APU

Question 0

Describe the APU.

Answer 0

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

Question 1

What kind of APU is on the aircraft?

Answer 1

Sundstrand APS 2300

Question 2

What controls the APU?

Answer 2

A dedicated FADEC

Question 3

What battery is used for the APU start?

Answer 3

BATT 2 powers the starter

BATT 1 powers the FADEC and EICAS for monitoring

Question 4

What is the fuel source for the APU?

Answer 4

Right fuel tank

Left fuel tank through crossfeed valve

Question 5

What fuel pump is used for APU start?

Answer 5

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

Question 6

Well the APU you shut down automatically if speed and acceleration rate isn’t reached in the starting cycle time?

Answer 6

Yes

Question 7

What does moving the APU start switch to “OFF” do?

Answer 7

Initiates normal APU shut down
1-minute cooldown
No pneumatics (electrics only for 1 minute)

Question 8

Can the APU shutdown be canceled?

Answer 8

Yes, by moving the START switch back to “ON” before the 1-minute cooldown is over.

Question 9

How is the APU you shut down immediately?

Answer 9

APU emergency stop button
No 1-minute cooldown.
Turning the batteries OFF with APU you switch off

Question 10

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

Answer 10

APU will shut down immediately

Question 11

When will automatic shutdown of the APU occur?

Answer 11

• Ground: overspeed, under speed, FADEC critical fault, fire, overheat, low oil pressure
• Flight: overspeed, under speed, FADEC critical fault

Question 12

Can the APU be started after a critical fault?

Answer 12

No