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M15 GTE > APU > Flashcards

APU Flashcards

1
Q

How many apu mounts

A

3

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2
Q

What loads do the 3 mounts transmit

A

Vertical loads and forces from the apu to the aircraft structure

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3
Q

What loads do 2 mounts carry

A

Transmit Axial loads and forces from apu to aircraft structure

flexible to allow limited movement for thermal expansion

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4
Q

What loads do 1 mount carry

A

Carries lateral loads and is always a fixed mount for strength and stability

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5
Q

What’s the purpose of the apu

A

Supplies pneumatic bleed air and electrical power

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6
Q

How is the apu removed

A

Using a fish pole hoist

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7
Q

How do u hold the apu once removed

A

Support stand

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8
Q

Where do we mainly use the apu

A

On ground

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9
Q

What are the 3 parts of the apu

A

Power

Bleed

Accessory

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10
Q

What does the bleed system do

A

Make sure sufficient bleed air is supplied to the aircraft pneumatic system

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11
Q

Where’s the apu intake on airbus

A

Lower intake door

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12
Q

Where is intake in Boeing

A

Right hand upper side of fuselage

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13
Q

What does apu intake door do

A

Supplies air to the apu and it closes off the apu air inlet if apu isn’t running

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14
Q

How is inlet door operated

A

Electrical actuator supplied from 28v DC

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15
Q

Air pressure for bleed air

A

30-45psi

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16
Q

What’s another name for the apu air inlet duct and why

A

Diffuser due to its shape , it guides air to the apu

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17
Q

What do the air inlet guide vanes do

A

Improve the airflow

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18
Q

Where are the inlet guide vanes

A

In the air intake elbow

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19
Q

What does the apu drain system do

A

Catch and drain fluids and leakages

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20
Q

Why is apu drain system necessary

A

Prevents fire operating malfunctions and corrosion

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21
Q

Where do u find condensed water

A

Apu exhaust section after apu shut down is cooled

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22
Q

Where does Oil or fuel leakage come from

A

come from the drive seals at the apu gear box

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23
Q

What are the two types of drains

A

Direct and indirect

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24
Q

What’s a direct drain

A

Catch fluids and drain them via drain lines directly overboard

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25
Q

What’s an indirect drain

A

Catch fluids the put into a tank which is connected to a drain mast

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26
Q

How does the drain mast work

A

Airflow at the drain mast causes suction to the suction line

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27
Q

What does the apu supply the ac generator with

A

Constant speed

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28
Q

What does normal speed mode do

A

Keeps apu at constant 100%

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29
Q

What does start mode do

A

Control apu from start activation until its at 100%

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30
Q

How is start mode activated

A

Manually by switches on the overhead panel in the cockpit

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31
Q

How many apu switch in Boeing

A

One switch

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32
Q

What are the two individual switches used on airbus

A

Master switch and start switch

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33
Q

What’s necessary to start the apu

A

Start initiation and start activation

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34
Q

What does start initiation mean

A

Electrical power is supplied to the APU control unit

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35
Q

What happens when master switch is on

A

Apu control unit is supplied with electrical power and first performs a pre start test

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36
Q

when does apu inlet door open

A

When pre start test is successfully performed

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37
Q

What does the speed indicator and EGT indicator show when air inlet door is open

A

Zero

38
Q

What two signals are used for constant speed control

A

Apu speed signal and torque motor signal

39
Q

How does normal operation keep a constant speed

A

By comparing the actual apu speed with thr necessary speed

40
Q

How does the toque motor signal work

A

If speed is not 100% it will change the fuel metering

41
Q

How do you shut down apu

A

Normal

Automatic

Emergency

42
Q

How is apu normal shut down

A

Via master switch

43
Q

How does apu automatic shut down

A

Triggered by apu if it detects any malfunctions in important comments

44
Q

How does apu shut down in emergency

A

By fire switch or alternate emergency shut down switch

45
Q

What is the apu cool down period on normal shut down

A

Varies between 0 and 120s

46
Q

How does apu shut down after cool down

A

Control unit closes off fuel supply to the combustion chamber so apu comes to a stop

