APU

Question 1

What services does the APU provide and what are they used for?

Answer 1

28 V DC to the electrical system
Pneumatic air for engine start and air conditioning.

Question 2

How is the APU controlled and monitored?

Answer 2

FADEC

Question 3

What does pressing the APU ON/OFF button do?

Answer 3

Starts the ECU power-up sequence.
Normal APU shutdown.

Question 4

When does the START button on the APU CONTROL panel flash green?

Answer 4

During the ECU BIT.

Question 5

What does the START button on the APU control panel illuminating steady green indicate?

Answer 5

APU is ready to start.

Question 6

If the START button illuminates amber, what does that indicate?

Answer 6

APU start is inhibited.

Question 7

What are the APU starter limitations?

Answer 7

Up to three consecutive start attempts allowed with 30 second intervals between attempts.

Question 8

What MFD page can APU information be seen on?

Answer 8

The STATUS synoptic page.

Question 9

Which tank normally supplies fuel to the APU?

Answer 9

Right tank.

Question 10

Is it possible to feed the APU from the left wing tank? If so how?

Answer 10

Yes through the cross-feed valve.

Question 11

Can the APU supply bleed air on the ground or in flight?

Answer 11

Yes, both.

Question 12

If the APU is the only source of electrical power on the ground, what buses can the APU power?

Answer 12

All plus battery charging.

Question 13

What is the APU operating envelope for starting, operation and to supply electrical power?

Answer 13

Up to 31,000 feet.

Question 14

Up to what altitude is the APU able to supply bleed air for engine start?

Answer 14

Up to 23,000 ft.

Question 15

Where does the APU get its power for starting?

Answer 15

Bat 2.

Question 16

What should be displayed on the STATUS synoptic page if the APU oil quantity is sufficient? Is low?

Answer 16

A green “OK”
A amber “LO QTY”

Question 17

List four conditions that will cause the APU to automatically shut down either inflight or on the ground.

Answer 17

Overspeed
Underspeed
ECU failure
APU bleed leak

Question 18

List the conditions that will cause the APU to automatically shutdown on the ground only.

Answer 18

APU fire
EGT over temperature
High oil temperature
Low oil pressure
Starter not engaged
Fuel shutoff valve failure

Question 19

If the APU is the only source of electrical power in flight, what buses can the APU power?

Answer 19

All except the shed busses.