Level III - Ata 49 Apu

A380 TECHNICAL TRAINING MANUAL MANUAL MAINTENANCE COURSE - T1 & T2 (RR / Metric) LEVEL III - AT ATA 49 APU

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A380 TECHNICAL TRAINING MANUAL

LEVEL III - ATA 49 APU Theory System APU Assembly Description (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 APU Oil System Descrip tion (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 APU Fuel System Des cription (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 APU Air System Descrip tion (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 APU Interfaces Description (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 APU Ignition & Starting Description (3) . . . . . . . . . . . . . . . . . . . . . . 42 APU System Maintenance (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Component Location (3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

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MAINTENANCE COURSE - T1 & T2 (RR / Metric) LEVEL III - ATA 49 APU

TABLE OF CONTENTS

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APU ASSEMBLY DESCRIPTION (3) General The APU is installed at a 15 angle in a fireproof compartment of the aircraft tailcone. Two maintenance doors at the bottom of the tailcone structure give access to the APU. The APU air inlet opening is on the upper right hand side of the aircraft fuselage. The air inlet duct supports the air in take flap, which is operated by a door actuator (electric motor). A rain gutter is installed forward the air intake, to protect the air intake against the precipitation or against ingestion of fluids generated on the fuselage. Openings for the cooling air compartment (cooling duct) and the APU air pressure relief door (LH maintenance door) are on the left hand side of the APU compartment. The exhaust muffler is the APU exhaust silencer, it has to release combustion gases into the atmosphere and suppress APU generated exhaust noise. The Aft part of the muffler is inside the rear fairing. °

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APU ASSEMBLY DESCRIPTION (3)

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APU ASSEMBLY DESCRIPTION (3) APU Mounts The APU is attached to the APU compartment structure by a suspension system via three airframe mounts. The APU attachment points comprise two forward mounts on the top of the load gearbox and two rear mounts on the gas generator case, aft of the fuel manifolds. The rear mounts are attached by links to a common single point. The three attachment points include shock mounts to prevent transmission of noise and vibration to the airframe, and to get normal airframe movement that occurs in flight.

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APU MOUNTS W 1 L



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APU ASSEMBLY DESCRIPTION (3) APU Mounts (continued) APU Front Mounts Each APU front mount is basically comprised of an isolator that connects the APU bracket to the airframe, and includes an elastomer to limit vibration.

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APU ASSEMBLY DESCRIPTION (3) APU Mounts (continued) APU Rear Mounts The APU rear mount has two APU links, which are connected via a common isolator to the airframe attachment bracket.

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APU ASSEMBLY DESCRIPTION (3) Air Intake Duct Assembly And Cooling Air Inlet

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The air intake system supplies sufficient ambient air to the APU air plenum chamber during ground or flight conditions, and its design maintains a low noise level with optimum aerodynamic flow. The air intake system has the following major components: - Rain gutter, - Anti ice fence, - Air intake nose, - Air inlet flap, - Air intake flap actuator, - Air intake duct. An air intake flap is controlled by the ECB, and is fu lly open throughout the APU operation. It will close when the APU is shut down. The rain gutter and the anti ice fence reduce the possibility of foreign object ingestion and prevent against ingestion of fluids and of hot APU gases. The cooling duct is installed in t he tailcone. The cooling air inlet supplies air to the ACOC (Air Cooled Oil Cooler) and helps in the cooling and ventilating of the APU compartment. Air in th e APU compartment moves through the ACOC collecting heat from the oil systems, the air is then mixed with the exhaust gas and discharged overboard. 0 0 0 0 0 0 0 0 1 D 9 4 M L 0 T 0 T K 0 L 1 6 1 6 0 W 1 L



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AIR INTAKE DUCT ASSEMBLY ASSEMBLY AND COOLING AIR INLE T 1

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APU ASSEMBLY DESCRIPTION (3) APU Exhaust Muffler The APU exhaust muffler is composed of: - Exhaust coupling to the APU, - Exhaust muffler body, the muffler body has a sound absorbing material tube, - Extension duct: This duct is the final part of the exhaust muffler and leads the hot gases outside the A/C, - Exhaust muffler suspension: the exhaust muffler suspension has two forward attachment mounts and two rear attachment points: These forward attachments are installed in the exhaust axis. These two rear attachments allow the exhaust muffler expansion. - Exhaust muffler hoisting: there are two attach brackets on the muffler surface for hoisting provisions.

