Podcast
Questions and Answers
What component does the GARRET 36-280 use for monitoring and control?
What component does the GARRET 36-280 use for monitoring and control?
- Full Authority Digital Electronic Control (FADEC) (correct)
- Basic Control Unit
- Manual Control Panel
- Analog Control System
What happens when the low oil pressure light illuminates?
What happens when the low oil pressure light illuminates?
- The APU will automatically shut down. (correct)
- The APU continues to operate normally.
- The maintenance light illuminates.
- A warning is sent to the cockpit.
Which APU model has a 60-second cooldown option?
Which APU model has a 60-second cooldown option?
- GARRET 36-280
- SUNDSTRAND APS 2000
- GARRET 85-129 (correct)
- None of the above
What does the APU fire warning light indicate?
What does the APU fire warning light indicate?
Which model uses a maintenance light to indicate non-critical failures?
Which model uses a maintenance light to indicate non-critical failures?
What happens when the APU turbine speed exceeds its allowable rpm?
What happens when the APU turbine speed exceeds its allowable rpm?
What type of compressor does the GARRET 85-129 feature?
What type of compressor does the GARRET 85-129 feature?
What does the APU fire control handle do when pulled?
What does the APU fire control handle do when pulled?
What type of impellers does the SUNDSTRAND APS 2000 use?
What type of impellers does the SUNDSTRAND APS 2000 use?
Which of the following indicates a critical failure in the APU?
Which of the following indicates a critical failure in the APU?
What is the purpose of the APU in an airplane?
What is the purpose of the APU in an airplane?
How much KVA can the APU generator supply during flight operation?
How much KVA can the APU generator supply during flight operation?
What feature automatically transfers power to an alternate generator when needed?
What feature automatically transfers power to an alternate generator when needed?
Which component converts 115V AC to 28V DC power?
Which component converts 115V AC to 28V DC power?
What is the first action taken when ground power is available?
What is the first action taken when ground power is available?
What is the maximum load displayed by the generator AC ammeter?
What is the maximum load displayed by the generator AC ammeter?
Which of the following statements is true about operating the APU bleed air?
Which of the following statements is true about operating the APU bleed air?
What happens to the APU in the event of overspeed?
What happens to the APU in the event of overspeed?
What is a feature of the APU designed to minimize exhaust noise heard by passengers?
What is a feature of the APU designed to minimize exhaust noise heard by passengers?
What is the role of the Constant Speed Drive (CSD) in the electrical power system?
What is the role of the Constant Speed Drive (CSD) in the electrical power system?
Flashcards
APU Generator Capacity
APU Generator Capacity
The APU generator provides 60 KVA of power on the ground and 50 KVA during flight.
Bus Transfer Switch (Automatic)
Bus Transfer Switch (Automatic)
Automatically switches between generators to maintain power if one fails.
Ground Power Switch
Ground Power Switch
Controls the use of external power source. When ON, engine/APU generators are disabled.
APU Function
APU Function
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Constant Speed Drive (CSD)
Constant Speed Drive (CSD)
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Generator Load Display
Generator Load Display
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APU Starting Method
APU Starting Method
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Automatic Bus Transfer System
Automatic Bus Transfer System
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APU Shutdown Triggers
APU Shutdown Triggers
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APU Noise Reduction
APU Noise Reduction
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Garret 85-129 APU
Garret 85-129 APU
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Garret 36-280 APU
Garret 36-280 APU
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Sundstrand APS 2000 APU
Sundstrand APS 2000 APU
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APU Maintenance Light (non-critical)
APU Maintenance Light (non-critical)
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APU Low Oil Pressure
APU Low Oil Pressure
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APU Fault Light (critical)
APU Fault Light (critical)
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APU Overspeed
APU Overspeed
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AC Ammeter
AC Ammeter
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Exhaust Gas Temp Indicator
Exhaust Gas Temp Indicator
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APU Fire Protection
APU Fire Protection
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Study Notes
Electrical Power System
- Three electrical generators power the aircraft (two engine driven, one APU driven)
- APU provides self-sufficiency, supplying on-ground electrical power
- Automatic Bus Transfer System increases electrical power reliability
- Onboard power system annunciator and test modules monitor and detect malfunctions
Constant Speed Drive (CSD) and Generator
- CSD and generators are driven by each engine to produce 115 volts, 400Hz, three-phase AC power.
- Each CSD supplies 50 KVA.
- A Variable Speed Constant Frequency (VSCF) generator also produces 50 KVA
- Transformer/Rectifier units convert 115V AC to 28V DC for other systems.
- The APU generator provides 50/60 KVA (ground/flight).
APU Generator Bus Switches
- Connecting APU generator to generator buses #1 or #2.
- Disconnecting from #1 or #2 generator buses.
- APU can supply power to both generator buses during ground operations. During flight, APU can only power one generator bus.
Ground Power and Bus Transfer
- Enables use of ground power if available
- Tripping engine/APU generators from buses when using ground power.
- Automatic bus transfer system switches to the opposite generator if needed.
- Isolates DC systems when the transfer switch is shut off.
Auxiliary Power Unit (APU)
- Garrett 85-129 and 36-280 models are used.
- Sundstrand APS 2000 system controls and indicates APU operation.
- APU mounted on accessory drive pad.
- 60 KVA ground power, 50 KVA flight operation.
- Supplies bleed air for air conditioning (and engine startup), optimizing takeoff.
APU Starting
- APU starts with airplane battery or external DC power.
- Automatic shutdown happens with overspeed, high oil temperature, low oil pressure, or fire.
Exhaust Noise Reduction
- Noise reduced by acoustically treated inlet and exhaust ducts, and distance from cabin and ground service points.
APU Access and Maintenance
- APU readily accessible for inspection, maintenance, or removal through large fuselage access door.
Garrett 85-129 Components
- Two-stage centrifugal compressor with one radical inflow turbine.
- Accessories grouped at the front.
Garrett 36-280 Components
- Two centrifugal impellers and a single centrifugal turbine with a containment ring.
Fire Protection System
- APU housed in a fire protection shroud to contain fires.
- Fault causes "DET INOP" light and master warning lights activation.
Controls & Indicators
- Panel located on the forward head panel
- Includes APU switch (on/off/start positions, cooldown option)
- Maintenance light illuminates when oil tank is low.
- Provides indicators on the APU fire system
- Includes lights to warn of non-critical and critical failures.
- Oil low pressure
- Overspeed condition
- Critical part failure.
- Contains AC ammeter to display current.
- Provides exhaust gas temperature indicator
APU Fire Protection Controls
- Illuminated red light = APU fire.
- Fire warning horn when fire detected.
- APU fire control handle activates system
- Bottle discharge switch triggers fire suppression.
Pneumatics
- APU pressurizes air for engine starting
- Air source obtained from onboard APU or external ground cart.
- Uses 5th stage compressor air section for flight, and 9th stage for low-engine.
- Precooler system to control air temperature.
- APU used for air conditioning up to 17,000 ft altitude
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