APU

Question 1

To protect the unit from thermal shock, the APU control system incorporates a timedelay
feature permitting APU cooling before shutdown. Which of the following
statements is/are correct:

Answer 1

Both statements are correct.

Question 2

What does the APU RUN light indicate?

Answer 2

The APU may be used to supply electrical power and

bleed air

Question 3

What can cause the APU FAULT light to illuminate?

Answer 3

APU fuel valve NOT in commanded position

Question 4

What is the maximum operating altitude for the APU?

Answer 4

Aircraft maximum certified altitude

Question 5

What occurs when the APU selector is momentarily positioned to START?

Answer 5

Initiates automatic start sequence

Question 6

What does the APU FAULT light indicate?

Answer 6

APU automatic fault shutdown

Question 7

What affect does the Battery switch selected to OFF have on the APU if running?

Answer 7

In flight, none. On the ground, causes the APU to shut

down with a cool down if required

Question 8

What are the electrical requirements for starting the APU?

Answer 8

Both the APU battery and the aircraft main battery

Question 9

When does the APU shut down immediately?

Answer 9

When an APU FAULT light illuminates

Question 10

How can the APU shutdown be discontinued if the APU selector was inadvertently
moved to OFF, but the RUN is still illuminated?

Answer 10

Momentarily moving the selector to START cancels the

shutdown signal

Question 11

What causes the EICAS advisory message APU Fuel Val to appear?

Answer 11

APU Fuel Val fails to reach the commanded position

Question 12

How many APU start attempts are allowed in a 60‐minute period?

Answer 12

3

Question 13

Which of the following describes the START position of the APU selector?

Answer 13

Momentary, spring‐loaded to ON