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THIS HANDBOOK IS FOR REFERENCE PURPOSES ONLY.IF FAULT ISOLATION OR MAINTENANCE IS REQUIRED, REFERTO THE APPLICABLE MANUFACTURERS TECHNICAL MANUAL
FOR SPECIFIC PROCEDURES
Hamilton Sundstrand reserves the right to make changes in specificationsand other information contained in this publication without prior notice
NOTICE
THIS TRAINING MANUAL IS TO BE USED FOR TRAINING PUPOSES ONLY
This training manual was prepared by Hamilton Sundstrand for training purposes only.
Some information contained herein is proprietary and/or copyrighted information of Hamilton Sundstrand. As a condition of, and as consideration for receiving thisdocument, the recipient agrees that this document and the information containedtherein shall not be disclosed outside the recipient or duplicated or used for anypurpose without Hamilton Sundstrand’s prior written consent.
Use or disclosure of this data is subject to therestriction on the title page of this document.
PREFACE
GENERAL DESCRIPTION
The APS 3200 Auxiliary Power Unit Maintenance Training Course,developed by the Customer Service Training Group of HamiltonSundstrand Power Systems, is designed to give the student anunderstanding of the various components of the Auxiliary Power Unit(APU) and their functions. This course also provides routinemaintenance and troubleshooting.
STUDENT WORKBOOK
This workbook is intended for the “limited” purpose of providingcomponent familiarization, general data, and support information for
this maintenance course.
This is an uncontrolled document and will not be updated or revisedon a regular basis. Specific values given in this document such asspeed, temperature, and pressure are provided for the purpose ofillustration and are not necessarily representative of the true valuesof the APS 3200 APU.
FAA AND AIRCRAFT MANUFACTURER APPROVEDPUBLICATIONS
The Airline is provided a variety of FAA and Aircraft Manufacturerapproved publications for the APS 3200 APU. These publicationsare:
Aircraft Flight Crew Manuals
Aircraft Maintenance Manuals
Engine and Component Maintenance Manuals
Service Bulletins
Chapter 49 of the aircraft maintenance manual presents detailed APU and LRU removal and installation procedures plus maintenanceand servicing techniques that can be accomplished at the flight-line.Careful study of Chapter 49 will add to the student's expertise introubleshooting and maintaining the Hamilton Sundstrand APS 3200
OIL CAPACITY 3.9 L (4.16 Qts) (add)5.4 L (5.72 Qts) (full)
OIL TEMPERATURE (SHUT DOWN) 135°C (275°F) Lubrication system185°C (365°F) AC Generator
APPROVED OIL SPECIFICATION:
MIL-PRF-7808
MIL-PRF-23699
CAUTION:
DO NOT MIX OR SUBSTITUTE OIL SPECIFICATIONS. USE ONLY ONE OF THE APPROVED OILS. IF THE OIL SUPPLY IS LOW AND THE OIL BEING USED IS NOT AVAILABLE, DRAIN THE OIL SUMP AND CHANGE THE OIL FILTER. SERVICE THEOIL SYSTEM WITH AN APPROVED OIL.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APS 3200 - DESCRIPTION (1)Power Unit
The APU consists of a gas turbine engine (Power Section) whichdrives:
- A load compressor
- And an AC generator (alternator) through a gearbox.
The APU is of modular design. It has three modules:
- The power section
- The load compressor
- The gearbox.
A common air inlet supplies the load compressor, the cooling fan andthe power section.
Power Section
The power section is a single spool gas turbine engine which
consists of:
- A centrifugal compressor
- A reverse flow combustor chamber
- A two stage axial flow turbine.
Load Compressor
The load compressor is a single stage centrifugal compressor drivendirectly by the power section. Variable inlet guide vanes are used forairflow and exhaust gas temperature control.
Gearbox
The gearbox, also driven by the power section, is attached to theload compressor. The gearbox provides the drive at the correctspeed for the AC generator and the APU mechanically drivenaccessories.
Electronic Control Box
The ECB provides control and monitoring of the APU and is locatedin the aircraft rear cargo compartment.
Power section provides the shaft power to drive the loadcompressor and the gearbox.
Power is produced by transforming the energy contained in theambient air and the fuel through thermodynamic cycle: compression,combustion, expansion.
- Compression of the air in the single stage centrifugal compressor
- Combustion of the air-fuel mixture in the reverse flow combustorchamber
- Expansion of the burned gases across the two stage axial flowturbine to drive:
• The power section impeller
• The load compressor impeller
• The gearbox.
The load compressor supplies compressed air to the aircraftpneumatic system. The air is compressed by a single stagecentrifugal impeller and uses variable inlet guide vanes to control the
air flow. The compressed air is delivered through a scroll to the bleedcontrol valve.
The gearbox provides the drive for the AC generator, andaccessories for APU operation.
The AC generator that provides electrical power for the aircraftsystems.
The Electronic Control Box receives various signals from theaircraft and the APU to operate and monitor the APU.
The electronic control box controls the following:
- Rotation speed (N) (fuel flow)
- Load compressor surge protection (bleed control valve)
- Exhaust Gas Temperature (EGT) (inlet guide vanes).
Use or disclosure of this data is subject to therestriction on the title page of this document.
Use or disclosure of this data is subject to therestriction on the title page of this document.
POWER UNIT - DESCRIPTION (1)
The first part of the description deals with the APU rotating assemblyand the second part will consider the modular design of the APU.
The following main components are considered in this description:
gearbox, air intake plenum, load compressor and power section.
Gearbox
The gearbox located at the front of the APU provides the mechanicaldrive for the AC generator and the accessories required for the APUoperation. The oil sump is also part of the gearbox.
Load Compressor
The load compressor is driven by the power section and providescompressed air to the aircraft pneumatic system. It is a centrifugalimpeller that has variable inlet guide vanes to control the air flowoutput.
Air Inlet Plenum
The plenum is located between the load compressor and the power
section. The plenum directs the air supply to the power section, loadcompressor and the oil cooling system.
Power Section
The power section provides mechanical shaft power to drive the loadcompressor and the gearbox.
The power section comprises:
- A single stage centrifugal impeller
- A reverse flow combustion chamber
- A two stage axial flow turbine
- An exhaust system.
The main rotor assembly is supported by two bearings: A ballbearing at the front of the load compressor, a roller bearing at therear of the turbine.
HAMILTON SUNDSTRAND PROPRIETARYUse or disclosure of this data is subject to therestriction on the title page of this document.
POWER UNIT - OPERATION
General
The power section produces mechanical shaft power for APUoperation.
This mechanical power is used to drive:
- The load compressor which supplies compressed air
- The AC generator which supplies electrical power
- Accessories required for the operation of the APU.
Power Section Operation
The air enters the power section through the aircraft air inlet and the APU plenum.
In the plenum, this air is divided into two flows; one for the loadcompressor and one for the power section.
The power section air is directed to the centrifugal impeller which
increases the air pressure.
The air is then admitted to the combustion chamber, mixed with thefuel and burned to provide a continuous combustion process. Thegases are expanded across the turbines that transforms the gasenergy into mechanical energy.
The gases are then expelled overboard through the aircraft exhaustsystem.
Load Compressor Operation
The load compressor is driven by the power section and produces airflow to the aircraft pneumatic systems.
Gearbox Operation
The gearbox is driven by the power section to operate the APUaccessories and the AC generator.
Electronic Control Box (ECB)
The ECB provides control and monitoring of the APU.
Use or disclosure of this data is subject to therestriction on the title page of this document.
AIR INLET PLENUM - GENERAL
Location
The inlet plenum is located between the load compressor and thepower section.
Main Features
- Acoustically treated part
- Shop replaceable unit
- Weight: approx. 7.5 kg (16.5 lbs).
Main Components
The plenum consists of two parts, upper and lower, which areconnected by quick disconnect latches.
The lower part interfaces with the aircraft air inlet system. The airinlet to the plenum is provided with a screen made of stainless steelthat protects the APU internal components from foreign objectdamage.
The upper part has an outlet for air supply to the oil cooling system(supply to the oil cooler fan).
Construction
The plenum is of sandwich construction with a structural envelope,Nomex and felt metal. The structural envelope and Nomex are fire
proof.
Operation
In the plenum, the air is separated into two flows by the splitter.
- One for the power section: 2.2 kg/s (4.8 lbs/sec.)
- One for the load compressor and cooling fan: 1.2 kg/s (2.6lbs/sec.).
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AIR INLET PLENUM - DESCRIPTION
Identification of the Air Inlet Plenum Components
- The lower part of the air inlet plenum interfaces with the APU airinlet system. It has a screen to protect the APU internal
components from foreign object damage.
The lower part incorporates noise treatment and a splitter whichseparates the air into two flows. It also provides the support for thefollowing components:
• The ambient air pressure and temperature sensors
• The differential pressure sensor
• The low oil pressure switch
• The ignition exciter.
- The upper part of the air inlet plenum is also noise treated.
The upper part has an oval outlet to supply air to the oil coolingsystem
- The quick disconnect latches secure the upper part and lowerpart of the air inlet plenum.
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LOAD COMPRESSOR - DESCRIPTION (1)
The first part of this description deals with the load compressorcomponents, the second part will consider the inlet guide vanescontrol mechanism and the third part the identification of all thecomponents.
Air Inlet Housing
The housing allows the passage of air to the load compressor andsupports the inlet guide vanes. It is made of aluminum alloy.
Compressor Impeller
The impeller is constructed of titanium alloy. The rear shaft of theimpeller is connected to the rotor intershaft using a curvic coupling.The front is supported by a ball bearing.
Compressor Shroud
The shroud houses the impeller and is constructed of steel alloy.
Compressor Diffuser
It consists of 19 cambered vanes made of steel alloy.
Scroll
The annular scroll provides the air outlet of the load compressor. It iscast aluminum.
The scroll housing provides passages for static air pressure to theload compressor discharge pressure sensor.
Bearing
A ball thrust bearing supports the front shaft of the load compressor.It is mounted in the load compressor housing.
Bearing Seals
Oil that is used to lubricate the front bearing is prevented fromentering the impeller area by a floating carbon seal and a labyrinthseal.
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LOAD COMPRESSOR - DESCRIPTION (2)
Identification of Load Compressor Components
- The IGV assembly includes the variable inlet guide vanes, therack and pinion mechanism and the air inlet housing
- The compressor shroud houses the impeller.
- The load compressor impeller has main blades and splitterblades. The impeller is connected at the rear to the inter shaft bycurvic-coupling. The impeller front shaft is supported by the frontbearing.
- The scroll provides the air outlet of the load compressor. Thescroll also houses the load compressor diffuser.
- The front bearing is a ball bearing that supports the impeller frontshaft
- The labyrinth seal is pressurized with compressed air from thepower section impeller.
- The front bearing nut retains the front bearing and forms thephonic wheel of the speed sensing system
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LOAD COMPRESSOR - OPERATION
Air Inlet
The ambient air enters the APU through the aircraft air inlet and the APU plenum.
The plenum air is separated into three flows:
- Air for the power section
- Air for the oil cooling system
- Air for the load compressor.
The air for the load compressor passes through the inlet guidevanes; the flow of air depends upon the position (the angle) of thevanes. The air is then directed to the blades of the compressorimpeller.
Compression
As the air enters the blades of the rotating compressor impeller theair velocity increases.
The air leaves the tip of the blades at high velocity and flows throughthe diffuser vanes where velocity is transformed into pressure.
Delivery
The compressed air then flows into the scroll and delivered to the
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POWER SECTION - COMPRESSOR - DESCRIPTION
Identification of Compressor Components
- The intermediate shaft is connected to the front of the loadcompressor impeller and to the rear of the power sectioncompressor impeller by curvic-couplings.
- The compressor housing houses the impeller and thecompressor shield.
The compressor housing is attached at the front to the air inlethousing and at the rear to the diffuser assembly and the combustorhousing.
- The impeller containment shield is mounted to the compressor
housing.
- The impeller has main blades and splitter blades. The impeller isconnected at the front to the intermediate shaft and at the rear tothe turbine by curvic-couplings.
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POWER SECTION - COMBUSTOR CHAMBER -DESCRIPTION
Identification of Combustor Chamber Components
- The combustor housing houses the combustor chamber. It alsohas bosses for the mounting of the fuel injectors, the igniter plugsand the combustor chamber drain valve.
- The combustor chamber has holes and tubes that allows air usedfor combustion and cooling to enter the combustor chamber.
- The bend assembly guides the burned gases from the combustorchamber to the inlet of the first stage turbine nozzle guide vane.
- The heat shield protects the diffuser holder plate of the powersection impeller.
The heat shield is located between the bend assembly and thediffuser assembly.
- The combustor chamber drain valve is threaded into the bottomof the combustor housing, this allows unburned fuel to drainoverboard. The valve is closed by air pressure in the combustorhousing.
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POWER SECTION - TURBINE - DESCRIPTION
Identification of Turbine Components
- The first stage nozzle guide vane has 22 vanes installed in frontof the first stage turbine wheel
- The first stage turbine wheel has 37 fir tree blades inserted into adisc and secured by blade locks.
The turbine wheel is connected to the rear of the power sectionimpeller and to the second stage turbine wheel by curvic-couplings
- The second stage nozzle guide vane has 26 vanes installed infront of the second stage turbine wheel
- The second stage turbine wheel has 31 fir tree blades insertedinto a disc and secured by blade locks. Vibration dampers arefitted between the blades.
The turbine wheel is connected to the first stage turbine wheel by acurvic coupling.
The rear of the second stage turbine wheel is supported by a rollerbearing
- The containment shield is located around the turbine wheels.
- The turbine housing is located between the containment shieldand the turbine.
The turbine housing is connected to the exhaust housing.
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POWER SECTION - EXHAUST - GENERAL
Function
The exhaust directs the exhaust gases to the aircraft exhaust pipe.
Location
The exhaust diffuser is located inside the APU exhaust housing.
Type
One piece, annular exhaust pipe.
Main Components
The exhaust housing is constructed of stainless steel and provides apassage for the exhaust gases. The housing also contains the rearbearing and struts that house oil pipes to the rear bearing.
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POWER SECTION - OPERATION (1)
The power section produces the shaft power through thethermodynamic cycle: compression, combustion, expansion andexhaust.
Compression
Ambient air is directed into the blades of the rotating impeller. The airthen flows through the divergent passages of the diffuser. (The airvelocity is transformed into pressure.)
Combustion
The compressed air is divided into two flows:
- A primary flow mixed with the fuel for combustion
- A secondary flow (dilution air) to cool the combustor and internalparts.
As a result of the continuous burning process, the pressuredecreases slightly whereas the velocity and the temperatureincrease.
Expansion
Expansion of the gases takes place across the two stages of theturbines, this transforms the gas energy into shaft power.
The gases flow through the nozzle guide vanes which increase thevelocity, then across the turbine blades. The aerodynamic forcescause the turbine wheels to rotate.
During expansion, the velocity of the gases increases and thepressure and temperature decrease.
Exhaust
The gases are then expelled overboard through the exhaust system.
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POWER SECTION - OPERATION (2)
The power section provides air flow to pressurize the APU labyrinthseals, to cool internal heated parts and balance rotor forces.
Pressurization
- Pressurization of Labyrinth Seals
Labyrinth seals are supplied with air pressure. A pressuredifference across the seals provide a non contact seal.
- Pressurization of Load Compressor Front Bearing
The pressurized air, bled from the outlet of the power sectionimpeller, flows through an external pipe to the labyrinth seal of the
load compressor front bearing and the cooling fan labyrinth seal.
- Pressurization of Power Section Rear Bearing
The pressurized air, bled at the outlet of the power sectionimpeller, flows through the power section rotor assembly to therear bearing labyrinth seal.
Cooling
To prevent excessive heating of the parts subjected to thecombustion gases, a circulation of cooling air (bled at the outlet ofthe power section impeller) is provided through the power section
rotor assembly, and is directed by internal passages to the turbinewheel faces.
Balance of Forces
The shaft, the turbine wheels, and the compressor impellers aresubjected to axial forces resulting from the operation of the rotorassembly.
To reduce the forces on the bearings, air pressure is used on thebackside of the power section impeller.
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OIL SYSTEM - DESCRIPTION
Oil Sump
The oil sump is formed by the lower part of the gearbox.
The gearbox has a fill tube for gravity filling, an overflow drain, apressure fill connector and a sight glass.
The gearbox intermediate gear also functions as the air/oil separatorand provides air venting of the gearbox.
Oil Pumps
One lubrication pump and two scavenge pumps are driven by thegearbox.
The pressure system is provided with a pressure relief valve locatedon the front of the gearbox.
Oil Filters
There is one filter in the lubrication line and one in the AC generatorscavenge line.
Both filters are the same and each have a filter element impendingblockage switch indicator. They are mounted on the lower front faceof the gearbox. The oil filter by pass valve for each filter is located inthe gearbox and is non adjustable.
Oil Cooler
The oil cooler cools the oil and has a by-pass valve.
De-oili ng Valve
The de-oiling valve is a solenoid valve located at the inlet of thepressure pump. When energized open, the valve prevents oil flowthus reducing the APU starting loads on the starter.
Monitoring Devices
- Low oil pressure switch
- High oil temperature sensor
- AC generator high oil temperature sensor
- Oil level sensor
- Oil level sight glass
- Oil filter impending blockage switch indicator on each oil filterassembly
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OIL SYSTEM – OPERATION
The main functions of the oil system are : oil supply, scavengereturn, venting and indicating.
Oil Supply
The lubrication pump draws the oil from the sump and delivers it to
the oil system. During starting, the de-oiling valve opens and air isdrawn into the pump to prevent oil flow. After de-oiling the oil flows tothe oil cooler, then to the filter.In the event oil flow through the filter becomes restricted, the switchindicator is activated. If the filter becomes blocked, the oil filterbypass valve will open and allow flow to the oil system.The oil pressure relief valve opens to regulate the oil systempressure. When the valve is open, some of the oil flow is bypassedback to the inlet side of the lubrication pump.
Scavenge Return
After lubrication, the oil returns to the gearbox sump by twoscavenge pumps:- One for the power section rear bearing that returns the oil directly
to the sump- One for the AC generator that returns the oil to the sump through a
filter.Note: The front bearing and the gearbox are scavenged by gravity.
Scavenge Return
After lubrication, the oil returns to the gearbox sump by twoscavenge pumps:
-One for the power section rear bearing that returns the oil directly tothe sump
One for the AC generator that returns the oil to the sump through afilter.
Note: The front bearing and the gearbox are scavenged by gravity.
Venting
Oil mist in the gearbox is separated by a centrifugal air-oil separator.
The gearbox is vented to the exhaust through an external pipe.
Monitoring-Low oil pressure switch-High oil temperature sensor- AC generator high oil temperature sensor- Oil filter impending blockage switch indicators- Oil level sensor- Oil level sight glass- Magnetic drain plug
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ENGINE LUBRICATION (2)
Front Bearing Lubrication
Oil Supply
The lubrication for the rotor front bearing is provided by pressurized
oil from the gearbox oil system.
A jet located in the gearbox housing sprays oil between the front endof the load compressor shaft and the front bearing nut. (PhonicWheel)
The oil runs along the shaft, lubricates the quill shaft splines andenters the gap through the split inner races to lubricate the bearing.
Oil flow to the bearing is also provided by oil passages between thegearbox and bearing outer race to provide a squeeze film to dampenbearing vibration.
Scavenge and Return
After lubrication the oil is returned to the sump by gravity.
Sealing
Oil sealing of this assembly is by a floating carbon seal and a
labyrinth seal using air from the power section impeller.
