APU

Question 1

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

Answer 1

An electrical generator supplies 28VDC to the electrical system.

The pneumatic power is used for engine starting and to supply bleed air to the air conditioning pack of the Environmental Control System (ECS)

(AOM 9-04-01)

Question 2

How is the APU controlled and monitored?

Answer 2

Through a dedicated Full Authority Digital Engine Control (FADEC)

(AOM 9-04-01)

Question 3

What does pressing the APU ON/OFF button do?

Answer 3

It starts the ECU power-up sequence and initiates the APU Built-In Test (BIT)

(AOM 9-04-30)

Question 4

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

Answer 4

During the ECU BIT test

(AOM 9-04-30)

Question 5

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

Answer 5

The APU is available to start
(AOM 9-04-30)

Question 6

If the START button on the APU control panel illuminates amber, what does that indicate?

Answer 6

The APU start is inhibited (AOM 9-04-30)

Question 7

What are the APU starter limitations?

Answer 7

Up to 3 consecutive unsuccessful start attempts are allowed.
30s intervals
between attempts.

(AOM 2-38)

Question 8

What MFD page can APU information be seen on?

Answer 8

The STATUS synoptic page
(AOM 9-04-30)

Question 9

Which tank normally supplies fuel to the APU?

Answer 9

The right tank
(AOM 9-04-50)

Question 10

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

Answer 10

Yes, via the cross-feed system
(AOM 9-04-50)

Question 11

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

Answer 11

Yes
(AOM 9-04-50)

Question 12

On the ground, what is the primary source of pneumatic air?

Answer 12

The APU
(AOM 9-04-50)

Question 13

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

Answer 13

All the airplane electrical loads and charge both batteries
(AOM 9-04-50)

Question 14

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

Answer 14

All electrical loads (except for the SHED BUSES) and also charging both batteries
(AOM 9-04-50)

Question 15

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

Answer 15

Up to 31,000 ft
(AOM 9-04-50 & AOM 2-38)

Question 16

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

Answer 16

Up to 23,000 ft
(AOM 9-04-50 & AOM 2-38)

Question 17

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

Answer 17

Up to 20,000 ft
(AOM 9-04-50 & AOM 2-38)

Question 18

Where does the APU get it’s power for starting?

Answer 18

The #2 BATT
(AOM 9-04-50)

Question 19

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

Answer 19

A green “OK”
(AOM 3-01-10)

Question 20

List the 4 conditions that will cause the APU to automatically shut down either in flight or on the ground:

Answer 20

Overspeed
Underspeed
ECU Internal failure
APU Bleed leak

(AOM 9-04-50)

Question 21

List the conditions that will cause the APU to automatically shut down on the ground only:

Answer 21

APU Fire,
APU EGT over temperature,
APU high
oil temperature,
APU low oil pressure,
APUstarter not disengaged,
APU fuel SOV failure

(AOM 9-04-50)