APU

Question 1

What does the APU provide?

Answer 1

Pneumatic and electrical AC power

Question 2

What is the APU pneumatic power used for?

Answer 2

1) Engine starting

2) Supply bleed air to the air conditioning packs

Question 3

What does the APU generator supply?

Answer 3

115 volts 40 KVA to the electrical system

Question 4

How is the APU controlled?

Answer 4

Dedicated FADEC unit automatically monitors and controls the APU

Question 5

What does the APU EMER STOP button do?

Answer 5

Closes the APU fuel shutoff valve, shutting down the APU with no cool down period

Question 6

Where does the APU get it’s fuel?

Answer 6

1) DC power only available: DC fuel pump in right wing tank
2) AC power available and #2 engine is NOT running: AC fuel pump
3) #2 engine running: Ejector fuel pump from the right wing tank

Question 7

What can the APU supply?

Answer 7

1) Electrical AC power up to 33,000’
2) Bleed air for engine starting up to 21,000’
3) Bleed air for air conditioning up to 15,000’

Question 8

Max altitude for APU start?

Answer 8

30,000’

Question 9

When is pneumatic and electrical loading available from the APU?

Answer 9

3 sec after the APU speed has reached 95%

Question 10

APU ground start sequence?

Answer 10

FADEC initiates ignition at approximately 6% RPM, and fuel flow 0.5 sec later. Battery #2 energizes the electronic starter controller. After a light off occurs, FADEC commands the starter to cut out at approximately 50% RPM

Question 11

APU in-flight start sequence?

Answer 11

FADEC initiates ignition at approximately 7-17% RPM, and fuel flow 0.25 sec later. After a light off occurs, FADEC commands the starter to cut out at approximately 50% RPM

Question 12

APU normal shutdown sequence?

Answer 12

• APU selector knob to OFF
• Pneumatic power removed immediately, electrical power removed at the end of a 1 min cooldown period
• APU SHUTTING DOWN EICAS message appears at the end of the cooldown period and disappears at the end of the spooldown period
• If APU selector is turned back to ON during shutdown, it will cancel the sequence

Question 13

APU FADEC shutdown protection on the ground?

Answer 13

• Overspeed
• Underspeed
• FADEC critical fault
• APU fire
• APU EGT over temp
• APU high oil temp
• APU low oil pressure
• Sensor fail

Question 14

APU FADEC shutdown protection in-flight?

Answer 14

• Overspeed
• Underspeed
• FADEC critical fault

Question 15

APU location?

Answer 15

Airplane tailcone