APU Flashcards
What happens when the APU master button is selected ON?
The APU fuel shutoff valve opens and the ECU is energized.
When does the APU indicate “READY TO LOAD”?
When the RPM has reached 94.5% + 3 to 5 seconds.
What will cause the APU automatic shutdown sequence to occur while on the ground?
Overspeed, overcurrent, overtemp (EGT), low oil pressure, high oil temperature, loss of EGT or RPM signals, and loss of power to the DC BUS 2.
What will cause the APU automatic shutdown sequence to occur in-flight?
Overspeed
During an APU shutdown, don’t turn off the APU MASTER until the RPM is below __%
10%
Must the APU be monitored in flight?
Yes
Must the APU be monitored on the ground?
No
Is it permissible to operate the APU in its amber EGT region?
Yes, but for emergency use only
Must you monitor the start and shutdown of the APU?
Yes
How should the APU be shutdown?
From the loaded condition
Is it required to shut the APU down for airplane de-icing
Yes and must remain off for subsequent taxi and takeoff.
When is it not permitted to use the APU bleed for ECS operation on the ground?
With one or both engines running, except as necessary for takeoff
What is the maximum altitude for APU operation?
30,000 ft
What is the maximum altitude for main engine airstart with APU assistance?
30,000 ft
What is the maximum altitude for APU restart in flight?
20,000 ft
What are the APU starter limitations?
3 consecutive starts or start attempts with 1 min 30 second max combined starter running time, which must be followed by 10 minutes off.
How long after an APU shutdown may the APU be restarted?
2 minutes after the APU MASTER selected off
Can the APU be restarted following an automatic shutdown without a failure message indicated?
Yes, but only once. If the restart is unsucessful, no further restart attempts are allowed.
Can the APU be restarted following an automatic shutdown with an amber failure message displayed?
No
Can the APU be restarted following a manual shutdown due to a hot start?
No
What is the maximum continuous load of the APU starter/generator?
400 Amps
Wait at least __ minute(s) for APU stabilization before APU bleed ON
One minute
If the APU bleed is used during takeoff, when should the switch back to engine bleeds be accomplished?
After passing acceleration height, but no higher than 1,500 above airport elevation.
Wait ___ minute(s) after the APU MASTER button is selected off before attempting a restart of the APU.
Two
