APU Flashcards
Primary function of the APU
AC power via 30 KVA generator
What controls and monitors the APU
The ECU
How is flow of air controlled through the compressor
Variable Geometry Diffuser
What is the job of the VGD
prevents surges and stalls
What accessories mounted on the APU gearbox
- AC Generator
- Fuel Control Unit
- Oil pumps
- Oil cooling fan
- DC starter motor
What is the screened duct for on the left side of the fuselage
Air is drawn in by the oil cooler fan for oil cooling and ventilation of the APU enclosure
How many pounds per hour does the APU burn
120 with electrical and bleed air loading
What controls fuel supply to the APU
The SOV
When does the APU SOV close
- APU PWR FUEL switch
- APU FIRE PUSH switch
- Automatically when fire is detected
What happens when the APU PWR switch is pressed
DIGS
- APU IN BITE self test (5sec)
- RPM EGT Gauges displayed
- Intake door opens
- APU SOV OPEN status message
- XFLOW/APU pump starts
When is starter motor de energized (START light goes out)
50% rpm
What does green AVAIL light indicate
APU is ready for bleed air loading, happens at after 4 seconds after RPM reaches 99%
Which battery is used for APU start
Main and the APU Battery
APU battery turns the APU Starter
Main Battery operates the ECU
What conditions will the APU shut down in flight
- Fire
- Slow Start
- Overspeed
- DC power loss
- RPM signal loss
- ECU Failure
What switch allows bleed air to be supplied to the 10th stage bleed air manifold
APU LCV on the Bleed Air Panel