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Training Manual ARRIE

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AIRCRAFT MANUFACTURERSUPPLY :

Installed on the deckingbeside the MGB

LEVELSIGHT GLASS

Air vent to exhaust pipe

To pressure pump

Air vent to exhaust pipe

Oil from the oil cooler

TANK

TEMPERAPROB

Oil frooil coo


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OIL PUMPS - GENERAL - DESCRIPTION

Function

The pumps ensure oil circulation.

Position

- In the system: on engine oil system inlet and outlet.

- On the engine: the pump unit is mounted by bolts on the

rear face of the accessory gearbox.

Main characteristics

- Type : gerotor

- Quantity : 4

- Pressure relief valve setting : 1500 kPa (217.5 PSI)

- Check valve.

Description

The pump unit comprises a body containing(one pressure pump with pressure relief scavenge pumps).

The four pumps are driven by means of a coconnected to the accessory drive (N1 drive).


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Type :Gerotor

Quantity :4

Pressure reliefvalve setting :

1500 kPa (217.5 PSI)

Check valve

DRIVESHAFT

PUMPUNIT

PRESSUREPUMP

From oil tank

To oil cooler

Checkvalve


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OIL PUMPS - OPERATION

Operating principle of a gerotor pump

A gerotor pump is a pump which comprises an inner rotordriving an outer rotor.

The inner rotor is eccentric to the outer rotor and has oneless lobe than the outer rotor has spaces.

Because of the eccentricity, the size of the chambersformed between the two rotors varies with rotation.

Thus the oil is drawn in as the low pressure chamber sizeis increasing and is forced out under pressure as the highpressure chamber size decreases.

The process is continuous for each chamber, ensuring asmooth, positive flow.

Operation of the pressure pumpThe pressure pump draws the oil from the tank and forcesit out under pressure in the supply system.

The whole pump flow is used (full flow ; pressure isfunction of the rotation speed, oil viscosity and oiltemperature).

Pressure relief valve operation

If the oil pressure exceeds the valve setting theand allows the oil to return to the pump inlet

In normal operation the valve is closed and oexceptional circumstances, e.g. starting wtemperature.

Operation of the scavenge pumpsThree scavenge pumps, one for the reduction gfor the gas generator bearing, one for thebearings and the accessory gear train, return oil cooler and the tank.

The pump flow is higher than that of the pre(dry sump type system).

Pressure pump outlet check valve ope

When the oil pressure is very low, e.g. enginat the beginning of start, the valve is closeprevent flow between the pump and system.


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Oil outlet

Oil inlet

PUMPBODY

HIGH PRESSURECHAMBER

LOW PRESSURECHAMBER

INNER ROTOR(driven at a speedproportional to N1)

INNER ROTOR

OUTER ROTOR(driven by

the inner rotor)

OUTER ROTOR

Normal running (valve clo

Overpre(valve o

Pressurerelief valve

PRESSUREPUMP

From oil tank

To oil cooler

SCAVENGEPUMPS

Cheval


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OIL VALVE ASSEMBLY

Function

The assembly houses a check valve, an electrical magneticplug and the strainer for the gas generator rear bearing.

The check valve prevents oil flow from the cooler to theengine when the pressure is very low (engine stopped).

The electrical magnetic plug collects ferrous particleswhich may be in the oil.

Position

- In the system : downstream of the scavenge pumps

- On the engine : on the rear face of the accessory gearbox.


- Check valve setting : 15 kPa (2.17 PSI).

Main components- Check valve

- Electrical magnetic plug and strainer

- Scavenge strainer for the gas generator rear bearing.

Check valve description

The check valve comprises :

- A piston

- A spring

- A cover.

Check valve operation

Engine running

The outlet pressure of the scavenge pumppiston, compressing the spring thus allowincooler.

Engine stopped

The scavenge pump outlet pressure is very l

Spring pressure closes the valve and prevenfrom the cooler into the engine.


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g

Check valvesetting :

15 kPa (2.17 PSI)

CHECKVALVE

SCAVENGE STRAINER(for the gas generator rear bearing )

Mountingflange

OIL VALVEASSEMBLY

OIL VALVEASSEMBLY

To oil cooler

VA(en

To oil cooler

VALVE OPEN(engine running)


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OIL FILTER - GENERAL

Function

The filter retains particles that may be in the oil. The filterhousing forms a fuel - oil heat exchanger.

Position

- In the system : downstream of the pressure pump

- On the engine : on the left rear face of the accessorygearbox.


- Type : glass fibre cartridge

- Filtering ability : 20 microns

- Mechanical pre-blockage indicator setting : 2C1 : P 120 kPa (17.4 PSID) 2C2 : P 250 kPa (36.25 PSID)

- By-pass valve setting : 2C1 : P 420 kPa (60.9 PSID) 2C2 : P 563 kPa (81.6 PSID) .

Main components

The filter contains the interchangeable filteraccessible by a cover and the fuel - oil heat e

It also provides the support for accessories (pindicator, low oil pressure switch, oil pressureoutlet unions).


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g

Fuel outlet (fuel - oil heat exchanger)

FILTERCOVER

OILFILTER

VISUAL PRE-BLOCKAGEINDICATOR

(re

(

Type :Glass fibre cartridge

Filtering ability :20 microns

Mechanical pre-blockageindicator setting :

- 2C1 : P 120 kPa (17.4 PSID)

- 2C2 :

P 250 kPa (36.25 PSID) By-pass valve setting :

2C1 P 420 kP (60 9 PSID)

Fuel inlet (fuel - oil heat exchanger)

OILFILTER

From oil tank


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OIL FILTER - DESCRIPTION - OPERATION

Description

The main components of the filtering unit are the following :

- Filter base

- Filter cover (screwed onto the filter base)

- Fuel-oil heat exchanger fitted with walls which permitfuel flow around the oil filter casing

- Fibre glass cartridge (filtering element)

- By-pass valve (fitted inside the filter housing)

- Pre-blockage indicator.

The filter base incorporates :

- Mounting points for the following : Low oil pressure switch Oil pressure transmitter Oil outlet unions (compressor bearing lubrication

and rear bearing lubrication) Fuel inlet and outlet unions.

O'ring seals ensure the oil filter sealing.

Operation

Filtering (normal condition)

The oil supplied by the pressure pump passesfilter from outside to inside. The filtered oil ththe engine for lubrication.

The oil is also used to heat the fuel throexchanger as the fuel flows around the oil fi

Pre-blockage

If the filter begins to become blocked the pressuracross the filter increases. At a given pressura red mechanical indicator pops out. The oil flow through the filter.

Blockage

If the pressure difference exceeds a given vapass valve opens and unfiltered oil passes to


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FILTERCOVER

PRE-BLOCKAGEINDICATOR

NORMA

FILTERING(20 microns)

FILTERINGELEMENT

FUEL - OIL HEATEXCHANGER

Oil inlet

FILTERBASE

Fuel outlet (fuel - oil heat

exchanger)

Fuel inlet

(fuel - oil heat exchanger)

Fue(fuel - oi

Oil outlet

PRE-BLOCKAGE


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FILTER PRE-BLOCKAGE INDICATOR

Function

The indicator detects the onset of filter blockage.

Position

In the system : between inlet and outlet of the oil filter.On the engine : on the filter housing cover.

Main characteristics- Type : differential- Setting :

2C1 : P 120 kPa (17.4 PSID) 2C2 : P 250 kPa (36.25 PSID).

DescriptionThe pre-blockage indicator comprises the following parts :- Indicator body including :

Mounting flange Filter upstream pressure inlet Filter downstream pressure inlet

- Red indicator piston

- P piston- Transparent cover

Operation

Normal condition

Filter downstream pressure plus spring pressuthan upstream pressure. The two pistons are hby magnetic force. The indicator is not visib

Pre-blockage condition

Filter upstream pressure exceeds downstreampressure and the P piston moves down

This breaks the magnetic hold and the indicapushed out by its spring. The indicator is vis

The bi-metallic thermal lock ensures that doesn't operate when a large P temperature (locked below 50 C (12

The indicator is re-armed by pushing in the i


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< 50 C (122 F) > 50 C (122 F)

Downstream

pressure

Downstr

pressu

Upstream pressure

NORMAL CONDITION

Red - 2C1 : P - 2C2 : P

PRE-BLOCKAGE

Oilfilter

FILTER

PRE-BLOCKAGEINDICATOR

Filter

cover

From oil tank To

Oil filterPressurepump PRE-

IN

Type :

differential

Setting :- 2C1 : P 120 kPa (17.4 PSID)

- 2C2 : P 250 kPa (36.25 PSID)


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OIL COOLER

Function

The oil cooler cools the oil after it has passed through theengine.

