shaped charges or 14.5-mm API projectiles (Ref. 94). A ment even when filled with fire-resistant hydraulic fluid
51-mm (2-in.) thick spacer was used between the fuel cell ML-H-461 70, can be a hazard because once again a com-
and the hull in the 14.5-mm API tests, but no spacer was bustible fluid is introduced into a sensitive compartment. b
used in the shapd-charge tests. in the two shaped-charge many of these tests the reservoirs shattered or cracked until
tests in which the jet traveled through the fuel and then reservoirs of a less crack-sensitive material were used.
entered the troop compan’men~ fuel did not flow into the There are several ways to reduce these hazards. Fhmerty
troop compartment because the shaped-charge slugs . . (Ref. 100) successfully. surrounded a fid-filled reservoir
plugged the holes in the hull, as shown in Fig. 441. with a mild steel box (to stop the fragments) and a
The ASTB external i%el cells were similar to those of the. powdered-extinguishant-filled honeycomb panel (to extin-
M113A3, Fig. 4-Z but these fuel cells were more fully guish the mist fire) to reduce the hazards. bother
tested (Ref. 95). In only three of the 27 tests described in technique is to use a truly noncombustible hydraulic flui~
Refs. 94 and 95, did the slug interfere with fuel flow from such as MIL-H-53 119, which can be quite expensive, or a
the fiel cell into the troop compartment. Thus the slug can- water-based hydraulic fluid that does not use a combustible
not be depended upon to prevent fuel flow into the vehicle freeze point suppressam
ilom an external fuel cell. In these tests a 7&mn (3-in.) Because most of these high-pressure reservoirs are made
tick gravel-fikd barrier was necessary to eliminate fuel of high-strength materials that are crack sensitive, an over-
flow into the troop compartment after shaped charge perf+ whelming threat will rupture a fluid container. A smaller
ration. (Thimer barriers, i.e. 50.8 mm (2 in.) thick, were not threa~ however, should not cause damage beyond the area
a effective.} perforated. Use of noncrack-sensitive materials or consrruc-

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MIL-HDBK-684
tions in this application is. recommended. Fluid container fuel regulator. to account fod.inferences in the engine inlet
fragmentation caused by small projectiles can be eliminated air temperature. The pneumatic actuators developed were
by use of a filament-wound container. Filament-wound fuel larger @n hydraulic actuators for the same application and o
cells haveqiroved to be crack resistant, as demonstrated in they were not spongy in operation. Also rotary pneumatic
Refs. 101 and 102. In the programs described in these two motors could be used. Pneumatic systems have not really
“references, as well as in several other test programs, fila- been developed because hydraulic systems are better known
ment-wound fuel cells containing hydrocarbon mobility and commonly used for high-power applications.
fuel or water consistently withstood hydraulic ram pressure
loads caused by fully tumbled 14.5-mm bullet impacts at 7-3.2.2 PowdereclFire Extinguishant Layer..,-
velocities of approximately 960 m/s (3149-ft/s) and suffered Powdered-fire-extinguishant-filled panels were devel-
only the entrance wound, which was approximately bullet oped for use in small naval craft by Ciba-Geigy. This panel
size; steel drums of 208 L (55 .@) capacity under the same has the trade nzupe Fire-Lamm and is referred .to as a pow-
conditions were torn wide open. In the B-1 aircraft program der pack. A version was tested for aircraft application by the
Artz (Ref. 103) fired a caliber .30 arrnor,piercing (AP) bul- “Engineering. Physics Department of the Royal Aircraft
let through a filament-wound pressure bottle: pressurized ~~~ Establishment (RAE) (Ref. ~105). As shown “in Fig. -+l*l7,
with nitrogen to 9.38 MPa (1360 psig) to establish whether Russian 23-mm armor-piercing incendiary tracer (APIT)
or not the bottle would explode; it did not. Again, the dam- projectiles were fired through the leading edge of a simu-
age to the bottle was restricted to the btdlet-size~ punctures. . lated aircraft wing made of 6 SWG L 70 light alloy (English
Another technique to reduce the hazard ~om hydraulic Number 6 Standard Wwe Gauge is 4.9 mm (0.192 in.) thick;
fluid is to use an electric motor to rotate the turret or open L 70 is an aluminum alloy), through an array of three
the troop compartment door. There is at least one incident in ~~ 5 l-~ (2-in.) outside diameter (OD) aluminum fuel pipes,
the USASC database, however, in which the.power cable and into a fuel cell containing Avtur (English equivalent of
‘for an M2” Bradley ‘was not reinstalled properly titer some Jet A-1) fuel at a temperature of, 14°C (57”F). The -APIT
vehicle maintenance, the insulation abraded, and ‘an elecrn- projectile was ac~vated by the leading edge cover so that
cal short produced a fire. Therefore, a chkge to electiic the fuel pipes and ffont face of the fuel cell would be
acttiation is a change to a different hazard. If there is a exposed to a cloud of burning incendiary particles. (It was
change, the electric system must contain circuit’ breakers, or . established that. the incendiary particles and fuel from the
the equivalen~ to preclude damage from hazardous shorts. pipes and/or cell would merge to produce a fire within 8
*
Another way to eliminate these hazards is to use pneu~ ms.) Upon impact with the simulated aircraft wing, the
~a~c actuation. In the late 1950s The M~quardt Comp&y’ APIT projectile was relatively intact, the projectile wind-
developed pneumatic control systems for some applications shield was in pieces, and span was present thus all of these
in which nuclear radiation precluded use of electric or could impact the pipes and the Fire-Lamm panel. The fuel
hydraulic power, as described in subpar. 4-4.1.:2 and ‘Ref. pipes were empty in Test 1, filled with unpressurized Avtur
104. One of ‘the subsystems described is a pneumatic tern- in Tests.2 and 3, and filled with Avtur pressurized -tcd38
perature sensor and a pneumatic actuator that controlled the kPa (20 psig) in Test 4. The impacted face of the fuel cell
metering of fuel through a regulator to maintain a constant was a self-sealing construction made to withstand 12.7-mm
temperatlwe at the inlet to a turbine engine. A second pneu- projectiles; therefore, ‘only a moderate quantity of Avtur was
matic temperature sensor and actuator interacted with the expected to spray backward into the leading edge space.

~ 51-mm(2-in,)ODFuelPipes

Fire-LamTM
Panel

Trajectoryof
,,. 23-mmAPIT “ 7
Projectile _ 1
FuelCellContainingAvtur 0.508m
Traveling (20 in.)
\
Approximately
721 m/S(2366ft/S)

, J
1

a
Figure 7-17. Instillation for Fire-LamTM Tests (Ref. 105)

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The Fm-Lam~ -panel, approximately 3.2 mm. (0.125 in.) nal fuel cell.into akrmilatedmop compartment (Ref. 112).
,tiI,
thick, was ~ed with a powdered extinguishant (’l?ef. 106). The Purple K packe~ were emplaced on the fuel-containing
o ‘~!~ ‘fhis powdered extinguishant could be potassium cryolite,
-.-: -patassium ~ic.atbonate, sodium bicarbonate, an ammonium
objects so that the jet projected the powder in the same path
as the diesel fuel. The powder packets were not the only sur-
phosphate, or potassium bicarbonate urea (Ref. 106); but it vivability enhancement feature use~ but the “fire-out”
was probably the latter, specifblly Monnex@* (Ref. 107). times were 81, 59, 65, 8, and 55 ms. In a second program
Extinguishment was obtained in 11, 104, 72, and 60 ms in (Ref. 98) that used double-walled t%el cells containing Pur-
Tests 1 through 4, respectively (Ref. 105). ple Kin the hollow walls or jacke~ much more heated diesel
In the mid- 1970s the US Army Air Mobility Research fuel was projected into the test fixture. The fire-out times for
and Development Laboratory funded a program by Bell two tests that used a 25.4-mm (1.o-in.) thickness of Purple
Helicopter to establish the capability of powder-filled panels K were 132 and 210 ms, and for one test that used a
to protect a helicopter fuel cell from the nearby detonation 12.7-mm (0.5-in-) thickness of Pt@e ~ the tire-out time
of a 23-mm HEIT projectile. Pedriani (Ref. 108) described was 102 ms. In the high frame rate motion pictures taken of
the excellent effectiveness of this device. these tests, the Purple K was seen to be projected from the
III the mid-1980s Ciba-Geigy closed its California facil- jacket in a single large clod. This clod traversed .Ihe tes$ fix-
ity, and powder packs were no longer readily available for ture and then broke up into a cloud of powder after impact-
ttiting in the United States. To enable Government Labora- ing tie far wall of the fixture. Fire extinguishment started
tories and contractors to continue testing, McNeilly (Ref. after the return of this cloud, so the fire-out time increased
109) described techniques used to produce similar pow-A considerably. If there had been objects on which the clod
dered-fire-extinguishant-filled panels. could have impacted sooner, the fire-out times probably
The capability of powdered-fire-extinguishant-filled pan- would have been significantly reduced. Again, these eight
els or plastic bags in layers to extinguish flash fires of tests are too few to provide any more than an indication of
hydraulic fluid and mobility fuel has been demonstrated. the potential of fire-extinguishant-filled packets.. -
Fuerty (Ref. 100) used either panels filled with Monnex@
or powdered potassium bicarbonate in aluminum honey- 7-3.2.3 Doub!e-Wailed Fuel CeUs
comb 3 to 25.4 mm (0.118 to 1.0 in.) thick with ahuninum Inthe late 1970s the BRL sponsorwi two.series of tests at
foil faces or the powder in plastic bags held by wire screen- the Terminal EKects Research Activi~ (TERA), located at

o# ing, The tests used these powder-filled panels on both sides

of containers of gasoline and of fire-resistant hydraulic fluid
New Mexico Technical University, Socorro, NM, of jack-
eted fuel cells to establish the feasibility of their use in the
per MIL-H-46170 (Ref. 110) or hydraulic fluid per Ml 13 APC (Refs. 113 and 114). The jackets tested were
MIL-IW5083 (Ref. 111). In the gasoline tests in which either stropped on (in the early tests) or integral (in the later
25.4-mm (1-in.) thick powder-filled panels were used, the tests) to the fitel cells and provided an extinguishant thick-
potassium bicarbonate extinguished the fire in slightly less ness of 19.1 mm (0.75 in.) or 25.4 mm (1.0 in.). The extin-
time (150 ms) than the Monnex!! (200 ms) in a single test of guishants tested were water, water with. 50%. ethylene
- each. In MLL-H-6083 hydraulic fluid tests, a 3.2-mm glycol, bromochioromethane (HaIon 1011), and dibromodi-
--- (0. K2S-in.) thick powder-filled panel containing potassium fluoromethane (1-lalon 1202). The fuel cells contained DF-2
bicarbonate reduced the resulting flash fire from 363 to 231 at ambient temperature. These tests were not as definitive as
ms. In %sts with hydraulic fluid per MIL-H-46170, a they could have been because the sirmdated fuel cells were
2S.4-mm (1.o-irt.) thick powder-filled panel containing improperly made: The seams were exceptionally weak.
potassium bicarbonate reduced the resttlting flash fire from They did show, however, that the filled jackets wouid
820 to 165 ms. These tests provided a preliminary evalua- reduce hydraulic ram damage to the fuel cell at the jet
tion of the effectiveness of powder-filledprtels. More work impact location and that the jacketed fuel cell showed prom-
should be done to define fie-resistant hydraulic reservoir ise in reducing fires. . -----
design features better. In 1987 a more definitive program was condu;d-bef.
In tests of four fuel cells and one fiel hose impacted by a 98) in which double-wailed fitel cells were tested. These
-- shaped-charge je~ 12.7-mm (0.5-in.) thick plastic bag pack- fuel cells contained heated diesel fuel, and the hollow waUs
ets of Purple K** were used to extinguish combustion of contained a liquid (water, water with high+xpansion foam
heated DF-2 diesel fuel (The bulk temperature of the fuel (HEF) or AFFF, water plus AFFF and propylene glycol, or
was above its flash point.) carried or expelled from an inter- bromochloromethane) or a pulverized (Purple K) or granu-
*A @et Of fmpdd CtlemiG3.t ktustries (la) Of ~% lated (monoammonium phosphate) solid. The conclusions
which is a carbamic powder formulated from the reaction poduct fkom this program follow:
of potassium bicarbonate and urea. 1. Jacketed fhel cells are more hydmulic ram resistant
**Purple K is a product name of siiiconized potassium bicarbonate than unjacketed fuel cells see subpar. 4-8.1.3. Figs. 4-38
a .smaBamount of putple dye coined by personnel in ttte US
The K is for the potassim, the purple dye was added to dk- and 4-39 ifhmtrate that the fuel cell wall at the jet exi~ as
courage personnel from using the material in food preparation. seen through the large hole in the outer jacket wall of the

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., MIL-I+DBK-684
fuel cells used for Tests 3 (Fig. 4-38) and 5 (Fig. +39), has a. growth of these organisms. .. ...
smaller hole than the fuel cells used for Tests 2 (Fig. 4-38) Also there is a concern that the water might freeze. In
and 4 (Fig. 4,39) do. This difference in hole size was proba- Test 11 of Ref. 95a 51-mm (2-in.) thick layer of water-filled o
,. ”.’ ‘bly.’~ausd- by the inertia of the jacket filler, “i.e., the fire. (no gel) plastic bags was installed just inside the simulated
e’xtinguishartt, to which the impulsive loads were passed; aluminum hull where the external fuel cell was mounted. A
the fisel cell wall was subjected to a simple impact, not to w similar 5 l-mm (2-in.) thick layer of ice cubes in plastic bags
impact plus a pressure loading around the impact location as was installed adjacent to the hull where the shaped-charge
was the outer jacket wall. jet e@.gd the test fixture. There was no sustained fire within
2. TM fire extinguishants that performed best were the test fixture after a shaped-charge jet perforated thefuel
water, bromochloromethane (Halon 1011), and Purpie K, cell and then the test fixture. The fireball at the entry wall
The fire-out times for the water tests were 85,36,77,35,41, lasted 9 ms, and that at the exit wall, 18 ms. Both fireballs
,. 90, and 105 ms, the fire-out time’ for the bromochlo- were p@mrily from the aluminum hull simulants. Fireball
,.
romethane test was 49 ms, and the fire-out times for the Pur- durations for a similar test (Test 9) without the water and ice
ple K tests were given in subpar. 7-3.2.2. The water tes@ cubes were 30 ms at the entry wall and 32 ms at the exit
included those with 25% HEF or AFFF concentrate. In all of wall. These times indicate “that the ice suppressed aluminum
these tests the filler thickness was 25.4 mm (1 in.), and the ilash less effectively. thah water but was significantly better
water was heated to approximately the temperature of the than air.
~~ ~esel fuel, which was at or above its flash point. Granulated A gelling agent will not reduce water vapor pressure, so
fire extinguishant is not recommended because the granules the water can still evaporate from the gel. The gel can
have a low solace-area-to-mass factor, nor are the water. harden when its temperature is below the freezing point of
~” additives HEF and AFFF recommended because mist or. water, but when the’ temperature of the gel is raised above ,
spray fireballs do not provide a surface the additives can . its -me~ting point the water remains gelled. This. gelled
. .. .. cover. “(nese additives forma layer over the surface of a water expands at temperatures below its freezin~point, as
burning fuel pool and prevent fuel vapor ffom leaving’ the ice does.
surface to fix with the air and burn. This situa~on does not
‘ exist with a fire fueled by a mist or spray.) To prevent bum- 7-3.2.5 Intumescent Paints and Coatings
-ing of pooled fuel, subpar. 7-3.2.8 provides a description of Intumescent materials react at relatively low tempera-
‘,. the use of the bilge. tures, swell while reacting, and then present a low thermal
*
This survivability enhancement technique shows great conductivity to heat. Intumescent materials are generally
promise. More work should be done to develop and verify hydrated solids and binders tha~ when exposed to fire, (1)
this technique. melt while absorbing heat, (2) become viscoelastic and lib-
,.
erate gases, usually water and/or carbon dioxide, which
7-3.2.4 Water Gel Subsystem cause the solids to swell and form a closed cell foam that
,., ..., ~~Gelled water -was initially developed for the National increases the heat transfer path ..and-decreases. the thermal
fieronautics and Space Administration (NASA) for use in conductivity of that path and (3) bum, dehydrate, andlor
spacecraft. A small plastic bag containing gelled water char (pyrolize) while absorbing heat. Usually it is the bind-
,- coild be fised. to put out a fire even under zero “gravity con- ers that bum and they are phenolic resins, epoxies, polysul-
- ditions (Ref. 63). These gelled water bags were’ either to be .” fides, neoprenes, and/or water-glass-based film materials.
thrown like a bean bag or applied by hand like a wet rag. Polysulfide, when used as a binder, or iron sulfide, when
Zabel (Ref. 95) demonstrated that gelled-water-filled used as a filler, liberates oxides of sulfur (SOX) that are
plastic bags, when penetrated by a shaped-charge je~ very toxic, and when they combine with atmospheric moisture,
.- effectively reduced the duration of fireballs. Gelled water they can form sulfuric acid (H.#04), which can dargage
,-, displays the same quenching characteristics as liquid water_.. electronic. components. Sometimes fibers, including glass or
but tends not to flow. This tendency reduces the potential ceramic fibers and mineral wool, are added to reinforce the
lealciige from vertically emplaced water layers. These char. Asbestos was used, but it usually is not considered at
gelled* water bags were incorporated in the AS,TB vehicle present. .:
,,
(Ref. 90). When intumescent materials reac~ the temperature
I One potential problem found during tests of the ASTB sequence of the various components is very important. The
vehicle was the. presence of algae in the gelled water. Hence acid-organic polyol must melt prior to or during esterifica-
the gelled water bags should be sterilized and.lor a bacteri- tion so that when the polyol decomposes through dehydra-
cide or algaecide should be added to the water to prevent tion (forming a carbon-inorganic residue), the released
*Ttie gelling agent used was Carbopolm 934, a product of B. F. blowing agent and the evolution of other nonflammable
Goodrich. From 1.8 to 2.270 by weight of Carbopolm was added to gases cause the carbonizing mass to foam. One of the pti-
water..Then, to bring the pl+ to between 7 and 8,.sufficient ammo= poses of the organic amine or amide, such as urea, a
nium hydroxide was added while the solution was stirred continu- melamine, dicyandiamide, and urea formaldehyde, is the
ously until gelled.

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MIL-HDBK-684 -

o;t!j
‘ release of gases-including C02 andlJH#mt physically
900
cause the fused organic mass to bubble or foam. If a phos-
‘1’$ phoric acid is use4 amides and amines act as dehydrating
- agents to.promote phosphorylation and enhance the conver-
sion of the carbon in the polyol to char. In addition to the
gases fi-om amides and amines, a halogettated organic mate- m
rial or other suitable material generally is included. These
materials release a large volume of gases that form bubbles
which result in the characteristic foam of an intumescent
system. AhhorIgh water vapor and carbon oxides rilso may
be released during dehydration and thermal decomposition
of the polyol, these gases will function as blowing agents
only if they are released at the proper time, i.e., after melt
but before solidification occurs. Thus to assure sufficient
gas is released at the proper point in the reaction, blowing
-ioo
agents with pmxletemnined decomposition temperatures are
/-H” —523*
-.
1
,/
employed, e.g., chlorine-containing para.fhs, which release 526
IiCl over a temperature range of 160 to 350°C, or P“ /
/ —736
melamine, which releases ammonk low molecular weigM — 746
hydrocarbons, and carbon oxides between 300 and 350”C. —
$00
Hydrated salts contain their own blowing agent, water
vapor. As the reaction nears completion, gelation and finally 10 M
0.0 1.0 2.0 3R 4.0 5.0 6.0
solidifkation occur. Time,min
The binder ensures a continuous and uniform structure
Forrrdatkm. Binder Fitter Fiber
throughout the coating system and helps to ensure a uniform
foam structure. It essentially hoids the intumescent system 623 Potywlfz’&ry SodiimM~Gcate ~=
526 Neoprane Sodii Metasikate GJass

o ,,,, and the inefi fillers together. It can be a thermoplastic resin

‘fi’!j :‘ or a convertible resin that hardens by oxidation, by poly-
merization, or by reaction with hardening agents. The resin
fllrm however, must not be so inflexible that it interferes
736
746
666
Foundr#Epoxy
Rexib!eEpoxy
Neoprane
SorXumMetae&ata
SodhJrn
Sybid
Wtasilicate
(s02)
Glass
Glass

Reprinted with permission. Copyigbt @ by Tecimomic Publishing

with intumescence. me binder must also incorporate the
COmpany, Inc.
expected properties of a coating system: (1) it is stable for
long periods in its praipplication state, e.g., storage in a can, Figure 7-18. Substrate Ternperature-Tirne
(2) it is noncorrosive%” it is easily appliecL (4) it presents Eistories for Actual Intumescent Formations
an aesthedcally pleasing appearance, and(5) it is resistant to (Ref. 115)
soiling, water, ultraviolet (W), and other environmental
effects. For combat vehicles the binder must also render the 51 s. l%e .postintumescent efkxive thermal conductivity
coating wear or abrasion resistant- was approximately 83.7 mW/(m-K) [0.0484 BtuJ(ft-h-°F)].
When subjected to flame, intumescent material begins to The vapors given off are water and carbon dioxide. When
react from the exposed surface inward. The temperature of the binder is neoprene, hydrogen chloride (HCl) is also
the substrate (the layer of material the intumescent coating given off.
is to protect) versus time is shown in Fig. 7-18. The four I.atumescent materials should not be used in the crew
active formulations (523, 526, 736, and 746) displayed .in compartments of comb vehicles &cause they emit Qox-
Fig. 7-18 contain sodium metasilicate, each with a different ious gases. They would-protect the equipment but-not the
binder. l%e fimt two (523 and 526) also conrain borax. The crewmen. On the other han~ intumescent materials could
resulting graphs indicate that intumesc.ent coatings can be be effecti~e in engine compartments and are effective in
tailored to the application- In all of these tests the ongbd ammunition magazines, as described in subpar. 4-8.42.
intumescent coating was approximately 2 mm (0.079 in.) Another potential use for intumescent materials is the exte-
thick. After the teaction, the expansion was 2 to 9 times the rior of the vehicle in order to reduce the effectiveness of
original thickness. In tests described in Ref. 115 for Fomm- A4010tov cocktails and “liquid h“, which are described in
Iarion 526, an initial thickness of 1.50 mm (0.059 in.) subpars. 1-4.1 .2.3 and 2-3.1.3. A third use is as an antifmtri-

,,ij[.
o
expanded to a char 3.61 mm (O.142 in.) thick The density
of the unaffected coating was 0.730 g/rnL and of the char,
!:i 0.202 g/mL. The material intumesced at 118°C (244”F) in
cide device in a magazine to prevent the burning propellant
charge of one cartridge from igniting another, as described
in subpar. 4-6.4.1 (Ref. 91).

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MIL-HDBK-684
7-3.2.6 Otl.ter Impedimertta holes, and the decking was not. hermetically sealed. There-
Combat vehicles must carry munitions for crew-served fore, it can be assumed that as long as the admittance of air
and individual weapons; tools, spare parts, and supplies for into the bilge is reasonably restricted, there is a good proba- 0
.:. ~~~
Wtintenaxrce;, water, rations, and personal equipment for .bility the bilge contents will not sustain combustion.
crew members; communications equipment arid supplies; Obtaining a liquid seal would in fact be counterproductive
and much other impedimenta to enable the crew and vehicle since the- leakage of combustible liquids must be able to
to remain” in the field in operational status for extended pen-’ drain past the decking into the bilge. These tests also estab-
,,, ods. ~s impedimenta can be used to shield andor prevent lished that heated diesel fuel will wick” up through reticu-
fires by proper selection and vehicle design. Test 10 of Ref. lated foam, other open-celled foams, rags, andExplostie”*
95 demonstrated that water quenches aluniinum flash and and provide combustible vapors at the upper surface of such
the hydrocwbon fireball when a shaped-charge jet p~ses wick-like items when they are. exposed to air. Items that
through an extema[ fuel cell below the fuel level, the alumin- could become wicks should not be stowed in the bilge.
um hull, the water container, a span curtain, and then into As was demonstrated in tests by Cosgrove et al (Ref. 96)
the troop compartment. Similarly, when a water container and explained by Stoll- and Chianta (Ref. 97), the decking
- was replaced by a box of loose 5.56-rmn cartridges, the box must be secured -to the vehicle to prevent explosions that
of car&dges apparently trapped muc~ of the hy&ocarbon occur underneath the vehicle from throwing the decking and
“fuel, but only the cartridges whose metal cases were perfo- bilge contents upward, which then injure or kill the occu-
rated by the jet contributed to the fireball (Tests 13, 14, 15, pants.
17,imd 18 of Ref. 95).
Impedimenta could safely trap armor flash an#or span 7-3.2.9 Other Passive Concepts
,:
and combustible fluids carried in. the. wake of a shaped- When planning the incorporation of fire suppression tech-
charge jet or KE penetrator. Loss of these impedimenta is niques in combat vehicles, the designer must start with a
,. ~~~
preferable to loss of the vehicle, and/or. its occupants:,’ thorough evaluation of the hazard(s) to be reduce4- the
:Men combustible fluids or combustible metal flm~ are effectiveness of the survivability enhancement devices or
trapped by impedimenta, usually within a storage corn- concepts that can be used, and the limitations imposed by ~
partment, the conditions within the compartment do not. other vehicle requirements. The hazards can be divided into
ordinarily foster ignition. the combustibles present and the threats that can ignite
them. The effectiveness of the survivability enhancement
.7-3.2.7 l?ire-Retardant Materials m
devices or concepts can be judged by whether they will (1)
‘ Fire-retardant materials are used primarily to reduce the prevent a combustible material from being in a combustible
probability,” or delay the inception, of ignition. These mate- form, (2) separate the combustible material from the igni-
niils eventually burn ‘in a conflagration and may produce tion sources at least for the time required to obtain ignition,
toxic fumes while burning or smoldering. Both of these phe- and/or (3) suppress any combustion that has occurred or
nomena should be considered when the ~ecision is made- reduce the effects of that combustion until effective extin-
: whether or not to specifj the use of fire retardants. ~~ guishment can be accomplished. When evaluating the limi-
When tie most hazardous combustibles-solid propel-. tations, the designer must always consider cost, weight,
lam of large munitions, mobility fuel, and hydraulic fluid— time, and the status of the vehicle. For vehicles being
..are rendered less hazardous by location; compartrnentaliza- planned or designed but not yet in production, there is much
: tion, or other means, fire-retardant materials can be helpful. more latitude in which to incorporate survivability enhance-
Any tire retardant used within a compartment to be occu- ment concepts than there is for vehicles currently being
pied by humans must not produce noxious products. used by troops. ”Retrofits of existing vehicles should be
much less complex than a complete rebuild, and such retro-
7-3.2.8 Bilge . fits should be limited to-replacement of components, addi-
The bilge, the portion of the vehicle between the hull and . tion of some items, and minor vehicular reworking. - ---
the decking, is the lowest compartment in a combat vehicle,
and unconfined liquids collect inside it. It is often used to 7-3.2.9.1. Fuel Cell Confine~ent
stow hazardous materials “because the location is less apt to A plastic or elastomeric cell provides excellent contain-
be fired upon when the vehicle is in hull defilade. Desi~ners ment of fuel, but such a cell cannot withstand the hydraulic
should note, however, that the bilge is highly vuhterable to ram forces resulting from a ballistic impact, especially at
land mines; particularly those with shaped-charge warheads” access ports or fuel line connections. By confining a plastic
duected’upward. fuel cell within a metallic structure so that the plastic cannot
~ The tests’ of bilge fires discussed in Ref. 112 demon- expand beyond its elastic limit, a well-sealed, ballistic-resis-
strate,d that a bilge covered with well-sectied flooring and
pfi”ally filled with heated diesel fuel is not prone to support *Explosafe”, a void filter material made of expanded aluminum m
combustion. In these tests; the decking plates had finger foil, is a product of Explosafe Ltd of Canada.

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MIL-IIDBK-684
tant fuel cell can be obtained. Such a .cornbination can be properties at. temperate ambient temperatures could be
.I1;!,
,,,,;,, U* M =ofits aS well as in initial designs. selected. To date, polyethylene appears less prone to crack-
,,)
o When a fuel cell in art existing vehicle is diagnosed to be ing at temperate temperatures, but it is combustible. Before
a hazard because it is located where it can be easily hit and such a mattial selection is made, the material properties at
because fitel cell failure can result in loss of vehicle and the lower environmental temperatures, i.e., temperatures
crew, that fiel cell might be rendered less hazardous by the down to -S4°C (-65*F), must also be considered.
addition of a confining wall. Work recorded in Ref. 112 US Amy helicopters use crashworthy, self-sealing fuel
demonstrated that a steel conlining wall can be added to cells made to the requirements of ML-T-27422, which
“ reduce the hazard to a small, easily extinguishable fire. Also specifies that the cell dces not have to seal when thedreat
the addition of a spill curtain, a layer of fire-extinguishant corns a hole, i.e., when self-sealing material has been physi-
filled packets or panels, and removal of potential ignition cally removed from the fkel cell. This removal occurs when
sources could preclude a t%e. Such a retrofit is eminently an armor-piercing incendiary bullet or a high-velocity frag-
practical, could be relatively inexpensive. and could be per- ment perforates the self-sealhtg material. Time missiles
formed by third echelon maintenance personnel. have sharp edges that act like a cookie cutter when perforat-
ing the elastomeric material. Conventional, self-sealing
7-3.2.9.2 Fuel Cell Material and Con6guration materials achieve a mechanical seal by having material that
Prior to 1959 fuel cells for rumored vehicles were made has been punctured by a Points tapered or ogival missile
of carbon steel. Since then, fuel cells have been made of reform to close the perforation. A shaped-charge je~ a plug
aluminum, stainless steel, nylon, Polyethylene% and a comp- or span from metallic armor, or a tigment from a KE pene-
osite of fiberglass and resirL Plastic is a particularly tempt- trator can core the self-sealing construction and thus prevent
ing material for fabricating a fuel cell. It is relatively the construction from sealing.
inexpensive and rotary molding can produce fiel cells rela-
tively inexpensively that have a homogeneous thickness 7-3.2.9.3 Reticulated Foam XWthina Combustible
without built-in weaknesses, such as seams. It is not yet Fluid Container
known, however, what material properties are needed or To preveent the explosion of fuel vapors and air in the
how to speci.@ the control of these properties. Also plastics ullages of airmail fuei cells, reticulated foam was placed
will not captwre secotxkwy missiles, such as tht? slugs h within the fuel cell (Ref. 118). Holten (Ref. 119) estimated
that reticulated foam reduced the hydraulic ram loadings by
Refs. 95, 112 and 1I 6 describe a total of 40 tests with six approximately 20% given a hit by a 23-mm HEIT below the
different elastomeric fuel cell materials: nylon 6, nylon 12, fuel level. Cosgrove et al (Ref. 96) am-ibuted smaller fire-
cross-linked polyerbylene, Hytrel@, Pebax@, and a conven- balls from shaped charges to the use of reticulated foam
tional, crashworthy, self-sealing material per MIL-T-27422 within the fuel cells. Those shaped-charge jets, however,
(Ref. 117). None of these sealed when perforated by a were traveling upwad through partially filled fuel cells;
: shaped-charge jet-At ambient temperature only the polyeth- thus the reticulated foam could well- have- 61tered. outfiel
ylene did not crack bul hydraulic ram did split it when a moving radially outward from the jet wake. See subpar.
weld in the confining box tiled. Twenty-six tests were per- 4-8.3.2 for a detailed discussion of tests of reticulated foam
formed with nylon 6 rotary-molded fuel cells. Containing used in the LVTP-5Al.
diesel ftiel at ambient temperature, these ceils usually Finnerty (Ref. 100) found that a hydraulic fluid reservoir
cracked, i.e., ruptured beyond the extent of rhe jet puncture, containing reticulated foam produced smaller fireballs in
and thus provided a larger opening for fuel leakage. When tests than did similar reservoirs without tie foam. This
b cells contained heated diesel fuel, tie of the eighteen result occuxred in one test recorded in the referenced repcm
cracked. (PIastics are usually less crack sensitive when and again in a reiteration of that test performed after the
heated.) Laboratmy “personnel who examined the material report was written.”On the other hand Zabel (Ref. 98)found
from a cracked ceil concluded that it contained no visible no benefit from reticulated foam yithin a fuel ceil given a
voids, whereas the material from the untracked cell did. ‘l’he horizontal shaped-charge jet passing through the fiel-wet-
probability that small voids in tbe plastic will reduce its pro- Wd reticulated foam, again in two similar tests. Zabel noted
pensity to crock is remote. More research is needed to estab- some “sparklers” in tie test fixture that were visible in
lish (1) the properties needed to obtain desired performance high-tie-rate motion pictures of these two tests; these
and (2) better control of fabrication to obtain the desired indicated more potential ignition sources, probably caused
P~C% or the fuel cell design should assure that even by the foam patticks burning. Similar sparklers were men-
with cracked or fractured fuel cells, there will be no gross tioned by Braadfladt (Ref. 120) in a reference to tests per-

,,.!,’j~!
o
dissemination of tie].
Because heated fuel is not desirable (It is more easily
“ :4 ignited than cool fbel.) and fuel at ambient temperatures
formed with Explosafe@ (expanded aluminum foil) within
the fuel cell. (Such “sparklers” prolong the existence of an
ignition source.)
could be used fuel cell materials that have more desirable

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MIL-HDBK-684
7-3.2.9.4- Ullagk Explosion Protection 7-3.3.2 Uses . . .-,.-
Aircraft, both fixed and rotyy wing, contain “fiel cells in ‘flie selection of handheld extinguishers should match the
their fuselage andlor wings that are of construction light extinguisher and extinguishing agent to the specific fire haz- 0
enough to need ullage explosion protection: The early ard, e.g., using AFFF for fuel pool fires but not for electrical
metallic external I%el cells also needed ullage explosion fires. Factors affecting the selection of the type of extin-
protection;. however, the filament-wound, external fuel cells guisher, such as the ease of use for the available personnel
made for the F/A- 18 and several large helicopters are and we physical ‘environment in which the extinguisher will
required to be strong enough to withstand the explosion of a be used are discussed in this subparagraph.
propane-air mixture. These” filament-wound fuel cells also Selection of a“handheld fire extinguisher should be based
withstand the hydraulic ram loadings from impacting tum~ on a number of factors including size, type of extinguishing
bling 14.5-rnm APIT bullets (Ref. 101). ~ agent, space and weight limitations, ease of operation, and
-While developing effective ullage explosion protection, cost. Most handheld extinguishers are relatively easy to use
designers tried many p~sive techniques. These techniques and do not involve, anymore operations other than to point
“are described by McCotick et al (Ref. 121). In addition, the container outlet at the fire, pull a pin, and either depress
active techniques were tied, which were the forewnners of a lever or squeeze a handle to release the agent. The size of
the active fire suppression systems used today in tie crew the extinguisher depends on the available area in which the
compartments of combat vehicles. Before the optical detec- crew member has to operate and on the size of the fire that
tion system was as well developed ~ it is cuqently, these the individual is expected to extinguish. Selection .of the
active systems did not prove effective in fuel cell ullages. extinguishing agent is a bit more complex because of the
Ground vehicles have an advantage over aircraft because nature of the fire and the fact that certain agents work well
,.,., .’.
there is not as great a need for weight reduction. Further, against certain material fires but will not extinguish all types
since ground vehicles are exposed to direct hits by huger - of fires. For example, carbon dioxide is effective against
threats, they are inherently stronger. Therefore, fqel cells of tires involving flammable liquids- and elecrnc -sparking
combat vehicles “should be designed and fabricated to be withjn a closed space. but is not effective against combusti-
strong enough to withstand ullage explosions agd hydraulic ble metal fires or deep-seated fires of ordinary combustibles,
ram loadings. Specific ullage-inerting devices should not be” such as paper, textiles, and hazardous solids.
needed. Fuel cells should be tested in their norgI~ installa= -Water w& the first extinguishant used in portable extin-
tion to prove their design. guishers. It is still in use today, but is not as common. Today
o
water extinguishers use carbon dioxide cartridges rather
,,
7-3.3 IL4NDHELD EXTINGU@H!NtS than the reaction of soda in water to pressurize the extin-
Handheld fire extinguishers provide the capability for guisher bottle. Water very effectively extinguishes cellulo-
crewmen to extinguish fires that are not appropriate for a sic fires, e.g., burning wood or paper, but it is not desirable
),
fixed fire-extinguishing system, i.e., fjres that fixed fire-ex- for fires involving electric discharges until after the electic
. tinguishing systems cannot extinguish because of the loca- . circuits have been interrupted. One -source of. fires in,.com-
., tion of the fire or the fixed fire-extinguishing system mercial aircraft is that passengers throw cigarettes into the
capabili~- or because the fire is external to the vehicle. In -- wastepaper containers in the rest rooms. This type of fire is
,, addition, handheld fire extinguishers are a morale booster difficult to extinguish using either dry chemicals or carbon
.- because they represent a capability for the cretien to react dioxide. HaIon 1301 was also ineffective in extinguishing
,. to a hazardous situation when all else fails. ~ese portable this type of lire; water, however, is excellent in this situa-
.:fire extinguishers are described in Ref. 122. tion. ”Airlines install a Federal Aviation Administration
,. (FM)-required Halon 1301 fire extinguisher in the rest
7-3.3.1 Types rooms, and some install a portable, water-type extinguisher
A number of handheld fire. extinguishers have been in the vicinity. of the rest room for such ..situations. :TTans
~.“designed for limited use against small fires and aremrrently World ~lines (TWA) has used this setup and has. encoun-
., “used in ground vehicles, aircraft, and a variety of ,other tered little or no problem in the use and maintenance of the
applications for which personnel are available to fight small portable extinguishers (Ref. 66). These portable extinguish-
fires. The use of lightweight and effective h~dheld fire ers, shown in Fig. 7-19, use small carbon dioxide cartridges
extinguishers is a critical part of ground ve~cle survivabil- to pressurize the bottle when the extinguisher is to be used
‘ ity because controlling or extinguishing a. fire in its initial and use GS-4m (potassium acetate) .to lower the freezing
stages prevents its escalating to an uncontrolled fire that can point of the water to 40°C (Ref. 123). These 1.6-kg
consume. the entire vehicle. Handheld extinguishers have (3.5-lb), water-type extinguishers have a range of over 6 m
been in use for a number of years and are available in a vari- (20 ft) and will flow for 30 to 45 s.
ety of sizes and contain a variety of agents. Extinguishing Dry chemical, portable extinguishers have been used
agents such as the halons, water, copper flakes, carbon diox- since 1928, and they are more effective against flammable @
ide, and dry chemical powders have been demonstrated to liquid fires than against cellulosic fires. Only one, monoam-
be effective against a number of different types of fires.
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fires), foundry flux (mixture of potassium chloride, barium

chloride, magnesium cttl~nyde, sodhtrtt chloride, and cal-
cium fluoride), and many others listed in Ref. 125-are not
. .. truly usable for a combustible metal fire on or in a combat
vehicle. Boralon~, a mixture of trirnethoxyboroxine
(TMB) and HaIon 1211 or 2402 (Ref. 126), is not ~pt-
able because of potential ozone depletion and for toxici~
reasons. The best candidate to extinguish combustible metal
fires in combat +’ehicles-is Navy 125S* (Ref. 8 l), which is
basically copper flakes. Both And and Amerex are cur-
rently producing, on a small scale, portable extinguishers
containing Navy 125S@ for the US Navy, which have a
13.6- or 113.4-kg (30 or 250-lb) capacity. If there is a need
for smaller combustible metal, portable fire extinguishers,
they can be made. ‘fhe.existing units are pressurizAm ith
argon. This type of extinguisher has been listed by Under-
writers Laboratones, Inc., for Class D lithium fires (Ref.
127) and is being evaluated for Class D magnesium fires
(Ref. 128).
Portable extinmtishers are most often used a~ainst.sus-
rained fires from a heated fuel or on a heated object, The
prime objective in such cases is to cool the heated fuel
(which is often solid such as a bag of clothin~ -eIecaic
wire insulation, paper, or wood) and/or the heated sur-
roundings. Normally the greatest cooling effect is
obtained by vaporizing a liquid extinguishant; the latent
heat of vaporization of water is 2254.8 J/g. For heat
transfer between a solid-the heated metal or the burning
wood, plastic insulation, or cloth-and a fluid-the extin-
guishanq the most significant determinant is the coeffi-
cient of heat transfer. Several representative coefficients
(hUtCSy of Kidde-Graviner ~ BerkshiRA En#and. are given in Table 5-1. Jf a liquid extinguishant droplet
impacts a hot engine block the coefficient of heat trans-
l?ii 7-19. Portable FE Extingukher, Water fer will be approximately 250 times that .of cool gaseous
Type extinguishant vapors passing by that same engine block.
Thus when liquid droplets of extinguishant hit a hot piece
monium phosphak is tawd for cellulosic fires, and it per- of metal or hot fuel, that hot metal or fuel loses some of
forms margkally. Most dry chemicals are also usable the heat required to vaporize the extinguishant. Large
against iires involving elecrnc discharges. These dry chemi- droplets of water can be-physically held tim a hot piece
cals, their relative effectiveness, and the ~s of fires for of metal by the steam flashed from the droplet. In this
which they are recommended, are tabulated in Table 7-14. case, many smaller droplets impacting the hot piece of
These extinguishers are usually pressurized by nitrogen or metal would cool the metal more quickly than would
dryair. TIM 0.9-to 2.3-kg (2-to 5-lb) dry chemical, portable. fewer. larger droplets. If the extinguishant wpmizes
b extinguishers have a range of 1.5 to 6 m (5 to 20 ft) and ettroute, as HaIon 1301 would, which has a boiling point
will discharge for 8 to 10s (Ref. 124). of -57.7°C (-71.9T) and a latent heat of vaporization of
For Chxs B and Class C fires, a 1.1- to 2.3-kg (2.5- to 118.8 J/g; the heat required would be taken from the air
5-lb) carbon dioxide, portable fire extinguisher has a range within the compartment.. This air would regain some of
of 0.9 to 2.4 m (3 to 8 ft) and a discharge time of 8 to 30s. that heat from the heated engine unless the cooled air
Most of the dry powde& exdnguishants currently in were forced out of the compwrment by the coolant air
use-gmphitei sodium chloride, “G-1 powdefl (screened, ffowing over the engine. This fact explains why engines
graphitized foundty coke plus an organic phosphate), remain hot and reignite fuel when either Halon 1301 or
Wet-L-X” powder (sodium chIoride base with additives), carbon dioxide is used to extinguish an engine compart-
Wa-X” (sodium carbonate base with additives for sodium ment tire, i.e., HaIon 1301 and carbon dioxi& cd the
convention is to call the Class B-Class C fire extinguisbants hot air in the engine compartment instead of the hot
w “dry chemical” and to refer to the ClassD-combustible metal engine.
h-extinguishams as“drypowdd’.