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APU OIL SYSTEM DESCRIPTION (3) General The Oil system makes sure that a pressurized and filtered oil is supplied for the cooling and lubrication of the APU rotating components and the two generators. The ECB monitors the oil temperature, the pressure, and the quantity.

when the oil level reaches the "ADD" mark and reflects approximately 60 hours of operation before the oil reaches the minimum operating level. The oil tank venting system uses an air/oil separator in the accessory gearbox (AGB), which makes sure that the clean air is vented into the exhaust duct.

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Oil Tank Assembly The oil system has two independent systems, one for the APU and the other one for the APU generators. Each one has an independent tank within the Load Gearbox (LGB), that shares a common filler and a common vent system. The total capacity of the two oil tanks is 18.9 l (5 USgal), The APU main oil tank has a capacity of 13.7 l (3.6 USgal), The generator oil tank has a capacity of 5.1 l (1.3 USgal). The oil tank filler is designated to fill the generator oil tank first. When it is full, a float valve closes so the oil flows into the APU oil tank. As the scavenge oil is returned to the tanks without cooling, both oil tanks are referred to as a "hot tank type". Oil cooling is done by an Air Cooled Oil Cooler (ACOC), which is mounted on the eductor assembly. Oil tank quantity can be inspected visually through the oil sight glass (APU main oil tank), Bulls eye (generator oil tank)is electrically monitored by a transmitter on the APU tank. The oil level sensor is used by the ECB to determine the oil level at each APU start. Oil level is sensed in the main (APU) oil tank at the beginning of the start cycle. Advisory fault signals are transmitted by the ECB to the CMS as the oil quantity approaches minimum levels. The first signal is transmitted when usable oil level reaches a preset level. This signal reflects approximately 60 hours of operation before the oil level reaches the "ADD" mark. A second signal is transmitted MAINTENANCE COURSE - T1 & T2 (RR / Metric) LEVEL III - ATA 49 APU

APU OIL SYSTEM DESCRIPTION (3)

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GENERAL - OIL TANK ASSEMBLY ASSEMBLY W 1 L



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APU OIL SYSTEM DESCRIPTION (3) Oil System As the APU and GEN oil systems are independent, each system has a pressure system to deliver the oil to the users, and a scavenge system to return the oil to the tank. In both cases oil cooling is do ne on the pressure supply circuit before the oil goes through the filter.

Oil Pump Assemblies Each oil system contains its own oil pump assembly. The main (APU) oil pump is installed in the AGB and has an oil pressure element and three scavenge pump elements. The generator oil pump is installed in the LGB and has an oil pressure element and two generators scavenge pump elements. Each pressure pump element draws oil from its respective oil tank and pushes it through the syst em. The scavenge pump elements return oil to the tanks.

Cold Start Valves

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Spring-loaded Cold Start Valves Valves (CSV) are installed just downstream of each oil pressure pump. The valves are used as a safeguard against excessive pressure buildup during cold weather operation. The valves open and divert oil either to the pump inlet or the generator oil tank via internal cored paths if the oil pressures exceed preset values.

Air Cooled Oil Cooler 4

The Air Cooled Oil Cooler (ACOC) has two independent core assemblies, one for the APU oil system and one for the generator oil system. Each system has a thermal / pressure relief valve, which lets cold oil bypass the cooler and flow directly to the filter. The design of the pipe-fittings is made so that the oil in the cooler assembly does not drain back to the tank at the APU shut down. 1

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Each core also has a drain valve to let the oil drain at the component removal.

Oil Filters Each system has its own disposable oil filters, which are used for the filtration of the pressure supply, but can be bypassed if the filter clogged. The differential pressure across the filter is monitored. To prevent oil loss at filter replacement, a check valves is installed inside each APU filters housing.

Pressure Regulating Valves The oil system pressures are regulated by a Pressure Regulating Valves (PRV), installed downstream of the oil filter assemblies. The PRV of the GEN oil system returns oil t o the tank to regulate the pressure whereas the PRV of the APU oil system returns oil to its pressure pump inlet.

Dual Oil Pressure Sensors The dual oil pressure sensors send their signals t o the ECB to monitor oil pressure across each filter. The sensors measure oil pressure upstream and downstream of the filters. The upstream and downstream channels are used to calculate the filter differential pressure, and give indication of an impending filter by-pass. The downstream channel gives the oil pressure to the ECB if it fails, and the upstream channel is used as backup signal.

