Fundamentals

M15
GAS TURBINE ENGINE
Rev.-ID: 1JAN2019
Author: DaC
For Training Purposes Only
ELTT Release: Jan. 17, 2019

M15.21
Engine Monitoring and Ground Operation

EASA Part-66
CAT B1

M15.21_B1 E
Training Manual

For training purposes and internal use only.

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Lufthansa Technical Training
GAS TURBINE ENGINE EASA PART-66 M15
ENGINE MONITORING AND GROUND
OPERATION M15.21

M15 GAS TURBINE ENGINE

M15.21 ENGINE MONITORING AND GROUND OPERATION
FOR TRAINING PURPOSES ONLY!

FRA US/O-5 DaC Jun 7, 2013 ATA DOC Page 1

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GAS TURBINE ENGINE EASA PART-66 M15
ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

STARTING AND MOTORING

Outside Preparation
You have to do an outside check before you start an engine for maintenance
tasks.
Let us now do this outside check together using the generalized checklist:
S First we have to check that the chocks are in position.
S Next on the checklist is to check that the gear pins are in place. The gear
pins must be installed to prevent an accidental retraction of the landing
gear.
S Next on the checklist is the removal of the nose gear steering bypass pin.
When the bypass pin is removed, the nose gear steering is pressurized.
This prevents the aircraft being turned by the asymmetric thrust of only
one engine.
S Next on the checklist you must check the engine inlet and exhaust.
S Now we check that cowls and access panels are closed and secured.
S The final check is to ensure that the ramp area is clear.
This completes the outside check.
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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21
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Inlet Exhaust

Figure 1 Outside Preparation

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GAS TURBINE ENGINE EASA PART-66 M15
ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

Cockpit Preparation
We also use a generalized checklist for the cockpit check.
Before you start the engine you must have a look in the technical log book to
see if there is any open item which makes engine start impossible.
We need electrical and pneumatic power for engine start.
Normally you get this power from the APU. The indications show that the APU
supplies electrical and pneumatic power.
Next you must do an engine fire test to check that the engine fire warning
system works properly.
Now you have to check that the parking brake is set and that the parking brake
accumulator pressure is OK. The parking brake is set by the position of the
parking brake handle and you can check the accumulator pressure on the
brake pressure indicator.
On the indicator the accu pressure is in the green range which means that
sufficient brake pressure is available.
The last item on this generalized checklist indicates that you need to switch on
the beacon. The switch is on the external lights panel.
This alerts everybody to stay clear of the hazardous area.
FOR TRAINING PURPOSES ONLY!

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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21
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Figure 2 Cockpit Preparation

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GAS TURBINE ENGINE EASA PART-66 M15
ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

Auto Start
You can activate the engine starting system in three different modes:
S the auto start mode,
S the manual start mode,
S and the engine motoring mode.
To show you the three starting modes we will use the controls and indications
of an Airbus 320.
First you start the engine in the auto start mode. In this mode the FADEC
system computer controls the whole start sequence. As you know this
computer is usually called the engine control unit or ECU in short. If a start
parameter runs out of limit, this engine control unit aborts the engine start
automatically.
You begin the auto start by moving the engine mode selector switch to
IGN / START. When the engine mode selector switch is in the ignition start
position, the engine start page appears on the system display.
You must now check the oil indication displayed on the start page for the actual
quantity of oil in the system.
You must also check the duct pressure. For the engine start you need a
minimum duct pressure of 25 psi. If the duct pressure is lower, a start failure
could occur.
When you switch the engine master switch to ON, a signal is sent to the fuel
low pressure valve. The valve opens and the fuel flows to the hydro mechanical
unit. A signal is also sent to the engine control unit, which will open the starter
valve, so that air can flow to the starter. You can monitor the position of the
starter valve on the engine start page.
Now the starter motor turns the N2 rotor system. When N2 speed increases,
FOR TRAINING PURPOSES ONLY!

you must check if the oil pressure is increasing also.