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MIL-HDBK-684
..
.,.
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o!.
fj 7-33.3 Selection Guidance a spray nozzle and valve combination could satisfy some of
Handheld fire extinguistters area necessity. They provide the need for a water-type extinguisher, but such a system
“Y::~ the best means to extinguish special fires and the most would be limited to use only in the crew comparanen~
..:. effective means to mmbat !ires that the fixed fire-ext.in- . Water is recommended over other coolant-type extin-
guishing system does not attack. I%@ fire-extinguishing guishants for use in occupied compartments because it
systems are designed to combat hydrocarbon fuel mist or presents fewer probIems during and after U. Potable
spray tires at specific locations within an enclosed space. water can be used in mist form even on ekctrica.1 fires,
They do not always extinguish and prevent the reignition of but the electricity should be turned off because the water
~ lires in ventilated spaces, particularly liquid pool fires, elec- will eventually-pick up-contaminants and become conduc-
trical fires, combustible metal fires, smoldering Ilres in bed- tive. Additives to the water such as AFFF and HEF are
ding, h in the air filtem of engines, burning UnifOtlIIS, not recommended by fire-fighting specialists unless there
6res of externally stowed gear, etc. Handheld extinguishers ‘- is a hy&ocarbon liquid pool fire. Water in mist form is
can extinguish these fires. Handheld extinguishers can also highly effective against most tires; deep-seated cellulosic
be used when the automatic system fails or has been fkes, however, require a sptay or. jet of water. A
expended. rechargeable, portable fire extinguisher, such as that
Pctrtakde fire extinguishers should be provided to extin- shown in Fig. 7-19, equipped with a selectable
guish the following types of fires: mist-spray-jet nozzle would provide an excellent tool for
1. Electrical fighting slow-growth Class & Class B, or Class C fires
2 Slow-burning combustibles, such as paper or cloth- within the vehicle. The water mist can also flush noxious
ing materials out of the air and reduce the hazard of smoke
3. Hydrocadmn liquid in either the crew or engine irdmlation, as described in subpar. 7-2.3.1.6.
rxxnpartmem The combustible metal extinguishants need further study.
4. Combustible metals, if present Many of those listed in Ref. 125, such as graphite and sand,
5. Fiies not completely extinguished by the primary are intended to be shoveled onto the burning object to cut
system off rbe source of oxygen. Navy 12SS@ is highly effective
6. Deepseated fires, such as occur in rubber tires or and presents a means to extinguish the fire without burying

oiif
“ the burning objecL l%e deep-seated plasticshubber fire
=or~&~ combustibles four basic extinguishant types are extinguishants need further study. At presen~ the only avail-
needed a general-purpose extinguishant usable in electrical. able extinguishant for bunting rubber is water (Ref. 130);
fires such as dry chemical. a cooling agent such as water, a formerly Halons 1211 and 2402 were recommended (Ref.
special Class D extinguishant for combustible metals, and a 131). Water with surfactants performs well. Fortunately,
persistent cooling and hating agent. small portable extinguishers should provide the fire-extin-
Dry chemical or a liquid haIon alternate is recommended guishing capability needed for both of these types of ties, a
over carbon dioxide for automatic systems in unoccupied . Navy 125S@ (copper flake) extinguisher-for combustible
compartments because either can be used to extinguish ekc- metals and a water extinguisher for burning rubber.
trierd fires: These extinguishants can be used in manual
extinguishers because they can be thrown fatther than car-
bon dioxide and thus allow a crew member to fight a 6.re
74 SYSTEMS
Two basic approaches have been used to improve fire sur-
-- from a greater distance. Expended, but unconsum~ dry vivability. One approach is to prevent the fire tim igniting.
chemical can have an effect should the fire reignite. Person- The other is to extinguish the Ii.re before the vehicle or its
nel using extinguishers of all types tend to use 10 to 100 occupants are affected. Elements of both approaches must
timeti the quantity of extinguishant needed (Ref. 30); gases be incorporated into the approach used in a combat vehicle.
dispmse, water evaporates, but powder lingers. There may
be a cleanup problem because much of the powder or its 7-4.1 GENEti SYSTEM Objectives :--
- products remain until removed by mechanical means, par- Tlte preferred approach is to prevent a fire from igniting
ticularly if the powder cakes in oil, hydraulic flui~ fuel, or by primarily passive means. The combat vehicle should be
other liquids. designed or modified to have the most hazardous materials
All combat vehicles carry water for the crew, usually in located where they are not apt to be hit or where, when hi~
19-L (5-gal) cans strapped or stowed on the vehicle some- their explosion andfor combustion products cannot seri-
where. ‘Ilte Cotnbtrr L#esaver Cburse, Medical T&ks man- ously affect the vehicle or its crew. ‘Ilk approach includes
ual messes the need for potable water (Ref. 129). design features that would reduce potential ignition sources,
Installation of a Wng water reservoir in combat vehicles eliminate potential combustibles, separate combustibks
is highly advisable. llte water could be used for drinking, from ignition sources, and reduce the availability of oxygen-
washing, and other purposes. Providing a small pump at the where tires cotdd occur. The potential for ignition of com-
bottom of the drinking water reservoir and a smalJ hose with bustibles is reduced by this approach to a fire survivability

7-47
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M! L-HDBK-684
system. A1l.potential catastrophic fires should be reduced to Halon 1301 does not travekjl in air (Gases do not travel
‘slow-burning or smoldering fires extinguishable by “crew well in other gases.), sufficient Halon 1301 must be used to
members. This system should, in hum, be backed up by fire flood the region of potential combustion. This requirement e
extinguishers. could also be necessary for an ahemate for Halon 1301 if it
The approach that seeks to extinguish fires: before the were gaseous when released. Flooding the region of
vehicle or occupants can be affected depends primarily potential combustion requires rapid employment and
upon an active fire-extinguishing system; Ideally, this sys- dispersion of more Halon 1301 than would be required if
tem would sense an incipient fire and activate w appropri- the extinguishant could travel in a more dense form. A
ately “sited fire extinguisher to extinguish the fire as soon ~ system that, achieves-total flooding is used zdso because the
it ignites. This active system depends upon sensors that can location of the fire is unpredictable. Halon 1301 is
react extremely quickly, a controller that can discriminate preferable to Halons 1211 and 2402 which are more toxic
between a fire and other phenomena afid activate @e appro- and do not work well in total flooding applications, and to
priate fire extinguisher, the fire extinguisher and its distribu: carbon dioxide, an asphyxiant for which a gas mask is not
tion system being sited to deliver exdnguishant to the fire effective. Dry fire extinguishants such as potassium ,bicar-
‘extremely quickly and effectively, and an extinguishant that bonate would be effective -:but would tend to irritate.. the
will quickly end the co~bustion. Additional protection is eyes and breathing passages. of occupants. Water mist is an
achieved if the fire extinguishant acts as an inertant and pre- attractive alternate; see subpar. 7-2.3.1.6.
vents reignition of the fire for the period of time ‘necessary
for heated, parts to cool down and combustible materials to 7-4.1.2 Engine an~or Cargo Compartment
be removed or if the extinguishant cools the fuel and fire The presence of hydrocarbon liquids in the engine com-
site. partment cannot be avoided. Objects within this compart-
,. ment can withstand more heat energy than people or other
7-4.1.1 Crew Compartment- . heat-sensitive objects within the crew compartment can. In
Regardless of whether an active or passive system is addition, extinguishants can be used within the engine or
used, the design objectives for the crew compartment are cargo compartment that are not recommended for use within
the same. The prime objective is to assure fiat the personnel crew compartments. The primary design objective here is to
are not killed or seriously injured by fire effects or fire sup- -- limit fire damage to the burning or charring of the surface of
pression. Secondary objectives include that the equipment the more susceptible items such as electric wire insulation
m
wiihin the crew compartment remains operable or at least and rubber fuel or hydraulic fluid hoses.
.tiat the vehicle is repairable and recoverable.’ Since current Within the engine compartment the presence of continu-
fiie-extin~ishin~. systems are ineffective in suppressing ous ignition sources makes inerting the compartment of
gun or rocket solid propellant cheti”cal reactions, use of major importance in order to prevent reignition of the com-
protective magazines is imperative. Therefore, the most bustibles. Also engine cooling requirements usually result in
hazardous- combustible to be treated by the fire-extinguish- ~ extremely high airilow within-the engine compartment.
ing system is hydrocarbon mist or spray of either the mobll- The ex~nguishant should be selected from among the more
ity fuel or hydraulic fluid. persistent agents, i.e., dry chemicals such as potassium
preferably, liquid hydrocarbon containers shciuld not be bicarbonate, liquid Halon alternates, and water. Neither
located in the crew compartment. These containers must be Halon” 1301 nor carbon dioxide is sufficiently persistent to
designed and fabricated not to rupture grossly” when hit, render the engine compartment effectively inert for the time
Also the locations of the liquid hydrocarbon containers are necessary for liquid hydrocarbons to drain to a safe location,
“important; however, the threat that can reach these such as a covered bilge, particularly because the airllow
containers’ arid puncture them will probably have enough through the engine compartment quickly removes the Halon
energy to produce a sizable spray within the crew. - 1301- orcarbon dioxide.
compartment. An appropriately desi~ed, passive system. The quantity of extinguishant to be dispersed by a fire
would assure that only a short-duration tkeball could occur extinguisher should be sufficient to inert the entire compart-
rather than sustai~ed combustion. This passive system, ment ~d-cool heated objects. Liquid extinguishants tend to
described in subpars. 7-3,2.1.2 and 7-3.2.1.3, would .. vaporize when they contact the heated surfaces present in
probably involve strengthening and confikng. the hydro- the engine compartment. These liquids will continue to
carbon container, compartmentalization, and a threat-re- vaporize over a period of time and thus provide longer term
leased fire extinguishant layer. inerting than gaseous extinguishants do. Liquid extinguish-
An” active ‘fire-extinguishing system would have optical ants, especially water, also cool the compartment and
sensors viewing the compartment from several aspects and thereby reduce the probability of reignition.
several nozzles covering the regions the hydrocarbon spray Cargo compartments are similar to engine compartments
could reach. The distribution lines should be relatively because there are no occupants; hence greater tleedom is m
short to minimize the response time of the system. Since allowed in selecting the extinguishant. Cargo compartments

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diiYer fi-om-engine. compartments by-the absence of high 4. Dupficaring. Duplicating the critical components is
,~ coolant airilow and heated surfaces, which absence can one of the most effective methods used to improve the
o ~‘j reduce the probability of reigrtition. Also cargo compart- survivability of a fire-extinguishing system because it pro-
ments are-more able to maintain inertion and therefore less vides a level of redundancy that allows the system to oper-
likely to have reignition. Cargo compartments do not neces- ate if a portion of the system is lost or fails. ‘Ihe use of
sarily contain liquid hydrocarbons, but they could contain multiple, parallel-wired fire detectors improves response
explosive or incendiary cargo. Again, rendeting the atmo- times and assures that even if a detector is 10SL the system
sphere within these compamnents inert is advisable. The will operate with the remaining detectors. Redundancy in
engineer should assure that whatever means are used to the agent distribution system requires either multiple bottles
inert the compartments will not produce toxic products of agent connected to the same disrnbution piping network
because they can leak into the crew compartment. or complete, identicrd redundant systems (bottles, valves,
For both engine and cargo compartments, if the cargo is and piping) covting the same area. ‘llte use of complete,
not energetic, the tk-extinguishing system can have a identical redundant systems provides a higher level of sur-
slower response than the crew compartment system. Meth- vivability; however, it is a more expensive technique in both
ods for stowing energeticmaterials are described in subpar. material costs and vehicle space and weight penalties. --
4-6.2. 5. Eiiminaring. If a flammable or combustible is not
absolutely necessary on a vehicle, it should be eliminated.
7-4.1.3 Fire-Extinguishing System Survivability This elimination should be done during the design phase of
To assure the smwivability of vehicle and crew, the fire- the vehicle and canied forward on a mission-by-mission
extinguishing system must also sutvive. The survivability of . basis. The principle is that the less there is to burn, the less
vehicle systems and their components has histoncall y fol- likely there will be a fire and the easier any resultant fire
lowed the A, B, C, D, and E of sumivabihty design: Armor- will be to extinguish.
ing the vehiclq Burying critical. components behind other -“ For an active fire-extinguishing system to function prop
items, Concermating many of the critical components, erly, control lines must remain intactj and several system
which presents less area to hostile threats and allows armor- components must be functional. These systems should be
ing of the clustered components with less weight from fail-safe in all aspects and should be as simple as possible to
armor, Duplicating to maintain functions if a component is . avoid incuming a higher than desired failure-t-alarm rate.
iIl~‘damag~
!,,
,,,, and Eliminating combustible materials from The possibility of losing components to ballistic or acciden-
o within the vehicle. tal damage must be considered. In a significant number of
1. Atnwtig. In the case of a he-extinguishing system vehicle tests, active h-extinguishing systems failed to
for a combat vehicle, the vehicle will already be armored. function because ballistic damage. severed an electric wire,
This armor provides protection from small arms fire and damaged a valve, or destroyeda controller.
from high-velocity figments produced by high-explosive
shells. Within the vehicle protection born objects that have 74.2 GENERAL SYSTEM DESCRtPTION..-
- perfcnzued the vehicle armor -ot be expected, but protec- Fire-extinguishing and prevention systems generally are
tion of the “fire-extinguishing system components and elec- either active or passive. l%e two are similar in some
trical _ses from spali and ricocheting particles of the respects. *y complete fire-extinguishing or prevention sys-
penetrator can be provided. tem. active or passive, must be designed to limit gun or
2. Bury”ng. Burying critical components is an efficient rocket propellant combustion andlor to divert the blast and
method used to improve the suwivability of a fire-extin- producrs of detonation so such effects will not affect the
guishing system by making use of the inherent shielding the vehicle or its crew. The Ml and M 1A] MBTs have separate
vehicle ant? its components offer. The strategic positioning magazines for the main gun cartridges, except the. few
of critical components, such as the control devices and eke- -. rounds in a basket on the turret floor. ‘Ike magazines are
trical harnesses, behind other components in the vehicle so separated tiom the crew compartment by sliding doors that
these items provide protection fkom span impacts and blast are normally closed. ‘Ihe magazines are designed to with-
loads will result in a higher survivability factor for the fire- stand the impulse from detonation of a single warhead
extinguishing system. therein, and -h magazine has a blow-away panel to vent
3. Cancenrran”ng. ‘Ihe technique of concentrating the the quasi-static pressure generated by such detonation either
critical components in a particular area is another method to the outside or into the engine compartment. This is a pas-
used to reduce the vulnerability of a system. On the other sive means to prevent the effects of such a chemical reaction
hantL concentration without any other survivability from affecting the crew or the vehicle. ‘l’his is an ex,amp~e of
enhancexnen~ such as axmonng or burying the concentra- a passive technique used on a combat vehicle that has active
on of components, may increase the vulnerability of the fire-extinguishing systems in both the crew and engine com-
stem because all of the critical components are now next partments.
to each other and are susceptible to a single hit.

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NW-14DBK-684
7-4.2.1 Active Systems malfunction ..given ballistic damage. Mobility-fuel-fired
Active fire-extinguishing systems sense combustion and troop compartment heaters might be replaced with electric
react to extingti:h that combustion by the discharge of w heaters and/or with hot air heated by the engine. It is foolish o
extinguiskrant.. These systems have sensors ~that detect to remove most of the mobility fuel from the troop compart-
parameters symptomatic of combustion, a controller that ment and then pipe some back into a heater to wait to be hit.
foIlows a set logic to signal extinguisher valves to open, Hydraulic power systems should use a truly nonflammable
electrical wiring, controls, and indicators, and extinguishant fluid or be replaced with elecrnc or pneumatic systems.
distribution plumbing including nozzles. In general; ~ Engine and cargo compartments should use insulation or
active system for the crew compartment uses optical sensors intumescent coatings-to minimize the effects of fires; The
and has an-extremely fast response. An active system for an bilge should be covered to prevent gross influx of air. Bilge
engine or cargo compartment can use optical or ~ermal sen- cover plates should allow leaked liquids to collect under
sors and have a slower response. Active systems cm usually them. Inherent in passive systems is the probability that
be activated manually when combustion is detected. some combustion, will occur. These systems are designed to
The advantages of an active system follow: - reduce the intensity of such combustion or to localize it so
11 The system can react to combustion” that” occurs that the crew can extinguish it with portable fire extinguish-
accidentally, i.e., for reasons other than ballistic impact, ers. The concepts of passive systems are described in sub-
such as the failure of a hydraulic line within “tie engine par. 7-3.2 and elsewhere in this handbook.
compartment. ,,.. Advantages of the passive approach include the follow-
2., me system is on standby and, requires only actua- ing:
tion to be put into use quickly. , 1. .The system is always on-line and cannot be turned
3. An automatic system does not require a gewman to off.
activate it. 2. The system requires little maintenance. However,
Disadvantages of an-active system include the following: checks must be made to assure that the troops have notaul-
1. The system is subject to damage that can prevent its lified the passive concepts, e.g., by careless placement of
functioning. Some active systems can be turned off manu- flammable objects or pressurized containers.
ally by crewmen and thus may not be available when 3. The system is not subject to false akwrns.
needed, 4. A properly designed passive system can protect
2. The system is predirected to cover regions in which many regions within the vehicle.
a
fires are anticipated to occur and cannot be redirected to 5. The system usually has lower life cycle-costs than
cover other regions in which combustion may actually an active system, particularly for new designs.
occur. The disadvantages of passive systems include the follow-
3. The system is subject to false alarms. ing:
4. The system is currently limited to one or two activa- 1. If jackets are used, as they are for jacketed fuel
tions: It cannot respond to, multiple (>2) fire “events. cells, inspection of the fire extinguishant is difficult. .. .. .
5. The system may “have expended its extinguishant or 2.” Personnel are not familiar with passive fire preven-
be inoperable when needed. tion techniques; therefore, until they gain confidence in the
-6. An aci.ive system requires maintenance and periodic passive system, it should be backed up with an active sys-
checking to assure it is functional. tem, at least a manually activated one.
3, Personnel unfamiliar with passive protection tech-
7-4.2.2 Passive System ‘” niques may inadvertent y neutralize a passive device.
A passive fire suppression system is present where the 4. ‘The passive device may not be activated by acci-
vehicle has been systematically designed and fabricated to dental fires.
minimize the probability of ignition, the effects of combus-
‘,-
tion, and the probability of a fire becoming sustained. The “7-4.2.3 Logic Fofiowed by Current US Army
most hazardous combustibles (explosives, mobility fuel, Active Fire-Extinguishing Systems
.,
and hydraufic fluid) must be removed from the crew com- The following is a brief description of the logic followed
,.
. . partment to the maximum extent possible. The explosives - by the automatic fire-extinguishing systems (Ref. 132) used
must be stowed where they cannot affect either crew or in the latest US Army combat vehicles, such as the FAASV
vehicle given a bit and subsequent reaction. Mobility fuel and some armored systems modernization (ASM) vehicles.
cells’ rriust k strong enough to resist gross. ruptur,e and be The optical fire sensor assembly (OFSA) per
,..
provided with threat-released fire extinguishant panels, or IWL-S-62546A responds to optical radiation from explod-
.,.
jackets where they are most likely to be hit. A paiwive tire ing or combusting atomized or vaporized hydrocarbons
extinguisher system, such as a double-walled fuel cell, and energizes the fire-extinguishing system within 3 to 4
. requ,j.res that the system suffer ballistic damage in order to ms, depending on the optical sensor type, when an o
function. In ‘most ways, passive systems are less likely to ener=~ level equal to or greater than the large fire thresh-
,,

,, 7-50
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MIL-HDBK-684
old is reached. The optical fire sensor systems are signal to iL If flow indications are not received within 38 ms
,,,$1intendedfor use in combat vehicles, crew and squad of the start of the drive signal for either or both of the extin-
o‘(~~ zones, and other compartments, such as engine spaces. guishers chosen initially, the MSEC provides automatic
----- System -standardizdon assures maximum interchangeabil- backup to select and apply drive signal(s) to the next highest
ity between various vehicle families. These systems are priority extinguisher and check its flow in turn. After the
designed to protect against the potential danger of deto- MSEC begins extinguisher activation, it ignores OFSA
nations, deflagration, and slow-growth fires caused by the large fire signals for 0.5 s and elearical-manual activation
presence of highly combustible fiels or other liquid signals for 4 to 6 s. If the MSEC finds no available extin-
bydmcarbons or flammable debris. . guishers when a hwgedire signal is presen~ it sequentially
The fixed fire extinguisher per ML-V-62547 and applies an extinguisher drive signal to each extinguisher
described in subpar. 7-3.1.1.1 is designed to be used with (with not more than 2 ms between consecutive drive sig-
the module, standard electronic control (MSEC). It includes nals). This drive signal application is done on the possibility
an integml pressure switch to indicate when the extin- that extinguishers indicated as unavailable may in fact be
guishant pressure drops below a presel limig i.e., 2.52 to usable. The MSEC does not apply subsequent drive sig@
2.76 MPa (365 to 4001b/h.2), and an agent flow switch to until extinguisher availability. is again indica@ as shown
confirm successtld extinguishant discharge after receipt of on Fig. 7-22.
an activation signal. This information is used by the MSEC
-. to determine extinguisher availability and whether extin- 7-4.3 DISTRIBUTION SUBSYSTEM
guisher backmp is required (See subpar. 74.4.2.). The A fire extinguishant disrnbution subsystem is needed
- extinguisher can be operated automatically, electrically and only by an active fire-extinguishing system. The distribution
manually, or mechanically. -and. manually. The system subsystem is used to provide fire extinguishant at the site of
usually operates as a tw~shoq two-extinguisher-per-shot the fire. Passive systems using threat-dispersed fire exdn-
system.- (Current systems in the Ml MBT or the BFV are guishants automatically broadcast the extinguishant where
single shot.) the threat wouid cause a fire.. The critical determinants for
The order of priority of the extinguishers in the system is disrnbution subsystem design are the overall system
1 (highest), 243, and 4 (lowest). Extinguishers are consid- response requirements and the type of extinguishant used.
ered available when pressurelflow switch and solenoid con-
,$$,, “ tititj~ are sensed by the MSEC in accordance with 7-4.3.1 WItltin the Crew Compartment
0
MIL-M-62545, shown in Fig. 7-20 and comected as shown ~ The design of the fire extinguishant distribution sub-
on Fig. 7-21. ‘Ihe MSEC follows the extinguisher activation system within the crew compartment is influenced by the
logic shown on Fig. 7-22. Whhin 2 ms of receipt of a large system response requirements; the type of extinguishant
tire signal from an OFSA or an elecrncal-manual activation used; the locations of sources of combustible hydrocarbon
signal from the test and alarm panel, the MSEC applies fluids; the size, location, and shape of the compartment and
extinguisher drive signals to the two highest priority, avail- the items within that can block or divert. flow the.location
, -“ able extinguishers. An extinguisher is not considered to be and direction of airflow from the ventilation system or com-
~ available for 8 to 10s after the MSEC has supplied a drive partment heate~ and the location, size,and number of extin-
guishers. l%e flow of an extinguishanq particularly one that
flashes fivm liquid to gas (as Halon 1301 does), must be
. through nozzles. These nozzles and the rest of the plumbing
and reservoir are designed to maintain a back pressure on
the extinguishant to prevent its flashing to a gas before
reaching the nozzle. Were the extinguishant to become gas-
eous before reaching the nozzle, the flow rate would be
greatly reduced. These nozzles must be optimized for each
application.
Because of the complex geometry of crew compart-
ments, the extinguishattt must travel a relatively long
distance from its release point to the fire. An extinguishant
that must travel in gaseous form, such as Halon 1301, is
quickly slowed down by the air within the compartment
because each molecule quickly loses momentum when
- Tech ~ViSiO~ colliding with the air molecules. If the extinguishant is in
-of~ %CifiC kktltitiC, ~ilrtei ~
mist (liquid) or powder (solid) form, the individual
o
;bI FWIW 7-20. Standard Electronic Control particles are significantly larger than the air molecules;
Module therefore, many collisions are required to reduce the

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MIL-HDBK-684

I I
I Test I
I I
and
I
Alarm
----- 1 Panel I
1- --i

‘a
I Valve 1 i I ,1
OFSA 1
1 I
With BITE
1-—
L —-— “.J
I

------
~ Valve 2 ~
OFSA 2 M@ule, T
-i Low-Prsksure& 1 --- --7 f- ~utomatic
----
WHh BITE standard r 1
I~. FlowIndicator ~ II
Eleetr@o ‘ Master ~ Fire- 1
----- “J I
Controi Swtich I I Extinguishing ~
(hISEC) t- ----- I
~ Valve 3 ~ L-_” --J 6.-&witc~~
OFSA 3 ~ Low-Pressure& $
With BITE I FlowIndicator I L 1
r--- --1 l--- --1

m
I L ---- -J
-- —--q
OFSA4
Lr I
Valve 4
1
1 L ----- j !-----d
With BITE , Low-Pressure&~
FlowIndicator
L --——- J ‘*
Figure 7-21. Block Diagram of Typical AFES Conf@ration (Ref. 133)

directed momentum of the extinguishant particles. Thus

gaseous Halon .1301 in ~r loses speed rapidly; therefore,
extinguishant in mist or powder form maintains its
distribution of HaIon 1301 beyond the nozzle is influenced
momentum to travel farther and more rapidly” than extin:,
by convection of the airflow within the compartment. ‘Iliese
~ishant in gaseous. form, aqd fire extifiguishers projecting
air ctients are also dependent upon the compartment venti-
a. mist or. a powder are said to have a greater reach than
lation system” and the crew compartment heater as well as
those projecting gas. Extinguishers with the greatest reac~,
on the h~on distribution system. In one M 113 AFES test
however, are those that project a liquid stream. Liquid can
catastrophic results oecw-red when the halon dkribution
alsobe projected as a spray, i.e., with larger particles than a
system was disrupted by the test charge detonation displac-
rriist.
ing an extinguisher bottle. Thus the Halon 1301 was not
A gaseous discharge from a nozzle will billow outward
projected as planned. (This incident is described in subpar.
radially to cover a greater volume in a shorter time than a
5-2.2 .3.3.) Hdon 1301 functions by flooding the crew com-
mist or powder discharge. This fact is important, to inerting
partment raker than” by being a stfeam -projected. into ~he
., the interior of a compartment quickly. Mist and powder bil-
combustion region. Because there’ is a system “response
low radially more than a jet. A spray can be made to expand
requirement of no further detectable combustion after 250
to the same dimensions as a mist, but the particles will be
ms, Halon 1301 has to be released quickly; therefore, the
much larger. Usually use of a jet or spray is reserved for
,. length of piping between the bottles and the nozzles and
nozzles being manipulated manuallyj not for those of an
restrictions of the flow passage are minimized. In most of
AFES. For an AFES to be effective, the nozzles used must
the current crew compartments, no distribution systems are
be selected for the application and positioned to direct the
used. Halon 1301 ‘is ejected from the valve at 5.2 MPa (750
extinguishant where it is needed.
lb/in.2) through a nozzle into the air. An alternate for HaIon
Current vehicle AF’ESS use Halon 1301. Halon 1301 is
1301 would have to be evaluated to ascertain the design fea-
released as a liquid but flashes ‘to a gas. ,A submerged jet of
tures needed for the distribution system.
,.
m

7-52

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MIL-HDBK-684

II Continuousfv
Monitor ‘ II
Nok Either a Large Fire
Signal From Any OFSA(S)
or an Electrical-Manual
Acth@icm Signal Shall be
T Considered a Fire Signal

Provides Drive 4-6s From

Signals to
- Extinguishers Ignore Subsequent
1-4 Consecutively

Yes Yes

O
,t,,
,:;f!,[
,,:,
44
Vo
Flow
on Both
Wnhm 38 ms
of ~
o
?
flow

dD
Within 38 ms

?o
‘o

Provide Drii --%

Y
t ( Signal to Next Provide Drive
Provide Drive Hig;k!#lJwify Signal
Provide Drive
Sgnat to Next Within 2 ms of I
Signals to Both Hig:;~k~irity Extinguishers
Remaining
Extinguishers

o Extinguisher
Wtihin 2 ms of A
o
Within 2msof ~
Within 2 ms of ~
o B

Yes

1 flow
or More on Both
MA&g#br:rs Wtihin 38 ms
f \
No
?
Yes
9
o
of B

0+
No

Figure 7-22. Extinguisher Activation Logic (Ref. 133)

7-53
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M! L-HDBK-684
,. ‘7-4.3.2 -W@n the Er@ne red/or-Cargo Corn- 7-4.4 AUTOMATICELECTRONIC CONTROL
partrnent SUBSYSTEM
The design of the fire ex~nguishant distribution sub- The development of rapid response and reliable fire o
:,. systemwithin an engine andor” cargo compartment is influ- detectors, both optical and thermal, has made totally auto-
enced by the same factors as it is for the crew compartment. matic fire-extinguishing systems possible for combat vehi-
The main differences are the high coolant airflow for the . cle applications. The advamces in detector response time,
engine, the high heat of the engine, the system response false alarm immunity, and reliability, as well as those in
requirement, and the choice of extinguishant. The systern. development of the control electronics necessary to inte-
response requirement for an unoccupied. compartment grate the detectors -and the agent-dispensing subsystems,
allows more time than it does for an occupied compartrnentl have enabled designers to develop fire-extinguishing sys-
The choice of fire extinguishant is no longer determined pri- tems that respond and extinguish fires within milliseconds.
m“tily by human exposure, so other fire extingui:hants can The actual design and response criteria for the detectors are
be used. Although the prime means of extinguishing com- covered in Chapter 6. The automatic fire-extinguishing sys-
bustion is still by flooding the compartment, the cooling. tems, such as the optical detection system used in ~e-AAV
effects of the extin’guishant are also important. Distribution 7A1, can sense a fire, sound an alarm, and dispense the-fire--
of the extinguishant is helped by being able to use liquid or extinguishing agent in 12 to 15 ms (Ref. 82). Tests were per-
powder extinguishants. The liquid extinguishant could be formed on an AAV 7A I vehicle in support of the live-fire
water; the powder extinguishant could be potassium bicar- tests in which a rocket-propelled grenade (RPG) -7 warhead
bonate., Both liquid and powder extinguishants. have better was fired into the vehicle through the exterior armor and the
“throwing capabilities. They are also more persistent and fuel cell and caused a fuel mist deflagration in the. crew
thus result in a longer period of compartment inertness. compartment. The time necessary to contain the fireball
., Engine compartments are different from crew compart- ranged from 27 to 52 ms, and the time necessary to achieve
ments, because there is much less unoccupied space and. total suppression varied from 45 to .225 ms. Posttest inspec-
there is a much higher airflow; (The higher airflow is tions of mannequins placed in the vehicle showed no evi-
required to cool the engine.) This: Mgher airflow affectS dence of burning of either the mannequins or their clothing.
extinguishant distribution and must be considered. Engine These extremely fast suppression times show the efficiency
compartments can withstand hydrocarbon spray fireballs with which the AFES detects- and extinguishes a fire—
and short-duration small fires. Fires are less easily detecte+ before catastrophic results can occur.
*
by optical detecto~, because engine ~omponents that are Since cument automatic fire detection and extinguishing
densely packed into engine compartments are in the way. systems are so reliable and can be designed to be nearly
,. Thus fires often exist longer in engine compartments before false alarm proof and yet can respond in such a short time,
the extinguisher system is activated. This delay results in automatic systems currently are. used in combat vehicles to
greater heating of items within the compartment.” For these assure protection from combustible fluid spray fires. The
reasons, it is more important that the extinguishant used in demonstrated ability of these.systems to, extinguish, fires in
I
the ‘engine compartment be more persistent thap the one milliseconds definitely outweighs any problem that could
used’in tie crew compartment and that this extinguishant be arise with false alarms. -Automatic systems are subject to
capable of cooling the heated items. Due to its normally hot. ballistic or.accidental damage that can render them inopera-
enviionrnent, extinguishers are usually. not locakd within tive; therefore, they should have fail-safe features and
the engine compartment unless they must be thereto obtain redundancy designed into them. At the time this handbook
the “desired performance, such as the linear fire extinguish-’ was being preptied, the main challenge for automatic fire-,
ers described in subpar. 7-3.1.5. The extinguishants would extinguishing systems was identification of a satisfactory
not necessarily be distributed by plumbing but could be alternate for Halon 1301.
explosively launched as described by Finnerty (Ref. 86),
who used a short length of Pxirnacord@ to disperse’ water 7-4.4.1 One ShoL.’Wo Shots, or ~ Shots
horn a plastic bottle to extinguish combustion of solid pro- Current electronics and controls allow a designer to add a
pellant grains on a tray; however, such explosive and liq- level “of’sophistica~on to fire-extinguishing systems and to
uid-filled devices would have to be protected horn the design them to be either single shot or multiple shot. The
engine heat. multiple-shot extinguishing system enables a combat vehi-
Passive fire protection techniques have been demon- cle to continue operating with an available extinguishing
strated (Ref. 98) that, include a double-walled or jacketed system even after having sustained a hit that resulted in a
fqel cell. Again the threat distributed the fire extinguishant fire. Ce~n fire-extinguishing systems, such as the Kidde-
(Water, HaIon 1011, and potassium bicarbonate were suc- Graviner system (Ref. 134),-utilize a multiple-shot electron-
cessfully tested.) into the region in which ‘tie hy~ocarbon
mist fireball existed.
ics controller and are designed to function for up to three
shots and use two suppressant bottles per shot. Combat
vehicles can be expected to be hit more than once, so the
0
, .,,
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MIL-HDBK-684
designoftbe.extinguishingsystem wiU be influenced by the 7-4.4.3 Response Requirements
for vehicles to smive multiple hits. A multihit 6re-ex- ‘Ihe response requirements for ao automatic fixed lire-ex-
ishing system requires multiple extinguishers to pro- tinguishing system are based upon the combustible to be
.- -tide-for .thc multiple shots; each valve and bottle are used . . . extinguished and the items to k protected h fire effects.
for a singie sho~ (At the time this handbook was prepared,
dual-shot extinguishers were under development but were 7-4.4.3.1 HydrocWbon Fluids in Mist or Spray
not ready for vehicle application.) Form
llte logistics of multishot fire-extinguishing systems do When the combustible is a hydrocarbon mist or spray in
not pose any particular problem to the designer because the personnel-occupied compartments, the fire-extinguishing
mtdtishot system uses solenoid valves, which are excellent system must respond rapidly enough to protect rhe crew.
for high—pressure situations. Because the system uses a new Currently, a system response that assures extinguishment
bank of bottles for each shot, the vehicle should not have to within a crew compartment of all detectable combustion
lose its fire-fighting capability when the first shot is dis- within 2S0 ms of threat impact is acceptable. The AFES
charged. must protect the crew from receiving second-degree bums.
(A superior system requirement would be to preclude the
7-4.42 Backups for Automatic Extin@shers and occumence of these fireballs by use of a passive system as
for Automatic Systems discussed in subpar. 7-3.2.) Actually the requirement is to
Automatic extinguisher backup is a system that checks extinguish the fireball that results from a shaped-charge jet
the presence of extinguishant within a bottIe and electrical or high-velocity KE penetrator going through a combustible
continuity to the valve and automatically sequences to an fluid container. ‘Ibis type of combustion does not have time
alternate bottle to assure that extinguishant flows into a pre- to heat the comparanen~ the compartment walls, or-any-
selected space. The presenee of extinguisbant is established thing within the compartrnen~ therefore, tie extinguishant
by bottle pressure, and low bottle pressure is signaled to the has only the incipient “fire” to extinguish and does not have
crew. to cool surrounding objects. Crew compartments generally
Automatic extinguisher backup should not be confused do not contain ignition sources other than those that are
with either a backxtp for the automatic system or system threat caused. Therefore, reignition is not as great a problem
redundancy. There are two types of backup for ah automatic as it is within the engine compartmerm ..
,,,~~
,M system. One is used when the automatic system fails to acti- When a threat causes hydrocarbon mist or spray within
o vate extinguisher bottles, a manual activation handle or an engine compartmen~ the response requirements are dif-
switch is provided (See subpar. 7+.5.), and the other is used ferent. FmL continuous ignition sources, such as tie com-
when the automatic system fails to extinguish the fire, either bustor can of the Ml MBT turbine engine, exisq thus the
a manual system is provided or portable extinguishers can threat of reignition is continuous.as long as fuel and oxidiz-
be used (See. subpar. 7-3.3.). ers are present. Second the items more susceptible to dam-
.. . .- Current fire-extinguishing system design incorporates a age by fire are electrical cable instdation% rubher,mahility
backup system for automatic the-extinguishing systems. fuel or hydraulic fluid hoses, and lighter weight engine com-
This backup system, however, has primarily been a manual ,- ponents, although even these items can char a bit before
backup so a crew member can discharge the extinguishing becoming inoperable. The response time needed for the
system should the automtic system f%i.1to respond. Most of fire-extinguishing system is a function of the radial burning
the current combat vehicle fire-extinguishing systems have rate of the outermost layer of these items and the kindling
very limited redundancy built into them because of the temperature of that material. In this case, the heat generated
severe space and weight limitations placed on these extin- by the fire rather than radiation from the tie causes damage.
.gtishing systems. ‘The redundancy is usually limited to the ‘Ilte fire-extinguishing system response can therefore be
agent storage bottles. As previously mentioned in this chap- much slower and measured in seconds rather than millisec-
ter, the use of redundant components whenever possible is onds. me extinguisban~ however, should be different also.
strongly recommended, especially in regard to critical com- In this case, reignition-is a significantly greater problem.
ponents, e-g., the detectors, control electronics, electric wir- The compartment should be inerted long enough for the
ing, and distribution system. If limitations preclude the use combustible liquid to drain into the bilge, and whichever
..
of cornpiete backup systems, the designer should assure that components have been bested above the ignition point of
as a minimurnj the fire-extinguishing system has a manual the combustible fluid should be cooled. For some applica-
backup so the crew can activate the &e-extinguishing sys- tions a response time of 15 s has been established for this
tem should the automatic fimction fail. Another reason to engine compartment fire-extinguishing system, i.e., 10s for
have a manual backup is to allow the crew to trigger the fire detection (allowing for thermal detection) and 5 s for
,,,1,, iire-extinguishing system if vehicle power is lost. This capa- lire extinguishment.
““‘“?’bility requires the use of a backup battery to provide temp~
0
rary power to the solenoids and other electronics if an
electric-manual system is used.
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MIL-HDBK-684
‘7-$4.3.-2’ Explosives, Low and High : ~~ nuity of the control. electronics and of the detectors; agent
V/lien tie combustibles are explosives initiated by pene- bottle preswires; and control unit status. There area number
tration. of a jet or high-velocity penetrator, the resulting of totally automatic BITE systems, which are used in cur- 9
‘dximical-reaction is probably either a deflagration or a deto-. rent fire-extinguishing systems, such as the M992 FAASV
nation. Fire-extinguishing systems do not exist that can engine bay test and alarm panel, illusnated in Fig. 7-23,
react in time to halt these chemical reactions. Further, low which monitors a thermal wire sensor and two bottles (Ref.
explosives (solid gun ok rocket propellants) are usually in a 136). A crew bay test and alarm panel, which appears
metallic or combustible case, which, even ‘if perforated by almost identical externally to the engine. panel, is designed
the jet or penetrator, would prevent the bulk of any extin- to monitor four optical detectors, four bottles, and: one
guishant from reaching the propellant grains. “Extinguish- amplifier (Ref. 137). The Kidde-Graviner control unit (Ref.
ment ‘of propellant grain combustion must be accomplished 134) features a totally automatic BITE that displays-system
by cooling (Ref. 86). Even when the propellant is in the faults includlng detector faults, cable faults, extinguisher
form of a caseless cartridge, the extinguishant cannot cool faults (low pressure or -loss of electrical continuity), and
more than the external surface of the propellant.. Therefore, control unit failure on an. alphanumeric display located in
a fire-extinguis~ng system is not truly applicable unless it the front of the control unit. The actual faults are displayed
effectively reduces the probability of fratricide (a cartridge as a coded message. The crew bay test and alarm panel
causing initiation or ignition of the explosives in an adjacent monitors the circuitry within the unit and isolates any defect
cartridge that would otherwise not be initiated or ignited) or . of any module within the fire-extinguishing system and
the effects from the cartridge that the jet or penetrator initi- gives a diagnostic display.
ated or ignited. A better survivability ‘enhancement system As mentioned previously, some of the optical detection
for explosives is one that prevents fratricide so that the only systems have automatic BITE, e.g., the automatic optical
cartridges to react are those directly impacted by the threat integrity test for W detectors. -Some of the infrared.(R)
and vents the overpressures outboard. These systems are optical detection systems, e.g., for the M 1 MBT and .M2/
described in subpam. 4-6.2.2 and 4-6.4.1. “ M3 BFV, require the crew to use a separate test set. The
fire-extinguishing system test set used to check out the
7-4.4.3.3 Other Combustibles dual spectrum IR detector (Ref. 138) contains all of the
Other combustibles include wire insu~ation, clothing, BITE electronics and controls necessary to perform
paper, and other items that may be in the vehicle,. Most of checkout tests and to verify the results. The unit gener-
these are extinguished by cooling. These combustibles 0
ates test and timing signals to the infrared radiation unit
present a response problem when hydrocarbon fluids or gun (which is used by the crew to test the optical detectors),
or rocket propellants can be ignited. A slower response, provides the necessaq threshold and logic circuits,. drives
such as is provided by a heat sensor or even a smoke detec-
tor, is adequate. Smoke detectors, however, have” a problem
of false alarms, particularly when weapons are fired or when
dusty conditions prevail.
An AFES would probably not be used with these other
combustibles. Extinguishment of the combustion of these
items could be better decided and directed by a human using
portable fire extinguishers, manual activation of a fixed
fire-extinguishing system, or other means.

‘7-4.4.4 Btiilt-k Test Equipment (BITE)

The use, of built-in test equipment (BITE), to determine.
the status of the fire-extinguishing system is definitely an
aid to the crew in reducing the -time spent doing routine
checks. BI~” can be as simple as a gage that monitors sys-
tem status such as pressure and moves a “flag” or needle to
indicate a certain condition, or it can be as sop~sticated as
the automatic optical integrity system used (Ref. 135) to
check a W detector for loss of sensitivity caused by a dirty
window or an electronics problem or failure. This type of
BITE capability is required in MIL-S-62546. BITE should Courtesyof HTL/Kin/Tech Division, Pacific Scientific, Duarte, CA
be designed and .irnplemented to determine system status of
the following components as a minimum: detector integrity Figure 7-23. M992 FAASV Engine Bay Test
(whether the detector is optical or thermal); electrical conti- and Alarm Panel (Ref. 136)

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MIL-HDBK-684
-- the lamp -indicatom and contains its.own power source. tus, and control-unit failurdnacklition, the control unit has
!,’ ‘l%e infmred radiation unit provides infrared radiation of a check of the test lamps and the alphanumeric display. ‘Rte
!;~’(f
o the proper spectral bands and energy levels to determine M992 FAASV crew bay test and alarm panel (Ref. 137)
-. ‘. ---whether +x not the optical sensor is operating properly. . contains lamp test and system test functions. In addition,
The rnajon~ of the BITE in use for testing the agent this unit has a built-in timer that keeps the extinguishing
storage systems consists of system self-checks of the system active for three hours after the master power switch
actual storage bottle. Because the majority of the current for the vehicle has been shut off.
fire-extinguishing systems use a pressurized extinguishing
agenL the crew needs to know the pressure in the extin- 7-4.S MANUAL ACTIVATION
guishant quicldy and accurately. Extinguishers include a The following reasons may lead to selection of a manu-
gage to measure the pressure of the agent as part of the ally activated fixed fire-extinguishing systenu
valve. ML-V-62547 valves (Ref. 139) use a tempera- i. The compartment and its contents are not overly
ture-coordinated pressure gage to measure bottle pressure susceptible to Ike damage, so a slower fire-extinguishing
because of the wide variations in pressure caused by bot- system can be used. .. .
tle temperature. The gage uses a green “flag”, which 2. False alarms have plagued an automatic control sys-
moves with temperature, and a black needle, which tem.
moves with pressure. This setup aLlows the crew to iook 3. The extinguishant can adversely affect crew and/or
for a black needle over the green background for a nomi- cargo.
nal status compared to having to read a pressure that 4. The cost of this system is less.
would then have to be compared to a temperature versus In addition, backup or optional manual activation control
pressure “go n~go” than Electrical continuity is contin-- features may be included in the automatic system. A detec-
. uously monitored between the controller and extinguish- tor system should provide a signal that a tire has been
ers. At the same tire% the pressure switch in the valve detected in a given location. This fire indicator is usually
relays information to the electronic controller so that if located adjacent to either an electric switch or a handle that
the pressure of the agent is very low, an indicator light is used co activate the fixed &e-extinguishing system. The
will signal that service is required on that component, fire extinguisher activation signal is transmitted through
and the controller can select an alternate bottle. electric wire or through mechanical motion, i.e., a cable,
n,,’;j*’
,, System test and alarm panels should aiso be designed to rod, or shaft. In both cases the mechanism is subject to bal-
include BITE capabilities so that the crew can test the oper- listic or other darnage that can render the manual actuation
ational status of any lamps or lights on the panel. In addi- capability of the fire-extinguishing system inoperable. Lack
tion, the test panel should have a capability to perform a of a detector system in an unoccupied comparunent can lead
self-test to determine whether there are any faults in the to fires not being detected. Data from the USASC, which is
electrical circuits and to check for ektctricai continuity in discussed in subpar. 4-1.1, yielded many instances of the
the wiring. The system designed by Spectronix Ltd (Ref. commander of a second vehicle zadioing the commander of
140) for use in the engine compartment of an rumored vehi- the vehicle in tint of him that the tint vehicle is emitting
cle has integral BITE to determine the status of the lamps on smoke and apparently is on tie.
the control box. The system automatically checks for elec-
trical faults in the control box and performs a continuity 7-4.5.1 Ektrical-Ma.nual
check of the overheat detection wire used by the system to An electrical-manual system is one that requires the crew
detect fires. member to initiate the extinguishing system by depressing
or closing an electrical switch to activate the extinguishing
74.4S T- and Alarm Panel system. This electrical-manual activation could be wired as
‘f’hetestand alarm panel should enable a crewman to see .an ove.mi& to 4he logic system Le., the human must-make
the vital information on the status of the tire-extinguishing the decision. A v&Uion could be provided that comects the
system so he can tell at a glance that the system is opera- switch directly to the extinguishers by separate wires and
tional In a combat situation the mew does not normally provides a redundant means to actuate the fire-extinguishing
have time to do any detailed system troubleshooting or system.
interrogation. Ideally, a test panel should provide informat-
ion only on the most criticrd components of the fire-extin- 7-4.5.2 Medtanicsd-Martttal
guishing system: system power, detector status, agent bottle A mechanicaknanttal fire extinguisher initiation system
staw and control unit status. As previously mention~ the uses a mechanical device such as a cable, rod, lever, or shaft
Kidde-Griwiner control unit (Ref. 134) features an alphanu- to trigger the extinguislthg system. Such an activation sys-
meric display on its tint panel. This rdphanumetic display tem could be used in lieu of or in addition to the elearical-
wiIl show system faults including detector fauks, cable manual activation system. In this system one or more
faults, suppressor faults such as low pressure and empty sta- handles are provided for crew members to use.

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MIL-HDBK-684 ““
7-45,3 ----Placementof-Actiwition.Handles +d 7-5.1 COMBAT VEHICLES
Stitches ,,.
Markal activation handles and switches for combat vehi- 7-5.1.1 Desc~ption of US Army Systems ‘0
., :.,.. -cles should be placed where. crew members can reach them Operational requirements and design guidance objectives
when there is an active fire. Redundant capabili~ should be are established for US Army equipment by the US Army
provided so that the crew can activate the extinguishers Training and Doctrine Command (TRADOC). The opera-
from inside or outside-the vehicle. Manual activation capa- tional requirements thus established for fire-extinguishing
bility should be independent of vehicle ‘power. Handles and systems for current combat vehicles are:
:switches must be clearly labeled and positioned ‘to minimize 1. APCM1132 No requirements . .-
inadvertent activation.: There was one USASC fire incident 2. MBT M60. No requirements for the original model.
reported during which the driver evacuated without pulling (A requirement for an AFES to be retrofitted has been can-
the internal fire extinguisher handle located beside his seat. celled.)’
The fire became quite active; no one dared to climb into the 3.’ MBT Ml. “...shall have an integral. fire detection/
vehicle to actuate the tire extinguisher. A redundant external suppression. system for.,cresv and engine compartments, with
handle would have, allowed personnel to activate the fire a non~ogic extinguishing agent.” ... ....
extinguisher from, outside the vehicle. and thus greatly 4. BFV M2/M3. “ ...rnust have a fire suppression sys-
reduce Iire damage. tem.”
5. .FMSV M992. “...shall start to extinguish fires
7-4.6 ROLE CM?HAND~LD EXTINGUISH- within 200 ins.”
ERS .:
6. TRV M88A1E1. AFES desired that extinguishes
i%ndhel~ fire extinguishers are necessary’ in combat fires within 100 ms.
vehicles because they can be used for fires that ‘automatic, “C~ent US Army combat vehicle fire-extinguishing sys-
semiautomatic, or passive fire suppression systems cannot tems described in the following subparagraphs-are the. Ivf60
or do not exting~sh. Handheld fire extinguishers provide a and M 1 MBTs, the M2/M3 BFVS, and the M992 FAASV. In
fire fighting capability when the vehicle is not operative and addition, the fire suppression system for the ASTB is
when there are fires outside the vehicle. described. See Table 7-15 for the characteristics of the fire-
Handheld fire extinguishers are needed to* extinguish extinguishing systems.
combustible metals fires, deep-seated fires, slow-burning
fires such as cloth or paper, fires that a fixed fire-extinguish- 7-5.1.1.1 MI13 Armored Personnel Carrier
,, ing system does not address because of location or extin- The Ml 13 series AIWs have a manual crwbon dioxide
guishant inconipatibility, and fires that occur or persist after FFES for the engine compartment. The 2.3-kg (5-lb) extin-
the fixed fire-extinguishing” system has expended its extin- guishant bottle of the system is located in the crew compart-
guishant. For some ‘vehicles handheld fire extinguishers will. ment: There is no fire detection system, but there is a “”
be the only systems available because there is no system. ,. handheld extinguisher, also 23~kg..(5-lb) carbon .dloxide, in
installed or the extinguishant was not replaced. For a pas- ,. the crew compartment at the rear on the right wall.”
sive fire suppression system, appropriate handheld extin-
,-’
,.
$! guishers are an excellent secondary system. 7-5.1.1.2 The M60 Main BattHeTank
Handheld extinguishers containing a dry chemical or The M60 MBT has no fire protection for its main gun
.’ .’
appropriate liquid extinguishant are recommended for fight- ammunition, which is stowed in the forward part of the hull
..
ing most li~uid hydrocarbon fires because hey c% be ‘used beside the driver, in a turret bustle magazine, and in a ready
,,. ... . where there are sparking electric igni~on. sources. The dry rack on the floor of the turret basket. Mobility fuel is carried
.. chemical and liquid extinguishants have better. carrying in two welded aluminum fuel cells located in the engine
,. properties and can inert an area longer’thanagaseous extin,.. ~. compartment, which. is separated from the crew.,.comtmrt-
guishant such as Halon 1301 or carbon, dioxide. The spark- ment by a fireproof bulkhead. The turret traverse is acti-
ing electrical ignition source should be deenergized. A vated by hydraulic fluid pressure accumulated by the mmD
..
water-based extinguishant with AFFF or HEF added is ret- for the” hy-draulic system, which is driven by ‘an e~ectri~
ommended for fuel pool-type fires because it can provide a motor.
:. film on the surface of the fuel pool. A handheld extinguisher The engine compartment is equipped with a fixed fire-ex-
.,,
containing an appropriate Class D agent is one of the few tinguishing system with two external and one internal
,, . means of fighting a combustible metal fire. mechanical-manual activation handles and three 4.5-kg
(lO-lb) ‘bottles of carbon dioxide in a two-shot system. No
7-5 EXAMPLES fire detection is provided for either the crew or engine corn-
The current usage” of tie-extinguishing systems is partrnent, but one handheld fire extinguisher containing
.!
described in this paragraph. Examples of fire-extinguishing 2.3-kg (5-lb) of carbon dioxide or 1.25-kg (2.75-lb) of e
‘. systems currently installed in. vehicles are given. Halon 1301 is provided for the crew compartment.
,,, .
7-58
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— .—
@
—.
f!9 -..
e

TABLE 7-15. US COMBAT VEHICLE FIRE SUPPfUISSION SYSTEM CHARACTERISTICS (Ref. 141)
LARGE-FIRE/ HANDHELD
EXTlNCNJISH13h DISCRIMINATION SMALL-FIRE B1T13 EXTINGUISHERS
DIYII3RM1NATION TYPE AND WEICIHT
M60 Mm Crew NA NA 1 co*
l%mily + 2.3 kg (5 lb)
Engine None 2 Shot, Mnmml NA NA None
I
MI/MIAl Crew No No HaIon 1301
MDT 2 ea. 1.25 kg
(2.75 lb)
Engine 2 Shot, Mrmual, or 2 HaIon 1301 No No No None
Automntic 3,2 kg (7 lb)
MI13APC Crew None NA
Family
Engine None I 1 Shot, Manual 1 co~ NA
2,3 kg (5 lb)
M2/M3 BFV Crew 2 HaIon 1301 Ycs No No HaIon 1301
I%nily

Engine
2,3 kg (5 lb)

1 Halon 1301
I
I NA I ‘NA INAI
2 en. 1.25 kg
(2.75 lb)
None
3.2 kg (7 lb)
M992 Crew HaIon 1301 Yes Yes Yes HaIon 1301
FAASV 44,5 kg(101b) 2 tm. 1.25 kg
or 63.2 kg (7 lb) (2.75 lb)
13ngine

NA = not applicable
---km= 2 Hnlon 1301
4,5 kg (10 lb)
NA Overhent
Wnrning
Continuity
Check
None

I
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MIL-HDBK-684 .
7-5.1.1.3 The Ml Main Battle Tank two-round rack for the MlAl, which may or may not be
The Ml Wd MIA1 MBTs (The MIA1 is shown on Figs. used-the potential hazard horn such use is described in
7-24 and 7-25.) have 4-man crews and, a re~-mounted subpars. 4-6.2.2.2 and 4-6.4.1. The mobility fuel is located o
en~ne.~l%e M 1 and M 1A 1 MBTs have most’ of the main in six rotary-molded, high-density, cross-linked polyethyl-
gun ammunition in two isolated magazines, one ‘low in .lhe ene cells. Four ‘fuel cells are located in the hull and are
hull and one in the turret bustle (See Fig. 4-29.). The ttiet armor protected.. Two of these four cells are adjacent to the
bustle magazine is divided into two or three sections, depen- crew compartment, i.e., one on each side of the driver. Fuel
dent upon the caliber of the gun. There is a three-rounti from these two cells must be pumped to one of the. cells in
ready rack below ‘the main gun breech for the. M 1 and a the engine compartment, Steel bulkheads, 25.4 mm (1. in.)
,.

t -.s..
-.s.
. . ......
,-

120-mmGun

.. I \,J
~ EngineAGT1503
(A)Top
Transmission
X-1100
4,25m 12,7mm(.50cd) Cupola
(167.5in,)
P -\. i

m
n.)

(B) Front (C)Side,

Figure ‘7-24. Line Drawing of MIAI MB~

Figure 7-25. Photograph of NHA1 MM’

,.
7-60
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MIL-HDBK-684

0,)~j
.-. thick sepamte these fuel cells iiom the .tiver. Two addi- 7-5.1.1.4 .. Bradley Fighting Vehicles M2 and M3
tional fuel cells are located in the sponson areas. AU six of The Bradley fighting vehicles (WV) are aluminum
“i’? these fuel cells are interconnected so that a hole in any one hulled and have tube-launched, 0@C311Y rracked,
.- -candraind cells down to the level of the hole. There is a wire-guided (TOW) missiles, 25-mm cartridges, and orher
hydraulic power system to drive the turret and to move the miscellaneous munitions stowed throughout the troop com-
maga2ine doors. partment. The M2A1 infantry fighting vehicle (IFV) is
The Ml and MIA] MBTs have two automatic HaIon shown on Fig. 7-26, and the M3AI cavahy fighting vehicle
1301 tire-extinguishing systems, one in the crew compart- on Fig. 7-27. ‘Ihere are two rotary-molded-nylon 6 fuel
ment and one in the engine compartment. Four dual-spec- cds, both of which are in the troop compartment.- The
trum, infrared sensors are used in each compartment The engine companment is separated from the troop compart-
crew compartment has an automatic, one-shot system, ment by a 6.35-mm (0.25 -in.) thick aluminum bulkhead.
whereas the engine compartment has a two-shot system Considerable mobility fuel is heated by the engine and
wirb amornatic detection and activation of one bottle for the returned to the fuel cell~o the upper fuel cell in the .h42
- tirst shot. If a fire rekindles, the driver can release. the sec- and M3 versions and to the-lower fuel cell in the M2Al,
ond shot by actuating an ekwrncal switch. This release will M3A1, M2A2, and M3A2 versions. The persomel heater
cause the engine to shut dowm and after a built-in time uses mobility fuel and is in the troop compartment mounted
delay, the second bottle will discharge. In addition, a man- in a recess in the upper tlel cell. A hydraulic power system
ual discharge for the first shot in the engine compartment is operates the rear ramp door. The .hydrmdic fluid reservoir,
provided for the driver at his station. An external handle, containing about 0.95 L (1 q) of fluid, is in the bilge near the
mounted on the left side of the hull, will discharge the sec- door. lhe bilge under the engine is open, i.e., not covered
ond shot without the engine being shut down. The crew with decking, but the bilge in the crew compartment is cov-
compamnent system has one 3.2-kg (7-lb) Halon 1301 bot- ered with decking. .-
tle, the engine companment system has two. ‘Ihae are two ‘Ihe BFVS M2, M3, M2A1, M3A1, M2A2, and M3A2
portable 125-kg (2.75-lb) HaIon 1301 fire extinguishers in have a single-shot AFES with manual backup in the crew
the Ml and MIAI MBTs. compartment. l%e crew compartment system uses four opti-

,’,,
f
,,,
l,,
,,,
,’
,,
o t.@ptuFusfTan%14sL(39@= ~ 25-lrunAlnmlJllMtNl,3
B0xes

-.

