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M15 vid > 15.18 > Flashcards

15.18 Flashcards

1
Q

What does the APU do?

A

Provide pneubleed air and electrical power for aircraft systems

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2
Q

The APU can be split up into three main sections

A

Power
Bleed
Accessory gearbox

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3
Q

What does the power section of the APU do?

A

Drive the compressor and the gearbox

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4
Q

What is the compressor called that provides sufficient bleed air to the pneumatic system

A

Load compressor

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5
Q

What type of compressor will you find on APU

A

Centrifugal flow compressor

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6
Q

On modern APUs the combustion chamber is what type

A

Annular type

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7
Q

What is the air pressure for the APU

A

30-45psi

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8
Q

What are the two methods of APU bleed air supply

A

Compressor of the the power section

Individual load compressor

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9
Q

The airflow into the load compressor can be controlled by what?

A

Variable inlet guide vanes

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10
Q

Why does the APU generator not need a constant speed drive when running as a back up

A

Because the APU is always controlled to a constant speed by the APU fuel control unit

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11
Q

Where is the APU compartment located

A

In aircraft tail sections

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12
Q

What does the APU equipment compartment house hold

A

Air intake actuator
APU fire extinguisher bottle
Fuel supply line
Bleed air duct

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13
Q

How many APU mounts are there to support the APU

A

3 one is fixed the other 2 are flexible

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14
Q

How many mounts transmit vertical loads and forces from the APU

A

2

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15
Q

How many mounts transmit lateral loads and forces from the APU

A

1

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16
Q

How many mounts transmit vertical loads and forces from the APU

A

All 3

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17
Q

What equipment is used to remove the APU

A

Hoist equipment

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18
Q

What is another name for the air intake door

A

Air intake flap

19
Q

What voltage is need to drive the APU air intake door actuator

A

28V DC power

20
Q

What does the APU inlet (diffuser) do?

A

Guides the air to the APU

21
Q

What does the APU air intake elbow do?

A

Forms the air duct between the air inlet duct and the APU air inlet

22
Q

What are the two types of drains

A

Direct and indirect

23
Q

What does the APU drain mast do

A

Collects the leakage and drains the fluid overboard during flight

24
Q

What two actions are needed to start the APU

A

Start initiation

Start activation

25
Q

What are the two APU control signals for constant speed control

A

APU speed signals

Torque motor signals

26
Q

How many ways can you turn off the APU

A

3 ways

27
Q

What is the cool down period of an APU

A

Between 0 and 120s

28
Q

How is automatic stut down of an APU activated

A

By the APU control unit

29
Q

What is the name of the primary fuel system of the APU

A

Low pressure fuel systems

30
Q

Where does the primary fuel system start and end

A

Starts at the fuel tanks and ends at the FCU of the APU

31
Q

Where does the secondary fuel system of the APU start and end

A

Starts at the FCU and ends at the fuel nozzle of the combustion chamber

32
Q

What are the sub-systems for the APU air system

A

Cooling air system and bleed air system

33
Q

What are the three main tasks of a bleed air system

A

Bleed supply
Surge procreation
Load compressor control

34
Q

Can a load compressor be switch off

A

No because it is fixed to the rotor shaft

35
Q

How can compressor surging be prevented

A

Bleeding off the air that is blocking the compressor discharge

36
Q

When would the surge control valve open

A

If the airflow behind the load compressor decrease or stops

37
Q

What are the two pressure pick ups in the surge protection system

A

Total pressure and static press

38
Q

What are the three types of supply pumps which can be used in the APU oil system

A

Gerotor type
Gear type
Vane type

39
Q

What pressure is the gearbox in the APU oil vent system pressurised to

A

4-5psi

40
Q

What does the APU starter lead do

A

Transmit the battery power to APU starter motor

41
Q

What type of motor is the starter motor

A

Brush type DC motor

42
Q

What are the three starter limitations for a APU battery

A

Duty time
Cool down time
Duty cycle

43
Q

The APU ignition system is usually powered by what?

A

DC

44
Q

What are the most important indication you will see during APU start

A

Battery voltage
Speed indication
EGT indication

M15 vid (15 decks)

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