Oil Temperature Sensors Two oil temperature sensors are installed downstream of each oil filter. Inputs from these sensors enable the ECB to monitor the oil temperature of each oil system.

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A380 TECHNICAL TRAINING MANUAL Chip Detectors

Generators Oil Pressure System

The oil systems include three chip detectors, one in the generator oil system and two in the main oil system. The detectors include a bayonet fitting for visual inspection.

Oil is drawn from the tank through an oil strainer by the pressure pump mounted within the LGB, then pressurized oil goes through the electrical chip detector. During cold weather operation, the CSV gives a safeguard against excessive pressure build up through the pu mp. When the valve opens oil goes back to the tank. Oil from the pump flows through an ACOC mounted on the eductor assembly. Cooled oil from the ACOC then goes through the oil filter mounted on the LGB. A bypass valve is installed around the oil filter to keep oil flowing in the event of filter blockage. Downstream of the filter, oil pressure and temperature si gnals are sent to the ECB. PRV bypasses oil pressure directly to the oil tank thereby maintains a constant oil pressure. Pressure oil then flows to the oil inlet ports on the generators and provides generator lubrication and cooling.

APU Lubrication Functional Description The APU oil system is composed of the pressure and the scavenge oil circuit for the main APU and the GEN oil systems.

APU Oil Pressure System

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Oil is drawn from the tank through an oil strainer by the pressure pump. The output of t he pressure pump is regulated by the PRV, which returns the excess of oil to the pump inlet. During starting when the oil is cold, the CSV will also return oil to the pump inlet to prevent excessive pressure in the system. The pressurized oil is directed through the ACOC to the pressure filter but if the oil temperature is already low, it can by-pass the cooler through the thermal / pressure relief valves. Pressurized oil will flow through the filter, but if the filter clogs the by-pass will open for unrestricted oil flow. Pressurized oil is delivered to the load gearbox accessory gearbox, and bearing using a combination of pressure of pressure jets and oil mist.

APU Oil Scavenge System 0

The scavenge system returns the oil to the APU main oil tank. The load gearbox scavenges pumps take oil from the load gearbox sump, which includes the oil from the bearing No 0. Oil from the No 4 bearing is pumped by its own scavenge pump to the accessory gearbox, which also receives scavenge oil from No 1, 2 and 3 bearings under gravity and secondary air pressure. This oil is then pumped by the accessory gearbox scavenge pump back to the tank. 0

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Generators Oil Scavenge System Two scavenge pumps, one for each generator, return the oil from the generators tank. The oil temperature is monitored at the scavenge outlet

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OIL SYSTEM & APU LUBRICATION FUNCTIONAL DESCRIPTION 1

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APU FUEL SYSTEM DESCRIPTION (3) General The APU fuel system has components that automatically supply proper APU acceleration and to maintain a constant operating speed under varying load and environmental conditions. The APU fuel circuit can be divided i nto two separated syst ems: the APU fuel control system and the fuel distribution system. The APU fuel control system is composed of the Fuel Control Unit (FCU) with the integrated fuel pump, the fuel filter and the low fuel pressure switch. The FCU is electrically connected to the ECB. The fuel distribution system feeds the fuel t o the SCV and IGV actuators and to the fuel nozzles through the flow divider and the primary and secondary fuel manifolds. The Fuel Control Unit (FCU) is mounted on an AGB drive pad for the fuel pump shaft.

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APU FUEL SYSTEM DESCRIPTION (3)

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APU FUEL SYSTEM DESCRIPTION (3) Fuel Manifolds Primary and secondary fuel manifolds deliver metered fuel from the flow divider to the fuel nozzles. The manifolds are flexible lines, which surround the gas generator case and are connected to the primary or secondary side of each fuel nozzles.

Flow Divider And Dump Valve The flow divider is installed on the fuel inlet manifold adapter located at the 6 o'clock position on the gas generator case. It schedules the metered fuel from the FCU between the primary and secondary fuel manifolds.

Fuel Nozzles Each of the fourteen duplex fuel nozzles has separate primary and secondary fuel injectors. The primary fuel injectors are installed inside the secondary fuel injectors and atomize the fuel for starting. Once the fuel pressure reaches the required level, the secondary injectors supply additional fuel required for sustained operation.

