APU Flashcards

1
Q

Fuel to start and operate the APU comes from ?

A

The left side manifold when the AC fuel pumps are operating.

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2
Q

The APU fuel boost pump is (blank) operated to ensure ?

A

DC operated to ensure positive fuel pressure to the APU fuel control unit

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3
Q

When does the APU fuel boost pump operate ?

A

It operates during start and operation automatically when the APU fuel control unit senses low fuel pressure

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4
Q

When does the APU fuel boost pump turn off

A

The APU automatically shuts off when the an AC fuel pump pressurizes the fuel manifold

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5
Q

If the AC and DC fuel pump are not operating how does the APU get fuel

A

If the AC and DC fuel pump are not operating fuel is suction fed from the no.1 tank.

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6
Q

APU engine air routes from where?

A

An automatically operated air inlet door located on the right side of the fuselage.

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7
Q

How is the APU cooled?

A

Air for APU cooling enters through a cooling air inlet above the APU exhaust outlet. This air circulates through the APU compartment, passes through the oil cooler and vents through the exhaust outlet.

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8
Q

Requirements to start the APU

A
  • APU fire switch on the overheat/fire panel must be In
  • APU fire control handle on the APU ground control panel must be in
  • Battery switch must be on
  • Electrically power from the #1 AC transfer bus or the battery bus is used to start the APU
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9
Q

APU start sequence

A

APU switch to start > initiates opening of the air inlet door > When APU inlet door full open start sequence begins > Once APU reaches proper speed, ignition / fuel provided > When the APU is ready to accept bleed air / electrical load the APU GEN OFF BUS light illuminates

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10
Q

How long can it take for the APU to start ?

A

120 seconds

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11
Q

automatic shutdown protection of the APU occurs if ?

A

If EGT is exceeded, overspeed conditions, low oil pressure, high oil temp, APU fire, fuel control unit failure

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12
Q

Moving the APU switch to OFF begins what sequence for shutdown

A

trips the APU gen > closes the bleed air valve > extinguishes the APU GEN OFF BUS light > shutdown occurs after 60 seconds > when the APU speed decreases the fuel valve and inlet door close > if the fuel valve does not close the FAULT light will illuminate

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