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NATOPS > APU > Flashcards

APU Flashcards

1
Q

What is the APU starting altitude envelope?

A

-1000 to 20,000 ft

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2
Q

What degree does the APU air intake door open on the ground? in flight?

A

35 15

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3
Q

What does the Auxiliary Start Relay on the APU do?

A

acts as a holding relay until the APU reaches 50%, then it is de-energized

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4
Q

Fuel for the APU comes from where and how does it get there?

A

Gravity fed from Tank 2

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5
Q

How much fuel must be in tank 2 IOT feed the APU without turning the boost pumps on?

A

2000 lbs

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6
Q

What does external power supply power to?

A

LH/RH AC bus, essential AC bus, and main AC bus which in turn powers the avionics buses and all four regulated TRs

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7
Q

What is the reset position for the APU generator?

A

OFF on the external/APU switch

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8
Q

When the External power/APU switch is placed to APU, what does it power?

A

connects the APU generator to the essential AC bus

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9
Q

What is powered if the APU is the only source of power?

A

essential and main AC buses

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10
Q

When does the start light on the APU go out?

A

until the APU compressor reaches 50 percent rpm

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11
Q

An ESS DC BUS OVERLOAD ACAWS message may appear during APU starts. No maintenance is required unless what?

A

unless a TR and/or other bus fail ACAWS message also appear

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12
Q

The APU has to warm up for how long without a bleed air load?

A

1 minute

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13
Q

What is the starter duty cycle?

A

1 minute ON, 4 minutes OFF

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14
Q

How long is the APU door operation?

A

9-18 seconds

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15
Q

How long from APU start light to on speed?

A

35 seconds

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16
Q

Normal APU rpm

A

98-105 percent

17
Q

Max APU rpm

A

110 percent

18
Q

Normal APU EGT

A

260-680 C

19
Q

Max APU EGT and for how long?

A

710 C for 3 seconds maximum

20
Q

What is the general purpose of the APU?

A

supplies air for ground operation of the AC systems and for engine starting provides shaft power to drive a 40-kVA AC generator

21
Q

When is the APU fuel and ignition circuits energized?

A

when APU oil pressure rises above approx. 4 psi

22
Q

When does the APU automatically shut down?

A

APU speed exceeds 110% oil pressure is low tachometer fails

23
Q

How is the APU maintained at a constant speed of 100%?

A

the speed-sensing governor controls it by regulating fuel flow into the combustion chamber

24
Q

What supplies APU starting control power?

A

isolated DC bus

25
Q

What supplies power to the APU start motor?

A

the essential DC bus (if the essential DC bus is powered) and the utility battery

26
Q

What should you do if the APU does not light off during ground start in extreme cold weather?

A

preheat the APU with an external source of heat prior to second start attempt

27
Q

What occurs when the APU oil subsystem senses low oil pressure?

A

APU automatically shuts down

NATOPS (14 decks)

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