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APU FUEL SYSTEM DESCRIPTION (3) Fuel Control System Description The APU fuel control system functions are to provide the metered fuel flow, Inlet Guide Vane Vane (IGV) and Surge Control Valve Valve (SCV) actuation . Fuel is supplied to the APU from the aircraft fuel system. The major components of the APU fuel control system are: - Low fuel pressure switch, - The Fuel Control Unit (FCU), which has a fuel pump, a fuel metering valve, and a shut-off solenoid, and an actuator regulator. - Fuel filter and the fuel filter impending bypass switch.

Low Fuel Pressure Pressure Switch A low fuel pressure switch is installed at the inlet to the fuel pump. It opens when the fuel pressure increases, if low fuel pressure occurs the switch is closed and the low fuel pressure signal is transmitted to the ECB.

Fuel Pump

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The fuel pump is integrated into the FCU and is mainly composed of a boost stage, disposable filter and a High Pressure gear type pump. The pump includes a pressure relief valve to protect the HP pump in case of overpressure.

Fuel Filter And Impending Bypass Switch 0

The disposable fuel filter protects the fuel pump gear stage and metering components from contamination in the fuel supply. The filter is installed before the fuel pump gear stage. A pressure P switch senses the fuel pressure across the filter filter and sends an impending filter bypass signal when the filter element becomes clogged. A bypass valve lets the fuel bypass the filter. Impending fuel filter bypass signal is sent to the ECB. 1

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Fuel Metering Valve A torque motor commanded by the ECB modifies the metering valve position in order to control metered fuel flow. A Pressure Regulating bypass Valve Valve (PRV) keeps the differential pressure across the metering valve constant. The flow from the metering valve goes through a shutoff valve before it goes to the flow divider. During either a normal or a protective shutdown, the ECB de-energizes the shutdown solenoid to stop the fuel flow to complete the APU shutdown. This solenoid opens an orifice to shunt metered fuel pressure and sends it to the shutoff valve, which moves to the closed position.

Actuator Regulator The Actuator regulator is a pressure regulator. regulator. The regulator maintains a constant pressurized fuel supply to the SCV actuator and IGV actuator.

Fuel Drain And Vent Valve The fuel drain and vent valve is installed on the APU inlet fuel line. This valve is used for a venting function to bleed the aircraft supply line.

Fuel System Functional Description During the APU start sequence, the ECB energizes the FCU solenoid valve. The FCU fuel pump draws fuel from the aircraft supply. Fuel pressure opens the FCU shut off valve and fuel flows through the FCU to the flow divider. Fuel pressure overcomes the flow divider dump valve spring and fuel can flow through the primary fuel manifold to the fourteen primary fuel injectors. At the relevant pressure, the flow divider valve opens the secondary fuel manifold to the fourteen secondary fuel injectors. APU FUEL SYSTEM DESCRIPTION (3)

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A380 TECHNICAL TRAINING MANUAL During operation, fuel is metered by a signal sent to the FCU torque motor by the ECB. Pressurized fuel is used to actuate the IGV actuator and SCV. The FCU actuator regulator regulates constant fuel pressure to these components. At APU shutdown, the ECB de-energizes the solenoid valve then the fuel shut off valve closes. A dump valve is included in the flow divider. During APU shutdown, a spring moves the valve and causes a blockag e of the fuel inlet p ort. Valve Valve movement also connects the primary and secondary manifolds to the dump valve port and the remaining fuel is vaporized into the exhaust.

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APU AIR SYSTEM DESCRIPTION (3) General APU Bleed Air System, APU Secondary Air System, APU Compartment Cooling.

APU Bleed Air System The functions of the bleed air system are: Supply APU bleed air to the aircraft Environmental Control System (ECS) and to the Main Engine Start (MES), Supply load compressor surge protection.

APU Secondary Air System The secondary air system uses pressurized P3 air to seal the bearing compartments and to cool the turbine disks.

APU Compartment Cooling The cooling air system supplies air to the ACOC and helps in the cooling and ventilating of the APU compartment.

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APU AIR SYSTEM DESCRIPTION (3)

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APU AIR SYSTEM DESCRIPTION (3) APU Compartment Cooling The cooling air system supplies air to t he ACOC ACOC and helps in the cooling and ventilating of the APU compartment. It uses the eductor to pull air from the APU compartment through the ACOC. Behind the ACOC, the APU exhaust flow causes a low-pressure, and then the cooling air is mixed with the exhaust gas and is discharged overboard. To maintain a normal pressure into the APU compartment an APU pressure relief flap is installed on the left maintenance door.

