APU

Question 1

How is the APU turbine built?

Answer 1

1 stage compressor
combustion chamber
2 stages turbine

Question 2

Max altitude for AC Power supply?

Answer 2

33,000ft

Question 3

Max altitude for bleed air supply?

Answer 3

Engine start up to 21,000ft
Air conditionning up to 15,000ft

Question 4

In what position is the APU anti-surge valve, on ground and in flight?

Answer 4

Closed on ground
Open in flight

Question 5

Oil press/temp limitations on APU?

Answer 5

T° max 275°C
Press min 35psi

Question 6

Fuel source for APU?

Answer 6

Right wing collector tank

All pumps can provide fuel to APU, incl. XFeed

Question 7

APU start limitations?

Answer 7

First start : 60 sec ON / 60 sec OFF
Second start : 60 sec ON / 60 sec OFF
Third start : 60 sec ON / 5 min OFF

Start electrical power provided by BATT 2

Question 8

Max altitude for an APU air start?

Answer 8

30,000ft

Question 9

When does the APU start to supply AC power and bleed air?

Answer 9

3 sec after reaching 95%

Question 10

What is the shutdown sequence of the APU?

When APU knob is placed in OFF position

Answer 10

Bleed air and electrical power are cut off
Cool down for 2 min
Fuel SOV closes
FADEC turns off 2.5 minutes after shutdown

Shutdown sequence can be cancelled by putting APU knob back to ON

Question 11

APU FIRE

Memory item

Answer 11

APU Emer Stop button PUSH IN

Closes the fuel SOV without the 2 min cool down

Question 12

Automatic APU shutdown on the ground

Give the possible reasons

Answer 12

• Overspeed/underspeed
• FADEC critical failure
• APU fire
• High EGT
• High oil temp / low oil press
• APU sensor failure

Question 13

Automatic APU shutdown in flight

Give the possible reasons

Answer 13

• Overspeed/underspeed
• FADEC critical failure

Question 14

APU limitations

Answer 14

• 108% RPM
• Start max EGT : 1032°
• Operation max EGT : 717°

Question 15

APU fuel consumption?

Answer 15

2kg per min (120kg per hour)