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A320 Systems > APU > Flashcards

APU Flashcards

1
Q

How is the APU started?

A
  • Aircraft batteries
  • External power source
  • Normal aircraft AC power
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2
Q

What is the main function of the Auxiliary Power Unit (APU)?

A

It is a self-contained unit that supplies the aircraft with:

PNEUMATIC and ELECTRICAL power

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3
Q

What does the APU provide during on-ground operations?

A
  • supplies bleed air for starting the engines
  • supplies air-conditioning
  • supplies electrical power
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4
Q

What does the APU provide during takeoff?

A
  • Supplies bleed air for air conditioning (for example, when optimum aircraft performance is required)

[APU bleed ON during takeoff]
*computation is packs OFF but PACK 1 and 2 pb still ON

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5
Q

What does the APU provide in-flight?

A

‐ It backs up the electrical system

  • It backs up the air conditioning
  • It can be used to start the engines
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6
Q

What is the basic element of an APU engine?

A

A SINGLE-SHAFT gas turbine that delivers mechanical shaft power for:

  • Driving the accessory gearbox (electrical generator, starter, etc.)
  • Produces bleed air (engine starting and pneumatic supply)
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7
Q

The basic element of an APU engine is a SINGLE-SHAFT gas turbine the delivers power for:

A
  • Driving the accessory gearbox (electrical generator, starter, etc.)
  • Produces bleed air (engine starting and pneumatic supply)
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8
Q

Is a full-authority digital electronic controller that performs the bulk of the APU system logic for all modes of engine operation:

A

Electronic Control Box (ECB)

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9
Q

What is an ECB?

A

Electronic Control Box

A full-authority digital electronic controller that performs the bulk of the APU system logic for all modes of engine operation

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10
Q

What does the Electronic Control Box (ECB) provide for the APU system?

A

Performs the bulk of the APU system logic for all modes of engine operation, such as:

  • Sequences the start and monitors it
  • Monitors speed and temperature
  • Monitors bleed air
  • Sequences the shutdown
  • Controls the automatic shutdown
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11
Q

This allows external air to reach the compressor inlet of the APU:

A

APU air inlet flap

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12
Q

Where is the APU air intake flap located?

A

At the bottom of the tail cone, beneath the APU compartment

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13
Q

What controls the APU starter?

A

The ECB (Electronic Control Box)

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14
Q

When does the APU starter engage?

A
  • When the APU MASTER switch and START pb is switched ON

and

  • When the APU intake flap is FULLY OPEN
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15
Q

When the APU MASTER switch and START pb is switched on, what else is needed in order for the APU starter to engage?

A

APU air inlet flap fully open

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16
Q

Where is the APU located?

A

In the unpressurized tail cone

16
Q

After the APU MASTER sw has been turned ON, the ECB will not allow an APU start until:

A

The APU air inlet flap is fully open

18
Q

What are the two (2) things needed in order for the APU starter to engage?

A
  • APU MASTER switch and START pb ON

- APU air inlet flap fully OPEN

19
Q

When the APU MASTER switch and START pb is switched ON with the APU air inlet flap still fully closed, will the APU starter engage?

A

NO.

The APU air inlet flap MUST be FULLY OPEN

(Together with the APU MASTER switch and START pb ON)

20
Q

The APU fuel system is normally supplied from?

A

The LEFT fuel feed line.

The required pressure is normally available from the tank pumps

21
Q

What happens if the required pressure from the left fuel feed line is not available (batteries only or pumps off)?

A

The APU FUEL PUMP starts automatically

22
Q

When does the APU FUEL PUMP turn ON?

A

Provided that the APU MASTER sw is ON:

It starts AUTOMATICALLY when the required pressure from the fuel feed line is not available.

The ECB controls the fuel flow.

22
Q

When does the APU Fuel pump operate?

A

If no fuel tank pump is running

23
Q

The APU bleed air system is fully automatic. True or False?

A

True

26
Q

The flight crew uses the controls on the APU panel for routine shutdown. What are other controls can be used in case of an emergency shutdown?

A
  • The flight crew can use the APU FIRE pb (cockpit)

- The ground crew can use the APU SHUT OFF pb on the inter-phone panel under the nose fuselage

27
Q

What happens with an APU fire on-ground?

A
  • The APU fire warning operates
  • A horn in the nose gear bay sounds
  • The AVAIL light goes out
  • The APU MASTER sw FAULT lt comes ON
  • The APU shuts down
  • The APU fire bottle discharges
28
Q

During an APU Manual shutdown sequence, if the aircraft was using APU bleed air, the APU keeps running for a cooling period of how long?

A

60 to 120 seconds

29
Q

When does the APU Master switch amber light come on?

A

When an APU automatic shutdown occurs

30
Q

What happens during an APU automatic shutdown?

A

Depending of the version of the ECB:

  • The amber fault light comes ON
  • A caution appears on ECAM
31
Q

An automatic APU shutdown occurs in case of:

Name three causes

A
  • Fire (On-ground only)
  • Air inlet flap closed
  • Overspeed
  • No acceleration
  • Slow start
  • EGT overtemperature
  • No flame
  • Reverse flow
  • Low oil pressure
  • High oil temperature
  • DC power lost (BAT OFF when aircraft on batteries only)
  • Overcurrent Sensor failure
  • IGV failure
  • ECB failure
  • No speed
  • Underspeed
  • Loss of overspeed protection
  • Oil system shutdown
  • Inlet overheat
  • Clogged oil filter
  • Loss of EGT thermocouples
32
Q

What does an amber fault light on the APU Master sw pb indicate?

A

An APU auto shutdown has occured

33
Q

During the APU cool down period, can the APU be turned back on?

A

Yes. As long as it is within the 60 to 120 second cool down period, and the AVAIL light is still on, the APU MASTER sw can be turned back ON.

34
Q

During an APU start sequence, when does the green AVAIL lt come on (on the START pb)?

A

When N is above 99.5 % or 2 s after N reaches 95%

35
Q

After the APU has been started and is on speed (95% N) the green AVAIL light appears in which three locations?

A
  1. APU Start pb
  2. ECAM APU System page on the SD
  3. E/WD memo section
36
Q

What happens during an APU fire in flight?

A

The flight crew must manually shutdown the APU by pressing the APU Fire pb and manually discharge the fire bottle/agent.

37
Q

What is different about an APU start using the aircraft batteries?

A

Nothing. Everything is the same except that the APU System page does not appear on the ECAM SD page.

38
Q

When the APU Bleed Valve is open and supplying bleed air, the APU AVAIL line on the ECAM memo is replaced with what line/message?

A

APU BLEED

39
Q

Can the APU be started and operated even if the LOW OIL LEVEL ECAM advisory is displayed?

A

Yes. If there is no oil leak, then the remaining oil quantity allows normal APU operation for about 10 hours. (Ref: ECAM Advisory conditions)

Maintenance action is required within 10 hours of APU operation.

A320 Systems (3 decks)

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