APU Flashcards
If more than 1000 lb of fuel have been loaded in the center tank and you need to run the apu, which fuel pump should you turn on so you dont get an imbalance prior to takeoff?
Left center
If no fuel have been loaded in the center tank and you need to run the apu, which fuel pump should you turn on?
Left forward fuel pump
Run the APU for how many minute before using it bleed air source?
2 minutes
If APU MAINT Light is illuminated, what should you do?
If APU MAINT Light is illuminated, only operate the APU if
needed. Make AML entry.
How many minutes should you wait after apu shutdown and apu gen bus off light extinguishes before turning the battery switch off?
2 or 3 minutes depending on aircraft
What happens to the apu if you turn off the battery?
Apu shuts down
What control module controls apu operation?
ECU - Electronic Control Unit
Where does the apu get fuel from?
Left fuel manifold
With no power on the airplane, how does fuel get to the apu for the initial start?
Suction feeds from the left fuel tank
Does the apu have auto shutdown features?
Yes
On the ground, what all does the apu auto shutdown for?
EGT exceedance High oil temprature Low oil pressure Failure to start Failure to accelerate APU fire
The APU door has how many positions?
3
Closed
Open ground
Open air
What happens if you turn the battery switch off while the apu is running?
Apu shuts down
Where do we get electrical power to start the apu if AC power is not available?
Airplane battery
Where do we get electrical power to start the apu if AC power is available?
No 1 Transfer bus
What powers the apu ECU?
Aircraft battery
What is the load shedding priority for the apu if both air and electrics are being drawn from the apu?
Other than during engine starts, apu will unload bleed air demand
On the ground, What is the load shedding priority for the apu if only electrics are being drawn from the apu and EGT or speed goes over acceptable limits or if there is an over draw of power?
Apu sheds some buses. Galley busses and main busses will be shed. You can reset them.
Is there a DC fuel pump in the left fuel that helps the apu suction fuel on initial start if AC power is not available?
Its an option and unsure if AA has those installed on the aircraft
How long is the apu automatic cooldown time once you place the switch to off?
1 minute
Will the apu conduct the automatic 1 minute cooldown time if you shutdown the apu by pulling the apu fire handle?
No. Its an immediate shutdown.
What manufacturer makes the Apu on the NG and Max?
Allied signal which became Honeywell
Since the honeywell apu has a starter generator, it can be started with battery power or AC transfer bus 1 while the classics were battery start only. True or False?
True
Is there an Apu Egt gauge on the max?
No. Its removed because the apu is highly automated using the FADEC on the APU.
Can you continue to operate the APU if you see a maintenance light?
Yes. But you should put it in the logbook and let maintenance make a decision.
Does the MAX have a blue apu maintenance light?
No. It is replaced by the door light.
What will call the APU to auto shutdown?
Fire
Low oil pressure
Overspeed
High oil temperature / Fault
How does the apu shutdown when you place the switch to off?
It sends an overspeed signal to itself which causes it to shutdown.
The apu can power both ac transfer buses both on the ground or in flight. True or false?
True
Will switching the battery off weather in the ground or air cause the apu to shutdown?
Yes. The classics, it did not shut it down in the air.
What is the primary source of power for starting the apu?
AC transfer bus 1. If its not available then the main battery is used. There is an auxiliary battery option available on the NG,s which can be used to start the apu.
When does the ECU remove the start signal during an apu start?
At 70% speed
The air that comes thru the apu air inlet is used for what purposes?
Provide combustion air as well as apu generator and oil cooling
What is the purpose of the vortex generator in front of the apu air inlet?
Provides for better air flow into the inlet. There is also a flap that bends 25 degrees inward while the apu is running to better form airflow
Is there an eductor air inlet on the max?
No. It is integrated into the apu door.
What are the 3 apu door positions on the max?
Closed - 0 degrees
Flight open - 17 degrees
Ground open - 45 degrees
Apu fire detection is by the battery bus or the hot battery bus?
Battery bus
Apu fire protection is by the battery bus or the hot battery bus?
Hot battery bus
Where is the apu fire bottle located?
The horizontal stabilizer assembly compartment in the tail of the a/c