47
Q

How quick is automatic shut down command activated

A

Imminently without any cool down period

48
Q

Does emergency apu shut down have a cool down period

A

No

49
Q

How is apu fire extinguished

A

By a special fire extinguishing system

50
Q

Where does fuel come from for the apu

A

Aircraft main engine engine fuel feed system

51
Q

What does apu fuel shut off valve do

A

Serves as an isolation valve for the apu fuel feed line

52
Q

What does the pressure switch in primary apu system do

A

Monitors fuel pressure in the apu fuel feed like directly infront of apu and triggers warming if there’s a fire

53
Q

What does the second pressure switch do

A

Controls apu fuel boost pump

54
Q

What is the apu fuel boost pump used for

A

Give positive fuel supply if tank boost pumps not available

55
Q

What’s does pushing the vent push button do

A

Apu fuel boost pump is started and the apu fuel shut off valve opens

56
Q

What’s the two sub system of apu air system

A

Cooling and bleed

57
Q

What can the bleed air system be split into

A

Bleed supply

Surge protection

Load compressor control if apu has one

58
Q

What does load compressor system do

A

Reduces fuel consumption of the apu

59
Q

What happens when only
One power source is needed in load compressor control

A

The other one is shut off , when apu
Bleed if off EGT decreases

60
Q

Can the load compressor be switched off

A

No it’s fixed to rotor shaft

61
Q

What do the variable inlet guide vanes do in the load compressor

A

Control quantity of airflow into the load compressor & can move to any position between open and closed

62
Q

How are inlet guide vanes moved

A

By inlet guide vane actuator

63
Q

How can compressor surge be prevented

A

Bleeding off the air blocking the compressor discharge

64
Q

Where are anti-surge systems installed

A

Apus without load compressors

65
Q

Why is anti sure system not efficient

A

Air is bled off when there is no surging

66
Q

Where is surge protection used

A

Apus with load compressors

67
Q

How does surge protection work

A

Monitors the airflow in the load compressor discharge duct and opens a surge control valve is surge occurs

68
Q

Where is airflow sensor installed

A

Discharge duct of the load compressor

69
Q

What are the discharge duct pressure pick ups

A

Total pressure pick up and static pressure pick up

70
Q

What’s the relationship between airflow in the compressor discharge duct and pressure

A

Airflow is equal to the difference in total pressure and static pressure

71
Q

Where does the apu cooling system supply air to

A

Apu cases

Apu compartment

Apu oil cooler

72
Q

What’s does the de-oiling valve do

A

Improve apu start sequence and on many Apus the oil system is used cool apu generator

73
Q

Where is the oil resovoir

A

Lowest part of the apu gearbox

74
Q

What type of pump is an apu oil supply pump

A

Positive displacement pump

75
Q

How are Apus with load compressors fuel efficient

A

They can be switched off if bleed load is not required by the aircraft

76
Q

What an advantage to apu with a load compressor

A

EGT limits aren’t reached which Improves lifetime of the apu

77
Q

How is airflow into load compressor controlled

A

Variable inlet guide vanes

78
Q

What are variable inlet guide vanes

A

Work as a modulating and shut off valve

79
Q

Where does electrical power supply come from

A

Generators driven via apu gearbox

80
Q

Why does apu not need a constant speed drive

A

Controlled to a constant speed by apu fuel control unit

81
Q

What supplies electrical power to to the apu to do the power up test

A

Master switch

82
Q

What type is the starter motor

A

Brush type DC motor

83
Q

What do brush wear indicators show

A

Show if brushes on the starter motor are worn via small inspection windows

84
Q

What do electrical brush wear sensors do

A

Electrically signal the control unit when worn on newer Apus

85
Q

When is starter relay energised

A

When apu start switch is activated

86
Q

What happens at starter cut off speed

A

Apu control unit opens starter relay

87
Q

What happens when starter relay opens

A

Disconnects battery from the apu starter motor

88
Q

What must you do after an apu start

A

Cool down sufficiently before you can use them again

89
Q

What are the 3 starter limitations

A

Starter duty time

Starter cool down time

Starter duty cycle

90
Q

Battery voltage check

A

Must be more then 23v

91
Q

What shows apu starter is accelerating the apu

A

Decrease in voltage during apu start

92
Q

What’s the quickest time to shut down the apu

A

Activate the fire switch

M15 GTE (19 decks)

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