A drain cavity between the seals is vented overboard, into the APUdrainmast.
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ENGINE LUBRICATION (3)
Rear Bearing Lubr ication
Oil Supply
The lubrication of the rotor rear bearing is provided by pressurized oilfrom the gearbox oil system.
The oil is supplied to the rear bearing through an external pipe.
In the bearing area, the oil is directed to the outer race to provide asqueeze film and an internal line that sprays oil into the rear tie-boltarea.
Drilled passages in the tie-bolt allow oil circulation for lubrication andcooling of the roller bearing.
Scavenge and Return
After lubrication, the oil is scavenged back to the sump through anexternal pipe by a scavenge pump.
Sealing
Oil sealing in the bearing area is accomplished by a floating carbonseal and a rotating labyrinth seal. The seals are pressurized with airflow from the power section impeller.
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AIR-OIL SEPARATOR
Function
The air-oil separator separates the oil from the air.
Location
The air-oil separator is located in the upper part of the gearbox.
Description
The air-oil separator is part of the gearbox intermediate gear.
The gear has a hollow shaft with radial drillings. The rear of thehollow shaft vents into a passage in the gearbox housing.
Operation
An air-oil mist is created in the gearbox when the APU is operating.
The oil is separated from the air by the rotating action of the gearboxintermediate gear. The oil returns to the gearbox sump by gravityand the air is vented through a pipe to the APU exhaust.
Use or disclosure of this data is subject to therestriction on the title page of this document.
Function
One pump is used for the lubrication supply and two pumps forscavenge.LocationThe oil pumps are located inside the gearbox front face.
Main Features- Lubrication pump
• Type: Vane type• Flow: 2160 l/h (570 GPH)
- AC generator scavenge pump• Type: Vane type pump• Flow: 2160 l/h (570 GPH)
- Rear bearing scavenge pump• Type: Gerotor type pump
• Flow: 160 l/h (42 GPH)
Gerotor Type
The gerotor is a positive displacement pumping unit consisting of twoelements: an inner and outer rotor.The inner rotor has one less tooth than the outer, and has itscenterline positioned at a fixed eccentricity from the centerline of the
outer element.The inner element is driven by the gearbox.Vane TypeThe vane type pump consisting of a slotted inner rotor equipped withvanes operating in an eccentric housing.Operation of the Pressure Relief ValveThe oil pressure relief valve is a non adjustable, spring loaded reliefvalve.The valve will open when oil pressure reaches 345-414 kPag (50-60
PSIG). The oil that is bypassed, returns to the inlet of the lubricationpump.
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DE-OILING VALVEFunction
The de-oiling valve reduces the APU starting lead during startconditions.
Location
The valve is located on the left side of the gearbox.
Main Features
- Solenoid valve operated by the ECB
- Nominal rating: 28 VDC; 1.0 amps
- Solenoid valve energized open.
Description
The de-oiling valve is a solenoid operated valve directly controlled bythe ECB.
Operation
During the APU start up the de-oiling valve is energized open by theECB. When the valve is open the lubrication pump is prevented frompumping oil into the system. This reduces the starting load of the
APU and allows faster acceleration.
When the APU accelerates to 55% speed, the ECB de-energizes thede-oiling valve and allows the lubrication pump to produce oil flow.
During shutdown, the de-oiling valve is again energized by the ECBwhen the APU de-accelerates to 90% speed. This allows the oilremaining in the system to return to the oil sump with the exceptionof one quart remaining in the oil cooler.
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OIL FILTER - OPERATION
Oil Flow
In normal operation the oil is filtered and then flows to the oil system.
Pre-blockage of the Oil Filters
Should the filter become contaminated, a difference in pressureacross the filter will occur.
Two switch indicators are mounted on the front of the gearbox neareach oil filter. The switch indicator provides a visual indication whenthe oil temperature is 74°C (165°F) and the oil pressure across thefilter reaches 241 kPad (30-35 PSID). The ECB also monitors eachswitch indicator and will store the fault message.
By-pass
When the differential pressure across the filter exceeds 345 to 414kPad (50 to 60 PSID), the by-pass valve will open and allowunfiltered oil to flow into the system.
The by-pass valve is located in the gearbox and is non-adjustable.
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Normal Operation
The oil delivered by the lubrication pump flows through the aluminumcooling tubes that are cooled by the cooling fan air flow.
The cooled oil then flows to the various APU lubrication points.
By-pass Operation
When the pressure exceeds 207 kPad (30 PSID), the bypass valveopens.
The oil flow by-passes the cooler to the lubrication system.
Check Valve Operation
The check valve is an oil pressure operated valve.
When the pressure in the oil system is low (de-oiling during start andshutdown), the check valve closes and prevents draining of the oilcooler into the sump.
The check valve traps approximately one quart of oil in the oil cooler
when the APU is not running.
Air Flow
The oil cooler uses the airflow from the cooling fan to remove heatfrom the oil. The heated air is then discharged overboard through anair duct located in the left APU compartment service door.
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General
Function
The Oil Temperature (HOT) sensor senses the temperature of the oilat the outlet of the oil cooler. When the oil temperature is too high,
the HOT sensor initiates automatic APU shut down.
Location
The HOT sensor is installed on the lower rear face of the gearbox.
Main Features
- HOT sensor setting: 135° C (275° F)
- Sensor input signal (from ECB): 1 mA
- Sensor output signal (to ECB): variable output voltage
- 100 Ω RTD; 1 mA; 19°C to 149°C (67°F to 300°F.)
Interfaces
- The ECB
- The APU oil system.
Functional Description
The HOT sensor is a Resistive Temperature Device (RTD) suppliedwith a constant current of 1 mA (by the ECB). The resistance varieswith the oil temperature and modifies the sensor output voltage.
When the oil temperature reaches a limit value of approximately135°C (275°F), the ECB will initiate automatic APU shut down.
Note: The AC generator also has an integral oil temperaturesensor which causes the APU to shut down when anexcessive temperature is detected (180°C; 365°F). Thesensor is monitored by the ECB.
The oil level sight glass is located on the lower left side of thegearbox housing, close to the oil fill tube.
It provides a visual indication of the oil level in the sump.
Oil level ADD and FULL marks are written on the sight glass.
housing. Removing the plug allows oil drainage from the sump. Thedrain plug embodies a magnetic chip detector that attracts ferrousmetal particles in the oil. The detector can be removed, inspectedand installed without draining the oil sump.
A self sealing valve in the drain plug housing prevents oil drainagewhen the magnetic chip detector is removed.
- The starter motor is energized and cranks the APU rotor assembly
- The ignition exciter operates and supplies high voltage spark to thetwo igniter plugs
- The 3 way solenoid valve is energized open to provide fuel flow tothe injectors
- The servo valve is electrically operated to control the fuel flow.
Fuel from the aircraft fuel system is supplied by the low pressure andhigh pressure pumps through the servo valve and the 3 way solenoidvalve.
When the fuel pressure reaches approximately 138 kPad (20 PSID),the flow divider delivers fuel to the pilot injectors. The fuel injectedinto the combustor is ignited by the ignitor plugs.
When the fuel pressure reaches approximately 1380 kPad (200PSID), the flow divider delivers fuel to the main injectors.
signals from the ECB.
At self-sustaining speed, the starter and the ignition system aredeactivated and the APU accelerates to 100% speed.
The APU is maintained at 100% speed under all load conditions bythe servo valve controlling fuel flow.
The fuel control unit provides a flow higher than APU fuel flowrequirements. The fuel is metered by the servo valve and iscontrolled by the ECB. The excess fuel is returned to the HP pumpinlet through the constant AP valve and the fuel filter.
- Transient condition
When the load applied to the power section changes, the rotationspeed changes. The ECB senses the change and implements asignal to the servo valve. The fuel flow is metered to keep the rotorspeed constant.
g y jshut off and bypassed back into the fuel system.
One second later the ECB de-energizes the fuel servo valve.
Any fuel remaining in the pilot manifold assembly and fuel injectors ispurged into the exhaust by combustor air pressure.
• A high pressure pump (gear type) provided with apressure relief valve
- A drain line for the pump shaft seal
- A filter which includes a filter element, a by-pass valve and animpending blockage AP indicator
- A servo valve (electrically operated valve that meters fuel flow inresponse to signals from the electronic control box)
- A constant P valve (a valve that controls the differential pressureacross the servo valve)
- A 3 way solenoid valve (valve operated by the electronic controlbox to open and close fuel flow to the fuel injectors)
system actuators:
• A fuel outlet port (fuel supply to the actuators)
• A fuel return port (fuel return from the actuators)
- A fuel inlet union (connected to the aircraft fuel system)
- An electrical connector (current signals from the electroniccontrol box to the 3 way solenoid valve and the servo valve).
O-rings
Two O-rings are located on the fuel control. One on the fuel controlmounting flange and one on the drive shaft. Both O-rings must beproperly installed or excessive loss of oil will occur when the APU isoperating.
- An impending blockage P indicator to provide a visual warningof a restricted filter
Setting: 48 kPad (7 PSID)
- A by-pass valve to allow the fuel supply in the event of filter
blockage
Setting: 324 kPad (46 + - 4 PSID).
O-ring
An O-ring is located inside the fuel filter cavity of the fuel control unit.The O-ring functions as a seal and a securing device for the filterbowel. The bowel is not secured by any external locking device.
The valve consists of a torque motor which operates a fuel meteringvalve (clevis type).
The motor is electrically controlled by the ECB. ECB currentoperates the valve to meter fuel flow.
During starting, the servo valve meters fuel flow to accelerate the APU.
In normal operating conditions, the fuel flow is metered to maintain aconstant 100% speed.
The main features of the servo valve are:
- Type: Torque motor
- Current: 0 - 100 mA
- Metered flow: 6 - 198 kg/h (13 - 435 lbs/hr).
The solenoid valve is energized open to supply fuel to the fuelinjectors (control from ECB).
When de-energized, a spring moves the valve to the close position.
When the valve closes, the fuel is shut off to the injectors andbypassed back into the fuel system.
During a normal or auto shutdown of the APU the ECB de-energizesthe 3 way solenoid valve, one second later the servo valve is de-energized.
In the event the 3 way solenoid valve does not close, the APU willshut down when the servo valve is de-energized. If this conditionoccurs, the ECB will store a fault message. (APU FUEL VALVEFAILED OPEN).
The flow divider distributes fuel from the fuel control unit to the pilotand main injectors. It also provides purging of the pilot injectorsduring APU shut down
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Two valves:
• A pilot injector and purge valve set at approx. 138 kPad
(20 PSID)
• A main injector valve set at approx. 1380 kPad (200 PSID)
- A filter screen (located at the fuel inlet)
- Fuel inlet/outlet ports:
• Fuel inlet from the fuel control unit
• Fuel outlet to the pilot manifold
• Fuel outlet to the main manifold
• Fuel outlet to the exhaust system (purge).
When the APU is started, the fuel pressure increases to 138 kPad(20 PSID). The pilot injector valve opens and allows fuel flow to thepilot injectors.
When the pressure reaches 1380 kPad (200 PSID), the maininjector valve opens allowing fuel flow to the main injectors.
- Normal Running Condition
The two valves remain open to allow fuel flow to the pilot injectorsand the main injectors.
- Shut-down
As the fuel pressure decreases, the two valves close. The fuelremaining in the pilot injectors is purged into the exhaust bycombustor air pressure. At this time, a momentary puff of smokemay be viewed coming from the APU exhaust. This is a normaloccurrence.
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It also supplies the pilot fuel injectors with fuel during normal running.
Location
The pilot manifold is mounted around the combustor housing.
Description
The pilot manifold consists of flexible pipes connecting the flowdivider to the three pilot injectors. It is comprised of teflon tubesencased in a single layer of steel braid that is covered with a rubber
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The three pilot injectors are installed on the rear of the combustor
housing:
- One at the top (at 12 o'clock)
- Two at the bottom (one at 4 o'clock and one at 8 o'clock)
- A fuel nozzle
- A heat shield
The injector fits into a heat shield that is provided with two air inletholes for cooling.
A gasket between the injector and the combustor housing.
Operation
A continuous flow of fuel is delivered to the combustor by the pilotinjectors and atomized by the fuel nozzles, the fuel is then mixedwith combustor air to maintain the combustion process.
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Location
The main manifold is mounted around the combustor housing.
Description
The main manifold consists of flexible pipes connecting the flowdivider to the six main injectors. It is comprised of teflon tubesencased in a single layer of steel braid that is covered with a rubbersheath.
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MAIN FUEL INJECTORS
Type
Air blast injectors.
Location
Operation
A continuous flow of fuel is delivered to the combustor by the maininjectors. The fuel is atomized by combustor air flowing through theshrouded air passage. The fuel is then mixed with combustor air tomaintain the combustion process.
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tank. The aircraft low pressure fuel pump provides fuel to the APU
when the aircraft tank pumps are not operating.
The low pressure valve is controlled by the ECB and is open whenthe APU is operating. The valve is closed when the APU is shutdown normally or by the APU fire switch.
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AIRCRAFT FUEL SYSTEM
The aircraft fuel system supplies fuel to the main engines and APU.
The aircraft fuel system has three main tanks:
- A left tank located inside the left wing
- A center tank located between the two wings
A low fuel pressure warning switch is located at the fuel inlet to thefuel inlet to the fuel control unit. The switch sends a signal to theECB if fuel pressure is too low.
The ECB will display "FUEL LO PR" message on the lower ECAMwhen the APU system page is selected. This requires the APU to beabove 7% speed and the fuel pressure below 109 KPag (15 8 PSIG)
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- A center tank located between the two wings
- A right tank located inside the right wing.
Each tank has electric pumps to supply the engines.
A cross feed valve, located between the tanks, connects the leftand right engine supply lines. In normal operation, the cross feedvalve is closed.
The low pressure valve isolates the APU from the fuel supply.
The valve is open when the APU is running. It closes when the APUis shutdown or when the FIRE switch is activated.
The APU low pressure fuel pump is controlled by a pressure switchlocated in the fuel line to the APU. The switch senses fuel tank pumppressure. If the pressure is too low or the fuel tank pumps are turnedoff, the switch will cause the APU low pressure fuel pump to turn on.
above 7% speed and the fuel pressure below 109 KPag (15.8 PSIG).
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AIR SYSTEM - GENERAL
Function
The air system provides compressed air to the aircraft on the groundand in flight.
Main Features
Component Location
The inlet guide vane system components are located on the rightupper side of the air inlet housing. The inlet guide vanes arelocated in the air inlet housing ahead of the load compressor air inlet.
The air bleed system components are located on the right lowerside of the load compressor scroll outlet
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- Flow: 1.2 kg/s (2.6 lbs/sec.)
- Pressure: 289.6 kPag (42 PSIG)
- Temperature: 232°C (450°F).
Main Components
Two systems are considered:
- The inlet guide vane (IGV) system controls the load compressorairflow and prevents EGT overtemperature of the power sectionduring load compressor operation. The inlet guide vanes arecontrolled by the ECB, servo valve, and the IGV actuator.
- The air bleed system delivers airflow from the load compressor tothe aircraft pneumatic system through a bleed control valve (BCV).The valve also functions as an anti-surge valve for the loadcompressor. The BCV is controlled by the ECB, servo valve, and
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The pressure is indicated on the lower ECAM APU system pagedisplay. The pressure is indicated by the load compressor dischargepressure sensor and transmitted to the indicator through the ECB,the ADIRU, the BMC computers in PSIG.
Air Sys tem Operation
The air system operation chart shows IGV and positions duringvarious modes of operation
.
ENGINE BLEED PACK MODE AIRCRAFT IGV BCVSPEED SWITCH MODEL POSITION POSITION
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Control Rod
The rod connects the actuator piston to the IGV assembly. It isconnected to the actuator piston by a quick release pin.
IGV Position Indicator
The actuator rod housing has a position indicator cast on the top andbottom of the housing. The indicator markings range from CLOSEDto OPEN. An external metal tab is attached to the control rod andfunctions as a position indicator for the IGV’s and used to manuallymove the IGV’s when the APU is not running. The igv’s should be inthe CLOSED position before starting the APU.
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INLET GUIDE VANE SYSTEM - DESCRIPTION (2)
Servo Valve
The servo valve controls the position of the actuator piston by usinga spill valve that meters the potentiometric jet. The servo valve has ametered fuel pressure inlet from the actuator and a return outlet tothe fuel control unit. The control current (0-100 MA) to the servovalve is provided by the ECB.
A t t
IGV Contro l Mechanism and Inlet Guide Vanes
The inlet guide vanes are part of the IGV assembly. A sector gear isattached to each inlet guide vane and is driven by a common ringgear.
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Actuator
The actuator consists of a piston that is positioned by fuel pressuremetered by the servo valve. The actuator also uses double dynamicseals for piston shaft sealing.
The position of the actuator piston is provided by a Linear VoltageDifferential Transducer (LVDT). The position signal is sent to theECB for control of the servo valve.
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INLET GUIDE VANE SYSTEM - OPERATION
Principle of Operation
The ECB provides a control signal (0-100 MA) to the servo valve byusing the following input signals.
- APU bleed switch
- Speed (100%)
APU Star ting
During start, the inlet guide vanes are in the closed position toreduce the APU starting loads. The inlet guide vanes are also in theclosed position during APU shutdown.
Operation
During load compressor operation the position of the guide vanes
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- EGT
- Air inlet pressure and temperature
- ECS mode
- MES mode.
The ECB control signal is sent to the servo valve. The servo valvemeters fuel pressure to control the actuator piston movement.
When the actuator moves, the linear voltage differential transducer(LVDT) sends the actuator position signal back to the ECB.
The actuator piston is maintained in a stabilized position by the ECBsignal (50 MA) to the servo valve.
The actuator piston positions the IGV assembly to control the airflowdelivery of the load compressor.
During load compressor operation, the position of the guide vanesare controlled by aircraft ECS computer signals sent to the ECB.
In the event APU exhaust gas temperature is too high during loadcompressor operation the ECB will signal the IGV actuator to reduceairflow delivery of the load compressor.
If inlet guide vane control is faulty, the IGV actuator will automaticallyposition the guide vanes to the closed position.
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AIR BLEED SYSTEM - GENERALFunction
The air bleed system provides air delivery to the aircraft pneumaticsystem while preventing load compressor surge.
Main Features
- Hydraulically operated actuator, controlled by a servo-valve andthe electronic control box.
Component Location
- The servo-valve, the actuator and the bleed control valve form acomplete assembly located on the right lower part of the auxiliarypower unit at the scroll outlet
- Two load compressor discharge pressure pipes:
• One located in the scroll outlet (high pressure)
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AIR BLEED SYSTEM - DESCRIPTION (1)
The air bleed supply is controlled by a bleed control valve.
This valve comprises of a housing, a butterfly valve and an actuator.
APU Bleed Switch
When the APU master switch is selected to off during bleed airoperation, the APU will continue to run in a cool down mode for amaximum time of 2 minutes.
APU Bleed Switch
When the APU master switch is selected to off during bleed airoperation, the APU will continue to run in a cool down mode for amaximum time of 2 minutes.
The cooldown time limit can vary from 0 to 2 minutes. The time limitdepends on when the APU bleed switch is turned off prior toselecting the APU master switch to OFF.
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Housing
The housing is mounted on the load compressor scroll outlet bymeans of a v-band clamp.
Butterfly Valve
The valve is located in the BCV housing and directs air flow from theload compressor to the aircraft pneumatic systems, APU exhaust orboth.
The butterfly shaft extends through the top of the BCV housing. Theshaft has a slot machined into it that provides manual positioning ofthe valve and also serves as a valve position indicator.
