APU

Question 1

What type of APU is installed

Answer 1

SPU300

Question 2

What is the maximum APU RPM? (AFM Limitations)

Answer 2

105%
Note: The APU FADEC governs the APU to 100% rpm. If the value is anything other than
100%, there is something wrong.

Question 3

What is the maximum altitude for APU generator operations? (AFM Limitations)

Answer 3

51,000ft

Question 4

What is the maximum altitude for starting the APU in flight? (AFM Limitations)

Answer 4

45,000ft

Question 5

What is the maximum altitude for bleed air extraction from the APU? (AFM Limitations)

Answer 5

25,000ft

Question 6

What is the minimum temperature for starting a cold soaked APU on the ground? (AFM Limitations)

Answer 6

-40°C

Question 7

How many start attempts are permitted on the APU? (AFM Limitations)

Answer 7

3 per hour

Question 8

What is the maximum OAT for APU bleed air extraction on the ground for air conditioning
operations? (AFM Limitations)

Answer 8

48°C

Question 9

What is the maximum load rating for the APU? (FCOM2, Electrical)

Answer 9

60KVA up to 45,000ft without restriction
40KVA above 45,000ft

Question 10

When does the APU door position appear on the EICAS and the SERVICE synoptic?

Answer 10

If the door is not in the commanded position
Note: An amber APU DOOR FAIL CAS message also comes on

Question 11

When is manual operation of the APU bleed control valve (BCV) not possible?

Answer 11

Anti-Ice is active
LH engine pressure-regulating valve (PRV) is manually opened
RH engine PRV and the crossbleed valve are manually opened

Question 12

Can you dispatch with the APU door failed open? (DDG)

Answer 12

Yes, with restrictions
Note: Located in Airborne Auxiliary Power chapter in DDG. The primary issue is the
APU windmilling without lubrication. The windmill limit is 7%. QRH2

Question 13

What conditions must be met before using the oil replenishing system for the APU?

Answer 13

Weight on wheels
APU has been shut down for a minimum of 10 minutes
OAT is warmer than -12⁰C

Question 14

Which fuel pump supplies pressure to the APU during start?

Answer 14

When AC power is not available, the right auxiliary DC pump supplies fuel pressure
When AC power becomes available from the APU generator or another source, the right primary
AC fuel pump starts, and the right auxiliary DC pump shuts down

Question 15

What happens to the APU bleed control valve (BCV) if the APU is pressurizing the pneumatic
manifold, and then the left engine bleed valve opens?

Answer 15

The APU BCV automatically closes
Note: interlock protection: the BMC control logic ensures that the BCV cannot be opened
when another bleed source is supplying the bleed air manifold

Question 16

How is an emergency shutdown of the APU accomplished?

Answer 16

Pressing APU FIRE PBA
Pushing the APU SHUTOFF button on the aft services panel
Pushing the red APU shutdown switch in the APU compartment

Question 17

What is the sequence of actions when the APU FIRE PBA is pressed?

Answer 17

APU firewall fuel SOV closes
APU fuel control unit shuts off the fuel
APU generator is taken off line
APU Bleed Control Valve (BCV) is closed
BTL 2 squib armed, AVAIL green PBA comes ON