APU

Question 1

What kind of APU is on the aircraft?

Answer 1

Sundstrand APS 2300

Question 2

Describe the APU.

Answer 2

Constant speed
Single-stage impeller with a 2-stage axial-flow turbine
Independent oil system

Question 3

What controls the APU?

Answer 3

A dedicated FADEC

Question 4

What battery is used for the APU start?

Answer 4

BATT 2 powers the starter
BATT 1 powers the FADEC and EICAS for monitoring, fire protection, and fire detection

Question 5

What is the fuel source for the APU?

Answer 5

Right fuel tank
Left fuel tank through the crossfeed valve

Question 6

What fuel pump is used for APU start?

Answer 6

Batteries ‘ON’ only: DC fuel pump in right tank
AC powered airplane: ACMP 2
Right engine running: Ejector fuel pump

Question 7

Will the APU shutdown automatically if speed and acceleration rate isn’t reached in starting cycle time?

Answer 7

Yes

Question 8

What does moving the APU start switch to ‘OFF’ do?

Answer 8

Initiates normal APU shutdown
1-minute cool down
No pneumatics (electrics only during the 1 minute cool-down)

Question 9

Can the APU shutdown be cancelled?

Answer 9

Yes, by moving the START switch back to ‘ON’ before the 1-minute cool down is over

Question 10

How is the APU shutdown immediately?

Answer 10

APU emergency stop button
No 1-minute cool down period

Question 11

What will happen if batteries are turned OFF during the 1-minute cool-down period?

Answer 11

APU will shut down immediately

Question 12

When will automatic shutdown of the APU occur?

Answer 12

Ground:
Underspeed
Overspeed
FADEC critical fault
Fire
Overheat
High oil temperature
Low oil pressure
Sensor failure
Flight:
Underspeed
Overspeed
FADEC critical fault

Question 13

Can the APU be started after a critical fault?

Answer 13

No