APU

Question 1

Pushing APU Emerg stop button

Answer 1

• closes APU fuel shutoff valve

- shuts down APU without cooling period

Question 2

Normal fuel supply for APU

Answer 2

Right wing tank via:

• DC Pump when only DC power is avail
• AC Pump when AC power is avail and engine not running
• ejector fuel pump when engine is running

Question 3

APU altitude limits

Answer 3

– Electrical AC power up to 33000 ft.
– Bleed air for engine starting up to 21000 ft.
– Bleed air for air conditioning and pressurization up to 15000 ft.
*Maximum altitude for APU start is 30000 ft.

Question 4

Normal APU Shutdown sequence

Answer 4

• rotate APU selector know to OFF
• APU pneumatic power removed immediately
• 1 or 2 minute cooldown period after which electrical power is removed

*EICAS message APU SHUTTING DOWN

Question 5

Auto APU Shutdown on the ground

Answer 5

• APU Fire
• EGT overtemperature
• High oil pressure
• Low oil pressure
• Sensor fail

Question 6

Auto Shutdown of APU in flight

Answer 6

• Overspeed
• underspend
• FADEC fault