APU

Question 1

What altitude can the APU provide electrical power to?

Answer 1

41,000

Question 2

Max altitude for APU bleed air?

Answer 2

17,000

Question 3

Max altitude for APU bleed air AND electrical load?

Answer 3

10,000

Question 4

How long should the APU be run before utilizing bleed air?

Answer 4

One minute

Question 5

What two AC power sources can power the APU for start?

DC source?

Answer 5

External power
Engine driven generator

Battery

Question 6

What happens if the battery switch is selected OFF with the APU running?

Answer 6

The APU automatically shuts down on the ground or in flight due to loss of its Electronic Control Unit (ECU)

Question 7

What is the indication that the APU is ready to accept an electrical or bleed load?

Answer 7

The APU GEN OFF BUS light illuminates

Question 8

T/F: The LOW OIL PRESSURE light normally illuminates during APU start

Answer 8

True

Question 9

What happens when the APU switch is moved to the OFF position?

Answer 9

The APU generator trips off if it was connected
The APU bleed air valve closes
The APU begins a 60 second cooling period before shutting down

Question 10

How can the APU be shut down immediately, without the 60 second cool down?

Answer 10

Pulling the fire handle up

Pulling the external fire control handle in the aft section of the right main wheel well

Question 11

What conditions cause an automatic APU shutdown?

Answer 11

APU fire
Low oil pressure
High oil temperature
Over speed
Fuel control unit failure
EGT exceedance
Other system faults

Question 12

If speed or EGT exceeds predetermined levels when the APU is providing electrical load only, what happens?

Answer 12

Some electrical load is automatically shed

Question 13

If speed or EGT exceeds predetermined levels when the APU is providing electrical load and bleed air, what happens?

Answer 13

The ECU (electronic control unit) reduces bleed air while maintaining electrical load

Question 14

If speed or EGT exceeds predetermined levels during engine start, the APU does what?

Answer 14

Electrical pad shedding occurs prior to reducing bleed air

Question 15

What does the amber OVERSPEED light with the APU mean? When will it extinguish?

Answer 15

RPM limit has been exceeded
Self test fail

Illuminated for 5 minutes after the APU switch is OFF

Question 16

What does the amber FAULT light with the APU mean? When does it extinguish?

Answer 16

Malfunction exists which has caused the APU to automatically shut down

Extinguishes 5 mins after APU switch is turned OFF

Question 17

What is the LOW OIL PRESSURE light associated with the APU? When will it extinguish?

Answer 17

Oil pressure is low and has caused an automatic shutdown

Normally illuminated during start. Extinguishes when low oil pressure no longer present, or 5 mins after APU switch turned OFF

Question 18

What does the blue MAINT light associated with the APU? Can the APU be run? What should the crew do?

Answer 18

There is a maintenance problem with the APU

APU May be operated

Maintenance must be notified

Extinguishes when the APU switch is in the OFF position

Question 19

Fuel for the APU normally comes from where?

Answer 19

Left side of fuel manifold when the AC pumps are operating. If fuel pumps are not operating, fuel can be suction fed from the main tank number 1

Question 20

T/F: Fuel is heated to the APU to prevent icing

Answer 20

True

Question 21

Will the APU fire bottle automatically discharge if a fire is detected?

Answer 21

No

Question 22

Will the APU automatically shutdown if a fire is detected?

Answer 22

Yes