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APU AIR SYSTEM DESCRIPTION (3) APU Bleed Air System The bleed air system includes the following components: Bleed Valve (BV) Surge Control Valve (SCV), Inlet Gu ide Vane Actuator (IGVA), (IGVA), Load Compressor (LC) air flow sensor, Load Compressor Delta Pressure sensor, Load Compressor static pressure sensor, LC Air flow sensor, APU eductor assembly.

Bleed Valve The Bleed Valve has a butterfly valve controlled by a solenoid (normally closed solenoid). The ECB commands the opening of the sol enoid then the P3 pressure opens the Bleed Valve. Valve. The two electrical position switches send to the ECB a signal indicating the position of the valve (open or closed).

Surge Control Valve

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The Surge Control Valve (SCV) has a butterfly valve operated by a fuel driven actuator. The SCV actuator receives an electrical command from the ECB. The ECB positions the valve based upon input from the Load Compressor (LC) Static Pressure and Delta Pressure Sensors. A Linear Variable Differential Transducer (LVDT) sends the valve position feedback to the ECB.

Inlet Guide Vane (IGV) Actuator L

The IGV actuator controls the fuel pressure to position the variable Inlet Guide Vanes (IGV). The ECB operates the IGV torque motor in response to SCV position and aircraft demand. L

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A position transducer in the actuator sends the IGV actuator feedback to the ECB.

LC Air Flow Sensor The LC Air Flow Sensor is installed on the Load Compressor scroll and has a total pressure port and static pressure port. The total pressure port gives the sense air pressure to the LC Delta Pressure Sensor. The static pressure port gives a sense for static pressure to both the LC Static and LC Delta Pressure Sensors.

LC Delta Pressure Sensor The Delta Pressure sensor gives a load compressor differential pressure input to the ECB for Surge Control Valve control.

LC Static Pressure Sensor The Static Pressure sensor gives a load compressor static pressure input to the ECB for Surge Control Valve and a delivery pressure indication to the airframe.

APU Bleed Air System Interface The ECB is connected to the ADCN to send information to other aircraft systems through the AFDX network. The ECB sends the APU BLEED VAL VALVE VE CLOSED sign al to the CPIOM Interface. This discrete signal goes to the Pneumatic Air Distribution System (PADS) (PADS) application h osted by CPIOM-A (PADS application is a part of the ATA 36).

APU Bleed Air Functional Description During the st art sequence, the Bleed Valve Valve remains de-energized closed and the SCV is energized open. Upon completion of the start sequence, the "APU Available" indication is shown on the ECAM and the APU bleed can be selected. APU AIR SYSTEM DESCRIPTION (3)

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A380 TECHNICAL TRAINING MANUAL Upon receiving a bleed command from the aircraft, the ECB energizes the Bleed Valve solenoid open making P3 air open the butterfly valve. At the same time, the SCV is commanded closed. The ECB uses a position feedback signals from both the Bleed Valve and Surge Control Valve to determine the valve positio ning. When MES is selected, the ECB commands the SCV open. The ECB controls the valve position in order to maintain a preset Load Compressor discharge airflow value. The ECB uses inputs from the LC Delta Pressure and Static Pressure Sensors to determine the Load Compressor discharge airflow. Based upon the inputs from the LC Delta and Static Pressure Sensors, the ECB is able to detect an impending compressor surge. If an impending surge is detected, the SCV is commanded fully open. During APU cool down and shutdown, the ECB closes the Bleed Valve and opens the SCV.

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APU INTERFACES DESCRIPTION (3) APU Interfaces

- Engine Electronic Controller (EEC),

The ECB is a single channel FADEC (Full-Authority Digital Engine Control) that gives automatic operation of the APU, from APU start procedure to APU Shut-Down The ECB interchanges information with the aircraft through an Avionics Full Duplex (AFDX) Ethernet data link. This system supplies: - Control for the automatic operation of the APU, - Control for the APU at a governed speed, - Automatic cool and stop sequences, - Protection of the APU from a failure or an overload (Protection Shutdown), - Monitored Line Replaceable Units (LRUs) and the APU parameters through the Data Memory Module (DMM), - APU System Tests. The ECB has a BITE (Built-in-Test Equipment) that does checks and monitors.