Position

- In the system : between the scavenge pumps and the tank

- On the aircraft : it is installed in front of the maingearbox.


- Supplied by the aircraft manufacturer

- Type : air-oil cooler

- Differential and thermostatic by-pass valve.

Main components

- Oil cooler

- Differential and thermostatic by-pass valv

- Unions (oil inlet and outlet)

- Cooling fan.

Note : For further details, refer to documentation.


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Indication

AIRCRAFT MANUFACTURERSUPPLY :

Installed in front of the main gearbox

Type :Air-oil cooler

Differential and thermostatic

Tota

Frsc

COOLINGFAN

A

OILCOOLER

OILCOOLER

Oiltank Scavenge

pumps

DIFFERENTIALAND THERMOSTATIC

BY-PASS VALVE

ENGINEAIRFRAME


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CENTRIFUGAL BREATHER

Function

The centrifugal breather separates the oil from the air/oilmist created by the oil system.

Position

- In the system : before the general vent line of the system.

- On the engine : it is formed by the starter/generator drivegear in the accessory gearbox.


- Type : centrifugal

- Air vent : through the rear part of the gear hollow shaft,connected to the exhaust.

Description

The centrifugal breather is formed by the starter-generatordrive gear. This gear is formed in one piece with a hollowshaft and has holes which provide a passage between thegearbox and the air vent.

The gear is supported by two ball bearings and has amagnetic carbon seal at each end.

Operation

The centrifugal breather is driven by the intermof the accessory drive.

When the engine is running the air/oil mist pathe breather :

- Centrifugal force throws the oil dropletsgearbox where they fall to the bottom of t

- The de-oiled air passes out through thegearbox passage, into an external pipe whicinto the exhaust.


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Oil droplets

Oil mist - from accessory gearbox

- from gas generator bearings- from power turbine bearings

- from reduction gearbox

STARTERDRIVE

Carbonseal

Bearing

STARTER-GENERATORDRIVE GEAR

Oil mist

De-oiled air

BREATHER

Type :Centrifugal

Air ventThrough the rear partf th h ll h ft


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ELECTRICAL MAGNETIC PLUGS

Function

The electrical magnetic plugs attract magnetic particles inthe oil system and provide a cockpit indication.

Position

- In the system : one electrical magnetic plug is located onthe reduction gearbox scavenge line, one on the accessorygearbox scavenge line and another one at the scavengepump outlet

- On the engine : one electrical magnetic plug is located atthe bottom of the reduction gearbox and another one atthe bottom of the accessory gearbox. These two electricalmagnetic plugs are mounted on the left or the right sideaccording to the position of the engine in the helicopter.A third electrical magnetic plug is located on the oilvalve assembly.


- Type : Magnetic with electrical indication

Self-sealing housing with strainer Optional chip pulse system.Quantity : 3

Description

An electrical magnetic plug comprises a mawhich has two parts which are electrically inone another and have a small gap between th

The plug is connected, via the engine electricathe aircraft instrument panel.

The plug is fitted into a housing which is proself-sealing valve and a mounting flange.

A bayonet type locking pin system ensures th

the electrical magnetic plug.The housings are bolted onto the oil valve assthe accessory gearbox and onto the reductcasing, where the scavenge oil can flow across tprobe.

Operation

The magnetic probe attracts magnetic particlthe oil.

If it attracts sufficient particles to form a bridggap, this will complete the electrical circuit two magnetic parts and thus provide indicaircraft instrument panel.

Note 1 : An optional chip pulse system mby the aircraft manufacturer. Thisto be burnt off.


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ELECTRICAL CONNECTOR(connection with the aircraft

instrument panel)

INSULATION

LOCKINGPINS

SELF-SEALINGHOUSING

SELF-SEALINGHOUSING

SELF-SEALINGHOUSING

MAGNETIC PROBEIN TWO PARTS

Type :- Magnetic with electrical indication- Self-sealing housing- Optional chip pulse system

Quantity :3

Indication :On the aircraft instrument panel

STRAINER

Oil valveassembly

Scavenge

pumps

ELECTRICAMAGNETIC PL


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SCAVENGE STRAINERS

Function

The strainers protect the scavenge pumps against largeparticles which might be in the oil.

Position

- In the system : they are fitted in each scavenge lineupstream of the scavenge pump

- On the engine : Two strainers are located on the accessory gearbox

casing (reduction gearbox and accessory gearboxscavenge)

One strainer is located on the oil valve assembly (gasgenerator rear bearing scavenge).

Main characteristics- Type : wide mesh filter

- Quantity : 3.

Description

Each strainer includes the following componmesh filter, a mounting flange and an O'ring

Operation

A strainer is a wide mesh filter which retaiparticles which may be present in the oil in ordthe scavenge pumps.

Note : The electrical magnetic plug, mounvalve assembly, is fitted with its ow


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Indication

WIDE MESHFILTER

O'RINGSEAL

MOUNTINGFLANGE

To scavengeTo oil cooler

ACCESSORY GEARBOX

AND REDUCTION GEARBOXSCAVENGE STRAINERS


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LOW OIL PRESSURE SWITCH

Function

The low oil pressure switch provides cockpit indication of low oil pressure.

Position

- In the system : downstream of the filter

- On the engine : mounted on the filter base.


- Type : diaphragm pressure switch

- Setting : 2C1 : 130 kPa (18.9 PSI) 2C2 : 170 kPa (24.65 PSI)

- Indication : light on instrument panel.

Description

The pressure switch comprises the following components :a mounting flange and an electrical connector (connectionwith the instrument panel).

The pressure switch is secured by means of two screwsonto the filter base.

Operation

The pressure switch microswitch is open duengine operation.

If the oil pressure reduces to less than the settithe diaphragm moves down. This causes tcontact to close, completing the circuit ofpressure warning light.


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LOW OIL PSWI

LOW OIL PRESSURESWITCH

Type :Diaphragm pressure swich

Setting :- 2C1 : 130 kPa (18.9 PSI)

- 2C2 : 170 kPa (24.65 PSI)

Indication :Light on instrument panel

Oil pressure

LOW OIL PRESSUR

SWITCH

O'RING

SEAL

MOUNTING FLANGE(secured by two screws

on the filter base)

ELECT(

the


OIL PRESSURE TRANSMITTER

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OIL PRESSURE TRANSMITTER

Function

The transmitter provides a signal of oil pressure.

Position

- In the system : in the supply system, downstream of thefilter after the restrictor.

- On the engine : mounted on the filter base.


- Supplied by the aircraft manufacturer

- Type : resistive

- Output signal : voltage proportional to the oil pressure

- Indication : on instrument panel.

Description

The transmitter includes :

- A mounting flange (mounting on the filte

- An electrical connector (connection with thpanel).

Operation

The transmitter incorporates a bridge of resion a flexible support.

The deformation of the support produces an ouproportional to the oil pressure for a constant in


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ELECTRICAL CONNE(connection with the instrument

MOUNTINGFLANGE

OIL

TRA

Oilpressure

AIRCRAFTMANUFACTURER SUPPLY

Type :Resistive

Output signal :Voltage proportional to

the oil pressure

Indication :

On instrument panel

OIL PRESSURETRANSMITTER


EXTERNAL OIL PIPES

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EXTERNAL OIL PIPES

This description deals with the external pipes of the oilsystem.

Function

The oil pipes ensure the oil circulation between the oilsystem components and the lubricated parts of the engine(bearings).


- Type of pipelines : rigid (one flexible)

- Type of union : flanged union.

