APU

Question 1

The APU should be operated for ________ before being used as a bleed air source

Answer 1

two minutes

Question 2

The blue GEN OFF BUS Light illuminates when ….

Answer 2

The APU is ready to accept a bleed air or electrical load

Question 3

T/F: an illuminated LOW OIL PRESSURE light is normal during start until the oil pressure is stabilized.

Answer 3

True

Question 4

T/F: The APU cannot be operated when the blue MAINT light is illuminated.

Answer 4

False. It can be operated, but maintenance should be notified

Question 5

T/F: In flight, if the APU is the only source of electrical power, all galley busses and main busses are automatically shed.

Answer 5

True

Question 6

The APU Bleed Air Valve is ________ controlled and __________ operated.

Answer 6

electrically; pneumatically

Question 7

T/F: The APU system will automatically discharge the dedicated APU fire bottle when it detects a fire

Answer 7

False. The bottle must be manually discharged.

Question 8

Immediate manual shutdown of the APU can be accomplished by two methods:

Answer 8

1. The APU FIRE switch located on the Fire Protection Panel
2. The APU Fire Control Handle located on the Ground Control Panel (aft section of right wheel well)

Question 9

The APU operates at a _______ speed to meet aircraft electrical demand

Answer 9

constant

Question 10

Fuel can be supplied to the APU from what 2 sources:

Answer 10

1. AC powered fuel pump (left manifold)
2. Suction feed from the No. 1 (main tank)

Question 11

The APU can get electrical power for its start from what sources?

Answer 11

Engine-driven generator, external power
or the battery

Question 12

T/F: A running APU will shut down if you remove electrical power from it

Answer 12

True. It’s Electronic Control Unit (ECU) requires power

Question 13

The APU’s Electronic Control Unit (ECU) does what 3 things during the APU automatic start sequence?

Answer 13

1. Opens the Fuel Shutoff Valve
2. Opens the Air Inlet Door
3. Illuminates the LOW OIL PRESSURE light

Question 14

When the APU switch is moved to the OFF position, the APU will continue to run for a ___________ period at which time its ECU will shut it down.

Answer 14

60 second cooling

Question 15

What are some of the things that will cause the APU to auto shutdown?

Answer 15

APU Fire, Overspeed, Low oil pressure, High Oil temp, FCU failure, EGT exceedance

Question 16

The APU amber annunciator lights will remain illuminated for _________ if any of them were illuminated when the APU switch was placed to off.

Answer 16

5 minutes

Question 17

When will the APU OVERSPEED light illuminate?

Answer 17

1. RPM exceedance causing an auto shutdown
2. Overspeed shutdown protection feature failed a self test during a Normal shut down

Question 18

What are the two types of APU airflow?

Answer 18

1. Combustion airflow (exhaust)
2. Cooling airflow (outside ambient air from the tail section of the aircraft cools the APU compartment, goes into an oil cooler, then exits out with the combustion air)

Question 19

Bleed air from the APU enters the pneumatic system on which side of the manifold?

Answer 19

Left

Question 20

Placing the APU switch to the OFF position does what when the APU is running?

Answer 20

1. Trips the APU generator of the bus(s) if connected
2. Closes the APU Bleed Air Valve

(APU will continue to run during 60 second cooling period)