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ECB Interfaces With The Aircraft Systems The ECB interchanges information with the following Aircraft systems: - Integrated Control Panel (ICP), - Air Generation System (AGS), - Generator and Ground Power Control Unit (GGPCU), - Fuel Quantity & Management System (FQMS), - Flight Warning System (FWS), - Control and Display System (CDS), - Flight Data Recording System (FDRS), - Landing Gear Extention Retraction System (LGERS), - Air Data Inertial Reference System (ADIRS), - Bleed Air System (Pneumatic Air Di stribution System, PADS), (Engine Bleed Air System, EBAS), (OverHeat Detection System, OHDS), - Onboard Maintenance System (OMS), MAINTENANCE COURSE - T1 & T2 (RR / Metric) LEVEL III - ATA 49 APU

APU INTERFACES DESCRIPTION (3)

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APU INTERFACES DESCRIPTION (3) APU Data Memory Module (DMM) The Data Memory Module (DMM) gives APU life data related to an APU, and keeps the data even if the ECB is replaced. The DMM receives its data from the ECB (Non Volatile Volatile Memory, NVM). The data kept in the DMM are the following ones: - APU fault Information, Operational Data: - APU operation hours, - Number of APU Starts, - Number of APU Main Engine Starting (MES) cycles, - MES operation time, - ECS operation time, - Number of unusual shutdowns, - No load operation Time, - EGT time limit, - EGT trim. Identification Data: - APU serial number, - ECB software number. 1 0 0 0 0 0 0 0 0 5 D 9 4 M L 0 T 0 T K 0 L 1 6 1 6 0 W 1 L



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APU IGNITION & STARTING DESCRIPTION (3) Functional Description

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The ignition and starting system supplies the electrical and mechanical energy necessary to initiate and sustain the combustion process during the APU start sequence. The system becomes dormant as soon as the APU is able to sustain combustion. The ignition and starting system includes the following components: - APU switch (cockpit), - Starter, - Ignition exciter, - Ignition cables, - Igniters. During the APU start and stop sequences, the ECB gives the automatic operation. It governs the speed, the temperature, the Inlet Guide Vane (IGV), the IGV actuat or, the Surge Control Valve Valve (SCV) and t he Fault detection and accommodation (BITE). When the APU switch is pushed "ON", the ECB initiates the power up sequence, and commands the inlet flap to open. Once all the pre-start conditions have been satisfied, the starter control into the ECB energizes the main and back up start contactors. Then the APU TRU or the APU battery supplies t he starter motor through the APU start DC bus. To control the APU start sequence the ECB uses inputs from N1 and N2 dual speed coil speed sensors and Exhaust Gas Temperature (EGT) sensors by comparing speed and the EGT rises against preset values. During the APU operation, speed sensor inputs are used by the ECB to maintain 100% N1 engine speed and give N1 and N2 overspeed protection. EGT Sensors are used by the ECB to maintain the engine EGT within acceptable limits by controlling the IGV, the Fuel Metering Valve Valve (FMV) and the fuel shut-off solenoid if a protective shutdown signal occurs. 1 L


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APU IGNITION & STARTING DESCRIPTION (3) APU Start Sequence

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The start sequencing includes the following logic: The APU push button "ON" signal initiates power to the ECB, triggering a series of ground functional checks. After a successful initial built-in-test ch eck of all hardware functions, the ECB signals an "APU START" command when the inlet flap is fully open. The ECB sets the IGV position to 47% open and sets SCV to open. It energizes the two start contactors that provide electrical power to the starter motor. As the start sequence begins and the engine spools up (8% N2), the ECB establishes start fuel flow energizing the FCU shut off valve and then igniters are also energized. Following completion of a successful start, the starter and igniters are de-energized (40% N2) and the APU continues to accelerate the speed. When the engine speed N2 reaches 55%, the IGVs are set to the minimum position As the free turbine reaches its reference speed, the N2 governor takes over the control and manages the final acceleration and stabilization to approximately 86%N2. The engine 86% N2 is a "NO LOAD" speed, which is maintained to control 100% N1 (N1 reference speed). Start parameters such as initial start flow and acceleration rates are adjusted based on ambient conditions and oil temperature. As applicable during the start and run-up sequence, pneumatic and generator loading available signals are indicated. 0 T 0 T K 0 L 1 6 1 6 0 W 1 L



