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MIL-H-8775D
11 June 1976
SUPERSEDING
MIL-H-8’775C
8 January 1964

MILITARY SPECIFICATION

HYDRAULIC SYSTEM COMPONENTS, AfRCRA~ AND

MISSILES, GENERAL SPECIFICATION FOR

This speci5cation is approved for use by all Depart-

ments and Agenciee of the Department of Defemee.

1. SCOPE

1.1 Scope - This specification covers the general requirements

that are common to m=ydraulic ‘components (see 6.2), used in aeronautical
hydraulic systeme (see 6. 1).

1.2 Classification - Aircraft hydraulic systems in which com-

ponents covered by this specification are to be used shall be of the followtng
+. types, as specified:

Type I -65° to +160n F fluid temperature range

TYW II -65” bJ +275” F fluid temperature range

2. APPLICABLE DOCUMENTS

2.1 The following documents of the issue la effect on date of

invitation for bids or request fcr proposal, form a part of the apeciflcation to
the extent specified herein.

SPECIFICATIONS

Federal

QQ-C-320 Chromium Plating (Eleotrodeposited)

QQ-N-290 Nickel Plstlng (EIectrodewsited)

QQ-P-416 Plating, Cadmium (Eleotmdepoeited)

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MIL-H-8775D ●
Federal (Continued)

QQ-S-365 Silver Plating, Electrodeposited, General

Requirements for

QQ-Z-325 Zinc Coating, Electrodeposited, Require-

. menta for

Mtfitary

MIL-C-5015 Connectors, Electrfc “AN” Type

MIL-H-5440 Hydraulic Systems, Aircraft Types I and If,

Design, Installation, and Data, Require-
ments for

MIL-C-5501 Cap and Plug, Protective, Dust and Moisture

Seal

MIL-P-551O Packing, Preformed, Straight Thread Tube

Fitting BOSS

MIL-G-5514 Gland Design, Packings, Hydraulic, General .,0

Requirements for

MII.A2-5541 Chemical Conversion Coatings on Aluminum

and Aluminum Alloys

MfL-H-5606 Hydraulic Flnid, Petroleum Base, Aircraft,

Missile, and Ordnance

MIL-H-6063 Hydraulic Fluid, Petroleum Base, for

Preservation and Operation

MfL-I-6s66 Inspection, Penetrant Method of

MIL-I-6S66 Inspection Precess, Msgnetic Particle

MIL-M-7969 Motor, Alternating Current, 400-Cycle,

115/200-Volt %yetem, Aircraft, General
Specification for

MIL-M-6609 Meters, IMrect Current, 28-VoIt System,

Aircraft, General Specification for

MIL-A-6625 Anodic Coatings, for Aluminum and Aluminum

Alloys
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MIL-H-8775D

Military (Continued)

MIL-R-8791 Retainer, Packing, Hydraulic, and Pneumatic,

Tetrafluoroet} vlene Resin

MIL-S-8879 Screw Threads, Controlled Radius Root with

Increased Minor Diameter, General
Specification for

MIL-T-10727 Tin Plating, Electrodeposited or Hot-Dtpped,

for Ferrous and Nonferrous Metals

MIL-H-25475 Hydraulic Systems, Missile, Design, Inetal-

Iation Tests, and Data Requirements,
General Requirements for

MfL-P-25732 Packing, Preformed, Petroleum Hydraulic

Fluid Resistant, 275 Deg. F.

MIL-C-26074 Coating, Electrolees Nickel, Requirements for

MIL-F-27656 Filter Unit, Fluid, Pressure MXU-408/Mo

Absolute 5 Micron, Hydraulic

MIL-C-38999 Connector, Electrical, Circular, Miniature,

High Density Quick Disconnect

MIL-G-81322 Grease, Aircraft, General Purpose Wide

Temperature Range

MIL-S-81733 Sealtng and Coating Compound, Corrosion

Inhibitive

MIL-F-81836 Filter and Disposable Element, Fluid Pressure,

Hydraulic, 3 Micron Absolute

MIL-H-63282 Hydraulic Fluid, Ftre Resistant Synthetic

Hydrocarbon Base, Aircraft

MIL-P-83461 Packtngs, Preformed, Petroleum Hydraulic

Fluid Resistant, Improved Performance of
275 Degrees F., Sizes and Tolerances

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MIL-N-8775D .-+

Military (Continued)

MIL-C-83982 Compound, Sealing, Fluid Resistant

STANDARiM

.Federal

FED-sTti791 Lubricaat, Liquid Fuel and Related Products,

Methoda of Testing

Military

MIL-STD-1OO Engineering Drawing Practices

MIIAITD-129 Maridng for Shtpment and Storage

MIL-STD-130 Identification Marking of U.S. Military Preperty

MIL-STIP143 Standarde and Specification, Order of

Precedence for the Selection of

MIL-STD-454 Standard General Requirements for Electronic

Equipment

MIL-STD-461 Electromagnetic Interference characteristics,

Requirements for Equipment

MIL-STD-462 Electromagnetic Interference Characteristics,

Measurement of

MIL-STD-463 Definition and System of Units, Electro-

magnetic Interference Technology

MIL-STD-490 Specification Practices

MIL-STD-704 Electric Power, Aircraft, Characteristics

and Utilization of

MIL-STD-785 Reliability Program for Systems and Equip-

ment Development and Production

M IL-ST-81 o Environmental Teet Methods

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?vIIL-H-8775D

Military (Cootinued)

MIL-STD-889 Dissimilar Me”als

MIL-STD-961 Outline of Forms and Inetructiona for the

Preparation of Military ;standarda and
Association Documents

MS20659 Terminal, Lug, Crimp Style, Copper,

Uninsulated, Ring Tongue, Type I, Claes I

MS2 0995 Wire, Safety or Lock

MS21209 Insert, Screw Thread, Coarse and Fine,

Screw Locking, Helical Coil, Cres

MS21343 Boss Spacing-Hydraulic Design, Standard for

MS2 1344 Fitting-Installation of FIared Tube, Straight

Threaded Connectors, Design Standard for

MS27595 Retainer, Packing Backup, Continuous Ring,

Tetrsfluoroethylene

MS28772 Packing, “D” Ring, Shcck Strut

MS28774 Retainer, Packing Backup, Single Turn

Tetrafluoroethylene

MS28775 Packing, Preformed, Hydraulic, Plus 275 Deg. F.

( “O” Ring)

MS28778 Packing, Preformed, Straight Thread Tube

Fitting Bees

MS28782 Retainer, Packing, Back-Up, Teflon

MS28783 Ring, Gasket, Back-Up, Teflon

MS33514 Fitting End, Standard Dimensions for

Flareless Tube Connection and Gasket Seal

MS33515 Fitting End, Standard Dimensions for

Bulkhead Flare less Tube Connections

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MIL-H-8775D
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Military (Continued) -1
MS33540 Safety Wiring and Cotter Pinning, General
Practices for

MS33547 Pin, Spring, Functional Limitiatione of

MS33649 BOSS, ‘Finid ~onnection - Internal Straight

Thread

MS33656 Fitting End, Standard Dfmensione for Flared

Tube Connection and Gasket Seal

MS33657 Fitting End, Standard Dtmensiona for Bulk-

head Flared Tube Connections

Air Force- Navy Aeronautical

AN814 Plug and Bleeder - Screw Thread

AN6227 Packfng, “O” Ring Hydraulic

AN6230 Gasket, “O” Ring Hydraulic -+

AND] 0476 Washsr - Limitations on Usage of Lock

PUBLICATIONS

Air Force - Navy Aeronautical Bulletin

MIL-147 Specifications and Standards of Non-Government

Organizations Released for Flight Vehicle
Construction

Military Bulletin

MIL-HDBK-5 Metallic Matertals and Elements for Aerospace

Vehicle Structures

M IL-HDBK-221 Fire Protection Design Handbeok for U.S.

