APU

Question 1

What happens when the APU master button is selected ON?

Answer 1

The APU fuel shutoff valve opens and the ECU is energized.

Question 2

When does the APU indicate “READY TO LOAD”?

Answer 2

When the RPM has reached 94.5% + 3 to 5 seconds.

Question 3

What will cause the APU automatic shutdown sequence to occur while on the ground?

Answer 3

Overspeed, overcurrent, overtemp (EGT), low oil pressure, high oil temperature, loss of EGT or RPM signals, and loss of power to the DC BUS 2.

Question 4

What will cause the APU automatic shutdown sequence to occur in-flight?

Answer 4

Overspeed

Question 5

During an APU shutdown, don’t turn off the APU MASTER until the RPM is below __%

Answer 5

10%

Question 6

Must the APU be monitored in flight?

Answer 6

Yes

Question 7

Must the APU be monitored on the ground?

Answer 7

No

Question 8

Is it permissible to operate the APU in its amber EGT region?

Answer 8

Yes, but for emergency use only

Question 9

Must you monitor the start and shutdown of the APU?

Answer 9

Yes

Question 10

How should the APU be shutdown?

Answer 10

From the loaded condition

Question 11

Is it required to shut the APU down for airplane de-icing

Answer 11

Yes and must remain off for subsequent taxi and takeoff.

Question 12

When is it not permitted to use the APU bleed for ECS operation on the ground?

Answer 12

With one or both engines running, except as necessary for takeoff

Question 13

What is the maximum altitude for APU operation?

Answer 13

30,000 ft

Question 14

What is the maximum altitude for main engine airstart with APU assistance?

Answer 14

30,000 ft

Question 15

What is the maximum altitude for APU restart in flight?

Answer 15

20,000 ft

Question 16

What are the APU starter limitations?

Answer 16

3 consecutive starts or start attempts with 1 min 30 second max combined starter running time, which must be followed by 10 minutes off.

Question 17

How long after an APU shutdown may the APU be restarted?

Answer 17

2 minutes after the APU MASTER selected off

Question 18

Can the APU be restarted following an automatic shutdown without a failure message indicated?

Answer 18

Yes, but only once. If the restart is unsucessful, no further restart attempts are allowed.

Question 19

Can the APU be restarted following an automatic shutdown with an amber failure message displayed?

Answer 19

No

Question 20

Can the APU be restarted following a manual shutdown due to a hot start?

Answer 20

No

Question 21

What is the maximum continuous load of the APU starter/generator?

Answer 21

400 Amps

Question 22

Wait at least __ minute(s) for APU stabilization before APU bleed ON

Answer 22

One minute

Question 23

If the APU bleed is used during takeoff, when should the switch back to engine bleeds be accomplished?

Answer 23

After passing acceleration height, but no higher than 1,500 above airport elevation.

Question 24

Wait ___ minute(s) after the APU MASTER button is selected off before attempting a restart of the APU.

Answer 24

Two