APU

Question 1

APU starting limits on battery

Answer 1

3 consecutive start attempts, followed by 1 hour cool down

Question 2

APU starting limits on external DC

Answer 2

3 start attempts, 15 min cool down between each attempt

Question 3

Max APU operating altitude

Answer 3

45000ft

Question 4

APU generator electrical load limit

Answer 4

100% (40KVA) sea level to 45,000 ft

Question 5

How is an APU start manually aborted?

Answer 5

Depress the APU stop switch, which triggers the 108% over speed circuit, resulting in an immediate start abort

Question 6

The min temp required for APU start is?

Answer 6

Greater than -30°c

Question 7

The min acceptable battery volts prior to APU start is?

Answer 7

22 VDC

Question 8

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

Answer 8

During APU start, and after APU start for 90 sec

Question 9

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

Answer 9

The APU READY light will be illuminated

Question 10

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

Answer 10

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

Question 11

Describe a normal APU shut down on the ground and inflight

Answer 11

A cool down period is initiated, loads are shed within 2 sec APU RPM decreases 1/2% for 60 sec

Question 12

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

Answer 12

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

Question 13

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

Answer 13

Yes for 5 min

Question 14

Can the APU provide pressurization in flight?

Answer 14

No

Question 15

What is the max altitude for APU operation to start?

Answer 15

39000

Question 16

If the APU was started on the ground, what mode will it be in flight?

Answer 16

Essential mode

Question 17

If landing with the APU running. How long will it stay in essential mode?

Answer 17

15 min

Question 18

The APU receives its fuel from what source?

Answer 18

The motive flow from the left fuel ejector

Question 19

Selecting what switch to the OFF position will close the APU fuel shut off valve immediately

Answer 19

The APU master switch

Question 20

Prior to starting the APU, how can the position of the right engine lower cowl door be checked?

Answer 20

Visually or checking the DOORS 2/3 synoptic display, or the amber cowl light on the apu control panel

Question 21

If necessary, how can the batteries be warmed prior to APU start?

Answer 21

Use an external AC power cart to charge and warm the batteries

Question 22

After APU start, when will the APU generator automatically power the electrical buses

Answer 22

2 sec after the APU achieves 99% RPM

Question 23

Would an APU FIRE CAS cause the APU to shutdown in-flight or on the ground?

Answer 23

Both on the ground and inflight

Question 24

At approximately what point will the APU ECU close the inlet door when the STOP switch is used to shutdown the APU

Answer 24

40% RPM

Question 25

At what point will the APU ECU close the inlet door when the MASTER switch is used to shut down the APU.

Answer 25

It will close the inlet door immediately

Question 26

If the APU continues to run in flight even though a fault has been detected that would normally cause it to shutdown on the ground, would the crew be aware?

Answer 26

Yes, by illuminating the amber APU ESSENTIAL CAS message