I
L------&~,
(B) Front (C) Sie

0 ,.’,,,
,,,,,[
~,
~
.,

Figure 7-26. M2A1 Infantry Fighting Vehicle (lF’V’)

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MIL-HDBK-684
UpperFuelTank,146L (39gal)
TOWMis$iles,10
LowerFue+jSS6L (147gal)
,

\ I [-

(A) TOP ,1 “ 2$mm Ammunition,21 Boxes

‘12.9 m
(117in.)

0.46m{y&\
–u–-l Elca
I 1. 3.91m
(154in,)
I
I
(B) Front (C) Side
,.
.: Figure 7-27. ”~Al Cavalry Fighting Vehicle (Cm)
e

cal sensors and two 2.3-kg (5-lb) bottles of Haloq 1301. The 1. Most of the munitions were removed from the crew
manual engine compamnent system has one 3.2-kg (7-lb) compartment.
bottle of Halon 1301, which is located in the crew compart- 2. The fuel cells were removed from the troop com-
ment ,next to the’ driver. There are two handheld 1.2-kg partment, and where fuel cells abutted the troop compart-
(2.75-lb) bottles of lHalon 1301in the crew compartment. ‘ ment, ‘entry of. fuel into the troop compartment -was
restricted by an aggregate bafile. Hull flash and fireball were
7-5.L%5. Advanced Survivability Test Bed Vehicle reduced by a gelled water baffle (Ref. 95).
The”Advanced SurvivabW~ Test Bed (ASTB) Task Force 3. The selectable automatic or manual fire extin-
was formed in 1986 to desi~, fabricate, and. demonstrate guisher system covering the troop compartment consisted of
alternate versions of the Bradley fighting vehicles with four optical sensors, a controller, and two 4.5-kg (lO-lb)
enhanced vehicle and crew survivability given overmatch- Halon 1301 bottles. This setup was reconfigured from the
ing threats. 130tir infamy fighting vehicle, Fig. 7-28, and BFV system by relocating sensors and bottles within the
cavalry fighting vehicle,Fig. 7-29, versions were made. - crew compartment to allow for differences in interior. con-
The ASTB had its stowed TOW rnissiles “moved to ~ “. figuration. The fixed fire extinguisher system for the engine
external magazine or placed in the bilge aid had the 25-mm’- compartment was not changed from the BFV configuration.
ammunition stowed in protected maghnes or stowed exter- 4.. The bilge ‘under the engine compartment was cov-
nally (See Fig. 4-32.). The bulk of the fuel was stowed in ered with decking, but passages were provided to allow
-external. rear cells similar to those. of the APC- M 113A3: drainage of liquids into the bilge in order to provide a safe
shown. in Fig. 4-2, with a smaller “get home” fuel cell in the collection location for spilled liquids.
engine compartment (Ref. 90). The troop compartment 5. The effectiveness of a double-walled or jacketed
heater, fueled with mobility fuel, and the hydraulic fluid res- t%el cell was explored and documented. These tests indi-
ervoir,in ‘the bilge, remained the same as in the Bradley. cated that such fuel cells will eliminate fires in the engine
The fire’ suppression system had the following passive compartment given a hit on the fuel cell (Ref. 98). “
and active features: ‘
m

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MIL-tiDBK-684

(A)
P UqOPJTw, 2Rct@
Glenwes.Rl?m. and

_—
.- ..,-
Ttlw 2 / &mmtmen13T6f4Knb
Rf?mbll.lnmrd ,1 . .25+nmAmmbMun. “ ‘

(8) Froni
FIgUIW 7-28. ASTB IFV Concept 163

ml Ammlmmn,
m ZS.mmAmmuIIUWI

1[+ - IAWS.3

TOW*2
Fk@frnbwm&i7
. ..—
,..Y-- GA-–-
Smm Ammunii
.

s
.KW2
lh@ff%Ln

p#&..!ql
.an -

(B) Fronl (C)Side

Figure 7-29. ASTB CFV Concept 165
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MIL-HDBK-684
:7-5.l.l.~ ~-Field ArtiHky Ammunition Support The FAASV supports ti,.M109 series SPH (155-mm
Vehicle M992 cannon with sep~ate-loading ammunition) and carries 90
The M992 F&WV is an aluminum-hulled vehicle that conventional projectiles, 3 Copperhead cannon-launched a
.,- ‘-:”tarries zmm-nmition for use in the M 109, 155-mm,- series of. guided projectiles or similar-sized projectiles, 99 propellant
self-propelled howitzers. The chassis 1s basically that of the charges, and 104 fuzes. (Ref. 142)
M109. The M992 has a crew of three and can cariy five pas,
- s.engers. The artillery rounds are delivered via a:conveyor to 7-5.1.1.7 Armored Reconnaissance and/or Air-
the M109. Ammunition handling within the FAASV can be borne Assault Vehicle M551 (Sheridan)
mechanically assisted” although crewme~ still must place The armored reconnaissance and/or airborne assaultvehi-
munition elements onto the conveyor belt,’ which uses cle M551, shown on Fig. 7-32, has an all-welded aluminum
hydraulic power. The layout of the ammunition and troop hull &d an all-welded steel turret with a titanium cupola.
compartment is shown on Fig.. 7-30. The ~AASV is diesel Power .is provided by a liquid-cooled Detroit diesel Model
powered and contains a fiberglass fuel cell that is located 6V53T, 598 L (158 gal) of diesel fuel are carried in two alu-
.,.. ., - within the engine compartment and has a comer, protruding-~ minum cells, one along the starboard side of the crew and
.. .’ into the ammunition and troop compartinent. A 3.175-mm engine compartments and one across the vehicle in ~the
.
‘,(O.125-in.) plate separates the fuel cell from the ammunition engine compartment and adjacent to the firewall separating
arid troop compartment. The hydraulic fluid accumulator, the two compartments. The main gun is the 152-mm gurd
,. the reservoir, and a fuel-fed heater are in the.’animu~tion launcher M81, which fires the MGM-51A Shillelagh missile
,.
,,. and @oop compartment. The auxiliary power unit (APU) is with combustible case cartridges. Combat cartridges are the
mobility fuel powered and is located above and behind the HEAT-T-MP M409, WP M41O, or canister M625A1 (bee-
,, ..’ driver in a sep~ate compartment.. ,. hive). Stowage is provided for 10 missiles and 20 car-
,’, .
The FAASV has an AFES for the ammunition and tcoop tridges. These missiles were too moisture sensitive to be
compartment that uses four optical sensors and provides used in SEA (Ref. 143), so addhional cartridges werewsu-
two shots of HaIon 1301. The halon is in four 4.5-kg (lO-lb) ally stowed in the spaces provided’ for the missiles.
,,. or six -3.2-kg (7-lb) bottles, as shown on Fig. 7-31. The The AIVAAV M551 was the first US combat vehicle to
engine compartment has thermal detectors and a two-shot have a Halon 1301 fixed fire-extinguishing system. There is
,,. fire-extinguishing system, one shot is automatic and the sec- no Iire-sensing system. The engine compartment has a man-
ond shot, mbual. .The engine compartment system has two ually activated ~S with a 1.5-kg (3.25-lb) bottle; the crew
,:, e
4.5-kg (lO-lb) bottles of Halon 1301. For ex~riences of compartment has a manually activated FFES with a 3.6-kg
,.,, ,“ FAASVS in SWA, see subpar. 7-1.2. . (8-lb) bottle. In addition, there is a 1.25-kg (2.75-lb) porta-
ble fire extinguisher in the crew compartment.

Two Extinguishers
Added for O-BottleT

I
“

... ,...

,.
Fuel’ce~l ! ‘iss!les on
‘ Top Powder I Right+iie
-, J LI d
~— Caiiiter
Projectile
Compartment )
Rack
)
.45~
20 dq Down

,,
~~
45 cteg
‘Vertical
30 deg Down
,.
20 deg

,:. Left-Side
Auxiliary 45 eg
.“. ” Canister
.Power
Compartment
Unit 2F
... . I
.,. , A =opticaIfire’sensor
..
Figure 7-30. Layout of Ammunition Compartment Sensors and Extinguisher Bottles on the FAASV

7-64
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.12

\l 6

Automtk FirEPExtirtguishing
system AFESManualDiiarge SystemtvlDS
(AFEs) Componenk

O,, :,,! ~ :,.’

crew
,,,, !, : !
1. CrewT/# Panel 13. EngineT/APanel 19. I.qad Assembly
2. OFSA 14. RemoteStaiusIndicator 20. LanyadCablePullHandle
3. OFSAWIteHarnessWl 15. ThermalDetectionSystem 21. EngineFireExlNo.2
4. MsEc 16. Ha!onDistribution
System
5. MSECWireHarnessW2 17. En@neFireExlNo.1
6. Extww Hafnessw3 18. ExtWireHarnessW4
7. Cr@ffFimExir@.1
8. cmYfitEExINO.2 WA= teslanddam
9. CrewFifeExtNo.r “Activatedby elhercrew AFESMDS
10. Cmv FireM No.4-
11. CrewFW Ex!No.5
12. crew FireEMNo. 6

Figure 7-31. FAASV AFES

Two AR/AAV M551s were hit by RPG-2s in SEA in providing protected stowage in combat vehicles for main
approximately the same location; the trajectories of the jets gun ammunition.
of these two war&ads are shown on Fig. 7-33. In the inci-
dent descrdxd in DAN 1548, the jet passed through the 7-5.1.2 Description of US Marine Corps Systems
&iver and killed him, but the jet was absorbed by materials The United States Marine .Corps (USMC) is responsible
in the rear of the crew compartment without starting a fire. for tie design and development of amphibious vehicks. ‘Ihe
In the incident described in DAN 1550, the jet hit main gun following descriptions are ftmtistted for two USMC
rounds stowed in the missile area and these rounds amphibious vehicles and the wheeled light-armored vehicle
expbded and killed all four crewmen, as described in sub (L.AV) 25.
pan 4-6.1.3 (Ref. 5). These incidents illustrate the value of

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MIL-~DBK-684

Fig Urt! 7-32. Ar&wed ~econnai&ance/Aiyborne Assault Vehicle M551

.,

! ~-.

-1

W
1-
,,-:
RPG2

(A) RpG2 tiit On AR/AAV, DAN 1548 Tc .Tan~ ~omman~er

GNR = Gunner
DVR = Dfiver
. LDR = Loader ... . .
,,

,. RPG2”-

.. .

(B) RPG2 Hit

on ARMV, DAN 1550
Reprinted with permission. Copyright @ Defense Fire Protection Association.
.,
Figure 7-33. Shaped-Charge Jet Trajectories k Two Incidents Involving AR/hV M551 in South-

,,. east Asia (Ref. 5)

I
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MIL+IDBK-684
7-!5.1.2.1 Landing Vehicle, ‘Ikacked, Personnel were four ha.lon bottles, each. containing 4.5 kg (10 lb) of
.1: (WIT) SAI Halon 1301. In addition, the engine compartment had one
,,‘,,,,
f!
;i,[
o The LandingVehicle, Tracked, Personnel (LVTP) 5A1, nozzle connected to a bottle containing 7.9 kg (17.5 lb) of
shown cm-~ig. 7-34, is no longer used by the USMC. It HaIon 1301.
is, however, still in use by the Philippine Republic. The
LVTP 5A1 is inkluded primarily because of the early 7-5.1.2.2 AssauJt Amphibian Vehicle (kiV) 7A1
work done on an AFES that was designed and tested for The assault amphibian vehicle (AAV) 7A1, shown on
but not incorporated into this vehicle. ‘fhis AFES design Fig. 7-35, is an aluminum-hulled vehicle with a- diesel
was the basis for the first US my AFES. lhe LVTP engine. An automatic Ike-sensing and suppression system
5AI is a steel-hdlecL gasoline-powered vehicle. The gas- (AFSSS) was approved for retrofit for the troop compart-
oline is carried in 12 cells, eight of which are located in men~ The Al?SSS operation was demonstrated to be accept-
sections of the bilge directly under the troop compart- able (Ref. 82) according to USMC validation test
ment. Rubber-coated fabric gasoline cells were covered procedures (Ref. 145).
with a layer of elastomer to provide abrasion resistance The AAV 7A1 has onefuel cell in the port (left) sidewall,
(Ref. 144). shown on Fig. 7-10. me vehicle has. a manual fire-extin-
lbe prirnhry threat was a beach mine with a shaped guishing system in the engine comparunen~ and mechanical
charge directed upward. A series of tests was conducted to pull handles are located both inside and outside the vehicle
demonmate how effectively the AFES could counter this at locations accessible .to the crew.. A portable 1.25-kg
threat (Ref. 96) (de~”bed in subpar. 5-2.2.3.1). The AFES (2.75-lb) HaIon 1301 the extinguisher is installed in the
used optical &e detectors, but an intrusion detector-a grid vehicle.
-- of wires placed between the hull and the fuel cells to sense l%e AFSSS has four discriminating optical sensors, an
~ jet perforation and described in subpar. 6-4.l-was also electronic controller, and three 3.2-kg (7-lb) HaIon 1301
tested. Government contractor personnel recommen&d the bales with associated wiring and plumbing. ‘Ibe sensors
intrusion detector because they had false alarm problems are Dual Spectrumm Infrared Optical Fire Sensors;
with the optical sensor system. The fire-extinguishing sys- described in par. 6-2. The electronic controller receives
tem used two nozzles to flood Halon 1301 into the troop inputs from all four sensors. If any sensor(s) detects the
~,
,!
mJfl,(,
compartment if a perforation of the hull occurred. There flash of a penetratio~ the system goes into a delay mwie

.“, . . . . .-
. .

.? ... . ..

Figure 7-34. LVTP 5A1

.-. . . .. .

Figure 7-3S. AAV 7AI

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. . . MIL’HDBK-684
periodically to recheck the situation.. OrIly. when a sensor(s) 7-5.1.3.1 -Leo@rd II Main Battle Tank
detects a fire without, any detection of the flash will extin- The West German Leopard II MBT uses the Deugram
guishers activate. (Deutsche Graviner) fire-extinguishing system. The crew m
... ‘.,: “’ This system uses solenoid valves that have manual compqtment haj a two-shot automatic fire-extinguishing
release levers which are connected to mec~cal’ pull system using four IR sensors and four 3.2-kg (7-lb) Halon
cables. Deflector nozzles are used on two bottles; and a dis- 1301 bottles. The second shot is available five seconds after
charge tube is used on the third; the halon wil~~spray in the “’ tie ~t shot has been used. The controller has three select-
directions. indicated on Fig. 7-11. The electrical wiring is able modes of operation In Mode O the system is off. In
sealed to protect it from salt fog. Mode I the system automatically operates when two or
,’ more sensors simultaneously signal afire (peacetime mode).
7-5.1.2.3 Light-Armored Vehicle (~AV~25 ~ In Mode II the system automatically actuates when one sen-
The USMC is acquiring the LAV 25, illustrated on Fig. sor signals a fire (wartime mode). The one-shot fire-extin-
7-36, from General Motors of Canada. This ve~cle is guishing system in the engine compartment has a
equipped with manual fixed fire-extinguishing systems in Firewirem thermal detector, an electric-manual controller,
both the crew and engine compartments. It originally had a and one or more 1.6-kg (3.5-lb) bottles of HaIon 1211:-
single-shot, two-bottle system fiumished by Walter Kidde, The Leopard system requirements include the following
but the system is now fabricated by Canadiaq. subcontrac- items:
,. tors. Each 6.8-L (418-in.3) aluminum bottle cop@ins 4.1 kg ‘, 1. ‘l%e fire-extinguishing system must recognize a fuel
(9 lb) -of Halon 1301 pressurized to 4.1 MPa (600 psi). or hydraulic fire being initiated, signal the fire, and extin-
,.. - ~ese bottles are actuated by axiy one ,of three cable pulls, guish’it before personnel suffer irreversible injury.
i.e., from the driver’s location, “the troop coti~~ent, or 2. The combat value of the vehicle cannot be
the vehicle exterior. Both bottles discharge wi~ a single degraded.
pull. 3. Effectiveness of the fire-extinguishing system can-
‘me USMC is currently considering ret.iofitting the LAV not be degraded by the nuclear, biological, and chemical
25 to use a crew compartment system similar to that used ifi (NBC) system or by no~al vehicle ventilation.
.!
tie AW 7AI. $.” When the vehicle suffers a hit that causes fuel, oil,
or hydraulic fluid to burn, the pressures generated are not to
.7-5.1.3 Description of Foreign Systems’ cause” ear darnage and the temperatures are not to cause
e
Some information is provided on the’ fie protection sys- greater &an fixst-degree burns.
,, tems in foreign combat vehicles, which include the West” 5. The total time from an explosive atmosphere form-
German Leopard II MBT, the English Chief$in MBT, ing to total extinguishment shall be less than 150 ms.
Israeli combat vehicles, and Russian MBTs. The Canadian Leopard Cl MBT, armored reconnaissance

‘-
I.
,.

,,.
I
,,
~,’ ,.’.
.

I@ure 7-36. USMC Light-Ar~ored Vehicles: Lef~ LAV 25 With 25-Inm Chain Gun; Right, Logis-
tics Variant

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MIL-HDBK-684
vehicle (ARV), AVLB, and armored enginesr vehicle
,1~., (~ hve the Spectronix automatic lire-ext.inguislthg
oif system described in subpar. 7-5.1.3.3.

7-S.1.3.2 British Army Main Battle Tanks

lhe Chieftainis the British Army MBT fielded in 1963.
The Challenger I is the MBT fielded in 1983 and used in
Kuwait in 1991. T%e Challenger II is the upgraded MBT
scheduled to replace the remaining Chieftains and Chal-
lenger I%.
The ChieRain MBT bas the Graviner Firewire~ thermal
system and Halon 1211 extinguisher bottles for fire protec-
tion of the engine compartment only, and it has water-jack-
ete~ fiberglass magazines for the main gun ammunition. (A)CmwCom@ment System . .
The fuel cells are plastic* cells in metal compartments. The ..-
turret power is electric, and there is no automatic or manual
fixed fire-extinguishing system in the crew compartment.
The Challenger MBT also uses the Fwwirem continuous
thermal wire &tection system for the engine compartment
with Halon 1211, but it has eliminated the water-jacketed
magazines for the main gun ammunition.- Rigid, rotary-
molded* fiel cells are used (Ref. 147). Turret power is elec-
tric, and there is no fixed fire-extinguishing system in the
crew compartment. Extended range fuel drums can be canti-
levered off the swr of the Challenger II.

7-5.L33 kaeii Combat Vehieles

:,;,
,
i,,:,!,
i,
,,,;,!~~,,,,
,, Almost all Israeli combat vehicles are protected &om fire
o of bydmcarbon liquids. This protection includes an AFES (B)-e COmtwtmmtsystem
for the engine and crew compartments, as shown on Fig. Courtesy of Spectrex,Inc., Cedar Grove. NJ
7-37. This fixtinguishing system is also used in the
Canadian Leopard (2I MBZ the Spanish AMX-30 MBT and Figure 7-37. Spectronix* Automatic Fire-Ex-
MI09 SP13; the Greek Leonides MB~ the Austrian M60 tinguishing System in the MBTs of Several
MBT, M109 SPH, and Speyr 4K APC and the Issael,i M60 NATO Countries and the Merkava MBT..
series MBTs upgraded Centurion MBT, and Merkavas
Tbe crew companment fire-extinguishing system, 148). The control unit has indicator lights for eactt of the
depicted on F~g..7-37(A), is capable of detecting and sup- four bottles that tight when the bottle is discharged. Lights
pressing all types of fires, small or large, slow or rapid also indicate detection of a system fault and power “on”.
growth, limited in area or widely growing, as weu as fhel There is a selector switch for normal or combat modes of
explosions, in combat or training. This system is designed operation. BITE checks the lamps and the system. The nor-
to minimize the pressure increase resulting fkom an explo- mal mode of operation is that fire detection must be by at
sion to not more than 101 kpa (one atmosphere) and should least two sensors. If the time between the two sensor detec-
prevent second-degree burns to uncovered skin. The optical. tions is less than 30 ms, the system will actuate two bottles.
detecto~ three or mom are dual spectrum, i.e., W and R. If the time is greater than 30 ms, only one bottle will be
Use of the W, particularly in the spectral region of 0.16 to actuated. In the combat mode of operation, a tire signal
0.26 prm permits dismimm. ation between most false stimuli horn one or more sensors causes activation of two bottles.
and a hydrocarbon fire. A ths response time from fire The system resets itself to repeat the automatic modes of
exposm to extinguishant valve actuation is desired (Ref. opemtion in five seconds. This system can also be operated
manually (Ref. 149) by using switches that generate their
- rigid fuet dk W t’OttUy-ttlOkk&CrOSS-hkd Pdydtyh
own current. The bottles contain HaIon 1301, and the size is
enc. These cells contain Ptomelm molded poIyami& fiber explo-
sion suppression medium and me surrounded by Atotnelm molded selected to tit the vehicle.
. . polyamide fiber tire-retaniant materials. Tltese fuel cds, tbe ‘l’he engine compartment system, as shown on Fig.
,,,ii,,iRem- and Atornel=. and the rotary-moldetLcross-linkedpoly-
‘;‘q ethylene water reservoirs for the Challenger II are all made in *use of product name does not constitute endorsement by the Gov-
o England (Ref. 146). ernment.

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MIL-~DBlG6$4
7-37(B), detects overheating anwor fire by using a continu- 7-5.1.3.4 Russian Tanks
OUS-thermal detector of the thermistor. type. The logic and In Russia fire-extinguishing equipment is considered
control box monitors the sensor and signals an overheat ano~er means of tank defense (Ref. 152). During World o
zonditio~(a flickering alarm light).’ When ~e signal is War 11 hand-pumped fire extinguishers were used, but they
strong enough, the controller signals fire (steady on” alarm were only slightly effective. Modem Russian tanks use
light) and activates one of the two Hqlon 1301 ,bottles. The fixed, fire-extinguishing systems consisting of a controller,
second Halon 1301 bottle is for manual actpation (Ref, distribution system, and several extinguisher bottles that are
,,
140). either manually or automatically controlled or both.
The Merkava—Hebrew for war chariot-M~T has been
designed with survivability of the crew in mind. ~s design .7-5.1 .3.4.1 T-54 lWBT
includes placement of the engine forward and provision for The T-54 M13T was the first post-World War 11tank to be
ingress and egress low in the rear, and.ti all electric turret produced by the Russians; its prototype was built in 1945
(Ref. 150). The Merkava III has rear~moimted; fuel cells (Ref 153). This vehicle has been upgraded while in use.
similar to those shown on Fig. 4-2, Wd it appe~s to have The” fire-extinguishing Iechnique used in the .T-54 is to
the ASTB type of spacershffles between the fiel cells and ~~ smo$er the fire, with carbon dioxide. Smothering- internal
the hull (Ref. 151), which provide a rapid drain overboard fires would be effective only if the vehicle were sealed to
when the fuel cell is. perforated. These fuel cells provide prevent the intake of fresh air; therefore, an essential ele-
protection to the ammunition magafie, -which iS installed ment of extinguishing the fire is to. close the air intakes,
low and at the rea of the hull. The 120-mm rounds are indi~ which has to be done manually.
vidually stowed in thermally. insulated, antifra~cide con; Ifkje Russian T-34 has a manually activated, fixed fire-
tainers, which reduce the potential ..for cook-off if a fire extinguishing system that can selectively inject carbon
.,
‘starts (Ref. 150).
9

““ ‘~2 Uuu’
3
1 Carbon DioxideQlinders 6 Fire Sensors .
2 BatteryProtectionUnit 7 Nozzle
,3 Discharge Mechanism Button 8 AutomaticFire ExtinguisherSelector
4 Signal Panel 9 Pipelines
5 Sound Signal (Fire Alarm) a
Figure 7-38. Fixed Fire-Extinguishing System for T-54 MBT (Ref. 154)
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MIL-HDBK-684
dioxide- into. either. the engine compartment or the crew tle discharge into both manifolds simultaneously, but to
1::: compartment (Ref. 154). This FFES, shown on Fig. 7-38, obtain sufficient carbon dioxide in both compartments, a
has three bottles, each containing 1.8 to 2.0 kg of carbon second bottle must be simultaneously activated.
dioxide, lmted in the rear right comer of the crew com- The T-54 MBT also has a portable fire extinguisher con-
partment and adjacent to the engine compartment Each taining 1.5 kg of carbon dioxide that is located adjacent to
bottle has a dual-outlet valve with a squib controlling the three FFES bottles.
each outlet that can be initiated separately or together in
order to inject “carbon dioxide into the engine compart- 7-5.1.3.4.2 T-55 lklBT
ment or the crew compartment or botb simultaneous] y. The T-55 was developed in the 1950s to operate otrther-
All three bottIes are phunbed to two manifolds. One monuclear battlefields (Ref. 155) and was introduced in
manifo~d goes to the engine compartment and the other 1958. (he of the new features built into the T-55 was a way
manifold, to the crew compartment. Each manifold has to seal the vehicle, which, with a positive internal air pres-
four nozzle outlets. ‘l%e FFES has a selector box that sure, prevented entry of fallout into the vehicIe. The fire-ex-
controls botb the squib(s) to be initiated (hence the tom- . tinguishing technique was still to smother the fire. Since
partment to be flooded with carbon dioxide) and the bot- sealing the vehicle was- still. an essential element -of the
- tle to be discharged. This system uses battery power smothering technique, the automated sealing features of the
throughout to operate the sensing and control devices. fallout protection system were also used by the fire-extin-
The sensors used with this system are heat-activated guishing system.
switches. The sensing element is a cupped diaphragm (prob- ‘he fixed lkexdnguishing system of the T-55 MBT is
akdy bimetallic) that straightens when heated and closes the shown on Fig. 7-39. This FFES uses the same principles as
contacts of a switch. .When a cloud of carbon dioxide -. that .of rhe T-54, but much of the hardware has been
engulfs one of these fire sensors, the diaphragm snaps back changed. l%e fue extinguishant bottles, valves, and mani-
and resets the sensor. There are four of these tire sensors folding are the same, but they have been relocated within
located in the crew compartment and four in the engine the engine compartmen~ The extinguishant has been
compartment. These fm sensors are wired to a control panel changed from carbon dioxide to a liquid halon CH3CH2Br

(visual
akmn)
at the driver’s location. The control panel has a signal light (ethylbromide or Halon 2001) pressurized by carbon diox-

