AUXILIARY POWER UNIT

Question 1

1. The APU is located where on this airplane?

Answer 1

 In the tail, fireproof compartment

Question 2

2. If you tried to start the APU and had no luck, is there anything you could check?

Answer 2

 Battery switch on, fire handles in cockpit and in the wheel well

Question 3

3. How long can it take the APU to start?

Answer 3

 Up to 120 seconds

Question 4

4. What are some requirements to start the APU?

Answer 4

 BATT switch must be on and inlet door

must be fully open

Question 5

5. What happens if the APU has not started by the end of the start cycle?

Answer 5

 Auto shutdown

Question 6

6. What happens if the APU GEN OFF BUS light

has not illuminated by the end of the start cycle?

Answer 6

 Auto shutdown & fault light illuminates

Question 7

7. If a fault is sensed by the APU, what happens?

Answer 7

 Auto shutdown

Question 8

8. What are some of the things that will cause an

auto shutdown of the APU?

Answer 8

 Fire
 Low oil pressure
 High oil temperature 
 Overspeed
 Fuel control unit fail
 High EGT temperature 
 Other ECU faults

Question 9

9. How long should the APU be operated before using it as a bleed source?

Answer 9

 One minute

Question 10

10. Why is it recommended waiting one minute before selecting bleed source after APU start?

Answer 10

 To increase the service life

Question 11

11. Is it mandatory to wait one minute after APU

start to select as bleed source?

Answer 11

 No, but it is recommended. As soon as the APU GEN OFF BUS light illuminates it is ready to take a load.

Question 12

12. When the APU switch is moved to OFF, does the APU shut down immediately?

Answer 12

 No

Question 13

13. How could you shut the APU down

immediately?

Answer 13

 APU fire handle or BATT switch

Question 14

14. During engine start will the APU ECU favor

bleed air or electrical load?

Answer 14

 Bleed air

Question 15

15. At other times is this APU load logic the

same?

Answer 15

 No, electrical load is favored

Question 16

16. Does the battery switch have to be ON in order

to start the APU?

Answer 16

 Yes

Question 17

17. How do you know if the APU is ready to

accept a bleed air or electrical load?

Answer 17

 APU GEN off bus light illuminates

Question 18

18. What is indicated by the MAINT light?

Answer 18

 Maintenance should be notified

Question 19

19. Can you operate the APU with the MAINT light

on?

Answer 19

 You can still use the APU if required

Question 20

20. What is indicated by the APU LOW OIL PRESS

light?

Answer 20

 Start up or shutdown due to low oil pressure

Question 21

21. Can you operate the APU with the LOW OIL PRESS light on?

Answer 21

 No, this will cause an auto shutdown

Question 22

22. What is indicated by the APU FAULT light?

Answer 22

 Some fault caused auto shutdown

Question 23

23. What is indicated by the APU OVERSPEED

light?

Answer 23

 APU RPM limit exceeded with a corresponding auto shutdown

Question 24

24. What is indicated by an APU OVERSPEED light on shutdown?



Answer 24

 Feature has failed a self-test during a normal APU shutdown

Question 25

25. Will an APU LOW OIL PRESSURE alert shut the APU down before the start cycle is complete?

Answer 25

 No

Question 26

26. Approximately how long does it take for the

APU inlet door to open or close?

Answer 26

 20 seconds