Low B leed Air Pressure
In the event low bleed air pressure occurs, cycle the APU bleedswitch OFF and then to ON. This may restore the system to normal.
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AIR BLEED SYSTEM - DESCRIPTION (2)
Servo Valve
The servo valve controls the position of the actuator piston by usinga spill valve that meters the potentiometric jet. The servo valve has ametered fuel pressure inlet from the actuator and a return outlet tothe fuel control unit. The control current (0-100 MA) to the servovalve is provided by the ECB.
Actuator
Bleed Control Valve
The bleed control valve (BCV) delivers compressed air to the aircraft,also the valve functions as an anti-surge valve for the loadcompressor.
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The actuator consists of a piston that is positioned by fuel pressuremetered by the servo valve. The actuator also uses double dynamicseals for piston shaft sealing.
The position of the actuator piston is provided by a linear voltagedifferential transducer (LVDT). The position signal is sent to the ECBfor control of the servo valve.
a flexible support. One of them varies if the support is deformed bythe air pressure. The whole bridge is supplied by a 5 VDC constantsource voltage coming from the ECB. The changes of the variableresistor cause the output to vary (from 0 to 50 mV).
- The temperature sensor is a resistor which is fed by a constant 1mA current supplied by the ECB. The output voltage changes fromapproximately 0.8 to 1.2 VDC according to the resistance changes
from -55 to +50°C (-67 to +122°F).
The ECB detects a sensor failure if:
- The measured ambient pressure is lower than 3.45 kPaa(0.5 PSIA) or higher than 110 kPaa (16 PSIA)
- The measured inlet temperature is lower than -62°C (-80°F) orhigher than 76°C (170°F)
Normal BCV control will be maintained if either air inlet pressure ortemperature sensor is failed.
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ACCESSORY COOLING - GENERAL
Function
The accessory cooling system supplies air for the oil cooler and forthe APU compartment ventilation.
Location
The system components are located on the APU.
Main Features
Cooling Fan
The fan provides cooling air to the oil cooler and to the compartmentcooling duct. The fan assembly incorporates a permanent magnetgenerator that is used for APU backup overspeed and to preventmomentary power interruption of the ECB.
Fan Outlet Duct
This duct connects the outlet of the cooling fan to the inlet of the oilcooler
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Cooling by circulation of air taken from the air inlet plenum andaccelerated by the cooling fan.
Main Components
The main components of the system are the fan inlet duct assembly,
the cooling fan, the fan outlet duct assembly, the oil cooler and theoil cooler exhaust duct.
Fan Inlet Duct
This duct connects the engine air inlet plenum to the inlet of thecooling fan.
cooler.
Oil Cooler Exhaust Duct
This duct connects the oil cooler outlet to the APU compartment doorvent.
Compartment Cooling
The APU compartment is ventilated by air ducted from the coolingfan outlet duct. The air is discharged into the compartment throughthe compartment cooling duct.
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ACCESSORY COOLING - COOLING FAN
Description
The cooling fan is mounted on the gearbox and aligned by a locatingpin. The fan mounting flange is secured to the gearbox by a v-bandclamp.
The fan is driven by a shaft assembly that is supported by two ballbearings, the bearings are lubricated by the APU oil system. The
shaft assembly uses a carbon seal and two labyrinth sealspressurized by the power section impeller air. The oil used forlubrication of the cooling fan is returned to the oil sump by gravity.
Operation
Cooling Fan
The cooling fan accelerates the air flow through the oil cooler.Cooling air is also used for APU compartment cooling.
PMG
The permanent magnet generator (PMG) is driven by the cooling fanshaft. The PMG provides momentary (240 msec) of rectified
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g p y g y
A permanent magnet generator (PMG) and a printed circuit boardare located in the fan housing. The printed circuit board contains therectifier components for the PMG electrical power output to the ECB.
The cooling fan can be used to turn the APU rotor assembly during
borescoping. This is accomplished by removing the fan inlet duct andmanually rotate the fan impeller.
p y ( )electrical power to the ECB when the aircraft electrical power isinterrupted during power transfer.
One unrectified PMG output provides a frequency signal to the ECBthat is used for the back up overspeed signal.
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ELECTRONIC CONTROL BOX - GENERAL
ELECTRONIC CONTROL BOX - DESCRIPTION (1)
ECB Inputs
General
This chapter considers the discrete and analog input signals to theECB.Sensors and Discrete Inputs from Ai rcraft to ECB
The corresponding signals form part of the ECB Inputs-Outputsdefinitions and PIN assignments.
The bleed control valve (BCV) command is transmitted to theECB by means of an aircraft discrete signal. Upon receipt of thiscommand, the ECB contro ls the opening o f the BCV to supplythe aircraft pneumatic sys tem.
Air/ground Conf iguration Switch (open/ground)
This signal to the ECB is to indicate whether or not the aircraft is in-flight operation. Special considerations (i.e. safety systems) apply forin-flight operation.
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definitions and PIN assignments.
APU Stop (ground)
The stop signal is transmitted to the ECB by the APU master switchin the flight deck. Actuating the switch causes a contact closure toground.
Bleed Control Valve Activation (ground)
Emergency Stop (ground for approx. 150 ms)
The emergency stop signal is transmitted to the ECB by means of adiscrete signal created by a contact closure to ground.
in flight operation.
MES Mode (28 V)
This signal indicates to the ECB whether or not the aircraft is in MainEngine Start mode (MES) of operation. The circuit is normally open.In the MES mode, the aircraft causes the circuit to close and tosupply a 28 V signal to the ECB.
Start Contactor Monitor (28 VDC/open/ground)
This discrete 28 VDC signal tells the ECB whether or not the back-upstart contactor is closed or whether or not it is open.The start contactor monitor is used exclusively for fault isolation
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ELECTRONIC CONTROL BOX - DESCRIPTION (2)
Sensors and Discrete Inputs from Aircraft to ECB (continued)
Air Intake Flap Open Posi tion (28 VDC)
When the air intake flap is in the fully open position, a switch isactivated to supply a 28 VDC signal to the ECB.
This signal is used to initiate the start sequence.
JAR Configuration
The ECB is programmed in the JAR mode. This means that allshutdown faults sensed by the ECB will cause the APU to shutdownon the ground or in flight.
Low Fuel Pressure Switch (open/ground)
The switch closes to ground when the fuel pressure falls below agiven pressure.
Air Intake Flap Closed Posit ion (ground)
When the air intake flap is in the fully closed position, a switch isactivated to the closed position and provides a ground signal to theECB. The aircraft relay operation is maintained until the flap closedsignal is received.
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Start Command (28 VDC for approx. 150 ms)
This command is activated by momentarily placing the start button in
the flight deck to "on". This action provides a 28 V signal to the ECB.
During normal APU operation, a 28 VDC signal is transmitted to theECB when voltage is being applied to open or close the air intakeflap.
Generator Oil Temperature Sensor (100 )
This sensor is mounted in the AC generator. The wiring uses thegenerator connector, P4. The sensor is a resistance temperaturedevice (RTD). It's variable resistance is a function of temperatureand is supplied with a constant current of 1 mA.
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ELECTRONIC CONTROL BOX - DESCRIPTION (3)
Sensors and Discrete Inputs from APU to ECB
Low Oil Pressure Switch (ground)
The low oil pressure switch is a normally closed contact. The switchopens and remains open when oil pressure is present.
Oil Filter Switch Indicators
This is a differential pressure switch that is normally open. Thecontact closes and provides a ground signal in case of filterrestriction.
EGT Sensors
This sensor is a variable resistance device supplied by a constantsource voltage of 5 VDC.
The output ranges from 0 to 50 mV for a 0 to 15 PSIA range of airpressure.
Load Compressor Discharge Air Pressure Sensors (P) and (
P)
There are two sensors: one to measure the pressure at the loadcompressor scroll (P), the other one to measure the differential airpressure between the diffuser and the scroll (AP). The ratio signal
AP/P is used to prevent load compressor surge.
The two sensors are of variable resistance type supplied by aconstant voltage of 5 VDC
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The EGT is measured by two independent thermocouples. They areK type (Chromel-Alumel).
The output is of approx. 1 mV per 24°C (43°F).
High Oil Temperature Sensor (100 )
The sensor is a Resistance Temperature Device (RTD). Theresistance varies according to the oil temperature and is suppliedwith a constant current of 1 mA.
Inlet Air Pressure Sensor
constant voltage of 5 VDC.
The outputs range from 0 to 50 mV for a 0 to 100 PSIA (absolute) or0 to 25 PSID (differential) ranges of air pressure.
Rotation Speed Sensors
There are two independent speed sensors mounted in the gearbox.
They provide a wave signal as a function of the teeth on the phoneticwheel (24) and the rotation speed (i.e. 19720 Hz at 100% speed).
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ELECTRONIC CONTROL BOX - DESCRIPTION (4)
Sensors and Discrete Inputs from APU to ECB (continued)
Inlet Air Temperature Sensor (1000 RTD)
The sensor is a variable resistance temperature device supplied by aconstant source current of 1 mA. Temperature range -55 to 150°C(-67 to 302°F).
Engine ID Module
The engine identification (ID) module is resistors that provide theECB with 3 voltage lines V 1, V2, V3 matched to the engine IDnumber. The engine serial number is the sum of the ID number andthe number 1000.
IGV and Bleed Control Valve LVDTs(Linear Voltage Differential Transducer)
LVDTs are used to detect the actual displacement of the IGV andBCV actuators. Their signal is fed back to the ECB for the purpose ofservo control.
Their primary coil is supplied with a constant voltage of 10 VAC.Their secondary coil provides a variable output voltage.
Upon loss of electrical signal, the IGV will close or the BCV opens todischarge.
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The engine ID number is stored in the ECB NOVRAM memory aspart of the power up initialization. The ID module is considered failedwhen all inputs are shorted, one or all inputs are open, a number
greater than 2048 is used, or 3 consecutive readings at power upinitialization are not identical.
The gearbox mounted oil level sensor is a Resistance TemperatureDevice (RTD) type. The variable resistance value is provided with aconstant current of 75 mA. The oil level is checked at power up over
a period of 8 seconds and is determined OK or LOW.
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ELECTRONIC CONTROL BOX - DESCRIPTION (5)
Sensors and Discrete Inputs from APU to ECB (continued)
Permanent Magnet Generator (PMG)
A Permanent Magnet Generator (PMG) is installed in the cooling fan.The assembly consists of the PMG rectifier circuit and a DC fusiblelink.
The PMG provides the ECB with rectified power and one unrectified
signal from one of the three phases (backup overspeed protection at107%).
The unrectified output is current limited (short circuit protection) bymeans of a resistor. The fusible link trip point is at 10 A.
Starter Motor Voltage
The starter motor is monitored by the ECB for low voltage during APU start. The low voltage sensing connector is located on the frontface of the starter motor housing.
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The rectified output provides 40 VDC at 100% speed for back-uppower supply to the ECB in the event of a momentary interruption inthe main power supply. This back-up supply lasts for 240 msec.
Note: The failure of the PMG/Speed circuit at startup will cause the APU to shutdown during acceleration.
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ELECTRONIC CONTROL BOX - DESCRIPTION (6)
ECB Outputs
General
This chapter considers the discrete and digital outputs of the ECB.
Discrete and Digital Outputs (to the aircraft)
Backup Start Contactor (28 VDC, 1 A nominal)
This contactor is energized by means of a discrete signal. The signalis supplied through a Field Effect Transistor (FET) in the ECB.
Main Start Contactor (28 VDC, 1 A nominal)
Thi t t i i d b f di t i l Th i l
Bleed Control Valve Open (28 VDC, 0.1 A)
The ECB transmits a discrete signal to the aircraft indicating systemwhen the bleed control valve is in the position that allows maximumflow to the aircraft pneumatic system.
APU Available (28 VDC, 0.4 A)
The ECB provides a discrete signal to the AVAIL light in the start
switch when the APU has completed the start sequence and is readyto load.
Start in Progress (28 VDC, 0.1 A)
The ECB transmits a discrete signal to the ON light in the start switchto indicate a start is in progress
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This contactor is energized by means of a discrete signal. The signalis supplied through a FET device in the ECB.
Aircraf t Relay (ground, 0.4 A)
The aircraft relay is activated by a closed contact to ground throughthe ECB. The aircraft relay is activated when the ECB is energizedand no stop command is present.
to indicate a start is in progress.
The light is "ON" from the beginning of the start until the "APU
available" light turns on.
Fault (28 VDC, 0.2 A)
The ECB transmits a fault discrete signal to the aircraft for allshutdowns.
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ELECTRONIC CONTROL BOX - DESCRIPTION (7)
Discrete and Digital Outputs (to the aircraft) (continued)
Flap Open Command (28 VDC, 3.5 A)
The ECB provides a power output for opening the air intake flap. Theflap open command is emitted through a FET device in the ECB.
This output is protected against overload and short circuits.
Flap Closed Command (28 VDC, 3.5 A)
The ECB provides a power output for closing the air intake flap. Theflap closed command is emitted through a FET device in the ECB.
This output is protected against overload and short circuits.
• ARINC 429 input from ECS: It is used by the ECB toreceive specific data from the Environmental ControlSystem (i.e. ECS demand signal, ECS valve status word,etc...)The ECS demand signal is used in the control of the IGV's.The ECS valve status word informs the ECB of the numberof air conditioning packs currently supplying air
• ARINC 429 CFDS output: The ARINC 429 output
transmits data to the CFDS, ECAM (Electronic Centralized Aircraft Monitoring) and ACMS (Aircraft ConditionMonitoring System)
- One RS 232 C interface: This interface is accessible on the rear ARINC connector and on the front face connector.
HSPS CT/NOV.. 2006 Page 6.36HAMILTON STANDARD PROPRIETARY
HARDWARE DESCRIPTION
ELECTRONIC CONTROL BOX - DESCRIPTION (9)
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ELECTRONIC CONTROL BOX - OPERATION (1)
General
The operating phases are:
- Power up
- Watch state
- Start preparation state
- Starting state
- Run state
- Cool down state
Sh td t t
Power Up State
GeneralWhen the APU master switch is selected to ON, the ECB enters thePOWER UP state.The POWER UP state lasts approximately 3 sec.OperationThe ECB checks that outputs are not energized except those thatare required.
The ECB enters self test.The ECB is able to recognize and record the occurrence of start oremergency stop signals.Upon receipt and validation of the start signal, the "start in progress"output is energized.The requirement to activate the "start in progress" output alsoapplies to the WATCH state.In case of an emergency stop signal being received the ECB closes
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- Shutdown state In case of an emergency stop signal being received, the ECB closesthe air intake and deactivates the aircraft relay output once the air
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ELECTRONIC CONTROL BOX - OPERATION (2)
Watch State
General
After completion of the POWER UP state the ECB automaticallyenters the WATCH state.
Operation
The ECB is able to recognize and record the occurrence of start oremergency signals.
Upon receipt of an emergency stop signal the ECB closes the airintake and deactivates the aircraft relay output once the air intake isclosed.
The ECB self tests as required
Start Preparation State
General
Upon receipt of the start command, the ECB enters the STARTPREPARATION state.
Operation
During this state the flap actuator position, the oil level and therotation speed is checked. If the speed is greater than 7%, the startcommand will be inhibited until the speed is less than or equal to 7%.
The ECB enters the START PREPARATION state automaticallywithout requiring a new start command.
HSPS CT/NOV.. 2006 Page 6.44HAMILTON STANDARD PROPRIETARY
STARTING STATE - FUEL CONTROL
ELECTRONIC CONTROL BOX - OPERATION (4)
Use or disclosure of this data is subject to therestriction on the title page of this document.
ELECTRONIC CONTROL BOX - OPERATION (5)
Run State- Fuel and Load Compressor Control
General
Upon completion of starting, three main functions are activated:
- Speed control
- Load compressor surge control
- EGT control.
Speed Control - General
The purpose of speed control is to maintain the APU at 100% speedunder all load conditions. This is accomplished by the fuel controlunit increasing or decreasing fuel flow automatically when APU loadchanges occur
Load Compressor Surge Control- General
This function prevents load compressor surge. This is accomplishedwhen the bleed switch is ON.
EGT Control - General
To prevent EGT over temperature during load compressor operation,the ECB will automatically move the IGV's to decrease airflow and
reduce the work load on the power section.
The AC generator output has priority overload compressor operation.
RUN STATE - FUEL AND LOAD COMPRESSOR CONTROL - GENERAL
ELECTRONIC CONTROL BOX - OPERATION (5)
Use or disclosure of this data is subject to therestriction on the title page of this document.
ELECTRONIC CONTROL BOX - OPERATION (6)
Cool Down State
General
This function allows the APU to operate in a no-load condition beforeentering the shutdown state.
When the APU master switch is selected to OFF, all loads areremoved (IGV's closed, Bleed Control valve to discharge).
If the APU was providing bleed air at this time, the APU will continueto run in a cool down mode for a maximum time of 2 minutes.
The cool down mode time limit can vary from 0 to 2 minutes. Thetime limit depends on when the APU bleed switch is turned off priorto selecting the APU master switch to OFF.
At the end of the cool down mode (if any) the operation enters the
Use or disclosure of this data is subject to therestriction on the title page of this document.
ELECTRONIC CONTROL BOX - OPERATION (7)
Shutdown State
General
The APU enters the shutdown state after a normal shutdown or afault shutdown occurs.
Note: The APU can be re-started during the shutdown state. Thisis accomplished by cycling the master switch OFF to ON andthen selecting the APU start switch to ON.
The ECB does not close the flap and the APU automaticallyre-starts when 7% speed is reached.
Use or disclosure of this data is subject to therestriction on the title page of this document.
ELECTRONIC CONTROL BOX - OPERATION (8)
Condition Monitor ing Data
General
For long term trend monitoring, the APU control system records theengine operating parameters.
Operation
APU conditioning monitoring parameters are taken during operationof the APU. The ECU does not store this information but it may beretrieved from the Aircraft Integrated Data System (AIDS) if thissystem is installed.
The following parameters are:
- Exhaust Gas Temperature °C
- Engine speed %
In addition, the ECB records:
- APU operating hours (in one minute increments from speed > 55%until the 3-way solenoid valve is de-energized.
- Number of starts (1 start = EGT rise detected + speed > 30%)
- ECB operating hours (in one minute increments, from ECB powerON to ECB power OFF).
The condition monitoring data is associated with the engineidentification (ID) number, ECB serial number.
Note 1: The condition monitoring parameters are not taken wheneither the inlet pressure or temperature sensors are faulty
Use or disclosure of this data is subject to therestriction on the title page of this document.
Engine speed %
- Engine inlet pressure PSIA
- Engine inlet temperature °C
- Fuel flow LB/HR
either the inlet pressure or temperature sensors are faulty.
Note 2: If the engine ID module has been determined failed, the APU system operating history data will be associated withthe last valid engine I D number.When a new engine ID number occurs, it is used withouterasing the previously recorded historical data.The oldest data is overwritten by the new data as it isrecorded.The ECB records the condition monitoring data associated
with the last APU cycle and the data is available via the ARINC 429 link.
• Frequency signal range: 0 to 24 KHz; 0 to 50 volts.
Operation
The phonic wheel rotates with the rotor assembly, as the teeth passby each speed sensor they generate a voltage. The voltage isproportional to the speed of the phonic wheel. The signal is sent tothe ECB for speed indication and system control.
The ECB will calculate the average signal of the two speed sensors.
In the event a signal difference of 5% or more occurs, the ECB willselect the sensor indicating the highest value.
APU speed indication is displayed on the lower ECAM when the APU system page is selected.
