APU

Question 1

Primary function of the APU

Answer 1

AC power via 30 KVA generator

Question 2

What controls and monitors the APU

Answer 2

The ECU

Question 3

How is flow of air controlled through the compressor

Answer 3

Variable Geometry Diffuser

Question 4

What is the job of the VGD

Answer 4

prevents surges and stalls

Question 5

What accessories mounted on the APU gearbox

Answer 5

• AC Generator
• Fuel Control Unit
• Oil pumps
• Oil cooling fan
• DC starter motor

Question 6

What is the screened duct for on the left side of the fuselage

Answer 6

Air is drawn in by the oil cooler fan for oil cooling and ventilation of the APU enclosure

Question 7

How many pounds per hour does the APU burn

Answer 7

120 with electrical and bleed air loading

Question 8

What controls fuel supply to the APU

Answer 8

The SOV

Question 9

When does the APU SOV close

Answer 9

• APU PWR FUEL switch
• APU FIRE PUSH switch
• Automatically when fire is detected

Question 10

What happens when the APU PWR switch is pressed

Answer 10

DIGS

• APU IN BITE self test (5sec)
• RPM EGT Gauges displayed
• Intake door opens
• APU SOV OPEN status message
• XFLOW/APU pump starts

Question 11

When is starter motor de energized (START light goes out)

Answer 11

50% rpm

Question 12

What does green AVAIL light indicate

Answer 12

APU is ready for bleed air loading, happens at after 4 seconds after RPM reaches 99%

Question 13

Which battery is used for APU start

Answer 13

Main and the APU Battery
APU battery turns the APU Starter
Main Battery operates the ECU

Question 14

What conditions will the APU shut down in flight

Answer 14

• Fire
• Slow Start
• Overspeed
• DC power loss
• RPM signal loss
• ECU Failure

Question 15

What switch allows bleed air to be supplied to the 10th stage bleed air manifold

Answer 15

APU LCV on the Bleed Air Panel