APU Flashcards
What would happen if APU air is selected on immediately after APU start?
The APU air would come on 60 seconds later
Will the APU start if the READY light is not on?
Yes
To what altitude will the APU operate?
45,000 feet
Normal APU shutdown is accomplished by pushing what switch?
APU stop switch
Selecting what APU switch to the OFF position will close the APU fuel shutoff valve immediately?
APU Master
Prior to starting the APU, how can the position of the right engine lower cowl door be checked?
Visually or using the “DOORS” 2/3 synoptic display
What is the minimum fuel temperature required prior to APU start?
Above -30 C
If necessary, how can the batteries be warmed most effectively prior to APU start?
Use an external AC power cart to charge and warm the batteries
What is the minimum acceptable battery voltage prior to APU start?
22 VDC
When is the APU air load control valve automatically inhibited OFF?
During APU start, and 60 seconds after start
How is it determined that all parameters are acceptable for APU start?
The APU READY light will be on
Will the APU start be inhibited with the absence of the READY light?
No, but the APU air inlet door must be verified to be open prior to start
After APU start, when will the APU generator automatically power the electrical buses?
After achieving 99% RPM for 2 seconds
How is an APU start manually aborted?
Depress the APU STOP switch, which triggers the 106% overspeed circuit, resulting in an immediate start abort
How is the APU normally shut down?
Using the APU STOP switch on the APU panel
How long are the APU RPM and EGT indications displayed after shutting down the APU?
5 minutes after APU RPM is less than 5%, and the APU MASTER is selected OFF, provided the APU ECU has a source of power
What are the limitations for starting the APU with external DC power?
3 start attempts, 15 minutes in between each attempt
Would an APU FIRE message cause the APU to shutdown in flight or on the ground?
Both
Describe a normal APU shutdown
Once STOP is pressed, APU RPM decreases by 0.5% per second, then at 70% RPM the APU shuts down
At approximately what point will the APU ECU close the inlet door when the STOP switch is used to shut down the APU?
35% RPM
At what point with the APU ECU close the inlet door when the MASTER switch is used to shut down the APU?
It will motor closed based on APU RPM
Why is there a requirement to turn off the right battery for an in flight APU start with one or both main generators powered?
Both batteries combined with their chargers produce too much amperage and may ramp the APU starter past the APU start envelope
Is the APU ECU still powered after the APU MASTER switch is deselcted?
Yes, for 5 minutes
What is the voltage rating for the APU generator, and is it interchangeable with the main generators?
40 kVA, not interchangeable