Description

Lubrication

- Oil inlet (from oil tank to pressure pump ; aircraftmanufacturer supply)

- From pressure pump to filter base

- Supply of the gas generator front bearings

- Supply of the gas generator rear bearing.

Scavenge

- Scavenge of the gas generator rear bearing

- Scavenge of the power turbine bearings turbine to reduction gearbox ; flexible pip

Breathing

- Gas generator rear bearing (external pipe)

Air vent

- External pipe from centrifugal breather topipe.


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LUBRICATION PIPE

(from pressure pumpto filter base)

POWER TURBINE

BEARING SCAVENGE(flexible)

GAS GENERATORREAR BEARING

SUPPLY

REAR BEARINGSCAVENGE

Oil inlet

GAS GENERATOREAR BEARING

BREATHING

FRONT BEARINGSUPPLY

SUPPLY

SCAVENGEBREATHING

AIR VENT

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5 - AIR SYSTEM

- Air system (75-00-00) .................................................... 5.2

- Internal air system (75-00-00) ...................................... 5.4

- Air tappings (75-00-00) ................................................. 5.6

- Compressor bleed valve (75-31-00) .............................. 5.8- P3 pressure transmitter (75-41-00) .............................. 5.12

- Air tapping unions (75-00-00) ...................................... 5.14

- External air pipes (75-29-00) ........................................ 5.16 to 5


AIR SYSTEM

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AIR SYSTEM

Function

The engine air system includes :

- An internal air system which ensures : The pressurisation of the labyrinth seals The cooling of the engine internal parts The balance of forces on the rotating assemblies

- Air tappings which ensure : The air pressure measurement for the control system The start injector ventilation The aircraft air system supply The air for the bleed valve operation The air for the pressurisation of the power turbine

labyrinth seals.

- The compressor bleed valve.

Note : Refer to the various systems for the location, thecharacteristics, the description and operation.


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INTERNAL AIR SYSTEM- Pressurisation of labyrinth seals

- Cooling of internal parts- Balance of forces on the rotating assemblies

AIR TAPPINGS- Start injector ventilation

- Air pressure measurementfor the control system

- Aircraft air system supply- Bleed valve operation

- Pressurisation of the power turbine labyrinth seals

COMPRESSOR BLEEDVALVE


INTERNAL AIR SYSTEM

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INTERNAL AIR SYSTEM

FunctionThe internal air system pressurises the labyrinth seals,cools certain parts and provides a balancing of forces.

PositionAll the parts of the system are internal except thepressurisation of the power turbine labyrinth which issupplied by an external pipe.

Main characteristics- Type : air tapping with a calibrated flow- Air pressures used :

P2.4 : centrifugal compressor inlet pressure P2.6 : centrifugal compressor wheel outlet pressure P3 : centrifugal compressor outlet pressure.

Note : The internal air system is also referred to as thesecondary air system.

Functional descriptionThe internal air system can be considered in three parts :the front section, the gas generator HP section and thepower turbine section.

Front sectionAir tapped from the centrifugal compressor inlet is used topressurise the front bearing labyrinths. There is a very

small flow of air into the bearing chamber. Air tapped fromthe same point is discharged through the compressor bleedvalve mountedonthecompressorcasing(seecompressor

Gas generator HP section

Air tapped from the centrifugal compressodown the rear face of the compressor wheel,curvic-couplings, the hollow shaft and internIt is used to :

- Cool the rear face of the gas generator turbine (into the gas flow)

- Pressurise the labyrinth seal of the gas g

bearing (small flow into the bearing hous- Cool the front face of the power turbine (d

the gas flow).

The air from the centrifugal compressor through the hollow nozzle guide vanes and thin the shroud. It is used to cool the nozzle guithe front face of the gas generator turbine. A smof air is also used to cool the turbine shroud

The centrifugal compressor casing is fitted witpoints. This air is called clean air as it is out offlow stream.

Power turbine section

The air is tapped from the front face of thcompressor casing (clean air) and is taken by

pipe to the reduction gearbox casing. It then painternal passages to pressurise the labyrinthpower turbine shaft and to cool the rear face o


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INTERNAL AIR SYSTEM

FRONT SECTION GAS GENERATOR HP SECTION POW

Discharge of air(through compressor

bleed valve)

- Internal passages

Type :

Air pressure tapping witha calibrated flow

Air pressures used :- Centrifugal compressor inlet pressure- Centrifugal compressor wheel outlet pressure- Centrifugal compressor outlet pressure


AIR TAPPINGS

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AIR TAPPINGS

Function

Air tappings are used for :

- Fuel control

- Start injector ventilation

- Aircraft services

- Bleed valve operation- Pressurisation of the power turbine labyrinth seals.


- P3 air : 820 kPa (118.9 PSI) 2C1850 kPa (123.2 PSI) 2C2

- Air tapping limited by restrictors.

Functional description

Fuel control

A P3 pressure transmitter measures the centrifugalcompressor outlet air pressure.

A t0 temperature probe measures the air inlet temperature.

Start injector ventilation

Compressor delivery air is used to ventilinjectors to prevent carbonisation of unburnt

The system comprises a tapping union and a pipto the start electro-valve.

Aircraft services

Compressor delivery air is tapped off for usaircraft systems.

The engine has two air tapping unions (used foservices) located on the centrifugal compres

Note : The use of this bleed is restricted dand in single engine mode.

Bleed valve operation

Compressor delivery air is tapped to operate thebleed valve.

Pressurisation of the power turbine labyrinth

Refer to page 5.4.


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P0

ENGINEELECTRONIC

CONTROL UNIT

P3 PRESSURETRANSMITTER

Aircraft services

Bleed valve operation

Fuel control

Power turbine labyrinth seals

P3 air

P3 air :2C1 : 820 kPa (118.9 PSI) 2C2 : 850 kPa (123.2 PSI)

Air tapping limited


COMPRESSOR BLEED VALVE - GENERAL

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COMPRESSOR BLEED VALVE GENERAL

Function

The valve prevents compressor surge by bleeding off acertain quantity of air tapped from the axial compressoroutlet. When the valve is open, the discharge of air causesthe air flow through the axial compressor to increase thusmoving the operating line away from the surge line. Theoperation of this valve depends on the P3/P0 pressureratio.

Position

- In the system : between the axial and centrifugalcompressors

- On the engine : at the top of the counter casing.


- Type : pneumatic, butterfly valve

- Control : by P3/P0 pressure ratio.

Main components

- Pneumatic control system

- Butterfly valve

- Rack and pinion mechanism

- Air discharge duct

- Microswitch (connected to the EECU)- P2.4 air outlet

- P3 inlet filter.

Note : The air can be discharged under thorder to improve cooling ocompartment.


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Type :Pneumatic, butterfly valv

Control :By P3/P0 pressure ratio

AIRDISCHARGE DUCT

MICROSWITCH(connected to EECU)

RACK AND PINIONMECHANISM

BUTTERFLYVALVE

P3 INLETFILTER

P2.4

air outlet

P3 air

PNEUMATICCONTROL SYSTEM

COMPRESSIONRATIO P3/P0

COMPRESSOR FIELD DIAGR

Surgeline

Work(valve

Work(valv


COMPRESSOR BLEED VALVE - Operation

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DESCRIPTION - OPERATION

Description

The compressor bleed valve includes 3 main parts : thedetection capsule, the intermediate stage and the bleedvalve.

Detection capsule

It is subjected to P3/P0 pressure ratio and controls the air

discharge downstream of the calibrated orifice B.

It is fitted with a filter at the inlet.

Intermediate stage

It includes a diaphragm which is subjected to the pressuredownstream of B. The diaphragm controls the discharge

which determines the pressure downstream of the calibratedorifice A.

Bleed valve

It includes a spring loaded piston subjected to the pressuredownstream of restrictor A. The piston actuates the butterflyvalve by means of a rack and pinion mechanism.