When N2 has increased to 16%, the ECU activates one ignition system, either
system A or B. The engine and warning display shows that the ignition system
is activated. The engine start page also shows the active igniter.
When the N2 of the engine reaches 22%, the ECU send a signal to the hydro
mechanical unit to open the fuel metering valve.

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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21
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Figure 3 Auto Start

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GAS TURBINE ENGINE EASA PART-66 M15
ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

Auto Start cont.

Now the fuel pressure can open the de−energized fuel shut-off valve and the
fuel flows to the spray nozzles. This is indicated on the fuel flow indication.
Now fuel and ignition are available to light up the engine. Light up is shown by
the increasing EGT indication.
The engine will now accelerate up to the thrust lever position which must be in
idle stop. When the engine N2 passes the starter cut out speed, the ECU
sends a signal to close the starter valve and deactivates the ignition system.
Now the engine speed stabilizes in idle. To complete the starting sequence turn
the engine mode switch to normal.
When you switch the mode selector back to normal, the nacelle temperature
replaces the starter valve indication on the engine page.
When you have finished all necessary maintenance checks with the running
engine, you can shut down the engine. You do that by moving the engine
master switch to the off position.
When you switch the engine master switch to off, a close signal is sent to the
fuel shut-off valve and the fuel low pressure valve.
The engine now spools down.
FOR TRAINING PURPOSES ONLY!

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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21
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Figure 4 Auto Start

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GAS TURBINE ENGINE EASA PART-66 M15
ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

Manual Start
During an engine manual start you have to watch the start sequence very
closely because you must abort the engine start manually when there is a start
failure. This is done by moving the engine master switch to off.
Another difference to the automatic start is that you need the engine manual
start push-button.
The manual start sequence begins with the same action as the automatic start.
The engine start page now appears on the system display.
The manual start push-button opens the starter valve and the air flows to the
starter.
The engine N2 speed increases. When it exceeds 20%, you must switch the
engine master switch to ON. When the engine master switch is in on, a signal
is sent to the fuel low pressure valve. The valve opens and the fuel flows to the
hydro mechanical unit. At the same time a signal is sent to the engine control
unit which activates both ignition systems. The engine control unit also sends a
signal to the hydro mechanical unit that opens the fuel metering valve and the
fuel flows to the fuel nozzles.
With engine light-up a critical phase of the manual start sequence begins, so
you must monitor the indications very carefully.
When light-up happens, the engine accelerates to idle. At an N2 speed of 50%
the ECU will close the starter valve and deactivate the ignition system.
The engine speed stabilizes in idle. The final task of the manual start sequence
is to turn the engine mode selector to normal. Also make sure that the manual
start push-button is switched to off.
You have now successfully started the engine in manual start mode.
After the maintenance work is complete, you can shut down the engine.
FOR TRAINING PURPOSES ONLY!

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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21
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Figure 5 Manual Start

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GAS TURBINE ENGINE EASA PART-66 M15
ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

Motoring
An engine motoring is necessary for engine leak and system checks. During
engine motoring only the starter motor turns the engine. The ignition system
must be deactivated. When you carry out a motoring, you must observe the
starter limits closely.
You can either do dry or wet motoring depending on the necessary
maintenance work.
First we do an engine wet motoring.
You need a clock to observe the starter limits. In our example the starter duty
time is two minutes. First you must move the engine mode selector to crank. In
this position the ignition system is deactivated.
You must open the starter valve with the manual start push-button. The starter
will accelerate the engine up to the motoring speed.
When the N2 speed is higher than 15%, you must set the engine master switch
to ON. This starts the fuel flow.
When you see that the fuel flow indication increases, you must set the engine
master switch back to OFF.
Now you know all necessary actions for a wet motoring.
Before the starter duty time is exceeded you must close the starter valve.
Now see that the engine spools down.
After each wet motoring you must remove the remaining fuel from the
combustion chamber. This is done by dry motoring for 1 minute.
After one minute of dry motoring you must close the starter valve again.
To set the starting system back into its normal condition you must turn back the
engine mode selector switch to normal.
FOR TRAINING PURPOSES ONLY!

