APU

Question 1

APU

Answer 1

Single-Stage gas turbine engine

Question 2

APU provides what?

Answer 2

Pneumatic air and AC power

Question 3

Does the APU have its own FADEC?

Answer 3

Yes

Question 4

APU is normally fed from which wing tank?

Answer 4

Right wing tank

Question 5

Can the APU be fed from the left tank?

Answer 5

Yes, via the crossfeed

Question 6

What provides pressure if DC power only?

Answer 6

DC fuel pump will supply fuel pressure

Question 7

If AC power is available and the engine is not running what provides pressure?

Answer 7

AC fuel pump

Question 8

APU bleed air provides pneumatic air for what?

Answer 8

• Air conditioning
• Pressurization
• Water pressurization

Question 9

The FADEC monitors and will command auto shutdown in flight for what conditions?

Answer 9

Over-speed, under-speed and FADEC critical fault

Question 10

Automatic shutdown on ground for which conditions?

Answer 10

• Over-speed
• Under-speed
• FADEC critical fault
• Fire
• Overheat
• Low oil pressure
• High oil temperature
• Sensor failure

Question 11

APU selector knob controls?

Answer 11

Normal start and shutdown

Question 12

APU selector knob to OFF?

Answer 12

Removes pneumatics only, placing the APU into a 1-minute cool down period before shutting down
-Can be cancelled by reselecting to ON within 1 minute

Question 13

EMER STOP button is used for what?

Answer 13

Abnormal shutdown without a 1 minute cool down period

Question 14

At what % is electrics and pneumatics usually available after the APU is started?

Answer 14

95%

Question 15

What kind of APU does the aircraft have?

Answer 15

Sundstrand APS 2300

Question 16

Describe the APU?

Answer 16

Constant speed, Single-stage impeller with 2-stage axial-flow turbine with independent oil system

Question 17

What controls the APU?

Answer 17

A dedicated FADEC

Question 18

What battery is used for APU start?

Answer 18

BATT 2 powers the starter

BATT 1 powers the FADEC and EICAS for monitoring

Question 19

What is the fuel source for the APU?

Answer 19

The right tank, left tank through the cross-feed valve

Question 20

What fuel pump is used for APU start?

Answer 20

• Batteries “ON” only DC fuel pump in right tank
• AC powered airplane with ACMP 2
• Right engine running ejector fuel pump

Question 21

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

Answer 21

Yes

Question 22

What does moving the APU start switch to OFF do?

Answer 22

Initiates normal APU shutdown, with 1-minute cool down, no pneumatics, electrics only

Question 23

Can the APU shutdown be cancelled?

Answer 23

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

Question 24

How is the APU shut down immediately?

Answer 24

APU emergency stop button (no 1-minute cool down)

Question 25

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

Answer 25

APU will shut down immediately

Question 26

When will automatic shutdown of the APU occur on the ground?

Answer 26

• Overspeed
• Underspeed
• FADEC critical fault
• Fire
• Overheat
• Low oil pressure
• High oil temp
• Sensor failure

Question 27

When will automatic shutdown of the APU occur in flight?

Answer 27

• Overspeed
• Underspeed
• FADEC critical fault

Question 28

Can the APU be started after a critical fault?

Answer 28

No