It also includes a microswitch, operated by the piston,which sends a position signal to the EECU.

p

Open position

The P3/P0 pressure ratio is not sufficient tocapsules and there is an air discharge downscalibrated orifices. The piston is not actubutterfly valve is open.A certain amount of air, tapped from thcompressor inlet, is discharged overboard.The microswitch contact is closed and sesignal to the EECU.

Closed position

When the gas generator rotation speed N1 incompression ratio P3/P0 increases and beyovalue :

- The pressure becomes sufficient to deform tcapsule which closes the discharge

- The pressure downstream of the calibraincreases- The diaphragm of the intermediate stag

discharge- The pressure downstream of the calibrat

increases- The piston moves down under P3 pressur

the butterfly valve through the rackmechanism. The valve closes and stops th

The microswitch contact actuated by the pi


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A B

P2.4

P2.4

RACK

INDICATION

MICROSWITCH

P0 air

INTERMEDIATE

STAGE

Signal to the EECU

BUTTERFLYVALVE

PINION

PISTON


P3 PRESSURE TRANSMITTER

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Function

The P3 pressure transmitter senses the compressor outletair pressure and supplies a signal to the EECU.

Position

- In the system : connected to the EECU

- On the engine : on the ignition unit support.


- Type : resistive

- Output signal : voltage proportional to the air pressure

- Supply voltage : 10 VDC.

Description

The P3 pressure transmitter system comprises the P3tapping, an air pipe and the pressure transmitter.

The transmitter is secured on the ignition unit support by2 screws.

The electrical connector provides the connection with theEECU.

Operation

The transmitter produces an electrical voltage to the P3 air pressure.

The pressure signal is used by the EECU for en(fuel flow limit, surge control).

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AIR TAPPING UNIONS

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Function

The air tapping unions allow air to be tapped from thecentrifugal compressor outlet.

Position

They are located on the centrifugal compressor casingfront face. The air in this zone is considered clean air as itis out of the main air stream and thus contains very littledebris.


At 100 % N1, in standard conditions :

- Air pressure : 820 kPa (118.9 PSI) 2C1850 kPa (123.2 PSI) 2C2

- Air temperature : 335 C (635 F).

Functional description

Start injector ventilation

Standard union.

Air flow : very low.

Power turbine labyrinth pressurisation

Standard union.

Air flow : very low.

P3 pressure transmitter

Standard union.

Air flow : nil.Aircraft services

Standard union.

Max air flow : 100 g/s (0.22 lb/sec.).

Note : P3 air tapping is automatically cugiven N1 (A/C control).

Compressor bleed valve

Standard union.

Air flow : negligible.


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At 100 % N1,in standard conditions

Air pressure :2C1 : 820 kPa (118.9 PSI) 2C2 : 850 kPa (123.2 PSI)

START INJECTORVENTILATION

Standard unionAir flow : very low

POWER TURBINELABYRINTH PRESSURISATION

Standard unionAir flow : very low

AIRCRA

StandMax air flow : 10

P3 PRESSURETRANSMITTER

Standard unionAir flow : nil

COMPRESSO

StanAir flow


EXTERNAL AIR PIPES

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This part considers the external air pipes of the air system.

Function

The air pipes ensure the air supply from/to the varioussystem components.


- Type : rigid, stainless steel

- Unions : standard (connecting flange with bolts).

Description of the pipes

The air system uses the following external pipes :

- P3 air pipe for the control of the compressor bleed valve

- Air pipe for the ventilation of the start injectors

- Air pipe to supply the P3 pressure transmitter

- Air pipe for the pressurisation of the power turbinelabyrinth.


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BLEED VALVECONTROL

VENTILATION OSTART INJECT

Type of pipes :Rigid, stainless steel

Type of unions :Standard (connecting

flange with bolts)

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6 - FUEL SYSTEM- Fuel system (73-00-00) ........................................... 6.2- Pump and metering unit assembly (73-23-00)..... 6.16

Fuel pumps (73-23-00) .................................. 6.18 Start purge valve (73-23-00) ......................... 6.22 Metering unit (73-23-00) ............................... 6.24

- Fuel filter (73-23-11) .............................................. 6.30- Fuel filter pre-blockage pressure switch (73-23-32) 6.36- Fuel filter blockage indicator (73-23-31) ............. 6.38- Low fuel pressure switch (73-23-33)..................... 6.40- Fuel valve assembly (73-14-00) ............................. 6.42- Main injection system (72-00-43) ......................... 6.46- Engine fuel inlet union (72-43-00) ........................ 6.48

- Start injectors (72-43-00) ...................................... 6.50Combustion chamber drain valve (71 71 00) 6 54


FUEL SYSTEM - GENERAL

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Main components

- Pump and metering unit assembly LP pump Filter HP pump Metering unit.

- Fuel valve assembly

- Fuel injection system.

Function

The fuel system ensures fuel supply, distribution, control,metering and injection.

Position

All the system components are mounted on the engineexcept the EECU.


- Supply by the aircraft system and the engine pumps

- Centrifugal main injection and start injection by injectors

- Automatic back-up control (optional on 2C1)

- Fuel control : digital control unit controlling a meteringdevice.


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P3 N1

N1

FUEL VALVEASSEMBLY

PUMP ANDMETERING UNITASSEMBLY

SENSORS

HP PUMP

FILTER

LP PUMP

METERINGUNIT

FUEL INJESYSTE

ENGINEELECTRONIC

CONTROL UNIT

- air- en

- centrifug- start injec

bac(opt

Fu

Digitcontrolling

AUTOMATICBACK-UP CONTROL


FUEL SYSTEM - DESCRIPTION

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This part shows the main components of the fuel system.

Low pressure pump (LP)Centrifugal type pump which gives an initial pressure rise.

Oil - fuel heat exchanger (oil filter)

Filter

Fitted between the LP and HP pumps, this filter has ablockage indicator and a by-pass valve.

Start purge valve

To eliminate air from the system before start.

Fuel filter pre-blockage pressure switch

Provides a cockpit indication of the onset of the filterblockage.

Low fuel pressure switch

Sensing the filter outlet pressure, it gives a cockpit indicationof system low pressure.

High pressure pump (HP)

Metering unit- Normal control (stepper motor, resolver, mete

constant P valve)- Automatic back-up control : by-pass valve

(the actuator is supplied by the aircraft ma

Additional check valve

The valve permits the correct operation of thevalve in low fuel flow conditions (particustarting).

Fuel valve assembly- Start electro-valve- Stop electro-valve- Pressurising valve

- Stop purge valve.

Fuel injection system- Start injectors (2)- Main injection (centrifugal wheel)- Engine fuel inlet union- Combustion chamber drain valve.

Note : A fuel flowmeter, supplied bmanufacturer canbefittedbetween


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Constant P valve

Metering needle(with resolver and

stepper motor)Automatic

back-up control

ADDITIONALCHECK VALVE

Pressurva

Stoppurge valve

PUMP ANDMETERING UNIT

ASSEMBLY

HP PUMPFuel inlet

Purge (to tank)

LOW FUEL

FUEL FILTER(with by-pass valve

and blockage indicator)

OIL - FUEL HEATEXCHANGER

(oil filter)

Blockageindicator

START PURGE

Normalcontrol

FUEL FILTERPRE-BLOCKAGE

PRESSURE SWITCH

LP PUMP

Startelectro-valve

Stopelectro-valve

Engifuel inlet u

Purge (to tank)

FUEL VALVE

ASSEMBLY


FUEL SYSTEM - OPERATION (1)

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This part deals with the following operating phases : pre-start, purge, starting, normal running, automatic back-up

control and shut-down.

Pre-start

- The LP and HP pumps do not operate and there is nopressure in the system

- The constant P valve is closed

- The stop electro-valve is closed

- The pressurising valve is closed

- The additional check valve is closed

- The start purge valve is closed

- The stop purge valve is closed

- The start electro-valve is in the ventilation position (noelectrical supply)

- The combustion chamber drain valve is open.

At power-up the metering needle is set to a "basic" fuelflow position in order to ensure a correct ignition in thecombustion chamber.


