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

Question 9

What are a few reasons the APU will shut down on the ground?

Answer 9

• Overspeed
• Underspeed
• FADEC critical fault
• APU Fire
• APU EGT overtemperature
• APU high oil temperature
• APU low oil pressure
• Sensor fail

Question 10

When will automatic shutdown of the APU occur in flight?

Answer 10

• Overspeed
• Underspeed
• FADEC Critical Fault

Question 11

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

Answer 11

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