Navy Aircraft Powered by Turbine Engines
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MIL-H-8775D

(When requesting applicable dccuments, refer to botb title and number.

Copies of unclassified documents may be obtained from tbe Commanding
Officer, Naval Publication and Forms Center, 5801 Tabor Avenue, Philadelphia,
Pennsylvania 19120. Requests for copies of classified documents should be
addressed to tbe Naval Publications and Forms Center, via the cognfzant
Government representative. )

2.2 Other publications - Tbe following document forms a

part of this specification to the extent specified berein, unless otherwise indf-
cated, the issue in effect on tbe date for bids or request for proposal shall apply.

American National Standards Institute

ANSI B46.1 Surface Texture (Surface Roughness,

1962 Waviness and Lay)

(Copies of the above publication may be obtained from the American National
Standards Institute, 10 East 46th Street, New York, New York 1001’7. )

Society of Automotive Engineers

ARP 603 Impulse Testing of Hydraulic Hose Assemblies,

Tubing and Fittings

ARP 1383 Impulse Testing of Hydraulic Actuators, Valves,

Pressure Containers and Similar Fluid
System Components

(Copies of tbe above publication maybe obtained from the Society of

Automotive Engineers, 400 Commonwealth Drive, Warrendale, Pennsylvania 15096. )

National Aerospace Standards Association, Inc,

NAS 1638 Cleanliness Requirements for Psrts Used in

Hydraulic Systems

(Application for copies should be addressed to the National Aerospace

Standards Association, Inc. , 1321 Fourteenth St. , N. W., Washimton, DC 20005. )

3. REQUIREMENTS

3.1 Contractor’s
— — general component specification - fnthoae

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MIL-H-8775D ●
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cases where, bymutual agreement between the contractor and the procuring
actiw”.ty, it ie determined that thta specification cannot be readtly applied to a
particular hydraulic system, or the number of deviations necessary would make
this specification impracticable, the contractor shall prepare a general com-
ponent spectftcaticn similar to thie specification, in conformance to MIL-STD-490
and MIL-STD- 961 and submit it to the procuring activity for approval. This
document shall specify the perfomnance, design, and testing requirements for
all the components in the hydraulic system and also shalf be the controlling
document for component not otherwise covered by an applicable detail com-
ponmt specification.

3.2 Matertals - Materials used in the manufacture of hydraulic

components shall be of high quality, suitable for the purpose, and shall con-
form to applicable Government specifications. Materials conforming to contrac-
tor’s specifications may be used, provfded it can be clearly demonstrated that
they are at least equivalent to Government specifications with respect to cperating
characteristics and that a savings in weight or cost can be accomplished. Con-
tractor’s specifications must be satisfactory to the Government and contain
provisions for adequate tests. The use of contractor’s specifications will
not constitute waiver of Government inspection.
“-!
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3.2.1 M~ - All metals shall be compatible with tbe fluid
and intended temperature, functional, service, and storage condttione to which
the components will be exposed. Metals shall be limited to those specified by
the detail specification. The metals shall possess adequate corrosion-resistant
characteristics or shall be euitably protected by the use of coatings equivalent
to those 1isted in Table I to resist corrosion which may reeult from such con-
dttione as dtesimilar metal combinations, moisture, salt spray, and bigb
temperature deterioration, as applicable. Where not indicated, clase or type
is at the option of tbe manufacturer, subject to approval by the procuring
activity. Dtseimilar metals are defined in MIL-STD-889. Unless otherwise
spectfie’d herein. physical properties of all metals shall meet tbe minimum
requirements of MIL-HDBK-5.

3.2.1.1 Copper and Aluminum alloys - All copper alloys except

for bearing surfaces shall be suttably protected with a coating eelected from
Table I, except that cadmium and zinc plating shall not be uskd in application
subject to abrasion. Other metallic coatinge, which shall have been demon-
strated to be satisfactory to tbe Government, such as electrodeposited 85
percent tin and 15 percent cadmium alloy, may be used. All aluminum alloys
shall be anodtzed in accordance with MIL-A-8 625, type II coating, except that
in the absence of abrasive conditions the anodize may be type I coating, where
applicable, or may be a chemical film in accordance with MIL-C -554I.
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MIL-H-8775D

TABLE I. METAL COATINGS

Coating Specification

Cadmium plating QQ-P-416, type II, class 2

Zinc plating QQ-Z-325, type II, class 2
Chromium plating QQ-C-320
Nickel plating QQ-N-290
Silver plating QQ-S-365
Tin plating MIL-T-10727, type I
Electroless nickel MIL-C-26074

3.2.1.2 Type I components - Except for internal surfaces in

constant contact with hydraulic fluid, ferrous alloys shall have a chromium
content of not less than 12 percent, or shall be suitably pr~:ected against
corrosion as specified in 3.2.1, 3.2.1.1, and Table I. In additiOn, cadmium
and zinc plating shall not be used for internal parts or on internal surfacea
in contact with hydraulic fluid or exposed to its vapors. O-ring grooves for
external seals shall not be considered as internal surfaces in constant contact
with hydraulic fluid. Use of magnesium shall be subject to the approval of
the procuring activity.

3.2.1.3 Type II components - Ferrous alloys shall have a chrom-

ium content of not less than 12 percent, or shall be internally and externally
protected against corrosion as specified in 3. z. 1, 3.2.1.1, and Table I. In
addition, cadmium and zinc plating shall not be used for internal parts or or
interml surfaces in contact with hydraulic fluid or exposed to its vapors.
Magnesium shsll not he used for type H components.

3.2.1.4 Residual magnetism - Parts made of material that is

capable of retaining residual magnetism, but are not intended to function as
magnets, shall be demagnetized sufficiently to prevent system or component
malfunction, including malfunction due to accumulation of magnetic con-
taminants. Where a component or system is vulnerable to malfunction due to
residual magnetism, the component detail specification shall specify the maxi-
mum allowable flux density.

3.2.1.5 Magnetq - Permanent magnets and electromagnets shall be

shielded where required to prevent system or component malfunction. ‘~>hede-
taiI specification shall specify the maximum allowable flux density outside the
shield.

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MIL-H-8775D ●
3.2.2 Plastic parts - The use of plastic parts shall be subject to
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the approval of the procuring activity for the specific application involved.

