APU Flashcards
What does the APU supply bleed air to?
Air conditioning pack and De ice system
Which bus does the APU supply power to?
28v right main feeder bus
What unit provides automatic control of the start sequencing, running and other aspects of the APU operation?
The ESU (Electronic sequence unit (
What power source can be used to start the APU?
main 28 V main bus or external power.
Where is fuel for the APU supplied from?
Left fuel tank collector Bay.
What unit allows automatic start sequencing and shut off in case of a malfunction?
The ESU
What are some faults that will cause the ESU to shut down the APU?
High EGT,
high oil Temp
low oil pressure
gas generator over or underspeed
How many loops and extinguishera are in the APU fire detection system?
1loop and 1 extinguisher.
When will the fault light illuminate in the APU panel?
Provides a visual indication of fire extinguishing or fire detection malfunctions (extinguisher pressure low or fault in the detector loop).
What cautions /warnings will alert crew to an APU fire? When will the bottle automatically be discharged?
APU caution,
Check fire det warning
The fire warning light on the APU fire protection panel
The bottle light will also illuminate to confirm the fire bottle is charged and armed. The fuel valve closed light will also illuminate. 15 seconds later the fire extinguisher will be discharged and the bottle light will go out (fire light should go out too).
What must be on to allow APU automatic fire protection?
The battery master as the circuits are powered by the essential bus.
