APU Flashcards

1
Q

Primary function of the APU

A

AC power via 30 KVA generator

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2
Q

What controls and monitors the APU

A

The ECU

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3
Q

How is flow of air controlled through the compressor

A

Variable Geometry Diffuser

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4
Q

What is the job of the VGD

A

prevents surges and stalls

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5
Q

What accessories mounted on the APU gearbox

A
  • AC Generator
  • Fuel Control Unit
  • Oil pumps
  • Oil cooling fan
  • DC starter motor
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6
Q

What is the screened duct for on the left side of the fuselage

A

Air is drawn in by the oil cooler fan for oil cooling and ventilation of the APU enclosure

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7
Q

How many pounds per hour does the APU burn

A

120 with electrical and bleed air loading

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8
Q

What controls fuel supply to the APU

A

The SOV

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9
Q

When does the APU SOV close

A
  • APU PWR FUEL switch
  • APU FIRE PUSH switch
  • Automatically when fire is detected
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10
Q

What happens when the APU PWR switch is pressed

A

DIGS

  • APU IN BITE self test (5sec)
  • RPM EGT Gauges displayed
  • Intake door opens
  • APU SOV OPEN status message
  • XFLOW/APU pump starts
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11
Q

When is starter motor de energized (START light goes out)

A

50% rpm

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12
Q

What does green AVAIL light indicate

A

APU is ready for bleed air loading, happens at after 4 seconds after RPM reaches 99%

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13
Q

Which battery is used for APU start

A

Main and the APU Battery
APU battery turns the APU Starter
Main Battery operates the ECU

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14
Q

What conditions will the APU shut down in flight

A
  • Fire
  • Slow Start
  • Overspeed
  • DC power loss
  • RPM signal loss
  • ECU Failure
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15
Q

What switch allows bleed air to be supplied to the 10th stage bleed air manifold

A

APU LCV on the Bleed Air Panel

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