APU

Question 1

Elec sources for starting?

Answer 1

Ground power
Engine driven generator
APU battery provided DC ESS bus powered

Question 2

Key altitudes for function

Answer 2

Starts below FL200

Supplied bleed air and elec power <22,500’

Only 1 APU generator can operate in flight

Question 3

Basic structure

Answer 3

2 rotors
N1 - Power rotor
N2 - High Pressure rotor

Air enters via the flap which closes automatically when APU not in use

2 APU generators (A and B) that supply constant 400Hz elec. Each cam replace any other generator and total AC can be supplied by both gens operating (although only 1 can operate in flight)

Question 4

ECB? Electrical Control Box

Answer 4

Controls operation, start and shutdown of APU

Question 5

How long wait between APU MASTER SW and APU START PB?

Answer 5

5 secs