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OPERATION M15.21
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Figure 6 Motoring
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GAS TURBINE ENGINE EASA PART-66 M15
ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

Start Failures
In this segment we will introduce you to four typical start failures. You will see
the reasons for these failures and the actions you must take when the failures
occur.
These start failures are:
S the hung start,
S the wet start,
S the engine stall
S and the hot start.
Hung Start
An engine start is called a hung start when the engine lights up but accelerates
too slowly. This could happen, for example, if
S the duct pressure of the starter air is too low,
S the starter cuts out to early or
S the fuel metering is wrong.
When a hung start occurs, the start sequence must be aborted to prevent the
turbine overheating.
When a hung start occurs in the auto start mode, the ECU aborts the start
sequence automatically.
You will be alerted by a fault light on the engine mode selector panel and a
start fault message on the engine and warning display.
You also get a corrective action message that advises you to set the engine
master switch to OFF.
This will reset the system and all warnings disappear.
FOR TRAINING PURPOSES ONLY!

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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21
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Figure 7 Hung Start

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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

Wet Start
You get a wet start when the engine speed increases normally and fuel is
sprayed into the combustion chamber, but the engine does not light up. This
happens when the ignition system does not work.
When a wet start occurs, the start sequence must be aborted as soon as
possible because fuel collects in the combustion chamber.
When the ECU detects a wet start, it cuts fuel and ignition off but keeps the
starter valve open and you will be alerted by local and central warnings.
After an aborted wet start the ECU automatically does a dry motoring which is
called auto crank.
After 25s of dry motoring the ECU initializes a second auto start, but this time
with both ignition systems on.
If the second start attempt also fails, the ECU aborts the engine start
completely and advises you to set the engine master switch to OFF.
FOR TRAINING PURPOSES ONLY!

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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21
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Figure 8 Wet Start

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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

Engine Stall
When the engine stalls, the EGT indication fluctuates.
The engine stall could happen if the fuel metering is wrong or if an engine bleed
valve is stuck in the close position or if the compressor performance is
degraded.
When a stall occurs, the start sequence must be aborted because the turbine
could be overheated or the compressor damaged.
When the ECU detects a stall in an auto start sequence, it aborts the start
sequence automatically and triggers the corresponding warnings.
FOR TRAINING PURPOSES ONLY!

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OPERATION M15.21
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Figure 9 Engine Stall

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ENGINE MONITORING AND GROUND Starting and Motoring
OPERATION M15.21

Engine Hot Start

A hot start occurs during the start sequence when the actual EGT is higher
than the max allowable start value. This could happen if the fuel metering is
wrong or fuel from a previous wet start is not blown out completely.
When a hot start occurs, the start sequence must be aborted immediately
before the turbine becomes overheated.
FOR TRAINING PURPOSES ONLY!

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OPERATION M15.21
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Figure 10 Engine Hot Start

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ENGINE MONITORING AND GROUND Maintenance Practices
OPERATION M15.21

MAINTENANCE PRACTISES

F.O.D.
and what we can all do about it.
F.O.D. or Foreign Object Damage, or Foreign Object Derbris is often
associated with a Bird Strike. However, even the smallest foreign objects such
as screws, nuts, etc. on aircraft and aircraft components cause considerable
damage, which must be repaired at high cost, and even lead to total losses of
aircraft (Concorde crash in Paris in 2000).
The abbreviation ”FOD” is known / associated with the following two meanings:
FOD − Foreign Object Debris:
Any object or object in an aeronautical area that is not where it should be and
thus can lead to injury / damage to persons or objects.
FOD − Foreign Object Damage:
A type of damage that is caused by inadequate FOD prevention measures,
work errors, or the forces of nature as a result of which persons come to harm,
or − objects have got into / onto an engine / aircraft and there have suffered
damage or operational failure caused this.
FOR TRAINING PURPOSES ONLY!