3.2.3 Selection of materials, parts and prooesses - Specifica-

tions and standards for all materials, parts, and Government certification and
approval of processes and equipment, which are not specifically designated
herein and which are necessary for the execution of this specification, ‘shall be
selected in accordance with MIL-STD-143 and MIL 147, except as provided
in the following paragraph.
3.2.3.1 Standard parts - Standard parts ( MS, AN or Specification
sheet) shall be used wherever they are suitable for the purpose, and shall be
identified on the drawing by their ( MS, AN or Specification sheet) part numbers.
Commercial utility parts, such as screws, bolts, nuts, and cotter pins may be
used, provided they possess suitable properties and are replaceable by the
standard parts (MS, AN or Specification sheet) without alteration, and provided
the corresponding standard part numbers are referenced in the parts Iis t and,
if practicable, on the contractor!s drawings. In the event there is no suitable
corresponding standard part in effect on date of invitation for bids, commercial
parts may be used provided they conform to all requirements of this specifi-
cation and the detail specification.
-+
3.3 Design and construction -

3.3.1 GeneraI - The configuration, dimensions, and other details

of design of standard components shall conform to the applicable MS, AN or
Specification sheet standards. Non-standard components shall conform to the
applicable”man~acturer’s or PrOcuring activity drawing as governed by
MIL-H-5440 or MIL-H-25475.
3.3.2 Temperature range - Components shall be desfgned and
ao constructed as to insure satisfactory operation throughout the temperature
range specified in tbe detail specification.

3.3.3 Threads - Straight threads shall conform to MIL-S-8879,

Untfled Fine Thread Series, classes UNJF-3A and UNJF-3B. Other type threads
ahsll be subject to approval of the procuring activity. Pipe threads shall not
be used except for permanently installed plugs.

3.3.4 w - Components shall be designed to operate with

MIL-H-5606 hydraulic fluid. When specified by the detail specification or
apprOved by the Procuring activity a fire resistant fluid such as MfL-H-s3z82
hydraulic fluid shall be used.

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MIL-H-8775D

3.3. s Orifices - Orifices larger than O.012 inch but smaller than
(). 070 inch in diameter shall be protected by adjaceot strainer elements having
screen opeoilig~ u. u08 to 0. Olz inch in diameter. Orifices smaller than the above
range may be protected by adj scent elemente havtng openings smaller than the
orifices with the approval of the procuring activity. Orifices and strainer
elements shall be strong enough to absorb system desigmflow and pressure up
to and including blocked flow without rupture.

3.3.6 Packing -

3.3.6.1 General - Component shall be so designed that, in assem-

bly of parts, sufficient clearance exists to permit assembly of the components
without damage to O-riugs or backup rings where they pass threaded parts or
sharp corners. MIL-G-5514 and MS21344 shall be used for type I system
packing installation and as a gujde for type ff system packfng installation.

3.3.6.2 Type I system components - All packtngs and gaskets .

shall be in accordance with MS28778, AN6227, AN6230, MS28772, or MS28775.
Backup rings shall he in accordance with MS28774, MS28782, MS28783, or
MS27595. Packing shall conform to MIL-P-25732 (excluding besa applications).
Packings used in bosses shall conform to MIL-P-551O.

3.3.6.3 Type H system components - Packings conforming to

M IL-P-25732 shall be used within the perfommmce constraints reflected by
qualification requirements and tests of MfL-P-25732. Non-Standard packing
or MI L- P-834 61 packing may be used subject to approval of procuring activity.
Tbe major performance constraints of MIL-P-25732 are summarized below.

3.3.6.3.1 Maximum fluid temperature of 225° F - If the msximum

fluid temperature does not exceed 225° F, the standard ‘ieal is suitable for the
normal life reflected by Endurance Test “B” of MIL-P-25732.

3.3.6.3.2 Maximum fkdd temperature between 225 “F and 275° F - ff

maximum fluid temperature is between 225° F and 275” F, the life expectancy of
the standard seal shall be reduced proportionally from tbe normal life reflected
by Endurance Test “B” of MIL-P-25732 to the reduced lile reflected by Endurance
Test “A” of MIL-P-25732. (The total accumulated time of exposure to 275° F
during qualification tests is approximately 80 hours. ) Tbe reduced life ex- ,
pectancy shall be clearly defined in all appropriate publications. Packings
used in besses shall be subject to the approval of tbe procuring activity.

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MIL-H-877!1D
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3.3.6.4 Back-up rings - Back-up rings shall confomn to ‘-l
MIL-R-8791.

3.3.7 ?3afet ying - All threaded parts shall be securely locked or

ssfetied by safety wiring, self-be king nuts, or other approved methods. Safety
wire shall be applied in accordance with. MS33540 and shall conform to
MS20995; Star washers and jam nuts shall not be used ae locking devices.
Use of lock washers shall be governed by limitations set for in AND10476.

3.3.7.1 Safetying internal parts of fluid chambers - Permanently

deformed safetying devices, such as safety wire or cotter pins, that are subject
to breski~ off shall not be used internally in fluid chambers.

3.3.7.2 Threaded Inserts - All threaded holes in non ferrous

parts to be used for mountiz.g screws or bolts shall incorporate self-locking
inserts cmforming to MS21209.

3.3.8 Retainer ring s - Retainer rings or snap rings shall not be

used unless specifically authorized by tbe procurfng activity for each applica-
tion. Where such applications are authorized, the following requirements are
applicable.

3.3.8 ..1 Displacement - Displacement of the ring or fragmentation

thereof, and associated hardware (e.g. washers, lockwire, etc. ) shall not
cause, or contribute to, loss of fluid from the cnmponent or system, or cause
malfunction of any component in the aircraft.

3.3.8.2 Load limitation - Hydraulic, structural, mechanical, or

any other form of loads, or combinations tb ereof, including vibration, shock
loads, expansion or contraction due to thermal changes, etc. shall not be
exerted on the ring that may cause axial displacement and/or failure of the ring.

3.3.8.3 Installatim clearances and tolerances - Retainer rings

or snap rings shall not be used where buildup of clearances and manufacturing
tolerances will allow destructive end play in the assembly that may cause,
or contribute to, failure of packtigs or gaskets, brine lling, or fatigue failure
of parts.

3.3.8.4 Installation and removal - The retainer rings or snap

rings shall be capable of being installed and removed with standard pin-type
pliers or other standard tools developed for use with the rings.
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MIL-H-8775D

e 3.3.9 Spring pins - The use of sprtng pins is undesirable and

they shall not be used in any applications that conflict with the intent of
MS33547, unless specifically approved by the procuring activity.

3.3.10 Reverse Installation - AR components shall be designed

such that reverse or incorrect installation in the aircraft or sub-assembly
cannot be made. fnternal parts which are subject to malfunction or failure
due to reversed or rotated assembly shall be designed to render improper
assembly impossible.

3.3.11 Structural strength - The components shall have sufficient

strength to withstand all loads or combinations of loads resulting from hydraulic
press ure, vibration, temperature variations, actuation or operations, and
torque loads for connection of tube fittings in accordance with MS21344.
Standard type 11components shall be designed to withstand 275” F proof
pressure and burst pressure tests, 4.5.3.1 and 4.5.3.2, respectively, after
lnss of strength of the material caused by aging at 275” F for 1,000 hours.
Nonstandard type II components shall be designed to withstand 275” F proof
pressure and burst pressure tests aa specified in 4.5.3.1 and 4.5.3.2,
respectively, after loss of strength cf the material caused by aging at 275” F
for a time period as designated in tbe detail specification.
*
3.3.12 Ruggedness - Where a manually operate? control lever,
etc. is intergral in a component, tbe lever, rr,echsmism, and stops shall bc
capable of withstanding a limit torque of 75R pound-inches for radii greater
than O. 8 inches. In the case of components which incorporate stops but
do not have an integral control means, the stops shall be capable of with-
standing a limit torque of 1, 800 pound-inches.

3.3.13 Rated flow capacity - The rated flow capacity shall be

as specified in the applicable detail drawing or specification.

3.3.14 Preesure drop at rated flow - The component shall he

so designed as to offer the minimum restriction to flow consistent with the
othc r requirements of this specification. Pressure drop at rated flow shall
not exceed the values specified in the applicable detail drawing or
specification.

