APU Flashcards
What are the start sources for the APU, and which one do we normally use?
TR/ APU battery. APU Battery
Can the APU be operated in flight?
Yes up to 20,000’
Is electrical power available from the APU in flight?
How about APU bleed air in flight?
No
Bleed for one pack to 15,000’
What APU components are powered by the APU battery?
Inlet door
APU controller
DC fuel pump
APU fire detection
What APU components are powered by the main battery?
APU fire extinguisher
APU fuel valve
SBY power for APU controller.
What powers the APU starter during a battery start sequence?
APU battery.
What happens if the TR should overheat with the start source in TR?
Starting power is transferred to the APU battery and the start continues on battery power. Further start attempts with an overheated TR are inhibited.
How does a TR failure affect APU starting?
No automatic switching to APU battery, manually change the source.
When does the EICAS memo message APU RUNNING display?
APU selector on
APU N1 >95%
Describe the APU shutdown sequence.
Rotating APU selector off begins the shutdown cycle by closing the APU bleed air valve. The APU continues to run unloaded for 60’ cooldown period. When the cooldown period finished the APU shuts down.
What would happen if the battery switch is positioned OFF prior to completion of the APU shutdown cooldown period?
The APU will shut down immediately.
How long should you wait before turning the battery switch OFF after the APU selector is rotated to OFF, and why?
Two minutes to ensure a complete shutdown sequence with fire detection capability.
What would cause the APU to shut down automatically?
If a limit is exceeded or a fire detected