o
for each compartmen~ which is energized ide. hstead of four nozzles within each compartrnen~ there
~~~ ““’when a compamnent fire sensor activates. ‘he engine detec- are nine nozzles in the crew compartment and six nozzles in
tor subsystem also has an audible alarm. There is a button the engine compartment. Some of these nozzles are directed
switch beneath each signal light that the driver must press to at specific fire threats; the rest are used for general compart-
activate the FFES in the compartment in which the fire was mental flooding. ‘Ike are stiIl four sensors in each com-
&tected. patttnen~ but the sensor has changed from the bimetallic
When the b is in the engine compartment the driver diaphragm switch to a 15-thermocouple thermopile
can actuate the FFES. The driver must first stop the engine (described in subpar. 6-3.3.2). The thermopile generates its
-. so that the carbon dioxide will not be expend, also the tank . own current and thus negates the need for battery power in
cmmnander and the hader must tum off the. ventilation the-sensor circuits. The control logicTemains the same, and
fires. The crew is instructed to remain within the tank and the master control is stil~ located at the driver location The
p- with their duties. selector box of the T-54, however, has been incorporated
- When the fire is in the crew compartmen~ the dtiver and into the dxiver’s panel, and the control signals are now
the loader mustA press a separate button located at his transmitted by relays to reduce the current flowing through
station. l%e tank commander and the loader must open the the cables and to permit the incorporation of needed relays
hatches. After the fire is extinguished tie tank commander into the control system rather than depending upon the crew.
and loader stan the ventilation fans, and the gunner opens AIl the vents are .Jouvers, and fan circuits, which had to be
the escape hatch. If permissible, the tank crew exits the tank closed or turned off by han~ are automated by using the
and leaves the fans operating for three to live minutes. If fallout ventilation control circuitry. ‘I%e switch used by the
exiting the tank is not possible, the crew members remain loader in the T-54 to provide an auxiliary means to actuate
within the tank and don their gas masks. (Gas masks wilt t12ecrew compartment FIRS was relocated so that either the
not help against carbon dioxide but will he~p against smoke tank commander or the gunner could operate it. “fhere -is no
and many of the other producrs of combustion.) mention of an audible alarm for the FFES control system in
When the driver or loader presses and releases his actua- the engine compartment The master control box has a tog-
tion button, the selector indexes the next bottle. This bottle gle switch that can select automatic or manual control. Ail

,,jv
0
“fi
may then be actuated. Each bottle requires 40 to 50s to dis-
charge fully. If there are fires in both compartments, the.
crewmen should start the flow of carbon dioxide into one
components for the FFES and the fallout protection system
are color coded red.
‘he fire-extinguishing system for the T-55 is also used in
manifold from one bottle and then start the fIow from later Russian MBTs.
another bottle into the other manifold. They can have a bot-
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MiL-~DBK-684

,,

1 Fuel Tank”and Ammunition Rack A Master Control Box Cnnc.nr

UGIlaw
‘
2 Ammunition Rack and Fuel Tank Ventilator Control Box
D
3 Fuel Tank ~~ ‘~ Driver% Relay Box
4 Transfer Case D Radiometric Protection Unit
5 Engine E Distribution Relay Box Nozzle
6 Transmission ,F Push Button x
7 Brake and Steering Units G Fire Extinguisher Bottles
8 Fuel Filter H Manifold

Figim 7-39. Fire-Extinguishing System for the T-55 Tank (Ref. 155)

7-5.1.3.4.3 Other used in handheld extinguishers by Russian tank crews in

The RussiW fire extinguishant of choice has changed World War II. H works. The water spray rapidly cools the
over the years. In World War II it was water. In the T-34 car- combusting materials. The carbon dioxide lowers the level
bon dioxide was used, although it may. have” been in the . of oxygen present in the combustion area, and the endother- 0
form of carbonic acid (H2C03). In the T-54 carbon dioxide. rnic reaction absorbs some of the heat being generated by
,. was used. In the T-55 and T-62; MBTs “Halon 2001 the tire. Further, @e spray is a good way to project the
. water, penetrate the flames, and impinge upon the burning
(CH@-12Br) pressurized wjth carbon dioxide was used in
the FFES. In the later tanks, T-64,, T-72, and T-80, Ha.lon matter. Also the development costs of the device were nil
. . . 2402 (C2Br#4) is used, but the pressurizing gas is not because seltzer bottles were invented prior to World War I.
known (Ref. 156). “ ~ A similar device, with replacement caxbon dioxide car-”
Carbonic acid. (H2C03) is created when carbon dioxide is tridges, is currently being used by airlines to extinguish fires
injected into water “within a “closed container. ~ contents in passenger aircraft. The -appeal of this device is that the
of the container will be a solution of cmbonic acid in water, bottle is not pressurized until used. First, the carbon dioxide
and the ullage. will contain both carbon ,dioxide. and water cartridge is screwed into the holder. This action punctures
vapor. The ~gher the pres’sure within the container and the the seal at the top of the cartridge and thus injects the carbon
~eater the quantity of carbon” dioxide injected, the higher dioxide into the water. Then the nozzle is pointed toward the
the carbonic acid concentration. When this liquid solution fire, and the handle is depressed to spray the extinguishant
flows tkom the bottle through a nozzle into a much larger on the fire. -
space, the carbon dioxide bubbles out of the liq~d, and the Russian vehicles make extensive use of exteimd he]
liquid jet rapidly becomes a spray. The conversion of cells: This design provides a passive means of fire protec-
H2C03 into watek and carbon dioxide is an endothermic tion, ”particularly since these external fuel cells are often
‘. reaction. The heat required for the conversion is calculated simple drums that provide enough fuel to reach the batt~e
‘!

by. using Eq. 7.-3 and properties of the compounds. From area and can then be jettisoned when the vehicle -goes into
Ref. 9, for H2C03, MW= 62.03 g/mol and Hf = -699.65 W/ combat. Later Russian tanks cantilever these fuel cells off
,’ rnofi for H20 in liquid form, i’kfW= 18.0153 ghol and Eli = the re~, as shown on Fig.. 7-40, to preclude leakage due to
-285.83 kJ/mol; and for COZ in gaseous form, ‘MJV= 44.01 gravity onto the rear deck of the tank.
~d Hf = -393.52 kJ/mol. One gr~ of H2C03 fo~s 0.29 g Another passive fire protection technique used by the
of water and 0.71 g of carbon dioxide. Substituting into Eq. Russians is to stow some of the main gun ammunition in
:. 7-3 shows that Q is 330 J..Thk pressurized ctibonic-acid- racks immersed within an internal fuel tank. This apparently
a
water solution is known colloquially as “fizz water”, “seh- does not work we[l, as k described in subpar. 4-6.2.1.
zer water”, or “soda water”. It was the fire extinguishant The Russian T-72 MBT, which mounts a 125-mm smooth

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. -:-

Figure 7-40. Russian T-55M MBTs Showing Jettismable Fuel Drums

bore gun that &es separateAoading ammunition, carries 22 are protected are the incendiary buile~ the high-velocity
complete rounds in the autoloader carousel, which is low in shell fragmenq and the small high-explosive shell. The
the vehicle, and another 17 projectiles and 17 propellant threat with which most Western aircmft are designed to
charge% Of these propellant charges five are located in the cope is the Russian 23-mm HEIT projectile used. by the
nmet (one in from of and two behind the commander’s seat ground-t-air automatic cannon. Protective concepts
and one in front of and one behind the gunner’s seat), and include
. . - twelve propellant charges are locatd in the hull (one on the 1. Fuel cell ullage fillers
right-band sidewall, three in the tint mclL and eight in the 2. Inerting systems for fuel cell uIlages -
center rack). Experiences in 1982 in Lebanon and in 1991 in 3. Self-seahg fuel cells
SWA have shown that hits on the T-72 almost always p- 4. Fillers for @ bays or void areas adjacent to fuel
duce catastrophic ammunition fires (Ref. 157). cells
‘l’he Russians provide tire-extinguishing systems for their 5. Powdered fire extinguishant panels
1, armored personnel carriers aod fighting vehicles similar to 6. Active fire-extinguishing systems.
iti~ those for their tank systems. McCormick et al reviewed rhese aircmft fire survivability
o
The Russians’ use of slow-response fire detectors, slow techniques and etiuated their potential for use in combat
total flooding systems, and less than crew-friendly agents vehicles (Ref. 121). Of the first five protective concepts
indicates their approach is to protect the vehicle, not neces- listed, only powder-filled fire extinguishant panels were rec-
sarily the crew. Their current doctrine, however, does spec- ommended for use in combat vehicles.
ifj that the crews should evacuate the tanks once the crew
compartment fire-extinguishing system is activated. Also 7.52.1 Ullage Filler Materials. .-, .
the fire-extinguishing system shuts down the engine when Of greatconcern for aircmft is the fact ~at under some
the system is activated. conditions the fuel vapors can form an explosive mixture
with air in the space over the fuel in fuel cells. If air and an
7-5.2 AIRCRAFT ignition source are introduced into that space, which is the
Ingeneral, the threats faced by ground combat vehicles tdlage, the fuel-vapor-air mixture can explode and cause
differ greatly from those faced by aircmft because ground structural damage. To avoid this, reticulated foam (Ref. 118)
combat vehicles can be made mttch sturdier. Some aircraft was fully packed into the fuel cells. bter voids up to 30%
smvivability enhancement concepts are directly applicable we~ left in which explosions could occur without disas-
to ground combat vehicles, but some are inappropriate trous results to the fuel cells (Ref. 160). Currently, schemes
tecause of the heavier conshuction. include gross voided configurations in which up to 8070
M excellent dissertation on the history and current stattis voidbg is left-the foam is located only in the top of the
of active fire-extinguishing systems for airmaft was given cell. Reticulated foam initially had a problem of deteriorat-
by Hillman (Ref. 158). Hillman described the development ing, but that has been solved (Ref. 161).
of the active systems that preceded those for armored vehi- In the United Kingdom a nylon material maL called
CICS.A study in which both active and passive systems were Promelm, is manufWured for the same function that reticu.
evaluated to detenn.ine their ability to protect dry bays was Iated foam Prforms in the US (Ref. 162). In Canti an
described by LeBlanc (Ref. 159). LeBlanc compared an aluminum foil batting, called Explosafe@, was developed
active Halon 1301 system to powder panels and to filler (Ref. 163). All three of these rnaterids perform the task
‘d:
,f’$~ foam. desim~ i.e., they prevent ul.lage explosions when used
o Aircmft use a mnnber of passiveand active fire suppres- properiy.
sion techniques. llw primary threats against which aimraft Ullage explosions are of much greater concern in aircraft

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NIIL-HDBK-684
than in. ground vehicles. Aircraft fuel cells are proportion- A self-seabg..fuel cell .rxmserves fuel that would other-
ally larger than those of combat vehicles, and &e aircraft wise’ leak out, which would leave less fuel for mobility.
fuel cells and structures are of much lighter construction. Crashworthy fuel cells were developed to prevent the gross a
The*xtemal, filament-wound fuel cells of-aircr~ can with- spillage of fuel when aircraft, particular] y helicopters, crash.
stand ullage explosions. Fuel cells of combat vehicles can Such crashes often resulted in fuel fires that killed personnel
also be made strong enough to withstand the ullage explo- who otherwise might have survived. The use of crashworthy
sions. cells saves those lives. Combat helicopters use crashworthy,
self-sealing fuel cells. A crashworthy construction usually
‘7-5.2.2 haling Systems for the UUage withs_@nds the -smaller- threats, such as 7.62-, . 121Z-; and
Another means of inerting fuel cell ullages is .to “introduce 14.5-mm bullets, better than simple self-sealing construc-
a material in gaseous form that will render the ullage explo- tions;
sion-proof by making it too fuel poor or too he] rich for In ~e United States there are three military specifications
ignition. The first concept was to in~oduce an inert gas, for elastomeric fuel cells used in aircraft:
either carbon dioxide or nitrogen, into the ullage. This 1. MIL-T-6396 (Ref. 165) applies to internal, nonself-
worked, but. a bottle system, which added weight to. the sealing fuel cells.” -- - ,-. ::..
vehicle, was tieeded. The second concept was to heat some 2. MIL-T-5578 (Ref. 166) applies to self-sealing and
fuel to vaporization so that the ullage became too fuel rich partially self-sealing fuel cells:
for ignition. This system introduced a potentially dangerous 3. MILT-27422 (Ref. .117) applies to-self-sealing and
item, the heater, into the fuel cell, and the too-rich ullage nonself-sealing crash-resistant fuel cells.
could be a danger to the aircraft when the fuel cell was per- A crashworthy fuel cell full of water will not rupture
. forated. The next concept was to.obtain nitrogen-rich air by when dropped from a height of 19.81 m (65 ft) onto a flat
removing oxygen through membranes. This would save @e- concrete surface. Crashworthy fuel cells were first made for
weight of bottles. This concept worked, but the filters could use in racing cars.
not obtain nitrogen-rich air fast enough to follow rapid air- A self-sealing cell will seal to the point of merely weep-
craft altitude changes. A fourth scheme was to add HaIon ing a test fluid after being penetrated by the design threat.
1301 to the fuel to inert the ullage. This also works. Further, This seal must be made wi~n 2 tin of the bullet impact.
the Halon 1301.-remaining in the fuei has been found to There are several conditions under which a seal is- not
clean carbon deposits out of the combustor ~d engine. expected:
e
McCormick et d (Ref. 121) did not recommend the use 1. When the impact occurs within 76.2 mm (3 in.) of a
of any ullage-inerting concept, nor does the author of this comer
handbook. Fuel cells for ground combat vehicles can be 2. When the impact occurs on or within 50.8 mm (2
made strong enough to resist ullage explosions ,through ~e in.) of a metallic or nonmetallic item installed, in the cell
‘structural strengh of metal cells, the “stmctur~ support of wall
plastic cells, or both. It is still advisable to i~orporate a 3. When coring, i.e., physical removal .of some of. the
pressure-relief feature into the cell. rubber, occurs
4. When the projectile “slices” (makes a long cut) the
7-5.2.3 SeIf-Sealing Fuel Cells fiel cell
Themain reliance for eliminating fires in combat aircraft 5. When metallic pieces from the aircraft or the pro-
is upon. passive suppression techniques rather than upon jectile we lodged in the self-sealing construction
llre:extinguishing systems. Thus self-sealing fuel cells were 6. When two or more perforations intersect.
used, as noted by General Ridgeway in 1945 (Ref. 164). In Shaped-charge jets are known to core conventional self-
“m airborne attack across the Rhine in 1945, the US 17th sealing constructions (Refs. 112 and 116).
Airborne Division of the XVIII Airborne Corps lost 19 of A” preactivated self-sealing construction was -xlemon-
72 C-46S primarily by fire~these aircrti, did not have self- strated that provided a means to seal in most of the cases
sealing fuel cells. (Mly 13 of 476 C-47S were lost. The just discussed (Refs. 167 and 168). However, this constmc-
much better loss rate of the. C-47S could not be attributed tion has not yet been perfected for production (Ref. 169),
solely to the newly installed self-sealing fuel cells. There nor has it been tested against a shaped-charge perforation.
was such a graphic difference, however, in the response of
these two aircraft to flak-hits; observers, includng General 7-5.2.4 Dry Bay and Void Space Fillers
Ridgeway, saw too many C-46S burst into flames to risk Fuel does not bum well within a fuel cell, but it can burn
pwatroopers in them again. For future drops ~dgeway very well in a ~ bay or void space adjacent to a fuel cell if
decreed that the C-46S were to be reserved for resupply mis- the fuel cell is penetrated. To prevent such dry bay or void
sions and that the paratroops were to drop from CL47S. The space combustion, either the void space is filled with a non-
self-sealing fuel cells in the C-47S made’ those aircraft much combustible material or a layer of this material is placed a
less vulnerable to ground antiaircraft fire than the C-46S. adjacent to the @el cell in the dry bay.

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MIL-HDBK-684
Such a void space filler is rigid polyurethane ballistic

o
I,f, foam which was first developed
““if 170) and is now produced
by NASA-kes
commercially. Another
(Ref.
void
1+ EBW EkdtiC leads

space IiUer is Atomelm, which is a fiber mat similar to

Promelm (Ref. 171).
Some rigid foam used to buffer plastic fuel cells in two -EBW
tests using small shaped charges, 81-mm M28A2 warheads,
End Cap

F
did not appear to have a beneficial effect after the shaped-
charge jet perforation (Ref. 112). MDC Propellant

\
Cord Fuse
7-5.2.5 Powdered Fire Extinguishant ParteIs
t%@(@( Ml
Powder packs, fire-extinguishant-filled panels, were

1’
developed to extinguish aircmft fires (Ref. 105). These are Copper Seal
discussed in subpar. 7-3.2.2
Inner Liner
withdrawal Plug
7-5.2.6 Fn-Exthguishing Systems
One of the first tasks for AFESS is to detect incipient
explosions within the dlage of a fiel celI and inject an
I #PressureBleed
extingpishant (Ref. 172). This task was not fully accom-
plished with the earlier systems because of response
requirements.
%rkedbnnifi (Ref. 85) developed a reactive explosion
suppression system for use in the ullage of an aircmft fuel
cell ‘I%& system senses the detonation of a projectile and
injects water in mist fixrn to inert the ullage within approxi-
l\T \Transducw Port

\ Pressure Transdmr
mately 10 ms. The key element of this device is the disper- Ftire
sion tube, shown on Fig. 7-41. This tube contains the
,Ir” extinguishan~ i.e-, water with calcium chloride freeze point \ Copper Seal
0 suppresanL rmd a linear solid gun propellant explosive
charge. Upon sensing a strong burst of ligh~ the exploding
bridgewire (EBW) is initiate~ and this initiation in turn ini-
tiates a mild detonating cord (MIX) fuse, which in turn ini-
‘/ Spacer Sleeve

IWzle Washers
tiates the propellant cord and presutizes the dispersion
tube. The pressurized extinguishant forces the suppressant
bladder to shear at the discharge orifices, which are located
K Inner Liner

}.-suppresant Bladder
at several locations along the tube, and thus permits the
extinguishant to flow into the tdlage. The pressurizing pm
b isehartte Pasaaae
gi
.
‘orifice
pellant products of combustion are confined within the dis-
persion tube by the bladder, as shown on Fig. 7-42, because FPrupelktrlt Cad
the pressurization is not sufkient to rupture the bladder a
second time after ejection of the extinguishant.
preasionCap
The fire-extinguishing systems, both automatic and man-
. ud currently used in aimraft are similar. to those used in >@mpm*m Bo!ts
combat vehicles.

7-5.2.7 Fi-Resistant Fuels and Hydraulic Fluids

Fro-resistant fueIs (FRF) were first developed to prevent
catastrophic fires in akcraft after crashes. The development Figure 7-41. Explosive Dispersion Tube Sche- ~
efforts employed both an emulsit%d fuel and an antimisting snatic (Ref. 85)
fueL ‘Ihe antimisting fuel was also tested for ballistic
impacts (Ref. 173). No fire-resistant fiels are in use in six tests, and three of the firs wem sustained. The tests of
either aim-aft or ground combat vehicles. In two series of JP-5 with 0.1% AM-1 had two fires in two tests, and one fire
was sustained. The tests of JP-5 with 0.2~o AM-1 had three
tests aircmft using neat 3P-5 or JP-5 containing 0.3, 0.2, or
0.1 % of AM-1 * antimist additive were hit by 23-mm APT-T fires in four tests, and none of the fires were sustained. The
or HEIT projectiles. The tests of neat JP-5 had five fires in %s antimist additive was a product of Conoco, BartksviUe, OK.

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I I
h<sch~ge Oriice
(A) DispersionTube -
-PropellantCord __ Norzie Washer Rim --

,.

Figure 7-42. Dispersion Tube Madder Functioning (Ref. 85)

a
tests of JP-5 with .0.3% AM-1 had three fires in eight tests, a combat vehicle., Other concepts are being -considered but
and none of the fires were sustained. (Ref. 174) In a series have not shown applicability yet.
of seven tests lightweight, single-wall, ground combat vehi- Fuel cell ullage filler materials have been tested but have
cle fuel cells containing neat DF-2 or a water-DF-2 emul- not yet proven they effectively enhance combat vehicle sur-
sion-type FRJ? were impacted .by BRL precision 8 l-mm . viability because ground vehicles are subject. to dwect. hits
shaped-charge’ jets. Three tests with neat DF-2 all resulted by shaped-charge warheads and by much larger caliber pro-
in sustained fires. The tests of FRF had two ‘fires in four .. .. jectiles than aircraft are. See subpim 7-3.2.9.3. The same is
tests, and none of the fries were sustained:” All seven tests @ue for other ullage-inerting concepts. It has been demon-
produced large fireballs. (Ref. ‘175) Thus tests of fire-resis-. strated that much of the impedimenta. carried in combat
tant fiel in both aircraft and armored vehicle applications vehicles can be used effectively as void space fillers (Ref.
indicate that fire-resistant fuels can reduce the probability of 95). Small arms ammunition, water, rations, and clo~ng
a sustained fire but will not eliminate fireballs. are included.
Fire-resistant hydraulic fluids were considered duting Conventional. self-sealing fhel cells are probably not
competitions for the TFX ~lane, which became. the F-111:’.’ “” appropriate for combat vehicles... Shaped-charge. jets- core
More recent development of fire-resistant and nonflamma- - such material, -and sharp-edged KE penetrators- or span
ble hydraulic fluids is described in “subpais: 3-3.1- and 3-3.2, could do the-same. Preactivated sealant constructions have
respectively. not yet been developed to the point that they are effective
against these threats.
7-5.2.8 Adapting Aircraft Fire Pr~ventiorn Con- Fjre-resistant fiels and nonflammable hydraulic fluids
cepts to Combat Vehicles have been considered for use in combat vehicles. The fuel
At least two aircraft he prevention concepts.have already would require considerable additional logistic efforts with-
been adapted to combat vehicles. These are the AFES an$ out an eq~valent increase in s’in-vivability. Noncombustible
the powdered fire extingtishant p~el. The reactive expIo- ~. hydraulic fluid, discussed in detail in subrmr.
. 3-3.2. will cer-
sion suppression system described in s’ubpar. 7-5.2.6 shows tainly be a candidate for use in future combat vehicles.
potential as a fire extinguisher in the engine compartment of
.,.

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7-5.3 SHIPS . 1. Redesign of munitions. to make cook-off in a pool

}!,
:! Navy ships have always had a major problem with fire. In fire more difficult
0
‘[‘;; the days of sailing ships a ship with tarred rigging, sails, 2. Insulation of Halon 1301 systems and heat and
and wooden masts and spars mounted on a dxy wooden smoke alamns in avionics spaces
structure with black powder at each gun were pyres await- 3. Installation of sprinkler systems and fire alarms
ing a match. Even with the advent of steam power and iron around high-value spaces such as the combat information
hulls, navy ships stiJI had a major iire problem. In 1915 center or in combustible storage spaces such as the storage
when the Germans lost the battlecruiser Bhtecher, they space for aircraft tires
learned thar the magazines of a ship must be better pro- 4. Use of flame arrestors in cableways through bulk-
tected. In 1916 the British learned the same lesson at Jutland heads
when they the lost the battlecruisers HMS hwincifde, HMS 5. Inspection of aircraft carriem by fire-fighting assis-
Queen Mag, and HMS Indejiznjpble, and ahnost lost the tance teams.
HMS fiorI* due to explosions in the propellant path fim The improvements for naval ships in general include the
magazine to gun. The survivability enhancement concept following:
used by the British was to place mbberized curtains along 1. Luminescent markers for egress routes to weather
the propellant path so that when the propellant was ignited decks
somewhere along the p~ the fire or explosion would not 2. Freshwater systems to compartments containing
travel to the magazine. The U.S. now uses a similar concept critical electronic equipment that saltwater would damage
in the Ml MBT except that we use a sliding door to prevent seriously
the products of explosion from entering the crew compart- 3. Removal of unnecessary furnishings and other com-
- ment and provide a blowout panel to vent tie resultant qua- bustibles from ships
si-static pressure to the atmosphere. 4. Establishment of standards for fire spread capability
In general, most of the facets of fighting fires aboard a of packaging materials
. ship differ from those in a combat vehicle. FiiL ships have 5. Installation of sprinMeL systems for storage spaces
ready access to copious qutities of the most effective containing high-value supply items in combustible packag-
extinguishant-water. All the ship needs is a pump and ing
power for that pump to get mom than enough seawater to 6. Provision of lockers for overnight storage of in-use
w ~~ extinguish shipboard fires, although it is not always possible flammable Iiquids
o to get the water where it is needed quickly enough. Second, 7. Protection of aluminum superstmcture with refrac-
ships are larger and have many occupied compartments tory felt insulation
rather than the one occupied compartment of a combat vehi- 8. Improved magazine sprinkler systems
cle. Theref~ the compartment(s) involved in the fire can 9. Installation of fire-stops for cableways.
be evac- and the tire isolated The Navy does share a In addition, the Navy is researching modeling of fim-
concern with mobility fuel. Because of serious fires in the spread. characteristics; studying toxicity, combustion,.. and
carriers USS Forresml in 1967 and USS Enretprtke in 1969, pyrolysis; studying use of new and special materials; study-
- the fiei used for carrier aimraft was changed fromJPr4 to. ing means to overcome smoke obscuration; and studying
JP-5, and the chemical washdown systems were converted use of nitrogen pressurization to inert closed chambers. This
to AFFF dispensers (Ref. 176). JP-5, with a flashpoint of last technique is used in submarines and could be of use in
6(PC (14WF), is much more difficult to ignite than JP-4, combat vehicles. Life is supported by the partial ptessure of
with a flashpoint near -18°C (0’’F), and the AFFF floats a oxygen, whereas fire is supported predominantly by the per-
b over a pool of liquid hydrocmbon fuel to prevent free centage of oxygem In a sealed environment partial pressure
reIease of vapor. The Navy also started the use of the and percentage of oxygen can be varied independently. It is
Twinned Agent Uni&*, which dispenses Purple K powder . ,possible to pressurize a sealed envtinment.with .an-.inert
or E solution. gas such as nitrogen to reduce the percentage of oxygen to a
The following are other actions taken by the Navy to value below that needed to support combustion but still to
enhance fire survivability of aircmft caniers: maintain the pamial pressure of oxygen so that tie atmo-
sphere is habitable for humans.
W%ile exploring h-extinguishing techniques, the Navy
*A mortally wounded Royal Marine Major within a magazine
Ordered the magazim flotxled before the propellant in it could has established that pressurized containers of water and a
explode very fine mist nozzle produced a system that is able to use
*%5 Twinned Agent Unit provides a firefighter with the capabil- .only a few gallons of water to extinguish an oil &e. This
ity to dispense either a liquid or a dry @w&r exdnguisham The

0,&
~~ ability was possiblebecausethe water usesheat energy as it
Twinned Agent Unit has two hosKA two vaks, and two nozzles. -
vaporizes, as described in subpar. 7-2.3.1. The Na-~ has
The fhefighter sehts which system to use based upon his assess- .-
‘—
~’;i mentofthe fire. also recommended that potable water mist can be used to
extinguish Class C fires.

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7-5.4 CXVILIAIN EQUIPMENT . 7-6 LESSONS LEARNED
A good example of a, civilian vehicle that has fire sup- lhe cases described in this paragraph present equipment
“ pression problems similar to those in combat ve~cles is the design and usage from which we may learn lessons. At the o
Caterpillar DIO tractor. The D 10 is a diesel powered, very least they present concepts that should be examined
tracked, off-road vehicle that tends to collect combustible further.
debris around the engine. This debris can become impreg-
nated with hydraulic fluid, oil, and/or fuel and create a 7-6.1 .DESIGN CONCEPTS EXPLORED IN
potentially hazardous fire situation. Also a hydraulic fluid or THE ASTB PROGRAM
oil line might fail and spray a combustible’ fluid onto the In the ASTB program several design concepts-were
engine or exhaust pipe and cause a fire. ~ explored that showed potential to enhance combat vehicle
Caterpillar furnished an AFES as optional’ equipment. survivability: .
This system used a thermal sensor based upon the differen- 1. Relocate the most hazardous munitions out of the
tial expansion of two dissimilar meta~s. The senior ‘was set most critical vehicie regions. . .
‘to trip at approximately 193°C (38001?) and send w electric 2. Use less hazardous impedimenta, including the less
current through a solid-state electronic controller. to a sole- hazardous munitions, to buffer the vehicle from the effects
noid valve. The solenoid valve ported compressed gaseous of the more haz~dous munitions.
nitrogen to a piston that drove a cutter. through a diaphragm 3. Separate the mobility fuel from the occupied com-
and thus liberated an extinguishant that flowed through noz- partment. ..-
zles onto preselected locations around”the engine being pro- 4. Use passive concepts, such as compartmentalizat-
tected(Ref. 177). ion, confinement of fuel cells, use of gelled water, and col-
This system is of particular interest because of the -- Iection of combustible liquids in the bilge, to preclude
development of selection criteria for extinguishants... The. fast-growth fires or fuel fires and/or. explosions within the
diesel engine is basically in the. open; therefore, there is occupied compartment. , ,.-,
an abundance of atmospheric oxygen., The candidate 5. Use passive conceptsr-such as double-walled. or
extinguishants considered were Halon 1301, HaIon 1211, jacketed fuel cells, to preclude fast-growth fires.. or fuel-air
Halon 2402, and the Class ABC dry chemical MAP. The explosions within the engine compartment. -.
tires anticipated could be Class A, B,’ C, or a combination’
thereof. This application nullified flooding performance of 7-6.2 DESIGN CONCEfiS USED IN FOREIGN
the extinguishant as an important selection criterion and TANKS o
elevated the throwing characteristics and the persistence To increase the range of operation of their tanks, the Rus-
as selection criteria. - Thus the gaseous extinguishant sians have used light-gauge metal. exterior fuel cells since at
Halon 1301 and the liquid flash-to-gas extinguishant least 1940, i.e., beginning with the KV-1 heavy tank (Ref.
Halon 1211 were not, as desirable as MAP and. Halon 178). At the present time, all the MBTs have two 200-L jet-
“2402. Between these two, Halon 2402 had betier throw-. .. tisonable external fuel cells (drums) .at the rear, and .tiee or
ihg chm’acteristics, was a more effective e~tinguishant, four 95-L external fuel cells. on the sponsons (Ref. 179).
and did not leave a difficult-to-remove residue. _Thus the fuel used first, approximately half the fuel carried,
Before the start of this development program, the Cater- is in external fuel cells. This design feature is a great sav-
~~
pillar fire-extinguishing ‘system used HiIon 1301. In this ings in interior volume. The jettisonable fuel cells cantile-
‘program MAP was considered and. rejected; then Halon vered off the rear are located where, when hit, the resulting
2402 was selected. The Halon 2402, was found to be much fires would be neither in nor on the vehicle. The sponson
“more effective than Halon. 1301 in requiring much less fiel celis again would probably not contribute to fire dam-
extinguishant to extinguish the fire’ and in inerting the age within the vehicle. The Swedish “S” tank also uses
region for a significantly longer. time.. Thus tie. incidence bf ... . ,.sponsoq-mounted fuel cells’ (Ref. 180.). These external. fuel
reignition was reduced. This system consisted of compo- cells added to the protection of the vehicle from. shaped-
nents designed by Caterpillar including spray nozzles, actu- ,, charge attack. me use of jettisonable or sacrificial external
ation valves, bottles, heat sensors, and a solid-state . fuel cells. should be considered.
‘~electronic controller. The spray nozzles were designed to
provide 0.91 kg (2 lb) per second of extinguishant per noz- 7-6.3 FULL-TIME AUTOMATIC FIRE PRO-
zle to the protected site. Because the tractor is open to the TECTION
atmosphere, there was no danger that the operator would be “ In some of the incidents described in the USASC data
in an enclosure wifi Halon 2402. This system is no longer mentioned in subpar. 4-1.1, vehicles parked in a motor pool
used because of the restrictions on halons. .. . have caught fire when no one “was present. Vehicles are too
valuable to be lost’ to fire. Each vehicle should have a full-
time AFES to protect it, and the system should be operable *
even when the vehicle power is off.

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7-6.4 AMMUNITION MAGAZINEDESIGN and W.-.Tsang, Construction of an Eaplorawry List of
,)!,$ A study was conducted at BRL of techniques to reduce Chemicals to Initiate the Search for Haion Altern-
o“!f the effects of a shaped-charge jet hit on the propellant of the atives, Technical Note No. 1279, National Institute of
main gun ammunition of the M60 MBT. Four of the five . Standards and Technology, Gaithersburg, MD, August
approaches tested and reported in Ref. 181 are WOrthy of 1990.
consideration. Other detads cannot be included because the 9. R C. Weast and M. J. Astle, Eds., CRC Handbook of
reference is classified. Chemirtty and Physics, 61st Ed., CRC Press, Inc.,
An upgrade option that can be incorporated into either the Boca Raton, FL, 1980.
MIAI or M1A2 MBT is FASTIXWW,i.e., an autoloader 10, R. M. Hodnett, Section 17, Chapter 1, “Water and
with two carousel magazines, each of which has 18, Water Additives for Fire Fighting”, Fire Pmtectian
12Wmn cartridge% located in the tuxet bustle. The two car- - Handbook 16th Ed., National Fn Protection Associ-
ousels are separated by an armored center web and have ation, Quincy, M& 1986. ...
small access pens through which cartridges are fed to the 11. D. W. Moore, Section 19, Chapter 2, “Halogenated
gun. FASTDRAW would enable the crew to fire at a rate of- . -. Agents and. Systems”, Fire Protection Handbook,
11.6 rounds/rein. The improved isolation would decrease 16th Ed., National Fue Rotection &sociatiom
vehicle vulnerability, and the ammunition load would be Quincy, MA, 1986.
increased by two rounds. (Ref. 182) 12. E. R. G. Eckert and R M. Drake, Jr., lntroducricm w
the T~er of Heat and Mass, McGraw-Hill Book
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>“ 105-mm Cartridges, 19 March 1984. Fire-Extinguishing System, Report No. USA
88. A. E. Finnerty, Extinguishing Ammunition Fires, CSTA-6564, US Army Combat Systems Test Activity,
Report No. ARBRL-TR-D241O, US Army Ballistics Aberdeen” Proving Ground, MD, August 1987.
Research Laboratory, Aberdeen Proving Ground, MD,. 100. A. E. Finnerty, Preliminary Evaluation of Powder
July 1982. Packs, Report No.. MR-3641, US Army Ballistics
89. E. Grove, World War.. H Tanks, Longmeadow Press, Research Laboratory, Aberdeen Proving Ground, MD,
Stamford, CT, 1987. December 1987.
90. LTC E. D. Colgan, V. J. Kowachek, B. Bonkosky, and 101. P. H. Zabel, ”Fuel Tank Specimens Ballistic Impact a
S. J. Kramer, Task Force Repoti on the Advanced Sur- Tests, Report No. 02-5896-1, Prepared for McDonnell

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430w&is-Tuka, .TuIw OIL by Southwest. Research NMTL1’ERA Report No3D-78-1260-U, New Mexico

O ~1,:

“~ill
+
,,
hsti~te, San #&tonio; l% 27 May 1980.
102. P. H. Zabel and G. S. Friesenhahn, Gunfire QualI&u-
tiorz Tats of 200-Galtow Filament-Woti
Technical University, Terminal Effects Research
Activity, Socorro, NM, 22 June 1978.
External . . 115. C. 1%Anderson, J. DziulG W. A. Ma.l]ow, and J. Buck-
Fuel T-, P/N 3016AOOOI, S0/ 004 and 005 for the master, “A Study of Inttrmescent Reaction Mecha-
H-3 Helicopter, Report No. 704711, Southwest nisms”, Journal of F~e Sciences 3, No. 3, 161-94
Research Institute, San Antonio, ~ 26 hdy 1982. (1985).
103. G. 1). ~ Tat ResuIts of .30 Galiber AP Pm.jectile 116. P. H. Zabel, Tk.rtProgram for Reduction of Wdnerabil-
on Pressunked Fiberglass-Rein foned Spherical .. ity of Armored Vehicle Fuel System, Report. No.
T~, Rocketdyne Internal Later, Santa Susana Test 061086-001, Southwest Reseamh Institute, San
Facility, Woodland Hills, CA, 21 August 1972. Also in Antonio, TX,.forFMCCorporation, San Jose, CA 28
H. W? Euker and P. H. Zabel, Gur$re Tat Activities Jdy 1986. -.
Conducted During the Period of January 1972. 117. MIL-T-27422B, Crash-Resistant, Aircrajl Fuel. T&
Through January 1973, Report No. TFD-73-115, B1 24 February 1970.
Division, Rockwell Corporation, Los Angeles, CA, 118. Fuel Cell Improvement Test Progmm, Engineering
March 1973. Test Report (ETR) No. 67, Fairchild Hiller Report No.
104. P. H. Zabel, ‘Temperature Control and Measurement FHR-3399, Republic Aviation Division, Fairchild
by a pneumatic Bridge”, C. M, Herzfeld, Ed., Temper- Hiller Corporation, Farrningdale, NY, February 1967.
ature, Its Mearuremenf and Cowvl in Science and 119. A. J. Hohen, AX Fuel Td Vulnerability Evaluation
htdustry, Vol. 3, Part 2, Reinhold Publishing Corpora- Report, AFFDLTR-74-55, US Air Force High
tion, New York NY, 1%2 823-35. Dynamics Laboratory, Wright-Patterson Air Force
-105. Effectiveness of Cibt@eigy Finr-Lan Xl in Protecting Base, OH, July 1974, plus verbal conversations of P.
Wing Fuel T- Agaimrt 23-mm API-T Attack, .. H. Zabe}. with A. J. Holten. .
Extracted by Ciba-Geigy from the Royal Airmaft 120. C. P. BraaMad6 Ballistic .T~t of Ml13A1/A2 Intental
Establishment Test Note No. 1148, Farnborough, Fuel T& (PM! 11678 175) IWth Explosafe@, Techni-
England, January 1977. cal Report No. 3802, Ordnance Division Engineering,
106. Patent 4251 S79, Fire Prvrection Means, US Patent FMC corporation, San Jose, CA, April 1982.
!:& office, Arlington, VA, 17 February 1981. 121. S. J. McCormick, P. F. Motzenbecker, and M. J. Clau-
0 “ 107. Private comespondence ilom P. V. Guethlein, son, Study of Passive Fuel T& Inerting Systems for
Ciba-Geigy, Fountain Valley, U to P. H. Zabel, Gmurtd Cbnbat Vehicles, Technical Report No.
Southwest Research Institute, San Antonio, TX, 13 13385, US Army Tank-Automotive Command, War-
April 1981. ren, IvQ Septemker 1988.
108. C M. Pedriani, “Powder-Fiied Structural Panels for 122. TB 5-4200-200-10, Hand Ponable Fire Extinguishers
Helicopter Fuel Fm Protection”, Amy Research Approved for Amy USG, Department of the Army,
Deveioprntvw and Acquisition Magazine, 19-20 Washington, DC, 1 September 1989.
(May-June 1981). 123. Brochure, Portable Fire Extinguished Water-Type,
109. J. W. McNeiIly, Field Erpedient Powder Packs for Walter Kidde Aerospace, Inc., Wfion, NC, January
Combat Aimafi, Bell Helicopter Texmon, Inc., 1992, and telephone conversation between P. H.
Arlington, TX Prepared for AppIied Technology Lab- Zabel, Southwest Research Instituti, San Antonio,
oratory, tigton, TX November 1984. ~ and G. Ewald, Walter Kidde Aerospace, Inc., Wd-
110. MIL-H-46170B, Hydraufic Fluid, Rust-hhibitecZ son, NC 19 August 1992.
Fitz-Resistant, Synthetic Hydmca&on-Base, 18 ‘., 124. M. E. Peterson, Section 20, Chapter 2, “Selection,
August 1982. . Operation, and Disrnbution of F~e Extinguishers”,
111. MIL-H-6083~ Hydraulic Fluid Petraleum-Btzre, for Fim Protection Handbook 16th Ed., NationaJ Fire
Preservation and Operatio% 14 August 1986. Protection Association, Quincy, ~ March 1986:
112. P. H. Zabel, Test Progmm 10 Demonstrate Enhanced 12s. A. S. Prokopovitah, Section 19,-Chapter 5, “Combus-
Survivability of Armored Aluminum Vehicle Fuel Sys- tible Metal Agents and Application Techniques”, Fim
tem to Shaped-Charge Attack, Report No. Ptvtecrion Handbook 16th Ed., National Fue Protec-
068899-001, Southwest Research hSdMe, San tion Association, Quincy, MA, Mach 1986.
Antonio, TX, July 1986. 126. R E. Tapscott, H. D. Beeson, M- E. Lee, M. A
113. Armored Vehicle (M113) Vidnerabili~ w Diesel Fire, Plugge, D. M. Zallen, and J. L. Walker, Extinguishing
NMT/TERA Report No. TD-77-1165E, New Mexico Agent for Magnesium Fire, Phases I-N, Technical
Technical ‘university, Terminal Effects R~earch ,-. Report No. ESL-TR-86- 17, New Mexico Engineering
Activity, Socorro, NM, 26 h’kly 1977. Reseatch Institute for Air Force Engineering and Ser-
114. Annared Vehicie (IW113) Vdnembili@ to Diesel Fire, vices Center, Tyndail Air Force Base, FL, JanuaIY
1986.
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IML-HDBK’684”
Ansul~ .Data..Shee~ No. F-9201, Navy. 125S Copper 144. ‘“Telephone.. conversti.. between D. L. Byerley,
Powder Models, Hand Portable and ~eeled Extin- AMFUIW Corporation, American Fuel Cell and
guishers, Ansul Fire Protection; Marinette, WI; 1992. Coated Fabrics Company, Magnolia AR, and P. H. @
Telephone conversation between P. H. Zabel, South- Zabel, Southwest Research Institute, San Antonio,
west Research Institute, San Antonio, ‘IX, mid G. A. ~, 1987.
Levcun, Naval Undersea Warfare Engineering Station, 145. K. R. Lardie, Validation Test Procedures (VTP) for the
Keyport, WA, July 1992. &lV7Al Automatic Fire Sensing and Suppression Sys-
Combat Lijesaver Course, Medical Tasks, Subcour$e igm (AFSSSj, Report No. AFSSSVTP2-86, US Marine
IS 0825, Army Institute for Professional Develop- Corps Development Center, Quantico,, VA, January
ment, Newport News, VA, 1990; 1986.
H. McGinley, “Motor Vehicles”, Fire Protection. 146. Brochures, FPT—Advanced Fuel .Cell Technology and
Handbook, 16th Ed., National Fire Protection Associ- FPT High-Technology Rigid Plastic Containers, FPT
ation, Quincy, MA, 1986. Industries .Ltd, Portsmouth, Hampshire, England,
D. W. Moore, “Halogenated Agents and Systems”, circa 1993, and a telephone conversation between J.
Fire Protection Handbook, 16th Ed., National, Fire Taylor, F~ Industries, England, and P. H. Zabel,
Protection Association, Qunicy, MA, 1986. Southwest Research Institute, San Antonio, ‘IX, 19.
MJL-M-62545A, Stanakrd Electronic Control Mod- March 1993.
Z&; 11 August 1989. ,’.’ 147. C. F. FOSS, “Proving Ground Progress”, Jane k
Purchase Description, Sensoc fire, Optical: System Defence W@kly (29 February 1992).”
Ulih’ Amplifie~ Standard Control, ~~Electronic, 148. ”The Advantages of a Dual-Spectmm UVllR Optical
A~D-2070, Rev. A, “US &my Tank,Automotive ~~Detectoc A Comparison Repon on Optical Detector
Command, Warren, MI, 29 February 1984. ,, Systemx, Spectrex, Inc., Cedar Grove, NJ, March
Fire and Explosion Safety and Survival, I$idde-Gra- 1985. . . . --.
viner,”Limited, Berkshire England. 149.; Automatic Fire Detection, and Suppression System for
Application Data, General Information ‘Automatic the Crew% Compartment of Armoured Vehicles,
Optical Integrity Ultraviolet Fire Detection Systems, Requirements and Spec@cations, RS 620001(2)-87,
Form 91-1000-1, Detector Electronics Corporation, Spectronix, Ltd, Israel, May 1987.
Minneapolis, MN, April, 1979. ‘“ 150. ~R. M. Ogorkiewicz, “Merkava Mark 3, the New
*
Data Sheet, SYS-304-2, Engine Bay Test. and Alarm Israeli Battle ‘Rink”, International Defense Review 22,
Panel (EBTAP), HTL Division, Pacific Scientific, No. 5 (May 1989).
Duarte, CA, February 1985. . . 151. Private conversation between B. Bonkos@, Armored
Data Sheet, SYS-301, Crew Bay Test and Alarm Panel Systems Modernization, Warren, MI, and P. H. Zabel,
(CBTAP), HTL Division, Pacific Scientific, Duarte; Southwest Research Institute, San Antonio, TX, fol-
CA, February 1985. lowing a visit by Mr. Bonkosky to Israel, 1991.
Technical Brochure, Duul-Spectrum Sensing and Sup- 152:- A. K. Babd?hanyan, Tanks and Armor- Troops, The
pression Syst.4ins, Hughes Aircraft Company, Santa Red Banner of Labor Military Press of the Ministry of
Barbara, CA, Undated. Defense of the USSR, Moscow, USSR, 1970, Trans-
ML-V-62547A, Valve and Cylinder Assemblies, lated by Gaylord Publications, Birmingham, MI, for
Halon 1301,5 April 1988. “US -y Tank-Automotive Command, Warren, MI,
Automatic Fire Detection and Extinguishing System Report No. FTO 1005, Foreign Technology Office,
for the Engine Compamnent of Armou~ed Vehicles, Wright-Patterson Air Force Base, OH, 1970.
System No. 450001, Technical Description: :153. J. Magnuski, Combat Vehicles of the Peoples’ Polish
TI1450001-86, Spectronix Ltd, Israel, June..l986. . . .- ~ Armed Forces, 1943-1983, Publishing House of, the
Telephone conversations, between S. McCormick; US Ministry of National Defense, Warsaw, Poland,1985.
Army “Tank-Automotive Command, Wirren, MI, and 154. ~~
G. Wohlfeld,. Translator, Instruction Manual for the
P. H: Zabel, Southwest Research institute, San Anto- . Components and Operation of the T-54 Tank, 507th
nio, TX; plus written correspondence. Ordnance Detachment, US Army Ordnance Tank-Au-
C. F. Foss and T. J1 Gander, Eds., Jane 3 Milita~ Vehi- tomotive Command, Center Line, MI, 20 March 1961.
cles and Ground Suppofl Equipment 1987, Jane’s 155.. Soviel 100-mm Gun Tank, Medium 1=55,
Publishing Company Limited, London, England; ST-CR-20-53-70, Foreign Science and Technology
1987. Center, US Army Materiel Command, Charlottesville,
Private, communication from COL L. R. S~nford, US .. VA, Undated.
Army, Office of the Director of Live Fire Testing, 156. D. S. R.icketson, Jr., J. M. Segraves, and LTC F. G.
Washington, DC, to P: H. Zabel, Southwest Research Sisk, Tracked Vehicle Fire Analvsis: 1984 Up&te, 9
Institute, San Antonio, TX, circa 1989. Technical Report No. USASC h84-2, US Axrny

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. - - Safety-Center, Fort Rucker,.ALJ984, and telephone c@~Re~mNo.~~/AS745-0~, Joint Techni-
4
:,i’1 conversation between LTC SislG US Amy Safety cal Coordinating Group on Aircmft Survivability,
,’,f
.’!
o Center, and Mr. Gooch, US Army Foreign Science and China Lake, CA, January 1976.
T~ology Center, Charlottesville, VA, 18 June 1984. 169. H. J. Villemain, Evolved Technology for Fabrication
157. W. Schneider, “Gunnery With the Soviet T-72MM41 and Aircrafi Applicability of a Preactivated Sealant
Tank”, International Defense Review U, No. 5 (May Se&Seal Fuel T&, Report No. JTCG/AS-76-5-013,
1991). Joint Technical Coordinating Group on Aimrai7 Sur-
158. T. C. Hillman, “Approaches and Applications of vivability, China Lake, W April 1980.
Active Fwe and ‘Explosion Suppression Systems”, 170. R. H. Fish and D.- Patterson, ‘Tkch.aical Consider-
Proceedings and Report, Volume i of II, Fire Safety/ ations in the Development of a Semirigid Void Space
Survivability Symposium— ’90, Alexandri~ VA, 68 Ballistic Foam”, The BR.LA4.DPARepon of the Pro-
November 1990, Defense Fm Protection Association, ceedings of the VulnerabilityKhuvivability Sympo-
Alexandria VA. sium, 21-23 October 1975, Vol. L& Washington DC,
159. D. J. LeBlanc, “Study of Passive and Active Fire Sup- “ pp. 245-64, American Defense Preparedness Associa-
pression Options for Fighter Aircraft Dry Bays”, Pro- tion, Alexandria VA.
ceedings and Repon, Volume I of U, Fire Safety/ 171. Firing Trials to Evaluate the Effectiveness of Atom-
Smviva.bility Symposium—’9O, Alexandi& VA, 6-8 . el ‘-Filled Dry Bays Adjacent to Fuel Cells Under
November 1990, Defense Fm Protection Association, High- Velacity A4ult@agment Attack, ICI Fibres, Har-
Alexandria VA. rogate, North Yorkshire, England, September 1970.
160. T. Dixon, Gross Voided Flame Arrestors for Fuel Td 172. J. P. Gillis and H R Cutler, Devefapment of
Explosion Protection, AFAPL-TR-73-124, US. Air ,. High-Tmperarure Fire and E@oswn Suppression
-..
Force Aero Propulsion Laboratory, Wright-Patterson - Systems, -Technical Report No. AFAPLTR-69-1 15,
Air Force Base, Om Febnmry 1974. US Air Force Aero Propulsion Laboratory; Wright-
161. T. O. Reed and W. D. Vahle, Qual@cation Tat Resufts Patterson Air Force Base, OH, January 1970. -
for Scott Paper Company Blue Hybri$ Polyethylene 173. P. H. Zabel, P. F. Piscopo, and L. E. Hendrickson,
Fcmm, ENFEF-TM-79-08, Aeronautical Systems - “Functioning/Malfunctioning of 23-mm Projectiles in
,,,, Division, Wright-Patterson Air Force Base, OH, &rcmft Integral Fuel Tanks, Resultant Target Dam-
,,;;!/ll: December 1979. age, and Relative Vulnembility of Neat and Modified
a 162 I? F. Jowitt and C. Henson, Exwnination of a Fibrous JP-5 Fuels”, Proceedings of the Symposium on Viil-
Flame Suppressant for ~losion Protection of Air- nerabili~ and Sunivabi@ of Sutface and Aerial Tar-
crafi Fuel Takr, TR 80002, Royal Aircraft Establish- gets, Washington, DC, September 1975, American
nten~ FarnborougiL England, January 1980, also P. Defense Preparedness Association, Alexandri% VA.
Cheversean, Intenechniques ,.. Protective - Foam 174. P. H. Zabel, Gunjre Tuts of JP-5/AM-l Modi&d Fuel
(Prvmel)-Fire Suppre.rswn Evaluation, Report No. Systm The Dynamic Science Division, Ultrasystems,
1098-LE-79, Repulsion Test Center, Ministry of Inc., Phoenix, Z Repared for hTaval Air Propulsion
Defens France, November 1979. Test Center, Trentom NJ, May 1976.
- 163. A. Szego, K premj~ and R D. Appleyard; Evaluation 175. B. R. Wright and W. D. Weatherfo~ Jr., investigation
afE#osafe@ Explosion Suppression System for Air- of Fire Vulnerability Reduction Effectiveness of Fire--
crajl Fuel Td Protection, AFWM-TR-80-2043, US Resistant Diesel Fuel in Armored Vehicular Fuel
Air Force Wright Aeronautical Laboratories, Wnght- Tti, Report No. AFLRL No. 130, US Amy Fuels
Patterson Air Force Base, OIZ July 1980. and Lubricants Research Laboratory, San Antonio,
164. C. Blair, “Ridgeway’s Paratroopers”, The American “- TX, September 1980.
Airborne in WorM Wiar11, The Dial Ress, Doubleday .: 176.- C.. H. POhler, CPT J. L. .NfcVoy, H. W. Carh@-J. T.
and Company, Garden City, NY, 1985. Leon@ and T. S. Pride, “Fn Safety of. Naval
165. hflL-T%39& iVonse~-Sealing, Removab!e, Internal, . Ships-An Open Challenge”, Naval Engineers Joti-
Aircrqli PrvpuI.sion Fluid System T&, 30 August nal 90, No. 2,21-30 (April 1978).
1983. 177. H. Schultz, An ~-Road Machine Fire Suppresswn
166. MIL-T-5578c Self-Sealing, Aircrajl Fuel T&, 31 Systew Earthmoving Conference, PecuiA iL, 7-9
Jtiy 1963. April 1987, SA.E Paper 870822, Society of Automo-
167. T. B. Squire, Se~-Sealing Fue[ Tmk Preactivated tive Engineers, Wamendale, PA.
Seaiant Program, Report No. JTCGiAS-74-5-007, 178. C. F, Foss, The Illustrated Encyclopedia of the Worid3

,,
o[~ Joint Technical Coordinating Group on Aircraft Sur-
viability, China Lake, CA, July 1975.
‘‘i~’ 168. T. B. Squire, Development of a Preactivated Seaiant
22mks and Lighting Vehicles, Chartwell Books, Inc.,
New York, NY, 1977.
179. D. C. ISby, Weapons and Twtics of the Sovier Army,
Wuh Low T&mperature C@bility for Fuel Ce!IAppli- Fully Revised Edition, Jane’s Publishing Company
Limited, London, England, 1988.
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S.-Berge,-.’:Hldden for 35 Years.the.S:T~k’s Armor”, J. D. BirchalL .:.On the Mechanism of Flame Inhibition by
International Defense Review 26, No. 3 (March Alkali Metal Salts”, Combustion & Flame 14, 85-96
1993). (1970). : 9
A. E. Finnerty, Techniques and Models Applicable to MAJ N. R. Jenseni Independent Evalimtion Repon for the
Extinguishing Fires in Steel Car&dge Cased Development Phuse of the M60A3 Automatic Fire
Rounds(lJ), Technical Report No. BRL-TI?-3088, US - Extinguisher System (AFES) Product Improvement,
Army Ballistics Research Laboratory, Aberdeen Prov- US Army Test and Evaluation Command, Aberdeen
ing Ground, MD, March 1990, (THIS DOC~ENT Proving Ground, MD, March 1987.
IS CLASSIFIED CONFIDENTIAL.) ~, B. Lewis and G. von Elbe, Combustio~ Flames, and Explo-
Western Design Corporation, “FASTDRAW Improved sions of Gases, 2nd Ed., Academic Press, Inc., New
Bustle Storage System”, International Defense York, NY, 1961.
Review 25, No. 5 (May 1992). ‘ ~ J. A. Senecal, D. N. Ball, and A. Chattaway, “Explosion
Suppression in Occupied Spaces”, Proceedings of the
Haltin”-Options Technical Working Conference, Albu-
BtiLIoGR.APHY : querque, NM, 3-5 May 1994, New Mexico Engineer-
ing Research J.nstitute, Albuquerque, NM.
C. E. Anderson, J. J. Dziuk, and D. E. KetchUrn, A Study of W. Porter; N. E. Schmidt, and C. V. Bishop, Halon 1301
,~, Formulations and Thermophysics of Intumescent Sys- Fire Extinguishant Toxici~ Program, Draft Report
~” terns, Report’ No.. 06-8766, Prepared for ‘Naval Air No. NASA-TR-411-002, Vok. I, II, and III, NASA
