APU Flashcards
Can the APU be started in flight?
NO
What is the max operation altitude of the APU?
20,000’
Where is the APU operating status displayed?
EICAS STATUS page
What does an yellow “APU” EICAS message indicate?
Auto shutdown of the APU with selector ON or APU N1 exceeds 95% with selector OFF
What does a yellow “APU DOOR” EICAS message indicate?
APU door not in commanded position
What does a yellow “APU FUEL” message indicate?
Low pump pressure when pump is active or APU fuel valve not in commanded position
When is APU electrical power availble?
On the ground ONLY
What is the APU bleed air capable of?
All a/c packs on the ground, 1 pack up to 15,000’.
How does the APU get fuel?
From Main tank 2, main AC pump 2 aft supplies pressure. On ERF(Extended Range Freighter) and newer aircraft, main AC pump 3 aft fuel transfer and can provide fuel pressure if main AC pump 2 aft fails.
How does the APU get fuel if AC power is not available?
Dedicated DC pump in main tank 2.
Where is the exterior APU panel located?
Right Body Gear Wheel well.
What happens when an APU fire is detected?
APU will be automatically shut down. Including a APU fire light and wheel well horn will sound.
What provide APU fire extinguishing?
1 Extinguishing bottle.
What does the APU battery power?
DC Electrical starter.
When APU starter is not engaged:
APU Air inlet Door
APU Controller
DC Fuel Pump
APU Fire detection system
What does the Main Battery Power on the APU?
APU fire extinguisher
APU fuel valve
Standby power for the APU controller. When the APU starter is engaged, all other APU components are powered by the main battery.
Starter Cycle Limits
see graphic
APU Selector “OFF” position
Closes the APU bleed air valve, initiates the normal shutdown, and resets the auto shutdown fault logic. 60 second cool down.
APU Selector “ON” position
Opens the APU fuel valve and inlet door, arms the APU bleed air isolation valve, and activates the DC fuel pump or two AC fuel pumps — as appropriate.
APU Selector “START” position
APU fuel valve and air inlet door open. As soon as the air inlet door is fully open, the starter engages. At the appropriate time, the ignition and light-off occur and the RPM accelerates to the rated speed.
What message is displayed if the APU is operating normally?
White “APU RUNNING” in EICAS.
What is the proper complete shutdown sequence?
Waiting a full 2 minutes after the APU is placed to the OFF position.
The EICAS Memo message APU RUNNING displays when the APU RMP is above _____% N1.
95