Use or disclosure of this data is subject to therestriction on the title page of this document.
EGT is lower than 120 C (250 F)
- EGT is higher than 1200°C (2200°F).
The ECU will calculate the average signal of the two thermocouples.In the event a signal difference of 121°C (250°F) or more occurs, theECB will select the thermocouple indicating the highest value.
APU exhaust gas temperature indication is displayed on the lower
Use or disclosure of this data is subject to therestriction on the title page of this document.
MONITORING SYSTEM - GENERAL
General
This system gives information about the APU actual status, foroperation and maintenance.
Description
Indication of operating parameters
The APU operating parameters are displayed on the lower ElectronicCentralized Aircraft Monitoring (ECAM) when the APU system pageis selected.
Maintenance and fault isolation
The ECB provides maintenance and fault information to the aircraftCentralized Fault Display System (CFDS). This information isdisplayed on the Multi-function Control and Display Unit (MCDU) inthe flight deck.
Warning messages
Warning, caution and indicating lights
MASTER WARNING, MASTER CAUTION and annunciator lightsprovide visual warning indications.
A FAULT light is incorporated in the APU master switch button, APUGEN button and APU BLEED button.
There are also the following lights:
- APU "ON" light in the APU master switch
- APU "START / ON" and APU "AVAILABLE" light in the APU startbutton
- APU GEN "OFF" light in the APU GEN button
- APU BLEED "ON" light in the APU BLEED button
- APU fire lights on the external control panel and in the flight deck.
Use or disclosure of this data is subject to therestriction on the title page of this document.
Ignition Exciter
The ignition exciter is located on the left side of the APU. The exciteris a capacitor-discharge unit that uses 28V DC to provide anintermittent high voltage output to the two ignitor plugs.
Use or disclosure of this data is subject to therestriction on the title page of this document.
Ignition exciter energized to provide ignition to the two ignitorplugs.
Starting Cycle
the APU is shut down manually or automatically the 3 way solenoidvalve is de-energized closed. The closed valve shuts off the fuel tothe fuel injectors.
Use or disclosure of this data is subject to therestriction on the title page of this document.
IGNITORS AND IGNITOR CABLES
Function
There are two ignitor plugs used to ignite the fuel in the combustorchamber during start up of the APU. They are connected to theignition exciter by two shielded ignitor cables.
Location
The two ignitor plugs are located on the combustor housing:
- One at 5 'o'clock
- One at 9 'o'clock.
Note: Location is looking at the combustor housing rear view.
Use or disclosure of this data is subject to therestriction on the title page of this document.
AIRCRAFT/APU HARNESS (2)
Description (continued)
APU eng ine harnessThe engine harness is connected to three firewall connectors, theyare identified as (P-1, P-2 and P-3).P1 connector:- PMG- 3 way solenoid valve- Ignition exciter- Starter Motor (low voltage sense signal)
- Bleed Control Valve LVDT- Gearbox de-oiling valve- Oil filter switch indicators- Low oil pressure switch- Oil level sensor- Low fuel pressure switch- Generator high oil temperature sensor- AC generator current transformers.
P2 connector:- Load compressor discharge pressure sensors- IGV actuator (servo valve and LVDT)- BCV actuator (servo valve)- Fuel servo valve- Speeds sensor 1 and 2- Oil temperature sensor- EGT sensor 1 and 2
- Engine ID module- Air inlet pressure and temperature sensor.P3 connector:- AC generator PMG- AC generator excitation control.
Use or disclosure of this data is subject to therestriction on the title page of this document.
AIRCRAFT/APU HARNESS (3)
Description (continued)
Starter motor electrical power supply cables
The starter motor DC power supply is provided by the aircraftbatteries or the Transformer Rectifier Unit (TRU).
The supply is controlled by two contactors in series (backup andmain start contactors). The power cables link the start contactorsdirectly to the starter motor (+ and -cables).
AC generator harness
The AC generator connector P-4 is part of the engine harness. Theconnector provides the following signals:
- AC generator oil temperature and control signals through the P-1engine harness connector
- AC generator PMG signal and exciter field control through the P-3engine harness connector.
The four AC generator cables are connected to the aircraft electricalbuss system. Three of the cables provide AC power and the fourthcable is a neutral.
Use or disclosure of this data is subject to therestriction on the title page of this document.
AC GENERATOR - GENERAL
Function
The AC generator (Alternating Current Generator) provides electricalpower to the aircraft systems.LocationThe AC generator is mounted on the front face of the gearbox.Type- Brushless- 3 phases- Oil cooled.Main Features
- Nominal power: 90 kVA- Output: 115 V, 400 Hz- Rotation speed: 24 034 RPM at 100 % APU speed- Direction of rotation: Clockwise viewing the pad- Weight: approx. 22.7 kg (50 lbs).
Interfaces
- Oil system (lubrication, cooling)- Generator Control Unit (GCU)- Electronic Control Box (ECB).Main Components- Permanent Magnet Generator- Current transformers- High oil temperature sensor (HOT).
Use or disclosure of this data is subject to therestriction on the title page of this document.
EXHAUST SYSTEM
Function
The exhaust system directs the APU exhaust gasses overboard.
Location
The system is installed in the tail cone between the APU exhaustand the end of the tail cone.
System Components
- The exhaust pipe
- The exhaust muffler
- The insulation
- The sealing ring.
The exhaust pipe is mounted on rails that are attached to the insideof the tail cone.
This allows the exhaust pipe to be disconnected from the APU andmoved rearward to provide additional clearance during removal andinstallation of the APU.
Use or disclosure of this data is subject to therestriction on the title page of this document.
EXHAUST SYSTEM
DRAIN SYSTEM (1)
Function
The APU drain system provides drains from various components.The fluids are collected and drained overboard through the drainmast.
The fuel control unit, BCV actuator and IGV actuator use a commondrain to the aircraft drain tank. Fluids are siphoned from the draintank, into the drain mast and then discharged overboard when theaircraft is in flight.
The other common and single drains flow directly into the drain mastand then discharge overboard.
Use or disclosure of this data is subject to therestriction on the title page of this document.
INSPECTION AND CHECKS
Visual Inspections
Opening the APU compartment for corrective maintenance orservicing provides the opportunity to visually inspect the APU forsecurity, leaks, and warning indicators. The following arerecommended inspection items:
- Engine mounts
- Engine Components and Fluid lines
- Oil Quantity and Magnetic Drain plug
- Oil and Fuel Filter impending blockage Indicators
- Electrical harness and Connectors
- Engine Air Inlet Plenum
- Engine Combustor Housing and Exhaust System.
Borescope Inspection
The APU internal components may be inspected by using a flexibleborescope. To rotate the APU internal components, the cooling faninlet duct may be removed to allow manual rotation of the fanimpeller.
The following components can be inspected with the APU installed inthe aircraft.
- Load compressor impeller and guide vanes
- Power section impeller
- Combustor, viewed through the ignitor and fuel injector bosses
- First stage turbine wheel
- Second stage turbine wheel.
Refer to the Aircraft Maintenance Manual for borescopeprocedures.
Use or disclosure of this data is subject to therestriction on the title page of this document.
GENERAL DESCRIPTION
The centralized fault display system (CFDS) provides electronicsystem fault detection, fault storage, fault displays, operationaltesting and troubleshooting from the flight deck multi-purpose controland display unit (MCDU).
CENTRALIZED FAULT DISPLAY AND INTERFACE UNIT
The CFDIU provides the interface between the APU electroniccontrol box (ECB) and the MCDU for screen display of APU faultinformation.
MULTIPURPOSE CONTROL AND DISPLAY UNITS
The Multipurpose Control and Display Unit (MCDU) is a display unitand a keyboard used by the CFDS to display and interrogate faultsand to initiate system tests. Both MCDU's (Multipurpose Control andDisplay Unit) are connected to the CFDS.
Only one MCDU can be used when interrogating the CFDS.
CFDIU/PRINTER INTERFACE
The CFDIU sends MCDU screen information and print commands tothe optional printer automatically or on request.
CFDIU/ACARS INTERFACE
The CFDIU sends fault information to the optional ACARS for down-linking when selected manually by the MCDU operator or when anuplink request is received from a ground station via the ACARSmanagement unit.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT WARNINGS
Flight Deck Fault Warnings are identified as Class 1, 2 and 3.Class 1 faults are further identified as Level 3, 2 and 1.
CLASS 1
- Level 3- This level corresponds to warnings needing immediate
action.- Level 3 warnings are associated with:
- Repetitive chime- Warning message on upper ECAM display- Master Warning Light flashing Red
- APU systems page on lower ECAM display
- Level 2- This level corresponds to abnormal situations needing
immediate awareness but not immediate action.- Level 2 warnings are associated with:
- Single chime- Master caution steady Amber light- Warning messages on upper ECAM display
- APU system page on lower ECAM displayLevel 1- This level corresponds to reduced bleed air performance- It is associated with low or zero duct pressure- Low or zero duct pressure is visible (lower ECAM display) on
the engine system page during MES or on the APUsystem page.
CLASS 2
- These failures are indicated on the STATUS page, under the title
of MAINTENANCE.- They are also accessible through the CFDS.
indicates that the STATUS page is not empty andflashes in flight phase 10 on the upper ECAM display.STS
CLASS 3
- These failures are only accessible through the CFDS. No APUfault warnings are displayed.
STATUS (STS) indication is an "attention getter" on the upper ECAMdisplay.
STATUS (STS) indicates that a status message (class 1 or class 2fault) is present and further maintenance action may be required. Aflashing STS indication occurs after the second engine shutdown inFlight Phase 10. It is necessary to press the STS key on the ECAMcontrol panel for the STATUS page to appear on the lower ECAMdisplay.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT WARNINGS
ECAM CONTROL PANEL
The control panel allows selection of the aircraft system pageincluding APU. Pressing the Status (STS) key presents the STATUSpage on the lower ECAM display. The STATUS page will indicate thefaulty aircraft systems under the INOP SYS (Class 1 Fault) andMAINTENANCE (Class 2 Fault) titles.
Use or disclosure of this data is subject to therestriction on the title page of this document.
MULTIPURPOSE CONTROL AND DISPLAY UNITS
The Multipurpose Control and Display Unit (MCDU) is a display unitand a keyboard used by the CFDS to display and interrogate faults
and to initiate system tests. Both MCDU's (Multipurpose Control andDisplay Unit) are connected to the CFDS.
Only one MCDU can be used when interrogating the CFDS.
Pressing the MCDU MENU key, the MCDU menu page is displayed,and any one of the systems connected to the MCDU can beselected.
A multiple page display is indicated by an arrow (∇) in the right uppercorner of the screen. In this case the NEXT PAGE key must be usedto provide access to the various pages of the display. The NEXTPAGE key can be used as long as the arrow is displayed.
Twelve line select keys, six on the left and six on the right, provideaccess to a page or a function. The line select keys permit access toa page or a function when these prompt symbols appear (>, <). Theyare identified as 1L to 6L on the left, and 1R to 6R on the right.
If a flight deck printer is installed and operational, the current MCDUdisplay screen may be printed by pushing the PRINT line select key.
APU FAULT OPERATION
SYSTEM SELECTION
The MCDU MENU page is displayed when the MCDU MENU key ispushed.
Selecting the CFDS line select key will then display CFDS menu.
Pressing the SYSTEM REPORT/TEST line select key displays theSYSTEM REPORT TEST menu.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
SYSTEM REPORT/TEST
When SYSTEM REPORT/TEST is selected while on the ground, asystems menu is displayed. The APU selection is located on thesecond page of the menu. Pushing the NEXT PAGE key will display
APU.
Selection of the RETURN line select key on the first page will displayMCDU MENU.
Selection of the RETURN line select key on the second page will
display the first page of SYSTEM REPORT/ TEST.
APU
There are two APU menu pages available. The first page displaysthe following information:
LASTLEGREPORT
PREVIOUSLEGREPORT
LRUIDENTIFICATION
SYSTEMSELF-TEST
SHUTDOWNS
The second page of the APU menu when selected by theNEXTPAGE key, displays the following information:
APUDATA/OIL
CLASS3FAULTS
Selection of the RETURN line select key on the First Page willdisplay the Second Page of SYSTEM REPORT/TEST.Selection of the RETURN line select key on the (Second Page) willdisplay the (First Page) of APU menu.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
APU LAST LEG REPORT
The Last Leg Report displays fault information delivered by theCFDS system. It can store up to 40 failures during the Last Leg. TheLast LEG Report displays only class 1 and 2 faults and contains theidentity of each LRU, its corresponding Date, GMT, ATA chapter andFault Code Number (FCN) for each fault occurrence. The FunctionalIdentification Number (FIN) appears after each LRU. In the case ofmultiple failures, the failures will be displayed in chronological orderwith two failures per page. A maximum count of four intermittentfaults will only be displayed in the same flight leg. Prompts (>) at the
end of each LRU message indicate the line select key to display the APU FAULT CONDITIONS screen. All of the Last Leg Report isprinted when the PRINT line select key is pushed, even if it containsseveral pages.
Selection of the RETURN line select key will display APU menu,(First Page).
APU PREVIOUS LEGS REPORT
The Last Leg Report contents are transferred into the Previous LegReport with each new flight leg. The report can store up to 200failures over the last 63 flight legs. Each LRU is identified along withthe Aircraft identification, Leg number, Date, GMT, ATA chapter andFault Code Number (FCN) for each fault occurrence. The FunctionalIdentification Number (FIN) appears after each LRU. In the case ofmultiple failures, the failures will be displayed in reversechronological order with two failures per page. Prompts (>) at theend of each LRU message indicate the line select key to display the
APU FAULT CONDITIONS screen. Only the PREVIOUS LEGSREPORT displayed page will be printed when the PRINT line selectkey is pushed.
Selection of the RETURN line select key will display APU menu,(First Page).
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
APU LRU IDENTIFICATION
The LRU Identification page displays the ECB Part Number, ECBSerial Number and the ECB Software Version.
The ECB part number is adjustable and is stored in the NVM. Thebuilt letter (H) following the part number is adjustable from A to Z.
Selection of the RETURN line select key will display APU menu,(First Page).
APU SYSTEM SELF TEST
A self test of LRU's may be initiated through the CFDS. The test canonly be accomplished when the APU is not running and the MasterSwitch is ON. In case of no failures or when the test is in progress, orlack of availability of the test function, the message of TEST OK, INPROGRESS and NOT AVAILABLE will be displayed respectively.Detected failures will be displayed with their ATA Chapter and FaultCode Number (FCN). The Functional Identification Number (FIN)appears after each LRU. In the case of multiple failures, the failureswill be displayed in chronological order with two failures per page.
Only the SYSTEM SELF TEST displayed page will be printed whenthe PRINT line select key is pushed.
Selection of the RETURN line select key will display APU menu,(First Page).
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
APU SHUTDOWNS
The Shutdowns page contains its corresponding Date, GMT, FaultCode Number (FCN), shutdown message and the identity of theLRU. The Shutdowns will be displayed in reverse chronological orderwith only one shutdown per page. Prompts (>) at the end of eachLRU message indicate the line select key to display the APU FAULTCONDITIONS screen.
In case there are no shutdowns, the message of NO SHUTDOWNSwill be displayed. Only the SHUTDOWNS displayed page will be
printed when the PRINT line select key is pushed.
Selection of the RETURN line select key will display APU menu,(First Page).
APU DATA/OIL
APU Data/Oil page contains the Date, APU Serial Number (S/N),Hours, Start Attempts, Start Cycles and Oil level status. Prompts (>)at the end of the message indicate the line select key to display the"Update APU Data" screen.
Selection of the RETURN line select key will display APU menu,(Second Page).
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
APU CLASS 3 FAULTS
Class 3 Faults can be stored up to 200 failures over the last 63 flightlegs. Each LRU is identified along with the Aircraft identification, Legnumber, GMT, ATA chapter and Fault Code Number (FCN) for eachfault occurrence. The Functional Identification Number (FIN) appearsafter each LRU. In the case of multiple failures, the failures will bedisplayed in reverse chronological order with two failures per page.Prompts (>) at the end of each LRU message indicate the line selectkey to display the APU FAULT CONDITIONS screen.
In case there are NO CLASS 3 FAULTS detected, the message NOFAULTS will be displayed. Only the CLASS 3 FAULTS displayedpage will be printed when the PRINT line select key is pushed.
Selection of the RETURN line select key will display APU menu,(Second Page).
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
UPDATE APU DATA
Selection of this screen allows the operator to update the APU hoursand cycles when the ECB or the APU is changed.The Update APU Data screen is only accessible by prompts (>) fromthe APU Data/Oil Screen. The Update APU Data screen displays the
APU Serial Number (S/N), and current values of Hours and Cycles.The new values of hours and cycles can be entered by use of MCDUkeyboard. After line key 3L is pressed (Prompt <) the screen willdisplay the new values for APU hours and cycles when the ECB or
APU is changed.
The HOURS and CYCLES will be printed when the PRINT line selectkey is pushed.
Selection of the RETURN line select key will display the APUDATA/OIL screen.
Use or disclosure of this data is subject to therestriction on the title page of this document.
HSPS CT/NOV 2006 Page 12 23
APU FAULT OPERATION
FAULT CONDITIONS
The Fault Conditions screens are only available by the line selectkeys indicated by prompt (>) on the Last Leg Report, Previous LegsReport, Shutdown and Class 3 fault screens. Selection will displaythe Fault Conditions screen-1 or screen-2. Each screen will displaythe APU S/N, Date, GMT and the identity of the LRU. The FunctionalIdentification Number (FIN) appears after the LRU.Engine data from the fault data stored in the Electronic Control Boxnon-volatile memory will also appear on each screen. (See Screen-1and Screen-2 Parameters on page 12-24).
One screen at a time is displayed. To select screen-2 when screen-1is displayed or select screen-1 when screen-2 is displayed it isnecessary to press the NEXT PAGE key on the Multipurpose Controland Display Unit (MCDU).
Only the screen that is displayed (Screen-1 or Screen-2) will beprinted when the PRINT line select key is pushed.
Selection of the RETURN line select key will display the screen that
was shown preceding selection of the Fault Selection Screens.
Use or disclosure of this data is subject to therestriction on the title page of this document.
HSPS CT/NOV 2006 Page 12 25
FLIGHT DECK PRINTER
The Printer provides onboard printouts concerning various aircraftsystems, one at a time.
MANUAL PRINT
In manual mode, prints of the MCDU screen display are printedwhen the PRINT line select key is pushed.
AUTOMATIC PRINT
In flight phase 10, the Post Flight Report will be automaticallyprinted. The Post Flight Report is the sum of the LAST LEGREPORT and the LAST LEG ECAM REPORT.
A list of ECAM Warnings and Fault Messages with the associatedtime and ATA chapter references are provided on the printed tape.
Use or disclosure of this data is subject to therestriction on the title page of this document.
HSPS CT/NOV. 2006 Page 12.27
FAULT CHARTS
The following Fault Charts provide the information that will be sent tothe CFDS by the ECB in the event of a fault.
The information appears in the Fault Chart columns located underthe following headings:
Version 5.0
MCDU LRU MessageMCDU Shutdown MessageFault CodeFault ClassLRU ID
ATA ChapterSystem Severity level
SYSTEM SEVERITY LEVEL
System Severity Levels are not sent to the CFDS. It is presentedhere only as information.
Once a fault has been identified with a switch or a sensor thatcomponent will no longer be used for further fault detection, isolationor control until the fault is no longer present. Detected faults can becleared and a restart may be possible once the master switch iscycled.