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Figure 11 F.O.D.
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ENGINE MONITORING AND GROUND Maintenance Practices
OPERATION M15.21

Perform FOD prevention ensure work on the object (engine / APU / component / assembly)
This list does not claim to be exhaustive. It serves the general understanding, S Engine openings, air inspections, pipes, but also disassembled
Consolidation of the topic and support during regular / daily checks. There must components, engine blades (e.g. cooling air bores) or assemblies / modules
were inspected during and after completion of the work closed or covered.
always be a addition of special departmental features / control points. FOD
Prevention must be active and are incorporated into the daily routine. S Bags on the personal work clothing may have been closed before starting
work.
in the work shop:
S Before connecting or closing the engine / APU / assemblies / modules, the
S No unused material such as screws, washers, nuts, bits, rivets or wire − /
following must be done, unless otherwise specified is already specified
drill residues on the Floors, welding and soundproofing booths or
using the corresponding job card, checks are generally carried out for
workbenches and production machinery / Test bench areas available
foreign body/contamination has been carried out
S Damaged, expired tool is marked and the output areas are marked for
replacement. / Repair supplied S Particularly during and after endoscopy checks, the employees concerned
paid attention: Sealing of the BSI ports and cover to drive the rotor systems
S Employee tool is checked for completeness and according to Quality according to the manufacturer / Customer specifications.
Management specifications. In the event of losses appropriate measures
S The marking of open engine / APU / component openings can be done by
have been initiated (appropriate search in the specialist area or, most
filling out the (name / department / component PN) Safety tags / hanger
recently known storage / assembly / disassembly areas and, if applicable,
hanger was observed When working on core engines, assemblies or
loss report)
modules, the prefabricated plastic covers are used for each work step.
S Unaccounted, unaccompanied, unauthorised, non−departmental persons
were reported S Any tools or devices temporarily used for the purpose of disassembly /
assembly in a engine, APU or module / component have a marking
S During repair work in the production areas / infrastructure (in particular (towards the outside). Visible safety flags or hanger signs e.g. ”Remove
crane systems or ceiling areas), measures were taken (e.g. by covering) to before Flight!”
prevent contamination / F.O.D. of engines / assemblies / components. If
S Tools or consumables that are no longer needed are returned to the output
necessary, a supervisor was provided.
areas.
Conclusion:
F.O.D Prevention affects every employee!
F.O.D Prevention must be a daily routine in the workflow!
Every employee must be aware of the great damage even the smallest foreign
FOR TRAINING PURPOSES ONLY!

bodies can cause in the engine.

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ENGINE MONITORING AND GROUND Maintenance Practices
OPERATION M15.21

MAINTENANCE PRACTISES

Fan Blade Damage Limits

During engine operation foreign objects can be sucked in by the engines.
These objects can impact with the fan blades and damage them. Therefore,
ground surface around an operating engine must be clean to prevent any
foreign object damage.
A damaged fan blade can still be used if damage does not exceed acceptable
limits or if the damaged area is reworked.
When the damaged area of the blade is reworked, a smooth transition between
the reworked surface and the surrounding undamaged areas of the blade is
ensured.
FOR TRAINING PURPOSES ONLY!

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Figure 12 Fan Blade Damage and Repair

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OPERATION M15.21

Fan Blade Damage Limits cont.

There are many examples of fan blade damage. Let us look at three of them in
more detail. Typical surface damages are
S nicks,
S dents,
S scratches.
A nick is a sharp−bottomed depression with rough outer edges.
A dent is a sharp−bottomed depression. The damaged material is distorted but
not separated.
A scratch is a narrow, shallow mark or line. It is caused by a sharp pointed
object striking the surface of the blade.
FOR TRAINING PURPOSES ONLY!

