APU

Question 1

What services does the APU provide and what

are they used for?

Answer 1

An electrical generator supplies 28V DC 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 three consecutive unsuccessful start
attempts are allowed, with 30 second 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, APU
starter not disengaged, APU fuel SOV failure
(AOM 9-04-50)