The troubleshooting system is designed to provide additional
information to aid in the maintenance and repair of the AuxiliaryPower Unit (APU) by downloading the Electronic Control Box (ECB)located in the aircraft aft cargo compartment.Maintenance information is stored in the nonvolatile memory of theECB and can be retrieved and analyzed by downloading into alaptop computer. The computer displays information andrecommended actions from the following stored data:
CONDITIONING MONITORING DATA
This data consists of engine parameters taken at each engine startand shutdown. Data is provided for the last twelve engine run cycles.
FAULT DATA
The data consists of maintenance and fault messages for class 1,class 2 faults and class 3 faults.
REQUIRED HARDWARE
Downloading of the ECB requires the following equipment:
Laptop computer or Personal Computer (PC) with at least3MB of free hard disc space, a modem and a Windows 95 orlater operating system.
A special interface cable is required to connect theComputer to the ECB. The interface cable (P/N AGE 70021)is available by contacting Hamilton Sundstrand.
To download and diagnose fault data, refer to APIC SIL APS32-
0049-47 for in-depth instructions.
Basic Steps:• Connect the interface cable from the computer to the ECB.• Power-up computer.• Select Diagnose on the tool bar.• Enter operators name on the Setup screen.• APU master switch ON (APU not running.)• Select Continue on the Setup screen.
The computer screen displays Class 1, Class 2 faults and Class 3faults. The screen will download and provide a file automatically forreview. (See example on page 13.6.)
Select the Most Recent scroll bar on the screen to scroll through thevarious faults.Each fault or fault combination is provided with a fault descriptionand recommended action.
With the Real-Time Data monitoring screen displayed, select AnalogI/O, Speed/Temp, or Discreet Inputs. Each selection displays ascreen that provides real time data. The data is viewed at the bottomof the screen when a data box is selected.
Note: The more data boxes selected the longer it takes for theinformation to appear. Select data that is related to thespecific fault for a faster response time.
BASIC STEPS:• Connect the interface cable from the computer to the ECB.• Power-up computer.• Start and run APU.• Select data box.• Select Start Monitoring.• Select Stop Monitoring after data has been taken.
Selecting Save Data at the bottom of the screen and selecting a filename allows the data to be saved. (See page 13.9 and example onpage 13.10.)
Use or disclosure of this data is subject to therestriction on the title page of this document.
PREFACE
GENERAL DESCRIPTION
The APS 3200 Auxiliary Power Unit Maintenance Training Course,
developed by the Customer Service Training Group of HamiltonSundstrand Power Systems, is designed to give the student anunderstanding of the various components of the Auxiliary Power Unit(APU) and their functions. This course also provides routinemaintenance and troubleshooting.
STUDENT WORKBOOK
This workbook is intended for the “limited” purpose of providing
component familiarization, general data, and support information forthis maintenance course.
This is an uncontrolled document and will not be updated or revisedon a regular basis. Specific values given in this document such asspeed, temperature, and pressure are provided for the purpose ofillustration and are not necessarily representative of the true valuesof the APS 3200 APU.
FAA AND AIRCRAFT MANUFACTURER APPROVEDPUBLICATIONS
The Airline is provided a variety of FAA and Aircraft Manufacturerapproved publications for the APS 3200 APU. These publicationsare:
Aircraft Flight Crew Manuals
Aircraft Maintenance Manuals
Engine and Component Maintenance Manuals
Service Bulletins
Chapter 49 of the aircraft maintenance manual presents detailed APU and LRU removal and installation procedures plus maintenanceand servicing techniques that can be accomplished at the flight-line.Careful study of Chapter 49 will add to the student's expertise introubleshooting and maintaining the Hamilton Sundstrand APS 3200
OIL CAPACITY 3.9 L (4.16 Qts) (add)5.4 L (5.72 Qts) (full)
OIL TEMPERATURE (SHUT DOWN) 135°C (275°F) Lubrication system185°C (365°F) AC Generator
APPROVED OIL SPECIFICATION:
MIL-PRF-7808
MIL-PRF-23699
CAUTION:
DO NOT MIX OR SUBSTITUTE OIL SPECIFICATIONS. USE ONLY ONE OF THE APPROVED OILS. IF THE OIL SUPPLY IS LOW AND THE OIL BEING USED IS NOT AVAILABLE, DRAIN THE OIL SUMP AND CHANGE THE OIL FILTER. SERVICE THEOIL SYSTEM WITH AN APPROVED OIL.
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APS 3200 - DESCRIPTION (1)Power Unit
The APU consists of a gas turbine engine (Power Section) whichdrives:
- A load compressor
- And an AC generator (alternator) through a gearbox.
The APU is of modular design. It has three modules:
- The power section
-
The load compressor
- The gearbox.
A common air inlet supplies the load compressor, the cooling fan andthe power section.
Power Section
The power section is a single spool gas turbine engine whichconsists of:
- A centrifugal compressor
- A reverse flow combustor chamber
- A two stage axial flow turbine.
Load Compressor
The load compressor is a single stage centrifugal compressor drivendirectly by the power section. Variable inlet guide vanes are used for
airflow and exhaust gas temperature control.
Gearbox
The gearbox, also driven by the power section, is attached to theload compressor. The gearbox provides the drive at the correctspeed for the AC generator and the APU mechanically drivenaccessories.
Electronic Control Box
The ECB provides control and monitoring of the APU and is locatedin the aircraft rear cargo compartment.
Power section provides the shaft power to drive the loadcompressor and the gearbox.
Power is produced by transforming the energy contained in theambient air and the fuel through thermodynamic cycle: compression,combustion, expansion.
- Compression of the air in the single stage centrifugal compressor
- Combustion of the air-fuel mixture in the reverse flow combustorchamber
- Expansion of the burned gases across the two stage axial flowturbine to drive:
• The power section impeller
• The load compressor impeller
• The gearbox.
The load compressor supplies compressed air to the aircraftpneumatic system. The air is compressed by a single stagecentrifugal impeller and uses variable inlet guide vanes to control theair flow. The compressed air is delivered through a scroll to the bleedcontrol valve.
The gearbox provides the drive for the AC generator, andaccessories for APU operation.
The AC generator that provides electrical power for the aircraftsystems.
The Electronic Control Box receives various signals from theaircraft and the APU to operate and monitor the APU.
The electronic control box controls the following:
- Rotation speed (N) (fuel flow)
- Load compressor surge protection (bleed control valve)
- Exhaust Gas Temperature (EGT) (inlet guide vanes).
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POWER UNIT - DESCRIPTION (1)
The first part of the description deals with the APU rotating assemblyand the second part will consider the modular design of the APU.
The following main components are considered in this description:gearbox, air intake plenum, load compressor and power section.
Gearbox
The gearbox located at the front of the APU provides the mechanicaldrive for the AC generator and the accessories required for the APUoperation. The oil sump is also part of the gearbox.
Load Compressor
The load compressor is driven by the power section and providescompressed air to the aircraft pneumatic system. It is a centrifugalimpeller that has variable inlet guide vanes to control the air flowoutput.
Air Inlet Plenum
The plenum is located between the load compressor and the power
section. The plenum directs the air supply to the power section, loadcompressor and the oil cooling system.
Power Section
The power section provides mechanical shaft power to drive the load
compressor and the gearbox.
The power section comprises:
- A single stage centrifugal impeller
- A reverse flow combustion chamber
- A two stage axial flow turbine
- An exhaust system.
The main rotor assembly is supported by two bearings: A ballbearing at the front of the load compressor, a roller bearing at therear of the turbine.
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POWER UNIT - OPERATION
General
The power section produces mechanical shaft power for APU
operation.
This mechanical power is used to drive:
- The load compressor which supplies compressed air
- The AC generator which supplies electrical power
- Accessories required for the operation of the APU.
Power Section Operation
The air enters the power section through the aircraft air inlet and the APU plenum.
In the plenum, this air is divided into two flows; one for the loadcompressor and one for the power section.
The power section air is directed to the centrifugal impeller which
increases the air pressure.
The air is then admitted to the combustion chamber, mixed with thefuel and burned to provide a continuous combustion process. Thegases are expanded across the turbines that transforms the gasenergy into mechanical energy.
The gases are then expelled overboard through the aircraft exhaustsystem.
Load Compressor Operation
The load compressor is driven by the power section and produces airflow to the aircraft pneumatic systems.
Gearbox Operation
The gearbox is driven by the power section to operate the APUaccessories and the AC generator.
Electronic Control Box (ECB)
The ECB provides control and monitoring of the APU.
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AIR INLET PLENUM - GENERAL
Location
The inlet plenum is located between the load compressor and thepower section.
Main Features
- Acoustically treated part
- Shop replaceable unit
- Weight: approx. 7.5 kg (16.5 lbs).
Main Components
The plenum consists of two parts, upper and lower, which areconnected by quick disconnect latches.
The lower part interfaces with the aircraft air inlet system. The airinlet to the plenum is provided with a screen made of stainless steelthat protects the APU internal components from foreign objectdamage.
The upper part has an outlet for air supply to the oil cooling system(supply to the oil cooler fan).
Construction
The plenum is of sandwich construction with a structural envelope,Nomex and felt metal. The structural envelope and Nomex are fireproof.
Operation
In the plenum, the air is separated into two flows by the splitter.
- One for the power section: 2.2 kg/s (4.8 lbs/sec.)
- One for the load compressor and cooling fan: 1.2 kg/s (2.6
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AIR INLET PLENUM - DESCRIPTION
Identification of the Air Inlet Plenum Components
- The lower part of the air inlet plenum interfaces with the APU airinlet system. It has a screen to protect the APU internal
components from foreign object damage.
The lower part incorporates noise treatment and a splitter whichseparates the air into two flows. It also provides the support for thefollowing components:
• The ambient air pressure and temperature sensors
• The differential pressure sensor
• The low oil pressure switch
• The ignition exciter.
- The upper part of the air inlet plenum is also noise treated.
The upper part has an oval outlet to supply air to the oil coolingsystem
- The quick disconnect latches secure the upper part and lowerpart of the air inlet plenum.
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LOAD COMPRESSOR - DESCRIPTION (1)
The first part of this description deals with the load compressorcomponents, the second part will consider the inlet guide vanescontrol mechanism and the third part the identification of all thecomponents.
Air Inlet Housing
The housing allows the passage of air to the load compressor andsupports the inlet guide vanes. It is made of aluminum alloy.
Compressor Impeller
The impeller is constructed of titanium alloy. The rear shaft of the
impeller is connected to the rotor intershaft using a curvic coupling.The front is supported by a ball bearing.
Compressor Shroud
The shroud houses the impeller and is constructed of steel alloy.
Compressor Diffuser
It consists of 19 cambered vanes made of steel alloy.
Scroll
The annular scroll provides the air outlet of the load compressor. It iscast aluminum.
The scroll housing provides passages for static air pressure to theload compressor discharge pressure sensor.
Bearing
A ball thrust bearing supports the front shaft of the load compressor.It is mounted in the load compressor housing.
Bearing Seals
Oil that is used to lubricate the front bearing is prevented fromentering the impeller area by a floating carbon seal and a labyrinthseal.
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LOAD COMPRESSOR - DESCRIPTION (2)
Identification of Load Compressor Components
- The IGV assembly includes the variable inlet guide vanes, therack and pinion mechanism and the air inlet housing
- The compressor shroud houses the impeller.
- The load compressor impeller has main blades and splitterblades. The impeller is connected at the rear to the inter shaft bycurvic-coupling. The impeller front shaft is supported by the frontbearing.
- The scroll provides the air outlet of the load compressor. The
scroll also houses the load compressor diffuser.
- The front bearing is a ball bearing that supports the impeller frontshaft
- The labyrinth seal is pressurized with compressed air from thepower section impeller.
- The front bearing nut retains the front bearing and forms the
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LOAD COMPRESSOR - DESCRIPTION (3)
Inlet Guide Vanes
The Inlet Guide Vanes (IGV) consist of 24 vanes, made of titaniumalloy and mounted in the inlet housing.
Each inlet guide vane has a sector gear.
There are five guide vanes with holes in them. Three are located atthe 6:30 position, one at the ten o’clock and one at the two o’clockposition. The holes allow a minimum amount of air flow to the loadcompressor to prevent surging when the guide vanes are closed andthe APU is operating.
Control Mechanism
The mechanism controls the position of the vanes. The completemechanism consists of:
- The actuator
- The control rod
- The rack and pinion mechanism that moves the vanes.
The Actuator
The actuator is hydraulically operated. It uses fuel pressure meteredby an electrical signal from the electronic control box.
The Control Rod
The control rod is mechanically operated by the actuator.
The control rod is connected between the actuator and the inletguide vane assembly.
The Inlet Guide Vane Assembly
The inlet guide vane assembly consists of 24 sector gears engagedinto a common ring gear.
The ring gear is connected to the inlet guide vane control rod.
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LOAD COMPRESSOR - OPERATION
Air Inlet
The ambient air enters the APU through the aircraft air inlet and the APU plenum.
The plenum air is separated into three flows:
- Air for the power section
- Air for the oil cooling system
- Air for the load compressor.
The air for the load compressor passes through the inlet guidevanes; the flow of air depends upon the position (the angle) of thevanes. The air is then directed to the blades of the compressorimpeller.
Compression
As the air enters the blades of the rotating compressor impeller theair velocity increases.
The air leaves the tip of the blades at high velocity and flows throughthe diffuser vanes where velocity is transformed into pressure.
Delivery
The compressed air then flows into the scroll and delivered to thepneumatic system through a bleed control valve.
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POWER SECTION - COMPRESSOR - DESCRIPTION
Identification of Compressor Components
- The intermediate shaft is connected to the front of the loadcompressor impeller and to the rear of the power section
compressor impeller by curvic-couplings.
- The compressor housing houses the impeller and thecompressor shield.
The compressor housing is attached at the front to the air inlethousing and at the rear to the diffuser assembly and the combustorhousing.
- The impeller containment shield is mounted to the compressorhousing.
- The impeller has main blades and splitter blades. The impeller isconnected at the front to the intermediate shaft and at the rear tothe turbine by curvic-couplings.
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POWER SECTION - COMBUSTOR CHAMBER - GENERAL
Function
The combustor chamber burns the air-fuel mixture and delivers theresulting gas to the turbine.
Location
The combustor chamber is located in the middle of the powersection.
Type
Reverse flow, annular combustor chamber.
Main Features
- Fuel air ratio: 1/45
- Turbine inlet temperature: 1020°C (1868°F).
Main Components
- The combustor housing is made of steel alloy. It houses thecombustor chamber. It also has bosses for the mounting of fuel
injectors (3 pilot fuel injectors and 6 main fuel injectors) andigniters. The lower part of the external housing is provided with acombustor chamber drain valve.
- The combustor chamber is used for the fuel air mixturecombustion. The combustor chamber and the elbow are made ofheat resistant alloy and is provided with air holes and tubes.
- The heat shield acts as a shield between the bend assembly and
the impeller and directs the combustor gases to the turbines.
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POWER SECTION - COMBUSTOR CHAMBER -DESCRIPTION
Identification of Combustor Chamber Components
- The combustor housing houses the combustor chamber. It alsohas bosses for the mounting of the fuel injectors, the igniter plugs
and the combustor chamber drain valve.
- The combustor chamber has holes and tubes that allows air usedfor combustion and cooling to enter the combustor chamber.
- The bend assembly guides the burned gases from the combustorchamber to the inlet of the first stage turbine nozzle guide vane.
- The heat shield protects the diffuser holder plate of the power
section impeller.
The heat shield is located between the bend assembly and thediffuser assembly.
- The combustor chamber drain valve is threaded into the bottomof the combustor housing, this allows unburned fuel to drainoverboard. The valve is closed by air pressure in the combustorhousing.
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POWER SECTION - TURBINE - DESCRIPTION
Identification of Turbine Components
- The first stage nozzle guide vane has 22 vanes installed in frontof the first stage turbine wheel
- The first stage turbine wheel has 37 fir tree blades inserted into adisc and secured by blade locks.
The turbine wheel is connected to the rear of the power sectionimpeller and to the second stage turbine wheel by curvic-couplings
- The second stage nozzle guide vane has 26 vanes installed infront of the second stage turbine wheel
- The second stage turbine wheel has 31 fir tree blades insertedinto a disc and secured by blade locks. Vibration dampers arefitted between the blades.
The turbine wheel is connected to the first stage turbine wheel by acurvic coupling.
The rear of the second stage turbine wheel is supported by a rollerbearing
- The containment shield is located around the turbine wheels.
- The turbine housing is located between the containment shieldand the turbine.
The turbine housing is connected to the exhaust housing.
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POWER SECTION - EXHAUST - GENERAL
Function
The exhaust directs the exhaust gases to the aircraft exhaust pipe.
Location
The exhaust diffuser is located inside the APU exhaust housing.
Type
One piece, annular exhaust pipe.
Main Components
The exhaust housing is constructed of stainless steel and provides apassage for the exhaust gases. The housing also contains the rearbearing and struts that house oil pipes to the rear bearing.
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POWER SECTION - OPERATION (1)
The power section produces the shaft power through thethermodynamic cycle: compression, combustion, expansion andexhaust.
Compression
Ambient air is directed into the blades of the rotating impeller. The airthen flows through the divergent passages of the diffuser. (The airvelocity is transformed into pressure.)
Combustion
The compressed air is divided into two flows:
- A primary flow mixed with the fuel for combustion
- A secondary flow (dilution air) to cool the combustor and internalparts.
As a result of the continuous burning process, the pressuredecreases slightly whereas the velocity and the temperatureincrease.
Expansion
Expansion of the gases takes place across the two stages of theturbines, this transforms the gas energy into shaft power.
The gases flow through the nozzle guide vanes which increase thevelocity, then across the turbine blades. The aerodynamic forcescause the turbine wheels to rotate.
During expansion, the velocity of the gases increases and thepressure and temperature decrease.
Exhaust
The gases are then expelled overboard through the exhaust system.
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POWER SECTION - OPERATION (2)
The power section provides air flow to pressurize the APU labyrinthseals, to cool internal heated parts and balance rotor forces.
Pressurization
- Pressurization of Labyrinth Seals
Labyrinth seals are supplied with air pressure. A pressuredifference across the seals provide a non contact seal.
- Pressurization of Load Compressor Front Bearing
The pressurized air, bled from the outlet of the power sectionimpeller, flows through an external pipe to the labyrinth seal of theload compressor front bearing and the cooling fan labyrinth seal.
- Pressurization of Power Section Rear Bearing
The pressurized air, bled at the outlet of the power sectionimpeller, flows through the power section rotor assembly to therear bearing labyrinth seal.
Cooling
To prevent excessive heating of the parts subjected to thecombustion gases, a circulation of cooling air (bled at the outlet of
the power section impeller) is provided through the power sectionrotor assembly, and is directed by internal passages to the turbinewheel faces.
Balance of Forces
The shaft, the turbine wheels, and the compressor impellers aresubjected to axial forces resulting from the operation of the rotorassembly.
To reduce the forces on the bearings, air pressure is used on thebackside of the power section impeller.
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OIL SYSTEM - DESCRIPTION
Oil Sump
The oil sump is formed by the lower part of the gearbox.
The gearbox has a fill tube for gravity filling, an overflow drain, apressure fill connector and a sight glass.
The gearbox intermediate gear also functions as the air/oil separatorand provides air venting of the gearbox.
Oil Pumps
One lubrication pump and two scavenge pumps are driven by the
gearbox.
The pressure system is provided with a pressure relief valve locatedon the front of the gearbox.
Oil Filters
There is one filter in the lubrication line and one in the AC generatorscavenge line.