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CONSTANT P VALVE

(closed)


(closed)

STOPPURGE VALVE

(closed)

STARTELECTRO-VALVE

(in ventilation position)

COM

STOPELECTRO-VAL

(closed)

STARTLP PUMP HP PUMP

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BOOSTER PUMP PRESSURE

START PURGEHP PUMPFuel inlet

Purge (to tank)

LP PUMP

(stopped)

Restrictor



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Starting

When start is selected, the start accessories are electricallysupplied.

The pumps are driven at a speed proportional to N1. Firstthey supply the start injectors and then the centrifugalinjection wheel.

The start purge valve closes.

The constant P valve operates and returns the excess fuelto the LP pump outlet.

The additional check valve ensures the operation of theconstant P valve when the HP pump pressure is very low.It increases the HP fuel pressure during starting, particularlyat altitude.

The fuel flow is metered by the metering unit according tocontrol laws determined by the Engine Electronic ControlUnit.

At the end of starting, the start accessories are de-energisedand the start injectors are ventilated by P3 air pressure.

The gas generator rotation speed is stabilised at a controlled

value.Note : Thecombustionchamberdrainvalveclosesduring


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START PURGEHP PUMPF l i l t

LP PUMP(driven)


LOW PRESSUREHIGH PRESSURE

METERED FUEL

CONSTANT P VALVE(in control)


(open)

PRESSURISINGVALVE(open)

STARTELECTRO-V(electrically sup

STOPELECTRO-VALVE

(electrically supplied)

Restrictor

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LP PUMP(driven)


LOW PRESSURE

HIGH PRESSURE

METERED FUEL

CONSTANT

P VALVE(in control)


(open)

PRESSURISINGVALVE

(open)

STARTELECTRO-VALV

(ventilation position

AUTOMATIC BACK-UPCONTROL

P3 AIR

The automatic back-up control providesa back-up control of the fuel in case of amain control system failure.

Restrictor



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Shut-down

The engine stop command electrically supplies the stopelectro-valve and the stepper motor to close the meteringneedle.

The fuel supply to the injection wheel is cut and the enginestops.

The stop purge valve opens briefly to drain the fuel from

the injection line to the tank.

Note : The electrical signal to the stepper motor is delayed in order to detect a failure to close of the stop valve.


STOP STOP

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HP PUMP

LP PUMP(stopped)


(closed)

PURGE VALVE(open)

Momentary purge (to tank)

ELECTRO-VALV(electrically supplie

The electrical signal to the stepper motor is

Restrictor


PUMP AND METERING UNIT ASSEMBLY -GENERAL

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Function

The pump and metering unit assembly ensures fuel supplyand fuel flow metering.

Position

- In the system : before the fuel valve assembly

- On the engine : on the left front face of the accessorygearbox.


- Mounting : clamping ring

- Replaceable components (LRUs):

Filter Pre-blockage pressure switch Low fuel pressure switch Fuel filter blockage indicator.

Main components

- LP pump

- Filter

- Pre-blockage pressure switch

- Blockage indicator

- Low fuel pressure switch

- Start purge valve

- HP pump

- Constant P valve

- Metering unit

- Additional check valve.


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METERINGUNIT

Mounting :Clamping ring

Replaceable components :Filter

Pre-blockage pressure switchLow fuel pressure switch

Fuel filter b lockage indicator

CONSTANT P VALVE

To HP pump inlet

Heat exchanger

LP PUMP

HP PUMP

PRE-BLOCKAGEPRESSURE SWITCH

BLOCKAGEINDICATOR

LOW FUELPRESSURE SWITCH

STARTPURGE VALVE

FILTER

FILTER

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HP FUEL PUMP

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Fuel inlet (from aircraft fuel system)

Ejector Impeller

Drive geDriven gear

HP FUEL PUMP

LP FUEL PUMP

HP PUMP

PRESSURERELIEF VALVE

Heat exchanger

(oil filter)

LP PUMFuel inlet

Filter

Type :LP pump : centrifugal type

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PUMP AND METERING UNIT ASSEMBLY -START PURGE VALVE

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Function

The start purge valve permits a purge of air from the fuelsystem before engine start.

Position

- In the system : between the filter and the return line to thefuel tank

- On the engine : on the upper part of the pump andmetering unit assembly.


- Type : ball valve controlled by a piston and a spring.

Main components- Valve

- Piston

- Spring.

Functionnal description

When the aircraft booster pump is switchesupplied to the engine. It passes through the Lfilter and passes out through the start purge vthe tank.

As soon as engine start is selected HP pump pon the piston to close the start purge valve.


Purge

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START

PURGE VALVE

SPRING PISTONVALVE

Frommete

Low pressure

STARTPURGE VALVE

(open)

FUEL SYSTEMPURGE

NORMAOPERATIO

HP pump(engine stopped)

Booster pump

pressure

Purge (to tank)

STARTPURGE VALVE

(closed)

HP pump(engine running)

Low pressure

Purge (to tank)

STARTPURGE VALVE

From fuel filter


PUMP AND METERING UNIT ASSEMBLY -METERING UNIT - GENERAL - DESCRIPTION

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FunctionThe metering unit controls the fuel flow in normal mode inresponse to signals from the EECU.

It also provides fuel flow control in automatic back-upmode.

Position- In the system : downstream of the HP pump

- On the engine : at the front part of the pump and meteringunit assembly.


- Normal flow control by an electrical actuator (Dualstepper motor) driving a metering needle

- Back-up flow control by an automatic unit.

Main components- Actuator and metering needle (normal con

- Actuator (aircraft manufacturer supply) valve (automatic back-up control)

- Metering needle position transmitter (nor

- Constant P valve (common)

- Additional check valve (common).

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NORMAL CONTROL ADDITIONALPOSITION

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Fuel return to HP pump

inlet

To fuel valve assembly

CONSTANT P VALVE

METERING NEEDLE CHECK VALVETRANSMITTER

DUALSTEPPERMOTOR

Fuel inlet

CON

+ -

METERING NEEDLEPOSITION

TRANSMITTER(to EECU)

DUALSTEPPERMOTOR

EECU

ELECTRICALCONTROL UNIT

(EBCAU)

ADDITIOCHECK VA

NORMAL CONTROLMETERING NEEDLE

N1 otherengine


PUMP AND METERING UNIT ASSEMBLY -METERING UNIT - OPERATION (2)

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Automatic back-up control system (optional on2C1)

This system comprises an electrical actuator (aircraftmanufacturer supply), fitted on the pump and meteringunit assembly, which operates a back-up by-pass valve.The actuator is electrically controlled by an electricalcontrol unit (EBCAU) located in the aircraft.

In the unlikely event of a total EECU failure, the steppermotor will be frozen and the automatic back-up controlsystem will automatically match both N1 speeds in orderto maintain N2 speed at 100 %. To do so the EBCAUreceives a signal of N1 from the other engine.

If an N1 increase is needed, the control unit will commandthe actuator to open the by-pass thus increasing the fuelflow passing through the back-up by-pass valve.

If an N1 decrease is needed, the control unit will commandthe actuator to rotate in the opposite direction. This willreduce the flow to the main metering needle withoutopening the by-pass.

The rate of engine acceleration and deceleration is a

function of the speed of movement of the actuator whichis designed to avoid the possibility of surge or flame-out.

Note 1 : The electrical control unit (EBC Back-up Control Auxiliary Unit) anare aircraft manufacturer supplie

Note 2 : There is a microswitch on the a provides a neutral position indica EECU. At power-up the EECU

initialises the EBCAU to the neunecessary.

Note 3 : In the case of EBCAU operation, N1s are displayed separately(Caution Advisory Display) screen


AUTOMATIC ADDITIONAL

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Fuel return to HP pump

inlet

To fuel valve assembly

CONSTANT P VALVE

BACK-UP CONTROL CHECK VALVE

METERING NEEDLEPOSITION

TRANSMITTER(to EECU)

Fuel

NEUTRAL

POSITIONMICROSWITCH

ELECTRICAL

ACTUATOR

Fuel inlet

AUTOCON

(op

DUALSTEPPERMOTOR

EECU

ELECTRICALCONTROL UNIT

(EBCAU)

Fuel

+-

ADDICHECK

NORMAL CONTROLMETERING NEEDLE

ENGINEAIRFRAME

N1 otherengine

P

- +N

Back-up flow chartas a function of the

metering needleposition ( ) when frozen,at the moment of failure.