3.8.15 B- - The configuration of components shall provide

scavenging of entrapped air and foreign matter such as water or excess
lubricant. Auxiliary bleed ports shall be provided when necessary.

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M1l,-H -87751)

3.3.16 Function -arljustm eut screws - Function-adjustment screws, -1

if used, sha!l be so designed and constructed as to maintain adjusbner.: under
all tbe required conditions of vibration, shock, temperature, and operation.
Friction-type lecking devices shall be kept to a minimum and shall be subject
to the approval of the procuring activity. If friction type is used, the adjustment
screws shall maintain their setting after adjusting through the full range 15 tbnes,
or as specified in the detail specification, and then vibration tested. It shall be
possible to adjust and leek the adjustable screws with a standard wrench or
screwdriver. Where practicable, “it shall be possible to adjust under full system
pressure with negligible loss of fluid. The adjustment screws shall be sealed,
where-practicable. If the component is subject to multiple settings, the seal
shall be marked with the setting. The means of adjustment shall either be
internal or protected from tampering by a cover or similar device.

3.3.17 Fluid comections - Permanent fitting sh al 1 be used

S1b]eCt to limitations specified in MIL-H-5440.

3.3.17.1 Bosses - All internally threaded bosses for connecti~

fittings and AN814 plugs shall conform to MS33649. Spacing of ports for
connecting fittings shall conform to MS21343. Bosses shall be made deep
enough or shal! kcorporate fitting stops to prevent dmnage to internal
mechanism or restriction of fluid flow when universal fittings are screwed
into the bosses to excessive depths.

3.3. 17.2 External tube connections - External male threaaed tube

connections shall conform to MS33656 and MS33657 or MS33514 and MS33515.
Male threaded flared fitting ends on 3,000 pounds per square inch (psi) com -
ponents shall be steel in sizes below l/2-inch tube sizes. These may be
aluminum alloy or steel for the tube sizes 1/2 inch and above. Caution should
be used in the use of aluminum alloy where repeated assembly could damage
the fitting which is an integral part of the component snd thus render it
unserviceable.

3.3.17.3 Fluid connection marking - All ports for tile tube connec -
tions shall be clearly and permanently marked to indicate the connections to
be made using nomenclature in accordance with MII.-STD-13O. Where appli-
cable, the directions of flow shall be indicated. The use of abbreviations
should be avoided, but if used shall be the general industry accepted abbre-
viations as applicable for the m srking. Use of a single letter for marking
such as “P” for pressure and “C !, for cYlinder is not acceptable. Decal-
com anias shall not be considered as a permanent markinE.
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MIL-H-8775D

3.3.1s * - All plugs, except permanently installed plugs

that will not have to be removed during the life of the component shall conform
to AN814 for types I and II systems. Where considered more advantageous
a plug with a seal conforming to MS28775 may be used.

3.3.19 Alignment - All plungers, poppets, balls, pistons, etc.

shall be accurately guided to prevent misalignment or chattering on their
seats.

3.3.20 Elect ric ally operated components -

3.3.20,1 Voltage range - Electrically operated components shall

be designed to operate in aircraft and missile electrical systems having
characteristics as specified in MIL-STD-704. The components shall he
designed to operate under simultaneous extremes of temperature, fluid
pressure, and voltage for their classes as specified in Table R. The effect of
factors such as: over and undervoltage, distortion (ripple), surge and
emergency mode eperation shall be considered fn determining the most
detrimental voltage as defined in MIL-STD-704.

Table R. Temperature, Pressure, and Voltage

Voltage delivered by aircraft

Class Temperature System pressure or missile electrical system
(See MIL-STD-704)

A, B,C, D (rein) (4-hour soak) (max.), ,min) Lowest voltage delivered

A, B,C, D Room (70” F to 90” F) (max.), (rein) Lowest voltage delivered
A, B,C, D Room (70” F to 90” F) 1.5 times Lower limit of steady state range
A (max) plus temp. rise (max.), (inin) Lowest voltage delivered
R (max) plus temp. rise (max.), (rein) Lower limit of steady state ra~e
c (mex) plus temp. rise (max.), (rein) Upper limit of steady state range
D (ins-x) (max.), (rein) Lower limit of steady state range
—

3.3.20 .1.1 Tbe ciass of the component shall be A, B, C, or D and as

specified in the detail specification.

3.3.20 .1.2 Class A and B components

.— - class .4 and B components are
normally ener~ized continuous-duty type. These components shall be capable Of
operation at the voltage specified in Table II after being energized at the uPPer
limits of the steady state voltage range specified in MI L-STD-704, while

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MI L-H-8775D

exposed to the maximum ambient temperature and al titm-fe conditions specified

in the detail specification until coil temperature stabilization is reached. If any
form of temperature control of the coile is to be used In the actual system
it shali be employed fn the test setup.

3.3.20.1.3 Clase C components - Clase C components are normally

ene rgiz,ed continuous ~=ty type. These components shall be capable of recycling
at the voltage specified in Table II and at the temperature, and altitude specified
in the detail specification, after being energized at the same voltage while ex-
posed to the maximum ambient temperature and altitude conditions specified in
the detail specific ation until coil temperature stabilization is reached. If any
form of temperature control of the coil is to be used in tbe actual eystem, it
shall be employed in the test eetup.

3.3.20. 1.4 Class D components - Class D components are normally

deenergized intermittent-dut y type, and shall be tested at the voltage specified
in ‘l’able 11 while at the maximum temperature and altitude conditions specified
in the detail specification after temperature stabilization is reached while in the
decnergized condition. The ttme of energization and time between cycles ehall
be as specified in the detail specification.

3.3.20.2 Solenoid operated components - The solenoids shall be of

compact design and of sufficiently rugged construction to withstand tbe mechanical
‘-s
shocks and stresses incident to their use in aircraft and performance requirements
specified in 3.3.20.2.7. Solenoids shall be designed for continuous or intermittent
duty and shall be provided with single-coil windings. Solenoids shall be totally en-
closed, in order to prevent moisture from coming in contact with the electrical
windings. The coil shall be firmIy fixed in the frame to prevent ultimate failure
of leads caused by vibration. Potting compounds used in the electrical com-
ponents shall be subject to approval by the procuring agency. Solenoids shall
operate within the time specified in the detail specification.

3.3.20.2.1 Coils - Coils shall be evenly wound end insulated to meet

the performance requ=e%ents specified (see 3.3.20.2. 7). Coils shall be com-
pletely insulated from the frame or other component parts. Coils shall be
suitably taped, impregnated, and secured to the frame as required to prevent
damage under humidity, salt fog, vibration, and other test conditions specified
for tbe component (see section 4).

3.3.20.2.2 Termfnals - Solenoid coils shall be terminated with an

electrical comector conforming to M IL-C-5015 or MIL-C-38999. Terminals
shall he constructed of corrosion-resistant material or suitably plated material
and equipped with waeher, leckwsaher and screw or nut for use with cable
terminals conforming to MS20659.
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MIL-H-8775D

e 3.3.20.2.3 Dielectric strength - All solenoids shall exhibit a leakage

current of less than one miIliam~ere when eubiected to a 60 Hertz alternatimz
teet voltage between termimds and case for one minute at the following root
mean square amplitudes:
a. 1500 volts at room temperature and pressure
b. 1000 volts at maximum operating temperature and
altitude.
3.3.20 .2.4 Temperature rise - When tested at maximum temperature
and altitude conditions, the temperature attained at equilibrium calculated by
the rise of res istence method shall not exceed the continuous rating of the
electrical insulation or other materials ueed in construction of tbe solenoids
(see 4.5.7).