Both filters are the same and each have a filter element impendingblockage switch indicator. They are mounted on the lower front faceof the gearbox. The oil filter by pass valve for each filter is located inthe gearbox and is non adjustable.
Oil Cooler
The oil cooler cools the oil and has a by-pass valve.
De-oili ng Valve
The de-oiling valve is a solenoid valve located at the inlet of thepressure pump. When energized open, the valve prevents oil flowthus reducing the APU starting loads on the starter.
Monitoring Devices
- Low oil pressure switch
- High oil temperature sensor
- AC generator high oil temperature sensor
- Oil level sensor
- Oil level sight glass
- Oil filter impending blockage switch indicator on each oil filterassembly
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OIL SYSTEM – OPERATION
The main functions of the oil system are : oil supply, scavengereturn, venting and indicating.
Oil Supply
The lubrication pump draws the oil from the sump and delivers it tothe oil system. During starting, the de-oiling valve opens and air isdrawn into the pump to prevent oil flow. After de-oiling the oil flows tothe oil cooler, then to the filter.In the event oil flow through the filter becomes restricted, the switchindicator is activated. If the filter becomes blocked, the oil filterbypass valve will open and allow flow to the oil system.The oil pressure relief valve opens to regulate the oil systempressure. When the valve is open, some of the oil flow is bypassedback to the inlet side of the lubrication pump.
Scavenge Return
After lubrication, the oil returns to the gearbox sump by twoscavenge pumps:- One for the power section rear bearing that returns the oil directly
to the sump- One for the AC generator that returns the oil to the sump through a
filter.
Note: The front bearing and the gearbox are scavenged by gravity.
Scavenge Return
After lubrication, the oil returns to the gearbox sump by two
scavenge pumps:-One for the power section rear bearing that returns the oil directly to
the sumpOne for the AC generator that returns the oil to the sump through a
filter.Note: The front bearing and the gearbox are scavenged by gravity.
Venting
Oil mist in the gearbox is separated by a centrifugal air-oil separator.The gearbox is vented to the exhaust through an external pipe.
Monitoring-Low oil pressure switch-High oil temperature sensor- AC generator high oil temperature sensor- Oil filter impending blockage switch indicators- Oil level sensor
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ENGINE LUBRICATION (2)
Front Bearing Lubrication
Oil Supply
The lubrication for the rotor front bearing is provided by pressurizedoil from the gearbox oil system.
A jet located in the gearbox housing sprays oil between the front endof the load compressor shaft and the front bearing nut. (PhonicWheel)
The oil runs along the shaft, lubricates the quill shaft splines andenters the gap through the split inner races to lubricate the bearing.
Oil flow to the bearing is also provided by oil passages between thegearbox and bearing outer race to provide a squeeze film to dampenbearing vibration.
Scavenge and Return
After lubrication the oil is returned to the sump by gravity.
Sealing
Oil sealing of this assembly is by a floating carbon seal and alabyrinth seal using air from the power section impeller.
A drain cavity between the seals is vented overboard, into the APUdrainmast.
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AIR-OIL SEPARATOR
Function
The air-oil separator separates the oil from the air.
Location
The air-oil separator is located in the upper part of the gearbox.
Description
The air-oil separator is part of the gearbox intermediate gear.
The gear has a hollow shaft with radial drillings. The rear of thehollow shaft vents into a passage in the gearbox housing.
Operation
An air-oil mist is created in the gearbox when the APU is operating.
The oil is separated from the air by the rotating action of the gearboxintermediate gear. The oil returns to the gearbox sump by gravityand the air is vented through a pipe to the APU exhaust.
The gerotor is a positive displacement pumping unit consisting of twoelements: an inner and outer rotor.The inner rotor has one less tooth than the outer, and has its
centerline positioned at a fixed eccentricity from the centerline of theouter element.The inner element is driven by the gearbox.Vane TypeThe vane type pump consisting of a slotted inner rotor equipped withvanes operating in an eccentric housing.Operation of the Pressure Relief ValveThe oil pressure relief valve is a non adjustable, spring loaded reliefvalve.The valve will open when oil pressure reaches 345-414 kPag (50-60PSIG). The oil that is bypassed, returns to the inlet of the lubricationpump.
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DE-OILING VALVEFunction
The de-oiling valve reduces the APU starting lead during startconditions.
Location
The valve is located on the left side of the gearbox.
Main Features
- Solenoid valve operated by the ECB
- Nominal rating: 28 VDC; 1.0 amps
- Solenoid valve energized open.
Description
The de-oiling valve is a solenoid operated valve directly controlled bythe ECB.
Operation
During the APU start up the de-oiling valve is energized open by theECB. When the valve is open the lubrication pump is prevented frompumping oil into the system. This reduces the starting load of the
APU and allows faster acceleration.
When the APU accelerates to 55% speed, the ECB de-energizes thede-oiling valve and allows the lubrication pump to produce oil flow.
During shutdown, the de-oiling valve is again energized by the ECBwhen the APU de-accelerates to 90% speed. This allows the oilremaining in the system to return to the oil sump with the exceptionof one quart remaining in the oil cooler.
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OIL FILTER - OPERATION
Oil Flow
In normal operation the oil is filtered and then flows to the oil system.
Pre-blockage of the Oil Filters
Should the filter become contaminated, a difference in pressureacross the filter will occur.
Two switch indicators are mounted on the front of the gearbox neareach oil filter. The switch indicator provides a visual indication when
the oil temperature is 74°C (165°F) and the oil pressure across thefilter reaches 241 kPad (30-35 PSID). The ECB also monitors eachswitch indicator and will store the fault message.
By-pass
When the differential pressure across the filter exceeds 345 to 414kPad (50 to 60 PSID), the by-pass valve will open and allowunfiltered oil to flow into the system.
The by-pass valve is located in the gearbox and is non-adjustable.
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OIL COOLER - OPERATION
Normal Operation
The oil delivered by the lubrication pump flows through the aluminumcooling tubes that are cooled by the cooling fan air flow.
The cooled oil then flows to the various APU lubrication points.
By-pass Operation
When the pressure exceeds 207 kPad (30 PSID), the bypass valveopens.
The oil flow by-passes the cooler to the lubrication system.
Check Valve Operation
The check valve is an oil pressure operated valve.
When the pressure in the oil system is low (de-oiling during start andshutdown), the check valve closes and prevents draining of the oilcooler into the sump.
The check valve traps approximately one quart of oil in the oil cooler
when the APU is not running.
Air Flow
The oil cooler uses the airflow from the cooling fan to remove heatfrom the oil. The heated air is then discharged overboard through an
air duct located in the left APU compartment service door.
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MONITORING DEVICES - OIL TEMPERATURE SENSOR
General
Function
The Oil Temperature (HOT) sensor senses the temperature of the oilat the outlet of the oil cooler. When the oil temperature is too high,the HOT sensor initiates automatic APU shut down.
Location
The HOT sensor is installed on the lower rear face of the gearbox.
Main Features
- HOT sensor setting: 135° C (275° F)
- Sensor input signal (from ECB): 1 mA
- Sensor output signal (to ECB): variable output voltage
- 100 Ω RTD; 1 mA; 19°C to 149°C (67°F to 300°F.)
Interfaces
- The ECB
- The APU oil system.
Functional Description
The HOT sensor is a Resistive Temperature Device (RTD) suppliedwith a constant current of 1 mA (by the ECB). The resistance varieswith the oil temperature and modifies the sensor output voltage.
When the oil temperature reaches a limit value of approximately135°C (275°F), the ECB will initiate automatic APU shut down.
Note: The AC generator also has an integral oil temperaturesensor which causes the APU to shut down when anexcessive temperature is detected (180°C; 365°F). Thesensor is monitored by the ECB.
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( )Starting
When APU start is selected:
- The starter motor is energized and cranks the APU rotor assembly
- The ignition exciter operates and supplies high voltage spark to the
two igniter plugs
- The 3 way solenoid valve is energized open to provide fuel flow tothe injectors
- The servo valve is electrically operated to control the fuel flow.
Fuel from the aircraft fuel system is supplied by the low pressure andhigh pressure pumps through the servo valve and the 3 way solenoid
valve.
When the fuel pressure reaches approximately 138 kPad (20 PSID),the flow divider delivers fuel to the pilot injectors. The fuel injectedinto the combustor is ignited by the ignitor plugs.
When the fuel pressure reaches approximately 1380 kPad (200PSID), the flow divider delivers fuel to the main injectors.
During starting, the fuel flow is controlled by the servo valve usingsignals from the ECB.
At self-sustaining speed, the starter and the ignition system aredeactivated and the APU accelerates to 100% speed.
The APU is maintained at 100% speed under all load conditions bythe servo valve controlling fuel flow.
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Running Condition
- Stabilized condition
The fuel control unit provides a flow higher than APU fuel flowrequirements. The fuel is metered by the servo valve and iscontrolled by the ECB. The excess fuel is returned to the HP pump
inlet through the constant AP valve and the fuel filter.
- Transient condition
When the load applied to the power section changes, the rotationspeed changes. The ECB senses the change and implements asignal to the servo valve. The fuel flow is metered to keep the rotorspeed constant.
Shut-down
When APU shut-down is initiated (manual or automatic), the ECB de-energizes the 3 way solenoid valve. Fuel flow to the fuel injectors isshut off and bypassed back into the fuel system.
One second later the ECB de-energizes the fuel servo valve.
Any fuel remaining in the pilot manifold assembly and fuel injectors ispurged into the exhaust by combustor air pressure.
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Components of the Fuel Control Unit
- A low fuel pressure switch located at the FCU fuel inlet (notshown)
- Fuel Pumps
• A low pressure pump (centrifugal type)
• A high pressure pump (gear type) provided with apressure relief valve
- A drain line for the pump shaft seal
- A filter which includes a filter element, a by-pass valve and an
impending blockage AP indicator
- A servo valve (electrically operated valve that meters fuel flow inresponse to signals from the electronic control box)
- A constant P valve (a valve that controls the differential pressureacross the servo valve)
- A 3 way solenoid valve (valve operated by the electronic control
box to open and close fuel flow to the fuel injectors)
- A pressure regulator that provides a constant pressure to the airsystem actuators:
• A fuel outlet port (fuel supply to the actuators)
• A fuel return port (fuel return from the actuators)
- A fuel inlet union (connected to the aircraft fuel system)
- An electrical connector (current signals from the electroniccontrol box to the 3 way solenoid valve and the servo valve).
O-rings
Two O-rings are located on the fuel control. One on the fuel controlmounting flange and one on the drive shaft. Both O-rings must beproperly installed or excessive loss of oil will occur when the APU isoperating.
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Servo Valve
The servo valve meters the fuel during starting and normal operatingconditions.
The valve consists of a torque motor which operates a fuel metering
valve (clevis type).
The motor is electrically controlled by the ECB. ECB currentoperates the valve to meter fuel flow.
During starting, the servo valve meters fuel flow to accelerate the APU.
In normal operating conditions, the fuel flow is metered to maintain a
constant 100% speed.
The main features of the servo valve are:
- Type: Torque motor
- Current: 0 - 100 mA
- Metered flow: 6 - 198 kg/h (13 - 435 lbs/hr).
3 Way Soleno id Valve
The valve opens and closes the fuel supply for operation and shutdown of the APU.
The solenoid valve is energized open to supply fuel to the fuel
injectors (control from ECB).
When de-energized, a spring moves the valve to the close position.
When the valve closes, the fuel is shut off to the injectors andbypassed back into the fuel system.
During a normal or auto shutdown of the APU the ECB de-energizesthe 3 way solenoid valve, one second later the servo valve is de-
energized.
In the event the 3 way solenoid valve does not close, the APU willshut down when the servo valve is de-energized. If this conditionoccurs, the ECB will store a fault message. (APU FUEL VALVEFAILED OPEN).
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Constant P Valve
The valve maintains a constant pressure differential across the servovalve.
The valve senses upstream pressure on one side and downstream
pressure plus the force of a spring on the other side. The valveposition determines the amount of fuel to be returned to the fuelsystem.
The ΔP setting of the constant ΔP valve is of 689 kPad (100 PSID)across the servo valve. The valve is non-adjustable.
Pressure Regulator
The pressure regulator provides the fuel pressure supply to the inletguide vane actuator and the bleed control valve actuator. The valveis non adjustable.
The pressure regulator is closed from 0 to 60% APU speed. Whenthe speed is above 60%, the regulator will open and deliver 1724KPad (250 PSID) of fuel pressure to the actuators.
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Function
The flow divider distributes fuel from the fuel control unit to the pilotand main injectors. It also provides purging of the pilot injectorsduring APU shut-down.
Location
The flow divider is installed on the left side of the combustor housing.
The flow divider is located downstream of the 3 way solenoid valve.
Main Components
The flow divider consists of two valves:
- A pilot injector and purge valve set at approximately 138 kPad (20PSID) to open.
- A main injector valve set at approximately 1380 kPad (200 PSID)to open.
• A pilot injector and purge valve set at approx. 138 kPad(20 PSID)
• A main injector valve set at approx. 1380 kPad (200 PSID)
- A filter screen (located at the fuel inlet)
- Fuel inlet/outlet ports:
• Fuel inlet from the fuel control unit
• Fuel outlet to the pilot manifold
• Fuel outlet to the main manifold
• Fuel outlet to the exhaust system (purge).
- Starting
When the APU is started, the fuel pressure increases to 138 kPad(20 PSID). The pilot injector valve opens and allows fuel flow to the
pilot injectors.
When the pressure reaches 1380 kPad (200 PSID), the maininjector valve opens allowing fuel flow to the main injectors.
- Normal Running Condition
The two valves remain open to allow fuel flow to the pilot injectorsand the main injectors.
- Shut-down
As the fuel pressure decreases, the two valves close. The fuelremaining in the pilot injectors is purged into the exhaust bycombustor air pressure. At this time, a momentary puff of smokemay be viewed coming from the APU exhaust. This is a normaloccurrence.
The three pilot injectors are installed on the rear of the combustorhousing:
- One at the top (at 12 o'clock)
- Two at the bottom (one at 4 o'clock and one at 8 o'clock)
A simple jet injector comprises:
- A pilot injector body and mounting flange
- A fuel nozzle
- A heat shield
The injector fits into a heat shield that is provided with two air inletholes for cooling.
A gasket between the injector and the combustor housing.
Operation
A continuous flow of fuel is delivered to the combustor by the pilotinjectors and atomized by the fuel nozzles, the fuel is then mixedwith combustor air to maintain the combustion process.
The main manifold delivers fuel from the flow divider to the maininjectors.
Location
The main manifold is mounted around the combustor housing.
Description
The main manifold consists of flexible pipes connecting the flowdivider to the six main injectors. It is comprised of teflon tubesencased in a single layer of steel braid that is covered with a rubbersheath.
The six main injectors are located on the combustor housing.
Description
An air blast injector comprises:
- A main injector body and mounting flange
- A fuel injection tube and a shrouded air passage
- A gasket between the injector and the combustor housing.
A continuous flow of fuel is delivered to the combustor by the maininjectors. The fuel is atomized by combustor air flowing through theshrouded air passage. The fuel is then mixed with combustor air tomaintain the combustion process.
The APU is supplied with fuel normally from the aircraft left wingtank. The aircraft low pressure fuel pump provides fuel to the APUwhen the aircraft tank pumps are not operating.
The low pressure valve is controlled by the ECB and is open whenthe APU is operating. The valve is closed when the APU is shutdown normally or by the APU fire switch.
The aircraft fuel system supplies fuel to the main engines and APU.
The aircraft fuel system has three main tanks:
A low fuel pressure warning switch is located at the fuel inlet to thefuel inlet to the fuel control unit. The switch sends a signal to theECB if fuel pressure is too low.
Each tank has electric pumps to supply the engines.
A cross feed valve, located between the tanks, connects the leftand right engine supply lines. In normal operation, the cross feedvalve is closed.
The low pressure valve isolates the APU from the fuel supply.
The valve is open when the APU is running. It closes when the APUis shutdown or when the FIRE switch is activated.
The APU low pressure fuel pump is controlled by a pressure switchlocated in the fuel line to the APU. The switch senses fuel tank pumppressure. If the pressure is too low or the fuel tank pumps are turnedoff, the switch will cause the APU low pressure fuel pump to turn on.
p
The ECB will display "FUEL LO PR" message on the lower ECAMwhen the APU system page is selected. This requires the APU to beabove 7% speed and the fuel pressure below 109 KPag (15.8 PSIG).
- The inlet guide vane (IGV) system controls the load compressorairflow and prevents EGT overtemperature of the power sectionduring load compressor operation. The inlet guide vanes arecontrolled by the ECB, servo valve, and the IGV actuator.
- The air bleed system delivers airflow from the load compressor tothe aircraft pneumatic system through a bleed control valve (BCV).The valve also functions as an anti-surge valve for the load
compressor. The BCV is controlled by the ECB, servo valve, andthe BCV actuator.
upper side of the air inlet housing. The inlet guide vanes arelocated in the air inlet housing ahead of the load compressor air inlet.
The air bleed system components are located on the right lower
gsensors to control the inlet guide vanes and the bleed control valve.
Indication
The pressure is indicated on the lower ECAM APU system pagedisplay. The pressure is indicated by the load compressor dischargepressure sensor and transmitted to the indicator through the ECB,the ADIRU, the BMC computers in PSIG.
Air Sys tem Operation
The air system operation chart shows IGV and positions during
Hydraulically operated actuator using fuel supplied by the FCU, itcomprises of a servo valve and an operating piston.
Control Rod
The rod connects the actuator piston to the IGV assembly. It isconnected to the actuator piston by a quick release pin.
IGV Position Indicator
The actuator rod housing has a position indicator cast on the top and
bottom of the housing. The indicator markings range from CLOSEDto OPEN. An external metal tab is attached to the control rod andfunctions as a position indicator for the IGV’s and used to manuallymove the IGV’s when the APU is not running. The igv’s should be inthe CLOSED position before starting the APU.
The servo valve controls the position of the actuator piston by usinga spill valve that meters the potentiometric jet. The servo valve has ametered fuel pressure inlet from the actuator and a return outlet to
IGV Contro l Mechanism and Inlet Guide Vanes
The inlet guide vanes are part of the IGV assembly. A sector gear isattached to each inlet guide vane and is driven by a common ringgear
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metered fuel pressure inlet from the actuator and a return outlet tothe fuel control unit. The control current (0-100 MA) to the servovalve is provided by the ECB.
Actuator
The actuator consists of a piston that is positioned by fuel pressuremetered by the servo valve. The actuator also uses double dynamicseals for piston shaft sealing.
The position of the actuator piston is provided by a Linear VoltageDifferential Transducer (LVDT). The position signal is sent to the
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INLET GUIDE VANE SYSTEM - OPERATION
Principle of Operation
The ECB provides a control signal (0-100 MA) to the servo valve byusing the following input signals.
APU Star ting
During start, the inlet guide vanes are in the closed position toreduce the APU starting loads. The inlet guide vanes are also in theclosed position during APU shutdown.
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- APU bleed switch
- Speed (100%)
- EGT
- Air inlet pressure and temperature
- ECS mode
- MES mode.
The ECB control signal is sent to the servo valve. The servo valvemeters fuel pressure to control the actuator piston movement.
When the actuator moves, the linear voltage differential transducer(LVDT) sends the actuator position signal back to the ECB.
The actuator piston is maintained in a stabilized position by the ECBsignal (50 MA) to the servo valve.
The actuator piston positions the IGV assembly to control the airflowdelivery of the load compressor.
closed position during APU shutdown.
Operation
During load compressor operation, the position of the guide vanesare controlled by aircraft ECS computer signals sent to the ECB.
