APU

Question 1

What is the APU used for?

Answer 1

Electric and bleed air

Question 2

What monitors and controls the APU?

Answer 2

FADEC

Question 3

How are batteries used for APU start?

Answer 3

BATT 2 powers the APU START BUS.

BATT 1 powers the FADEC and EICAS for monitoring.

Question 4

What is the fuel source for the APU?

Answer 4

• Right fuel tank

- Left fuel tank through crossfeed valve

Question 5

What fuel pump is used for APU start with just batteries?
With AC power?
With right engine running?

Answer 5

• Batteries on only: DC fuel pump
• AC powered aircraft: Right AC pump
• Right engine running: Ejector fuel pump

Question 6

When does the APU electrical and pneumatic loading become available?

Answer 6

• APU icon is available on the ELEC synoptic page.

- 3 seconds after APU reaches 95% RPM

Question 7

What will happen if the APU fails to start within the normal start cycle time period?

Answer 7

APU will shut down.

Question 8

What does moving the APU selector knob to OFF do (4)?

Answer 8

• Initiates normal APU shutdown.
• 1 minute cooldown followed by a spooldown period.
• Pneumatics removed immediately and electric removed after one minute cooldown.

Question 9

Can the APU electrical power be used during the cooldown period?

Answer 9

Yes

Question 10

If you need the APU 50 seconds into shutdown, is there a way to get its use back?

Answer 10

Yes, just turn the APU master switch back to ON.

Question 11

Can the APU pneumatics be used during the cooldown period?

Answer 11

No

Question 12

Can the APU shutdown be cancelled?

Answer 12

Yes, by moving the MASTER switch back to ON before the one minute cooldown is over.

Question 13

How can the APU be shut down immediately?

Answer 13

• APU EMER STOP button.

- No one minute cool down period.

Question 14

When will automatic shutdown of the APU occur (in flight)?

Answer 14

Flight:

• Overspeed
• Underspeed
• FADEC critical fault

Question 15

When do we get the red bar on the APU EMER STOP button?

Answer 15

An APU fire is detected

Question 16

What happens when the APU EMER STOP button is pushed?

Answer 16

The APU fuel shutoff valve closes and the APU will shut down with no cooling period. A white stripe illuminates on the button.

Question 17

What is the maximum altitude for operation of the APU bleed?

Answer 17

15,000

Question 18

What is the maximum altitude for APU operation?

Answer 18

FL330

Question 19

What is the maximum altitude for APU start?

Answer 19

FL300

Question 20

What is the maximum altitude for APU to assist with engine start?

Answer 20

FL210

Question 21

Why could APU use on the ground lead to a fuel imbalance?

Answer 21

APU draws from the right tank.

Question 22

The APU is equipped with a dedicated FADEC (T/F).

Answer 22

True

Question 23

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).

Answer 23

True

Question 24

Is battery 1 necessary to start the APU?

Answer 24

Yes, BATT 1 powers the APU FADEC

Question 25

How many batteries are required for normal APU start?

Answer 25

2

Question 26

Which fuel pump is used for APU start with only batteries ON?

Answer 26

DC Pump

Question 27

Which fuel pump is used for APU start with an AC power source?

Answer 27

AC Pump 2

Question 28

Which fuel pump is used for APU start with the right engine running?

Answer 28

Right ejector pump

Question 29

How can the APU be shut down immediately?

Answer 29

Push the guarded EMER STOP Button IN

Question 30

What conditions will cause the APU to automatically shut down on the ground?

Answer 30

Underspeed
FADEC Critical Fault
Overspeed

Sensor fail
High oil temperature
EGT overtemp
Low oil pressure
Fire