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Questions and Answers
What is the primary function of the gearbox in relation to the APU?
Which of the following is not an APU driven accessory?
What does the lubrication module in the APU system primarily support?
Which component is responsible for generating electrical power in the APU?
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What role does the APU gearbox play in relation to the electrical generator?
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What components are included in the APU mounting system?
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How many vibration isolators are part of the APU mounting system?
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What purpose does the APU mounting system serve?
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Which of the following statements accurately describes the number of rod assemblies in the APU mounting system?
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What type of mounting system is used for the APU installation?
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Which component is NOT part of the APU mounting system?
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How many bonding straps are included in the APU mounting system?
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What is the function of the structure brackets in the APU mounting system?
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What is the purpose of the visual clogging indicator in the filter housing?
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What happens when either or both differential pressure switches are actuated?
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At what differential pressure does the bypass valve open?
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What do the bypass valves in the circuits allow for?
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What is the range of the visual indication activation pressure for the clogging indicator?
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What is the purpose of the APU Fuel Control Unit (FCU)?
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What component distributes fuel to the combustion chamber?
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Which aircraft families are mentioned in the document?
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On which displays can APU fuel system indications be found?
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What is primarily indicated by the APU fuel system indicators?
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Which of the following components is used for operation with inlet guide vanes?
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What is the date on the document mentioned?
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How many fuel nozzles feed fuel into the combustion chamber?
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What is the recommended waiting time before checking the APU oil level after shutdown?
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What is indicated as a failure condition for the APU that allows it to be dispatched?
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Which APU model is referenced in the maintenance briefing?
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What should be avoided for an accurate oil level indication?
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What does MEL stand for in this context?
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What action can be taken regarding the inlet when there is an inlet actuator failure?
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Which of the following is NOT a requirement for checking the APU oil?
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Which page number contains the APU information in the training manual?
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Which condition is essential for maintaining accurate oil servicing?
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What is a consequence of failing to check APU oil promptly after shutdown?
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What structure supports the rotating group in the APU system?
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Which component primarily increases air pressure through the combustion chamber?
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How is the variable IGV assembly controlled within the APU system?
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What design feature of the bearings in the APU helps to reduce vibrations?
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What is the operational speed of the rotating group in the APU system?
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What assembly is responsible for regulating the airflow into the load compressor?
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Which bearing type is located at the forward end of the rotating shaft assembly?
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What is the primary function of the load compressor impeller in the APU?
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What does the load compressor module primarily supply to the air conditioning pneumatic system?
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Which engine model is specified for the A330-200/300 in the technical manual?
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In the context of APU maintenance, what does APU stand for?
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What is the primary function of the power section of the GTCP331-350 system?
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What type of training services does the manual indicate the content is designed for?
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What does not pertain to the APU General Directives, based on the provided content?
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What is indicated as the document's date of revision?
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Which component does the APU provide shaft power to drive?
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What should be done if the APU inlet is deactivated in the CLOSED position?
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How many turns of the manual drive are required for one full travel of the inlet flap?
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What action must be taken to start the APU after the inlet is in the OPEN position?
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Why should a torque wrench be used when moving the actuator manually?
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What is the maximum duration the APU can remain operational with the inlet deactivated OPEN as per the MEL?
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What item should be used to create a dummy connector for identification?
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What is the first step in the deactivation procedure of the APU inlet?
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What should be checked after starting the APU to ensure it’s operating normally?
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What role does the torque-motor metering valve play in the APU fuel system?
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During which sequence is the fuel solenoid valve controlled to open?
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Which of these signals does the Electronic Control Box (ECB) utilize for managing the fuel system during normal operations?
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What component is primarily monitored through a pressure switch installed at the FCU inlet?
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Which statement accurately describes the operational control during the shut-down sequence?
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How is the fuel flow during the starting phase controlled?
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What is the primary purpose of the fuel muscle pressure in the APU system?
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What happens to the fuel flow when a visual filter-clogging indicator indicates contamination?
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What is the function of the oil cooler and thermal bypass valve during APU operation?
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In which aircraft models is the air/oil separator relevant?
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What is the purpose of the thermal bypass valve?
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Which of the following statements accurately describes the operational condition of the thermal bypass valve?
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What type of training is associated with the CMQ - SA family to A330-200/300?
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What is an implicit result of optimal oil temperature maintenance in the APU?
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What is a significant operational requirement for the APU oil system?
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What is indicated by the operational status of the oil cooler in the APU?
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What are the necessary conditions for APU bleed air to be delivered?
