APU Flashcards
What is the APU used for?
Electric and bleed air
What monitors and controls the APU?
FADEC
How are batteries used for APU start?
BATT 2 powers the APU START BUS.
BATT 1 powers the FADEC and EICAS for monitoring.
What is the fuel source for the APU?
- Right fuel tank
- Left fuel tank through crossfeed valve
What fuel pump is used for APU start with just batteries?
With AC power?
With right engine running?
- Batteries on only: DC fuel pump
- AC powered aircraft: Right AC pump
- Right engine running: Ejector fuel pump
When does the APU electrical and pneumatic loading become available?
- APU icon is available on the ELEC synoptic page.
- 3 seconds after APU reaches 95% RPM
What will happen if the APU fails to start within the normal start cycle time period?
APU will shut down.
What does moving the APU selector knob to OFF do (4)?
- Initiates normal APU shutdown.
- 1 minute cooldown followed by a spooldown period.
- Pneumatics removed immediately and electric removed after one minute cooldown.
Can the APU electrical power be used during the cooldown period?
Yes
If you need the APU 50 seconds into shutdown, is there a way to get its use back?
Yes, just turn the APU master switch back to ON.
Can the APU pneumatics be used during the cooldown period?
No
Can the APU shutdown be cancelled?
Yes, by moving the MASTER switch back to ON before the one minute cooldown is over.
How can the APU be shut down immediately?
- APU EMER STOP button.
- No one minute cool down period.
When will automatic shutdown of the APU occur (in flight)?
Flight:
- Overspeed
- Underspeed
- FADEC critical fault
When do we get the red bar on the APU EMER STOP button?
An APU fire is detected
What happens when the APU EMER STOP button is pushed?
The APU fuel shutoff valve closes and the APU will shut down with no cooling period. A white stripe illuminates on the button.
What is the maximum altitude for operation of the APU bleed?
15,000
What is the maximum altitude for APU operation?
FL330
What is the maximum altitude for APU start?
FL300
What is the maximum altitude for APU to assist with engine start?
FL210
Why could APU use on the ground lead to a fuel imbalance?
APU draws from the right tank.
The APU is equipped with a dedicated FADEC (T/F).
True
During the normal shutdown sequence, APU bleed air is immediately removed and electrical power is removed after a one minute cooldown period, followed by a one minute spooldown period (T/F).
True
Is battery 1 necessary to start the APU?
Yes, BATT 1 powers the APU FADEC
How many batteries are required for normal APU start?
2
Which fuel pump is used for APU start with only batteries ON?
DC Pump
Which fuel pump is used for APU start with an AC power source?
AC Pump 2
Which fuel pump is used for APU start with the right engine running?
Right ejector pump
How can the APU be shut down immediately?
Push the guarded EMER STOP Button IN
What conditions will cause the APU to automatically shut down on the ground?
Underspeed
FADEC Critical Fault
Overspeed
Sensor fail High oil temperature EGT overtemp Low oil pressure Fire
