APU

Question 1

How many lights/items appear during an APU fire test?

Answer 1

8. 2 Overhead / 4 Master Caution panel / 2 CAS

Question 2

APU is guaranteed to start at or below

Answer 2

39,000’ (may start up to 43,000’)

Question 3

What is the max operating altitude of the APU?

Answer 3

45,000’

Question 4

APU Generator will come on when it has reached:

Answer 4

2 seconds after it has reached 99%

Question 5

On APU Start, when does Isolation valve open?

Answer 5

1 minute after APU is online.

load control valve is inhibited OFF during APU start unless EGT before start >150°. There is no delay when airborne

Question 6

If started in the air, the APU will remain in ESSENTIAL mode for how long after landing?

Answer 6

15 minutes

Question 7

APU Essential and Nonessential modes depend upon which system

Answer 7

WOW

Question 8

The APU surge control value operates at what altitude and above?

Answer 8

16,500 - to prevent high altitude compressor stall.

Question 9

The bleed air augmentation valve opens at what altitude?

Answer 9

35,000’ and higher - allows 400°F bleed air into inlet

Question 10

The Bleed Air Augmentation Valve delays APU start for

Answer 10

15 seconds to allow warm up

Question 11

What temp range is APU oil tank heated to

Answer 11

+21°C to 43°C regardless of whether the APU is in use

Question 12

Depressing the APU STOP switch cause the APU

Answer 12

to shut down by simulating overspeed

Question 13

APU Starter limitations

Answer 13

3 start attempts, one hour cool down

Question 14

What are the APU starter limitations when using Ext DC?

Answer 14

3 start attempts, separated by 15 minutes, then one hour cool down

Question 15

How is an APU start manually aborted?

Answer 15

APU STOP, which triggers the 108% overspeed circuit resulting in an immediate shutdown.

Question 16

The minimum fuel temp required prior to APU start

Answer 16

> -30°C

Question 17

Min battery voltage for APU start

Answer 17

22 VDC

Question 18

When is the APU air load control valve automatically inhibited OFF/how long?

Answer 18

During start, after start for 90 seconds

Question 19

How is it determined that all parameters are acceptable for APU start?

Answer 19

APU Ready light

Question 20

Will the APU start be inhibited with the absence of the READY light?

Answer 20

No, however the APU air inlet door must be verified open prior to start

Question 21

Describe the normal APU shutdown - ground, air

Answer 21

Ground - Cooldown period is initiated, loads are shed within 2 sec. APU RPM decreases 1/2% for 60 seconds

Question 22

Why is there a requirement for turn OFF the right battery for an in-flight APU start with one or both main generators powered?

Answer 22

Because both batteries combined with their chargers produce too much amperage (starter torque) and may ramp the APU starter past the APU start envelope

Question 23

Is the APU electronic control unit still powered after the APU master switch is deselected?

Answer 23

Yes, for 5 minutes

Question 24

Can the APU provide pressurization in flight?

Answer 24

No

Question 25

If the APU is started on the ground and not shut down prior to takeoff, what mode will it be in flight?

Answer 25

Essential

Question 26

If landing with the APU running, how long will it stay in essential mode?

Answer 26

15 minutes

Question 27

The APU receives fuel from…

Answer 27

The motive flow line to the left fuel ejector in the left hopper

Question 28

When will APU generator power the AC buses after start?

Answer 28

2 seconds after it reaches 99% - with APU GEN switch ON

Question 29

At approx what RPM will the APU ECU close the external door during shutdown?

Answer 29

40%

Question 30

At what point will the APU ECU close the inlet door if the pilot uses the MASTER switch to shut down the APU?

Answer 30

Immediately

Question 31

When does the AFM allow the crew to run the APU inflight?

Answer 31

Four times
Single Gen Failure
Double Gen Failure
Single Engine Failure
Dual Engine Failure

When Checklist instructs.

Question 32

When do you check the oil level?

Answer 32

Between 15 and 30 minutes after shutdown.

Question 33

APU provides bleed air up to what altitude?

Answer 33

• 1,500 AGL for pressurization during a Bleeds-off takeoff

- Up to 30,000’, but current AFM limits use only allow for bleed air use up to 25,000’ for Main Engine Start in-flight.

Question 34

When does the AFM allow the crew to run the APU inflight?

Answer 34

Four times
Single Gen Failure
Double Gen Failure
Single Engine Failure
Dual Engine Failure

When Checklist instructs.