Development Center,. Warminster, PA, by Southwest Johnson Space Center, white Sands Test Facility, Las
Research Institute, San Antonio, TX, September 1988. Cruces, NM, 12 August 1985.
D. N. Ball, “Aircraft Cabin Water Spray System’;, Proceed- D. J. Rasbash tid G. W. V. Stark, “Extinction of Running
,,..-, ings of the Civil Aviation Authc&’~ (C&l) Consulta- Oil Fires”, The Engineer 208,862-4 (1959)..,.. ---
tive Conference on Aircra# Cabin Water Spray D. J. Spring, T. Simpson, D. P. Smith, and D. N. Ball, “New
Systems, London (Gatwick) Airpo~, Englimd, 29-30 Applications of Aqueous Agents for Fire Suppres-
May 1991, Civil Aviation Authority, London, sion”, Proceedings of the Halon Alternatives Techni-
England. cal Working Conference, Albuquerque, NM, 30
D. N. Ball, D. P. Smith, and ~. J. Spring, “Development of April-1 May 1991, New Mexico Engineering
an Aircraft Water Spray System”, Seminar 25, Airwor- Research Institute, Albuquerque, NM.
thiness—New Ideas, Institute of Mechanical Engi- T. Simpson and D. P. Smith, “Suppressing Fires in Telecom-
neers, London, E’ngkmd, 1992, and co@rnunications munications Switchgear”, Fire Prevention Magazine
from D. P. Smith, Kidde International, ,Berkshire, 267 ‘i&brCh 1994).
,,
England, to P. H. Zabel, Southwest Resetich Institute, Proceedings of the Live-Fire Test Crew Casuulty Assess-
San Antonio, TX, 25 July and 2 August 1994. ment Workshop, 18-19 October 1988, Naval Subma-
M. Bennew “Advanced Concepts for Aircraft Fire Protec- rine Base, Groton, CT, October 1988.
,,’
tion Systems”, Proceedings ad Repoti,’ Volume I of Proceedings From the Seeond Live-Fire Crew Casualty
H, Fire Safety Symposium—’9O, Alexandria, VA, 6-8 Assessment Workshop, 29 October-1 November 1990,
November 1990, Defense Fire Protection Association, Brooks Air Force Base, San Antonio, TX, 1990.
Alexandria, VA.
,,’.

,, .,

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,J
oIl!,,~!
,,
CHAPTER 8
TEST AND EVALUATION FOR DESIGN VEIUI?ICATION
The
roles of testing and modeling in the design of a combat vehicle forjire survivability are discussed Testr of existing or
generic systems are used to develop computer mod.ds and mathe~”cal mode+ of the naturnl phenomena involved The
computer && are used to design and size vehicle systems forjlre prevention and/or exringw”shment. Tests are used to ver-
ify the pe~o rmance of the system. T-t results are also used when computer models are upgraded or venjied There are no
computer models in existence wn”tren specijicalty m perform these tasks, but there are some computer models that can be
rnoayled to do so.

8-O LIST OF SYMBOLS identied in broad opemtiona.1 terms, which are pmgres-
sivel y uanslated into system-specific performance rwpire-
c= concentration of extinguishan~ mg/L
ments. Where new or modified equipment is need~ the
c= a calibration constan~ (W/m~mV
performance and affordability of these material needs are
e = sensor outpu4 mV “ thoroughly evaluated. The process is a phased series of steps,
P& = probabili~ of damage given a hi~ dimensionless as shown on Fig. 8-2. ‘Ilte designs of combat vehicles have
Pm = probability of kill given a hi~ tiimensionks evolved over the years in many different forms. Require-
Whd ments, both stated and impli~ have multiplied thus fitting
Q= heat flux,
them together in a single vehicle becomes a challenge. Fur-
R= resistance, Q
ther, installing an item to meet one requirement could hinder
T= temperarure,°C compliance with another. The Amy cannot afford to fabri-
Tu = limit tempemture, “C cate a host of specimens to meet a single need and then try
v= vohage, V them out, In the early design stage the Army must be able to
evaluate specitlc features in order to select those that, when
assembled, can best meet all design requirements. To make
8-1 INTRODUCTION
this selection expeditiously and e5cient.i y, the designer must
/,&
>,
,, ,, Combat vehicles are designed to perform cettain tasks. be able to predict performance not only for the extremes of
o
This design evolves following a process specified in Depart- conditions in which the vehicle must operate but also for
ment of Defense (DoD) Directive Number SO(X).1 (Ref. 1) attack by weapons of hostile forces. For fire survivability the
rmd DoD Instruction 50W2 (Ref. 2). The three major deci- designer must assure that even when the vehicle is hit by an
sion-making support systems and their interactions that con- overmatching threa~ the results will not be catastrophic.
stitute this process are shown on Fig. 8-1. A mission need is Rediction of performance aftes ballistic attack can be

-m

@ .
I SrL2es ~ Ocqp”ii
Tea
I

T .

[
Resmm?Rs@Emm andCQmtraii !
$ t t

Figure 8-1. Major Decision-Making Support Systems and Key Interactions {Ref. 1]
8-1
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MIL-HDBK-684
~.A--’.---= -------- --~ ~------- a
8
$
n
‘%%5- : p~:~:-:
8
1
t

$
8
I
n ~ L-------a
8
a
#
: 7
MissionNeedSmmmenl t
a t
L -----

?
s
a ~rE?::
I
t 1

‘:
Operational Requirements Document
“:
●
=------- ‘-----

aasdii
I *
eomepr

System/ DeveJop,ment
{
/ ProductSpecifications
,- J

Figure 8-2. Rqpiranents Generation Sy~em (Ref. 2)

based upon, theoretical studies, upon experience in battle, it was available at the laboratory or test site, not because it
antior upon test data. Theoretical studies are the poorest was the best device for the test. There are usually many mod-
source of perfo~ance data. ‘l%eory is best used to guide. els of devices that could perform the desired function(s) and
the design studies and test programs that produce tbe many suppliers.
design data. Battle damage is also a poor source’of design Which data cm’ be obtained and which data are needed
&ta primarily because detailed studies are not usually must be established. The following question could be asked:
‘made of the resulting damage and its cause. The best Which useful data can be obtained and documented without
source of data to guide survivability design is a well- unduly increasing the test cost? As a minimum for each test
planned test. The majority of tests perfo~ed are not or combat operation, we should have descriptions of the tar-
generic; they are conducted with specific weapons used get and threat, the incident or test,. and the events and
against specific targets. If detailed descrip~ons of the results. The descriptions of the threat and target should be in
threa~ target, test conditions and events, and the test results sufficient detail for an” independent evaluator to know what
qre d~umented, specific tests of specific items can be cor- materials came in contact throughout the incident and the
related with other tests to provide generic guidance. Then condition and strength of the materials and their spacings in
the battlefield data can be used for verification. ‘~ order to evaluate penetration and ignition source generation,
This chapter is not intended to instruct instrumentation impact location, and threat trajectory. Other information is
personnel how to use pressure transducers, temperature- also needed, such as mass, shape, explosive content, fuze
sensing devices, or the associated .recording and playback functioning details, target contents, parameters that affect
equipment. The intent is to inform. designers and program ignition (such as. combustible fluid bulk temperature, and
managers what types of inshuments are available and what flash point), and which survivability enhancement features
types of data can be obtained so they will know what to are “present. The description of the incident or test should
require from the instrumeiitation specialists. No attempt include impact velocity, impact obliquity, and weather con-
has been made to describe all makes and models of instru- ditions-i.e., ambient temperature, humidity, barometric
ments, nor is the inclusion of a specific device to be consid- pressure, and wind speed and direction. The description of
ered an endorsement of that device. The equipment used in test events includes (1) threat penetration into the targe~
@
the specific instances described was often chosen because which includes portions of the threat that may become sep-

8-2

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MIL-HDBK-684

,0~-On
~,,
-~ aratd (2) sprdl generation,

‘~~1~ fo~
of the imhon
(3) locations, magnitude,
sources generate~ (4) sources and
of the combustibles broadcas$ (5) locations, ignition,
and world”. Also care must be taken to assure that the rnathemat-
ical models are correct and that the data”used to develop
these models are comet and represent the proper phenom-
-.. and duration of fires, and (6) means needed to extinguish - ens. Once all of these steps have been followe~ valid Yehi-
the tires. Ile test results should include perforations in the cle designs or modifications can be selected. -
target and materials in front of and behind the targe~ func- The roles of testing and modeling in the design of a sys-
tioning or mrdfimctioning of the threaq damage to the tar- tem follow:
ge~ particularly damage affecting the ignition and 1. Testing provides the data by which mathematical
combustion of the contents; functioning of any survivabil- models can be developtxiof~the phenomena involved in the
ity enhancement device, other incidental damage, move- fimctioning of a specific design under specific loadings, and
ments, or incidents that occurred; residual mass and the it provides indications of the sequencing of these phenom-
condition of threat remnants; residual mass and/or volume ena so that a logic Bow can be prepared.
and locations of combustibles and extinguishants. This may 2. Computer models are prepared by establishing the
seem like a lot of information from a “simple” tes~ but all logic flow andlhen the speciilc mathematical models needed
of it is readily available and need only be observed and in order to predict the phenomena observed The parameters
morde~ except for the flash point of the fluid, which can needed are selected from theoretical evaluation of the phe-
be determined and recorded. Motion pictures or videos are nomena. These parameters must be amenable to quantifica-
excellent methods of recording much of this information. tion and determination in practical tests. ?hese computer
Even a “simple” test is expensive, and the agency paying models are prepared and verified by additional tests.
for it deserves this minimum for its money. Some tests 3. Candidate survivability enhancement concepts are
involve obtaining more information and thus involve more selected and their capabilities established by using the comp-
-complex instrumentation. uter models. ‘l%ese concepts are incorporated into the
‘fhe next question is “What will be done with the informa- design of test specimens. . e
tion collectedin these tests?”. Some tests are intended to 4, Conceptual survivability enhancement features are
demonstrate the efiicacy of a speciiic vehicle design to meet tested for effectiveness. The results from these tests are used
specific requirements. These requirements, however, may to verify and/or improve the computer model and to plan

ij~’
o their
.,,~,
change. Very few combat vehicles remain unchanged over
service lif% and the setwice life could be greatly
extended over what is currently envisioned The US Army
improvement of the survivability-enhanced
-
design.
5. llte design is modified, and qualification test speci-
mens prepared and tested ‘he computer model is exercised
could place tanks in depot storage in the same manner in to predict results.
which the US Navy %nothballs” ships. In the event of a .6. Test results are compared to the computer-predicted
major confiicq however, these tanks could be upgraded and results, and any differences explained. The test results are
b used in secondary theaters or for tmining and thereby used to improve the computer model and to qualify the sur-
allow the first-line tanks to be deployed to the most critical Vivability-nhanced design.
theater. Our M60A3 main battle tanks (MBTs) are still 7. The system design is incorporated into the vehicle
highly effective against most of the tanks in the world. These design. A vehicle is then built and subjected to design ven6-
“ could be upgraded with additional parasitic armor and sur- cation tests. The computer model is exercised to predict the
vivability enhancements in order to approach first-line tank test results.
status. Israel is still using upgraded US M4 tanks. and the 8. Design verification test results are evaluated to ver-
Russians store T54/55 MBTs. One use of test data gathered ify that the vehicle design meets the specified requiremems.
fkom obsolete or obsolescent combat vehicles is to plan the These test resulrs are also used to check and improve the
upgrading of those vehicles. Another use is to plan the computer model.
design and flnure upgrading of new vehicles. ‘IMs handboqk Throughout this process the computer mo&l is checked
&mons%rates tlm lessons learned with the British”Mark 1“ -and improved by factoring in the results of each-series
and Mark IV tanks in 1916 and 1917 are still applicable to and modifying the design of the vehicle or its components to
tanks to be made tomorrow. improve the performance of the systerm l%ere is continuous
Computer models enable designers to predict the relative interaction between tests, vehicle design, and predictions
effectiveness of candidate techniqu~ but software for sur- throughout the development process.
vivability enhancements would have to be developed. This chapter covers the test requirements and capabilities
Although there is no existing software, computer models available, as well as the computer software available and the
could be prepared to predict the life cycle cost of these sur- requirements for such software. Life cycle cost is needed to
vivability enhancement- concepts in specific combat vehi- establish affordability. For a discussion of cost analys~ see

0
cles. Care must be taken, ltowever, to assure that computer par. 1-5.
~,,~~ ‘ models will perform properly and wiil represent the “real

8-3
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NIIL4+DBK-684
~~8-2 PERFORMANCE PARAMETERS
TEAT CAN BE TESTED “.
The parameters that cag be tested ‘“include pressure and
temperature ,versus time, gas concentration, and extinguish-
ings ystem event timing. To select instrumentation for these
parameters, boti the purpose for which the data are to be
‘used,and the environment under which the data ‘kre to be col-
lected rhust be considered.
‘Pressure and temperature data are needed to evaluate the
potenthl effects on occupants and equipment. The effects on
occupants and equipment, however, are usually functions of
impulse or heat fl~ received and often of the rate at which
the impulse and energy are received. Specific i~pulse is the
integral ,of pressure versus time; heat flux is ihe rate of (A) Pretest Picture of Pencil Gages ,and. Thermocouples
change of heat energy per, unit ties. The gas concentration Affixed to Fixture Walls and Piezoelectric Transducer
Mounted in Fuel Cell Access Plate
has to be established as that the eyes and lungs of occupants
wo@d receive. The vapor, mist, or particulate concentration ..”
that would affect vision should also be established. ~~
Instrumentation must withstand the enviro~ent of a
combat vehicle that sustains a .ballis~c impact; ,If the threat
being tested has a shaped-charge warhead, the test ve~cle or
specimen is going to receive a severe impulse load from &e
blast of the shaped-charge wNhead..At the least this impulse.
load will send shock waves through the vehicle and/or test
fixture body.. The impulse load may also cause the vehicle
andfor test fixture to displace abruptly (Ref. 3). Blast prei-
sure gages installed as shown on, Fig. 8-3(A) have been
destroyed by “whiplash” when a testfixture was displaced
approximately 152 mm (6 in.) when loaded by the blast from
a shaped charge. These gages were relocated on a separate (B) Pencil .Gage Showing “WhiplasW Damage After Test
sbd that was not subjected to the blast load.
In general, these tests are to deterrhine what happens when” Figure 8-3. Inappropriate Test Instrumentation
a given threat hits a given target in a selected location. me LOc@ion (Ref. 3)
relative effectiveness of candidate design “X” can be estab-
lished by comparison of the results from a baseline test to. approximately 294 mh (965. ft/s) (Ref. 4). The velocity of the
those of configuration “X’. “’ shaped-charge jet is primarily from the detonation of the war-
This paragraph addresses testing combat ,vehicles or their head, alone; the residual velocity of the projectile is only a
components that contain combustibles for fire survivability minor contributor to the total velocity of the jet. Thus a stati -
and vuhterabili~ ‘when subjected to the teriuinal effects of tally. fired shaped charge is an adequate simulation of this
battlefield threats. The types of battlefield threats that are threat. When a HEAT projectile is fired from a tank gun, the
most probable to cause fire within a combat vehicle are velocity at impact .is approximately 914 m/s (3000 ft/s); the
shaped-charge warheads, high-velocity kinetic energy pro- blast and fragments from such a threat would significantly
. ... . . contribute to the damage to the target, particularly for lighter
‘jectiles, and land mines.
An example of such a situation is an aluminum armored armored vehicles.
vehicle to which the threat considered is a shaped-charge The fragmentation horn the HEAT projectile body would
warhead from a shoulder-launched, rocket-propelled weap- have a primary velocity that is directed radially. For normal
on. The shaped charge is presumed to detonate on contact impacts (O deg obliquity), only where the projectile has an
with the. outer surface of the vehicle at a standoff of 2 1/2 impact velocity approximately that of the tank gun projectile
cone diaeters. Most fin-stabilized, rocket-propelled, high- would any casing fragment impact near the hole in the target
explosive, antitank (HEAT) projectiles are traveling at a rel- surface created by the jet.. Also that fragment would most
ative] y Iow velocity al. impacu hence the greatest warhead probably be from ihe base of the projectile and would have a
effect against the vehicle is obtained ffom the jet formed by. comparatively low forward velocity. This base fragment
velocity would be the difference between the projectile
the shaped charge. ~S jet has a velocity of approximately
7620 m/s (25,000 ftk). The projectile, if it is a Russian
rocket-propelled grenade (RPG)-7, has an impact velocity of
velocity at impact and the velocity imparted’ by the charge
detonation, which would be in the opposite direction, and
9
8-4
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NNL-JiDBK-684
. . these fhgments would be of a comparatively large size
,,,$ (mxima~ly ~ of tie hole produced by the jet). llIUS
‘~
o. ‘4: these base tigments should be unable to penetrate the armor
. . .. of the vehicle. The other projectile casing fragmenrs wouId
most probably not penetrate through the vehicle tumor either.
These fragments will impact the target when the trajectory to
target surface angle is ecu% as shown on Fig. 8-4 by an.
M28A2 warhead at 454eg obliquity (Ref. 5). ‘he behind-
the-rmnor effects probably would be produced by the jet.
Actual vehicle armor should be simulated, if not used, in the
tests.
For light US combat vehicles the armor might be one or
two thin steel plates and then a thicker aluminum plate. For
an aluminum armored vehicle that has spaced steel exterior
armor p~ates, the jet from an RPG-type. warhead could pm
duce a 25-mm (l-in.) diameter hoie in the ahminum armor
protecting the fuel system component. ‘Ihis jet would readily (A) Jet Passage and Fuel Mist Fo[lowing Jet From Fuet Cdl
perforate the fuel system component and the fuel and most of
the internal components of the vehicle in the path of the. jet,
and the jet could exit the vehicle through the opposite side.
This action was demonstrated repeatedly in the tests con-
ducted for Kanakia and Wright (Ref. 6) and those conducted.
by Zabei (Ref. 3). .
Where the jet passes through a fuel cell, a fuel spray fol- .
lows the jet and enters the vehicle as a mis~ as shown on Fig.
8-5. This mist is readily ignitable, but the strongest ignition

,,~~$
o, source is produced by the subsequent impacts of the jet with
aluminum components within the compartment, including
the far wall of the vehicle. Ignition of this fuel mist and/or
vapor and air mixture within the compartment results in a
Ilreball, the heat from which can severely injure the occu-
pants. Additional fuel can flow into the compartment through
the jet perforation and any ruptures in the fuel cell, as shown
on Fig. 8-6 (Refs. 3 and 7). Hydraulic ram pressures, which (B) Fuel Spraying Out of Fuel Cell From Ruptures Both in
—
Front and Rear

. Figure
8-5.
-Test of Actual Fuel Cell (I@& 3 and
3
oscillate by apparent expansions and contractions, produce
fuel sprays where the fuel is forced through ruptures in the
fuel cdl (Refs. 8 and 9). This fuel can vaporize and ignite
from the heat of the earlier flash fire; with air being continu-
ously input into the compamnen~ combustion within the
. . chamber cart be sustained. Occupants in the path of rhe. jet
-- would be wounded, possibly mortally, by the je~ and-occup-
ants near the path of the jet could be hit by span. These and
. any other occupants could receive severe burns. All could
receive danxige to eardrum, as described in par. 5-3. The
unburned liquid. fuel can collect in the bilge, and if there is
sufficient air, a pool lire could result that could render the
vehicle irreparable. Although it is of less importance at this
Figure 84 Jet Entry Hole and Fmgment time, perforation of the t%el system components can ako
hpacts From Static-1%’ed M28AZ Warhead result in 10SSof mobility.
Piaced at 4%kg Obliquity to a Heavy-Walled Items of interest to measure in this example are the hydrau-
Fuel @l (Ref. s) lic ram pressures in the fuel cell, the shock or blast pressures
within the test fixture (troop compartment), and the tempera-

8-5
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IWL-HDBK-684:
8-2A PIKESSUREAm.TEMPERATURE TIME
,, HISTORY
The two most important parameters to establish for fire
survivability are pressure and temperature versus time. -The
hydraulic ram pressures versus time or their integral
(impulse) should be established so the designer will know
the lo~ding to be expected within a fuel cell. The impulse
loadings transmitted through air onto the walls of a maga-
zine are a function oflhe type of chemical reaction of the
explosive contents. Similarly, the air or shock pressure load-
ing on the walls of an engine compartment or the upper por-
tion of a fuel cell in contact with the ullage can be highly
impulsive where an explosive fuel-vapor-air mixture-ignites,
as indicated in subpar. 8-2.4.1.3. In addition, the shock pres-
,,
sure”versus time of a threat passing through a troop compart-
(A) Cracks in Fuel Cell: Front and Right ,~de ment must be known in order to establish the effects on
personnel, as described in subpars. 5-3.4.3 and 5-4.4. The
need to establish temperature buildup versus, time is
described for h~man’incapacitation in subpar. 5-2.2 and is
described for design of fire-sensing subsystems in subpar. 8-
3.4. ~s need to establish temperature versus time was also
.. .. - described in subpan 4-8:4.2, in which the differential heating
of- the. magazine. walls given gun propellant. .,combustion
,,, resulted in buckling of the magazin’e doors. There is a great
need to know the changes in both pressure and temperature
versus time and, since the rate of combustion of various
materials can be affected by either presiure or temperature,
to know the relationship of the rate of change of pressure and
9
temperature to the temperature and/or the presstie.

,8-2.1.1 Hydraulic Ram Pressure Versus Tiie Re-

corciktgs
Hydraulic ram is a phenomenon that increases the damage
to a liquid container upon penetration by a high-velociiy
threat. There are very few data available, however, by which
hydraulic ram can be characterized, particularly when the
~ .,.-
“threat‘is a shaped charge. Over the years pressure transduc-
ers have become sturdier Wd have a faster response. IrI 1957
1’ a Photocon pressure transducer was used to measure the
OY m-w! hydraulic r~ resulting inthe liquid oxygen (LOX) feed line
of a large liquid propellant rocket engine when the flow
~-, --, ,-ce of Fuel Cell
through the main ‘oxidizer feed valve was suddenly stopped
~-.. ---=. JO Fa.wl ~ell Shoivn in Fig.
(Ref. 10). The. pressure transducer had to be protected from
kfs.3and7) ““ ‘.” “,”
... . . the low. temperature (–1 83.O”C (-297 .4°F)) of the LOX by
use of a jacket normally used for protection-from heat. A liq-
ture within the test fixture. In some cases s~ri. gages can be
uid was forced through the jacket-to maintain the transducer
placed on metal fuel cells to provide information for design-
temperature within the operable temperature range. The
ers; and accelerometers can be used to record gross vehicu-
transducers successfully measured the LOX pressure varia-
Ihr, or test fixture, reaction to the blast ancl/or “impact. (The
tions when a series of twisted bourdon tube transducers used
test fixture in which the gage shown in Fig. 8-3 was ‘mounted
previously had f~led to measure the pressures and had also
weighed over 1200 kg (1.3 tons) and”was moved 100 to 1$0”
failed to survive.
mm (4 to 6 in.) by the blast of the warhead.) +41sopictorial
More recent pressure transducers that use piezoelectric
recordings of the events within the test fixture should be
crystals have a faster response, are smaller, and can better
obtained. Obtaining samples of the gases within’the test fix:
withs~nd impulsive pressure changes. In 1974 Kistler
ture requires greater sophistication of both test and instru-
piezoelectric transducers were used to measure the hydrau-
mentation.
lic ram pressures within a liquid, which resulted from the

8-6
 Downloaded from http://www.everyspec.com

MIL-HDBK-684

impact of.a severely yawing 14.5-mm armor-piercing incen- tmnsducers were mounted in fittings at the end of the steel
~f ~, ~ tracer (Nm bullet (Refk 8 and 9). Fig. 8-7 is a tubes seen in the center of the test iixture. Each transducer
0“ sequence of frames from a high frame rate motion picture was approximately 152 mm (6 in.) horn the anticipated brd-
L“-.-4haLshows.the passage of this bullet through the liquid and let trajectory. A typical pressure recording is shown in Fig.
the tit hydraulic ram pressure oscillation. The pressure 8-8.
‘..

Fr. 3, t= 0.0006s Fr. 5, t= 0.0011 s Fr. 8, t= 0.0018s

Fr. 25, t= 0.00S6s Fr. 40, t= 0.0089s Fr. 61, t= O.0136s

.

%-
Fr. 99 t= 0.0220s. Fr. 136, t= 0.0302s Fr. 154, t= O.0342s

.. . . . . .,---
. . ..
. . . .,. -

Fr. 290, t= 0.0664s. Fr. 425, t= 0.0944s.

Notes: 1. The pressure transducers are in hermetically sealed fittings at the ends of steel tubes and can be seen in Frame 3-
2. These photographs were made by a HyCam at the rate of 4500 frk. -
3. Fr. = frame
,:,,,
,O,:
,)11:
,>,, _ 8-7. Hyiradic Ram ButkringTS (@f. 9)

8-7
 Downloaded
.:, from http://www.everyspec.com

,.,. .:.
:: IW;HDBK-684 .
,.
In 1982 recordings of hydraulic ram pressures generated
by fully tumbled. 14.5-mm APIT bullets were made success-
fully by using either piezoelectric pressure transducers or *
., undev’ater tourrnaline -blast pressure transducers. Water
was contained within aluminum-lined, fiber-wound external
fuel Ceils, and the bullets impacted at a fully tumbled atti-
.-
tude. Pressure 3, shown in Fig. 8-9, was measured 1.041 m
(41 in.) from @e impact location with a PCB Model
102AO3* piezoelectric pressure transducer mounted “in a
bu~ead at the nose of the fuel tank. Pressure 4 was mea-
sured at a bulkhead at the tail of the fuel cell approximately
3.2 m fl 1 ft) from the impact location. The pressures mea-
sured using a PCB Model 138A underwater blast transducer

t,
146 g (5.75 in.) from the impact location areas shown on
Fig. 8-10 (Ref. 11). The biaxial strain gage recordings on
Fig. 8-10 are both saturated.**

‘mm----

EEIE
*Use of equipment by P~B Piezotronics, Inc., or other manufactur-
ers does not constitute endorsement by the US Government.
I Impact **~e fil~ent.wo~d, composite fuel cell being tested was
- — grossly delaminated under the biaxial strain so that the layer of
.
< materi~ on which the gage was mounted was no longer stressed.
..—.
-.
Figure $-8. ‘@@al Recordings Made SWth Pres- .
sure lkansducers Configured as Shim on Fig.
8:7 (Ref. 9)

i’

,.

,,

Figure 8-9. Hydraulic Ram Pressq Recorded Using a PCB I02A03 Piezoekctric ~essure Trans-
ducer (Ref. 11)

8-8

.’,
 Downloaded from http://www.everyspec.com

MIL-HDBK-684

(~sr=dmti amw@Hatatrain 9armwaaJso*.)

Figure 8-101 Hydraulic km I?mwure Frwn an Underwater Blast lkansducer (Ref. 11)

o,,1# ,
b another program (Ref. 12) a 7.78-g (120-grain) steel
fragment simulator impacted a fuel cell with a thin ahmni-
num face at 1585 m/s (5200 ft/s). The cell contained JP-5,
opposite quadrantson the same fiel cdl wall. The miniature
chronograph screen anays seen on F]g. 8-11 were an
attempt to ascertain fragment simulator velocity immedia-
water, or methanol. Hydraulic ram pressures on the inside of tely before and after perforation of the aluminum sheet.
the face were measured with PCB Model 138A underwater “fltis attempt was not successful primarily because of the
blast grtge% shown in Fig. 8-1 l(A). These gages were difficulty maintaining intmcreen distances accurately. The
cemented to the interior fuel cell wall with an elastomeric interior screen may had been fuel proofed with spray-on
cement. Biaxial main gages were attached to the exterior epoxy .(Ref. 12) The pressure and strain recordings shown
surface of that fuel ceil wall, as shown in Fig. 8-11(B), in on Fig. 8-12 are typical of the pressure on the inside of the

(A) InternalSurface of the Fnxtt Face of the Test F@ure (B) Fm-nt Face of-Test I%ture
Gxnttsy of Southwest Research Lnstitute.
,,!,:,!,,
;!’
o“P’~r~ tgtm $3-IL Strain
Gageson External Surface and Underwater Blast Gages on Internal Surface of Fuel
cell F- (Ref. 12)
8-9
 Downloaded from http://www.everyspec.com
.
,,

MWHDBK-684

,, ““frontface and tie strain “in the rear face. “The underwater in.) and 1“13 mm (4.45 in.); respectively, from the impact
blast gages were located at Points 1 and 2, 51.3 mm (2.02 location; the liquid for the test shown was water.
., e

-11 a1 1 1
,. .
I ! 1 1 1 , I 1
I-154)
,, ~,(A) Internal Pressure at Point:l of Fronl Face
10 I t i 3 i I 1 E I I * 1500
.: +Tlme Ze,ru .
. -p
. ..
z 1000a
25 - a-
a- 500;
% a)
m
m ti
. ;. .,.... ... ..... ... .. ..... ..... ..... ... 0

) t , t ● I 1 f 1 t I I 1 -500
(B) Internal Pressure at Point2 of Front Face
.,.

4000 -
. Time Zero+: a
E .
= .
.=- 2000 - . .
g .

-2000 I
P
I t I ! ,.I 1 1.1 ! I
(C) Strain at External., Surface of Rear Face, x-axis

6C00~”, ,{lr, ., [ I I I I I I I
d

E
a3000 . .
.-
.-=-

‘, 0
-1500
.’ ,.
(D) Strain at External Surface of Rear Face, y-axis
.,. lime. tms ~~“ ..
‘,
Reprinted with permission. Copyright @ Southwest Research Institute..
.’, .
F- 8-12. Hydraulic Ram Fressums Recorded Using Underwater Blast Gages Cemented to an AIu- 9
tiumWW With a Biaxial Straih Gage on the Outside (Ref.’ 12)

8-10
 Downloaded from http://www.everyspec.com

1 6 I I d 20.m
.*--
,~
w
,,
,1 ,
!:!”,
,
-
on the iet exit waU of the fuel cell were measured in a seri=
of- shaped-charge shots (Ref. 3). Initially, the pressures,
shown on Fig. 8-13, were measured using Susquehanna
underwater tourmaline pressuretransducersattached to the
I
fuel cdl walls. The transduc~ however, were physically
disassembled by the very strong impulse. These tourrnaline
transducers were replaced by a PCB ballistic transducer first
(designtd to measure gun chamber pressures) and a PCB
Model I02A03 piezoelectric pressure transducer later. These
:1 0

transducers were usually emplaced in the access port cover 1

on the t%el cells as seen on Fig. 8-3(A). The hydraulic ram
~+oo
2 4 e 8 tc
pressures measured by the piezoelectric pressure transducers
Tbnains
varied from 46.9 to 78.5 MPa (6803 to 11,384 psi). In three
of these tests the shaped-charge slug did not enter the fuel Figure 8-14. Hydraulic Ram Pmssums in a Fuel
cell. ‘he hydraulic ram pressures recorded for these three Cell Impacted by a Shaped-Charge Jet M=-
tests had a low of 46.9 MPa (6803 psi), a high of 52.2 MPa sumd WM a PiezOelec&ic Prewum lkarLs-
(7679 psi), and a mean of 48.5 MPa (7126 psi). In 13 tests ducer (Ref. 3)
the slug and the jet entered the he] cell. In these tests there
was a low of 47.9 MPa (7034 psi), a high of 78.5 MPa
(11,384 psi), shown on Fig. 8-14, and a mean of 64.9 MPa
(9408 psi). No good correlation could be found between
@pm and distance from jet exit to pressure tmns-
ducer. lheplots shown on Figs. 8-13 and 8-14 wem made by
recording the pressure versus time data on a magnetic tape

,:;~’
o paper recorder, then digitizing the &m and documenting it on
by using an X-Y plotter. These same pressure-time
plots can be recorded from an oscilloscope by using a cam- - era For the test results shown in Fig. 8-14a PCB piezoelec-
tric pressure transducer was emplaced in the access port
} 20,0W
1 9 , I 1 cover on the jet exit side of the fiei cell. The jet exit was
approximately 305 mm (12 in.) from the pressure transducer
diaphragm. me second pressure peak shown k-due to the
addition of reflected shock waves, but such pressures are too
variable to be used for design. Whh knowledge of these
impulsive loads a designer can better design a liquid con-
tainer to prevent gross rupture when a shaped-charge jet
impacts it.
There are many means available (Some of these are
shows on Fig. 8- 15.) by which to acquire these data and doc-
ument them. me underwater blast gage in Fig. 8-15(C)
~+Q.rm proved to be too delicate for hydraulic ram determinations
a. 10 when shaped-charge jets paSS through fuel “cells; however, a
rinq m device that should be sturdy enough for this purpose is cur-
. Pressures recorded after the first 2 ma. are often not acctt- rently being developed (Ref. 16). The underwater tourma-
rate. The underwater pressure Wm.sducer was cemented to line transducers, which were disassembled by the turbulence
the inside surface of ttte fuel cell on the jet entfy side approx-
incident to jet-liquid interactions, were easily reassembled
irnatety 102 mm (4 in.) from the jet impact point.
and functioned properly aftmwmd.
On occasion, the effect of bydmulic ram can be assessed
F- 8-13. Hy&udic Ram I%sures From a
by the posttest condition of some hardware within the fuel
Shaped-Charge Jet Passing Through a Fuel ceU, as shown in F]g. 8-16 by the crushed the fuel feed line
Cell Measured WRh an Underwater Iksum wirhin an integraI wing fuel cell. “

8-11
 Downloaded from http://www.everyspec.com

MIL-HDBK-684
,.:
Standa~d AN 49195 Connector*
~Stainless Steel Housing
\“”
Acoustic Center
Bonded Neoprene
4
16mm (0.63 in.) dia _ - “. [~ - ~ : I \
.-

63,5 mm. I
~1 (2.50 in.)~~~~o~n~ “4 ,.

*’Connector Not Waterproof

Reprinted with permission. Copyright GCelesco Industries, Inc.

(A) Celesco L~-33 Blast Pressure Transducer(Ref. 13) ~

.,. -’---. ... .

,.,
1 ‘ ~F?~ -

,.

Reprinted with permission. Copyright o PCB Piezotronics, Inc.

22.4 mm (0.88 in.) dia
Electrical
Connection a
-$
(B) Model 137A, Series Free Field Blast Pressure Probe
,’ (Former %squehanna:ivlodel ST-7 With Built-In Source Follower) (Ref. 14)
:,. -.
,-
Micro l-ined~ver 9.X mm
,,

Hermetic — -“
, ‘. 10-32 -
Micro \
Tygon ~
,.-. Sensor Oil Filled

..,’:
L . .
193mm
(7.6 in.)
I

Reprinted with permission. Copyright ‘oPCB Piezotronics, Inc.

,.
., (Q PCB 138A,-Series Underwater Tourmaline Blast Pressure Transducer
,,,:“-.. (Former Susquehanna Model No. PHI-7) (Ref. 15)
..
., F&q-e’ 8-15. Ikesswe Ilansducers

,,, .
,.. ,

8-12

..
 Downloaded from http://www.everyspec.com

MIL-HDBK-684

.- .-” - --- .- —-— 5--- -’ - -w--’ -- ~

I
“ Note: The instnrmentation is protected from bfast by a metal
shiefd (l). The pressure transducer mount (2) has a separate
ground base (3) from the box (4) simulating the vehicle.
(A) Isolation of Air Shock Transducer

I
1

-“}

TW limre 8-16. Collamed Fuel Line Wkthi.uAkcraft...

i%lg Integral
I&l cd (Ref. 17)
8-2.1.2 Air Blast or Shock Pressure Veins Time
Recordings
Theuse of piezoelectric pressure transducers has greatly
improved the fidelity of blast or shock wave pressure mea- (6) Relation of Air Shock Transducer to Test Fuel Cdl
sr&ments in air. dcilloscope photographs ‘of the shock ..
Figure 6-17. Hezoeledt-ic ~ Tkm.sclucer
P~ from the passage of a shaped-charge jet through a
test fixture are Fig. S-15 (Ref. 3). Pencil gag= were used
Nlountesl k $-tion Plate for Tkst Fixture
either Celesco Model LC-33 blast pressure transducers (Fig. Air shock PmSStm% w~ons (Ref,-18)
8-15(A)) or IW13 Model 137A free field blast pressure
proks Fig. 8-15(B)). These gages are somewhat timited flat surf= in the plane of the diaphragm and in ail direc-
because the gage has to be directed.toward the source of the tions around the diaphragm to assure the. sensing of the
shock wave. Otherv&e the fidelity of the pressure bing . ..
dynamic (stagnation) pressure.
sensed kreases, and the gage will not sense a true side-on
pressure. This orientation requirement means that the shocks 6-2.13. Recording Tempem~ Verstts Time “.
from reflections, which can be seen on Fig. S-! 5, may be Heat is a nebulous quantiry to measure. Heat is not mea-
greater or lesser than those recorded depending upon the sured; the effect that heat has on an objec~ i.e., the tempera-
direction tim which they came. ture of the objeet, is measured indirectly by the volume a
To alleviate this orientation problem a piezoeleetric pres- fluid fills or by pyrometers, which mtasure the voltage
sure transducer can be centered in a stagnation plate, shown across a dissimilar metal junction, the electrical resistance of
in Fig. 8-17. This type of &vice senses the normal compo- a material, or the emitted light. Alf of these phenomena take
nent of all incident pressure, as illustrated in Fig. 5-17, for time to become evident and do so through a finite volume.
effeetive pressure received by a crewman’s ears. A good Also that volume will not beat a single tempe.rarure through-
rule of thumb is that the stagnation plate should provide the out; therefore, a measured “temperature” should be the aver-
distance of approximately ten transducer diaphragms from a age of the temperatures throughout the volume. The test

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MIL;~DBK-684 :
instrumentation shown in Fig. 8-3(A) uses five. thermocou- 4. To establish the’ expected duration of operation of
pies to attempt to obtriin a mean temperature. Ch~gei in the
measured “temperature” take time to occur. This time is a
.. n.fimction of the nature of the heat transfer that takes place, the -
specific components given a fire in their compartment
5. To establish the rates at which specific materials,
e.g., mobility fuel,. hydraulic fluid, and explosives, will heat
● r

area through which this heat tiansfer is occurring, the ther- in either sustained vehicular operation.or the event of vehic-
mal capacitance and mass of the material being heated, the ular fires.
difference in temperature between the heat source and tine To select fire sensors or detect heat inputs into magazine
material, and the loss of heat from the material. There tie walls, time in the seconds or even minutes range can be
three processes for ‘heat transmission: radiation conductio~, used. A faster-device-such as an intrusion or penetration
and convection. Convection is the trimsfer of heat by the detector (break .wire device) (See subpar. 6-4. 1.) can be used
combined mechanisms of fluid mixing’arid conduction. (Ref. to detect penetrations that may cause a fire. The time
19) Heat transfer by radiation is faster than by conducting response requirement for fire-retardant insulation, for the
(Radiant heat transfer occurs at the speed of lig~t), but radi- operational times of components, and for the rate of burning
- ant heat transfer is a function of the difference’ between the of materials is also in the. seconds range. Therefore, for all
absolute temperatures of the donor arid acceptor each taken practical purposes,. thermocouples provide an adequate
to the fourth power. There must be a ~eat difference in abso-. response. They are described in subpar. 6-3.2. Thermocou-
lute temperatiues, as described in subpar. 5-2.1.2.1.1, before ples “we inadequate for immediate detection of a hydrocar-
this means of heat @ansfer is greatly effective. Yost of the bon fireball that may cause crew bums if sustained.
heat transfer addressed in this handbook is by conduction. To The main advantages of a thermocouple are that it is sim-
measure heat transfemed by conduction, either a voltage gen-. ple, rugged (compared to other temperature-sensing
eration device, i.e., thermocouple; or a change of resistance devices), and cw cover an extensive temperature range.’l%e
device, i.e., a thermistor, can be used. Thewolume change main disadvantage is that a thermocouple is slow compared
- device; i.e:, thermometer, and other, devices, such as.a bime-.. to a piezoelectric pressure transducer but so are-most-other
., tallic probe or coil; have been omitted because they are not temperature-sensing devices. An important advantage is that
,.
.’ suited to high-speed recording. The thermocouple is usable thermocouples can k easily fabricated by the technicians at
“over a greater range of temperatures with which the engineer a test site using a simple welding device. A thermocouple
,..
,, is concerned than the therrnistou see Figs. 6-15 and 6-26. To responds to temperature wherever j unctions are formed, usu-
obtain a very fast response, a bare, butt-welded thermocou- ally only at the bead. In .a large target it is necessary to
ple (Fig. *27(A)), a beaded type with a small head (Fig. 6- - employ a large number of thermocouples, each with its own a
.27(C)), or’s thin film thermocouple (described in”subpar. 6- record@g device. On the other hand, temperature is a point
, 3.3. 1) is needed. The smaller the bead, however; the finer the phenomenon and is subject to change whenever heat sources
1,
‘, . .. wire. Thus fabrication is more difficult, and”the fine wire pro- and/or heat sinks vary, and even when the heat source and
~ vides an extremely sensitive device that is highly subject to heat sink each remain constant, the “temperature” of a single
,, being damaged. A pyrometer is usefpl when temperatures body will vary within the body.
1, are too high to use thermocouples.
8-2.1.3.2 Thermistors
There are many types of temperature-sensing’ devices, but
for most recording of temperature in tests, an engineer need Another temperature-sensing- device that can be used is a
~ ‘“
,, consider only two, the thermocouple and the thermistor. Heat thermistor or THERMal resISTOR. A thermistor is. a
flux sensors have been used -to determine whether sufficient ceramic material (a semiconductor) whose elecrncal resis-
,, heat is received by a bodyat a given location to cause a burn, tance changes with temperature (Ref. 20). Thermistors, like
but this device is essentially a specialized use of a thermo- thermocouples, are used in bridge circuits to provide an
couple. error signal that is a measure of the temperature to which
,“ the thermistor is exposed. Thermistors have a greater gain
8.2.1.3.1 The~ocouples .” than thermocouples; that is,. the change of. signal with
There has been much controversy about whether a tier-~ change of temperature (AR/A7) k greater than it is for a
mocouple has as fast a response as a piezoelectric pressure thermocouple (AV/AT) where R. = resistance, T= tempera-
..
transducer. It does not, but is that fast a response for temper- ture, and V = voltage. The temperature range of the ther-
ature needed when designing a combat vehicle for fire sur-” mistor, however, is corresponding y smaller (as shown on
viability? For what purposes is the’”information needed? Fig. 6-15). Also the output of the thermistor versus temper-
These purposes are ate is not as Iinem “as that of a thermocouple. The time
1. To establish the potential haizirds to occupants ., response of the thermistor is approximately the same as that
.,,----- 2. To select or design fire sensors for the troop corn- .. of a thermocouple; again, a volume of material must have
partinent, the engine compartment, and vehicular magazines heat transferred. into or out of it for its average elecrnc
3. To establish which items need fire-retardant or ther- resistance to change. A thermistor is more delicate than a
*
. . mal insulation coverings thermocouple, i.e.? the thermistor can be more easily dam-

8-14
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o
#
,,,
-ot mated
aged by heat as well as by mechanical imPacL lhmnistors
be f~ -
a test site. llermistors
easii y, especially not by technicians at
require more knowledgeable and/or
., -..!.

- ~ --experiend imrtmtentation personnel than thermocouples

to obtain valid temperature determinations. Thermistors are
Themtocoup!e to Measure
recommended where temperature must be established more
Tempemture Historyof Slug
precisely.
(A) Section Through Typical Slug-Type
8-2.1.3S Heat Flux Sensors Heat Flux Transducer
Ha flux sensors have been used to quant@ the heat
received by an animal that redted in a given burn, and they
are being used in current tests to establish the potential for a
person to receive a bum. There am four basic vtiations of
heat flux sensors that are most often used. ‘1’hese types are
shown on Fig. 8-18. ‘Ike sensors must be selected based
upon several factors; the mode of heat transfer, the tempera- I.k]gJ@J@@
ture range involved, the heat transfer rate, and the time (B) Sedon Through Typical Thin-Foil-Type
involved are probably the most important factors in this .- Heat Flux Transducer
application. The important application for the purposes of
rhis handbook is to establish tie probability of a crewman’s HotJuncLions on

-5
being exposed to enough heat to receive a skin burn. The TOpofThermal
modes of heat transfer involved in this application are radia- 8anier (War)
tion, convection conduction (when a hot droplet of liquid . ..
impacts), andh the combination of the three when a fireball H2atsirtk--- -—-
of burning liquid spray engulfs a person. This is a much CofdJurtctions on 8ottmn
more complex situation than most heat flux applications.
The geatest challenge is to calibrate the heat flux sensor to
account for the total heat flux. Calibration is usually accorn-- (C) Pictorial Mew of Wafer-Type Thermopile
plished by a combination of measurement and analysis. Heat Flux Transducer
The capacity element of the slug-type heat flux sensor,
Fig. 8-18(A), is a heat-receiving mass that is usually in the
form of a copper cyii.nder and the outer surface has been
blackened to increase its absorptivity. This slug is embedded
in thermal insulation and. has a thermocouple embedded in
the center of the unexposed; or inner, face. l%e heat flux Q is
propcationrd to the rate of rise of the slug ternpmrure. S1ug-
type sensors are generally inaccumte because of the practical .,
difficulty in insulating the slug perfectly fkom its surround-
ings. T%e slug-type sensor is good for short duration heat
flux inputs and has a very fast response, but irs use is
restricted to applications whose total test time is in millisec-
onds. This type of sensor is useful for establishing transient
heat transfer but is not capable of measuring steady state
w
(0) SectionThroughTypicalThin-Film-Type ----
heat flux.
Heat FluxTransducer
‘llte thin foil-or membrane-type heat-flux sensor, which is
Reprinted by permission Copyright 01972, Instmment Society of
illustrated in Fig. 8-18@), is usually a constantan membrane America. Fmm 1S4 Transahcer Compendium, Second Edition.
wtached on its periphery to a copper mass, and a copper lead
is attached to the center of the membrane. The thermocou- Figure 8-18. Heat Flux Senscm (Ref. 21)
ples are the junctions of the constantan and copper at the been manufactured that can measure up to 34.05 MW/m2
center and around the periphery of the membrane. The ther- (3000 Btd(ftz.s)). Continuous time-varying measurements
mocouple output is a function of the differential temperarurr. can be made easily. A 63% response time is in the range of
between the center (hot junction) and the periphery of the 50 to 500 ms. Most thin foil sensors are limited to a temper-
membrane (cold junction), which is a fimction of the heat

o
,! ,, ffow from the membrane to the sink (tie copper mass). The
~~
sensory output can have a range of O to 10 mV. Sensors have
-ature range of -45°C to 230°C Water~ooIed sensors are
also available.
The thermopile-type sensor is shown in fig. 8-18(C). The

8-15
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WA-IDBK-684
hotjunctiorts are exposed to the heat, and the cold junctions that must be solved to ass~e...tatat the chemical species (and
are buried in the heat sink below the thermal bfier. The their concentrations) do not change during the sampling pro-
t.kermopile output voltage is proportional to, ~e, heat flux. cess. An extensive survey of this subject is given in the a
‘l%is ~pe.of sensor is ideal for measurement of low convec- American Society for Testing and Materials (ASTM) E 800,
tive heat transfer rates from low-temperature, gases. Bot?z Standard Guide for Measurement of Gases Present or
water-cooled and uncooled types of sensors $re available. Generated During Fires (Ref. 22). h-t many cases; spe-
Heat flux rates from very low to 227 kW/rn2 (20 Btu/(ft2.s)) cially designed sampling probes and instrum”entation are
can remeasured with a 63910response time ranging from 250- required for the unique environment of a fire. Transport of
ms to several seconds: ‘he zimximum operating temperature- reactive gases;-..g.,.hydrogengen chloride, through long~sam-
s 180”C (356”F). pling lines is discouraged. Afire or explosion in an enclosed
The thin-film sensor, Fig. 8-18(D), has a t@n, resistive, vehicle presents some additional problems due to the likely --~
temperature-sensitive film deposited on a qu$rtz or glass press~e buildup. Sampling lines, vessels, and other test
subs,mate. The elecrncal resistance of the film varies propor- equipment must be designed to withstand these stresses. A
tionally with surface temperature. The’ temperature can be fire in a combat vehicle is an obvious and immediate prob-
related to heat flux through a complex computer analysis. lem. The hazards from toxic. gases resulting from such a fire
Th$ device has a very fast response. The usable temperature- may’ not be so obvious,
,. however, because of low concentra-
range is dependent upon the film material used. .tion and/or lack of odor. Development of gas monitors for
All of these heat flux sensors must be calibrated to provide use in vehicles during actual operation may be advisable.*
a heat flux Q in terms of For example, there are small, commercially available detec-
,.,. tors for carbon monoxide that sound an alarm at low levels
Q = Ce, W/in’ ‘ (8-1) (gene~lly 400 ppm), which could be haiardous if breathed
over long periods of.time.
where ;
C = calibration constant, (W/m?)/mV 8-2.2.1 Fuel and Exfinguisbrtt Vapors
~~e = the output of the thermocouple; mV. me presence of volatilized fuel or unburned hydrocar-
bons in a vehicle. after a tire or munition impact poses a
The tin-film heat flux sensor is better adapted to establish- threat of further fire or explosion. Although these vapors are
ing transient flux. generally not lethal or even acutely toxic, their measurement
indicates the possibility of a hazard to the crew tlom fire or a
explosion. Today there are instruments available to deter-
8-2.2 GAS CONCENTRATION
mine selected gas concentrations inside vehicles.
Measurement of gas concentrations during full-scale test- Measurement of fuel vapors can be accomplished by
ing is intended to serve several purposes. These data are cru- atmosphere sampling and common laboratory analytical
cial to evaluate the toxic hazards due to the products of a fire techniques, such as gas chromatography.. Such techniques
inside a combat vehicle. Such. hazardS are related to the con’- are the same as those described for hydroc~bon vapors in
centrations of the important chemical species (generally subpar. 8-2.2.2. The &ta must be compared with the com-
gases), the to~cities of theSe specieq;and the time Of exPO-. -L--.bustibihty ~ts for tie type of hydrocarbon vapors, and
sure of the stibjects. The detection of lethal gases, as welj as consideration given to the likelihood an ignition source is
those that ~ght produce. toxic effects other than lethality, present.’
e.g., sensory or pulmonary irritation, is necessary. These Release of a fire extinguishant should be measured in real
gases may be produced by either pyrolysis. or combustion of time or by periodic sampling and followed with analysis by
the substances burnirig or by the extinguishant itself. Of sec- gas chromatography or mass spectrometry or other tech-
ondary irrtpoz&nce is the measurement of fuel vapors which niques.. Presence of certiin extinguishing agents within a
may contribute to continued burning or subsequent reigni- given concentration range may preclude a fire ffom reignit-
tion. Devices that sample the air from within the vehicle on a ing. However, the possible toxic effects of the extinguishant
fairly timely basis are described in subpar. .6-4:3. , and its ‘pyrolysis by-products will need to be identified.
It is not necessary to analyze all of the products of afire;
in facg it is nearly impossible to do so. It is most important to 8-2.2.2 Fire By-l?roducts
characterize those products that pose a risk to. life or to the Some of the by-products of a fire are potentially toxic,
appropriate. functioning of the individuals in the. vehicle. perhaps even lethal in larga doses. Thus analyses of these