In the event APU exhaust gas temperature is too high during loadcompressor operation the ECB will signal the IGV actuator to reduceairflow delivery of the load compressor.
If inlet guide vane control is faulty, the IGV actuator will automatically
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AIR BLEED SYSTEM - GENERALFunction
The air bleed system provides air delivery to the aircraft pneumaticsystem while preventing load compressor surge.
Main Features
Component Location
- The servo-valve, the actuator and the bleed control valve form acomplete assembly located on the right lower part of the auxiliarypower unit at the scroll outlet
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AIR BLEED SYSTEM - DESCRIPTION (1)
The air bleed supply is controlled by a bleed control valve.
This valve comprises of a housing, a butterfly valve and an actuator.
APU Bleed Switch
APU Bleed Switch
When the APU master switch is selected to off during bleed airoperation, the APU will continue to run in a cool down mode for amaximum time of 2 minutes.
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When the APU master switch is selected to off during bleed air
operation, the APU will continue to run in a cool down mode for amaximum time of 2 minutes.
Housing
The housing is mounted on the load compressor scroll outlet bymeans of a v-band clamp.
Butterfly Valve
The valve is located in the BCV housing and directs air flow from theload compressor to the aircraft pneumatic systems, APU exhaust orboth.
The butterfly shaft extends through the top of the BCV housing. Theshaft has a slot machined into it that provides manual positioning ofthe valve and also serves as a valve position indicator.
The cooldown time limit can vary from 0 to 2 minutes. The time limit
depends on when the APU bleed switch is turned off prior toselecting the APU master switch to OFF.
Low B leed Air Pressure
In the event low bleed air pressure occurs, cycle the APU bleedswitch OFF and then to ON. This may restore the system to normal.
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AIR BLEED SYSTEM - DESCRIPTION (2)
Servo Valve
The servo valve controls the position of the actuator piston by usinga spill valve that meters the potentiometric jet. The servo valve has ametered fuel pressure inlet from the actuator and a return outlet tothe fuel control unit The control current (0-100 MA) to the servo
Bleed Control Valve
The bleed control valve (BCV) delivers compressed air to the aircraft,also the valve functions as an anti-surge valve for the loadcompressor.
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the fuel control unit. The control current (0-100 MA) to the servovalve is provided by the ECB.
Actuator
The actuator consists of a piston that is positioned by fuel pressuremetered by the servo valve. The actuator also uses double dynamicseals for piston shaft sealing.
The position of the actuator piston is provided by a linear voltagedifferential transducer (LVDT). The position signal is sent to the ECB
The pressure and temperature sensors are in one unit which islocated on the right rear side of the air inlet plenum.
Main Features
Pressure Sensor
- Type: variable resistor device
- Excitation voltage: + 5 and - 5 VDC
- Output signal: 0 to 50 mV
- Range: 0 to 104 kPaa (0 to 15 PSIA)
- Minimum bridge impedance: 2000Ω.
Temperature Sensor
- Type: resistance temperature device
Functional Description
- The pressure sensor is made of a bridge of 4 resistors printed ona flexible support. One of them varies if the support is deformed bythe air pressure. The whole bridge is supplied by a 5 VDC constantsource voltage coming from the ECB. The changes of the variableresistor cause the output to vary (from 0 to 50 mV).
- The temperature sensor is a resistor which is fed by a constant 1mA current supplied by the ECB. The output voltage changes from
approximately 0.8 to 1.2 VDC according to the resistance changesfrom -55 to +50°C (-67 to +122°F).
The ECB detects a sensor failure if:
- The measured ambient pressure is lower than 3.45 kPaa(0.5 PSIA) or higher than 110 kPaa (16 PSIA)
- The measured inlet temperature is lower than -62°C (-80°F) orhigher than 76°C (170°F)
Normal BCV control will be maintained if either air inlet pressure ortemperature sensor is failed.
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Use or disclosure of this data is subject to therestriction on the title page of this document.
ACCESSORY COOLING - GENERAL
Function
The accessory cooling system supplies air for the oil cooler and forthe APU compartment ventilation.
Location
Cooling Fan
The fan provides cooling air to the oil cooler and to the compartmentcooling duct. The fan assembly incorporates a permanent magnetgenerator that is used for APU backup overspeed and to preventmomentary power interruption of the ECB.
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The system components are located on the APU.
Main Features
Cooling by circulation of air taken from the air inlet plenum andaccelerated by the cooling fan.
Main Components
The main components of the system are the fan inlet duct assembly,the cooling fan, the fan outlet duct assembly, the oil cooler and theoil cooler exhaust duct.
Fan Inlet Duct
This duct connects the engine air inlet plenum to the inlet of thecooling fan.
Fan Outlet Duct
This duct connects the outlet of the cooling fan to the inlet of the oilcooler.
Oil Cooler Exhaust Duct
This duct connects the oil cooler outlet to the APU compartment doorvent.
Compartment Cooling
The APU compartment is ventilated by air ducted from the coolingfan outlet duct. The air is discharged into the compartment throughthe compartment cooling duct.
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The cooling fan incorporates a permanent magnet generator thatprovides momentary direct current power, and a backup overspeedsignal to the electronic control box.
Location
The cooling fan is located at the top of the gearbox front face and issecured by a V-band clamp.
Main Features
- Cooling fan rotation speed: 51965 RPM
- Permanent Magnet Generator output: 40 VDC (100% of N)
- Speed signal for back-up of the overspeed protection system:107%.
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bearings, the bearings are lubricated by the APU oil system. Theshaft assembly uses a carbon seal and two labyrinth sealspressurized by the power section impeller air. The oil used forlubrication of the cooling fan is returned to the oil sump by gravity.
A permanent magnet generator (PMG) and a printed circuit boardare located in the fan housing. The printed circuit board contains therectifier components for the PMG electrical power output to the ECB.
The cooling fan can be used to turn the APU rotor assembly duringborescoping. This is accomplished by removing the fan inlet duct andmanually rotate the fan impeller.
PMG
The permanent magnet generator (PMG) is driven by the cooling fanshaft. The PMG provides momentary (240 msec) of rectifiedelectrical power to the ECB when the aircraft electrical power isinterrupted during power transfer.
One unrectified PMG output provides a frequency signal to the ECBthat is used for the back up overspeed signal.
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Full Authority Digital Electronic Controller (FADEC)- On Board Replaceable Memory Module (OBRM) for design
flexibility and reduced component count- Modular design for reliability, maintainability and testability- No calibration required- Digital communication links (ARINC 429 and RS 232-C)
The main components are:- The ECB enclosure which houses Printed Wiring Assemblies
(PWA)- The ECB front face which includes:
• A RS 232-C connector• A front cover door housing the On Board Replaceable
Memory Module (OBRM)
• A handle- The ECB rear face which includes an ARINC 600 connector.
Identification
The electronic control box has an identification plate and amodification plate, both located on the front face of the ECB.
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ELECTRONIC CONTROL BOX - GENERAL
ELECTRONIC CONTROL BOX - DESCRIPTION (1)
ECB Inputs
General
This chapter considers the discrete and analog input signals to theECB.
The bleed control valve (BCV) command is transmitted to theECB by means of an aircraft discrete signal. Upon receipt of thiscommand, the ECB contro ls the opening o f the BCV to supplythe aircraft pneumatic sys tem.
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Sensors and Discrete Inputs from Ai rcraft to ECB
The corresponding signals form part of the ECB Inputs-Outputsdefinitions and PIN assignments.
APU Stop (ground)
The stop signal is transmitted to the ECB by the APU master switchin the flight deck. Actuating the switch causes a contact closure toground.
Bleed Control Valve Activation (ground)
Emergency Stop (ground for approx. 150 ms)
The emergency stop signal is transmitted to the ECB by means of a
discrete signal created by a contact closure to ground.
This signal to the ECB is to indicate whether or not the aircraft is in-flight operation. Special considerations (i.e. safety systems) apply forin-flight operation.
MES Mode (28 V)
This signal indicates to the ECB whether or not the aircraft is in MainEngine Start mode (MES) of operation. The circuit is normally open.In the MES mode, the aircraft causes the circuit to close and tosupply a 28 V signal to the ECB.
Start Contactor Monitor (28 VDC/open/ground)
This discrete 28 VDC signal tells the ECB whether or not the back-upstart contactor is closed or whether or not it is open.
The start contactor monitor is used exclusively for fault isolationpurposes.
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ELECTRONIC CONTROL BOX - DESCRIPTION (2)
Sensors and Discrete Inputs from Aircraft to ECB (continued)
Air Intake Flap Open Posi tion (28 VDC)
When the air intake flap is in the fully open position, a switch isactivated to supply a 28 VDC signal to the ECB.
This signal is used to initiate the start sequence.
JAR Configuration
Low Fuel Pressure Switch (open/ground)
The switch closes to ground when the fuel pressure falls below agiven pressure.
Air Intake Flap Closed Posit ion (ground)
When the air intake flap is in the fully closed position, a switch is
activated to the closed position and provides a ground signal to theECB. The aircraft relay operation is maintained until the flap closedsignal is received
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The ECB is programmed in the JAR mode. This means that allshutdown faults sensed by the ECB will cause the APU to shutdownon the ground or in flight.
Start Command (28 VDC for approx. 150 ms)
This command is activated by momentarily placing the start button inthe flight deck to "on". This action provides a 28 V signal to the ECB.
signal is received.
Air Intake Flap Movement (28 VDC)
During normal APU operation, a 28 VDC signal is transmitted to theECB when voltage is being applied to open or close the air intakeflap.
Generator Oil Temperature Sensor (100 )
This sensor is mounted in the AC generator. The wiring uses thegenerator connector, P4. The sensor is a resistance temperaturedevice (RTD). It's variable resistance is a function of temperatureand is supplied with a constant current of 1 mA.
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ELECTRONIC CONTROL BOX - DESCRIPTION (3)
Sensors and Discrete Inputs from APU to ECB
Low Oil Pressure Switch (ground)
The low oil pressure switch is a normally closed contact. The switchopens and remains open when oil pressure is present.
Oil Filter Switch Indicators
This is a differential pressure switch that is normally open. Thecontact closes and provides a ground signal in case of filter
This sensor is a variable resistance device supplied by a constantsource voltage of 5 VDC.
The output ranges from 0 to 50 mV for a 0 to 15 PSIA range of airpressure.
Load Compressor Discharge Air Pressure Sensors (P) and (
P)
There are two sensors: one to measure the pressure at the loadcompressor scroll (P), the other one to measure the differential airpressure between the diffuser and the scroll (AP). The ratio signal
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p g grestriction.
EGT Sensors
The EGT is measured by two independent thermocouples. They areK type (Chromel-Alumel).
The output is of approx. 1 mV per 24°C (43°F).
High Oil Temperature Sensor (100 )
The sensor is a Resistance Temperature Device (RTD). Theresistance varies according to the oil temperature and is suppliedwith a constant current of 1 mA.
Inlet Air Pressure Sensor
p ( ) g AP/P is used to prevent load compressor surge.
The two sensors are of variable resistance type supplied by aconstant voltage of 5 VDC.
The outputs range from 0 to 50 mV for a 0 to 100 PSIA (absolute) or
0 to 25 PSID (differential) ranges of air pressure.
Rotation Speed Sensors
There are two independent speed sensors mounted in the gearbox.
They provide a wave signal as a function of the teeth on the phoneticwheel (24) and the rotation speed (i.e. 19720 Hz at 100% speed).
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ECB with 3 voltage lines V 1, V2, V3 matched to the engine IDnumber. The engine serial number is the sum of the ID number andthe number 1000.
The engine ID number is stored in the ECB NOVRAM memory aspart of the power up initialization. The ID module is considered failed
when all inputs are shorted, one or all inputs are open, a numbergreater than 2048 is used, or 3 consecutive readings at power upinitialization are not identical.
discharge.
Oil Level Sensor (100 A)
The gearbox mounted oil level sensor is a Resistance TemperatureDevice (RTD) type. The variable resistance value is provided with a
constant current of 75 mA. The oil level is checked at power up overa period of 8 seconds and is determined OK or LOW.
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ELECTRONIC CONTROL BOX - DESCRIPTION (5)
Sensors and Discrete Inputs from APU to ECB (continued)
Permanent Magnet Generator (PMG)
A Permanent Magnet Generator (PMG) is installed in the cooling fan.The assembly consists of the PMG rectifier circuit and a DC fusiblelink.
The PMG provides the ECB with rectified power and one unrectifiedsignal from one of the three phases (backup overspeed protection at107%).
Starter Motor Voltage
The starter motor is monitored by the ECB for low voltage during APU start. The low voltage sensing connector is located on the frontface of the starter motor housing.
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ELECTRONIC CONTROL BOX - DESCRIPTION (6)
ECB Outputs
General
This chapter considers the discrete and digital outputs of the ECB.
Discrete and Digital Outputs (to the aircraft)
Backup Start Contactor (28 VDC, 1 A nominal)
This contactor is energized by means of a discrete signal. The signalis supplied through a Field Effect Transistor (FET) in the ECB
Bleed Control Valve Open (28 VDC, 0.1 A)
The ECB transmits a discrete signal to the aircraft indicating systemwhen the bleed control valve is in the position that allows maximumflow to the aircraft pneumatic system.
APU Available (28 VDC, 0.4 A)
The ECB provides a discrete signal to the AVAIL light in the startswitch when the APU has completed the start sequence and is readyto load.
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is supplied through a Field Effect Transistor (FET) in the ECB.
Main Start Contactor (28 VDC, 1 A nominal)
This contactor is energized by means of a discrete signal. The signalis supplied through a FET device in the ECB.
Aircraf t Relay (ground, 0.4 A)
The aircraft relay is activated by a closed contact to ground throughthe ECB. The aircraft relay is activated when the ECB is energizedand no stop command is present.
Start in Progress (28 VDC, 0.1 A)
The ECB transmits a discrete signal to the ON light in the start switchto indicate a start is in progress.
The light is "ON" from the beginning of the start until the "APUavailable" light turns on.
Fault (28 VDC, 0.2 A)
The ECB transmits a fault discrete signal to the aircraft for allshutdowns.
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ELECTRONIC CONTROL BOX - DESCRIPTION (7)
Discrete and Digital Outputs (to the aircraft) (continued)
Flap Open Command (28 VDC, 3.5 A)
The ECB provides a power output for opening the air intake flap. Theflap open command is emitted through a FET device in the ECB.
This output is protected against overload and short circuits.
Flap Closed Command (28 VDC, 3.5 A)
The ECB provides a power output for closing the air intake flap. The
• ARINC 429 input from ECS: It is used by the ECB toreceive specific data from the Environmental ControlSystem (i.e. ECS demand signal, ECS valve status word,etc...)The ECS demand signal is used in the control of the IGV's.The ECS valve status word informs the ECB of the numberof air conditioning packs currently supplying air
• ARINC 429 CFDS output: The ARINC 429 outputtransmits data to the CFDS, ECAM (Electronic Centralized
Aircraft Monitoring) and ACMS (Aircraft ConditionMonitoring System)
HSPS CT/NOV.. 2006 Page 6.36HAMILTON STANDARD PROPRIETARY
HARDWARE DESCRIPTION
ELECTRONIC CONTROL BOX - DESCRIPTION (9)
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ELECTRONIC CONTROL BOX - OPERATION (1)
General
The operating phases are:
- Power up
- Watch state
- Start preparation state
- Starting state
- Run state
Power Up State
GeneralWhen the APU master switch is selected to ON, the ECB enters thePOWER UP state.The POWER UP state lasts approximately 3 sec.OperationThe ECB checks that outputs are not energized except those that
are required.The ECB enters self test.The ECB is able to recognize and record the occurrence of start oremergency stop signals.Upon receipt and validation of the start signal, the "start in progress"
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Run state
- Cool down state
- Shutdown state
p p g , p goutput is energized.The requirement to activate the "start in progress" output alsoapplies to the WATCH state.In case of an emergency stop signal being received, the ECB closesthe air intake and deactivates the aircraft relay output once the air
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ELECTRONIC CONTROL BOX - OPERATION (2)
Watch State
General
After completion of the POWER UP state the ECB automaticallyenters the WATCH state.
Operation
The ECB is able to recognize and record the occurrence of start oremergency signals.
Upon receipt of an emergency stop signal the ECB closes the air
Start Preparation State
General
Upon receipt of the start command, the ECB enters the STARTPREPARATION state.
Operation
During this state the flap actuator position, the oil level and therotation speed is checked. If the speed is greater than 7%, the startcommand will be inhibited until the speed is less than or equal to 7%.
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The purpose of speed control is to maintain the APU at 100% speedunder all load conditions. This is accomplished by the fuel controlunit increasing or decreasing fuel flow automatically when APU loadchanges occur.
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ELECTRONIC CONTROL BOX - OPERATION (7)
Shutdown State
General
The APU enters the shutdown state after a normal shutdown or afault shutdown occurs.
Note: The APU can be re-started during the shutdown state. Thisis accomplished by cycling the master switch OFF to ON andthen selecting the APU start switch to ON.
The ECB does not close the flap and the APU automaticallyre-starts when 7% speed is reached.
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ELECTRONIC CONTROL BOX - OPERATION (8)
Condition Monitor ing Data
General
For long term trend monitoring, the APU control system records theengine operating parameters.
Operation
APU conditioning monitoring parameters are taken during operationof the APU. The ECU does not store this information but it may beretrieved from the Aircraft Integrated Data System (AIDS) if thissystem is installed.
The following parameters are:
In addition, the ECB records:
- APU operating hours (in one minute increments from speed > 55%until the 3-way solenoid valve is de-energized.
- Number of starts (1 start = EGT rise detected + speed > 30%)
- ECB operating hours (in one minute increments, from ECB powerON to ECB power OFF).
The condition monitoring data is associated with the engine
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g p
- Exhaust Gas Temperature °C
- Engine speed %
- Engine inlet pressure PSIA
- Engine inlet temperature °C
- Fuel flow LB/HR
g gidentification (ID) number, ECB serial number.
Note 1: The condition monitoring parameters are not taken when
either the inlet pressure or temperature sensors are faulty.
Note 2: If the engine ID module has been determined failed, the APU system operating history data will be associated withthe last valid engine I D number.When a new engine ID number occurs, it is used withouterasing the previously recorded historical data.The oldest data is overwritten by the new data as it isrecorded.
The ECB records the condition monitoring data associatedwith the last APU cycle and the data is available via the ARINC 429 link.
• Frequency signal range: 0 to 24 KHz; 0 to 50 volts.
Operation
The phonic wheel rotates with the rotor assembly, as the teeth passby each speed sensor they generate a voltage. The voltage isproportional to the speed of the phonic wheel. The signal is sent tothe ECB for speed indication and system control.
The ECB will calculate the average signal of the two speed sensors.In the event a signal difference of 5% or more occurs, the ECB willselect the sensor indicating the highest value.
APU speed indication is displayed on the lower ECAM when the APU system page is selected.
Use or disclosure of this data is subject to therestriction on the title page of this document.
g
An EGT system failure is declared if:
- EGT is lower than 120°C (250°F)
- EGT is higher than 1200°C (2200°F).
The ECU will calculate the average signal of the two thermocouples.In the event a signal difference of 121°C (250°F) or more occurs, theECB will select the thermocouple indicating the highest value.
APU exhaust gas temperature indication is displayed on the lowerECAM when the APU system page is selected.
Use or disclosure of this data is subject to therestriction on the title page of this document.
Starter low voltage is sensed by the ECB through the low voltagesensing connector.
