APU Flashcards
Describe the APU
Constant speed
Single-stage impeller with a 2-stage axial-flow turbine
Independent oil system
What controls the APU?
A dedicated FADEC
What battery is used for the APU start?
BATT 2 powers the starter
BATT 1 powers the FADEC and EICAS for monitoring
What is the fuel source for the APU?
Right fuel tank
Left fuel tank through the crossfeed valve
What fuel pump is used for APU start?
Batteries ON: only DC fuel pump in right tank
AC powered airplane: ACMP 2
Right engine running: ejector fuel pump
Will the APU shutdown automatically if speed and acceleration rate isn’t reached in the starting cycle time?
Yes
What does moving the APU start switch to OFF do?
Initiates normal APU shutdown 1-minute cool down No pneumatics (electrics only for 1 minutes)
Can the APU shutdown be canceled?
Yes, by moving the START switch back to ON before the 1-minute cool down is over.
How is the APU shutdown immediately?
APU emergency stop button
No 1-minute cool down period
What will happen if batteries are turned OFF during the 1-minute cool-down period?
APU will shut down immediately
When will automatic shutdown of the APU occur on the ground?
Overspeed Underspeed FADEC critical fault Fire (but won't blow the bottle) EGT Overtemp Low oil pressure High Oil Temp
When will automatic shutdown of the APU occur in flight?
Overspeed
Underspeed
FADEC critical fault
Can the APU be started after a critical fault?
No
What kind of APU is on the aircraft?
Sundstrand APS 2300
When is APU electrical power available?
95% +3 seconds