Animal subjects are often used in an effort to assess the species (generally gases) are crucial to evaluation of the
effects of we combination of toxic products rather than to
attempt to model, i.e., predict, the biological effects based *Such monitors could be integrated with the nuclear, biological,
solely on chemical analyses. The sampling of gases and and chemical (NBC) system, but basically the monitoring and alter-
aerosols from, a fire environment creates unique problems ing of “the content of the air within a combat vehicle is an environ- 0
mental-air conditioning-problem, not a chemical warfare one.

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MIL-HDBK-684

.. survivability of zm.individual to these fire by-products. Dti- lection for attalysk, this - pref~le for a large fire or
~i~, ferent types of chemical reactions, even with the same explosion in a confined space. Direct sampling can be repre-
,,’
,:, material, do not necessarily produce the same products. For . sented by a collector directly in the fire atmosphere this type
o
“. - ‘example; detonation of RDX produces 0.6 moles per kg of is advisable for collection of reactive gases, such as the
CO, 6.6 moles per kg of C~, 0.8 moles per kg of NH~ hydrogen halides. Thus sampling gases from a test fire envi-
(ammonia), and 3.1 moles per kg of HZO (Ref. 23), whereas ronment in a combat vehicle may include the following:
deflagration of RDX produces 8.0 moles per kg of CO, 5.5 1. Remote continuous analyzers may be usexl to meas-
moles pex kg of CO= 2.8 moles per kg of N1-$, and 8.0 ure selected nonreactive and noncondensable gases. For
moles per kg of HZO (Ref. 24). In an enclosed environment example, commercially ‘available, nondispersive, -infrared
such as a combat vehicle, tie toxic effects of the gases may instruments are very uset%l for measuring carbon monoxide
be exerted over relatively long periods of time because the or carbon dioxide. When this type of analyzer is available, it
occupants are confined within the vehicle. These toxic would be the preferred choice.
effects are dependent on both the concentration of the spe- 2. Remote-batch analyzers that entail noncontinuous
cies and the time of exposure of tie subjecq thetefo~ it is . . sampling and labomto~ analyses, e.g., gas or solution &ro-
- “necessary that’ the toxic gaseous species be identified and matography with an automatic or semiautomatic sampling
that their concentrations as functions of time during and system, may be used for most of the gases of interesL e.g.,
after a fire he determined. With this information an assess- CO, COZ, HCN, hydrocarbons, and aldehydes. Gas chroma-
~ ment of the toxic hazards due to these species can be made, tography can also be used in conjunction with direct grab
as was done in Ref. 25 for Halon 1301. sampiing. This type of instrumentation is commonly avail-
Specialized sampling and analysis systems exist for many able in laboratories and is applicable to a broad range of
- of the common &e by-products, including carbon monox- chemical species. However, it has a significant disadvantage
ide, carbon dioxide, hydrogen cyanide: hydrogen halides because many samples must be obtained in order to be able
(HCl, I-IBr, and ElF), nitrogen oxides (NO~, su.tfur oxides. . to describe a concentration-time curve. Othm specilic types
(SO~, txubonyl suM&, organic aldehydes, and hydrocar-- of analysis of batch samples may include titration, calorime-
bons, as well as oxygen, water, and nitrogen. In some cases try, and ion+elective electrode methods, which are listed in
continuous or semicontinuous analysis of the particular gas Table 8-1.
of interest may be obtaind in other cases, however, only 3. Several types of direct batch sampling probes are
intermittent analyses are possible. Each sampling and analy- available that permit collection and holdlng of a sample of
sis system has its advantages and disadvantages for applica- the atmosphere with essentially no sampling line ahead of
tion to any particular fire scenario. the collector, One type involves solid sodalime, or caustic
Titble 8-1 has been abstracted tim ASTM E 800, Stan- solution, sampling tubes, which are referenced in Section 7.3
dard Guide forhlea.wmnent of Gores Present or Gen- of ASTM E 800. This type is particularly useful for sampling
erated During Fires (Ref. 22). It contains a summary of reactive gases, such as hydrogen Mldes, that might be lost
the methods of sampling-and analysis for the g- of pri- due to reaction or condensation in sampling lines. Subse-
mary concern in ~. The table conrains references to sec- quent analyses usually involve titmtion or, ion chromatogra-
tions in the text of the standard that contain further phy. The other type of directbatch sampling is a “grab”
discussion. The following information is intended to supple- sample of the atmosphere. ‘l’his generally consists of an
ment that provided in the standard and to include discussion evacuated bulb, a plastic bag, or a gas-tight syringe to collect
of the unique situation of lire in a combat vehicle. a known volume of the test atmosphere. Subsequent analyses
Many analytical techniques can IR used to analyze the fire might be conducted using gas or liquid chromatography. M
by-products of interesL provided that interferences, such as of these batch methods require multiple samples in order to
further reactions within the sampling system, are taken into describe a concentration-time curve. In practice, a tester
‘consideration ancf that the appropriate ranges of concentra- would set up many samplers in the same location inside the
tions are accommodated. The most critical aspect of mti- test environment and actuate valves remotely in order to acti-”
surement of b by-products is sampling. (See Section 5, vate each sampler ar a precise time during the experiment.
“Sampling”, in ASTM E 800 for a detailed discussion of the Measurement of the gases present during a fire in a simu-
problems of sampling fire atmospheres,) lated combat vehicle R a difficult task Stairdess steel sam-
Listed in Table 8-1 are the two basic modes for sktpling pling prols have to be located at key sites within the
fire atmospher~, batch and continuous. Batch refem to a volume of the “vehicle”. Numerous proks may be necessary
sample obtained over some paid whether it is 30s or the at each site in order to analyze all of the key gases for an
entire run. Continuous refers to a continuous measure of the extended time period. Several different types of analyzers
concentration of the species for the duration of the experi- are necessmy to provide the appropriate charactaization of
ment. ‘lltese two modes may be further subdivided into the gases of interes~ It is impractical and unn~ to
,1J;,
, ;!1!;$remote and direct sampling. Remote sampling entails a attempt to analyze all of the gases produced in a fir~ how-
0
transfer line fkom the point of sampling to the point of col- ever, it is essential to characterize properly the important

8-17
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Downloaded from http://www.everyspec.com

MIL-HDBIG684
.“”, .,
TIWLE 8-L. SUMNLARY OF~ALYT!CAL ~THODS F6R FIIULGASES (Ref. 22)

METHOD* SPECIES** ..’ S~PLING MODET INT’ERFERENCES/LIMITATIONS

Gh Chomato~aphy CO,
~ COZ, 02, Nz Batch ~ No single column will resolve all four spe-
.-
Batch ties.
‘ I-ICN ; Batch NOTcommonly used
Hydrocarbons: Batch See Ref. 21.
Suitability to mixtures of hydrocarbons
Aldehydes Batch depends on calibration.
.,
,, See Ref. 21.

Ion Chroniatography x Batch, solution Specific detector and conditions required

N02, NOj Batch, solution .‘ Specific detector and conditions requtied

Infrared co, co~ Continuous or batch Continuous mode usually limited to analy-
sis of one species; batch mode not limited
Hx Continuous Technique utider development
HCN ‘. Continuous Tgzhnique under development
so~ Continuous - tt
Hydrocarbons ~ Con~inuous Not very accurate for mixtures of hydrocar-
,, bons

Ion-Selective. Electrodes. x. Batch or continuous, - Cyanide, sulfide, and other halides can.
.-
solution interfere; each elec~ode specific to that
... .
CN Batch or continuous, species
,.
solution Cyanide, sulfide, and other halides can
interfere; each elec~ode specific to that
species

Electrochemical co Continuous Relatively slow

Methods: Hx Continuous, solution Nonspecific
O~dation HCN -.” Continuous, soh.ttion Interference from H$
Conductometric NOX Continuous Large sampling volumes
Arnperomernc ‘ HCN. .’ Batch, solution Limited to low concentrations
Cherniluminescent ‘ Acrolein Batch, solution Limited to low concentrations
Determines total acid gas componenc i.e.,
anything that will remove or pickup proton
in solution

Titrimetric Procedures HX” Batch or,continuous, Not commonly used

solution
,, I-ICN Batch, solution Igtereference from halide ions

Gas Analysis Tubes co, co*,o~ Batch, ~~~ Only setniquantitative; HC1 tube very lim-
(C’pulltubes”) Hcl -,,. . ited
HCN
,,
*This list is not exhaustive,
**X = halide (F, Cl, Br, I) “”
I
SOX= sulfur oxides (S02, S03)
NOX= ni@ogen oxides (NO, N02)
t“Batch” refers to a sample obtained over some periixl (whether it be 30s or the entirenrn). “Continuous” refers to a continuous measure of
the species’ concentration for the duration of the experiment. “Solution” means that the species must be absorbed into solution in order to be
measured.
ttNo remarks -
Copyright ASTM. Reprinted with permission:

8-18
 Downloaded from http://www.everyspec.com

MIL-HDBK-684
.. toxic by-products. The key gases depend somewhat on the defective. The chemical analysis of these particles was sur-
,r, materials and products exposed to the fire (as detailed in pm prising~e panicles were a carbohydrate, resembling
,;{;~
vious chapters). In all fires measurement of carbon monox- breakfast ceti. The test conductor remembered that person-
o
- . ik carbon dioxide, and oxygen has become routine and nel at the government agency which had furnished the car-
necessary. In many fires measurement of HCN is essential.’ rndges had a policy to fill the space between the propdlant
Likewise, analysis of I-ICI, HBr, and HF must be done when and the bullet of off-loaded cmtridges witi Cream of Wheat.
their presence is suspected based on the types of materials Therefore, all remaining cartridges were examined for pro-
being burned or the possible by-products from the extinguis- pellant loads, i.e., the bullets were pulled and the propellant
hant being used. &ld&S of SpCCifiC aldehydes, hydrocar- charges weighed.-and:exam.ined Approximately- ei~- off-
bon vapors, nitrogen and sullkr oxides, carbonyl sulfide,. loaded cartridges inadvertently had been included in a ship
etc., may be undertaken as deemed necesstuy, but they are ment of fifty 14.5-mrn cartridges. However, sufficient instru-
too expensive for most routine experimentation. mentation had been used, including wimess sheets, to
establish just what had happenm and this diagnosis, or at
8-X3 EXTINGUISHING-SYSTEM EVENT least the identification of an abnormality and the gathering of
TIMING
evidence, took place a few minutes after the test was per-
For test and design personnel to develop a fire-extinguish- fomted (’Ref. 26). Test personnel must be alert to any abnor-
ing system, they must be able to relate events that have mality or discrepancy and must check such at the time of the
occwred with the threaL the test specimen, the combustion test.
reactions and the fire-extinguishing system. All of these. In another program intended to establish the capability of
events or reactions must be established for their time of antimisting fuel to resist ignition or sustained combustion,
occurrence relative to each other. Insaumentation must be the reaction of the target fuel cell and the fuel to tie impactof
selectd that has the capability to discern the naiure of Ihe. a 23-mm high-explosive incendiary tracer (I-EIT) projectile
event and its relative time of occummce. .. seemed remarkably subdued. The tests were performed to
8-23.1 Thkeat Functioning simulate an attack aimraft receiving a grourtd-teair antiair-
craft projectile hit as the akcraft was climbing after a stra6ng
Usuallythe test and design personnel know how threats
run. The test installation is shown in Fig. 8-19. The chrono-
fiction and what target response can be expected; however,
graph system mounted on the muzzle of the main gun
,,,,, test pxs.onnel should always verify that the thrkat has func-
showed that the projectile was at the desired velocity. One of
i“If tioned as expected and be able to relate threat effect to target
0 the test technicians noticed that some bright object had come
response. Sometimes the threat does not function as
from the target area and landed over by the wind machine.
expected, and threat malfunction must be diagnosed. Most
After the area was declared safe, he investigated and discov-
threats are of foreign manufacture and often cannot be disas-
ered that the object was a sizable part of the body of ,the pro-
sembled to establish whether they are properly fabricated
jectile. ‘Ilk identification led to a fhrther evaluation of the
and assembled. Many of these threats have been acquired by
subdued projectile-target interaction, whicli. proved to be
one govem.ment agency and have been passed through other
caused by an unsuspected projectile weakness. (Ref. 27) This
agencies before being received by the user. In one instance, a
number of 14.S~ APIT ca&idges were received that -- test demonstrates
. ----- - that observant test pemonnel, who check
out unusual happenings and bring them to the attention of the
were reputedly unmodified, and none appeared to have been
test director, are a form of insrmmentation that is extremely
modified. Several of these cartridges were used in tests, all
valuable, It alSO shows that remnants of the bat are them-
functioned properly, and the chronograph syste~ used&tab-
selves a reliable indicator of threat performance. “I%e frag-
IiShed the expected near-muxxIe* velocities. In the test to
ments shown in Fig. 8-20 were all collected during this same
establish the reaction of an exmrnal fuel cell for the FA-1 S
series of tests. Fragments shown in Fig. 8-20 show that two
aircmft to the impact of a’%dly tumbled” 14.5-mm bulle~
different mechanisms were involv@@ their fomnation. Frag-
the target performed as expecti but the chronogmph sys-.
ments on Fig. 8-20(B) ‘were formed by a normal detonation
mm indicated a much slower than desired muxzle velocity.
of a 23-mm HEIT projectile. The figment shown on Fig. 8-
The ‘humble” was not ‘YiW’ enough. Examination of wit-
20(C) was formed when the projectile failed mechanically
ness sheets, emplaced to monitor the tumbling of the bulle~
after it hit a hard object and then split or mushroomed Frag-
showed that the bulIer was accompanied by many small par-
ments on Fig. 8-20(A) show evidence of both failure mecha-
ticles part of the way to the target. Some of these particles
nisms; they were failing mechanically and then apparently
were recovered and examined for chemical composition
explosively when the charge detonated. For this dual failure
because the test personnel thought there was a possibility
to occur, the mechanical failure had to occur before the fuze
that the propellant of this foreign Cartridgemight have been
delay ended but the mechanical breakup of the projectile
was ‘not complete enough to disrupt the explosive train. Thus
me velocity established using a chronograph screen array is not
tbe velocity of the projectile as it passes through the plane of the failures of the threat to function properly can be diagnosed
muzrie of the weapon; it is the velocity esablisbed near the nwzzie. ffom examination of projectile fragments.

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MIL-HDBK-684
... . Thre:;$;-&peed
Movable ‘
Integral Wing Fuel Cell I 2 3 .. ..1.. .l BackstoD

Fbsh Detectorand -”
- ..--.-..,
Chronograph Screen Array ‘= Storage Unit (Of
Figure 8-19. Installation Showvi& T* Sp@nens, Mann Gq and Wmd Machine (Ref. 27)

Proper threat functioning can be observed ~om viewing Abnormalities in, or abrupt cessation of, strain gage or pres-
motion pictures, from recordings of blast gages or light sen- - ~~ - sure data (e.g., me extraneous blip on Fig. 5-15(B)) or signal
sorsj or from target damage. “Time of arrival of a projectile - saturation (e.g.; the strain gages o,? Fig. 8-10) can provide
impacting a target “can be obtained from an, impact switch or.:. indications- of the time “at wiuch: some, phenomenon
an event timer. occqrred, such as an impact by an extraneous object (the”first
example) or when” the target failed (the second example).
8-2.3.2 Target Response
“The target response can be established by use of strain 8-2.3.3 combustion
gages, pressure gages, high-frame-rate motion pictures, and The time and location of ignition is probably best shown
posttest examination, Data from strain and pressure gages ---- in tigh-speed motion pictures. The duration of tie resulting o
can be recorded on a high-speed recorder. An exarhple of fire is. better shown on real-time motion pictures or videos
establishing the target response is on Fig.. 8-5(B), which unless the fire is of short enough duration to be recorded
clearly shows that the fuel cell failed when a large piece completely on the bigher frame rate films. Recordings of
broke out of the rear surface before be fuel cell was thrown temperatures can be of great value, particularly when smoke
off the shelf on which it was mounted (Refs., 3 and 7). obscures the motion pictures. Infrared Iihmor..videos can be
used when smoke precludes other methods.

.. ,

. .

,’
... ,.. .

. .,
,,,

(2)

(A) Initial Mechanical Fluptuye

(B) Detonation (C) Mechanical Rupture
Followed by Detonation

—
F~re 8-XI. Fragments Show@g Different Rupture Modes (Ref. 27)

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8-2.3.4 Eminguisher System performance With the more rapidly .occ.urting events the needs of the
Extinguisher system performance can be obtained by recording equipment may drive the test sequence. For exam-
recording sensor outputs, light or other electromagnetic radi- ple, when using a high-f+ame-rate motion picture camera
.. ation (emr) from selected locations, control signals to such as a Hycamg to obtain motion pictures at or over 5000
valves, extinguisher pressure, and temperature at selected hmes per second (ti/s), the camera must be ikaming pic-
hxations, all recorded vemms time. Motion pictures can also tures at the desired rate before the event occum. l%us a
show extinguishing even~ but smoke will ofl.en obscure switch that can trigger the event after sufficient film has been
some scenes or locations. expended for the camera to have reached the proper framing
rate is provided within .the.camera. Thus, the camerais not
8-2.3.S Correlation only an obsemer of events but also the sequencing driver.
The twomainsourcesof information are the motion pic-
8-2.4.1.1 Photographic Equipment
tures or videos and the recordings of electronic information,
such as pressures, temperatures, strain, or emr versus time. A great variety of photographic equipment is availabIe to
‘ihese can be correlated by recording the threat time of record rapidly occurring events. This type of equipment can
‘“ impact by means-of a switch that the threat closes. Tlte time provide a sequence of photographs.that can be viewed wi$t a
of impact is time zero and is recorded with the elecmonic projector on a screen, with a motion analyzer on a viewing
dam as shown on Fig. S-15 or on Fig. 8-12 on which time plate, or as a series of photographs. The development of
zero is indicated by a series of dots andlor in the motion pic- color filxn of ASA 400 or better and the gr~ter strength of
tures by having the switch energize a lamp that is-visible in Mylar-based film have e~ated the need to consider black
the motion pictures. For example, the Hycam~ provides a and white motion picmres. Color film provides far superior
time correlation feature. Other cameras may not. - pictures, especially for the analysis of ignition and combus-
tion processes.
8-2.4 ANCILLARY DATA The cameras range from the Beckman-Whitley Model 200
The reactions of materials to various loadings can be Simultaneous Streak and Ftarning Camera (Ref. 28)- in
understood and modeled mathematically when the phenom- which 35-mm film is placed on the inside surface of a rotat-
ena can be visualizd By knowing the sequence of actions able drum and achieves frame rates from 10,000 to

,,,,+:!
o beginning),
ji~$
and reactions from beginning to end (but particularly in the
the designer can deduce the causes and change
specific design features in order to alter the results.
8,800,CMI0 fds. through tie Hycam” (Ref. 29), which uses
reels of Id+n.tn film at framing rates to 11,000 fds, to the
Locam (Ref. 30), which fi-arnes id-mm film at framing rates
The ‘types of equipment used currently are either photo- to 500 fr/s. These three cameras have been selected to illus-
graphic or electronic. Photographic equipment can provide trate the range of photographic equipment available, no
still or motion pic~ whereas elexxronic equipment can attempt has been made to describe all available makes and
provide real-time videos or a series of still pictures taken at a models of cameras.
very rapid rate (image converters). Flash X-ray equipment is The Beckman-Whitley Model 200 supmts a relatively
- mentioned because it may be used in tests involving ignition short length of film on the inside surface of a relatively large
and combustion. The X rays do not effectively record corn-. drum. This 35-mm film is approximately 3 to 23 frames long.
- bustion andcan complicate the use of other equipment that - s.’l%e drum is rotated at a ve.tj high
-- speed. The camera func-
can record combustion or the use of other instrumentation, tions by either opening a slit for a streak picture and/or rotat-
but flash X-ray photographs are often desired ~ause they ing a prism for ffaming pictures. ‘l%e streak picture, Fig. 8-
provi& information not otherwise obtainable, such as close- 21, simply shows the rate of change of the quantity of light
in velocity determinations irnpactor attitude at impact and entering the s]iL The framing photographs, 13g. 8-22, show a
breakup, and projectile fragmentation patterns. series of pictures taken at a high rate of speed. The photo-
Ballistic tests of combat vehicles or their components are ‘ graphs in these two figures were taken at the same. tinte and
“ usually costly enough to warrant redundancy in the equip-. show a nonelecbic blasting.cap, i.e., the booster for a 23-mm
ment used to obtain pictorial&m. Such redundancy need not HEIT’ projectile, detonating. The framing rate of this camera
be two identical means; it can include difkrent equipment (Ref. 28) is vety high, iiom 10,000 to 8,800,000 Ms. me
viewing the test tlom different aspects. camera is driven to speed via a pneumatic turbine before the
lens is opened and uses one of five basic plug-in fkurting
8-2.4.1 Reeording of Rapidly Occuming Events
modules and one of three mirror ntrbiies to provide the
Rapidly occttrring events can be recorded using either frame rate desired. Test procedures are sequenced so the lens
photographic or electronic equipment. Both types of equip- is open for the event that is to h. recorded
ment are being improved rapidly. Some of the specific

,,,:11~~
o
equipment described is obsolescent or perhaps obsolete;
however, equipment that can produce at least equivalent
‘:“’” results is available.
. .

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MIL-HDBK-684
The Hycam’? uses:aroMting:prism andasegmented shut- ‘.
ter to frame pictures on film.; The film is fed from one reel to
another. The camera is powered electrically and uses a high e
current. (This high-current requirement, if not taken into
account, can iiffect other elecrncally powered instruments.
The power cable to the Hycam” should be isolated from
otler cifcuits.) The framing rate achieved is from a combina-
tion of reel size, power setting, and time of operation (See
Fig. S-23.), The camera requires time to come up to”speed,
so considerable footage will not contain photographs taken
at tie desired filming rate. For full-frame photographs the
maximum frame rate is 11,000 fr/s (Ref. 29). Thus when a
high framing rate is desired, the largest reel must be used,
i.e., 122 m (400 ft), and the camera must pass most of the
film past ~e Iensjust to get up to speed. To assure the event
is sequenced to occur at the proper time, a switch within the
camera. can be set to close after a desired length of film is on
the take-up reel. MS switch closure can be used to trigger an
event such as discharge of a gun or initiation of a blasting
cap. selected frwes from a motion picture, taken by a
I-Iycam” -using a $l~e rate of 1000 MS are shown in Fig 8-
24. When operated at a high frame rate (over 4000 fr/s), the
-Hycarne cannot be stopped to save film. Three mel sizescan
be used in a Hycam”, 30 m (100 ft), 61 m (200-ft), and 122 m
(400 ft). A Hycame has a rated ~nimum rate of 20 fr/s, but
it has somewhat poorer resolution that is caused by using a
rotating prism. Thus it does not operate as well below a
framing rate of 100 fr/s as either a Locam or a standard
motion picture camera. a

,.
(A) Frame 1 (B) Frame 2

figure 8-22. Frames of Detonation of the B&ster of a 23-mmHEIT Projectile

(cent’d on next page)
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MIL-HDBK-684

(C) Frame 3 (0) Frame 4

Figurt $22 (cctnt’d)

(A) Frame 1
.

2 6 8
Ekpsi3thime, s

(9) Frame 2
—.

-. -.

!a7sla173as2n =“-27s
Linear Footage,ft

FigwetW3.F raudngRateV kusElapsedTime

and Linear Footage for lilycam~lking a X22-m “Figure 8-2$. &F-&3uentid Frames
(400-ft) Reel (Ref. 30) From Motion Picture of Test No. 1 of Ref.
5
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.,
MII+DBK-684
The Locani is a variable rate motion pictie camera with a only “freezes”. m.o~on but almjncreases the requirement for
minimum fkuning rate of 16 fr/s and a miixirnurn framing light ,fiom the subject.
rate of 500 fr/s. Locams can be operated at the sthdard rate If the subject is not self-illuminated, high frame rate
a
., of.-24.fr/s.-They are shutter cameras, which direct light from motion pictures require additional illumination to activate
the scene directly onto the film rather than use light reflected - the film. When the dwell time is shortened, the light must be
b~ a prism (Ref. 30). more intense to obtain proper film activation. In southern
Both HycamsG and Locams have small lights that flash at Tex~ or Arizona the.”sun is an adequate source of light for
preset rates near the edge of the film to provide timing pips. fram.@g rates of approximately 2500 fr/s for much of the
Some Hycains” also have a second light, w~ch can be ~. year. If more’ light-is-needed;. banks of p~oto flood lights or
flashed on the other film edge to provide a time correlation sequenced banks of flash bulbs have been used successfully.
with some outside event such as projectile impact on the ~- A problem vdh banks of photo’ flood lights.is that they heat
get. This time correlation light must be ‘tiggered by an exter- the subject, The fl”~h bulbs heat the subject less, primarily ~
.- ‘;
nal signal. because they provide light for a shorter period of time. A
Each frame of a framing camera is a picture ~~ade by the ~. t~ searchlight was found to add a half f-stop of light. Addi-
deposition of light over a short peiiod:of time. Items that do tion~ ~llumination for Fig. 8-22 came from an exploding
not move during that period of time appear as sh~ images; bridgewire sprer@ evenly through a Fresnel lens. Some sub-
items that do. move appear as a blui. Fig. 8-$5 is from a jects are self-illuminating, such as the detonating 23-mm
motion picture taken by a Fastax (an earlier design of the HEIT projectile in Fig. 8-25.
Hycanf-’) at a rate of 8000 &/s. The short bti oflight seen in High-speed photography is a fairly costly operation in
Fig. 8-25(A) is the burning tracer of a 23-mm WIT projec- funds, time, and iabor. ‘13me is required to develop the films
.,.. .
tile that traveled approximately 114.3 mm (4.5 in.) during ~~:.and there is no instant playback. Excerpts from high frame
the time light was impregnating the film to produce the. rate motion pictties can be converted to video tapes for doc-
.,
frtie: The-higher the ‘framing rate, the ..shorter the dwell umentary purposes.
time for making a single picture: This shorter dwell time not When flas~ X-ray radiographs are desired, the test .i~stal-

.“

,.
1’
1.

...,

.....

(4) Frame 1 , (B) Frame 2

..,,

,.

(C) Frame 3 (D) Frame 4 —

Figure S-25. Sequential Pictures .of a 23-mm HEIT Perforating a Stainless Steel Target.

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MIL”HDBK-664

Iation is mom complicated because the cameras and their At present the only video.~~tem capable of rttrkng the
must not be in the X-ray beam. Flash X-ray radiographs equivalent of high frame rate motion pictures with full iiame
e in order to “see through” the opaque cloud of com- pictures is the Spin Physics (Eastman Kodak) Models
--- =.-bustionartd combustion products, e.g., Fig. 8-26*.(The fmg- EKTAPRO HMO ( 1000 Msec) artd SP 2000 (2000 fkh), but
rnents and the rearward ejected tracer can be seen readily in these produce black and white pictures only. These pictures
b radiograph whereas the light and products emitted by the are recorded on magnetic tape, and each point is recorded in
detonation would prevent an observer from seeing the tig- linear analog as one of 256 shades of grey. These can be
ments, as shown on Fig. 8-22.) played back in pseudocolor at the rtonnal 30 Ws using a
pseudocolor gerterworin which each shade of grey has-been
8-24.1.2 Electroitic Equipment assigned a color from yellow to red to blue or co~bimtions .
The image converter was an early version of electronic of these. This color assignment producm a video scenesim-
equipment used to make a series of sequenthil pictures at a ilar to that of acolonzed video tape of an old black and white
very fast rate. Fig. 2-12 is meries of pictures showing a steel motion picture.
fiagmern perforating a titanium sheet that was taken using an Eastman Kodidc is working on an age intensifiersystem
image converter. Basically, the image converter reproduced that magnifies light .up to 40,(M)0 times with an electronic
this same scene five times approximately 20 m apam The gaang (equivalent to shutter speed) of 1 M, which can be
limitation on this device was that five ties were the most recorded on a high-speed data tape traveling at approxi-
that could be made. Also the scene had to be backlighted mately 6.35 m/s (250 i,nJs). ‘i%is tape provides an equivalent
using a xenon Iight source to overcome the flash generated of a 10,000 fi/s of motion picture in black and white. Again
by the impact of the steel fragment on the titanium targeL this can be colorized using the pseudocolor generator for
(15g: 2-11 is a similar set of pictures of a fkagment impacting. playback This device would not require as much light as the
an aluminum sheet taken by an image converter.) other system.

8-2.4.13 Examples of High-Frame-Rdte Motion

Pictures ----
The motion pictures described in this subparagraph were
originally made in color, but the excerpts shown are-in black
and white. Two examples are shown to illustrate important
points.
In 1985P. Il. Zabel (Ref. 3) was tasked to adapt aircmft
fuel cell survivability techniques, such as those shown effec-
tive for helicopter fuel cells (Ref. 32), to lightly armored
ground vehicles and to demonstrate their enhanced sumiv-
ability. The first phase of this task was to review the then
current state of the an of lightly armored vehicle fuel cell
vulnerability. Even more important b the written reports
I werb the motion pictures that had been made during those
tests. l%ose motion pictures, some ties ,of which ~e
shown in Fig. 2-17, ckad y showed ~at the main source of
combustible fuel was the mist produced when the seams of
the fuel cells split. Those motion pictures also showed that
the jet exiting the vehicle produced the ignition sources that
A ignited the fuel mist Bmadfiadt (Ref. 33) had demonstrated
tit the actual fiel cells did not split at the seams-when hit by
a shaped-charge jet. Thus, in the program repomxl in Ref. 3,
care was exercised to fabricate fuel cells that would be more
representative of actual fuel cells. In this example the high
frame rate motion pictures that had been taken to establish
the relative characteristics of combustion of neat’ and 6re-
Fktm 6-26. Flash X Ray of Static Detonation of a resistant diesel fuels later provided the means to detect fuel
Z-mm HIIIT Projectile (IM 31) cell weaknesses and to e&iblish combustible tlel mist and
ignition source meeting. From these, design changes pro-
Whisftash Xrayisr4double exposm— t%s~ the intact projecdtewas duced the successful survivability enhancement demonstra-
Then the detonating projectile was superimposedby being x:
tion of fiel celi confinement in Ref. 3, as is described in
ed on the sameplate a desired number of microsecondsafter irtitia-
SUbpM. 7-3.2.9.1.

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,.

M14-tiDBK-684
‘A second example of the value of .high.frame rate motion ment’ in an actual engine.~Qmpartrnent should have been
pictures is from Ref. 18. In this program double-walled or much more rapid than in the empty test fixture.
jacketed fuel cells were examined in fair detail. One ques- High-frame-rate motion pictures provide extremely valu- ‘9
-: ‘~:’.’-.tion .that.arose was “Why does the dry powdered fire extin- able answers” to what occurred and when it occurred. Some-
.=~ishant, Purple K, take approximately twice, the time to times these answers can verifj’ the adequacy of the test
extinguish the fire ball as does water?”, The answer is shown installation, as happened when Zabel (Ref. 34) provided a
in Fig. 8-27,.an extract from the high ffame rate motion pic~ . thin wiridow of 625-mm (0:246-in.) acrylic over the fuel cell
ture tidcen of Test 10 of Ref. 18. The dark object’ seen travel; -ullage containing & explosive fuel vapor-air mixture when
. .
ing from the fuel cell, Fig. 8-27(C), to ,tie far wall of the test firing. a23-mm HJ3T-projectile into the fuel cell, Fig..2-lLAn
fixture is the ~le K launched as a single clQd.This clod ~~ obse~er had complained that the window was too thin and
impacts the far wall and then travels b,ack into the center of was blown away by the projectile detonation, which allowed
the test fixture as a cloud of powder, Fig. 8-27(H). Extin-. external air to mix with the ullage vapor and thus resulted in
guishment occurs as this cloud passes back through the fire, the explosion. Later examination of the HycamG motion pic-
ball. Therefore, in an actual vehicle with niaiiy objec~ ture, Fig. 2-8(J); showed that the ullage vapors had started
located within the engine compartment, such as w engine; burning and that “combustion was well beyond the explosion
tubes, wiies, and many other assorted objects, ‘this clod of stage before the window ruptured, Fig. 2-8(L). In short; the
tire extinguishant would have been broken up into, a cloud of window was not ruptured due to fragment impacq the ullage
powder long before reaching the far w*1. Hence extingqjsh: explosion ruptured the window, which admitted air that

,,,

. ...,,

.,,
‘e

.,

(A) Frame O,t=O-s

.. .

,.

,’.
,
,, (C) Frame 2, f= 0.001 s . “(D) Frame 3, t= 0.002s
,,
—
Figure
8-27.
Fire Extin@@t Purple K Disse@nation (Ref. 18)
,,’,
., . 8-26
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MIL-HDBK-684

{F) Frame 5, f= 0.004 S

..

..

-. ---- .

(H) Frame 47, t= 0.046s

27. (cent’d)

- 8-2.4Q Docu&enting Overall Test Events

l%eadagethata picture is worth a thousand words is not
only correct but possibly an understatement of the value of a
picture. A fact to remember is that tests conducted for one
Pq* tdy may provide the answer to a different problem
five, ten, or fifteen years horn now. Hopefully, we learn as
we work. Often, much can be learned from earlier work if it
is known just what was done with which instrumentation,
facilities, and fixmres. Terminology changes. Pictures pro-
vide much better understanding of past events or earlier
equipment than volumes of text- These pictures can be still
photographs, motion pictures, videompes, or other media of
recorded oictorial details. The ~eneral WUP of m or tie
and the intensity and duration of light generation. Caution general kiyout and composition-of equipment can be seen in
should be used in attempting to relate test series performed still photographs. For example, Fig. 8-28 shows the instru-
by different organizations using this technique, but this corn- mentation anti four cameras used as well as the test fixture
parison can provide a crude measure of condation within a and terrain of the tests documented in Ref. 3. Also note that
single test series or of tests perfonrmd dmi.ng a short period in Fig. 8-24 there was no concrete pad; the test fixture itself
of time by the same organization. was depended upon to catch leaked fuel, and a large, heavy

8-27
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,,
IWL-HDBK”684

Figure 8:28. Tkst Site Imtaktion {~ef. 3) “

pipe ‘was’ used to capture. fragments ~om” ~e .M28 HEAT
warhead. Fig. 8-29P a test subsequent to’Ref. 3, shows that a
test pad had been constructed to cap~e leaked fuel and that (B) Sh@ed Charge on Opposite Side of the Test Fixture
From the Fuel Cell
the fragment trap for. the’ wtihead had been reinforced;
Note The shaped charge was enclosed in the large frag-
Detriils that the author of ‘a test report did not deem worth
ment trap to the. left. The concrete pad had -a ‘large”sump
stating can be established from photos taken before, during,
pump on the far side to capture leaked fuel.
and after. tests. .,
Documentary motion pictyre (24 fds) or video (30 fr/s) Figure 8-29. Installation for Testing (Ref. 5)
recor&ngs are of great, value in establishing overall test
events and results. The presence or absence of sustained run down the wall and drain into the bilge. The author has ‘:
‘e
combustion can be noted. The locations at” which ignition also picked up 5.56-mm ball .cartridges off the floor of a test
occurred ctin be established’ and those sites checked to find fixture, which had been thrown out of an ammunition box
,> perfofited by the shaped-chtige jet, and found the cartridges
the probable causes. ,’
. . usable. The flash fire just did not have time to heat the fix-
8-2.4.3 Value of Photo~aphs ~ ~{‘, ~ ture, $e ctidges, or the fuel to a reaction..temperature.)
Not only tests but also accidents, newspaper ‘&ticles,.and The .d~age done to the vehicle was from the. bkts~ the jet
combat records cariprovide important information~when still perforation, and. we hydraulic ram incident to jet passage.
photographs “iweanalyzed. Fig. 8-30(A) is of an ~“lAl MBT The @iver was killed, probably by the jet, but the jet did not
that was hit by a large antitank guided missile (ATGM) in exit the, far side of the vehicle.
Southwest Asia (SWA) early in 1991 (Ref. 35).~The missile Fig, S-30(B) is of the left side of the tumet of a Bradley
“hit the tank on the right side, above, and slightly forward of fighting’ vehicle (BFV) hit by the same type of missile.that
he front right road wheel. The jet entered the front right fuel hit the,. MIA1. -~s photograph shows Mat the tube-
cell and ruptured it and dispe~ed”the ~el around the tiont of Iaunched, optically tracked, wire-guided (TOW) launcher,
the vehicle and the rear of the turret, (The tank was appar; which is mounted there, was removed, but since there are no
ently traveling with the turret facing rearward.) Noting the obvious ~pacts from fragments of either.the TOW warhead
blackened surfaces of the front of the hull-and ~e rear of the or rnjwile motor,. it can be assumed that either the. TOW
turret and the statement of the photographer, ~ Spencer, launcher was in the:tiring position (unlikely) or that the war-
,, that “the vehicle was dripping wi~ ‘black oil”j, ,the author head bltit of the incoming missile merely blew the TOW
believes that the front right fuel cell was ruptured and that launcher and its &ssiles away without causing a detonation
although a flash fire followed, the fire self-extinguished of the. warhead or motor of either TOW. MAJ Spencer stated
,.” before the ammunition in the turret bustle could ignite. (In that both the vehicle commander and the gunner were killed
,.
several tests, the” author has seen diesel fuel draining down (probably by the “jet). However, the jet did not perforate the
the wall of a test fixture after a shaped-charge jet perforated far w’kll of the vehicle, nor did it start a fire or cause ammu-
a‘ test fixture and sprayed the fuel” within the ‘fixture. The nition to explode. Neither vehicle was imeparably damaged,
resulting fireball either self-extinguished or” was extin- even by the hit.of such a large weapon. Figs. 8T30(A) fid (B)
guished. After the test, the blackened diesel fuel was found illustrate that a significant amount of information can be 9
to have. coated the inside of the fixture and in some places to obtained from evaluation of such photographs.

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. -.

(A) MIA1 MBTAfter Impact

(B) Bradley fighting Vehicle Turret After Impact

courtesy
of MM c Spenser, North Camiina -y National Guard

Fi/ w 8-30. Whicles Impacted by Large HEAT Warheads in SWA

$-2.5.1 Fire Extinguishant Selection

8-2.5 OTHER ASPECTS OF FIRE SURVIV-
ABILITY TESTING Selection of a backup fire extinguishant to safeguard test
assers must be based upon the following.
Ihere are other aspects of fire survivability testing that
1. ?hetype of fireto be fought
require planning and preparation.inherently these tests often
2. The effectiveness of the agent under the conditions
result in fires. l%e test specimens axe’ often expensive and
of the test
therefore should be designed and fahicated or prepared not
3. The hazards associated with the agent that are inten-
to be destroyed in a single test should a fire result. Also test
sified by the test conditions
facilities must have backup systems to extinguish 6res.
4. The effects of the agents on cleanup and on prepara-
~ Sometimes the threat used WM require special operations to
tion for the next test
assure safety usually the mobility fuel must be trapped and
5. ‘fhe availability of equipment needed in order to use
disposed of safely after the tests. l%e fire-extinguishing
the agen~
agents must not add to the safety problems, and the test fix-
Some gaseous extinguishing agents, such as carbon diox-
ture contents should not present hazards that are not repre-
ide or Halon 1301, cannot be depended upon to extinguish a

0
sentative of those of the actual vehicle. The selection of
fire and then inert the fire site unless the fire is in a space that
“i~$‘
.:1,
, appropriate extinguishants, training of fire-fighting crews,
can effectively exclude the surrounding atmosphere. If the
and preparation of test fixtures are necessary for protection
fire is deepseated and/or smoldering-as in multilayered
of the test facility.
8-29
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i :. MIL-@BK-684 ‘
fabrics, .zrtultipiece wooden objects, or cus~oning mats-or. 80-kni/h (50-mph) airflow ove~-~e test fixture had to be shut
if metallic objects have been heated or if there are other igni-: off before the ciwbon dioxide could be used, and the carbon
tion sopces present, these inerting agents must remhn in dioxide.had to be:used before the fire became deep-seated or
a
,...: :place longxmough for the heated objects to cool or the igni; had heated the, suqounding structure. This carbon dioxide
tion sources to be eliminated; otherwise reignition will system required “a considerable investment.. of funds and
occur. If the volume containing the fire cannot be effectively’ prepwation. The system had a 3630-kg (4-ton)** storage
cIosed to the atmosphere,, the inerting agent may be ineffec-”’ bottle: connected with buried high-pressure steel pipe to the
tive in any case. This closure to the atmospiiere “need not be CARDOXQ fog nozzles seen” on Fig. 8-31 directed toward
complete. The small holes made by a shaped~charge jet or a: the test .specimen.%ach.nozzle was controlled by a solenoid
ICE penetrator will probably not be l~ge enough to admit valve’ operated fro~ the coni.rol trailer. The carbon dioxide
sufficient air for sustained combustion. If hatclfes or doors: blew out the fire’ if used promptly, or the tire became sus-
are blown open or a significant hole is made in. the vehicle tained. The storage bottle wx behind the berm and hidden
wall, however, sufficient air will probably be available to from view by the portable airflow unit seen on Fig. 8-19.
sustain combsistion. Ventilators or air blowers tliat introduce This ctibon dioxide system was backed up with alight water
air into the compartment in which a fire has started should be. system,. which was used when the tires, particularly .p.ool
shut off until after ‘tie combustion is extinguished and there, fires Under the test specimen, were sustained. ~~:
is no probability of reignition.
W1hls particd”ar foreign projectile does not have a superquick foze.
A cooling agent, such as water, extinguishes a fire more
The persofiel at the test organization modified, the delay fuze so
effectively, particultily if the fire is deep-seated or there are
that it functioned in approximately 20 ps, which is almost super-
nonelectrical ignition sources. Of all ~e fire extinguishants quick. ~is modified fuze was used only in the tests described in
-available, the one that has the lowest cost, presents the low: Ref. 34. In the tests described in Ref. 32, a striker sheetwas used in
nest hazard or contamination, and is usually most effective ii: order to have the ‘delay fuze function where a superquick fuze
water. The latent heats of. vaporization, specific heats,. and would’have functioned. ...
boiling points of water and two of the liquid halons are given” **~s specifies tie mass of carbon dioxide that the vacuum-insu-
,,.
in Table 7-3. lated bottle can contain.
The US Navy has explored the use of water m$sts to extin-
guish oil fires. In such a form water could be used very effec-.
tively within a test specimen or fixture. The, water mist
would not only be an excellent coolant: it would also lower
the oxygen percentage as the water droplets vaporize. Equip-
ment within the vehicle would have to, be able {owithstand
the high humidity, but so does equipment used in the tropics.
After, extinguishing a fire with water. rtjisq the extinguishant
-would present no greater hazard than is encountered in a
sauna, and the- wiiter niist will have removed m~y noxious
materials. See subpar. 7-2.3.1.6 for discussion of the use of
water mist as ati extinguishant. - “.
The US Navy has found that water mist c~ be used to
extinguish Class A and ClassB fires (Refs. 36 aqd.37). Their
work was on a fixed tie ex’tin~tisher system inte,nded for use
in submarines. This system W* designed to flood a 6. IX 6. I
x 2.7 h (20 x 20x 9 ft) test compartnient with a water fist
areal flow rate of ~.037 Lhnin.m2 (0:05 gaU(min~ft2)). Newly
ignited Class A and Class B fires were e&guish&l; deep-
seated Class A fires were not. Freshwater w& reco’inmended
for Class C tires but not tested (Ref; 38).-The ,principal fire:
ex@guishing mechanism was cooling, but the srnothenn”g
mechanism was of great benefit. Work on this system was
stopped in 1986 for lack of funding, and portable systems
“were not explored.
~ In several test programs (Refs. ”32, 34 and 39), a fixed,’
high-flow carbon dioxide system, illustrated “in Figl 8-31,
was used successfully to blow out a fire at the exposed sur-
Figure 8-31. In&dlation Showing Carbon IXox-
face. of a mobility-fuel-filled target impacted wih a s@m-
ide, Piping and Fog Nozzles Positioned to Extin- e
lated superquick-fuzed* 23-mm HEIT projectile. In these
guish JP-5 Fn (Ref. 39)
tests the. aircraft engine (shown in Fig. 8-18) used to force an
..
, 8-30
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MIL-HDBK-684

~W%en a fuel cell is perforate4 the fuel above the perfora- program in which personnel mistakenly assumed that Halon
flows out in liquid form. T%is fuel pools within test ti- 1301 could extinguish any &e that would occur within the
compartments or below the test specimen or fixture target. When the halon system failed to extinguish the fire,
.“ ‘unless provisions have been made to drain it elsewhere. If the backup system was used. The backup extinguishant cho-
ignited, a fixd pool provides enough heat energy to destroy sen was dry chemical powder, which was required to be used
oral least dist6rt almost any test specimen or fixture. Once a in large quantities during the test (The fire finally became
fuel pool has started to burn, the most effective extinguishing retarded enough that the burning items could be physicaUy
system is one with light water. ‘Iherefore, a light water fire- removed and allowed to smolder elsewhere.) In this incideng
extinguishing system is necessmy for tests involving mobd- watm could .hrtve been collected more easily, but th~ater
ity fuels.. itself would have had to be collected in drums. This cdlec-
Ligln water is water containing 3 or 6% aqueous film- don of water would have posed a disposal problem if a great
forming foam (AFFF) concentrate. This additive forms a --- amount of water were used to extinguish the fire, unless the
foam or film that will float on the surface of the fuel and pro- water had evaporated. (h the test cited the fire was-within a
tide a barrier that separates the fuel fium the air. ‘Ih.is con- . panicleboatd dummy covered by a cloth uniform. A-piece of
centrate is introduced into the water stream via an eductor or - . DU was embedded within the particleboard. Application by
similar metering device located between the pump and the a person webng proper breathing apparatus of a small
nozzle. A fire hose should be equipped with an adjustable amount of water, either as a jet or a spray, at the correct loca-
-Y or fog nozzle, which can also form a jet. The light tion could have quickly extinguished the fire without spread-
water should be sprayed on the fire to form a foam barrier on ing radioactive contaminants.)
the surface of the fuel (Ref. 40). If the water were used in a
stream the jet would break up the foam or film bamier on the
8-2.5.2 Fire-Fighting Crews and SOPS
fitel surface and could spread the ftre by splattering burning When tests with the potential for fire are being conducts
fuel droplets. a fire-fighting crew shouid be designated and trained to fight
Because the”AFFF additive is b-=ically a detergen~ it can any fires that may occur. Untrained personnel .ofi.en take the
clean oil or tie] off the test specimen or fixture; however, it wrong action (Ref. 40) and may expose themselves to haz-
can also cause the test specimen or fixture to corrode or rus~ ards unnecessarily. Fire-fighting crews should be trained and
Therefore, after the iire has been extinguishe&the flow of clothed in appropriate gear before the test.
.ght water and AFFF concentrate should be stopped and the Appropriate standard operating procedures (SOPS) should
hose fiushed out with water only. This water can also be. be prepared and distributed before the test. These SOPS
used to cod the test specimen and fixture and to flush the should assure that any fire is attacked promptly in a manner
foam off the fixture and test site. that does not endanger the fire-fighting crew, and the crew
TIE residual mobility fuel must be collected and pre- should be trained in the SOPS. The @fighting crew shouId
vented fkom soaking into the ground. ‘Ihe concttte pad be familiar with the test site, or someone familiar with the
shown in Fig. S-29 under the test fixture is a method of col- test site should accompany them.
lecting the fuel. This pad has a raised rim of concrete and a The iire-fighting crew should be tied how to approach a
sump in the’rear to prevent escape of released fuel. iire safely. Fwe fighters should not approach a liquid fuel lire
If ek.ctrical discharges are presen~ dry chemical extin- from downwind or downhill-the burning liquid or noxious
guishants are recommended. Water should not be used unless fumes may travel toward the crew. l%ey should not enter a
the electric circuit is opened. cloud where carbon dioxide has been dispersed. The white
la tests involving depleted uranium (DU) penetrators, cloud is actually moisture condensed from the air, but it also
there is another problem. All detectable uranium ancl/or ura- contains a great deal of ctu%on dioxide, which has diluted the
nium oxide must be removed and packaged for indefinite oxygen the fire fighter needs to breathe. A gas mask is of no
storage. For DU penettator tests the entire tmget area is usu- use in a carbon dioxide cloud the oxygen just is not therein
ally enclosed, and the air Witin pum~ out through a filter sufficient quantity. The SOP should clearly state when fire-
to provide a negative pressure differential between the out- fighang pemonnel should enter an area containing a fire and
side air and the air within the test fixture. This procedure what areas should be avoided. These procedures, however,
assures no loss of radioactive particulate. Due to the ballis- should not unnecessarily limit the fire-fighting crew’s access
tic impq some of the DU becomes an aerosol. This- DU to the area. An example of unnecessary limitation of the fire-
aerosol must be filtered OULand the tl.lters prepared for stor- fighting crews was the requirement during a test that a sin-
age. For exampl~ if a dry chemical extinguishant were u- gle-shot Mann gun have its screw-on breech removed before
that dry chemical powder would have to be collected. Such the test site could be entered. (There is no way a single-shot
an operation involving filtering down to one-micron-size Mann gun can &e a second shot without a second round

,,
‘If/!/
o‘: particles is very expensive in time, labor, and filters (which
