Study Guide APU Flashcards
Describe the APU
Constant speed
Single stage impeller with a two stage axial flow turbine
What controls the APU
A dedicated FADEC.
What battery is used for APU start?
Batt two for start and bat two for the FADEC and EICAS monitoring.
What is the fuel source for the APU?
Left tank and the right tank using cross feed.
What fuel pump is used for the APU?
Right DC without AC power.
Right AC pump when AC power is on.
Motive flow pump with the right engine running.
Will APU shutdown automatically if speed and acceleration rate are not reached in starting cycle in time?
Yes
What does moving the APU start switch to off do?
Initiates normal APU shut down.
One minute cool down.
Provides electrics if no other AC power source is available.
Can an APU shutdown be canceled?
Yes, by turning the soot start button back to on during the one minute cool down period.
How does the spy shut down immediately?
Push EMER stop button…. No cool down period.
What will happen if batteries are shut off during the cool down period?
Shuts down instantly.
When will automatic shut down of the APU occur?
On the ground if… Over speed, under speed, FADEC critical fault, fire, overheat, low oil pressure.
In flight….. Over speed, under speed, FADEC critical fault.
Can APU be started after a critical fault?
No
What kind of APU?
Sunstrand APS 2300