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What is the function of the gearbox-driven fan mentioned in the context of APU accessory cooling?
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Which component is responsible for sending a signal to energize the APU bleed valve solenoid?
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What happens when the APU inlet pressure altitude is above the specified maximum?
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How does the APU bleed valve operate when the APU is functioning correctly?
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What happens to the solenoid de-oiling valve when specific start conditions are met?
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During which phase does the solenoid de-oiling valve also open aside from the initialization conditions?
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What primarily influences the opening of the solenoid de-oiling valve?
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What is the role of the lower part of the APU gearbox?
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Which of the following statements is true regarding the solenoid de-oiling valve?
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In the context of the APU system, what is the consequence of low fuel temperature?
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What component prevents oil overflow in the APU system?
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What types of aircraft are compatible with the A330-200/300 technical training manual?
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What type of system component is primarily used for filling oil in the APU?
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What aspect of the APU operation is considered critical when determining the solenoid de-oiling valve's behavior?
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Which APU model is referred to within the context of the gearbox description?
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What does an OIL LEVEL: CHECK indication on the APU SERVICE DATA page signify?
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What critical function does the air/oil separator fulfill in the APU system?
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Which procedure must be followed if the oil level is indicated as LOW on the APU SERVICE DATA page?
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What safety step is essential before servicing the APU oil?
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What maintenance-related document is indicated by the presence of the revision date?
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Which of the following components is part of the APU assembly for handling oil?
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During oil servicing, what is the final step of the pressure filling procedure?
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What aspect of the APU system's gearbox is NOT mentioned in the provided content?
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What signifies that the oil level is deemed sufficient on the EIS and CMS?
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Which APU maintenance practice is indirectly emphasized in relation to the oil management?
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What is the recommended action when the sight glass indicates overfilled oil?
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Which of the following is NOT a required step when conducting the gravity fill procedure?
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What does the ADD mark on the oil reservoir sight glass indicate?
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What is the total capacity of the oil reservoir in liters?
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Which of the following components is not included in the gearbox?
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What is one function of the low oil quantity switch in the gearbox?
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What is the role of the air/oil separator within the gearbox?
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Which component provides an indication of oil temperature within the gearbox?
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Which of the following parts is internally supplied with oil in the gearbox?
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What is the primary function of the electrical chip detector in the gearbox?
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Which feature of the gearbox aids in monitoring the oil level?
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Study Notes
APU Oil Level Checks
- Wait 5-15 minutes after the APU shutdown before checking oil level
APU Gearbox Function
- Transmits shaft power to APU accessories and APU electrical generator
- Contains APU oil reservoir
- Drives APU generator, lubrication module, and Fuel Control Unit (FCU)
APU Inlet Actuator Failure
- APU can be dispatched per Minimum Equipment List (MEL) with the inlet CLOSED or OPEN
APU Mounts System
- Installed on a three-point vibration-insulated mounting system
- Components:
- Seven structure brackets
- Seven rod assemblies
- Three APU mount brackets
- Three vibration isolators
- Two bonding straps
APU Fuel System
- Fuel flows to the combustion chamber through 12 fuel nozzles
- Filter is used in lubrication and scavenge circuits:
- Replaceable and non-cleanable
- Housing equipped with a visual clogging indicator and a differential pressure switch
- Differential pressure switches provide a real-time indication of impending bypass of the corresponding filter
- Switch actuation will cause an APU auto-shutdown (inhibited during flight)
- Bypass valves are installed to allow continued APU operation with a contaminated or blocked filter
- Valves bypass the filter during auto-shutdown inhibition
- Differential pressure switch actuates at 35 +/-5 psid
- Bypass valve opens at 65 +/-5 psid
- Visual clogging indicator provides pre-warning of potential filter blocking
APU Inlet Deactivation
- The APU is inoperative when the inlet is closed.
- The APU can only be operated with the inlet open for a maximum of 10 days, according to the Minimum Equipment List (MEL).
- The inlet flap actuator has a manual drive which can be used to move the APU inlet to the required position.
- The APU inlet actuator is located near the APU inlet on the left side of the fuselage.
- The actuator requires 87 turns of the manual drive for one full travel of the APU inlet flap.
APU Inlet Deactivation Procedure
- Access the actuator.
- Disconnect the actuator electrical connector and install a blanking cap.
- Use the manual drive to move the inlet flap to the required position, use a torque wrench to prevent damage to the actuator during this step.
- Placard the APU inoperative if the inlet was deactivated closed.
- If the inlet was deactivated open, install a jumper lead to close the circuit to allow the APU to start.