include long-term storage). The requirement of such a clean-
up operation caused a six-week delay in a test schedule in a
being loaded-) There are many procedures such as these that
untrained
in the
personnel either do not know or will not remember
excitement of fighting a fire.

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,. ., . ..
“ NNL4-IDBK-684
8-2.5.3” Preparation of Test SpeciniernandFixture some have been adapted .tonaval ships. The models assume a
for a Fire sustained fire exists in one room, and then monitor heat
Specialtest equipment within the test fixture and the spec- buildup and fltie spread. The generation and flow of toxic
o
imen should be installed so that such equipment will not be produc~ are similarly predicted. Such a model, however, is
lost as a result of afire. This is particuli-mly applicable to such of little use for a combat vehicle with two or three “rooms” at
items as remote television or video cheras, w~ch may be most mid those “rooms” are usuidly separated by fire bti-
me principal means of letting the test controller know the ers. In fact, as has been established in many instances in the
staigs of an internal fire. -, reperk described in subpar. 4-1.1, the driver of a combat
Care should be taken not to introduce combustibles unnec- vehicle has difficulty -realizing that there is a fire in. the
essdly into the’test fixture. For example, a du~y used to engine compartment of his vehicle, which may be only a few
represent a crewman within a combat vehicle should be no millimeters away on the other side of a fire wall.
more combustible than the crewman himself. The human There are computer models that predict the vulnerability
body is approximately 78% water, and this water must boil .of combat vehicles and the time required to repair battle
out before the body can susi.ain combustion: A duby made damage. These models use prepared Pm and P&. tables as
of papier-mach$, particleboard, or cloth aid plywood would described previou~y. Usable with these models is a model
present a fire hazard that a’ human body would not. Fires called kIRESIM (Ref. 42). FIRESIM provides the capability
within .tiese materials could become ~eep-seated md would to designate components to be flammable fluid locations or
present a reignition problem not representative. of a human heat sides, stowed ~unition, or components protected by
body: ‘Use. of styrofoam ‘would be worse because its fumes afire-extinguishing system. When these specific components
would” be toxic. For tests of combat vehic]es in which the-~ we hit, “tie”model provides logic to assess the type of kill that
crew is to berepresented sufficient y well to establish wound occws or, in the case of components protected by the fire-
probability, low-cost dummies should be. used. A recom- extinguishing system, whether the kill is prevented. Again
mended filling for these’dummies is gelled water. - : the user must input tables of probability of kill for each case.
Also. simulating, ammunition with plastic repiicas is dis~ As Dr. B. E. Cuminings (Ref. 43) pointed o~t in 1973, the
couraged because solid plastic replicas are costly and thin greatest void is in the area of probability of kill predictions.
plastic:replicas are subject to heat damage and ~istortion. It Dr. Finnerty has prepared a qbulation of probabilities of sus-
is reasonable to exclude the explosive filler in ammunition tained ‘fires for combat-damaged vehicles in Ref. 8-44.
from- tests? but onboard munitions would be. beiler repre- FIRESIM is further described in subpar. 8-3.3.1.
sented by hollow metallic surrogates rather than’solid plastic A model that accounted for the incidence of fire separately *
ones. Combustible cartridge cases would be better repre- ~om other terminal effects is the PARKed AirCraft (PARK
sented by “file-retardant-treated cardboard tubes” that contain AC) “model (Ref. 45). The treatment of incidence of fire ,
sand. These metallic or cardboard surrogates would provide given a 23-mm 13EIT projectile hit in or near a fuel cell was
witness devices that would “record” impacts by thieats capa- exp~ded (Ref. 46). PARK AC is further described in subpar.
ble of igniting or initiating the nornd onboard munitions: 8-3.3.2.
This simulation does. not apply to live-fire tests in. which tie A computer model follows a. series of logic operations in
objective is to establish-what will happen when a vehicle. which” decisions are based upon conditions, configurations,
contacting its normal combat load is hit. ~ ‘. ‘events, and/or circumstances. Sometimes empirical data are
used’ to provide the probability of occurrence of given
8-3 MODELING ~ ~ events. Often the decisions are based upon mathematical
Computer models. are used to make a preliminary ev@ua- models of natural phenomena.
tion of a design id ,can be- used to establish t$e relative Several mathematical modeling techniques are used. One
effectiveness of survivability enhancement devices. Such technique is to model phenomena that occur horn theoretical
com~uter models are very” valuable design tools. Cuirentl~ concepts. This usually leads to an involved theoretical model
available models, however, usually predict the probability of of “events that is partial] y hypothetical and involves inputs
kill (Pm) or darnage (Pti) given a ballistic hit in a particukir from’ h~dbooks which may or may not be truly representa-
location. These models use tables of kill and damage proba- tive. ‘A second technique is to base a model upon empirical
bility that have been generated by tests ador by the best test or. incident data. This usually requires a multitude of
engineering estimates of knowledgeable personnel. The PM. tests, the results of which are interpolated. ~ese tests, how-
tables do not differentiate between the terminal effects that ever, are of specific designs that are not always applicable to
cause the kill; the tables indicate ”either a kill or no kill given new designs. A third technique, similitude modeling, is par-
a hit in a certain location. Thus they do not predict partial tially theoretical and, partially empirical. In this method non-
effects of fire. dimensional Buckingham Pi terms are established that relate
There are computer models that predict the spread of fire theoretical phenomena. When a good correlation has been
and/or generation of toxic combustion products (Ref. 41). established, an empirical fit to all applicable test data is
made. This technique makes maximum use of all available o
These models were developed for apartment buildlngs, but

8-32

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MIL-HDBK-684
.-
empirical @a and znaxhizes the utility of&e empirical fit workshops. .The first WOLW., focused on the data avail-
,, ,by using as many parameters as are applicable. abte and testing techniques, whereas the second workshop
,J,!,+;
$,, An example of data regression to provide a predictive focused on assessment methodology. In addition, the Joint
o
-.:: =equationis.sltown on Fig. 8-32 (Ref. 47). Impact velocities Technical Coordinating Group for Aircmft Survivability
were from 59 to 3537 m/s (193 to 11,60S fds), and obliqui- (lTCG/AS) sponsored a workshop to establish the best
titis were from O deg to 80 deg. The total number of data usable component vulnerability, i.e., probability of damage
points was 847. All materials were transparent including given a hit (Pfi), for use in akraft vulnerability assess-
laminates, homogeneous mattials, bullet-resistant glass, and ments. One of the panels was assigned “crew stations”,
pcdycarbcmate. Projectiles included steel fragments as well which included all persomel aboard the aircmk ~--=
as bullets. Residual velocities were from 2993 to O trds (9820
to O ft/s). This similitude modeling approach is recom-
S-3.1.1 FM Live-Fire Crew Casualty Assessment ~
Workshop
mended for preparing mathematical models. See Ref. 48 for
details on similitu& modeling. The first live-fire crew casualty assessment workshop was
held at the Naval Submarine Base, Groton, CT, 18~19 Octo-
8-3.1 CREW-INCAPACITATION . ber 1988. This workshop concentrated on establishing-the
There is currently no computer model available that can availability of pertinent data and how such data could be
predict the casualties in combat vehicles. l%ere are models obtained. Approximately 150 military, civilian, Government
that can predict casualties caused by bulle~ fragmen~ or industry, and medical representatives attended this work-
fkhette impac~ but these are for troops in the open and are shop. The panels that covered the subjects most pertinent to
not really for blast and not at all for burns, overheating, or this handbook were the working groups on bums, toxic
noxious gas (smoke) inhalation. As part of an attempt to gases, and biast.loverpressure. (Ref. 49)
develop a usable model for predicting crew incapacitation, The burns working group reviewed the Knox-burn model,
the Director of Live-Fro Testing, Office of the Secretary of which was derived fiotn the tests described in subprq. S-
“ Defen% has sponsored two crew casualty assessment 22.3.4. They also reviewed potential preventative measures

100.0
& 1 i I I 1
‘n
Pofycarbonate (PC)
Stir /Wylii A
cast Acryk OA
Bullet-Resistant Glass (ERG) A~
BRG + PC AA /!
General Electric (GE) RC 750
AA’ @
GL + RC750 .~
GL + MPC 500 A
n Line.
ACRY + PC
PC+ ACRY + PC #

c1 o“ Note: ACRY=Actylic
-. RC350andMPC500= GEIWrnenciatures
GL = Glass
‘cl t t
0.1 I___ 1 ! I
0.001 Oal 0.1 1.0 10.0 100.0 1000.o

Buckingham ~, dimensionless

_ 8-32. Regression of Test Data to Provide a Prediction Equation of Residual Vklocity for Projectile
,:)~;~~~Penetmtion (Ref. 47)
o !,

8-33
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: IUWHDBK-684
,,
such as-use- oflow-vulnerability ammunition, passive tech- For the ground systems_working group, the personnel
xiiques to prevent gross dispersion 01 fuel within the crew from the Live-Free Test Organization at the US Army Ballis-
compartment, and improved protective clothing. The inca- tics Research Laboratory (BRL) described how they were
o
pacitzking.effect of bums was discussed, but no criteria could conducting live-fire tests on Army ground equipment. The
be agreed upon. The working group members” agreed that sea systems work.@g group covered Nayy damage control
da% we available-most of wliich are presented in this hand- measures, which” are more” toward assuring that sufficient
book—but the data have not been collected into a single crewmen are avtilable to fight fires to save the ship than pro-
database. The best avtilable instrumentation was discuss~. tecting individual crewmen. (There is good reason for this:
Thermocouples appear to “furnish Ke best available tempera- Loss’ of the shiptis tantamount to loss of the entire crew:) The
ture instrumentation. air systems working group pointed out that for most aircraft
The toxic gases working gioup members agreed that the crewmen could do little to affect casualty reduction. A
most cument work has been with the toxicity of individual crewman is fairly well fixed in place, much like other aircraft
g~es rather than the degree of” incapacitation caused by components, uqil the aircraft lands. (This is not correct for
breathing the gases. They agreed that ,tie degree of incapac- large aircraft such as the AC-130.) For aircraft crews the
,.
itation should be explored. In a study .perforrned by Knight, most Important items are the capability of the crewmen to
Sci_dichting, and Dougherty (Ref. 50),, the menw and motor perfoti their duties and the time required for a wounded
capabilities of six. volunteers were evaluated aker exposure cre~man to return to duty.
io noxious gases. After being exposed to ari atmosphere For the incapacitation working group, the greatest need
with a 12% oxygen. content for 30 rein,. their mental capa- found was for a series of definitions of “incapacitation”. The
bilities (ability to perform mathematical computations) working group members a~eed that each service and many
were noticeably impaired, but their motor capabilities (abil- specialties require different definitions. There was agree-
ity to pedal an exercise bike) were not. - ‘“ ~ ment that a “humm tolerance handbook” is needed.
The blastfoverpressure working group reported that the For the methodology working group, the .c.onsensus:iwas
greatest problem is that blast or overpressure within a mili- that each service should develop its own crew casualty
tary vehicle is never “clean”, it is always accompanied by assessment methodology.
fire and fiagmenti. Aside from this problem, good tech-
8-3.J.3 Crew Casual~” Assessment Reference Sys-
niques are available for predicting “clean” blast effects, but
tem
jtit what a crewman has to be incapable of doing before fie
The Office of the Deputy Director of Test and Evaluation/ m
is considered incapacitated has not been defined.
Live-Fire Testing had a personal computer database direc- ‘-
A definition of incapacitation is needed for all three areas,
tory prepared (Ref. 52) and distributed to Government and
i.e., bums, toxic gases, and blastiove~ressure, ‘singly and in
indushy experts in crew casualty assessments. This directory
combination.
describes available databases and instructs users where the
8-3.1;2 Second Live-Fire Crew Casualty Assess- data and/or models are located.
rnent Workshop
8-3.1.4 JTCG/AS Component Vulnerability Pti
The second live-fire crew casualty assessment workshop
was ,held at Brooks Air Force Base, San Antonio, TX, on 29 Workshop
October l-November 1990. Again there were approximately This workshop convened at Wright-Patterson Air Force
150 attendees, most of whom had agended the ‘first work- Base, OH, in February 1991. The crew stations panel con-
shop. The first order of business was to receive updates on sisted of five individuals, all from private organizations. The
the subjects of the first workshop. Then the workshop ‘consehsus of this group was that the existing fragment or
divided into three working groups: ground, sea, and air sys- bullet impact methodology would have to be used to predict
tems: For the final efforts the workshop divided into t,wo incapacitation, particularly for pilots. They believed. that
working groups: (1) incapacitation assessment tiethodolo~ other types of wounds could not be assessed with the current
and (2) integrated crew/equipment and” integrated crew/ state of assessment me~odology (Ref. 47). The criteria for
equipment weapon system vulnerability and lethality assess- incapacitation, therefore, are still based upon the capabilities
ment methodology. (Ref. 51) needed by an infantry rifleman to use his weapon and move
h, the update for burns, some work had been done on pre- on the battlefield.
dicting bums, but most of the work done had been on how to
prevent burns. The Knox prediction methodology was still 8-3.2 EQUIPMENT’ DAMAGE
the best available. In the update for toxic gases, the only In existing vulnerabili~ assessment models vehicular
work reported was by the Navy. ~ey still recommended the components are assessed for ballistic impact damage caused
use of their oxygen breathing apparatus when fighting fires. only by kinetic energy impacts. An aircraft or vehicle maybe
The update for blastloverpressure reported that work in the deemed lost due to blast or tire, but that is a yes or no deci-
field had continued. sion. In PARK AC provision was made to assess heat and e

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MIL-HDBK-684

. . burn damage to rubber tires and canopies from nearby pool . of loss. Loss due to explosim.is determined elsewhere and
m fires (Ref. 45) based upon aimraft b~ tests at the ‘N>val used in the vulnerab~ty programs that use FIIUXM as
inpuL In some vehicles fluid containers of a given type are
‘.A lire damage computer model for a combat vehicle interconnected; when one is punctured and the fluid spills, aU
engine compartment would be a very useful design tool. those connected to- it will also be drained. Included in the
Because such a model is not currently available, a model input &ta are amays indicating into which sink fluid horn
should be prepared with the following features. All vehicular each location drains. Fluid draining outside the vehicle
components would have 10 be assessed to establish failure or should be ueated as a separate sink.
malfunction mocks due to surrounding combustion and/or The vulnerability af--the.combustible fluids is given as
heating. The contribution of each component to the available ‘conditional probabdities of ignition given puncture or perfo-
combustibles would have to be noted. Where high-energy ration of the fluid container. Two types of fires are addressed:
combustibles such as mobility fuel, lubricating oil, or (1) an immediate fire caused by the puncture of the container
hydraulic fluid could be liberated, the circumstances by . and (2) ignition of fluids spiUed and collected in .a sink but
which such liberation occurs would have to be monitomd. not ignited by earlier impacts. Type 1 fires depend on the
me effects of sumivability enhancement devices; such as vehicle, the threag the fluidtype, and the fluid location. Tjpe
iire extinguishers or intumescent coatings, would have to be 2 fires depend upon ignition of a fluid pool by a threat and are
included. A probable scenario would be for a shaped-charge conditional upon the threat entering the compartment defin-
jet to peneuate a fuel line and thus Iiberate XL (Ygal) of JP- ing tie sink The probabfities of Type 2 fires can vary for
8, which wonld be assumed to ignittxmd bum. Given no spe- each sink and the fluid in each sink. Thus there are two prob-
dic extinguishment that fuel could be assumed to liberate abilities for fires in each sinlG one if the sink contains fiel
XX Joules (YYBtus) of heat energy. The probability of such and a second ifit conrains only Lubricating oihadoz hydrau-
ignition and combustion occurring would be based upon 6re- bC fluid.
extinguishing system and/or component performarm. This Each sink is assumed to have one of two types oflire-
heat energy could heat objects, ignite materials, or be lost to extinguishing systems. The Iirst type will discharge when
the external environment- The greatest value of this model there is a fire in its sink or in one of the locations draining
would be to establish the relative efficacy of candidate sur- into the sink. The second type will discharge whenever there
vivability enhancement devices. Given specific component is a perforation into the sink or a puncture of one of the fluid
damage criteria, a heat transfer model, such as that described locations draining into the sink whether or not a fire is
in subp. 8-3.4, could be modified to provide an equipment . started. For both types of extinguishers, two probabilities for
damage model. extinguishment are given. The first is the probability that a
single charge of the extittguishant will extinguish a Type 1
8-3S I?IRIZ IN1’I’MTION
(mist fireball) tire, and the second is the probability that a
~e mvo extant programs for predicting initiation or igni- single charge of the extinguishant will extinguish a Type 2
tion of explosionsor fires are FIRESIM (Ref. 42) and PARK (pool) fire. No distinction is made in either case for the type
AC, (Ref. ‘45). In addition, Dr. A. E. Fimerty (Ref. 44) has of fluid burning. It is assumed that the extinguisher will not
_ a tabtion of predicted probabilities of sustained extinguish an ammunition iire. Each extinguisher system can
b for combat-damaged vehicles based upon test data. -- discharge up to n shots; n is an input to the program.
8-3.3.1 FrRESm FIRESIM uses pregenerated tables of damage for prede-
termined shot lines. For a given shot line, if a combustible
FRESINl (Ref. 42) uses the Monte Cailo technique to
fluid container has been punctur~ a random number is
predict the probabllty of fire given a hit. Each flammable
obtained and compared to the probability of a T~ 1 fire for
fluid container must be tilgnated. These containers are fuel
that container. If the random number is less than the proba-
&w& lin~ and fil~, lubricant locations such as oil pans,
bility of fire, a fire is assumed to occur. Similarly, penetration
riXO~ fluid reservoir, etc.; hydraulic cylinders, res~om
of a threat into a sink requires the- random number check for
and accumulator, as well as sinks where spilIed fluids col-
aType2fire.
k2cL Stowed ammunition is identified. For fluid locations the
-IM requires damage prediction fkom the vulnerabil-
critical damage is perforation of the” componen~ which
ity model COVART or a similar vulnerability model as an
causes the co~tained-fluid to spill. Ignition o; these ffuids is
input. FIRESIM does not predict fire ignition based upon the
treated separately. For the sinks the critical damage is perfo-
reaction of vehicuIar components to the thre% it uses user
ration of the sink by the _ which creates the possibility
probability inpum and then figuratively ilips a coin x number
of ignition of any spilled flammable fluids that have col-
of times to decide whether a fire occurs or whether other
lected there. For the stowed ammunition the critical damage

,,,:
J)(
o
“(”j
is whatever causes that ammunition to detomte or ignite and
cause the vehicle to suffer a catasuophic kill. This model
does not&ermine what level of damage will cause this type
events occur.
FIRESIM has the capability to predict casualties given
kinetic energy (ICE) missile impacts. The user must input the
kill, wound, and injury criteri~ FIRESIM just monitors how

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IWL-HDBK-684
many vehicle occupants are hit by the penetrating threat and An abbreviated ‘version of-E4RK AC, called ENDGAM,
considers these occupants as addhional components. “ has the capability to handle moving targets and was used to
establish aerial bomb fragment hits on trucks in convoys or e
8-3.3.2 .~ARK AC
laagers or warhead fragment hits on an aerial missile. END-
PARK AC’(Refs. 45 and 46) iS a computer model written GAM has been used in two projects at Southwest Research
to be operated inde~ndently rather ‘tian as an adjunct to Insti$ute, so it should be available for use. ENDGAM has
another model,’ such as ‘FJRESIM. which is ~ adjunct to been, prepared for batch mode operation.
COVART. This model was prepared to establish which ti- P@K AC has not yet been used. A moderate effort would
craft pinked on m air base would ,surviv”e a conventional be needed befo~.it would .beavailable for use. It uses.,modi-
weapons attack and how soon damaged, but repairable, air-. .tied combinatorial geometry for its target description and.
craft would be available to fly a mission. Since fire and shot line generation. PARK AC was written for batch mode
explosion are the two principal modes of des~.ction, they oper?tion. Any, updating of this program should provide
received special attention. PARK AC relates damage directly, user~friendly term@al operation.
to either aircraft destruction or to the number of hours of
repair time needed before the aircraft can. perform another 8-3.3.3 Predictions of Probabilities of Sustained
mission. Also PARK AC uses a Monte Carlo approach. Sub- Fires for Combat-Damaged Vehicles “‘
routines (S/Rs) that treat fire and explosion are presented. In Ref: 44 Flnnerty provides the probabilities of a sus-
S/R BLOW calculates the reaction of stowed ordnance to tained fire within many different combat vehicles given hits
impact by a high-velocity fragment or a projectile. -The cri- with several types of threats. These probabilities are based
teria and databases for the chemical reac~ons of such rip upoq both combat and test data and me for the vehicles as
impact are given in Ref. 46. Similitude modeling of exten- built, The only survivability enhancement device considered
sive test data produced reaction criteria that considered war- is the automatic fire-extinguishing system if it is installed in
head casing thickness, -projectile size, shape, velocity, arid a vehicle, as built. This report would provide an excellent
other parameters. S/R BLOW addresses both high-explo- database to establish the baseline vulnerability of these vehi-
sive-filled warheads and solid propellant rocket motors. ‘” cles before other survivability enhancement” concepts are
,.
S/R PFYRE establishes the probability of ignition of a fire incorporated. Tlus work could provide the damage criteria
given a small high-explosive incendiary’ (H13) projectile for use in,either FIRESIM or PARK AC.
burst, the impact and subsequent initiation of am armor-pierc-
8-3.4 FIRE GROWTH AND EXTINGUISHING
ing incendiary projectile, or the impact of high-velocity frag- . a
ments on or neaca fuel-filled component. The analog for this Considering the limited size of combat vehicles and that
subroutine is described in Ref. 46 and is based upon data there is usually a fire wall or barrier between the engine com-
from more than .686 tests for small “HEI projectile bursts. partinent and the occupied compartment, fire growth is pri-
This subroutine takes into account the fuel tank ullage as marily concerned with the burning rate of the most
well as adjacent dry bays. Fuel igriitibility is treated as a combustible “material ignited. In the engine compartment the
function of bulk temperature, air velocity, and impact loca- most probable,, combustible is a hydrocarbon fluid, i.e.,
tion. Most of the survivability enhancement techniques used mobility fuel, lubricating oil, or hydraulic fluid. The hotter
the fluid, the more ~pid the combustion; therefore, as a fire
for aircrtit fuel systems are considered, but fire-extinguish- . .... ,,
.- ing systems are not. progresses; the burning rate increases with increased fluid
S/R TYPETR establishes whether or not a ,projectile or temperature. These materials are highly flammable in the
fragment trajectory intercepts an explosive-containing or mist state as well as in the vapor state and can explode. The
fyel-containing component or a component adjacent to a fuel most probable passages through which a fire in one compart-
tank. If a fuel-containing component is intercepted, the sub- ment of a, combat ,vebicle could enter another are via a bilge
routine establishes whether the interception is above or open to both compartments and openings made by the threat
below the fuel surface.. between the two compartments.
S/R LEAKS establishes which components are more The most important result from a fire growth computer
flammable because of fuel leaks caused by earlier hits. model is the ability to predict the rate of temperature rise of
“In addition, S/R PROJPN, which follows projectile pene= the compartment walls and of objects within the compart-
tration through aircraft components and other objects, ment. Temperattie rise is a function of the heat added less
checks for incendiary. projectile activation “as materials are the heat lost and of the specific heat of the materials heated.
perforated. If the fireball diameter of a high-explosive (HE) The heat added is controlled by the quantity and energy con-
warhead is greater than a given aircraft dimension, either S/ tent of the material combusting, the quantity of oxygen avail-
R PROJPN or DIRIWT can signal the destruction of that able, and the rate of combustion, which is in turn a function
, aircr~t. S/R DIREHT and FRDAMG can call S/R BLOW of combustible temperature. The practical use for such a
or P~RE if either a projectile or fragment is able to ini- computation would be to establish design details for a fire-
tiate or ignite component contents. sensing and/or fire-extinguishing system, or to establish the *

8-36
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MIL-HDBK-684

o:l;!/
time to malfunction of components or the time .of loss of ntent methods. -.> .-:.-
comparunent walls. This model has been made more user-friendly and has
!,,,1) There are Iwt transfer models available that can be used been checked by compating its results with results from a
---: .for~ckrxmtpwations. In these models the compartment and live-fire test on an MIA1 MBT. ‘fhe fluid flow computations
its contents are divided into nodes-either heat sources or have been checked by comparison with test results obtained
heat sinks-that are connected by paths for conductive, con- by the Jet Propulsion Laboratory, Burbti CA. (Ref. 5S)
vective, or radiative transfer of heat. Each heat sink has an
individual mass and spectic heat. Each heat source has a
8-3.4.2 Fluid FIow Computations
specific rate of heat generation which can be fixed or vari- Electric analogs are simple to use and are generally Wder-
able. Each heat transfer path is based upon a single means of stood. The calculations, however, could be made using fluid
heat transfer, and each path should consider all factors affect- flow rather than electric fiow. Such computations should not
ing heat transfer, e.g., the effective film coefficient resulting be too complicated and would easily lend themselves to treat
from the clamp connection where two pieces of metal are other extinguishants and other configurations of plumbing
bolted together. and compartments. An analysis using fluid flow parameters
l%e fire-extinguishing system would be incorporated ii rather than an electrical analog was performed without bene-
the heat transfer program by handling the temperature sen- fit of a personal computer in 1966 to establish the design for
sor(s) as additional nodes with logic provided to activate an ignition system for a supersonic ramjet engine. (Ref. 56)
negative heat generators or oxygen depleters simulating the In that system a pyrophoric liquid was forced from a toroidal
released extinguishants when appropriate temperatures are resemoir through a burnt diaphragm into a disrnbution sys-
reached Thns utility heat transfer computer programs could tem with multiple impinging jet nozzles that fed the combus-
be used or modified to model iire growth and extinguishment tion chntnber of the engine.
within a compartment of a combat vehicle. To improve the Another such evaluation was made in 1965 (Ref. 57) to
- predictions of such a model, better. analogs of burning rates estabiish why attitude control engines for the AwIIo sp-~-
of materials as affected by temperature will probably be craft were meeting performance requirements on. ~;e test
needed. stand but not on another. The flows of oxidizer and fuel horn
reservoirs into the combustion chambers were calculated for
8-3.4.1 Model for predicting the Performance of lo-ins pulses and were shown to differ in magnitude and tim-
,,,~
~.,?l: Halon Fii-Exthlgttishing systems ing sufficiently to nccount for the difference in performance.
;’~,llj
o Dtzewiecki et al (Ref. 54) have prepared a model for pre- The only causes for the differences in flow were the differ-
dicting the flow of Halon 1301 through plumbing to extin- ences in the plumbing,
guish a fire within a compartment. This model has been These two examples show that calculating the flows of
prepared for use on a personal computer and has been made different fluids in different piumbing are weU within the state
specifically for the Ml and MIA1 MBTs and their HaIon of the am The use of personal computcm should reduce the
1301 fire-exdn guishing system. l’lte model is divided into time required for these evaluations.
three plmses (1) computation Of the time required to fill the More recently, MPR Associates, Incz has prepared
distribution lines once the balon bottle valve has opened, (2) FLONiYP, a two-phase flow and pressure loss model to
computation of the halon flow through each individual noz- calculate the flow of HaIon 1301 through the tire-extinguish-
zie once the lines are filled and pressurized with halon, and ing system plumbing of a Navy ship (Ref. 58). MPR also
(3) computation of the halon concentration within the com- prepared TFHAL (Ref. 59) for the Naval Sea Systems Com-
partment in specified conmol volumes given the outflow mand, Fire Protection Division. a model for predicting the
rbrough the nozzles. The distribution line fill time is com- capability of the fire-extinguishing system of a Navy ship to
puted as an isentropic expansion process of the pressurizing functiom This model has additional features that make it
nitrogen with the halon liquid flow being throttled by valve more generally applicable. Tltese two models could be.com-
and line resistances. The halon flow out of each nozzle is bined and adapted for use in combat vehicles.
modeled as a distribution network of an equivalent elecrnc
resistive-inductive circuit driven by a discharging capacitor. 8-3.43 Fire Extinguisbmertt Predictions
Ha.lon concentration was treated as a bookkeeping problem Ewing et al (Ref. 60) performed a series of studies on the
of keeping track of the halon flowing into a space imid the effectiveness of extinguishants. Concentrating on the use of
transfer of halon-air mixtures between adjacent spaces. Tlte dry chemicals, they studied the parameters affecting extin-
fire was assumed extinguished when a vohunernc halon con- guishment, but they also studied liquids and gases. They
centration of 6$%was obtained. Throughout electric analogs took the extinguishment of heptane in a flat pan, conducted
were made of the fluid flow. The heating of items within the experiments, and by using a main frame computer, calcu-
compartment was mentioned but not included in the model. lated the results with STANJAN~, a chemical reaction
This model shows potential, but much more work should be model. They have established the optimum particle size for
done to generalize it for iire-extinguishing systems, fire several dry extinguishams, which are shown on Fig. 8-33,
extinguishan~ vehicle compartments, and fire extinguish- and verified these sizes in tests.

8“.37
 Downloaded from http://www.everyspec.com

NIIL4-K)BK-6$4

:GFe(CN)5.
3H~0
\
—-.\ \
\
I
1
\
t \
1
i \
4
1

“+”K
,
K4Fe(CN)g 3 H20
.

\
\
\.

i
‘,

,.
Na2B4 07-10 H20

10 20 30 40 50 60 70 80 90 100 “I1O
Average Particle Size, mm
I I i I I 1 I r I t
o lom304050w 70 WJ90 100 Reprinted with permission. Copyright e Society of Fire Protection
Par!kJe Oiameler, ~ m Engineers. e
Reprinted with permission. Copyright o Society of Fire Protection F@urk S-34. Flame Extinguishing Effectiven~
Engineers.
Versus Particle Size for Large Particle Sizes of
l@ure8-33.
Extinguishing Effectiven~ Versus Ely@rated Extinguishants (Ref. 60)
Particle Diameter for the Extinction of the iV-
~eptame Pan Fire (Ref. 60)
.’..
Ewing et al (Refs. 60,61,62, 63,.and 64) are propounding’ (mole percentage in air). If the experimental results were
a hypothesis that thermal absorption is the principal mecha- obtained from literature, the average differential between
nism in extinguishing flame. By their hypothesis flame is analytical and experimental results was *16%. See Table 8-2
extinguished when sufficient heat is removed’ to allow the for comparisons. If they conducted the experiments, the
adiabatic flame temperature to fall below a h-+ tempera- average differential was *7%. These predicted results, both
ture,. TLfi Their model is basically a heat balance in which the experimental and imalyticali are based upon extinction of
heat-absorbing capabilities of the. extinguishant including flame, not upon cooling the fire site be~ow fuel kindlingtem-
changes of state, changes in temperature, and decomposition’ perature. Their analytical technique has been shown to apply
or disassociation tie comp”ared to the heat produced by the to both Class A and Class B fires.
chemical reactions of the fuel. The model locates tie concety Ewing. et al concluded that the primary fire extinguish-
tration ‘of extinguishant C needed to lower the temperature of ment method involved is through cooling the flames. This
the flme below the temperature needed to sustain combus- conclusion is highly probable since the standard practice of
tion, i.e., Tfi. The effectiveness of some hydrated extinguis- fire-fighting personnel and of vehicle designers is to apply
hants is shown on Fig. 8-34. Ewing et al have shown tliat this more’ extinguishant than is needed by factors of three, four,
methodology can predict the performance of halons, dry or five. Fristrom said 10 to 100 times (Ref. 65). Therefore,
chemical extinguishants, and Iiquid extin”~shants for both the cooling effect very probably is the most important for the
diffusion flames (the flames over a pool fire) and premixed physically acting agents.
flames (the flames of a gaseous fuelhir mixture in a chamber,
e.g.: the ullage of a fuel cell). They have compared analytical
and experimental results using the extinction concentrations

8-38
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MIL-HI)BK-684

TAlUJ3 8-2 COMPARISON OF PRED1(XEJJ EXTINGUISHING CON-

cENmATIoNs
WITH
EXPERIMENT ALVALUIEl FROMLITERA’TCJRE
(FINELY DIVIDED SOLIDS AND LIQUIDS) (Ref. 61)

EXTINCTJON
CONCENTRMIONS”,
(rnol % in Air)

EXI’ANGUISHING
PREDICTED THERMAL
cHEMlcAL EXPERIMENTAL
MECIiANISMS
SUBSTANCE
N~C03 0.65 0.53

NaHC03 0.88 1.30

mco~ 0.59 0.57

Ala, 1.60 1.20

FiaCi 1.40 1.10

&o (mist) 5.20 5.00

Br2 2.20 2.30 “

Iz 2.30 2.30
‘iAverage differential~16%
Reprinted wifb permission. Copyright 9 Defense Fire Protection AssociatiorL

REFERENCES ne[ Ckm.ers Due w Ballistic Penetration, Report No.

AFLR 194, US Army Fuels and Lubricants Laboratory,
1. DoD Diieuive 5000.1, Defense Acquisirwn, 23 Febru-
San Antonio, ~ March 1985.
ary 1991.
7. P. H. Z%bel, Passive Techniques to Counter Ballistically
2 DoD Instruction 500CQ Defense Acquisitwn Manage-
initiated Fuel T& Fires, Report No. 6-4838-001,
ment Policies and Ptvcedures, 23 February 1.991. -.
Southwest ResearchInstitute, San Antonio, TX for Sur-
3. P. l% Zabd, Test Prvgram to Demonstrate Enhanced vivability Systems, Armored Systems Modernization,
Survivability of Ahmtinum Armored Vehicle Fuel System Wamen, MI, February 1992.
to Shaped-Charge Attack, Report No. 06-8899-001,
8. R J. DeWht and P. H. Zabel, Tests of Hydraulic Ram
Southwest Research Institute, San Antonio, TX, for US
Bu#enng Materials, Report No. 4560-74-43, Dynamic
Army Ballistic Research Laborato~, Aberdeen Proving
Science, Phoeti ~ for Navy Weapons Center, China
Grourt~ MD, hdy 1986.
Lake, m May 1974.
4. D-M. Potter and J. G. Barger, Final Report on Milita~
9. P. H. Zabel, “Test Evaluation of Shock-Buffering Ccm-
Potential T& of RPG-7 Weapon System, Report No.
cept for Hydrodynamic Ram Induced by Yawing Pr-
DPS-2866, US Army Test and Evaluation Command,
ojectile Impacting a Simulated Integral Fuel Tank”, J7ze
Abmleen Proving Ground MD, September 1968.
Shock and Viration Bulletin 40, Part 1, The Shock and
5. P-H. Zabel, !3taped-Cha~e Test Pe@onnance of Fue! Vhation Information Center, US Naval Research Lab-
T&for the Advanced Survivability T2.rtBed Vehicles,
oratory,Washington, DC, September 1979, pp. 141-70.
Report No. 06-8899-003, Southwest Research Institute,
San Antonio, ‘IX, for US hlly Bdtistic Research Lab
10. P. H. .Zabel, Southwest Research Institute, San Antonio,
7X, Recollection of work performed at Rocketdyne in
oratmy, Aberdeen Proving Grount MD, February
1957 for large, liquid propellant rocket engines.
1987.
11. P. H. Zabel and G. J. Friesenhahn, Gun~ Tests 200-
M.D. Kanakia and B. R. Wrigh~ lnvesrigation of Diesel
Gailon, Filament-Wound, &-tenal Fuel T&, Pan
Fuel Fire Vulnerability Parameters k Armored Pecon-
Number 3016A OOOi, Serial Numbers 004 and 005,
8-39
 Downloaded from http://www.everyspec.com

,, MIL-HDBK-684 :
Report No. 02-7047-1 (Program ‘was a US Navy sub- ~te Sands Test Faci~.xlxis Cruces, NM, 12 August
contract for” Fiber Science Division of. EDO, Inc., i985. ,
Ogden, UT.), Southwest Research Institute, San Anto- 26. Letter Report, from P., H. Zabel, Southwest Resemch e
lliO, ~, July 1982. Institute, San Antonio, TX, to J.-Johnson, McDonnell
12. 1? EL Zabel and R. E. White, Hydraulic” Ram Study, .. Douglas, Tulsa; OK, Subject: Fragment Impact Test on
Report No. 06-9360, Southwest Research Institute, San External Fuel Tank FPU-61A, Part No. 74A550000-
Antonio, TX, December 1985. 1011, Serial No. HTT-009, 28 January 1981.
13. Product “Description, Lp-33 Blast ,Pressure Trans- 27. P. H. Zabel, .P. F...l?iscapo, and L. E. Hendrickson,
ducer, Celesco Industries, .Inc., Canoga: Park,’ CA, “Functioning/Mal functioning of 23-mm Projectile in
Undated. Aiqcraft Integral Fuel Tanks, Resultant Target Damage,
14. PCB 137A (Susquehanna ST-7] Charge ~R40de Blast and Relative Vulnerability of Neat and Modified JP-5
Probe 10pG-psi, PCB Piez,otronics, Inc., Depew, NY, Fuels”, Proceedings of the Symposium on Vulnerabili@
Undated. and Survivability of Su~ace and Aen-al Targets,
..’
15. PCB 138A, Underwater Tourmaline. Blast Pressure .“ Monterey, CA, American Defense .Preparedness Associ-
-.
ation, Washington, DC, 1975.
Transducer, PCB Piezotronics, Inc., Depew, NY,
Undated. 28. Model 200 Simultaneous Streak and Framing Camera,
,.,
Form No. 8/14/64, Bec~an-Whitley, San Carlos, CA,
16. Telephone conversation between P. E?.Zabel, Southwest
1964.
Research Institute, San, Antonio, TX, and Ben Granath,
consultant to PCB Piezotronics, Inc., ad inventor of the 29. Operat~ng instructions With Illustrated Parts List for
137Aand 138Agages. ~ the Hycam m II 400-ji, 16-mm, High-Speed Rotating
Prism Camera, Redlake Camera Corporation, Morgan
17. P. H. Zabel, “23-mm Hydrodynamic Ram Damage to an
Hill, CA, January 1984.
Integral Wing Fuel Tank”, Hydrodyn&mic Ram Seminar,
Report No. AFFbL-TR-77-32 (and JTCG/AS-77- 30. LOCAM 16-mm Cameras, Models 50 and 51, Redktke
DO02), US Air Force Flight Dynamics” Laboratory, Camera Corporation, Morgm’ roll, CA, Undated. .
Wright Patterson Air Force Base, OH, May 1977. 31. M.. Lee, Preliminary Invesrigafion of the Soviet 23-mm
18. P. H. Zabel, M. J. Lewis, Jr., and B. Bonkosky,
Surviv- HEIT Projectile, NWC TN 5114-065-74, Naval Weap-
abili~ Enhancement of Advanced Survivabili~. Test Bed ons Center, China Lake, CA, 1974. e
Vehicle Given a Shaped-Charge Hit Through the Engine. 32. P. ‘H. Zabel, Reduction of Army Helicopter Fuel Tank
Compamnent Fuel Tank, Repofl” No. ASw-87-2, US Vulnerabili~ to 23-mm, HEIT Projectile, USAAM-
Army ‘Tank-Automotive Command, Warren, - MI, 31 ~L-TR-75i32, US ky Air Mobility Research and
July 1987. Development Laboratory, Fort Eustis, VA, August 1975.
19. E. A. Avallone and T. Baumeister
~, Eds., “~arkk Stan- 33. C.. P. Braadflad~ Ballistic Test of Ml13~l/A2 Internal
oizrd Handbook for Mech.&ical Engineers; ,9th .Ed.; Fuel Tank (PIN 11678175) W?th Explosafe~, Technical
McGraw-Hill Book Company, Inc., New York, WY Report No. 3802, Ordnance Division Engineering, FMC
1987. Corporation, San Jose, CA, April 1982.
20. H. J. Trietley, Radio Electronics, Part 1, 4~-50 (January 34. P. H. Zabel, ”Gunfire Tests of Bell Helicopter Fuel Cell
1985) and Part 2,73-6 (Februa.iy 1985). .. Installation Vulnerability, Report No. 1560-7591, Ultra-
,’ 21. D. Rail,” Chapter 2, “Heat Flux”, LSA‘Transducer Coriz~ systems, Dynamic Science Division, Phoenix, AZ, May
pendiuni, 2nd Ed., Part 3, Im.tmment ,Society of Amer- 1975. .
ica, Research Triangle Park, NC, 1972. ,‘ 35. R. Rosen, “When Shield Became Storm, Three Durham
22. ASTM E 800-88, Stanaizrd Guide for Measurement of Guardsmen Recall Life One Year Ago, at the Start of the
Gases Present or Generated During Fires, American Mother of All Battles”, Z7zeHerald-Sun, Durham, NC,
Society for Testing and Materials, Philadelphia, PA, il?hlllw 1992.
;.
1988. 36. R. Buteux and M. Grzeszkiewicz, Water Mist Test for
23. M. A. Cook, The Scie~ce of High Explosives; Reinhold $SN-21 Auxilia~ Machinery Room Mock-Up in the
Publishing Corporation, New York, NY, 1958. NRL Fire Test Chamber (Phase 11Report), DTNSRDC-
SME-CR-1O-86, David W. Taylor Naval Ship Research
24. M. A. Cook, “Fugacity Determination of the Products
and DevelopmentCenter, Bethesda, MD, June 1986.
of Detonation”, The Journal of Chemical Physics, 16,
No. 11,,1081-6 (November 1948). ~ 37. R. Buteux and M. Grzeszkiewicz, Water Mist Test for
SSN-21 Torpedo Room Mock-Up in the DTNSRDC 20
25. B. Porter, N. E. Schmidt, and C. V. Bishop,.Halon
130~
X 20’ Fire Test’Chamber (Phase ZReport), DTNSR,DC-
Fire Extinguishment Toxicity Program, ASA Test 9
SME-CR-1 1-86, David W. Taylor Naval Ship Research
Report No. TR-41 1-002, L. B. Johnson Space Center,
and Development Center, Bethesda, MD, June 1986.
8-40
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,,,[1
o,,;!,1!
:l;~
38. J. IL Lugar, SSN-21 Water M& System Summary
Report, SME 87-65, David W. Taylor Naval Ship
Research and Development Center, Bethestkq MD,
Proceedings of the L&e-xire Test Casucdty Assessment
Workrhop, Naval Submarine Base, Groton, CX, 18-19
October 1988, Office of the Director, Live-Fiie Testing,
August 1987. Department of Defense, Washington, DC.
39. P. H. Zabel, Gunjire Tars of JP-5/AM-l Mod@ed Fuel 51. Proceedings from the Second Live-Fire Crew &sualry
Systew Unpublished Fiial Report by Ultmsystems, Assessment Workrhop, Brooks Air Force Base, San
Dymtmic Science Division, Phoenix, AULfor Naval Air Antonio, TX, 29 October-1 November 1990, Office of
Propulsion Test Center, Trenton, NJ, May 1976. the Director, Live-Fn Testing, Department of Defense,
40. Learn or Bum or Trial by Fire-A tinier Fighls for Washington, DC.
Life, VMeotape prepared by Naval Photographic Cater 52. M. Powell, Crew casualty Assessment Reference Sys-
that discusses the fire on the USS Forrestal, 1967. tem (CC4RS) User’s Manual, l%e Analytic Sr5ence
41. C. E. Anderson, Jr., D. K O’Kelley, and A. F. Grand, Corporation, Fort Walton BeackL FL, April 1992.
“’Spread of Fn Effects Between Rooms: A Computa- 53. W. T. BurL Evaluation of A-4 Aircr@ Fire Damage as a
tional Model”, Journal of Fire Sciences 4, 365-96 Result of Simubzted Aimraji Cam”er Deck Fire, NWC
(November/December 1986). TM 2418, Naval Weapons Center, China Lake, CA,
42. A. I). Groves, FIREMf, A Multihi~ Vehcle Sum”vabiL February 1974.
ity Model, ASI Report No. 87-10, Aberdeen Group, ASI 54. T. M. Drzewiecki, W. D. Terry, 3. R. Stouq and T. M.
Systems Intemational,Aberdeen, MD, December 1987. Kieman, A Multiple Control Volume Model for Predict-
43. C. Candlana G. Kuehl, and B. E. Cummings, A Survey . ing the Perfomumce of Halon Fim Suppresswn Sys-
“- of Models Used lWzin the Vuherabiliq Laboratoy tems, Technical Report No. DR-031, Defense Research
Circa 1973, BRL-MR-2434, US Army Ballistic Technologies, Inc., Rockville, MD, December 1989.
Research Laboratory, Aberdeen Roving Ground, MD, 55. M. F. Salter and J. Nlemczk A Multiple Control Vol-
January 1975. ume Model for the Prediction. of Fire-Out Tiis in
44. &E. Finnerty, Predicfz”ons of Ftvbabilities of Sustahed Combat Vehick Engine Compamnents, Techni@ ~ote
Fires for Combat-Damaged Vehicles, BRL-TR-2875, No. TN-92-7, Defense Research Technologies, Inc.,
?,,,, US Army Ballistic Research Laboratory, Aberdeen Roclmille, MD, November 1992.
,,},,,,
!l!
‘1? Proving Ground, MD, November 1987. 56. P. H. 224x1, Dynamics of Pyrophoric Fuel Sysrem,
o
45. P. H. Zabel, L. M. Vargas, P. S. Westine, W. E. Baker, J. Interoffice Memo 501 1/15740/1019, The Marquardt
C. Hokanson, J. B. Lenox, P. FL Moseley, and E. P. Corporation, Van Nuys, % 12 May 1966.
B-, Parked Aircraft Vulnembili@ASurvivability 57. P, H. Zabel, Evaluation of D@erences Betweeen Cell 6
Estimation Techniques, ASD-TR-78-32, Aeronautical and Pad D as They Aflect the Dynamic Response of
Systems Division, Wright-Patterson Air Force Base, &tgines Tested on the Two Stands, Interoffice Memo
OH, September 1978. 3298/15740/935, The Marquardt Corporation, Van
46. P. H. Z&d, V. B. PaK, M. G. Whimey, and L. M. Var- Nuys, CA, 10 November 1965.
g=, Pa&ed Aircrtrjl VulnerabilityXSunn”wtbility Assess- 58. FLON.5TW, Halon 1301, Two-Phose Flow and Pres-
ment Procedure. ASD-TR-89-5051, Aeronautical sure LOSSAnalysis for Halon 1301 Piping Distribution
Systems Division, Wright-Patterson Air Force Base, Networks, MPR Associates, Inc., Washington, DC,
OH, November 1980. 1990.
47. P. H. Z&A, L. H. Woods, M. Meyers, C. F. Green, and 59. TF~ A Compuler Thermcd Hydraulic Analysis Sys-
S. M. Arndb Report of the Crew Stations Panel, JTCG/ tem for the Transient Flow of Halon 1301, MPR Associ-
AS Component Vldnerabiliiy Pm Workshop,. Wright- - >ates, Inc., Washington, DC, September 1989. .
Patterson Air Force Base, OH, February 1991. 60. C. T. Ewing, F. R. Faith, J. B. Remans, J. T. Hughes,
48. W. IZ Baker, P. S. Westine and F. E. Dodge, Similarity and H. W. CarharL ‘Thune Extinguishant Propaties of
Method in Engineering Dynamics, Hayden Book Co., Dry Chemicals: Extinction Weights for Small Diffusion
Inc., Rochelle Park+ N.J, 1973. Pan Fns and Additional Evi&nce for Flame Extin-
49. Proceedings of the Live-Fire Test Casualty Assessment guishment by Thermal Mechanisms”, Journal of Fire
Workshop, Naval Submarine Base, Groton, CT, 18-19 Protection Engineering 4, No. 2,35-52 (1992).
October 1988, Ofice of the Director, Live-Fn Testing, 61. C. T. Ewing, J. T. Hughes, and H. W. _ ‘The
w~t of Defense, Washington, DC. Extinguishment of Class A and Class B FMes by DIY
chemicals and a Themxd Mezhanisrn for l%mes Extin-

o
50. D. F. tigh~ C. Schlichtirtg, and J. P. Dougherty, Jr.,
,:,:(!$
, ‘~ Reversibl% Nontoxic Effects of Fire Products”, guishment”, Proceedings and Repon, VOL I of II, Fire
Safety/Survivability Symposium-’9O, The Defense
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Fire ProtectionAssociation, Alexandria, VA, November medical Eva$mtion o~.llummd Effects”, Handbook for
1990. Human Vultiergbility Criteria, Special Publication EB-
C. T.. Ewing, F. R. Faith, J. T. Hughes, and H. W. Car- SP-7601 1-7, Edgewood &senal, MD, May 1976. a
hart, “Evidence for Flame Extinguishment by Thermal D. T. Kihninster, A Model to Predict Human Skin Bums,
Mechanisms”, Fire Technology 25, No. 8; 195-212 BRL MR 2426, US Army Ballistic Research Labora-
(August 1989). tory, Aberdeen Proving Ground, MD, December 1974.
C. T. Ewing, F. R. Faith, J. T. Hughes, and ~. W. Car- Pohler,,,McVoy, Carbart, Leonard, and Pride, “Fire Safety of
hart, “Flame Extinguishment Properties of Dry Chemi- Naval Ships-An Open Challenge”, Naval Engineers
cals: Extinction Concentration for Small Diffusion I% .70ymal, 21-30 (April 1978).
Fires”, Fire Technology 25, No. 5, 134-:49 (May 1989).: B. R. Wright and W. D. Weatherford, Jr., Investigation of
C. T. Ewing, J. T. Hughes, and H. W.. carh~, “The Fire Vulnerability Reduction Effectiveness of Fire-
Extinction of Hydrocarbon Flames Based on the Heat Resistant Diesel Fuel in Armored Vehicular ‘Fuel Tanks,
Absorption Processes Which Occur in Them”, Fire and Final Report No. AFLRL 130, US Army Fuels and
Materials 8 (1984). Lubricants Research Laboratory, San Antonio, TX, Sep-
R. M. Fristrom, “Combustion suppression”, Fire tember 1980.
Research Abstracts aha’ Reviewi!l (3)+ 125-60 (1967). P. H. Zabel, Fraginentation Data, 23-mm High-Explosive
Incendiary Tracer Projectile, NWC TM 2649, Naval
BIBLIOGRAPHY , Weapons Center, China Lake, CA, December 1975.
P. H. ~bel “and W. Kuhn, Computer Model for Fragmenta-
W. F. Ashe, L. B. Roberts, and W. E. Mann, 71@e-Ternpera-
tion Threat From a High-Explosive Shell, Report No.
ture Relationships W%ich Produce Hot. Air Bums of
TFD-73-634; B-1 Divisioni Rockwell International, Los
Human Skin, Project 14, 710 SPMEA,. Arrpored ,Med~
Angeles, CA, ,1973.
cal Research Laboratory, Fort Knox, KY, 20 July 1944.
P. H. Zabel and V. B. Parr, “,Prediction of Initiation of Low-
A. E. Fhmerty,. The Physical and Chemical” Mechanism
&d High-Explosive I%llers .Due to Fragment or. Erojec-
Behind Fire-Safe Fuels, BRL Report No. ,1947, US
tde Impact”, 1980 JANNAF Propulsion Systems Haz-
Army Ballistic Research Laboratory, Aber~een moving
., , ards Subcommittee Meeting, Volume 1, CPIA
Ground, MD, November 1976.
,, Publication 330, Chemical Propulsion Information
a
R. R. Ingram, Jr., and R. F. McHugh, Jr., Chapter 7, “Bio-. Agency, Johns Hopkins University, Columbia MD,
December 1980.

:’

,.

, ,.

I
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-.
GLOSSARY

6V-53. A diesel engine used in Ml 13 family of vehicles. - with 1.29-gram (20-grain) flechettes. The flechettes
8V-71 D-it Diesel. An engine used in M105VM11O SP were all made of steel. Beehive projectiles do not
howitzers. project the flechettes fonwmd; they merely release them.
Bronchoconstim. Substances that lead to constriction of
A the bronchial tubes, the portions of the windpipe that go
to each lung.
Acoustic Truzurm. Injury caused by sound.
Brownian Motion. The motion imparted to very fine parti-
Added Concentration. The percentage of an inertan~ such
cles held in suspension in a fluid and caused by impacts
as nitrogen, carbon dioxide, etc., which mist be added
by molecules of the fiuid.
to air to assure that the fUeI-air mixture is inert
Burn. A chemical reaction-fire-the rate of which is gov-
AGT-1500. h engine used in the MUMIAI MBTs.
erned primarily by the beat applied to the fuel reacting.
Aiveofu.s. Air cell of the lungs. Afire can range from glowing combustion to a defhgra-
Anaerobic. Absence of free oxygen. tion.
AntIfim2icrMe. Something or method that precludes explo Burn, First-Degree. Abnormal reddening of the skin (ery-
sion of one explosive-filied device from initiating a sim- thema) without blistering; can be painful after seveml
. . ilar reaction in an adjacent explosive-fled device. -. hours; typical example is sunburn.
ASA Exposure Index or Film Speed. A measure of the sen- B&, Second-Degree. Abnormal reddening of the skin with
~sitivity to tight of the film and that is calibrated in accor- blistering. Touching or pricking the skin in the burned
dance with American Standards Association (ASA) area produces pain. Deeper layers of the skin have been
..y. —
~requirements. (This exposure index or film speed is used

,,,,,
o
,,,t,’~!l,,
,, ,,
by a photographer to establish the apemwe setting, exp~
sure time, and mtificial lighting requirements when tak-
ing pictures. A film may have different exposure indices
B-

B-
damaged
Third-Degree. Destruction of the full thicknesses
skin and often of deeper tissues including bone.
Fourth-Degree. At one time, used to describe a burn
of

or fihn speeds for daylight or artificial (assumed to be

