Auxiliary Power Unit

Question 1

Max permissible load on the APU Generator

Answer 1

40 KVA to 41,000ft

Question 2

Max altitude for starting the APU

Answer 2

37,000 FT

Question 3

Max altitude for APU operation

Answer 3

41,000 FT

Question 4

Max altitude for APU bleed air extraction

Answer 4

25,000 FT

Question 5

Max speed with APU door open

Answer 5

220 KIAS if APU not operating

Vmo/Mmo if APU is operating

Question 6

What battery voltage is required before starting the APU

Answer 6

22 volts on both Main and APU batteries

Question 7

What does the main battery power during an APU start

Answer 7

APU ECU

Question 8

What does the APU battery power during an APU start

Answer 8

Cranking of the 28 VDC start motor

Question 9

When will the AVAIL switch light illuminate on the APU

Answer 9

99% RPM plus 2 seconds

Question 10

What are the priorities of the APU?

Answer 10

Primary: Electrical
Secondary: Pneumatics

Question 11

When will the START portion of the START/STOP switch light extinguish on the APU?

Answer 11

46-60% APU RPM

Question 12

What are the APU starter limits?

Answer 12

No more than 3 start attempts in one hour.

2 Minutes delay between start attempts

Question 13

What type of APU is used on the CRJ 900?

Answer 13

Allied-Signal RE220