Fuelflow

Max

flow

Min flowstop (antiflame-out)

Neutral position

FUEL METERING IN


FUEL FILTER - GENERAL

F ti M i t

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Function

The filter retains any particles that may be in the fuel inorder to protect the metering unit components.

Position

- In the system : between the LP and HP pumps

- On the engine : on top of the pump and metering unit

assembly.


- Type : fibre glass cartridge

- Filtering ability : 20 microns

- By-pass valve setting : P 120 kPa (17.4 PSID)

- Pre-blockage pressure switch setting : P 70 kPa(10.2 PSID).

Main components

- Filter

- Blockage indicator

- By-pass valve

- Pre-blockage pressure switch.


T

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Type :Fibre glass cartridge

Filtering ability :20 microns

By-pass valve setting : P 120 kPa (17.4 PSID)

Pre-blockage setting : P 70 kPa (10.2 PSID)

Low pressure

Pre-blocpressure sw

Blockageindicator

FUELFILTER

BY-PASSVALVE

Blockageindicator

FUELFILTER

To start purge valve Pre-blockage

pressure switch


FUEL FILTER - DESCRIPTION

The assembly comprises the housing, the filtering element,

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y p g, g ,the by-pass valve, the pre-blockage pressure switch and

the blockage indicator.

Filtering element

It is a fibre glass cartridge with a filtering ability of 20microns.

O'ring seals ensure the sealing between the cartridge andthe filter housing.

The filter cover is fitted with a purge outlet union.

By-pass valve

This valve ensures a fuel flow to the metering unit in theevent of filter blockage. It is subjected on one side to filterupstream pressure and on the other side to downstreampressure plus the force of a spring.

Note : The by-pass valve is fitted inside the pump and metering unit assembly body.


FILTERING ELEMENT

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FILTERING ELEMENT(20 micron fibre glass filter)

FIL(20 mi

O'RINGSEALS

FILTERHOUSING

To start purge valve

COVER

BY-PASSVALVE


FUEL FILTER - OPERATION

The operation is considered in normal operation, pre- Blockage

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p p pblockage and blockage.

Normal operation

The fuel provided by the LP fuel pump enters the fuel filterand flows through the filtering element (from outside toinside).

The filtering element retains particles larger than 20

microns. The fuel then flows to the HP pump.

Note : Before entering the fuel filter, the fuel passesthrough the heat exchanger formed by the oil filter housing.

Pre-blockageWhen the filter becomes dirty, the pressure differenceacross the filtering element increases.

If the pressure difference becomes higher than the pre-blockage pressure switch setting, the electrical contact of the pressure switch closes and supplies the "fuel filter pre-blockage" indication in the cockpit.

g

When the pressure difference across the filterexceeds the by-pass valve setting, the by-passand causes :

- The red indicator to pop out

- The fuel flow to by-pass the filter.

Note : Refer to the following pages for the pressure switch operation.


OPERATION OF THE FUEL FILTER

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FILTERBLOCKAGE

ONSET

The pre-blockagelight illuminates(cockpit)

FromLP pump To HP pump

FILTERING ELEMENTOPERATION(20 microns)

BLOCKAGEINDICATOR OPERATION

(the red visualindicator appears)

FromLP pump To HP pump

PRE-BLOCKAGE PRESSURE SWITCH P : 70 kPa (10.2 PSID)

PRE-BLOCKAGE

OBY

P : 12

FromLP pump

FILTERBLOCKED


FUEL FILTER PRE-BLOCKAGE PRESSURESWITCH

Description

The pre-blockage pressure switch includes th

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Function

The pre-blockage pressure switch provides an indicationof the onset of filter blockage.

Position

- In the system : between the fuel inlet and outlet of thefilter

- On the engine : on the pump and metering unit assemblybeside the fuel filter.


- Type : differential pressure switch

- Setting : P 70 kPa (10.2 PSID)

- Indication : light in the cockpit.

components :

- The pressure switch body which houses contact

- The mounting flange : the pre-blockage preis secured by two screws on the pump and massembly

- Electrical connector (connected to an indicthe cockpit).

Two O'ring seals ensure the sealing betwblockage pressure switch and the pump and massembly body.

Operation

Normal operation

The filtering element is clean. The pressure deach side of the filtering unit is lower tblockage pressure switch setting : the electricopen and there is no indication.

Filter pre-blockage

When the filtering unit becomes dirty, difference across the filter increases. When differenceexceedsthepressureswitchsettingt


Type :

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MOUNTINGFLANGE

O'ring

seals

ypDifferential pressure switch

Setting : P 70 kPa (10.2 PSID)

Indication :Light in the cockpit

Fuelfilter

To HP pump

Low pressure

Low pressure

Fuel pressure

Fuelfilter

Pre-blockage light(cockpit)

PRE-BLOCKAGEPRESSURE SWITCH


FUEL FILTER BLOCKAGE INDICATOR

Function Operation

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Function

The blockage indicator provides a visual indication of filter blockage.

Position

- In the system : between the fuel inlet and outlet of thefilter

- On the engine : on the pump and metering unit assemblybeside the fuel filter.


- Type : differential pressure, magnetic arming device

- Setting : P 120 kPa (17.4 PSID)

- Indication : red indicator.

Decription

The indicator comprises :

- A body with a mounting flange

- A red indicatorA bl ( l )

Operation

Normal operation

The filtering element is clean. The pressure deach side of the filter is lower than the blockasetting : the indicator doesn't protrude (arme

Filter blockage

When the filter becomes dirty, the pressurincreases.

When the pressure difference exceeds tindicator setting it causes the by-pass valve to indicator to pop out.

Note : The indicator is reset, after the recover by pushing it back into its ho


RED INDICATOR(magnetic) TType :

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MOUNTINGFLANGE

(magnetic) T

Upstream pressure

Downstream pressure

Type :Differential pressure,

magnetic arming device

Setting : P 120 kPa (17.4 PSID)

Indication:Red indicator

BLOCKAGEINDICATOR To HP pump

Low pressure

Low pressure

Filter

BLOCKAGEINDICATOR

Fuelfilter


LOW FUEL PRESSURE SWITCH

Function Description

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Function

The low fuel pressure switch detects low pressure at the LPpump outlet.

Position

- In the system : upstream of the HP pump

- On the engine : on the pump and metering unit assembly

front face above the LP pump.


- Type : diaphragm

- Setting : 60 kPa (8.7 PSI)

- Indication : light on the instrument panel.

p

The pressure switch includes :- A fuel inlet orifice

- A diaphragm and a microswitch

- An electrical connector (connection with thpanel).

The low fuel pressure switch is secured by 2 scpump and metering unit assembly front face

Operation

Normal engine running

In normal operation the fuel pressure is suffithe electrical contact open.

The warning light on the instrument panel is ex

Low pressure operation

If the fuel filter downstream pressure droppressure switch setting, the electrical contaccompletes the circuit to the low fuel pressure w


MOUNTINGFuel

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Type :Diaphragm

Setting :60 kPa (8.7 PSI)

Indication :

Light on the instrument panel

PRESSURSWITC

FLANGE

LOW FUELPRESSURE SWITCH

LOW FUELPRESSURE SWI

ELECT(

the

pressure

To

From LP pump

HP pumpLP pump

Lo

(in


FUEL VALVE ASSEMBLY - GENERAL -DESCRIPTION

Description

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Function

The fuel valve assembly distributes the fuel to the injectionsystem.

Position

- In the system : between the metering unit and theinjection system

- On the engine : on a support at the upper part of thecentrifugal compressor casing.


- Assembly which comprises electro-valves andhydromechanical valves

- Pressurising valve setting : 300 kPa (43.5 PSI)

- Stop purge valve setting : 1300 kPa (188.5 PSI).

p

This assembly includes the start electro-vaelectro-valve, the pressurising valve and thvalve (injection wheel purge).

