Auxiliary Power Unit

Question 1

What is the range where the APU starter cut-out will occur?

Answer 1

46% on the ground and 46-60% in flight.

Question 2

What are the APU starter limits?

Answer 2

Three attempts in a one hour with a two minute waiting period between each attempt

Question 3

What will the APU automatic fire protection provide in flight?

Answer 3

Automatic shutdown of the APU, but not automatic discharge of the fire bottle.

Question 4

Where does fuel to operate the APU come from?

Answer 4

The left collector tank via a dedicated 28 VDC APU fuel pump.

Question 5

Prior to APU start the minimum battery voltage should be_______________.

Answer 5

22 volts on both batteries

Question 6

The APU will not start if the RPM is rotating above what speed on the ground versus flight?

Answer 6

5 percent on the ground 12 percent in flight

Question 7

The maximum altitude for starting the APU is ________. It can be operated up to _________.

Answer 7

37,000 feet/41,000 feet.

Question 8

APU bleed air can be used in flight up to what altitude?

Answer 8

25,000 feet.

Question 9

The APU can be used as a source of bleed air for the aircraft ice protection systems.

Answer 9

False

Question 10

If the APU door is stuck open or its position is uncertain, what must be done? Also what is the reason?

Is there a way around the restriction?

Answer 10

Maintain a max airspeed of 220 knots.

To prevent APU from windmilling without proper lubrication and to ensure the APU RPM remains below 12 percent in the event it becomes necessary to start the APU in flight.

Yes normal speeds can be used if APU is running

Question 11

The APU control system ensures that priority is given to ____________.

Answer 11

Electrical power

Question 12

APU bleed air is controlled by modulating the

Answer 12

APU Load Control Valve (LCV)

Question 13

What is indicated by the illumination of the PUMP Fail light?

Answer 13

the APU pump failed to energize

Question 14

What is indicated by the illumination of the PUMP FAIL light?

Answer 14

the APU fuel shutoff valve is not in the commanded position

Question 15

What is the primary purpose of the APU?

Answer 15

provide electrical power

Question 16

will the APU shutdown on due to high oil temp or low oil pressure?

Answer 16

yes on the ground

No if in flight

Question 17

If the APU shuts down on the due to fire will the bottle fire?

Answer 17

Yes on the ground

No if in flight

Question 18

At what altitude will the surge control valve open?

Answer 18

17000

Question 19

If the APU Pump fails will the APU continue to operate?

Answer 19

Yes but it cannot be restarted without the pump

Question 20

What is the purpose of the LCV

Answer 20

the load control valve varies pneumatic load to ensure electrical power and 45 psi in the manifold

Question 21

can apu bleed air be used by anti ice system?

Answer 21

no

Question 22

What powers the APU door and what powers the ECU?

Answer 22

The APU battery provides power to the door and is secondary for the ECU. The main battery is the primary power source for the ECU

Question 23

If the APU is left unattended can the ground crew shut it down?

Answer 23

Yes through the use of an APU shutoff switch on the forward nose or in the APU compartment