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 smeller with a 2-stage axial-flow turbine

Question 3

What is the voltage and kVA of the APU?

Answer 3

115VAC, 40 kVA

Question 4

What monitors and controls the APU?

Answer 4

Its own dedicated FADEC

Question 5

What battery is used for the APU start?

Answer 5

• BATT 2 powers the starter

- BATT 1 powers the FADEC and EICAS for monitoring

Question 6

What is the fuel source for the APU when the engines are running?

Answer 6

Right fuel tank (ejector pump)

Question 7

What fuel pump is used for APU start?

Answer 7

• When BATTs on only: DC fuel pump
• AC power on: AC fuel pump
• DC power only: DC fuel pump

Question 8

What normally provides fuel to the APU when the engine is not running?

Answer 8

• # 2 fuel tank
• AC power: AC fuel pump
• DC power only: DC fuel pump

Question 9

When does APU electrical and pneumatic loading become available?

Answer 9

3 seconds after the APU speed has reached 95%

Question 10

Describe the APU start sequence during a ground start

Answer 10

Starter engagement, ignition at 6%, fuel after 0.5 secs and starter cutout at 50%

Question 11

Describe the APU start sequence during an in-flight start

Answer 11

Starter engagement, ignition at 7-17%, fuel after 0.5 secs and starter cutout at 50%

Question 12

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

Answer 12

Yes

Question 13

What indication would you have of an APU auto-shutdown?

Answer 13

An APU FAIL EICAS message

Question 14

What does moving the APU start switch to OFF do?

Answer 14

• Initiates normal shutdown
• 1 min cool down
• Pneumatics removed immediately and electrical power is removed after the 1 minute cool down

Question 15

What happens when you rotate the APU master switch to ON?

Answer 15

Powers the FADEC and opens the APU shutoff valve

Question 16

Can the APU shutdown be cancelled?

Answer 16

Yes, by moving the START switch back to ON before the 1 min cool down is over

Question 17

Can the APU pneumatics be used during the cool down period?

Answer 17

No

Question 18

Can the APU electrical power be used during the cool down period?

Answer 18

Yes

Question 19

How is the APU shutdown immediately?

Answer 19

• APU EMER STOP button

- No 1 min cool down

Question 20

What is indicated by an illuminated red bar in the upper half of the EMER STOP button?

Answer 20

An APU fire

Question 21

What BUS provides APU fire protection>

Answer 21

DC ESS BUS 2

Question 22

What BUS provides APU fire detection?

Answer 22

DC ESS 1 and 2 (Using MAU 1 and 2). I think it may just be DC ESS BUS 1

Question 23

What happens when the APU EMERGENCY STOP button is pushed?

Answer 23

The APU fuel shutoff valve closes and the APU still shut down with no cooling period. A white stripe displays on the switch

Question 24

Selecting the APU control MASTER selector knob from On to OFF initiates a normal APU shutdown, monitored and controlled by?

Answer 24

FADEC

Question 25

How is the APU monitored and controlled?

Answer 25

FADEC

Question 26

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

Answer 26

APU will shut down immediately

Question 27

When will automatic shutdown of the APU occur?

Answer 27

- Ground: overspeed, underspeed, FADEC critical fault, fire, EGT overtime, sensor failure, high oil temp, low oil pressure - Flight: Overspeed, underspeed, FADEC critical fault

Question 28

The APU can be used for pneumatics to a max of what altitude?

Answer 28

15,000 feet

Question 29

What is the max altitude for operation of the APU electrical?

Answer 29

33,000 feet

Question 30

What is the max altitude for APU start?

Answer 30

30,000 feet

Question 31

Up to what altitude may the APU assist in engine start?

Answer 31

21,000 feet

Question 32

On which display would the crew find info regarding the operational status of the APU?

Answer 32

EICAS

Question 33

Where would you find the APU RPM and EGT indications?

Answer 33

On EICAS

Question 34

If both engine bleed and APU bleed is available which one has priority?

Answer 34

Engine bleed

Question 35

During APU start where does the fuel come from and what pump does it use when only DC power is available?

Answer 35

Right fuel pump and DC pump until AC power is available, then AC pump takes over

Question 36

With the right engine running and the APU running where does the fuel come from?

Answer 36

Engine ejector pump?

Question 37

The AMS controls the APU and engine bleeds. During an engine start what happens to the bleed valves?

Answer 37

The APU bleed valve opens which supplies the bleed air for the start. After the start the engine bleed valve opens and the APU bleed valve closes

Question 38

Do you get the APU cool down period when you press the APU emergency stop button?

Answer 38

No

Question 39

If you need the APU 50 secs into shutdown is there a way to get it back?

Answer 39

Yes, turn the APU master switch back to ON

Question 40

How would you operate the APU while using from from Tank 1?

Answer 40

Select XFEED selector to LOW 2

Question 41

In normal operations on the ground with APU running it would be normal to see the fuel imbalanced with less fuel in which tank?

Answer 41

Right tank

Question 42

Can the APU be started after a critical fault?

Answer 42

No

Question 43

Will the APU auto-shutdown inflight for an APU fire?

Answer 43

No

Question 44

What is the APU starter duty cycle?

Answer 44

- 1st and 2nd attempt: 60 secs on/60 seconds off | 3rd: 60 secs ON/5 mins off