APU

Question 1

What are the start sources for the APU, and which one do we normally use?

Answer 1

TR or APU battery

We use APU battery

FCOM 2 7.14.12

Question 2

Can the APU be operated in flight?

Answer 2

The APU may be left running in-flight up to 20,000ft

It can power one pack up to 15,000ft

FCOM 2 7.30.1

Question 3

Is electrical power available from the APU in flight? How about APU bleed air in flight?

Answer 3

Electrical power is not available in-flight.

Bleed is available to operate one pack up to 15,000ft

FCOM 2 7.30.1

Question 4

What APU components are powered by the APU battery?

Answer 4

The inlet door
APU controller
DC fuel pump
APU fire detection system

FCOM 2 7.30.1

Question 5

What APU components are powered by the Main battery?

Answer 5

APU fire extinguisher
APU fuel valve
Standby power for the APU controller

*during start, all components except the starter are transferred to the main battery

FCOM 2 7.30.1

Question 6

What powers the APU starter during a battery start sequence?

Answer 6

The APU battery

FCOM 2 7.30.1

Question 7

What happens if the TR should overheat with the start source in TR?

Answer 7

Start power is transferred to the battery and the start continued on APU battery power

FCOM 2 7.30.2

Question 8

How does a TR failure affect APU starting?

Answer 8

A failure other than overheat does not provide automatic switching to the APU battery. Moving the start source selector to battery removes the TR from the starting circuit and allows APU starting on battery power.

FCOM 2 7.30.2

Question 9

When does the EICAS memo message APU RUNNING display?

Answer 9

When the APU selector is ON and APU N1 RPM exceeds 95% N1.

FCOM 2 7.30.2

Question 10

Describe the APU shutdown sequence

Answer 10

The APU bleed valve closes
The APU continues running unloaded for a sixty second cool-down period
After cool-down the APU shuts down

FCOM 2 7.30.2

Question 11

What would happen if the battery switch is positioned OFF prior to completion of the APU shutdown cool-down period?

Answer 11

The APU will shut down immediately.

FCOM 2 7.30.2

Question 12

How long should you wait before turning the battery switch OFF after the APU selector is rotated to OFF, and why?

Answer 12

2 minutes or fire detection capability will be lost.

FCOM 2 7.30

Question 13

What would cause the APU to shut down automatically?

Answer 13

APU fire detected

FCOM 2 8.20.2