3.3.20 .2.5 Endurance - Tbe eolenoid valve shall withstand the

endurance test specified in the detail specification for the component (see
4.5.8 and 4.6.1).

.3.3.20.2.6 Attitude - The solenoid valve shall conform to all require-

ments of this specification while mounted in any position.

3.3.20.2.7 Performance - The solenoid shaI1 be capable of operating

the component under the following environmental conditions or natural
combinations the reo f:
(a) Almcspheric pressure range: Equivalent to the
range from sea level to the maximum altitude specified in the detail
specific ation.
(b) Temperature limits: Same as specified for fluid eml
embient limits for the cemponent. Test as specified in 4.5.6.5.
(c) Hum idit y: Conditions encountered when tested as
specified in 4.5.10.
(d) Sand and dust: Conditions encountered when tested
as specified in 4.5.12.
(e)
,. Vibration. shock and acceleration: Conditions
encountered when tested ae specified in 4.5.9.
(f) Fungue resistance: (See 4.5. 11. )
(g) Salt feg: (See 4.5.13. )

3.3.20 .2.7.1 Drop out voltage - Solenoid operated components shall

be de-energized below the drop out voltage. The drop out voltage shall be
greater than 10~ of the nominal operating voltage and less than the minimum
activation voltage specified in the detail specification.

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MIL-H-87751)

3.3.20.3 Electric motor operated components - The characteristics

of electric motors for operating hydraulic components shall conform generally
to M IL-M-8609 for dc operated units, MIL- M-7969 for ac operated units, and
to the det:~il specification, including the oilproof and explosion proof require-
ments.

3.3, 20.4 Clutches or brakes - On assemblies u.sing clutches or

, brakes to limit overtravel, tbe design shall be such as to prevent overtravel
sufficient to cause malfunctioning of the component, even with oil on the clutch
or brake surfaces. Posit ive mechanical stops shall be incorporated to insure
accurate positioning.

3.3.20.5 Explosion proof - Detail specifications for electrically

eperated components that have a potential source of ignition shall specify tbe
applicable eXplOSiOII proof teSt in accordance with MIL-STD-81O. Surface
temperature of electrically operated c mnponents shall be below auto ignition
temperat~e of tbe environment as defined in MIL-HDBK-221.

3.3.20.6 Elect rom agnetic interference - Detail spec ificatione for

elec~,ric afl y operated components that cause e] ectrom agnetic interference shall
specify interference testing in accordance with MIL-STD-461, MIL-STD-462
and MIL-STD-463.

3.3.21 Actuation above system pressure - Components shall be

so designed as to be capable of actuation or deactuation under pressure equal
to thermal relief or system relief valve maximum setting of the circuit in which
they are fnstalled, without encountering any seizing, excessive force input or
greater electrical voltage than the specified maximum turn-on voltage nor greater
than maximum rated current. The turn-on voltage shall not exceed 80 percent of
the nominal voltage. Tbe maximum current rating (continuous and intermittent)
based on the worst case environment and tbe maximum turn-on voltage, shaIl be
provided in the component specification.

3.3.22 Reliability - Each compenent shall be designed and con-

structed to meet a specified quantitative reliability requirement in terms of mean
time between failures ( MTBF) or its equivalent. The detail specification for criti-
cal ( see MIL-STD-785) components shall include specific test plans to demonstrate
that the necessary reliability requirement, including confidence factors, is satisfied.

3.3.23 Cleanliness - Internal cleanliness of hydraulic components

shall be equal to or better than class 8, table I of NA.W638 (see 4.5.20).

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MIL-H-8775D

*L 3.4 ~nterchangeabilit y - All parts having the same part

number shall be directiy and completely interchangeable with each other with
respect to installation and performance. Changes in manufacturer’s or pro-
curing activity part numbers shall be governed by the drawing number require-
ments ofMIL-STD-100. Subassembly ies composed of selected mating compon-
ents must be interchangeable as assembled units, and shall be so indtcated on
the applicable drawings. The individual components of such assembled untts
need not be interchangeable.

3.5 Lubricants - The hydraulic fluid selected tn paragraph

3.3.4 shall ix? used to lubricate seals during installation and assembly of
hydraulic components. A light coating of grease conforming to MIL-G-81322
or hydrauIic fluid conforming to WIL-H-6083 may also be used (for
MIL-H-5606 systems). If other lubrication ia necessary, the means of
lubrication and the Iubricamt used must be approved by tbe procuring activity.
Lubrication shall be so accomplished that no disassembly for relubrication
is necessary during endurance testing or normal service life. Copious use
of MIL-G-81322 grease shall he avoided.

3.6 = - Weight shall be maintained as low ae POSSible,

consistent with the requirements of this specification. The weight of the”
assembled component shall be specified in the manufacturer’s assembly
drawinge.

3.7 Finish -

3.7.1 Surface roughness - Surface rougbnesa finishes, where

required, shall ‘be established, and shall be specified on the manufacturer’s
assembly drawings as specified in ANSI B46. 1 - 1962. Tbe determination
of surface fiuishes shall be made with a profilometer, comparator brush
analyzer, or other suitable comparison equipment with an accuracy of ●15
percent at the level being measured. If surface defects are unacceptable, it
shall be specifically designated that all imperfections will be within stated
iimits or that prescribed special inspection procedures will be followed. At
least where a surface of 16 mic roincb roughness height rating (RHR) or finer
is designated, the essential process description for its generation shall be
in addition to surface measurements that constitute part of the requirements
for compliance. When necessary, waviness and lay shall be specified.

3.7.2 Coatinge - Upon request of the procuring activity, tbe

contractor shall supply test data or perfomm specific tests wbicb are con-
sidered neceseary to determine that the materials and plated cnatinga
employed in the component are suitable for the intended service.

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TvIIL-H-8775D

3.8 Physical defect inspection - All magnetizable highly

stressed parts shall be subjected to magnetic inspection in accordance with
MIL-I-G868. Aluminim or aluminum-alloy parts which have been treated
with MIL-C-5541 material shall be inspected after treatment by a process
conforming to MIL-I-6866. Where such inspection is necessary, it shall be
called for on the manufacturer’s drawings, Cracks or other injurious defects
disclosed by the inspection shall be cause for rejection. Where MfL-C-5541
material is used for touchup on parts which have been anodized, the above
inspection process will not be required.

3.9 Special tools - The design shall be such that special or

unusual tools will not be required for normal maintenance and inspection of
the component.

3.10 Identification of product - The components shall be

marked for identification in accordance with MI L-STD-130.

3.10.1 Nameplate - Each component shall be identified by

means of a durable nameplate conforming to MI L-STD-130. The nameplate
shall he securely attached to each component by use of screws, rivets,
welding, or other approved method. A faying surface sealant conforming
to M IL-C -83982 or MIL-S-81733 shall be used under mechanically fastened
nameplates to prevent corrosion. Nameplates which are attached by use of
adhesives will require prior approval of the procuring activity. Nameplates
shall not be impression stamped after installation.

3.11 Workmanship - Workmanship shall be high grade through-

out to insure proper operation and service life.

