APU

Question 1

What does the APU supply?

Answer 1

28v DC power to main feeder bus. Bleed air to ECS

Question 2

What is the APU fuel consumption?

Answer 2

90kg / hour

Question 3

What are the APU restrictions?

Answer 3

Ground use only Can’t start during fueling operations Can’t be operated during gravity fueling Gen on first before bleed air Must not be operated when de-icing Must not be operated unattended with passengers on board

Question 4

What happens if you forget the APU on for takeoff?

Answer 4

Shuts off automatically on liftoff. (WOW switch)

Question 5

Can the APU bleed air be on with engine bleeds selected on? What about a ground air cart?

Answer 5

No - desensitized by WOW Yes

Question 6

Where does the APU get it’s fuel supply from?

Answer 6

Left tank

Question 7

How long should you wait after starting the APU before you turn on the bleed air?

Answer 7

3-5 minutes

Question 8

What are the APU temperature limits? ….with inlet louveres?

Answer 8

-54°C to 50°C or ISA +35°C 21°C with inlet louvers installed.

Question 9

APU starting limits

Answer 9

1 minute on, 5 minutes off 1 minute on, 30 minutes off and maintenance action required.

Question 10

What is a nice trick to increase success rate in starting the APU in winter?

Answer 10

Press the self test then wait 3-5 minutes before pressing the start button.

Question 11

What precaution must be taken when using external power to ensure that the APU GEN comes on line in the event of GPU failure?

Answer 11

APU GEN needs to be reset or else it doesn’t automatically kick in once GPU is offline. Therefore just cycle the APU GEN off then on after start up.

Question 12

If pressing the APU PWR button does not shut down the APU, what can be done to shut down the APU?

Answer 12

Press the FIRE TEST button on the Fire Protection Panel (APU section is on the left part of FPP).