APU Flashcards
When AC power is available, the fuel is supplied to the APU by which fuel pump?
Aft main pump 2 and aft main pump 3 operating to prevent fuel transfer
On the -400, to what altitude is APU bleed air available in flight for one pack?
15,000
On the -400, rotating the APU selector to OFF begins the shutdown cycle by closing the APU bleed air valve. How long does the APU continue running unloaded for the cool down period?
60 seconds
For an APU battery start, prior to the start sequence, the APU battery powers which APU components?
APU starter, inlet door, controller, DC fuel pump, APU fire detection
If the APU is running, what occurs if the APU selector is rotated to the OFF position?
The APU continues running unloaded for a 60 second cool down period.
What does the EICAS memo message “APU RUNNING” indicate?
APU selector is ON and APU N1 RPM exceeds 95%
What condition is indicated by the EICAS advisory message APU?
Automatic shutdown of APU with APU selector ON or APU N1 RPM exceeds 95% with APU selector OFF.
During the APU battery start sequence, the APU battery powers which components?
APU starter only
APU selector to the OFF position resets auto shutdown fault logic except when the shutdown is due to what condition?
APU bleed duct leak
What is the maximum altitude the APU may be operated in flight?
20,000 ft
If the battery switch is positioned to OFF while the APU is running what would occur to the APU?
APU shuts down immediately
The APU:
If started on the ground can provide pneumatics for one pack up to 15,000’, operate unloaded to 20,000’, and cannot be started inflight
To maintain fire detections, how long after the APU selector is rotated to OFF should the crew wait until placing the battery switch OFF
2 minutes
APU bleed air is available in flight under what conditions?
One pack up to 15,000 ft
After moving the APU selector to OFF
Wait 2 minutes before turning the battery switch OFF to ensure fire detection
