APU Flashcards
APU starting limits on battery
3 consecutive start attempts, followed by 1 hour cool down
APU starting limits on external DC
3 start attempts, 15 min cool down between each attempt
Max APU operating altitude
45000ft
APU generator electrical load limit
100% (40KVA) sea level to 45,000 ft
How is an APU start manually aborted?
Depress the APU stop switch, which triggers the 108% over speed circuit, resulting in an immediate start abort
The min temp required for APU start is?
Greater than -30°c
The min acceptable battery volts prior to APU start is?
22 VDC
When is the APU air load control valve automatically inhibited OFF/how long?
During APU start, and after APU start for 90 sec
How is it determined that all parameters are acceptable for APU start?
The APU READY light will be illuminated
Will the APU start be inhibited with the absence of the ready light?
No, however the APU air inlet door must be verified to be open prior to start
Describe a normal APU shut down on the ground and inflight
A cool down period is initiated, loads are shed within 2 sec APU RPM decreases 1/2% for 60 sec
Why is there a requirement to turn OFF the right battery for an inflight APU start with one or both main generators powered?
Because both batteries combined with their chargers produce too much amperage and may ramp the APU starter past APU starter envelope
Is the APU electronic control unit still powered after the APU master switch is deselected?
Yes for 5 min
Can the APU provide pressurization in flight?
No
What is the max altitude for APU operation to start?
39000
If the APU was started on the ground, what mode will it be in flight?
Essential mode
If landing with the APU running. How long will it stay in essential mode?
15 min
The APU receives its fuel from what source?
The motive flow from the left fuel ejector
Selecting what switch to the OFF position will close the APU fuel shut off valve immediately
The APU master switch
Prior to starting the APU, how can the position of the right engine lower cowl door be checked?
Visually or checking the DOORS 2/3 synoptic display, or the amber cowl light on the apu control panel
If necessary, how can the batteries be warmed prior to APU start?
Use an external AC power cart to charge and warm the batteries
After APU start, when will the APU generator automatically power the electrical buses
2 sec after the APU achieves 99% RPM
Would an APU FIRE CAS cause the APU to shutdown in-flight or on the ground?
Both on the ground and inflight
At approximately what point will the APU ECU close the inlet door when the STOP switch is used to shutdown the APU
40% RPM
At what point will the APU ECU close the inlet door when the MASTER switch is used to shut down the APU.
It will close the inlet door immediately
If the APU continues to run in flight even though a fault has been detected that would normally cause it to shutdown on the ground, would the crew be aware?
Yes, by illuminating the amber APU ESSENTIAL CAS message