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Figure 13 Different Fan Blade Damages

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Fan Blade Damage Limits cont.

Damage on a fan blade can only be reworked if they are within certain limits as
shown in the aircraft maintenance manual. In the manual you will find limits for
the damage depth, damage length and the total damage permitted per blade.
Note also that because of the load distribution during operation, these damage
limits are different for specific areas across the blade.
The fan blade is therefore divided into specific areas.
In areas of the blade where stress is low, the damage permitted can be larger
than in areas where stress on the blade is high. For example, there is very high
stress in the blade root area, and therefore no damage is permitted in this area.
The fan blade is also divided vertically into damage limit areas. These are the
leading edge area, the surface area and the trailing edge area.

Example:
On critical areas of the blade root and the blade shroud where stress is very
high, scratches may not be deeper than 0.076 mm.
At the leading edge and the trailing edge of the blade root and shroud,
scratches may not be deeper than 0.152 mm.
In the middle of the blade scratches may only be 0.381 mm deep.
In areas where stress on the blade is low, scratches may be 1.016 mm deep.
FOR TRAINING PURPOSES ONLY!

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OPERATION M15.21
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Figure 14 Fan Blade Areas and Damage Limits

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OPERATION M15.21

Fan Blade Damage Limits cont.

If there is a nick, dent or scratch on a fan blade that is within the limits, the
damage is reworked. This process is called blending.
In the graphic you can see a damaged surface after the blending process has
taken place. The highlighted area shows the material removed from the original
damage area.
The removed material reduces the weight of the fan blade and causes
imbalance.
FOR TRAINING PURPOSES ONLY!

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OPERATION M15.21
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Figure 15 Fan Blade Blending

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ENGINE MONITORING AND GROUND Maintenance Practices
OPERATION M15.21

Engine Trend Monitoring

Modern engines are very reliable and economic, but the performance of the
engine modules decrease during their lifetime.
To prevent larger performance reductions or even engine problems during
flight, you need a monitoring tool that alerts us to a problem at an early stage.
This tool is called engine trend monitoring.
The engine trend monitoring is done in the workshop by analyzing engine data
that is periodically recorded during flight by the aircraft condition monitoring
system.
The ACMS provides this data on a print-out from the cockpit printer, and it can
also usually transmit the data via the ACARS data link to the ground.
The transmitted engine data is analyzed by a computer system in order to find
any parameters that indicate a trend towards a limit.
3 different analyses are usually done:
S the thermodynamic analysis,
S the mechanic−dynamic analysis, and
S the oil consumption analysis.
The thermodynamic analysis checks the pressures and temperatures along the
gas flow path. It also monitors the feedback signals from the VSV and VBV, the
active clearance control, and the fuel flow.
The data gives exact information about the condition of the engine components
involved in the thermodynamic process.
The mechanic-dynamic analysis mainly checks for failures in the rotor system,
for example imbalances and bearing failures. To do this it checks engine
vibration and rotor speed signals.
FOR TRAINING PURPOSES ONLY!

The oil consumption analysis generates an alert when the oil consumption
exceeds a certain level.

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OPERATION M15.21
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Figure 16 Engine Trend Monitoring

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OPERATION M15.21

Engine / Compressor Water Wash

General
During the use of aircraft engines the internal components like the compressors
and turbines contaminate. This results in a loss of engine efficiency. To
maintain the required engine thrust, a higher fuel ingestion is needed than on
an engine with better efficiency.
A core engine wash lowers the Exhaust Gas Temperature (EGT), thus reducing
the fuel demand. This has the effect of not only cutting costs but of also
sparing the environment by producing lower emissions and consuming less
fossil fuels. At the same time the improvement of the EGT margin leads to
longer engine on-wing time, as the material is subject to less stress, and also
to lower overhaul costs. All in all, an engine wash substantially reduces aircraft
operating costs.
Procedure
To wash the engine, water and a cleaning solvent is injected by spray nozzles
into the core engine during motoring. The used equipment varies, depending
on the maintenance organisation. The above mentioned procedure is repeated
several times. On some engines preparation work like removing sensors or
covering some inlets is necessary. An engine run to dry out the engine as final
work also may be necessary. Further information is given in the AMM Chapter
72.
CAUTION: OBSERVE THE STARTER DUTY TIME TO PREVENT
DAMAGE TO THE STARTER
FOR TRAINING PURPOSES ONLY!