4. QUALITY ASSURANCE PROVISIONS

4.1 Responsibility for inspection - Unless otherwise specified

in the contract or purchase order, the supplier is responsible for the perfor-
m ante of al 1 inspection requirements as specified herein. Except as otherwise
specified in the contract or order, the supplier may use his own or any other
facilities suitable for the performance of the inspection requirements specified
herein, unless disapproved by the Government. The Government reserves the
right to perform any of the inspections set forth in the specification where such
inspections are deemed necessary to assure supplies and services conform to
prescribed requirements.

4,2 Classification of tests - The classification of tests,

qualification, first article or quality conformance, shall be as specified in
the detail specification. Test metheds are described in 4.5, 4.6 and 4.7.
-I*
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4.3 Qualification or first article test conditions - The follow-

ing test conditions apply to qualification or first article testing, unless
otherwise reedified by, or added to, in the detail specification.

4.3.1 Adverse toleramce conditions: - Tbe component shall be

capable of functioning when assembled with adverse tolerance parts without any
degradation iu component performance or life. The manufacturer shall verify
cmnpliance with this requirement by m atbematical analysis.

4.3.2 Test fluid - The fluid selected in paragraph 3.3.4 shall be

used as a test fluid. For quality conformance testing MIL-H-6083 fluid may b’?
used in lieu of MIL-H-5606 fluid.

4.3.3 Temperature conditions - Unless otherwise spec~led, tbe

ambient and outlet fluid temperatures shall be within the range indicated in
each individual test. For the components with appreciable heat generating
characteristics such as relief valve, solenoid-operated units, etc. , the outlet
fluid temperature shall be as specified, and the inlet fluid and ambient tern-
perature may be decreased to compensate for this heat generation. However,
in no case shall the inlet fluid temperature or ambient temperature be
decreased by more than 25” F. For zero flow condition tests, the ambient
temperature shall be as specified. The ambient inlet and outlet fluid temper -
at ure shall be stated in the test report. Fluid tern perat ure shall be meaaured
as near as practicable to tbe cnmponent ports. During all snaking periods,
the system shall be bled of air and shall be maintained full of fluid. Unless
otherwise specified, the following tolerances shall be applied respectively
to the following basic temperatures referred to throughout the tests specified
in Section 4:

4.3.4 Filtration - For qualification testing, the test fluid shall

be continuously filtered through a filter element with a micron rating equivalent to
tbe micron rating of the filter element used in the aircraft or missile system.

4.3.5 Qualification of similar units - In the case of a series of

devices which are intended to serve the same general function in a hydraulic
system, qualification of one device of the series may, at the discretion of the
activity responsible for qualification, bs applied to auy nther devices of the
series if all the internal working parts are identical in every detail with the
corresponding internal working parts of the qualified device, and provided it
meets the proof, burst pressure, and such operational requirements as may
be designated by the activity responsible for qualification. For example,
qualification of this type would apply to all devices which differ from pre-
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MIL-H-8775Q
‘a
-3
viously qualified devices only insofar as port size, port location, external
body dimensions, and external body configuration are concerned. This
qualification of similar devices is not automatic upon qualification of one
device in a series; it is the discretion of the activity responsible for
qualification.

4.3.6 Applicable tests - All tests described herein shall be

conducted on each test component in the order specified fn the detail specifica-
tion.

4.4 Quality conformance tests - Unless otherwise specified

fn the detai 1 specification, the quality conform ante tests for a type I or a
type II component shall consist of:

(a) Examination of product (4.5.1)

(b) Proof pressure (4.5.3.1)

(c) Leakage tests (4.5.4)

(d) Pressure drop (4.5.5)

4.4.1 Quality conformance test conditions - Unless otherwise

specified in the detail specification, the following test conditions shall apply.

4.4.1.1 Quality conformance test temperature - Unless otherwise

epecified, fluid and ambient temperatures shall be between 70” and 120° F.

4.4.1.2 Quality conformance test filtration - Unless otherwise

specified, the test fluid shall be continuously filtered through filters
equivalent to MIL-F-27656 (USAF) or MIL-F-81836 (AS) for Navy applications.

4.5 Test methods - Type I components -

4.5.1 Examination of product - Each component shall be carefully

examined to determine conformance to the requirement of this specification for
design, weight, workmanship, marking, conformance to applicable AN or MS
standard, government and manufacturers drawings , specifications and standards
for any visible defects.

4.5.2 Jmmersion -

4, fi,2.1 Nonmetallic parte - Components containing nonmetallic

parts other than plastic parts or MS or AN standard seals in glands conforming
to MIL-G-5514 shall be immersed in hydraulic fluid for a period of 7 days at
a temperature of 158” + 2°F prior to conducting the qualification tests specii’ied
herein or in the detail specification. All internal psrts shall be in contact wilh
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MIL-H-8775D

the fluid during this period. If this test is necessary as a result of the use of
nonstandard packing installations, or if the packings pass over holes, ports,
step diameters, threads, etc. , and if the inside diameter, outside diame~ef,
or sides of the seal are unrestrained during any part of their normal opera-
tion, the packing used in the test samples shall be fabricated of the approved
AN packing compound listed tn QPL-5516 having the highest swell, and the
fluid shall be tbe hydraulic fluid listed M QPL-5606 with 26-28% swell Of
etandard e ynthetic rubber. (The Government wilI designate the applicable
high-s well packing compound and fluid upon request to the activity responsible
for qualification. ) After the above immersion, the equipment shall remain
in the high-swell ffuid at normal room temperature until ready for test. It
shall not be expnsed to air for any appreciable length of time during the tests.

4.5.3 Pressure tests -

4.5.3.1 Proof pressure - A proof pressure, as specified in

M IL-H-5440, MIL-H-25475 or the detail specification, shall be applied at the
temperature specified in the detail specification for at least two successive
times and held 2 minutes for each pressure application. The rate of pressure
rise ehall not exceed 25,000 psi per minute. The equipment shall be operated
in its normal function between applications of the test pressure. There shall
be no evidence of external leakage, other than a slight wetting at seals in-
sufficient to form a drop, excessive distortinn, or permanent set. Compon-
ents which require varying test pressures in different elements may have
these pressures applied either separately or simultaneously as specified in
the [ietail specification. Components that are s uhject to pressure in tbe
reverse direction such as check valves, shut off valvee or accumulators shall
bc pressurized in both directinne, either separately or simultaneously as
specified in the detail specification.

4.5.3.2 Burst pressure - A burst pressure, as specified in

MIL-H-5440, MIL-H-25475 or the detail specification, shall be applied at the
temperature specified in the detail specification to the component at a maxi-
mum pressure rise rate of 25,000 psi per minute. The component shall nnt
rupture under this pressure nnr shall leakage exceed that permitted in
external leakage test specified herein. The pressure may be increased above
that specified in order to secure data on actusl rupture pressure. This
should be the last teet performed because of its destructive nature. Compon-
ents that require different teet pressures in different elements shall have these
preesures applied either separately or simultaneously, whichever is the most
critical. Components that are subject to pressure in the reverse direction
such as check valves, shut off valves or accumulators shall be pressurized
in both directions, either separately or simultaneously as epecified in the
detail specification.

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●
4.5.4 Lee@e tests -

4.5.4.1 External leakage - During the course of all the tests

listed fn thfs specification, external leakage, other than a slight wetting
insufficient to form a drop through static seals, shall be cause for rejection.
Where external, dynamic seals are utilized, permissible leakage past such
seals shall be no greater than that specified in the detail specification.