Start electro-valve

This valve allows either fuel or air to flowinjectors. It is a 3-way, mono-stable valve. It solenoid which controls a double valve. Thare : the fuel inlet, the air inlet and the injectors.

Stop electro-valve

This valve controls the fuel flow to the injectiois a bi-stable type valve and consists of a solencoils (open and close) and a two position va

Pressurising valve

During starting it ensures priority of flowinjectors. It is a ball valve which is spring-lo

Stop purge valve

It is a ball valve which is spring loaded closed. centrifugal injection wheel during engine sprevent carbonisation of residual fuel.


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Fuel valve assembly :- Electro-valves

- Hydromechanical valves

Pressurising valve setting :300 kPa (43.5 PSI)

Stop purge valve setting :1300 kPa (188.5 PSI)

PRESSURISINGVALVE

STARTELECTRO-VALVE

FUEL VALVEASSEMBLY

STOPPURGE VALVE

STARTELECTRO VALVE

From metering unit

Purge

(to tank)

PRESSUVA

STOPELECTRO-VALVE


FUEL VALVE ASSEMBLY - OPERATION

The following phases are considered : starting, normalr nning and sh t do n

Shut-down - Injection wheel purge

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running and shut-down.

Starting

When start is selected, the start electro-valve is electricallysupplied. The double valve opens the fuel supply to thestart injectors. At the same time the stop electro-valve isenergised to the open position to admit the fuel flow fromthe metering unit.

When there is sufficient fuel pressure (300 kPa / 43.5 PSI),the pressurising valve opens and fuel flows to the centrifugalinjection wheel.

When the engine reaches self-sustaining speed (approx.45 % N1) the electrical supply to the start electro-valve iscut. The valve moves across under spring pressure, closingthe fuel supply and opening the P3 air supply to ventilate

the injectors.

Normal running

In this condition the fuel is supplied to the centrifugalinjection wheel and the start injectors are still ventilatedwith P3 air.

When shut-down is selected the closing coielectro-valve is supplied. The valve closes anfurther supply to the injection system. The valve closes and the engine begins to runsudden but brief pressure rise, upstream of the svalve, causes the purge valve to open againsThis allows combustion chamber air pressureresidual fuel from the centrifugal injection wline. This prevents carbonisation of the residuamight cause the blockage of the injection s17 cc). The fuel is returned to the fuel tank.

As the fuel pressure decreases, the purge under the action of its spring.


Stoppurge Pressurising

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valve

Startelectro-valve

gvalve

Fuelinjectionsystem

Stopelectro-valve

INITIAL PHASE OF STARTING ACCELERATIONENGINE STOPPED

P3 P3


MAIN INJECTION SYSTEM

Function Internal supply pipe

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The injection system sprays fuel into the combustionchamber to give stable and efficient combustion.

Position

- In the system : downstream of the fuel valve assembly

- On the engine : inside the combustion chamber. The

injection wheel is mounted between the centrifugalcompressor and the turbine shaft.


- Type : centrifugal injection

- Radial fuel supply.

Description

The main injection system comprises the engine fuel inletunion, the internal supply pipe and the centrifugal injectionassembly.

Engine fuel inlet union

Fitted at the lower right front face of the compressorcasing it has a restrictor and a leak test plug

This pipe connects the inlet union to the fueCentrifugal injection assembly

This assembly consists of a stationary distriinjection wheel. The distributor is drilled withdeliver the fuel to the wheel. The injection whebetween the compressor and the turbine shawith holes which form the fuel spraying between the distributor and the wheel is pressurised labyrinth seals.

Operation

As the injection wheel is rotating at high spfuel is centrifuged out through the radial sprayed between the two swirl plates.

It should be noted that the injection pressure isthe centrifugal force and therefore the fuel systrequire very high pressures.

The injection wheel fuel chamber is sealed bylabyrinth seals. There is a small air flow chamber. During shut-down the fuel rema

system is purged via the fuel valve assembly


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Type :Centrifugal injection,

radial fuel supply

CENTRIFUGALINJECTION WHEEL(with spraying jets)

INTERNALSUPPLY PIPE

ENGINE FUELINLET UNION


DISTRIBUTORFuel inlet

DISTRIBUTOR

Leak testplugRestrictor

Pressurisingvalve

CENTRIFUGALINJECTION WHEELFrom

metering unit

To stop purge valve


ENGINE FUEL INLET UNION

Function Operation

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The engine fuel inlet union ensures transfer of the fuelfrom the external pipe to the internal supply pipe.

Position

- In the system : downstream of the pressurising valve

- On the engine : it is fitted at the lower right front face of

the compressor casing.

Main components

The device comprises :

- A body with a mounting flange and an internal restrictor

- A leak test plug

- Seals (O'rings and copper seal).

The engine fuel inlet union ensurebetween the external and internal fuel ductsinjection system.

The restrictor is used to increase the pressure thus to improve the pump and massembly P valve operation.

The leak test plug helps to check the internunion (there should not be any leak).


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Internalsupply pipe


Distributor

Fuel inlet

From metering unit

P3

Leak testplug CoppersealRestrictor O'ringseals

FUEL VALVEASSEMBLY


START INJECTORS - GENERAL

Function Main components

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The two start injectors spray fuel into the combustionchamber during engine starting.

Position

- In the system : downstream of the start electro-valve

- On the engine : on the upper half of the turbine casing at

2 o'clock and 10 o'clock - They penetrate into the mixer unit.


- Type : simple injector

- Quantity : 2

- Ventilation : by air flow.

- Mounting flange- Fuel inlet union

- Injector body

- Spraying jet.


MOUNTINGFLANGE

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STARTINJECTOR

Startelectro-valve

From metering unit

Type :Simple injector

Quantity :2

Ventilation :By air flow

SPRAYINGJET

INJECTOR


START INJECTORS - DESCRIPTION -OPERATION

D i ti Operation

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Description

The start injectors are mounted on the upper part of theturbine casing. They penetrate into the combustion chamberthrough holes in the mixer unit.

They are secured by two bolts onto bosses with seals andspacers to prevent leaks and adjust the depth of penetrationinto the combustion chamber.

Injector components

- Injector body with mounting flange

- Fuel inlet (threaded to receive a union)

- Spacers and seals (depth adjustment)

- Mounting flange (secured by 2 bolts)

- Filter

- Nut

- Jet

- Shroud.

Operation

Starting

During starting the injectors are supplied wi

The fuel is atomised and is ignited by the spaigniter plugs. The flame thus produced, ignsprayed by the centrifugal injection wheel.

Normal running (N1 > 45 %)

When the engine reaches self-sustaining sp45 %) the fuel supply to the injectors is shut

P3 air is then blown through the injectcarbonisation of the residual fuel.

It should be noted that ventilation is continengine running.


F

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From

metering unit

From metering unit

Startelectro-valve

Startelectro-valve

P3

FILTER

JET

SPACERS ANDSEALS

SHROUD

NUT

Fuel inlet

MOUNTING FLANGE(mounting with two bolts)

INJECTOR

STARTING


COMBUSTION CHAMBER DRAIN VALVE

Function Operation

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The valve drains overboard any unburnt fuel remaining inthe combustion chamber.

Position

- On the engine : at the bottom of the turbine casing.


- Type : piston valve

- Setting : closing threshold as a function of N1 and P0.

Description

The drain valve includes the following components :

- A mounting flange (secured by two bolts on a mountingpad located at the bottom of the turbine casing)

- A piston valve held open by a spring

- An outlet union which connects to the drain system.

The valve has two positions : open and clos

Open position

When the engine is not running and at the start, the valve is held open by the action of

Any unburnt fuel in the combustion chambthrough the valve overboard to the drain

ensures that no fuel accumulates in the combustwhich could cause starting problovertemperature).

Closed position

As the engine starts the combustion chamincreases. This pressure is felt on the upper s

valve which moves down to close the drain.The valve closes during starting when the presa given threshold as a function of N1 and P0

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EXTERNAL FUEL PIPES

Function

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The fuel pipes ensure the circulation of fuel between thecomponents of the system.


- Type : rigid, stainless steel.