Ignition Exciter
The ignition exciter is located on the left side of the APU. The exciteris a capacitor-discharge unit that uses 28V DC to provide anintermittent high voltage output to the two ignitor plugs.
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Fuel servo valve and 3 way solenoid valve energized open.
- Ignition
Ignition exciter energized to provide ignition to the two ignitorplugs.
Starting Cycle
- Automatically by the ECB fault shut-down system.
The ECB controls the fuel control unit 3 way solenoid valve. Whenthe APU is shut down manually or automatically the 3 way solenoidvalve is de-energized closed. The closed valve shuts off the fuel tothe fuel injectors.
Use or disclosure of this data is subject to therestriction on the title page of this document.
IGNITORS AND IGNITOR CABLES
Function
There are two ignitor plugs used to ignite the fuel in the combustorchamber during start up of the APU. They are connected to theignition exciter by two shielded ignitor cables.
Location
The two ignitor plugs are located on the combustor housing:
- One at 5 'o'clock
- One at 9 'o'clock.
Note: Location is looking at the combustor housing rear view.
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AIRCRAFT/APU HARNESS (2)
Description (continued)
APU eng ine harnessThe engine harness is connected to three firewall connectors, theyare identified as (P-1, P-2 and P-3).P1 connector:- PMG- 3 way solenoid valve- Ignition exciter- Starter Motor (low voltage sense signal)- Bleed Control Valve LVDT- Gearbox de-oiling valve- Oil filter switch indicators- Low oil pressure switch- Oil level sensor- Low fuel pressure switch- Generator high oil temperature sensor- AC generator current transformers.
P2 connector:- Load compressor discharge pressure sensors- IGV actuator (servo valve and LVDT)- BCV actuator (servo valve)- Fuel servo valve- Speeds sensor 1 and 2- Oil temperature sensor- EGT sensor 1 and 2- Engine ID module- Air inlet pressure and temperature sensor.P3 connector:- AC generator PMG- AC generator excitation control.
Use or disclosure of this data is subject to therestriction on the title page of this document.
AIRCRAFT/APU HARNESS (3)
Description (continued)
Starter motor electrical power supply cables
The starter motor DC power supply is provided by the aircraftbatteries or the Transformer Rectifier Unit (TRU).
The supply is controlled by two contactors in series (backup andmain start contactors). The power cables link the start contactorsdirectly to the starter motor (+ and -cables).
AC generator harness
The AC generator connector P-4 is part of the engine harness. Theconnector provides the following signals:
- AC generator oil temperature and control signals through the P-1engine harness connector
- AC generator PMG signal and exciter field control through the P-3engine harness connector.
The four AC generator cables are connected to the aircraft electricalbuss system. Three of the cables provide AC power and the fourthcable is a neutral.
Use or disclosure of this data is subject to therestriction on the title page of this document.
AC GENERATOR - GENERAL
FunctionThe AC generator (Alternating Current Generator) provides electricalpower to the aircraft systems.LocationThe AC generator is mounted on the front face of the gearbox.Type- Brushless- 3 phases- Oil cooled.Main Features
- Nominal power: 90 kVA- Output: 115 V, 400 Hz- Rotation speed: 24 034 RPM at 100 % APU speed- Direction of rotation: Clockwise viewing the pad- Weight: approx. 22.7 kg (50 lbs).
Interfaces- Oil system (lubrication, cooling)- Generator Control Unit (GCU)- Electronic Control Box (ECB).Main Components- Permanent Magnet Generator- Current transformers- High oil temperature sensor (HOT).
Use or disclosure of this data is subject to therestriction on the title page of this document.
This allows the exhaust pipe to be disconnected from the APU andmoved rearward to provide additional clearance during removal andinstallation of the APU.
Use or disclosure of this data is subject to therestriction on the title page of this document.
EXHAUST SYSTEM
EXHAUST GAS
DRAIN SYSTEM (1)
Function
The APU drain system provides drains from various components.The fluids are collected and drained overboard through the drainmast.
The fuel control unit, BCV actuator and IGV actuator use a commondrain to the aircraft drain tank. Fluids are siphoned from the draintank, into the drain mast and then discharged overboard when theaircraft is in flight.
The other common and single drains flow directly into the drain mastand then discharge overboard.
Use or disclosure of this data is subject to therestriction on the title page of this document.
INSPECTION AND CHECKS
Visual Inspections
Opening the APU compartment for corrective maintenance orservicing provides the opportunity to visually inspect the APU forsecurity, leaks, and warning indicators. The following arerecommended inspection items:
- Engine mounts
- Engine Components and Fluid lines
- Oil Quantity and Magnetic Drain plug
- Oil and Fuel Filter impending blockage Indicators
- Electrical harness and Connectors
- Engine Air Inlet Plenum
- Engine Combustor Housing and Exhaust System.
Borescope Inspection
The APU internal components may be inspected by using a flexibleborescope. To rotate the APU internal components, the cooling faninlet duct may be removed to allow manual rotation of the fanimpeller.
The following components can be inspected with the APU installed inthe aircraft.
- Load compressor impeller and guide vanes
- Power section impeller
- Combustor, viewed through the ignitor and fuel injector bosses
- First stage turbine wheel
- Second stage turbine wheel.
Refer to the Aircraft Maintenance Manual for borescopeprocedures.
Use or disclosure of this data is subject to therestriction on the title page of this document.
GENERAL DESCRIPTION
The centralized fault display system (CFDS) provides electronicsystem fault detection, fault storage, fault displays, operationaltesting and troubleshooting from the flight deck multi-purpose controland display unit (MCDU).
CENTRALIZED FAULT DISPLAY AND INTERFACE UNIT
The CFDIU provides the interface between the APU electronic
control box (ECB) and the MCDU for screen display of APU faultinformation.
MULTIPURPOSE CONTROL AND DISPLAY UNITS
The Multipurpose Control and Display Unit (MCDU) is a display unitand a keyboard used by the CFDS to display and interrogate faultsand to initiate system tests. Both MCDU's (Multipurpose Control andDisplay Unit) are connected to the CFDS.
Only one MCDU can be used when interrogating the CFDS.
CFDIU/PRINTER INTERFACE
The CFDIU sends MCDU screen information and print commands tothe optional printer automatically or on request.
CFDIU/ACARS INTERFACE
The CFDIU sends fault information to the optional ACARS for down-linking when selected manually by the MCDU operator or when anuplink request is received from a ground station via the ACARS
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APU FAULT WARNINGS
Flight Deck Fault Warnings are identified as Class 1, 2 and 3.
Class 1 faults are further identified as Level 3, 2 and 1.
CLASS 1
- Level 3- This level corresponds to warnings needing immediate
action.- Level 3 warnings are associated with:
- Repetitive chime- Warning message on upper ECAM display- Master Warning Light flashing Red - APU systems page on lower ECAM display
- Level 2- This level corresponds to abnormal situations needing
immediate awareness but not immediate action.- Level 2 warnings are associated with:
- Single chime- Master caution steady Amber light- Warning messages on upper ECAM display
- APU system page on lower ECAM displayLevel 1
- This level corresponds to reduced bleed air performance- It is associated with low or zero duct pressure- Low or zero duct pressure is visible (lower ECAM display) on
CLASS 2
- These failures are indicated on the STATUS page, under the titleof MAINTENANCE.
- They are also accessible through the CFDS.
indicates that the STATUS page is not empty andflashes in flight phase 10 on the upper ECAM display.STS
CLASS 3
- These failures are only accessible through the CFDS. No APUfault warnings are displayed.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT WARNINGS
STATUS
STATUS (STS) indication is an "attention getter" on the upper ECAMdisplay.
STATUS (STS) indicates that a status message (class 1 or class 2fault) is present and further maintenance action may be required. Aflashing STS indication occurs after the second engine shutdown inFlight Phase 10. It is necessary to press the STS key on the ECAMcontrol panel for the STATUS page to appear on the lower ECAMdisplay.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT WARNINGS
ECAM CONTROL PANEL
The control panel allows selection of the aircraft system pageincluding APU. Pressing the Status (STS) key presents the STATUSpage on the lower ECAM display. The STATUS page will indicate thefaulty aircraft systems under the INOP SYS (Class 1 Fault) andMAINTENANCE (Class 2 Fault) titles.
Use or disclosure of this data is subject to therestriction on the title page of this document.
MULTIPURPOSE CONTROL AND DISPLAY UNITS
The Multipurpose Control and Display Unit (MCDU) is a display unit
and a keyboard used by the CFDS to display and interrogate faultsand to initiate system tests. Both MCDU's (Multipurpose Control andDisplay Unit) are connected to the CFDS.
Only one MCDU can be used when interrogating the CFDS.
Pressing the MCDU MENU key, the MCDU menu page is displayed,and any one of the systems connected to the MCDU can beselected.
A multiple page display is indicated by an arrow (∇) in the right uppercorner of the screen. In this case the NEXT PAGE key must be usedto provide access to the various pages of the display. The NEXTPAGE key can be used as long as the arrow is displayed.
Twelve line select keys, six on the left and six on the right, provideaccess to a page or a function. The line select keys permit access toa page or a function when these prompt symbols appear (>, <). Theyare identified as 1L to 6L on the left, and 1R to 6R on the right.
If a flight deck printer is installed and operational, the current MCDUdisplay screen may be printed by pushing the PRINT line select key.
APU FAULT OPERATION
SYSTEM SELECTION
The MCDU MENU page is displayed when the MCDU MENU key ispushed.
Selecting the CFDS line select key will then display CFDS menu.
Pressing the SYSTEM REPORT/TEST line select key displays theSYSTEM REPORT TEST menu.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
SYSTEM REPORT/TEST
When SYSTEM REPORT/TEST is selected while on the ground, asystems menu is displayed. The APU selection is located on thesecond page of the menu. Pushing the NEXT PAGE key will display
APU.
Selection of the RETURN line select key on the first page will displayMCDU MENU.
Selection of the RETURN line select key on the second page willdisplay the first page of SYSTEM REPORT/ TEST.
APU
There are two APU menu pages available. The first page displaysthe following information:
LASTLEGREPORT
PREVIOUSLEGREPORT
LRUIDENTIFICATION
SYSTEMSELF-TEST
SHUTDOWNS
The second page of the APU menu when selected by theNEXTPAGE key, displays the following information:
APUDATA/OIL
CLASS3FAULTS
Selection of the RETURN line select key on the First Page willdisplay the Second Page of SYSTEM REPORT/TEST.Selection of the RETURN line select key on the (Second Page) willdisplay the (First Page) of APU menu.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
APU LAST LEG REPORT
The Last Leg Report displays fault information delivered by theCFDS system. It can store up to 40 failures during the Last Leg. TheLast LEG Report displays only class 1 and 2 faults and contains theidentity of each LRU, its corresponding Date, GMT, ATA chapter andFault Code Number (FCN) for each fault occurrence. The FunctionalIdentification Number (FIN) appears after each LRU. In the case ofmultiple failures, the failures will be displayed in chronological orderwith two failures per page. A maximum count of four intermittentfaults will only be displayed in the same flight leg. Prompts (>) at the
end of each LRU message indicate the line select key to display the APU FAULT CONDITIONS screen. All of the Last Leg Report isprinted when the PRINT line select key is pushed, even if it containsseveral pages.
Selection of the RETURN line select key will display APU menu,(First Page).
APU PREVIOUS LEGS REPORT
The Last Leg Report contents are transferred into the Previous LegReport with each new flight leg. The report can store up to 200failures over the last 63 flight legs. Each LRU is identified along withthe Aircraft identification, Leg number, Date, GMT, ATA chapter andFault Code Number (FCN) for each fault occurrence. The FunctionalIdentification Number (FIN) appears after each LRU. In the case ofmultiple failures, the failures will be displayed in reversechronological order with two failures per page. Prompts (>) at theend of each LRU message indicate the line select key to display the
APU FAULT CONDITIONS screen. Only the PREVIOUS LEGSREPORT displayed page will be printed when the PRINT line selectkey is pushed.
Selection of the RETURN line select key will display APU menu,(First Page).
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
APU LRU IDENTIFICATION
The LRU Identification page displays the ECB Part Number, ECBSerial Number and the ECB Software Version.
The ECB part number is adjustable and is stored in the NVM. Thebuilt letter (H) following the part number is adjustable from A to Z.
Selection of the RETURN line select key will display APU menu,(First Page).
APU SYSTEM SELF TEST
A self test of LRU's may be initiated through the CFDS. The test canonly be accomplished when the APU is not running and the MasterSwitch is ON. In case of no failures or when the test is in progress, orlack of availability of the test function, the message of TEST OK, INPROGRESS and NOT AVAILABLE will be displayed respectively.Detected failures will be displayed with their ATA Chapter and FaultCode Number (FCN). The Functional Identification Number (FIN)appears after each LRU. In the case of multiple failures, the failureswill be displayed in chronological order with two failures per page.
Only the SYSTEM SELF TEST displayed page will be printed whenthe PRINT line select key is pushed.
Selection of the RETURN line select key will display APU menu,(First Page).
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
APU SHUTDOWNS
The Shutdowns page contains its corresponding Date, GMT, FaultCode Number (FCN), shutdown message and the identity of theLRU. The Shutdowns will be displayed in reverse chronological orderwith only one shutdown per page. Prompts (>) at the end of eachLRU message indicate the line select key to display the APU FAULTCONDITIONS screen.
In case there are no shutdowns, the message of NO SHUTDOWNSwill be displayed. Only the SHUTDOWNS displayed page will be
printed when the PRINT line select key is pushed.
Selection of the RETURN line select key will display APU menu,(First Page).
APU DATA/OIL
APU Data/Oil page contains the Date, APU Serial Number (S/N),Hours, Start Attempts, Start Cycles and Oil level status. Prompts (>)at the end of the message indicate the line select key to display the"Update APU Data" screen.
Selection of the RETURN line select key will display APU menu,(Second Page).
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
APU CLASS 3 FAULTS
Class 3 Faults can be stored up to 200 failures over the last 63 flightlegs. Each LRU is identified along with the Aircraft identification, Legnumber, GMT, ATA chapter and Fault Code Number (FCN) for eachfault occurrence. The Functional Identification Number (FIN) appearsafter each LRU. In the case of multiple failures, the failures will bedisplayed in reverse chronological order with two failures per page.Prompts (>) at the end of each LRU message indicate the line selectkey to display the APU FAULT CONDITIONS screen.
In case there are NO CLASS 3 FAULTS detected, the message NOFAULTS will be displayed. Only the CLASS 3 FAULTS displayedpage will be printed when the PRINT line select key is pushed.
Selection of the RETURN line select key will display APU menu,(Second Page).
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
UPDATE APU DATA
Selection of this screen allows the operator to update the APU hoursand cycles when the ECB or the APU is changed.The Update APU Data screen is only accessible by prompts (>) fromthe APU Data/Oil Screen. The Update APU Data screen displays the
APU Serial Number (S/N), and current values of Hours and Cycles.The new values of hours and cycles can be entered by use of MCDUkeyboard. After line key 3L is pressed (Prompt <) the screen willdisplay the new values for APU hours and cycles when the ECB or
APU is changed.
The HOURS and CYCLES will be printed when the PRINT line selectkey is pushed.
Selection of the RETURN line select key will display the APUDATA/OIL screen.
Use or disclosure of this data is subject to therestriction on the title page of this document.
APU FAULT OPERATION
FAULT CONDITIONS
The Fault Conditions screens are only available by the line selectkeys indicated by prompt (>) on the Last Leg Report, Previous LegsReport, Shutdown and Class 3 fault screens. Selection will displaythe Fault Conditions screen-1 or screen-2. Each screen will displaythe APU S/N, Date, GMT and the identity of the LRU. The FunctionalIdentification Number (FIN) appears after the LRU.Engine data from the fault data stored in the Electronic Control Boxnon-volatile memory will also appear on each screen. (See Screen-1and Screen-2 Parameters on page 12-24).
One screen at a time is displayed. To select screen-2 when screen-1is displayed or select screen-1 when screen-2 is displayed it isnecessary to press the NEXT PAGE key on the Multipurpose Controland Display Unit (MCDU).
Only the screen that is displayed (Screen-1 or Screen-2) will beprinted when the PRINT line select key is pushed.
Selection of the RETURN line select key will display the screen thatwas shown preceding selection of the Fault Selection Screens.
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FAULT CHARTS
The following Fault Charts provide the information that will be sent tothe CFDS by the ECB in the event of a fault.
The information appears in the Fault Chart columns located underthe following headings:
Version 5.0
MCDU LRU MessageMCDU Shutdown MessageFault CodeFault Class
LRU ID ATA ChapterSystem Severity level
SYSTEM SEVERITY LEVEL
System Severity Levels are not sent to the CFDS. It is presentedhere only as information.
Once a fault has been identified with a switch or a sensor thatcomponent will no longer be used for further fault detection, isolationor control until the fault is no longer present. Detected faults can becleared and a restart may be possible once the master switch iscycled.
Use or disclosure of this data is subject to therestriction on the title page of this document.
TROUBLESHOOTING
GENERAL
The troubleshooting system is designed to provide additionalinformation to aid in the maintenance and repair of the AuxiliaryPower Unit (APU) by downloading the Electronic Control Box (ECB)located in the aircraft aft cargo compartment.Maintenance information is stored in the nonvolatile memory of theECB and can be retrieved and analyzed by downloading into alaptop computer. The computer displays information andrecommended actions from the following stored data:
CONDITIONING MONITORING DATA
This data consists of engine parameters taken at each engine startand shutdown. Data is provided for the last twelve engine run cycles.
FAULT DATA
The data consists of maintenance and fault messages for class 1,class 2 faults and class 3 faults.
REQUIRED HARDWARE
Downloading of the ECB requires the following equipment:
Laptop computer or Personal Computer (PC) with at least3MB of free hard disc space, a modem and a Windows 95 orlater operating system.
A special interface cable is required to connect theComputer to the ECB. The interface cable (P/N AGE 70021)is available by contacting Hamilton Sundstrand.
Use or disclosure of this data is subject to therestriction on the title page of this document.
TROUBLESHOOTING
ECB TROUBLESHOOTING AID
To download and diagnose fault data, refer to APIC SIL APS32-0049-47 for in-depth instructions.
Basic Steps:• Connect the interface cable from the computer to the ECB.• Power-up computer.• Select Diagnose on the tool bar.• Enter operators name on the Setup screen.• APU master switch ON (APU not running.)
Use or disclosure of this data is subject to therestriction on the title page of this document.
TROUBLESHOOTING
ECB TROUBLESHOOTING AID
ECB TROUBLESHOOTING AID (Fault Information)
The computer screen displays Class 1, Class 2 faults and Class 3faults. The screen will download and provide a file automatically forreview. (See example on page 13.6.)
Select the Most Recent scroll bar on the screen to scroll through thevarious faults.Each fault or fault combination is provided with a fault description
Use or disclosure of this data is subject to therestriction on the title page of this document.
TROUBLESHOOTING
ECB TROUBLESHOOTING AID
REAL-TIME DATA MONITORING
With the Real-Time Data monitoring screen displayed, select AnalogI/O, Speed/Temp, or Discreet Inputs. Each selection displays ascreen that provides real time data. The data is viewed at the bottomof the screen when a data box is selected.
Note: The more data boxes selected the longer it takes for theinformation to appear. Select data that is related to the
specific fault for a faster response time.
BASIC STEPS:• Connect the interface cable from the computer to the ECB.• Power-up computer.• Start and run APU.• Select data box.• Select Start Monitoring.• Select Stop Monitoring after data has been taken.
Selecting Save Data at the bottom of the screen and selecting a filename allows the data to be saved. (See page 13.9 and example onpage 13.10.)