APU

Question 1

How is the APU controlled?

Answer 1

• Via a dedicated FADEC.

Question 2

What Battery is used for the APU Ground Start?

Answer 2

• BATT 2 powers the starter.

- BATT 1 powers the FADEC and EICAS for monitoring.

Question 3

Where does the APU get its fuel?

Answer 3

• Right Fuel Tank.

- Left Fuel Tank (through the Crossfeed valve)

Question 4

What Fuel Pumps are capable of providing fuel to the APU?

Answer 4

• Batteries ‘ON’ only = DC Fuel Pump in Right Tank
• AC powered airplane = ACMP 2
• Right engine running = RH Ejector Fuel Pump

Question 5

What does moving the APU start switch to ‘OFF’ do?

Answer 5

• Initiates Normal APU Shutdown
• Closes APU Bleed Valve
• 1-minute cool down

Question 6

Can a normal APU shutdown be canceled?

Answer 6

• Yes, by moving the START switch back to ‘ON’ before the 1-minute cool
  down is over.

Question 7

How can you shutdown the APU immediately?

Answer 7

• APU Emergency Stop button (no 1-minute cool down period)

Question 8

What will happen if the Batteries are turned OFF during the 1-minute cool-down
period?

Answer 8

- APU will shut down immediately
What are a few reasons the APU will shut down on the ground?
- Overspeed
- Underspeed
- FADEC critical fault
- APU Fire
- APU EGT overtemperature
- APU high oil temperature
- APU low oil pressure
- Sensor fail

Question 9

When will automatic shutdown of the APU occur in flight?

Answer 9

• Overspeed
• Underspeed
• FADEC Critical Fault

Question 10

What happens when you turn the APU Start Knob to ON?

Answer 10

• Powers the APU FADEC
• Displays viable APU EICAS information following FADEC self-test
• Opens the APU Fuel Shutoff Valve

Question 11

When is electrical and pneumatic loading available during APU start?

Answer 11

• 95% RPM plus 3 seconds