Main pipes

- From LP pump to oil filter (heat exchanger)

- From oil filter to fuel filter

- From pump and metering unit assembly to valve assembly

- From valve assembly to start injectors (x2)

- From valve assembly and pump and metering unitassembly to tank (injection wheel and start purge valve)

- From valve assembly to injection wheel.


LP PUMP / VALVE ASSEMBLY /Flowmeter

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OIL FILTER(heat exchanger)

LEFT START INJECTOR

OIL FILTER /

FUEL FILTER

PUMP AND METERING

UNIT ASSEMBLY /VALVE ASSEMBLY

VALVE ASSEMBLY /RIGHT START INJECTOR

VALVE ASSEMETERING

COMBUSTIONCHAMBER DRAIN

VI

(optional)

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7 - CONTROL SYSTEM- Control system ............................................................... 7.2

General ................................................................... 7.2 Description .............................................................. 7.4 Operation ............................................................... 7.8 Indication and monitoring .................................... 7.34

- Fault tolerance tables ......................................... 7.38

- Engine Electronic Control Unit (73-21-00) ................. 7.44 General .................................................................... 7.44

Functional description ........................................... 7.46 to 7


Main components

CONTROL SYSTEM - GENERAL

Functions

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- Engine Electronic Control Unit- Engine (engine and systems)

- Aircraft : various systems (control, indica

The system is designed to adapt the engine to the aircraftpower requirements whilst remaining within defined limits.

The main functions are :

- Starting

- Speed control

- Various limits

- Automatic back-up control

- Overspeed protection

- System monitoring and fault management.

Main characteristics- Dual channel digital electronic control system


- Redundant electrical supply (from the aircraft and fromthe engine alternator).


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ENGINE EL

CONTR(EE

AIRCRAFT(various systems)

ENGINE

MAIN FUNCTIONS

- Starting

- Speed control

- Various limits


- Overspeed protection

- System monitoring and fault management


CONTROL SYSTEM - DESCRIPTION (1)

The complete system includes aircraft components, enginecomponents and the EECU.

- Electrical components : Control sensors

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Aircraft components

- Switches, buttons, etc. (logic and analog signals)

- Indicators, warning lights, etc.

- EECU power supply

- Start and stop selection logic.

Engine components

- Hydromechanical components : LP pump Filter HP pump Metering unit (with optional automatic back-up

control) Check valve Start injectors Main injection system

Indication sensors Dedicated alternator Resolver Stepper motor Stop electro-valve Start electro-valve Neutral position switch

Ignition unit Starter EBCAU back-up control unit (fitted in

Note : EBCAU = Engine Back up Control A

Engine Electronic Control Unit (EECU

Computer which controls and monitors the e

- Digital type, dual channel

- Mounted in the aircraft

- Digital power turbine overspeed protectio

- One EECU per engine with cross monitor


A/C START AND STOP LOGICA/C 28 VDC

SUPPLYA/C CONTROLS AND

INSTRUMENTS

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EBCAU

Firewall

CHANNEL BCHANNEL A

INDICATIONSENSORS

F i l t e r p r e - b

l o c

k a g e

S t a r t c o n

t r o

l

S t o p

S t a r t

L o w

f u e

l p r e s s u r e

EECU

CONTROLSENSORS IG

LPPUMP

STOPELECTRO-VALVE

PRESSUVA

FILTERHP

PUMP METERING UNIT

STARTELECTRO-VALVE

BACK-UPELECTRICALACTUATOR

A B

ALTERNATOR

STEPPERMOTOR A

STEPPERMOTOR B

N e u

t r a

l p o s

i t i o n

RESOLVER

Fuel inlet

ENGINE

AIRCRAFT

PUMP METERING UNIT ASSEMBLY


CONTROL SYSTEM - DESCRIPTION (2)

The EECU has two independent channels A and B. Bothchannels have the same software.

Channel selection

A channel selector in the EECU will select wh

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Analog inputs

The two channels receive the following analog inputs : P3,t4.5, resolver position,Tq, N2 trim, P0, t0, collective pitchand conformation resistances Tq and t4.5.

The inputs are shared between the two channels. The N1and N2 inputs are independent for each channel.

There is a data link between the two channels.

This configuration ensures that if all the acquisitions onone channel fail the acquisitions of the other channel aresufficient to control the engine safely.

Discrete inputs and outputs

The discrete inputs are received and shared by the twochannels and the discrete outputs are controlled by theselected channel. The resources of each channel receivetheir power supply from the corresponding channel. Theshared resources receive their power supply from bothchannels.

A channel selector in the EECU will select whwill control the engine depending on the signafrom the two channels. The normal channel isthe system changes automatically to channel

If both channels are unable to control the engstepper motor is frozen.


POWER SUPPLY

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INTER CHANNELDATA LINK

SPEEDMEASUREMENTN1, N2ANALOG

INPUTSCHANNEL A

ANALOGINPUTS

CHANNEL B

DISCRETEINPUTS

CHANNEL SELECTIONLOGIC

SPEEDMEASUREMENT

N1, N2

CHANNEL A

POWER SUPPLYCHANNEL B

CHANNEL A

CHANNEL B


CONTROL SYSTEM - OPERATION (1)

Main functions of the control system

Overspeed

This function causes the engine to automadown in the event of power turbine overspee

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Each channel of the control system can ensure the followingfunctions : starting, speed control, back-up control,overspeed, monitoring and maintenance aid.

Starting

This function guarantees a quick and safe start under alloperating conditions :

- Sequential control- Control of the fuel flow required to start.

Speed control

This function maintains the aircraft rotor rotation speedalmost constant in all operating conditions.

It also protects the engine with various limitations: rotation

speeds, acceleration, deceleration, fuel flowAutomatic back-up control

The control system is a FADEC and therefore designed tofunction without back-up control, however the aircraftmanufacturer supplies an optional electrically operatedback-up fuel flow control. This system permits automaticfuel control as a function of the other engine's N1, in the

event of a major failure.

This function is optional.Monitoring

This function ensures engine monitoring, fault mand maintenance aid.

Maintenance aid

The EECU permanently records and mparameters and engine events.They can be transmitted to the displays and the cockpit, for maintenance aid purposes.

Note : The operation described in the folconsiders the following modes :

- Starting

- Idle and Transition from idle to fli- Fuel control - Generalities- Speed control- N1 limits- Fuel flow limits- Selection and indication of ratings- Indication and monitoring- N2 overspeed .


AUTOSTARTING MAINTENANCE AID

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CONTROLSYSTEM

MONITORING

- Sequential control

- Fuel flow control

SPEED CONTROL

- N2 rotation speed

- Engine protection



Functions ensured by the electronic controlsystem

Monitoring

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This part mentions in a general way the main functionalelectronic blocks.

Determination of control mode

Starting

N2 speed controlAnticipation

Load sharing

Selection of N1 datum

Limitations (N1, torque

)

N1 speed control

Flow datum selection

Flow limitation

Control of the metering needle

- Data bus interfaces with the aircraft- Fault detection and indication

- Cycle counting

- N1 indication calculation

- Counting and indicating of OEI usage

- Engine power check

- EECU hours counting

- Bleed valve monitoring

- Maintenance aid.


Determination ofcontrol mode

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Loadsharing

N1datum

selection

Anticipation

N2 speedcontrol Limitations

N1 speedcontrol

N1calculation

Fault detectionand indication

Bleed valvemonitoring

Maintenanceaid

Enginepower

check AIRCRAFT

s

l

OEI

counting

EECUhours counting

Overspeedprotection



Starting Starting fuel flow control

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This function includes the starting sequence, the startingfuel flow control, idle, the transition from idle to flight andrelight in flight.

Starting sequence

The system ensures the cranking (starter), ignition (ignitionunit) and the fuel supply.

Start is selected using the Stop/Idle/Flight selector :

- Stop (selection of engine shut-down)

- Idle (start control up to idle)

- Flight (normal control).

Note : Refer to "FUEL SYSTEM" and "STARTING" chapters for more details on engine starting.

In-flight relight

The sequence is identical to a ground start, but onlypermitted below 17 % N1. I

Documents

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