APU

Question 1

What is the approximate fuel consumption for the APU with
a) 2 Packs ON
b) 1 Pack OFF
c) 2 Packs OFF

Answer 1

a) 130 kg/h
b) 110 kg/h
c) 100 kg/h

Question 2

How much fuel can be saved by using ground power and a pneumatic ground unit?

Answer 2

130 kg/h

Question 3

How much CO2 emissions can be saved in kg/h by using ground pneumatic and ground power units?

Answer 3

410 kg/h

Question 4

How is fuel fed to the APU?

Answer 4

From the left feed line.
If pumps are off a separate APU FUEL PUMP starts automatically

Question 5

Describe the manual shut down sequence for the APU

Answer 5

• Push the MASTER SW pb, ON light go out as well as the AVAIL light on the START pb
• If the aircraft was using APU bleed air, the APU keeps running for cooling period of 60 seconds
• At 7% the inlet flap closes

Question 6

Describe the start sequence for the APU

Answer 6

• When the inlet flap is completely open, the APU starter is
  energized
• 1,5 sec after the starter is energized, the ignition turns ON
• At 55% the starter is de-energized and ignition turns OFF
• 2 sec after N reaches 95%, or when N is above 99,5% the ON light on the START pb goes out and the AVAIL light comes on

Question 7

What does the ON light on the APU START pb-sw indicate?

Answer 7

The APU start sequence is in progress

Question 8

When will APU speed (N) become amber?

Answer 8

102% or more

Question 9

When will APU speed (N) become red?

Answer 9

107% or more

Question 10

What causes an automatic emergency shutdown of the APU?

Answer 10

APU fire on the ground

Question 11

What causes the APU inlet flap to open?

Answer 11

Pressing the MASTER SW pb

Question 12

What is the APU start cycle limitations?

Answer 12

After 3 starter motor duty cycles, wait 60 min before trying 3 more cycles

Question 13

The APU may be started up to what altitude?

Answer 13

At any altitude using normal aircraft electrical power

Question 14

What is the purpose of the ECB (Electronic Control Box)?

Answer 14

It is a controller that performs the bulk of the APU system logic

Question 15

What is the highest altitude the APU can supply bleed air for engine start while providing electrical power?

Answer 15

20000 ft

Question 16

In regards to APU BLEED, what is the max altitude for airconditioning and pressurization (single pack operation)?

Answer 16

22 500 ft

Question 17

What is the highest altitude the APU can supply bleed air for air-conditioning and pressurization in dual pack configuration?

Answer 17

15000 ft

Question 18

With the APU green AVAIL light ON and the EXT PWR blue light illuminated, which system is powering the aircraft?

Answer 18

EXT PWR

Question 19

With the APU green AVAIL light ON ane the EXT PWR green AVAIL light ON, which system is powering the aircraft?

Answer 19

APU

Question 20

With the APU running and supplying bleed air, how do you shut it down?

Answer 20

APU BLEED pb OFF
APU MASTER sw OFF and APU will cool down and then shut down

Question 21

During the cool down cycle can you still use the APU?

Answer 21

Yes, press the APU MASTER sw pushbutton

Question 22

What does an amber FAULT light in the APU MASTER sw pb indicate?

Answer 22

An ECB commanded auto shutdown of the APU has occurred

Question 23

During APU start, what happens to the SD?

Answer 23

The APU page appears, until RPM>75% for >10secs or switched off.

Question 24

What is the max EGT for APU running for the A320?

Answer 24

675 deg C

Question 25

Max EGT for APU start below 35 000 ft for the A320?

Answer 25

1 090 deg C

Question 26

Up to what altitude can the APU provide bleed air with a single pack?

Answer 26

22 500 ft

Question 27

What is the start limit altitude on battery only?

Answer 27

25’000 ft