well into the muscle, possibly to the bone.
fim tungsten) tight The higher the index, the less light
needed for a proper exposure,)
Ataxia. Lack of norrnrd coordination, especially inability to
c
coordinate voluntary muscular movements. Gzndeliz (cd). Unit of luminous intensity in the direction of
rhe normal.
B Clm&ter Rotutdir. Like large shot gun shells. ‘l%e canister
. slugs are cylindrical steel missiles with a mass of 5.1 g
BaWstic Damage. Damage to equipment resuIting born the
or weight of 79 grains. ~ese were used in World War
impact of bulles projectiles, shaped-charge jets, fmg-
II, Kora and Vietnam by US forces and were fired pri-
ments, blas~ etc.
marily from antitank or tank guns for antipersonnel use.
But& Dress Uniform (BDU). Uniforms designed speci& See also Beetive.
tally for use in combat; the BDU in use is made of 50%
C2zrbo#temogfuMn. Compound formed by carbon monox-
cottom 50% nylom usually 237 g/m2 of a 2:1 left-hand
ide and hemoglobm during poisoning by carbon monox-
twill weave and usually with a camouflage pattern.
ide.
J%zzooti. The early 59.9-mm (2.36-in.) antitank rocket
C’kMs A. Fires in ordinary combustible materials (woq
launcher that resembled the “musical instrument” used
clolh, paper, rubber, and many plastics) that require the
by comedian Bob Burns. Burns called his instrument a
heat-absorbing (cooling) effects of water or water solu-
‘%azooka”, and this name has stuck to the rocket
tions, the coating effects of certain dry chemicals
launcher since World War II.
(which retard combustion), or the intemupting of the
Beehive Prq”ectdes. PTclmame for antipersonnel (APERS) combustion chain reaction by halogenated agents.
projectiles. Similar to the shrapnel projectiles, but the
Ckrss B. F~es in flammabIe or combustible liquids, tkunrna-
submissiles are flechettes rather than spheres, Beehive
ble gases, greases, and similar materials that must be put
projectiles were used in Vietnam and were made for

o .:;
,,,,
C’d’!
i“
: artillery rounds with 0.81-gram (12-gmin) flechettes and
for 2.75-in. (7(hm) folding fin aircraft rockets (FFAR)
out by excluding air (oxygen), inhibiting the release of
combustible
chain reaction.
vapors, or interrupting the combustion

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MIL-HDBK&4
C’tiss. C,.lhsin..live. electrical. equipment;. safety of the i~plies the b~ing ofl.asubstance with self-contained
operator requires the use of electrically nonconductive
extinguishing agents. (Note: When elecrnc’d equipment
...-. .. : .. ...-.is deenergized, extinguishers. for Class A or B fires may
be used.)
oxygen so that the reaction zone advances into the unre-
acted materi~ at less than the velocity of sound in the
umeacted material. The term is often used to refer to the
action of a high-explosive projectile, which upon
e
“:- ~.Class D. Fires in certain combustible metals (magnesium, impact with a target does not produce the usual effects
titanium, zirconium, sodium, potassium, ”etc.), which of a high-order detonation. See also Detonation and
require a heat-absorbing extinguishing medium. that, Bum and Combustion and Explosion.
does not react with the burning metals. ‘, ‘, ., . Detonatt”on. An’ exotherrnic chemical reaction which propa-
.,
CoZd Work.” Permanent strain produced by an external force: gates with such rapidity that the rate of advance .of the
..’. . in a metal below its recrystallization temperature. reaction zone into the unreacted material exceeds the
Combat. Development Test. Requirements for-kc Army in’ velocity of sound in the unreacted material, i.e., the
the field, or a study that conrnbutes to such determina- advancing reaction zone is preceded by a shock wave.
.. . See also Deflagration and Burn and Combustion and
tion.
,,. Explosion.
Combht.Vehi& Crewman (CVC) Helmet or Unz~orm. Hel-
met or uniform developed especially for use by crew- Dust. Dust is finely divided material in solid form that can
,: men in combat vehicles. The helmet inchides provi- remain airborne for a, significant period of time, sec-
“ sions for ‘the earphones needed for the vehicular orids or niinutes, after being agitated. See also Mist.
. . intercommunication and radio equipment. Dysfunction. Impaired functioning.
. . Ctimbustion. The. continuous rapid combination of a sub-
,., stance with various elements, such as oxygen or chlo- E
,... rinei or witi” various.. -oxygen-bearing compounds Elastorneti. Rubber-like plastics. .-,
accompanied by the generation of light and heat. ~
Electric Arc; ~ electric discharge through air. The arcing
Computer ~odeL The program necessay to perform ,senes between the anode and cathode of a spark plug is one
.. . . . of operations on a computer. This program hai a logic example; lightning is another. When the ‘insiildtion on
.: flow in which a series of logic steps and mathematical & electric conductor is removed, arcing often occurs.
- models are used to produce and document results horn
a specified set of inputs; thus a task is pe~ormed. See
also Mathematical Model.
Electric arcs produce ultraviolet radiation.
●
F
Cone Calorimeter. A laboratory device used to’ measure the
Fire Extinguishment. Using extinguishants to eliminate
rate of heat release of a material during combustion.
combustion whether that combustion is sustained or
Cored. Cut or bored out, i.e., when a projecti~e cuts out
not,
..” some of the material, as an apple corer cuts out the core
Fire Prevention. Measures taken to preclude ignition of a
of the apple.
Ilre or, if ignition does occur, to assure the combustion
~~
~”:Count. The rate of ionic discharges (discharges per second)
is not sustained.
established by an ionic discharge instrument. “(Refers to
Fire; Suppresswn. Both fire prevention and tire extinguish-
the frequency of “ionic discharges’ detected by a Geiger-
-,, ment.
Mueller device.) .,
Fires, Large and Small. For specifying desired optical fire
Cover. A location where terrain features prevent direct fire
sensor performance, US Army Tank-Automotive Com-
onto a vehicle or person.
mand has classified hydrocarbon fires as large or small.
A large tire produces radiation similar to that produced
,, D
by. a 76-~ finirnum depth of 840 cm3 of diesel fuel
Document Acqui.rton Number (DAN). A, number used by DF-2 in a 130-mm diameter pan at a distance of 380
. . . the .Survivability Information and Assessment Center mm from the sensor being tested. A small fire produces
(SURVLAC), Wright-Patterson Air Force Bi%e, OH, to radiation sirhilar to that of the large fires, except that the
identify incidents in the Battle Damage Assessment and distance to the sensor is 1200 mm.
Repair Program database. Fkk. Abbreviation for flugzeug abwehr kannone, which is
Dej&r.de. Behind cover, i.e., behind a till or mound that pre- German for aircraft defense cannon. Since during
cludes impacts by direct fire weapons. See also Hull- World Wars I and H, we in the US and United Kingdom
Defilade. (UK) were usually on the receiving end, Flak came to
De@gration. “Very rapid combustion sometimes accompa- mean antiaircraft artillery fire.
nied by flame, sparks, and/or spattering of burning par: Flammability Characteristics. The characteristics by which o
., titles. Although classed as an explosion, it generally a material ignites and bums. These characteristics
.,

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. .. include the-material melting poin~ tbe .bofilng poin~ the that melts when a predetermined amperage of current
(,!(:(’ vapor pressure versus temperature, the kindling temper- flows.
i’
!, ature or flash point, the specific hea~ the thermal con-
o Fuze. & object used to initiate functioning of artillery pro-
.- ductivity, the heat of combustion, and many other prop-
.. jectiles, aerial bombs, and missile warheads, which
erties. have advanced so that simple, combusting fuses are no
Fkr.sh Point. The lowest temperature at which combustion longer adequate. To differentiate the more elaborate ini-
of fuel vapor can be achieved over a liquid surface. The tiation device from the burning fuse, the US mititary
fbsh point of a liquid is used to gage relative fire safety. has adopted the convention of calling the more elabo-
Fog. Vapor condensed into fine droplets huge enough to rate device a “fuze”r The devices used to iniriatedRw
scatter light and to obscure vision. Fog droplets range objects are often quite complicated. Fuzes can initiate
in diameter from 025 to 1.00 pm and remain sus- on contact~kd superquick+x after a finite delay
pended in air through Brownian motion. See afro Mist following impact+elay. Fuzes can “sense” an object
und Spray und Vapor ad Dust. and initiate a short distance away-proximity. Fuzes
Free Radids. ChemicaJ species (molecuIes) that have can initiate a given time after firing--time. Fuzes can
unpaired electrons. These species are very energetic be mounted in the front (nose) or the rear (base) of the
and chemically reactive and are capable of promoting projectile.
and pmticipating in chemical reactions, such as com-
bustion. G
Freon. Trade name belonging to E. 1. Du Pent de Nemours Geiger-Muef&r. A gas-tilled ovoid chamber with an anode
and Company for halogenated hy-&ocarbons.’’Halon” is (fine wire) along the axis and the chamber wall as the
an industry name for the same materials.. cathode. .When a quantum of radiation enters the chamb-
Fresnel Lens. A succession of concentric rings, not neces- er, the radiation impacting the gas molecules results in
sarily circular, each of which is an element of a simple iotition of the gas. The electrons move to the itwde
lens, assembled in proper relationship on a flat. surface and ‘cause a change in voltage between the anode and
to provide a short focal length and used to concentrate . . . the cathode. This change-in voltage can .be detected by

ol,~jf
~~ Iight expanding from a point source into a relatively an electronic instrument. When the frequency of radia-
narrow beam. Named for Augustin Jean Fresnel (1788- tion impacts is low, the instrument can count the num-
,, 1827), a French physicisl who was a pioneer in optics. ber of impacts per unit of time. When the frequency is
Fresrd lenses are made from plastic quite economi- high, the instrument can measure the output current,
cally and can therefore be used in baMistics tests in which is proportional to the radiation intensity.
which they will probably be destroyed. Grand Muf. V~olenti epileptic-like-seizures.
Fuel. A generic term denoting a material that will combine Ground Far@ Interrupter. A very high-speed electronic
with an oxidizer in a combustion process in which tilt breaker.
energy is generated. Fuel is used in three specific
instances in this handbook: (1) MobiIity fuels are mix- H
tures of liquid hydrocarbons that are burned in internal
Haif f-Stop of Light. A camera with an adjustable lens pro-
combustion engines to propel vehicles, to produce elec-
vides several aperture diaphragm openings to control the
trical power, or to provide other stationary power needs,
amount of light entering the camera. These full-stop open-
(2) Solid fuek are also used in explosive or pyrotedtic
ings are usually designated f72.8, f74, t75.6, t78, ff 11, i716,
mixtures to fuel solid propellant rockets; to produce
and f122. 13ach full-stop opening passes twice as much
bh.sL ligh~ or smoke; or to launch bullets or projectiles,
light as the finumber following; f12.8 passes the most
and (3) Fuels for fires can be any combustible material.
ligh~ and ~ the least. A half stop such as f/3.5 would
Fuel Tbr& Fuel Ceff. In this handbook the fuel container be halfway between f./’8.8and t74 in the quantity of light
in or on a combat vehicle is referred to as a fuel “cell” passed. Referring to a light source as providing a half f-
to preclude confusion with the heavily armored combat stop of light means that the extra Iight on the object being
vehicle, the tank.
photographed is equal in effect to opening the diaphmgm
Fuse. An object &a& when lit at one end, will bum at a a half f-stop.
fairly welldt$med rate, dependent upon the combusti-
Hahn. Halogenated hydroctions that are used as fire
ble material used to ignite some material at the other extinguishants. ‘i%e most common used in vehicles are
end-for military purposes uswdly either an explosive
Halons 1,301 and 1211.
charge or an incendiary-a desired time later. ‘llte fuse

o ,;f’:jr!
,;. ,,:
functions by burning a filler, and the burn time is usu-
ally established by the length of the burning material.
Fuse is aIso used for the device in an electrical circuit
Heat Flux Grfon%zetry. Use of a heat-measuring device,
calorimeter or heat fiux sensor, to measure the rate of
heat flow.
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MIL-HDBK-684
Heat Rejection.. Aterrmind~cating hat heat he been trans- was a low.-density salad,.. which was discarded upon
ferred from an object to a cool~t. When cooling an muzzle exit. When the greater effectiveness of long-rod
engine, heat is “rejected” by the engine to the coolant penetrators was appreciated, the penetrator was length- 0
:liqyid; which later “rejects” this same heat to the ~ ened and fins were installed to obtain aerodynamic sta-
flowing through the radiator. In ~-cooled engines heat bility. These rounds are called armor-piercing, fin-stabi-
is rejected directly to the air. li?ed, disc~ding sabot (APFSDS). Projectile velocities
Hemoconceratration. Thickening of blood that results when cap exceed 1372 mls (4500 ftk).
water is lost from the blood.
L
Hstotoxic Anoxia. Tissue poisoning due to lack of oxygen.
Hull Lle$krde. A tank is in hull de filade when it is behind a Lean Limit. The smallest fuel-vapor-to-air mixture ratio at
mound and the hull is in defilade, so only the” turret is which sustain~ burning can occur.
exposed to direct fire from the front. Learning Curve. Manufacturers? pa-titularly aerospace
Hydraulic Ram. The conversion of.kinetic energy to a pres-’ contractors, when estimating the cost of a product that
sure within a liquid. The kinetic energy caq be that pos- is to be produced in quantity, use an exponential--curve
sessed by the liquid itself, as when flowing liquid is to estimate what the final product cost will be after their
suddenly stop~d, or that possessed by a moving object personnel have “learned” how to fabricate and assem-
which, enters the liquid, as a projectile or shaped-charge ble the item. These “learning curves” are based upon
jet which enters a fuel cell. experience and are used to estimate labor costs.
Hydroijlic StubiMy. The fluid cannot absorb more water Limp Home. The capability of the vehicle to move to a safe
and change its properties when exposed to; atmospheric area after sustaining damage.
moisture. Live-Fire Tests. Tests of military equipment prescribed by
Hygroscopfi. Readily absorbs and retains atmospheric Congress in 1986,
moisture. ,..
Hyperpyrexia/llypedhermia. Fhgher than no~al body M
temperature. Ml Main Battle Tank (MBT). Called the Abrams for GEN
Hypoti. Lo’wering of the oxygen content in thk blood. Creighton Abrams. Turbine-powered and uses diesel
fiel or JP-8; mounts 105-mm gun (M.lA1 and A2 have a
,1 120-mm gun.), steel hull; has automatic HaIon 1301
fixed fire ex~nguisher systems (FFES) in crew and
Ignition. The’ action by which combustion, bum, or fire is
. engine compartments. The M 1 and M 1A 1 have high-
started. (Compare to initiation.)
density polyethylene fiel cells.
Impediment. Supplies carried by individu~s, military
M2 and M3 Brgdley FigMing Vehicles (BFVS). M2 is the
organizations, or vehicles.
infantry version, and M3 is cavalry. Mount 25-mm gun
Znqus. See Ossicles.
~lus tube-launched, optically tracked, wire-guided
,.
initiation. As applied to an explosive item, the beginning”of (TOW) missiles, diesel powered, aluminum hull, has
the deflagration or detonation of ye explosive. ,. automatic Halon 1301 FFES in the crew compartment
.
,’ Intumescent Coati~g. A coating that exp;ds when and a. manually activated Elalon 1301 FFES in the
., exposed to the heat of flames and forms a char. The char engine compartment. The BFVS have rotary-molded
has a low thermal conductivity and therefore. reduces nylon 6 fuel cells.
the heat tmtnsfer horn the” flames to the material pro- M48 MBT. Mounts 90-mm gun, except M48A5 mounts
tected. In short, reaction of the intumescent coating 105-mm gun. M48, M48A1, M48A2 were gasoline
insulates the material on which it is placed. powered; M48A3, M48A5 were diesel powered with
welded aluminum fuel cells and a steel hull. M67 was a
.K fl~e thrower version. M48 armored-vehicle-launched
,,

Kinetic ‘Ener~ Penetrator. A solid, very hard antiarmor bridge has M48 hull and engine.
projectile that impacts armor at a high velocity and uses M60 MBT. Mounts 105-mm gun, diesel powered, steel hull,
kinetic energy (ICE) to damage the target. LnWorld War manually activated carbon dioxide FFES in engine
II these steel p~ojectiles were called armor piercing compartment, and has welded aluminum fuel cells.
(AP). Material advances led tohardened steel, tungsten M60 armored=vebicle-launched bridge and M728 CEV
,.
carbide, and depleted uranium (DIJ) penetrators. TO use same chassis.
avoid higher than normal aerodynamic drag on the M109 and MlIO. SP Howitzers. Aluminum hull, diesel
tungsten carbide penetrators (which had a smaller engine, and welded aluminum fuel cells. M 109 has m
“diameter than the gun tube), the bulk of the projectile 155-mm howitze~ Ml 10 has 203-mm (8-in.) howitzer.

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.. B2247 DXVAD (Sg% York). Divisional akdefense vehicle, Mucosa. Mucous membrane- .

o
;~~~
.i k028
now cancdled; used M48A5 hull and engine.
CEV Combat Engineer Vehicle. Has 165-mm demo-
iit.im projector. See ako M60.
N
Napalm. Gelling agent used with hydrocarbon fuel, such as
Maguzim Rij?e. A tie into which several camidges can be gasoline, to make a thickened fuel for use in incendiary
loaded so that the user need not load each cartridge sep weapons such as a flamethrower, fourgase (a large
arately. l%e use of the magazine rifle permitted soldiers incendiary Iand mine usually initiated by an observer),
to fire from the prone position and greatly reduced their or aerial bomb.
vulnerability and enabled them to fire more accurately h’arcotic.Substance that in moderate dosage allays se~lbil-
at a much higher rate. Because tltese magazine rifles ity, relieves pain, and produces profound slee~ how-
were loaded at the breech rather than the muzzle, the ever, in greater dosage produces stupor, com~ and con-
soldiers did not have to expose themselves to reload vulsions.
their weapons, and the use of spin-stabilized projectiles
Nasophaynx. Upper part of the pharynx continuous with
greatly increased the effective range and accuracy of
the nasal passages. The pharynx is the part of the ali-
the weapon.
mentary canal between the cavity of the mouth and the
Mrfleus. See Ossicles. esophagus (gullet).
iWlhematical Modef. Mathematical models are a series of Nuclear Hardening. Modifications made to hardware so it
mathematical operations that convert input parameters will resist the electromagnetic pulse (emp) effects of a
into a desired output parameter. An example of a math- nuckar weapon explosion.
ematical model relating the mass of a body m and the
rate at which that body is being accelerated a by an
unbalanced force F is F = m . a. Mathematical models
o
are components of computer models. See also Com- On-Vehick Equipment (OWE). Equipment stowed in or on
puter Model. the vehicle that are necessary for operation and/or
ikfifilivy Stress Situations. Specific combat situations in . . maintenan~ of-the vehicle,. such as gxds, ywqon-
which soldiers must function and for which specific cle.aiing tools, etc. ‘fhese items are listed in the-vehicu-
# manual ancl/or mental fictions are required lar maintenance manual.
,,,~~
!,
o “ Mirz. Liquid droplets greater in size than 1.0pm but can be Order of Magnitude. An order of magnitude is a factor of
up to 5.0P. For these mist droplets the gravitational ten, i.e., if one object is measured in tens of items and
force is relatively small compared to air cuments. Mist anorher in hundreds of items; thus the second object is
droplets will not remain permanently airborne by said to be an order of magnitu& greater than the firsL
- Brownian motion alone. See also Fog and Spray and OssicJks: Mafkus, lMcus, and Stapes. Three bones, or ossi-
Vapor and Dust. cles, of the ear. The malleus, or hammer, is comected to
Mofotkw Coek&rif. An incendiary device consisting of a the eardrum, or tyrnpanic membrane. ‘llte:stapes, or
gl~ bottle that contains gasoline or another liquid fuel stirrup, is connected to the walls of the oval window at
and an external igniter. In use, the external igniter, the entrance to the cochl% or inner ear. The incus, or
which is normalJy a gasoline- or oil-soaked rag, is anvil, connects the malleus to the stapes.
ignit~ and the device is thrown onto a target so the OverPressure. Timsient pressure rhat exceeds atmospheric
glass bottle breaks. Molotov cocktails were used by the pressure manifested in the blast wave from an explo-
F- against Russian tanks in 1940 when the USSR sion.
invaded Finland. The Finns reputedly named these for
the Soviet Foreign Minister, V. I. Molotov, stating that P
these cockmils were for the consumption of-Molotov’s Plug. Part of a. mrget cut out by a flat-ended projectile,
errissaries, the Russian tankers. much like a cookie cutter removes a circular piece of
i%fonobbc. Essentially one-piece armor. A single thickness dough. The piece removed is called a plug and usuaUy
of material, as opposed to multiple layers of possibly leaves the target with the same velocity as the residual
different materials with or without air gaps between penetrator.
layers
Pokrgraphic. A method of qualitative or quantitative anal- ‘“.
Moth&dL To ‘tiothball” is to prepare an item of equipment ysis based on current-voltage curves obtained during
for long-term storage and then to store the item. Some electrolysis of a solution with increasing electromotive
essential maintenance may be required during stomge. force.
,!!),/!,, ‘ Basically, the item is availabl% but some preparation Pounder fpdr). l%e British designate theix cannon by the
‘,,,,,.[ will be necessary before the item can be used.
D

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MIL-HDBK-684’
, weight of .-the. high-explosive shell .fire~” e.g., the 25 Shaped-Churge. Jet. A dxape.d-charge or high-explosive
pounder that had a caliber of 85 mm (3.35 in.). antitank (HEAT) warhead is a chemical energy warhead
Pour Point. The temperature at which a liquid has a low that has a copper-lined, conical cavity in a high explo- 0’
~:enough viscosity to flow. sive. As the high explosive detonates, part of the copper
liner is accelerated into a very fast-moving jet (jet tip
fiessuke Attenuator. A device to reduce pressqre spikes.
ve~ocity is approximately 7620 nds (25,000 ft/s)),
l$obit. Unit of measurement of statistical probability based
which is followed by the liner in the form of a slug. The
on deviations horn the meamof a normal frequency dk-
slug is moving at approximately 244 m/s (800 ft/s). The
tribution.
shaped-charge, jet- applies an extremely high impact
Purpk? K. A, trade name fo~ a powdered dry chemical fire pressure on the armor.
.extinguishant consisting primarily of potaksium bicar-
Shot. Used in a tank commander’s fire command for inert,
bonate but with a small amount of pwple dye added.
kinetic energy (ICE) projectiles. Also used in testing to
describe a single event that uses either a KE or shaped-
R , .,
charge projectile.
Rack Setting. The position to which the rack is adjusted to Shrapnel. An artillery shell’ containing a large numlkr of
obtain a desired diesel fuel injection rate. submissiles; usually lead balls, and a propelling charge
Radiution Liner. A liner usually contiguous with the inne~ that is exploded in air, usually by a time fuse or fuze, so
vehicular wall, which captures fast neutrons and that the balls are projected toward troops from above.
gamma radiation. Slug. Rearmost potion of the metallic liner of the shaped-
Reflected fiesswe. Total, or stagnation, pressure applied charge jet. This is the slowest moving portion of the jet,
normally, i.e., perpendicularly, to a surface. In some approximately 244 mls. The slug may contain much of
instances “reflected” is applied to shock waves, ”i.e., the liner,
waves that echo horn v~ous surfaces. Sornan. A nerve gas, GD.
Reticulated Foam. An open cell polyether or polyester SpalL men a ballistic penetrator ~mpacts a target, stress
~~.~ polyure~ane foam used in the ullage of militaryaircraft waves pass thi-ough the material and reflect biickward
fuel cells to preclude explosio~ of the fuel vapor and horn the far side of the target. When these waves-com-
air. Also used in void spaces adjacent to fuel cells to bine with o~ers in the @rget, the target material can fail
preclude fires within. This material confonrk to MIL- in tension. Men broken free, the target material is *
B-83054. c~led span. Span can have a significant velocity, par- “
Rich Limit. .~e greatest fuel-vapor-to-air rni&re ratio at titularly from a shaped-charge jet impact. These parti-
which sustained burning can occur. cles are usually thrown outward from the side opposite
Ro@y Molded. A fabrication process in which. @anules of that impacted by the’ penetrator or blast. In combat
a thermoplastic are taken above @e melting point in a vehicles the span is usually metallic.
mold :that is rotating about two orthogonal axes.. The SpaZl Curtains. .Layers of ballistic fabric, bonded or
temperature is gradually lowered so that the plastic qnbonded, which are intended to trap span.
solidifies on the inside surface of the mold, This.proce- Span Liner. A ipall-trapping lining contiguous with or
dure produces a seamless, hollow part with a very con- spaced a short distance, e.g., 102 mm (4 in.), from the
stant thickness and very few built-in” stresses. ‘Ilk pro- metallic wall that can emit span.
cess can be ,used with many materials including nylon, Spectral Bands., Electromagnetic radiation forms a spec-
polyethylene, etc. trum by frequency or wavelength with electric or radio
Rust Inhibitor. A component added to the fluid which pro- waves at one end and cosmic waves at the other.
vides a coating on steel or iron components that pre- ,. Between these limits are heat rays including infrared
vents atmospheric oxygen contact with- the metal and and visible radiation, ultraviolet, X rays, and gamma
thus prevents oxidation or rust from forming. rays listed in order from longer to shorter wavelengths.

s .’ ‘“ In several cases these designations overlap. The spec-

tral bands are discrete sets of wavelengths or frequen-
cies of radiation that are emitted by materials when
Sm”n. A nerve gas, GB.
heated. These spectral bands are peculiar to specific
Seebeck Effect. Named for Thomas Johann Seebeck (1970-
bonds between atoms.
1831), an Estonian-born German physicist; who discov-
ered in 1821, that an electric current flows between dif- Spfu.rh. Metal that flows from the target in the opposite
ferent conductive materials when two junctions of these drection from that of the impacting projectile.
different materials are at different temperatures in a cir- Spray. A distribution of droplet sizes generally greater than
m
cuit. This is the basis of a thermocouple circuit. 5.0 microns in diameter. Sprays are usually caused by

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o#
.. _.. _ mechanical. action. such as a ball.hicimpact-on a liquid THgeminuflYerve. Fti ouifacird, nerve is the largest cra-
mass, a liquid being forced through an opening, or a liq- nial nerve. It is the great sensory nerve of the head and
,,!,,,
~:,
j uid jet impacting an object See Fog auf MM fkce and the motor nerve of the musclm of mastication.
. .Squib:.khbe. A vaIve actuated by an electroexplosive Trolond. A unit of retinal illuminan ce, the troland (td), is
&vice. based on the fact that the light passing into the eye is
Stapes. See Ossicles. proportional to the area of the pupil. The troland is the
retinal stimulation provided by a source of 1 cd/m2
Stick Grenude. German hand grenade, also called a “potato
viewed through a pupil of 1 mmz. The troland value for
masher: had a handle; the US oval hand grenade was
the stimulus is given byrd = 1 (cd/m2) xA(mm2),. where
called a “pineapple” because of the deep serrations in
A = pupil area.
the body. The ovoid grenade was thrown much like a
baseball, whereas the stick grenade was thrown like a
hatcheL u
S2raight Run DistLWe s. ‘I%ose hydromrbons that were U/loge. The vapor space above the liquid level in a liquid
inherently in the crude oil and merely boiled off and container, such as a fuel cell. The ullage of a fuel cell
then condensed. Cracked distillates are those resulting contains air and fuel vapor. These can be in a combusti-
fkorn cracking or breaking up of longer chain hydroca- ble or explosive mixture or can be too lean or too rich
rbon molecules. for combustion.
StoicAiometric Mriiure, A mixture of oxidizer and fuel in
which both oxidizez and fuel are completely consumed v
in a chemical reaction to stable products, e.g., . Vizpor. A substance in the gaseous state; vapor is molecular
2H~ + o~ + 2H*0. in size. See Fog and Mist.
.A projectile
Sdediber smaller in diameter than the bore of Vapor Lock. Fuel flow in a line blocked by vaporized fuel.
the gun from which it was fired. Vehicular SurvivaiWty. ‘Ihe ability-of a vehicle to “endure
SynergiSm. Cooperative action of discrete agencies that ballistic hits or other damage-and nor lose crew. mem-
causes a total effect greater than the sum of the effects bers or be destroyed.
Venti. %neipfe. Fluid flow in a channel is restricted so
that the rate of flow increases in order to lower static
A
pressure on the walls of the channel.
T- Constant. A measure of the quickness of response of a VXA-903 Curnmins. An engine used in the M2/M3 BIWs.
device to a change in input. For the temperature-sens- This is a diesel, 8-cyLinder, liquid-cooled engine.
ing devic~ such as a themnocouple, the time constant
is the time required for the device to reach 63.2% of its w
@al voltage given a step change in temperature.
Weeps. A very low leakage rate, more like a seepage than a
I’i%nti. Perceived buzzing, whistling, or ringing sound in drip or pour.
the ear that does not comspond to real physical stimu-
White Phosphorus. Pyrophoric material used as a filler in
lation.
smoke grenades and projectiles.

,,
O ‘j ‘j

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INDEX
A crew incapacitation, 8-33-8-34
AAV 7AI fire, 8-32-8-33
fuel storage, 4-17418 fire-extinguishing, 8-36-8-37
fire-extinguishing system, 6-15,7-32, 7-67—7-68 Ancillary power, 4-29-4-30,4-37-4-40, 7-37—7-38
ACAV. See APC Ml 13. vulnerability reduction, 42~1 ::
Accumulator, 4-33-4-34 Antifiaricide, 4-46-4-56
Actuator, 4-34,4-35 Antifreeze, 3-2&3-21
flimafl 7-35,7-73-7-76 APCM113
~ge ~efion, 7.74 fn data, 4-2,4-5
vulnerability reduction, 7-73-7-76 fire-extinguishing system 4-5, S28, 7-58
Alkali metal salt aqueous solutions, 7-15 t%el storage, 4-17418,4-27
Alkali metal salt powders 7-12 mentioned, 4-9,4-10,4-13,4-71, 5-14,5-17
Aluminq 7-31 APFSDS. See Kinetic energy threats.
Aluminum, 2-24 Aqueous foams, 7-10-7-11,7-27
Ammudamp@, 4-46 AIUAAV M551, 5-18,7-64-7-65
htrmmition mentioned, 3-23,4-9,4-71
caseq 3-23-3-24 Argon, 7-10
(chemical) Stowag% 4-56 Armor-piercing threats. See Kinetic energy threats.
explosive loading% 3-24,3-26 Armored pemonnel carriers, 4-2, 4-5, 4-9, 4-10, 4-13,
ba.zwds, 44243,4-54-4-56,5-17 4-16--4-18, 4-27, 4-67468,.4-71, 5-13, 5-14, -5-17,
ignition, 4-42-4-43 &I, &15, 6-27--6-28
in fuel cell, 4-4*6 Southeast Asia experience, 61
initiation, 4-4243 AsTB
main gun, 4-41 ammunition storage, 4-48,7-36
~O~tia.rl~ 3-23-3-24 fire-extinguishing system, 7-62
stowage, external, 4-62 he] storage, 4---67,7-37
stowing attitudefor WP-filled shells, 3-26 Atomel, 7-73
transportation, 442 Auxiliary power, noise, 4-38
vulnerability, 4-41 AWB, 4-2
Anmmnitiort magazine design, 1-3, ~51, 4-54- B
4-56,461-2, 4-tM---65,5, 469470,7-36-7-37 Blast effects, 5-3
antifratricide, 4-46-4-56 Background of fire detection, 6-1-6-2
barrier, 4-~5 Backup extinguisher, 8-29-8-32
compartmentalization, 4-61462 Backup fire-extinguishing systems, 7-55
explosive warhead% 4-44-4-51 Ballistic effects, 4-16.4-23, 442+3, 5-l—5-3
external stowage, 4-45,4-62 Ballistic foam, 7-74-7-75
intumescent coating, 4-69470 &dfistic VeS& 5-33-5-36
metal shields, 1-3 Banier, 4-U65, 4-66
~pe~t c~=, 4-54-4-56 Battle Damage lwessment Repair Program, 4-1,4-5, 4=41
separation, ~51 BFV M2, M3
water jackets, 1-3 fire daq 4-2
Ammunition magazin~ 4-6146Z 7-36-7-37,7-79 fire-extinguishing system, 615,6-31, 7-61—7-62
for specitlc vehicles. See each vehicle. fuel storage, 4-17
steel cover, 4-42 mention~ 5-53,7-37,7-38, 8-28
venteh 4-47,4-54,4-55 Bilge, 7-42
vulnerability reductiom 3-24, 4-42, 4-46, 4-47, 4-54- Blast waves, effect on crew, 5-50-5-51
458, 4-6Z 7-36-7-37,7-79 BMP, 4-16. See afso T-55.
warn-injection, 3-24,4-54 Body injuries, 5-32—5-42
Water-jacketa 4-54 Bottles, fire-extinguishing, 7-35
Anaiyses Bn fiel system, 4-)6
cos~ 1-8-1-10 Built-in test equipmen~ 7-56-7-57

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Burn criterion, 5-12—5-13 ,. ., . for life cycle costs, 1-9=J.A.0.
Burn tests, 5-7 COVART: 8-35,8-36
Burns, 5-5—5-7 Crew compartment, 7-48, 7-51—7-52 a
“:ch.hinfirotection, 5-11, 5-13, 5-1~5-17, 5-18—5-19 design, 7-48
criteria” for, 5-12 fire-extinguishing system, 7-48,7-5 1—7-53
effect on crew, 5-51 Crew incapacitation, 8-33—8-34
experience, 5- 17—5- 19 Crew perform~ce
test programs, 5- 13—5- 7 combustion effects, 5-49—5-53
related to system design, 5-52—5-53 .:
c requirements, 5-3
Calcium chloride, 7-24
CWbon dioxide, 5-45 D
“Carbon monoxide, 5-43 Data sources, 4-1,4-2,4-5,4-41
Carbon dioxide, 7-6,7-8,8-30 . Databases, 4-1,4-2,4-5,4-41
Cirbonic acid, 7-72 ~ Deflagration, 2-2 ~,
CARDOX@, 8-30 Design guidance, 4-8, 5-28’—5-32, 5-40,5-41,5-53,6-16
Cargo compartment, fire-extinguisl@g system, 7-48—7-49 Detectors, 7-54”
CEV M728, 4-2 , for combustible gases, 6-30-6-31
Challenger, 7-69 for gases, 6-29—6-31
Chemical energy threat, 1-2, 1-4-1-5. See also Shaped- for noxious gases, 6-30
charge threat. for optical effects, 6-4-6-16
Chemical intervention agents, ‘7-11—7-23 : ~. . for oxygen, 6~30
Chemical munitions, antifratricide, 4-56 , for penetration, 6-27-6-28,8-14 ..
Chieftain, 7-69 for smoke, 6-28-6-29
Churchill VII. See Flamethrower. for thermal effects, 6-16=6-27, 8-l&8-15
Cluster bomblet, 1-5 Detonation, 2-2
Coatings. See Paints. DF-A; 3-2
Combat Lifesaver, 5-10 DF-1, 3-2
Combat service support vehicles, 4-1,4-2 ., - DF-2, 2-22,3-2,3-3,3-8,3-9, 3-21
Combat support vehicles, 4-1, 4-2, 4-5, 4-18A-19, 4-31, Diesel engine, 4-11-4-13
7-64 Direct-fire threat, 1-4
Combat vehicles. See Vehicles, combat. “’ . DIVAD M247, 4-2
Combustible metals fires, extinguishants for, 7:31 Double-walled cell, 4-20-4-21, 4-62A-63, 7-39—7-40
Combustion gases, 2-3—2-8, 8-16-8-19
Combustion, products of, 4-58+60, 8-16-8-19 E
Combustion- resistance, 3-9—3- 10,3-13,7-42 Eardrum rupture, 5-22—5-23, 5-25, 5-32
Compartmentalization, 4-61462,4-634-64 ‘ tests, 5-28—5-32
Compression ignition engine, 4-11-4-13 Elastomers, 3-29, 3-40,3-45
Computer models, 8-32, 8-35—8-37. See also Models Electric system, 4-39440
Concussion, 5-42 Electric power, 4-37440
Conduction, 5-5—5-6, 8-13-8-16 vulnerability reduction, 4-37-+4 1, 7-36-7-38
Contaminants of combustion, effect on crew, 5-49—5-50 Electric wire insulation, 4-40
Continuous thermal detectors, 6-16-6-24 . Electrical installation, 3-28—3-29
Controls, fire-extinguishing systems, 7-5 L7-55 Electrical shorts, 4-4W-41
Contusion, 5-42 Elect@city and extinguishants, 7-27
Convection, 5-5—5-6, 8-13—8-16’ Electronic equipment, 8-25
Cooling agents, 7-23-7-31 ENDGAM, 8-36
Copper powder, 7-11 Engines, 4-10-4-16
Cost analysis compartment, 4-71, 7-48—7-49, 7-54
cost-effectiveness, 1-8—l -9 design, 7-48—7-49
for automatic fwe detection and suppression equipment for fue-extinguishing system, 7-48—7-49, 7-54
FAASV, 1-9 selection, 4-26
for automatic fue detection and suppression equipment for Equipment darnage, 8-34-8-35
M60 MBT, 1-8—l-9 Equipment tests, 5- 11—5-17
for external fuel cell, 1-8 Ethylene glycol, 3-21,7-24

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o,,,$
&t system, vulnerability reductio% 46=66 ~ifOnIK3.UCe,8-21 ,_-...
Explosafe@, 7-43,7-73 response requirements, 7-55
‘‘~* Explosions, 2-2 ships, 7-77
==:-.-Explmive=activated fire extinguishers, 7-34-7-36,7-71 survivability, 7-49
Explosive fillers, 4-53 test and alarm panel, 7-57
Explosives. See Munitions. Fire-resistant fuels,.3-9-3-10, 7-75-7-76
External cell, 4-66,469 Ftie-retardant materials, 7-42
Extinguishant vapors, 8-16 Fwes, undetected, 623
Extinguishants, 7-l—7-2, 7-*7-31. See a&o each agenL FfRESIM, 8-32,4)-35,%-36
and electricity, 7-27 Flamethrower, 451
chemical intervention agents, 7-1 l—7-23 Flaming tires, 2-2
comparison techniques, 7-5-7-6 Flash, effect on crew, 5-51
for combustible metals fires, 7-31 l%sb X my, 8-21,8-24-8-25
Russian, 7-72—7-73 Fluid flow, modeling, 8-37
Ftying particulate, effect on crew, 5-51 .-
Extinguishers. See F= extinguishers.
Extinguishing system- See Fnw-extinguishing systems. Foams, 7-10-7-11,7-27
Extinguishment, probability, 8-37-8-38 Fog Oti, 3-3,3-6, 3-21—3-22
Eye safety, 540,541 Frangible cell, 4-69
Freeze point suppressants, 3-20-3-21,7-24-7-25
F Fresh water, 7-23,7-27
F-V M95?L fire+txtirtguishing system, 1-9,7-6$ Fuel. See a&o Mobility fuels.
Fabrics. See Textiles. excluders, 7-6
Fighting vehicles, 4-2, 4-17, 5-53, 6-15, 6-31, 7-37, 7-38 fire-resistant, 3-9-3-10,7-75-7-76
7-61-7-62,8-28. See ulsa MC M113. hazards, 425
FIO- ,8-37 heating, 4-12
Fire by-products, 8-1=-19 leakage, 7-74 .-
Fire extinguisher vahq 7-33-7-35 lines, 4-27
m Fire extinguisiwrs, 7-32–7-47, 7-54,7-58,7-71,7-75, 7-77 Fuel cell, 1-3,4-16-419,4-20-423, 426-4-27,466-
w bottles,7-35 468,7-37,7-39-740,7-42-7-77
controls, 7-54 confinemenk 7-42,7-43
explosive-rtctivaterl 7-34-7-36,7-71 double-walkxL 4-19-4-20,4-62463,7-39-740
linear, 7-35-7-36,7-75 external, 1-3, 7-72—7-73
portabl% 7-44-747.7-58 frangible, 469
powder-filled panels, 7-38-7-39
fuel barrier for, 4-21,423,466
for test site. See Test events, preparation. jacket~ 4-19--420,4-62463,7-39-740
twinned agent Wit, 7-77 jettisonable, 4-68-4-69
Fire ~OWth, 8-36-8-37 material, 4-19-4-20, ?-43
Fire initiation, 8-35-8-36 reticulated foam filIer, 4-67468
Fm prevention, 7-3&7-44, 747—7-49 mptu~, 4-16-4-23
FR protection techniques, 4-1 Self-sealing construction, 7-74, 7-7*7-77
Fire-resistant i%el, aircmft, 7-75-7-76 Fuel system, 4-17418, 4-19, 4-2%23, 4-24-425,
Fm signatures, 6-3 7-37
Ftre suppression, ineffective, 4-26-427 confinemen~ 7-42-743
Fro-extinguishing SyStemS, 7-2—7-5, 7-3G744, 7+7— Fuel system, vulnerability reduction, 3-9-3-10, 420-
7-58,7-?5, 7-7f, 7-78,8-21,8-36-8-37 623,462463,466,4-68-469, 7-37,7-42-743
active, 748 Fuel vapor explosion, 2-6-2-8
aircmfL 7-35,7-75 Fuel vapors, 8-i6
backup, 7-5.5 Fumes, effect on crew, 549,5-50
components, 7-35
design, 747—7-48 G
distribution, 7-51—7-54 Gas concentration, 8-16-8-19
effectiveness, 7-2—7-5 Gas detectors, 6-2M31
functioning Io@c, 7-50-7-51 Gas pressure, 8-13
manual activatio~ 7-57—7-58 Gases, irritan~ 547
number of shots, 7-54-7-55 Gasohol, 3-6-3-7

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MIL-HDBK-684
.. Gasoline” engine,4-14 .. .,,-,1.
Gelled water, 7-40 Ice, ‘7-40
Glowing fires, 2-2” Ignition, 2-2—2-12, 2- 13—2-17, 2-20,8-20
.. Godsave’.sLaw, 2-4 by a heated sw$ace, 2-8,2:21, 3-17—3-18
by blast threats, 2-16-2-17
H by incendiary threats, .2-16
Halogen-containing hydrocarbons, 7-17 by exploding charge, 2-t&2-8
Halon 1301,.8-30 by chemical energy threat, 2-16-2-17
Halon-containing nonhydrocarbons, 7-20 by ‘kinetic energy threat,- 2-”13-2- 14 ----
HaIon replacements, 7-20 by electricity, 2-20,4-41
HaIon alternates, 7-20 by hot p~cles, 2-8
Handheld extinguishers, 7-44-7-47. of munition, 2-.13—2- 16
Hazards, 4-.16, 4-25, 4-42443; 4-59, 4-60-4-61, 5-9, of spray, 2-4-2-5,2-8,3-14-3-18
5-13,5-14,5-15,5-17. See also Crew performtice. of mist, 2-4-2-5, ‘2-8, 3-14-3-18
“Hearing safety, 5-28—5-32 of vapor, 2-2-2-4, 2-6
Heat, effect on crew, 5-5 I ,-.
of liquid, 2-8, 3-16-3-17”’
Heat flux, 8,4, 8-15—8-16 source generation, 2-8—2-12
Heat fluk sensors, 8- 15—8- 16 Impedimenta, 7-42
, Heat sensors, 8-15—8- 16 Incapacitation, an$ysis, 8-33—8-34
Heat transfer, 5-5-5-6, 8-13—8-16 Incenciiary threats, 1-5
HEAT. See Chemical energy theat.
Inergen@, 7-10
Heated .air, 5-9 Inju~” :
Heated fuel, vulnerability reduction, 4-12,4-13 by noxious substances, 5-42—5-49 .. . ..
Heaters, personnel, 4-27,4-29 .
to body, 5-32—5.-42
.Helium, 7-10 to eye, 5-39—5-42
High arousal, effect on crew, 5-51-5-52 . to he~ng, 5-22—5-25
High explosives, 3-24-3-26 Insensitive munitions, vulnerability reduction, 4-524-53
~gh-explosive plastic, 2-16,2- 17,’3-29,5-2 Instrumentation’requirements, 8- 1—8-3
High-explosive squash head. See High-explosive plastic. @
Intumescent materials, 7-37,7-40-7-41
Hit locations,, 4-54-10,4-44,4-45 .Intumescent coatings, 7-4&7-41
Host installation hazards, 4-16 . Ionization smoke detectors 6-29
Human incapacitation criteria, 5-19—5-20, 5-25, 5-32— IR detectors, 6-13
5-33,5-36-5-38
Human performance, 5-52-5-53 J
,, Hydraulic fluid, 2- 18—2-20, ”2-22, 3-10-3-18,’ 4-29— Jacketed cell, 4-2M-21, 462-4-63, 7-39—7-40
4-30, 7-37—7-38 Jet A, 3-6
aircraft, 7-75—7-76 Jet A-1, 2-22,3-2,3-3,3-6,3-9, 3-21
,, combustion resistance,.3- 10-3-14 Jettisonable cell, 4-68469
fittings, 4-37 JP-5, 2-22,3-2,3-6,3-8,3-9, 3-21
IWL-H-5606, 2-22,3-13,3-14,3-16, 3-17 J’P-S, 3-2—3-6
,. IWL-EI-6083, 2-22,3-13,3-14,3-15, 3-16 JP-4, 2-22,3 -2,3-3,3-5,3-6
MIL-EI-19457, 3-14 JJ@, 3-2—3-6, 3-7,3-8,3-9,3-21
MIL-EI-22072, 3-13 JS-3, 4-68
MJL-H-46170, 2-22,3-13,3-14,3-16, 3-17
ML-H-531 19,3-13 K
MJL-H-83282, 2-22,,3-13,3-14,3-15 Kinetic energy threats, 1-2, 1-5,2-9
reservoirs, 4-32433 KV-2, 4-8
vulnerability reduction, 3-10-3-14, 7-37—7-38
L
Hydraulic lines, vulnerability reduction, 4-35,4-37
Land mine attack, 4-5
Hydraulic power, vulnerability reduction, 4-3 W-37,
LAV 25,7-68
7-37—7-38
Le Clerc, 4-38
Hydraulic pump, 4-32
Leopard I (Canadian), 7-68—7-69
Hydraulic ram, 4-19-4-20, 8-=8-1 1
Leop~d 11
Hydraulic reservoir, 4-32-4-33, 7-37—7-39
fire-extinguishing system, 7-68—7-69
Hydrogen cyanide, 5-44--5-45
detection, 6-31
Hyperthermia, 5-7—5-9

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MIL-HDBK-684
Lessons karned .M

o ,:1,
/:,
;‘~ ammunition magazine design, 7-79
-ancilliary power, 4-374-38
“ ~- ‘.arrmqrmection, 4-70
Ml (Abrams)
ammunition storage, 4-47,7-36-7-37
fire da% 4-2,4-37,7-2
ballistic fabric Selectiom 4-60 fire-extinguishing systerrL 6-15,6-16,7-60-7-61
bilge design, 4-25 fuel storage, 4-17
chemical ammunition stowage, 4-56 fuel system, 4-27
crew needs in combaL 4-70 mentioned, 4-10,4-14,4-16,4-29, 8-28
electric fusing, 440 M106, 4-5
electric wire routing, 441 M125, 4-5
engine compartment design,4-71 M4 (Sherman), 1-3,446
exhaustsystems,4-6=66 M48
external fue~cell, 4-69 fire dah 4-2,4-5
fire-resistant polymers, 4-61 mentioned, 4-9,4-54, 4-56,6-1
from aircmft techniques, 7-76 M60
from animal tests, 5-17 cost analysis for AFDSE, 1-8-1-9
from ASTB program, 7-78 detection, 6-31
from Russian tanks, 7-78 fire da% 4-2
fuel cell, 4-2U23, 4-26-4-27 fii-extinguishing system, 7-58
*1 lines, 4-23-4-25 fuel storage, 4-17
tilel mixtures, 425 Magazine design. See Ammunition magazine design.
full-time protection, 7-78 Magnesium, 2-24
~ high-explosive stowage, 4-56,7-56 Magnesium sulfate heptahydrate, 7-23 .-.
hydraulic lines, 4-37 Manual VdVCS, 7-35
intumescent coating, 4-69470 Mark I, fuel storage, 1-3,4-26 “
main weapon ammunition stowage, 4-54-4-56 Marks m III, fuel storage, 1-3 .-

0 ,:#$
photographs, value of, 8-28
Southeast Asia experience, 5-18-5-19
smoke generator, 4-8,4-29
w heaters, 4-65-4-66
Marlr N, fuel storage, 1-3,4-26
Mark VIII, fuel cell, 4-18
Material and configuration, vulnerability reduction, 743
Materials, noncombustible, 4-61
testing, 8-19,8-29-8-32 Mathematical model, 8-32-8-33
user fiendly equipment, 4-70 Merkava
water, 4-65,4-71 fire-extinguishing systerrL 7-69-7-70
wire insulation, 440 fuel storage, 14
Light effects, 5-3 Metals, 2-24-2-25
Light gun or reconnaissance. vehicles, 3-23, 4-9, 4-71, Mines, 1-5,4-19
5-18,7-64-7-65,7-68 MisL water, 7-27—7-31, 8-30
Light water, 7-27-7-31,8-31 Mobility fuels, 2-3-2-8, 2-21—2-22, 3-1—3-10
Linear fire extinguishers,.7-35-7-36, 7-75 combustion resistance, 3-%3-10
Liquid ptWXUR,8-6-8-12 fire-resistant fuel, 3-9-3-10
Lithium,2-24 hazards, 4-25
Litter installation, 4-64 Modeling, 8-32-8-38
LOcaked overtemperature, 5-8-5-9 ,. Models, 8-32-8-33,8-35-8-37
Lubricants, 2-22-2-24,3-18-3-20 role of, 8-1-8-3
Lubricant M3L-L-2104, 3-18 MOGAS, 3-1,3-6
Lubricant IvIIL-L-2105, 3-18 Molotov cocktail, 1-5
Lubricant MIL-L-7808, 3-18,3-20 Monnex, 7-39
Lubricant MIL-F-12070, 3-21—3-22 Monoamrnoniurn phosphate, 7-31
Lubricant MIL-B-46176, 3-14 Munitions, 3-22—3-28
Lung damage, ~32—5-33, 5-365-38
LYTT 5A] N
- fire-extinguishing system, 4-67468,6-27428, 7-67 NATO diesel, 3-7
,,,,,, fuel storage, 4-18 ‘Nitrogen, 7-9--7-10
,! !,: Noble gases, 7-10
0 mentioned, 5-13-5-14
Noncombustible materials, 4-61

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MIL-HDBK-684
Noxious .substances, injury by, 5-42-5-49. Reticulated foam, 7-43 .. .. .
Noxious particle hazards, 4-59,4-69-61 RPQmO-A threats; 1-5
Russian diesel, 3-7—3-8
0
0ils,2-22—2-24,3-18—3-22 s
On~vehicle equipment, 3-35 SEA BDARP, 4-1; 4-5,4-41
Optical detectors,.6-4-6- 16 Self-sealing fuel cells, aircraft, 7-74
combination, 6- 13—6-14 Sensors. See Detectors.
infrared, 6-13 Shafid-charge.threa~ 2-9—2- 12. See also Chemical energy
uliaviolet6- 10-6-13 threat.
Optical sensors location, 6-16 Ships, fire-extinguishing systems, 7-77
Oxygen, 7-6 Shock pressureand impulse, 5-25—5-32
Oxygen depletion, 5-45—5-46 Shock pressure, 5-3
Si~litude, 8-32—8-33
,P Site disability, human, 5-19
Paints, 3-35,3-40 Smoke
Paladin (M109A6), mentioned, ,4-31 detectors, 6-28~-29
PARK AC, 8-32,8-36 effect on crew, 5-49, 5-50
Passive tie-extinguishing systems, 7-36-7-44,7-50 generator, 4-8, 4-29
Patton; LTG George S., 1-2, 1-7 haz$ds, 5-9
Pencil gages, 8-’13 inhalation, 5-9, S-47—5-48
Penetration detector, 6-27,6-28 :- inhalation reduction, 5-48—5-49
Periiuorinated’carbon compounds, 7-31 Smoldering fires, 2-2
~erformance requirements, 8- 1—8-3 Solenoid valves, 7-33—7-34
Photoelectric smoke detectors, 6-29 Solid combustibles, 2-8—2- 12
Photographic equipment, 8-21—8-25 Solid propellants, 3-23—3-24
Photography, 8-21, 8-25—8-28 Solids, particulate, 5-47
Piezoelectric transducers, 8-6-8-8,, 8- 11—8-13 Sound waves, effect on crew, 5-50-5-51 “’
Plastics, 3-40,3-45 Space’ fillers, aircraft, 7-74-7-75
pneumatic power, 4-30,7-38 “. Space heaters, 4-654-66
vulnerability reduction, 4-30, 7-3*7-3 8 span
Portable fire extinguishers,- 7-44-7-47,7-58 curtain, 3-29, 3-33,4-64
Potassium bicarbonate, 7-12 focusing, 3-29,3-33
Potassium acetate, 3-21,7-24-7-25 liner, 3-29,3-33,4-64
!’
Potassium lactate, 3-21 reducing hull liner, 5-40-5-41
Powder panels, 7-38—7-40 Spark ignition engine, 4-14
‘tircraft, 7-75 SP~ M109, 4-2,4-31
Powder-filled panels, 7-38—7-39 SPH M11O. See also SPH M109.
Pressure measurements, 8-6-8-13 fuel storage, 4-184-19
Pressure time history, 8-6-8-13
Spray, water, 7-27—7-31, 8-30
Prevention, fire, 7-3G7-44, 7-47—7-49 Squib valves, 7-34-7-35
Promel, 7-73 STANJAN, 8-37
Propellants, 3-23—3-24 Stew. hazards, 5-9
gun, 4-53 Steam. See Water vapor.
liquid, 4-52 Stowage diagram, BFV M3A0, 3-35
Propellant charges, antifratricide, 4-5W-56 Surfac@nts, 7-11,7-27,8-31
Propylene glycol, 3-21,7-24 SURVWC, 4-1,4-5
Purple K, 7-39 Survivability
R desi~ for, 1-2—l-7
,,,.
Radiation, 5-5—5-6, 8- 13—8- 16 enhancement, 1-5-1-6
Radiation liner, 3-33 fwe protection techniques, 4-1
Reactive armor, 3-24 philosophy, 1-2—l-7, 4-61
Recording of rapidly occurring events, 8-20-6-26 priority, 1-7
Respiratory tract injuries, 5-9, 5-32—5-38 techniques, 1-7

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MIL-HDBK-684

0,,ri~
, Sustained fire, probability, 8-36 7krmistors, 8-14-8-15 -—_
SUSV, 6-H24 Thermocouples, 6-24--627,8-14
“i“(’ Systemic disability, human, 5-20 ‘fbermopile, 6-27
Threat functioning, 8-19-8-20
T
Threats, 1-2, 1-4-1-5, 2-9-2-12, 4-16-423, 4-42—
T-34, 4-68,5-20
443, 5-l—5-3
T-54, fire-extinguishing system, 7-70-7-71
overhead, 1-5
T-55, sensor, 6-27
Tractor, fire-extinguishing system, 7-78
T-55, fire-extinguishing system, 7-71 —
Trailer, 4-42
T-62, ammunition storage, 4-46
Transducers, 8-=- 13
T-72, ammunition storage, 7-72—7-73
TRV M88, 4-2
T-so, 4-10 Turbine, 4-1= 16
Tactical vehicle, SUSV, 6-H24
Twinned agent unit, 7-77
Tanks, 1-3, 1-4.1-8-1-9, 4-2, 4-5, 4-8, 4-17, 4-27, 4-37,
438,4-46,447, 468, 6-1, 6-15, 616, 627, 6-31, 7-2, u
7-36-7-37,7-58,7-60-7-61 ,7-68-7-73 Ullage, 7-73-7-75
Temperature measurements, 8-6, 8-13-8-16 expiosion protection, 744
Temperature time history, S-6, 8-13-8-16,8-20 filler materials, 7-43,7-73-7-75
Temporaxy threshold shiil 5-23-5-25 Underwater blast transducers, 8-8-8-11
Test events Uniform tests, 5-16-5-17
combustion, 8-20 Unsecured object hazards, 5-13,5-14,5-15
event timing, 8-19-8-21 Uranium, 2-25
extinguishant selection, 8-29-8-32 USASC, 4-1,4-2
gas concentration, 8-16-8-19 UV detectors, 6-10-6-13 ..
heat flu~ 8-4,8-15-8-16
performance, 8-21 v
preparation for ilre, 8-32 , Valves, for fire extinguishers, 7-33-7-35 ,
pressure time history, 8-6-8-13 Vehicle habitability, 5-53
recording, 8-20-8-28 Vehicle preparation requirements, 8-1-8-2
targetresponse,8-20 Vehicle tests, 5-1 1—5- 17
tempermm time histo~, 8-6,8-13-8-16,8-20 Vehicles, combaL See alro the specific vehicle, i.e., ~
threatfimctioning, 8-19-8-20 M 113, and the specific vehicle type, i.e., Armored per-
Test Vdlicks, 4-48, 4-6*7, 7-36,7-37,7-62 sonnel carriers.
Testing, CIeW training, 8-31 categories, 4-1
rde OZ 8-2-8-3 design requirements, 8-1-8-3
Tests, comparison of results to combat m $17—5- 19 use of, 1-2—l-4
Tests Video, 8-25
eardrum rupture, 5-28-5-32 Vitiated air, oxygen+kpleted, 7-8-7-9
evaluation of, 5-17 Vulnerabilities illustrated, 2-6-2-12,3-29,3-33,4-5, 4-12,
fbll-scale, 5-11—5-12 4-2-27, 4-29, 4-32433, 4-37, 4-38, 4-40-441,
human injury potential shown, 5-28-5-32 4-4-46,4-56,6-23,7-74
ofequiprnenk5-11—5- 17 Vulnerability reduction, 3-9-3-14,3-24, 3-33,4-8,4-20-
of aircrew uniform, 5-l&5-17 4-23, 4-29~1, 4-42, 4-46-447,4-51452,4-54-
of SkiIl burns, 5-7 4-56,4-62,4-63-4-66, 4-68--449,5-48-5-49, 7-36
of thermal effects, 5-8 7-39,7-40-7-43,7-73-7-76, 7-79
of vehicles,5-11—5-17 ancillary power, 4-2~1
recommendation to conduct animal tests, 5-12 exhaust system, 4-6546
using animals, 5-13-5-17 for aircrafL 7-7%7-76
Textiles, 3-3S3-36, 3-46 for ammunition magazines. See hurmnition magazines.
TFHAL, 8-37 for fuel system. See Fuel system.
‘Ihemai detectors, t$16-6-37 for mobility fuels, 3-10,3-13

0‘I%ermal
,,,,,,
Thermal effects tests, 5-8
injuri~ 545-7
,:’[$ effm (m performance 5-4G5-53
for Navy ships, 7-77
for space heaters, 4-65-4-66
for trailers, 442
fmtricide, 4-51452,4-5-55
Thermal overload, 5-19

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,.. IWL-HDBK-684
human perfo~ance~ 5-52—5,53 ‘. foaming agents, 7-27 .. ..
passive, 7-42—7-44 forms,. 7-27—7-28
with insensitive munitions, 4-52-4-53 for vulnerability reduction, 4-65
witliwater, 4-65 freeze point suppressants, 3-20-3-21,7-24-7-25
ullage, 7-44 gelled; 7-40
vapor, 7-2, 7-10
w Whke phosphorus, 5-20
Warheads, antifiatricide, 4-51452
.
Water, 3~20-3-21, 4-46, 7-23—7-31, 7-40,8-30-8-31
bulk, 7-27 ,.

., ,,

..

,,,

.,

.,’

,.,

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MIL-HDBK-6$4

SUBJECT TERM (KEY WORD) LISTING

Agents, extinguishing Extin~uisbing systems, passive
AgenTs, extinguishing, chemical intervention Extinguishing techniques, passive
Agents, extinguishing, physical-acting Fwe prevention
Fuel system, design --- _.
Arnmunitiom hazards
Detectors, combustion, optical Hydraulic system: design
Detectom, combustion, thermal Incapacitation, crew, predictions
Electrical system, 12 V dc, design ,. Materials selection, vehicle
Explosio% suppression Modeling, combustion and extinguishment
Extinguisher, handheld FOL
Extinguiskr, vehicle-mounted System integration, AFES
Extinguishing systems, active System swvivability

o
,,JI

custodians: Preparing activity:

Army— AT Army-AT
Navy— (project 12GP-0003)
&r Force-

o“!,jj
,,,
1
~,,,:!,’:

ST-1
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STANDARDIZATION DOCUMENT IMPROVEMENT

PROPOSAL

INSTRUC?IONS

1. The preparrrg activity must complete blocks 1.23, and 8. In block 1, both the document number and revision letter
shodd.be given.
2. The submitter of this form must complete blocks 4.5,6, and 7.
3. The preparing activity must provide a repty within 30 days ftom receipt of the form.
NOTE: Thii form may not be used to request copies of documents, nor request waivers, or clarification of requirements on
current contracts. Comments submitted an this form do not constitute or imply authoriz~on to wa”we any paifon of the
referenced document(s) or to amend contractual requirements.
1.DOCUMSNINUMBER . 2 DOCUMWI D~ (WbS%fDD)
1 RECOMMEND A CHANGE NllL-liD8K+84
Xmcurw?wnru
DESIGN OF COMBAT VEHICLES FOR FIRE SURVIVABIIJTY
$. NATLIKOF CHANGE(M6df&~ mnnber and hmfude pmpa$ed rmvdfe. ff pcssO@. Atfmh exlm sheds as needed.)

5. REMON FOR RECOMMENDATION

6.9@aTrER
txNAM&as%fTmivm b.orammoN
“.
.

c.AFmm3s~z.poxm u.lRm40w 5Mbda Al@@C9dB) 7. lMTEWBkmED

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A PEWMNG AC’lWITY ..
0. NAME b. lEIEPMO?JECndudo &eo Code)
(I) Cunmlllcm G3m
W Amy Tank-Automatfve and Armaments Command
810-574-5508 786-5508
c. ADDRESS(RtslWo 2@ CtXW IFYOU DO NOT RECUVEA REPLYWITHIN4S DAY?&C@4TAC’n
Deffw@oQucdifyandsiwl dar&@oo OfIice
/WvlSfA-TR-T
S2D31.eosbqfUco, Suite 14fB, f@rsti~VA ZZD41-3466
Warren, MI 48397-5KI0 T@ephoIw (703) 7s6-234D AUTOVON 289-234

---
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