APU

Question 1

AUDIO

Answer 1

AUDIO

Question 2

APU Selector: OFF

Answer 2

• APU BLEED CLOSED - Initiates SHUTDOWN - resets auto-shutdown fault logic except w/shutdown due to APU bleed air leak

Question 3

APU Selector: ON

Answer 3

• Opens APU fuel valve and inlet door - Arms APU bleed air isolation valve - Activates DC or two AC fuel pumps

Question 4

EICAS MEMO: APU RUNNING

Answer 4

APU RPM greater than 95%

Question 5

APU auto shutdown items (3)?

Answer 5

• Limit Exceedence - Fire - Battery Switch Off

Question 6

APU Cool down period?

Answer 6

Starts when switch placed in OFF and lasts for one minute. Wait 2 minutes after shutdown before turning off battery switch. This ensures fire detection capability.

Question 7

Normal APU starter power?

Answer 7

(TR) when UTILITY BUS 4 is powered.

Question 8

Can APU be started in flight?

Answer 8

NO

Question 9

What fuel pumps provide pressure for APU?

Answer 9

Main Tank 2 AFT AC PUMP - otherwise - Main Tank 2 DC *Main Tank 3 AFT AC PUMP prevents xfer and is a backup.

Question 10

APU gens and load?

Answer 10

• 2 gens - Capable of supplying entire load of A/C on ground - Not avail in flight

Question 11

What APU components are powered by APU battery?

Answer 11

• Inlet Door (Hot) - APU Primary Controller (Hot) - DC Fuel Pump (Main) - APU Fire Detection System (Main) (Fire - Fuel - Controller + Door)

Question 12

What APU components are powered by main battery?

Answer 12

• APU Fire Ext - APU Fuel Valve - APU Secondary Controller (Fire - Fuel - Controller)

Question 13

What happens if TR overheats with start source in TR?

Answer 13

Start power is transferred to the battery. Further attempts with overheated TR inhibited.

Question 14

How does TR failure affect APU starting?

Answer 14

Auto switching to APU battery is not provided. Moving start switch to BATTERY removes TR from start circuit and allows APU start on battery power.

Question 15

What happens if battery turned OFF before APU auto shutdown?

Answer 15

It will shut down immediately as the DC pump is de-energized. Remember, it’s on the APU MAIN BUS not APU HOT BUS.

Question 16

What happens if TR power is not available for an APU start?

Answer 16

The APU BATTERY will supply power for the APU Starter and ALL OTHER COMPONENTS are powered by the MAIN BATTERY while the APU starter is engaged.

Question 17

When is APU cool down cycle complete?

Answer 17

When fuel valve closes and APU decelerates.

Question 18

Is APU GEN power available during cool down cycle?

Answer 18

NO