4.5.4.2 Internal leakage - .

4.5.4,.2.1 Qualification or first article tests - These tests shall

be performed with the component held in the position most conducive to leak-
age. Tbe component shall be tested for leakage by applying 5 psi, 50 percent
of worki~ pressure, working pressure and pressure equal to thermal relief
valve setting or proof pressure for a period of 30 minutes each, unless
otherwise specified in the detail specification. The leakage measurements
perbd shall begin 2 minutes after tbe application of the required pressure.
Tbe cemponent shall be actuated between pressure applications. The rates
of leakage shall not exceed those specified in the detail specification. During
the first 2 minutes of each test, the leakage shall rapidly decrease frem the
flow condition to tbe rate in the fully seated condition.

4.5.4.2.2 Quality conformance tests - These tests shall be per-

fom ed with the component held in the position most conducive to leakage.
Pressure of 5 psi and working pressure shall be held for a period of 5
minutes each, unless otherwise specified in the detail speci~lcation. In each
case, the leakage measurement shall consist of the last 3 minutes of the 5-
minute period. The rate of leakage shall not exceed that specified in the detail
apecffic ation for the qualification or first artic Ie test.

4.5,5 Pressure drop - Pressure drop characteristics for a

flow range of O to 150 percent of rated flow or as specified in the detail speci-
fication shall be determined for the component. The piezometer or manometer
across the component may be used for accurate measurement where the
pressure drop range is low enough to permit its use. The pressure drop
observed at rated flow shall not exceed the value permitted by the applicable
detatl specification.

4.6.6 Extreme temperature functioning tests -

4.5.6.1 Low temperature - The component shall be connected to a

@tatic head of 1 to 3 feet of the test fluid or rated working pressure, whichever

--)0
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MIL-H-8775D

e L.
is the more critical condition.
temperature
This arr.sngement shall be maintained at a
not warmer than -65” F for 3 hours after the temperature has
stabilized at -65” F. After this period the component shall be actuated at least
two times. Variation of actuating forces or regulation, as applicable shall
not exceed that permitted by the detail specification. The quality conform ante
tests for leakage shall be performed after each actuation and the requirements
of the detail specification satsified.

4.5.6.2 Intermediate temperature - immediately following the low

temperature test (4. 5.6. 1), the test arrangement shall be warmed rapidly to
a temperature of 160” F. While the temperature is being raised, the compon-
ent shall be actuated at maximum increments of 36° F to determine satisfactory
operation throughout the temperature range. These check tests shall be made
without waiting for tern per at ure of the entire component to stabilize. For
complex components, the 36” F increment may be increased in the detail
specification to allow for time to perform functional tests.

4.5.6.3 High temperature - In the case of AN or MS standard

components, the temperature shall be maintained at 160° F, or in the ca$e of
nonstandard components, the temperature shall be maintained at the highest
value which the component is expected to encounter for alength of time
sufficient to allow all parts of the component to attain the temperature. In no
case shall the temperature at which this test is conducted be less than 160” F.
● ‘“ The component shall then be actuated at least two times.
sure actuation or regulation,
In the case of pres-
the variation from room temperature actuation
or regulation shall not exceed that permitted by the detail specification. The
quality conformance test for leakage (4. 5.4) shall be performed after each
actuation and the requirements of the detail specification satisfied.

4.5.6.4 Different ial tern perature - For components utilizing fluid

from the two eystems, the component shall be operated with the fluid temper-
ature maintained at a differential temperature of 160° F between systems or as
specified in the detail specification (as the m sxi.m um differential. possible fOr
the system). The component shall be actuated at least two times. Variation
of actuating forces or regulation, as applicable shall not exceed that per-
m itted by the detail specification for the differential temperature condition.

4.5.6.5 Temperature limits - The solenoids shall be subjected to

high temperature and low temperature test procedure of MIL-STD-81O.

4.5.7 Temperature rise - dc components shall be tested at

29V, and ac components shall be tested at 122 V or 212V for single phase or

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MIL-H-8775D

or 3 phase, respective y, at the frequent y as specified in the detail specifi -

cation. The dc teat eource shall be used to measure coil resistance prior to
and immediately after eperation at 122V or 212v SC. The dc resistance
measurements shall be used to determine temperature rise.

4.5.8 Endurance -

4.5. 8.1 General - The component shall be subjected to cyclic

eperation and to other fatigue tests, such as hydraulic impulse, in accordance
with the requirements of the detail specification which shall indicate number
of cycles, schedule of cycling, cycle rate, stroke, rate of flow, loads, tern -
perature, impulse peaks, etc. When applicable, leakage shall be checked at
25, 50, 75 end 100 percent of tbe number of cycles required. At the con-
clusion of the endurance test, tbe component shall operate satisfactorily
end shall be disassembled and carefully inspected. There shall be no evidence
excess ive wear in any part of the component.

4.5.8.2 Aircraft applications - The number of cycles selected

shall be baaed on the duty cycle ever the anticipated life of the aircraft or the
component, whichever is greater, multiplied by an appropriate safety factor.
In either case, the cycles shall be not less thar. the v-alues specified ~
Table 111.

TABLE III. ENDURANCE TEST

I Type and Usage of Component Cycles

ANor MS standard (See detail specification)

Nonstandard - Emergency 5,000
- Infrequent (less than 10
cycles per flight) 20,000
- Frequent (more than 10
cycles per flight) 50,000
- Flight control, steering,
antiskid, etc. (See detail specification)
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MIL-H-8775D

●✎ 4.5.8.3 Missile w placations - The number of cycles selected shall

be four times the estimated number of cycles to which tbe component may be
subjected during the life of the missile, including perindic missile exercise
and confidence check cycle6, except that a minimum of 2,000 cycles shall be
conducted on all ,components.

4.5.8.4 Impulse -
4.5.8 .4.1 Actuators, valves, pressure containers and similar
components - These components shall be subjected to an impulse test in
accordance with SAE ARP 1383 and as specified in the detail specification.
Where tbe SAE AR P and the detail specification conflict, the detail specifi-
cation shall take precedence.
4.5.8.4.2 Hose assemblies, tubin g, fittings, quick disconnect
couplings, filters and other transm iss ion line components - These components
shaIl be subjected to an impulse test in accordance with SAE AR P 603 and as
specified in tbe detail specification. Where the SAE ARP and tbe detail speci-
fication conflict, the detail specification shall take precedence.

4.5.9 Vibration, shock and acceleration - Components shall be

subjected to vibration, shock and acceleration test prncedure of MIL-STD-810
(methods 514, 516 & 513 respectively) when specified in tbe detail specification.

4.5.10 Humidity - Moisture resistance shall be established by

the humidity test procedure of MIL-STD-81 O. At the conclusion of this test,
the compnnent shall operate normally through 25 cycles at rated voltage.
The solennids shall be subjected to dielectric strength test specified in 4.5.19.

4,5.11 _ - C~POnents which include materials that are not

classified as fungus - inert by M IL-STD-454, Requirement 4, sha!l be subjected
to the fungus test of MIL-STD-810, Method 508.

4.5.12 Sand and dust - The components shall be subjected to

the dust test precedure of MIL-STD-81O. This test may be nmitted if all
moving parts of the compnnent are exposed only to internal fIuid.

4,5.13 Salt f% - The components shall be subjected to salt fog

test procedures of MIL-STD-81O unless it is established by the precurhg
activity that this test is not required.

