Auxillary Power Unit Flashcards Preview

CRJ900 Limitations, Systems > Auxillary Power Unit > Flashcards

Flashcards in Auxillary Power Unit Deck (23):
1

How much battery voltage is required to start the APU?

22 volts on both the main and APU batteries but it only takes the APU battery to actually start

2

What is the normal and non normal APU door indications.

Normal = DOOR OPEN or DOOR CLOSED on the status page

3

What is the APU interlock?

A function that prevents against back flow from the engines by closing the APU

4

What are the differences between an APU fire on the ground verse in the air

On the ground = bottle fires automatically
In the air = pilot controlled

5

What will occur if the APU pump fails while the APU is still in operation?

The APU solenoid pump pulls fuel to the APU

6

Why would it be normal to see a L AUTO XFLOW message while sitting at the gate with the APU running?
PSM 04-30-1

The APU pulls off the left collector tank

7

What's the primary purpose of the APU?

Electrical power

8

What indications would you find with an APU pump failure?

Yellow outline of pump
APU Pump caution light

9

What is the critical rotation speed of the APU

An RPM that is fast enough to require oil but to slow to draw oil through the system.
5 - 30%

10

When does the APU door open

On the ground with PWR/fuel switch
In the air with the APU Start/Stop switch button

11

When can you restart the APU after it's been normally shut down?

Gauges go away
Inbite test is complete
2 minutes rest

12

Which pump provides pressurized fuel to the APU?
PSM 04-30-1

APU fuel pump

13

What does the green AVAIL light indicate on the APU START/STOP push button?

The APU is ready for electrical and pneumatic loading.

14

After the APU completes the start and is stabilized, what do you check?

Voltage frequency and loads are normal

15

When might you get an APU GEN OFF caution message?

APU GEN is selected off and the APU is ready to load

16

How does the APU start sequence differ in the air and on the ground?

In flight the APU door will not open till the START/STOP is selected

17

What prevent surges and stalls in the APU?

Check valve in my pneumatic ducting
Surge control valve
Interlock protection

18

When will the APU LCV close?

When PURSOVs open
When anti-ice is turned on
Bleed source is in manual mode

19

Will the APU shut down for high oil temp?

Yes

20

Is the red line on the APU dependent on altitude and temp?

Yes

21

Does an APU FAULT caution shut down the APU automatically

Only on the ground

22

How is the APU exhaust cooling air pulled through the compartment

Educator

23

When will the APU shut down automatically in the air

Fire
Over speed
ECU - loss of DC power, no signal so it doesn't know what the speed is