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APU IGNITION & STARTING DESCRIPTION (3) APU Normal Shutdown The normal APU shutdown cycle begins with an "APU SWITCH OFF" signal that indicates removal of the pneumatic compressor load and initiation of the shutdown cycle. The ECB closes the bleed valve and starts a 50 second cool down period. When the N1 speed decreases to 95% the "APU AVAIL" indication disappears. At the end of the cool down period, the ECB decreases N1 speed to 67% and moves the IGVs to the 47% open position over the next 10 seconds. To shut down the APU the ECB simulates a N1 overspeed condition, modulating the FCU torque motor so there is no more fuel flow. When the system detects the simulated overspeed, it de-energizes the FCU shutdown solenoid to stop all fuel flow. At 20% N2 speed the aircraft fuel supply is closed. When the N2 speed decreases to 7%, the inl et flap is closed and the ECB is de energized. The ECB monitors the complete shutdown process; if the protection system fails the ECB also sets the applicable fault in the DMM.

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APU IGNITION & STARTING DESCRIPTION (3) APU Protective Shutdowns Each protective shutdown signal results in immediate APU shutdown by de-energizing the FCU shutdown solenoid. The cause of any protective shutdown is stored in the DMM and is sent to the aircraft maintenance computer for the APU maintenance and fault isolation. The difference between protective shutdown and a normal shutdown is that there is no cool down cycle. A protective shutdown is initiated whenever the following conditions are encountered on ground: - A/C Emergency Stop Discrete (input from airframe), - N1 Overspeed (N1 > 106.3%), - N2 Overspeed (N2 > 102.5%), - N1 Underspeed (N1 < 88.5%), - Loss of N1 Overspeed protection, - Loss of N2 Overspeed protection, - Low Main Oil Pressure (< 55 psig), - Low Oil Pressure Gen (< 48 psig), - Main High Oil Temperature (> 135 C), - High Oil Temperature Gen (> 146 C), - Gen. No. 1 High Oil temperature (> 164 C), - Gen. No. 2 High Oil Temperature (> 164 C), - Engine Oil Filter Bypass (Shutdown in event of oil filter bypass), - Generator Oil Filter Bypass (Shutdown in event of oil filter bypass), - EGT Overtemperature (> 900 C for 30 sec and > 934 C), - Significant ECB Fault, - Loss of Main DC Supply (except when starting), - Fuel Control Unit FCU fault, - Reverse Flow (Bleed Valve not closed), - Both SCV and Bleed Valve Valve Closed (Bleed Valve closed and SCV 90% closed or if N1 > 20% and BV not fully open and SCV 40%), - Surge Protection (P STA STATique rate of change<100 psia / sec).

A protective shutdown is initiated whenever the following conditions are encountered in flight: - A/C Emergency Stop Discrete (input from airframe), - N1 Overspeed (N1 > 106.3%), - N2 Overspeed (N2 > 102.5%), - Significant ECB Fault, - Fuel Control Unit FCU fault, - Loss of Main DC Supply (except when starting), - Loss of N1 Overspeed protection, - Loss of N2 Overspeed protection, - Both SCV and Bleed Valve Valve Closed (Bleed Valve closed and SCV 90% closed or if N1 > 20% and BV not fully open and SCV 40%), - N2 corrected limit exceeded for min fuel flow (function of altitude).

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APU SYSTEM MAINTENANCE (3) APU Tests The APU provides the following interactive tests: - APU tests, - APU safestore function, - APU status and configuration, These tests are launched from the OMS HMI.

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APU SYSTEM MAINTENANCE (3)

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APU SYSTEM MAINTENANCE (3) APU Menu The APU MENU page of the Onboard Main tenance System (OMS) gives the following functions: APU tests: . System Test . Air Intake Flap Test . Oil StatusTest . Dry Crank Test . Wet Crank Test APU Status Data & Configuration: . APU Status Data . APU History Data . Software Pin Programming . Shutdown Report Data APU Safestore Function: . ECB Shop Data Memory.

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COMPONENT LOCATION (3) APU A/C Zone 315 Zone 162 Zone 252

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COMPONENT LOCATION (3)

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AIRBUS S.A.S. 31707 BLAGNAC cedex, FRANCE STM REFERENCE L1W06161 APRIL 2006 PRINTED IN FRANCE AIRBUS S.A.S. 2006 ALL RIGHTS RESERVED AN EADS JOINT COMPANY WITH BAE SYSTEMS

Level III - Ata 49 Apu

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