- For easy identification, make a dummy connector and paint it red.
- Close the access door and perform the APU operational test.
APU Operational Test
- Perform the BITE (Built-in Test Equipment) test.
- Check the SERVICE DATA.
- Start the APU and check for normal operating parameters.
APU System Overview
- The GTCP331-350 APU system is composed of the power section, the load compressor, and the control and monitoring systems.
- The power section supplies shaft power to the load compressor, the accessory drive gearbox, and the electrical generator.
- The load compressor supplies compressed air to the aircraft pneumatic system.
- The control and monitoring system controls the fuel system, monitors the APU systems, and manages the starting sequence.
APU Power Section
- The power section is composed of the engine compressor, the combustion chamber, and the rotating group.
- The engine compressor is a two-stage centrifugal compressor that increases and guides air pressure into the combustion chamber.
- The combustion chamber is where fuel is burned, providing energy to the engine.
- The rotating group includes the centrifugal compressor and turbine, and is supported by ball and roller bearings.
APU Load Compressor
- The load compressor includes the Inlet Guide Vanes (IGV) assembly, the load compressor impeller, the load compressor diffuser, and the scroll.
- The IGV assembly modulates the amount of air supplied to the load compressor by adjusting the vane position angles.
- The load compressor impeller is a single stage impeller for the APU.
- The load compressor diffuser slows down the airflow, increasing pressure and allowing for cooler temperatures.
- The scroll collects the airflow from the diffuser and directs it to the gearbox.
APU Fuel Control Unit (FCU)
- The FCU supplies and regulates fuel for the APU operation.
- It is composed of an inlet filter, a high pressure pump, a high pressure filter, a torque-motor metering valve, and a shut-off valve.
- The fuel schedule is controlled by the Electronic Control Box (ECB) which schedules the fuel flow for several stages including starting, on-speed operation, and shutdown.
APU Fuel System
- APU fuel muscle pressure is used to drive the surge control valve and load compressor IGV actuators.
- Fuel shut-off is managed by the ECB controlling a solenoid valve.
- The flow divider separates the fuel flow into primary and secondary flows.
APU Oil System
- The oil cooler and the thermal bypass valve maintain the proper oil temperature during operation.
APU Bleed Air Operation
- APU bleed air is delivered when the APU is running above 95% speed, the bleed switch is selected, no bleed leak is detected, and the APU inlet pressure altitude is below 25,000 feet.
- Bleed Monitoring Computers (BMCs) detect leaks and signal the Electronic Control Box (ECB) to energize the APU bleed valve solenoid, which opens the valve.
- The ECB monitors the oil level status through the low oil quantity switch when the A/C is on the ground, the APU is off, and power-up initialization is finished.
- The oil level status is indicated on the Engine Indication System (EIS) and the Centralized Maintenance System (CMS).
- An OIL LEVEL: OK indication on the CMS APU SERVICE DATA page and no indication on the ECAM APU page means the oil level is sufficient.
- An OIL LEVEL: CHECK indication on the CMS APU SERVICE DATA page and a CHECK OIL LEVEL message on the ECAM APU page indicates the oil level allows for 60 hours of APU operation.
- An OIL LEVEL: LOW indication on the CMS APU SERVICE DATA page and a LOW OIL LEVEL message on the ECAM APU page indicates the oil level is at its minimum and needs to be refilled.
APU Oil Servicing
- Prior to servicing, shut down the APU and open the access doors.
- Use operator-approved oil for servicing.
- Options include gravity fill and pressure fill procedures.
- The gravity fill method is the most common.
APU Gearbox Description
- The lower part of the gearbox serves as an oil reservoir with a capacity of 8.5 liters.
- The gearbox features:
- Gravity and pressure fill ports
- Oil level sight glass
- Low oil quantity switch
- Low oil temperature sensor
- Oil heater
- Electrical chip detector
- Air/oil separator
- The cooling fan pad and starter motor pad are internally supplied with oil.
- The oil heater has a temperature switch and a nickel-iron alloy coil.
APU Solenoid De-Oiling Valve
- The valve opens to allow air to enter the inlet side of the pressure pump under specific start conditions (depending on oil and fuel temperatures, and aircraft altitude).
- The valve also opens during APU shutdown.
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Description
This quiz covers essential aspects of Auxiliary Power Unit (APU) maintenance, including oil level checks, gearbox functionality, inlet actuator handling, mounting systems, and fuel systems. Understand the key components and their functions to ensure proper APU operation and maintenance.