4.5.14 Icing - The component shall be subjected to an icing test

if its design is such that accumulation nf ice on external surfaces or inside of
vent holes may cause malfunction. When required, this test shall be per-
formed as specified in the detail specification.
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MIL-H-8775D -+

4.5.15 Explosion proof - Components with a potential source of

ignition shall be subjected to an explosion proof test in accordance with the
explosive atmosphere test procedure of MIL-STD-81 O.

4.5.16 Electromagnetic interference - Components that cause

electromagnetic interference shall be subjected to a electromagnetic interfer-
ence test in accordance with MIL-STD-461, MIL-S~D-462 and MIL-STD-463.

4.5.17 Actuation above system pressure - Components shall be

tested for actuation, under a pressure equal to tbennal relief valve maximum
setting of tbe circuit in which they are installed. This test shall be conducted
as specified in the detail specification.

4.5.18 Reliability - Tests shall be conducted to demonstrate

compliance with reliability y requirements, including MTBF, or equivalent, as
specified in the detail specification.

4.5.19 Dielectric strength - If the dielectric test follows the

humidity test or the salt fog test, the solenoids shall be baked for 6 hours at
a maximum ambient temperature as specified in the detail specification prior
to being subjected to tbe dielectric test. All solenoids shall be subjected to a
60 Hertz alternating test voltage between terminals and case for one minute
at the following root mem square amplitudes:

(a) 1500 volts at room temperature. and pressure

(b) 1000 volts at maximum operating temperature and
altitude.

Leakage current shall not exceed one milliampere during these tests.

4.5.19.1 Subsequent dielectric tests on assembled hydraulic com -

ponent or dielectric test after environmental test on the solenoid shall be
performed at 75 percent of the above voltages for 1 minute. Flashover or
leakage current greater than one milliampere shall constitute a failure. There
shall be no distinctionbetween test voltage on prototype and production units.

4.5.20 Drop out voltage test - Solenoid operated components shall

be tested for drop out voltage by applying nominal activation voltage and slowly
reducing tbe applied voltage to 107, of the nominal activation voltage. The
solenoid shall drop out between 10% of the nominal activation voltage and the
minim um activation voltage specified in the detail specification.

4.5.21 Component cleanliness - The component shall be tested for

interal cleanliness by subjecting a representative sample of the fluid contained
in the component to a particle count using FED-STD-791, method 3009. The

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MU, -H-87’75D

Q/ component shall be actuated (if possible) durfng the sampling. The cleanliness
level shall be equal to or better than Class 8, Table I of NAS 1638. If this
procedure is not practical, the detail specification shall include a component
cleanliness test.

4.6 Test methods - Type 11 components - The test methods

described for type I components shali. also apply to type 11components with the
following exceptions:

4.5.2 shall be conducted at 275° F for 72 hours.

4,5.3.1, 4.5.3.2, 4.5.6 .3 shall be conducted at 275° F
instead of 160” F. !
4.5.6.4 shall be conducted at maximum temperature differential.

4.6.1 Endurance - The endurance tests of type II components

shall he governed by the following general test cycle, aa well aa the test
methods for type I components specified in 4.5.8. The following tests shall
he performed in the sequence indicated:

General test cycle - type H components: .

(a) Fill the component with hydraulic fluid to 90 percent —
●✍ of the total fluid vohane of the unit. Cap tbe ports and place the component in a
heating chamber in which the smbient temperature is maintained at 275” F.
Hold the component at the ambient temperature of 275” F for a period of 72
hours.

(h) Conduct the test specified in 4.5.3.1 at 275” F.

(c) Conduct the test specified in 4.5.6.1 at -65” F for a

minimum of 10 cycles. Test specimen to remain at -65” F for at least 4 hours
prior to conducting test. Increase in temperature during the test owing to
operation is permitted.

(d) Immediately following the test specified in 4.5.6.2 at

160” F, warm test arrangement rapidiy to 275” F and actuate component at
increments of approx~.atel y W oITto.determine satisfactory operation.

29
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MIL-H-8775D

(e) Conduct thetest specified in4.5.6.3at 275” Ffora

minimum of 10 cycles.

(9 Conduct 25percent of thecycles of thetestspecified

in 4.5.8 at 275” F, with the consequent length of exposure at 275” F, unless
either condition is modified as a result of 4.6.1.1.

(g) Soak component at275” Ffor2 hours. Pressure is

te be maintained durtng the first hour and reduced to approximately zero psi
for the second hour.

(h) Repeat thelowtemperature test specified in4.5..6.l

at -65” Fand the high temperature test specified in 4.5.6.3, at 275” F.

(i) Conduct 75percent of thecycles of the test specified

in 4.5.8 at 225” F unless modified as the result of 4.6.1.1.

4.6.1.1 Forthetype II system components, the contractor shall

determine tbepercentage of the cyclesa component istooperate at elevated
temperatures and the cumulative elevated temperature exposure of the compo-
nent during its life or the life of the aircraft, whichever ie greater. The
extent ofelevated temperature endurance cycling of a component shall be
based on the above determination.

4.7 Packaging, packing, and marking - Preparation for

delivery sballbe inspected forconformancetn Section5.

5. PREPARATION FOR DE LlVERY

5.1 Preservation, packeging, and packing - Preservation,

packaging, snd packing requirements shall be as specified in the detail spec i-
fIcation or by the precuring activity. Hydraulic components shall be sealed
with closures conforming to MIL-C-5501. For Navy aircraft only metal
closures confomning to MIL-C-5501 as required by NAVAIR 01-1 A-17 shall
be used.

5.2 Marking of shipm eot - In addition to any special marking

required by the contract or order, or tbp detail .specffic ation, interior packages
and exterior shipping containers shall be marked in accordance with
MIL-STD-129.

5.2.1 Reinspection m arki ~ - Reinspection marking shall be se

specified by tbe prec uring act ivlt y.

30
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,.

MIL-H-8775D

e. 6. NOT ES

Intended use - Aircraft and missile hydraulic components

6.1
are intended for use in aircraft hydraulic systems conforming to MIL-H-5440
and MIL-H-25475.

6.2 Definitions - For the purpose of this specification, the

term “component” is used to mean a valve, actuating cylinder, or similar
device of a hydraulic system.

6.2.1 A standard component is one which is assigned an MS,

AN or specification sheet part number.

Custodians: Preparing activity:

Army - AV Navy - AS
Navy - AS
Air Force -11 (Project No, 1650-0317) ‘

Reviewer activities:
Army - MI
Air Force -71
*US GOVERNMENT PR, WING OFFlrE 19761W-76G ‘4741

●L” 31
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-/

INSTRUCTIONS: In a continuingeffort to make our stmdardization documenfd better, the DoDprovidesthis form for use in
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and
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tQ waive my portion of the refe=nce~ do.-enW) or to mend -t-ud rewi-en~.

;:,,

[Fold olorU thk 11”.)

fF.ald.l.n# thk if.e)

n
DEPARTMENT OF THE NAVY
Commanding Officer
Naval Air Engineering
Systems Engineering
(SESD), Code 93
Center
Standardization Department M NO POSTAGE
N6CESS4RY
IF MAILED
IN THE
uNITED STATES
Lakehurst. NJ 08733
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POSTAGE
WILLBE pAID By THE OEPARTMENT OF THE NAVY

Commanding Officer
Naval Air Engineering Center
Systems Engineering Standardization Department
(SESD). Code 93
Lakehurst, NJ 08733
ATTN: TJM (9322)
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