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OPERATION M15.21

EGT

EGT max.
limit
EGT margin

Engine with bad efficiency

Engine with medium efficiency

Engine with best efficiency

FOR TRAINING PURPOSES ONLY!

Engine speed
T flat rate

Figure 17 Performance chart

FRA US/O-5 DaC 01.05.2014 06|Compr. washingL1|A/B1 Page 37

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ENGINE MONITORING AND GROUND Maintenance Practices
OPERATION M15.21

Engine Borescoping
In this segment we will show the principles of one kind of visual inspection of
engine components, known as borescope inspection.
A borescope inspection is used to inspect the internal gas path components of
the engine.
These inspections are mostly necessary after FOD ingestion or an overheat
condition of the engine.
If you need to inspect an engine, you will find that with a torch you can only
look into the engine inlet or turbine outlet, but with a borescope you can inspect
the internal components of the engine without taking the engine apart.
Note that a borescope inspection is only done by a especially trained people
because it requires a lot of experience, but very often a second person is
needed for the borescope inspection as you will see later.
This type of inspection also makes the maintenance concept of on−condition
monitoring possible. This means that parts can be left on the engine as long as
possible. They do not have to be replaced after a fixed operating time even if
they are still serviceable.
FOR TRAINING PURPOSES ONLY!

HAM US/F-4 SwD 01.03.2008 07|Eng Borescp|L1|A/B1 Page 38

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Borescope Inspection
FOR TRAINING PURPOSES ONLY!

Figure 18 Principles of Borescope Inspection

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Engine Borescoping cont.

Now take a look at the basic borescope equipment.
There is
S the borescope itself,
S the light source, and
S the light transmitting cable.
You will also find that the borescope can have either a rigid probe or a flexible
probe.
FOR TRAINING PURPOSES ONLY!

HAM US/F-4 SwD 01.03.2008 08|Eng Borescp|L1|A/B1 Page 40

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OPERATION M15.21
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Figure 19 Borescope Equipment

HAM US/F-4 SwD 01.03.2008 08|Eng Borescp|L1|A/B1 Page 41
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Engine Borescoping cont.

Here you can see the internal components of the borescope which help to
transmit the picture in the field of vision to the eyepiece.
These internal components include optical parts like
S lenses,
S prisms,
S objectives and
S light guiding glass fibres.
In flexible probes the light and also the picture is transmitted by the glass
fibres.
To light up the area inside the engine, a high intensity light is transmitted from
the light source to the probe tip.
Most typical borescopes have different angles of view and different adaptors
for the eyepiece. These adaptors are interchangeable and have attachments
for cameras and video cameras.
FOR TRAINING PURPOSES ONLY!

HAM US/F-4 SwD 01.03.2008 09|Eng Borscp|L1|A/B1 Page 42

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Figure 20 Borescope Internal Parts

HAM US/F-4 SwD 01.03.2008 09|Eng Borscp|L1|A/B1 Page 43
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Engine Borescoping cont.

A modern type of a borescope is the videoscope. Here the optical components
are replaced by electronic components.
The videoscope has a hand−held monitor with a flexible probe and a light
source with a computer.
The image and data measurements are visible on the monitor. The probe tip
can be controlled by the joystick on the monitor handle.
FOR TRAINING PURPOSES ONLY!

HAM US/F-4 SwD 01.03.2008 10|Eng Borescp|L1|A/B1 Page 44

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Figure 21 Videoscope
HAM US/F-4 SwD 01.03.2008 10|Eng Borescp|L1|A/B1 Page 45
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Engine Borescoping cont.

If you have to insert a borescope into an engine, you need to find a hole big
enough to let it through.
In the compressor and turbine case of modern engines there are many
borescope ports, usually one port per stage.
You will find these borescope ports on the compressor and turbine usually at
the three o’clock or nine o’clock position. You can get the precise position from
the maintenance manual.
You can also use alternate openings by removing external parts, such as
igniter plugs or fuel nozzles.
FOR TRAINING PURPOSES ONLY!

HAM US/F-4 SwD 01.03.2008 11|Eng Borescp|L1|A/B1 Page 46

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Figure 22 Borescope Ports

HAM US/F-4 SwD 01.03.2008 11|Eng Borescp|L1|A/B1 Page 47
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Engine Borescoping cont.

As you can see here, the borescope is almost completely inserted in the stator
between two stator vanes of the compressor or the turbine.
The mechanic can see the rotor blades in front of the borescope when the
viewing direction is facing forward as shown in this position.
The mechanic can then turn the borescope around to see the rotor blades
behind the borescope.
FOR TRAINING PURPOSES ONLY!

HAM US/F-4 SwD 01.03.2008 12|Eng Borescp|L1|A/B1 Page 48

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Turbine Rotor Blade

Figure 23 Viewing Directions

HAM US/F-4 SwD 01.03.2008 12|Eng Borescp|L1|A/B1 Page 49
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Engine Borescoping cont.

When one mechanic looks at the rotor blades, another mechanic turns the
corresponding rotor system slowly.
The N1 rotor is usually turned directly by hand.
The N2 rotor can be turned by a hand cranking device which is connected to
the accessory gearbox or the transfer gearbox.
You do not need a second person to crank the N2 rotor if you install an
automatic cranking drive. This drive has an pneumatic motor which can be
controlled by a foot operated toggle switch.
FOR TRAINING PURPOSES ONLY!

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Figure 24 Rotor Cranking

HAM US/F-4 SwD 01.03.2008 13|Eng Borescp|L1|A/B1 Page 51
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OPERATION M15.21

Soap Sampling
Oil samples are taken from the engine oil tank for the Spectrometric Oil
Analysis Program. A plastic bottle with a hose is used to take the oil sample.
The hose is inserted through the sampling tube of the filler assembly into the oil
tank.
A number of safety precautions must be observed for SOAP sampling.
S You should always use a new plastic bottle and a new hose to prevent
contamination of the oil.
S Remember to wait at least 5 minutes after engine shut-down before you
open the oil tank filler cap.
S You should wear gloves to protect your hands, because the oil can be hot.
S You must close the bottle and label it immediately after the sample is taken.
The label is necessary to prevent samples getting mixed up.
You can see that the label must have details of the aircraft registration, the
engine position, the engine serial number, the station where the sample is
taken, the date, and the time of the sample.
When the label is completed, the sample can be sent for analysis.
FOR TRAINING PURPOSES ONLY!

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Figure 25 SOAP Sampling

HAM US/F-4 SwD 01.03.2008 14|SOAP Sampling|L1|A/B1 Page 53
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OPERATION M15.21

Magnetic Chip Detector Inspection

Magnetic chip detectors are inspected at fixed intervals.
For safety reasons maintenance staff should only check the detectors on one
engine and a cross−check by a second mechanic is required. This is to
minimize the effect of working errors.
A wrong detector installation can lead to a leak in the oil system and an
in-flight shut-down of the engine.
Typically the magnetic chip detectors are designed so that they can be
removed without tools.
Note, that the detectors may be hot from the oil so you should wear gloves to
protect your hands.
You remove the magnetic chip detector by pressing it in and then by turning it
counter clockwise.
When a detector is removed, a check valve closes in the housing to prevent an
oil leakage.
You must handle the magnetic chip detectors with care. Any chips must be
removed with a sheet of paper and secured for analysis and the detector must
be cleaned before you install it again.
FOR TRAINING PURPOSES ONLY!

HAM US/F-4 SwD 01.03.2008 15|MCD Inspection|L1|A/B1 Page 54

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Figure 26 Magnetic Chip Detector Inspection

HAM US/F-4 SwD 01.03.2008 15|MCD Inspection|L1|A/B1 Page 55
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Magnetic Chip Detector Inspection cont.

Some chip detectors have two seals − a reusable seal and an o−ring.
Other chip detectors just have two o−rings, like the one on the left.
The old o−rings in the magnetic chip detectors must be replaced with new ones
to help prevent leakage.
Keep in mind that the most common work error is to forget to install the
o−rings.
You must check, that the detector has engaged correctly.
FOR TRAINING PURPOSES ONLY!

HAM US/F-4 SwD 01.03.2008 16|MCD Inspection|L1|A/B1 Page 56

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Figure 27 Magnetic Chip Detector Installation

HAM US/F-4 SwD 01.03.2008 16|MCD Inspection|L1|A/B1 Page 57
M15.21 B1 E

TABLE OF CONTENTS
M15 GAS TURBINE ENGINE . . . . . . . . . . . . . 1
M15.21 ENGINE MONITORING AND
GROUND OPERATION . . . . . . . . . . . . . . . . . . . 1
STARTING AND MOTORING . . . . . . . . . . . . . . . . . . . . . . 2
OUTSIDE PREPARATION . . . . . . . . . . . . . . . . . . . . . . . . . 2
COCKPIT PREPARATION . . . . . . . . . . . . . . . . . . . . . . . . . 4
AUTO START . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
MANUAL START . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
MOTORING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
START FAILURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
WET START . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
ENGINE STALL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
ENGINE HOT START . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
MAINTENANCE PRACTISES . . . . . . . . . . . . . . . . . . . . . . 22
F.O.D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
PERFORM FOD PREVENTION ENSURE . . . . . . . . . . . . 24
MAINTENANCE PRACTISES . . . . . . . . . . . . . . . . . . . . . . 26
FAN BLADE DAMAGE LIMITS . . . . . . . . . . . . . . . . . . . . . 26
ENGINE TREND MONITORING . . . . . . . . . . . . . . . . . . . . 34
ENGINE / COMPRESSOR WATER WASH . . . . . . . . . . . 36
ENGINE BORESCOPING . . . . . . . . . . . . . . . . . . . . . . . . . . 38
SOAP SAMPLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
MAGNETIC CHIP DETECTOR INSPECTION . . . . . . . . . 54

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M15.21 B1 E

TABLE OF FIGURES
Figure 1 Outside Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Figure 2 Cockpit Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 3 Auto Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 4 Auto Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 5 Manual Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 6 Motoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 7 Hung Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 8 Wet Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 9 Engine Stall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 10 Engine Hot Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 11 F.O.D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 12 Fan Blade Damage and Repair . . . . . . . . . . . . . . . . . . . . . . . . . 27
Figure 13 Different Fan Blade Damages . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 14 Fan Blade Areas and Damage Limits . . . . . . . . . . . . . . . . . . . . 31
Figure 15 Fan Blade Blending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 16 Engine Trend Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Figure 17 Performance chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Figure 18 Principles of Borescope Inspection . . . . . . . . . . . . . . . . . . . . . . 39
Figure 19 Borescope Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Figure 20 Borescope Internal Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Figure 21 Videoscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Figure 22 Borescope Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Figure 23 Viewing Directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Figure 24 Rotor Cranking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Figure 25 SOAP Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Figure 26 Magnetic Chip Detector Inspection . . . . . . . . . . . . . . . . . . . . . . 55
Figure 27 Magnetic Chip Detector Installation . . . . . . . . . . . . . . . . . . . . . 57

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TABLE OF FIGURES

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TABLE OF FIGURES

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