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M15 > M15.18 > Flashcards

M15.18 Flashcards

1
Q

What type of engine is the APU?

A

A small gas turbine engine

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2
Q

What does the APU supply?

A

Bleed air and electrical power

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3
Q

When would the APU be used?

A

When you don’t need the engines

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4
Q

On very large APU’s what may you find two of?

A

AC generators on the gearbox

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5
Q

What does the power section drive on a APU?

A

The compressor and the gearbox

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6
Q

Will you find on an APU to make sure that the bleed air is sufficient?

A

A separate compressor usually called the load compressor

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7
Q

What is the compressor of the power section mainly used for on an APU?

A

Provide air for the combustion and bleed air

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8
Q

What type of compressors are found in an APU?

A

Centrifugal flow compressors

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9
Q

Why are centrifugal flow compressors used?

A

Good performance, long lifetime, resistant against FOD

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10
Q

What type of combustion chambers are used on APUs?

A

Annular (new) or can-type (old)

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11
Q

What type of turbine will you find on a small APU?

A

Centrifugal turbines

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12
Q

What type of turbines are found on large APUs?

A

Axial turbines with two or more stages

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13
Q

What pressure is the air pressure at that comes from the APU?

A

30-45psi

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14
Q

What are the two different ways a APU supplies bleed air?

A
  • a compressor from the power section

- an individual load compressor

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15
Q

Why are load compressors very fuel efficient on an APU?

A

Because the load compressor can be switched off if bleed air isn’t needed

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16
Q

Why would the APU need to supply electrical power?

A

As a back-up source for the aircraft

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17
Q

Where does the electrical power supply come form on an APU?

A

From generators which are driven via the APU gearbox

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18
Q

How many generators will you find on a large APU?

A

2

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19
Q

What are the APU doors for?

A

Servicing and maintenance

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20
Q

How many support mounts are there on the APU?

A

3

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21
Q

What are the names of the support mounts on an APU?

A
  • right aft mount
  • left aft mount
  • Forward mount
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22
Q

When would APU mount links be used?

A

On large aircraft

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23
Q

Why is one of the APU support mounts fixed in place?

A

For strength and stupidity

24
Q

How is the APU removed and refitted?

A

By using hoist equipment commonly know as fish pole hoist

25
Q

What is the air intake door of an APU also called?

A

Air intake flap

26
Q

How many volts is used to operate the APU intake door?

A

28volts DC

27
Q

What is the APU air inlet duct often named?

A

A diffuser

28
Q

What are the two types of drains on an APU?

A
  • direct drains: drained directly overboard

- indirect drains: drained to a drain tank

29
Q

The electronic APU control unit controls the APU automatically by using three operating modes, what are these?

A
  • start mode: controls start to 100%
  • normal speed mode: keeps it at 100%
  • shut down mode: controls shut down
30
Q

Where would you find emergency shut down switches for the APU?

A

Anywhere easy accessible for ground personal so landing gear areas

31
Q

What is the primary fuel system of the APU also known as?

A

Low pressure fuel system

32
Q

Where does the primary fuel system (low pressure fuel system) start and finish on a APU?

A

Starts at the fuel tank and finish’s at the fuel control unit

33
Q

What is the secondary fuel system of the APU also known as?

A

High pressure fuel system

34
Q

Where does the secondary fuel system (high pressure fuel system) start and finish on a APU?

A

Starts at the fuel control unit and ends at he fuel nozzles of the combustion chamber

35
Q

Where is the APU fuel boost pump and shut off valve normally located?

A

The left hand side main wheel well

36
Q

What is the job of the APU fuel shut off valve?

A

To shut off fuel supply to the APU if its not running

37
Q

What is the APU fuel line vent switch used for?

A

To bypass the APU master switch which allows for easy maintanence

38
Q

What is the APU air system divided into?

A

Cooling air and bleed air

39
Q

How can compressor surging be prevented in an APU?

A

By bleeding off the air that is blocking the compressor discharge

40
Q

Why does the APU oil system have a de-oiling valve?

A

Helps to improve the APU start sequence

41
Q

What is the APU oil system used to cool?

A

The APU generator

42
Q

Where is the APU oil reservoir located?

A

The lower part of the APU gearbox

43
Q

What does the APU oil supply pump do?

A

Supplies oil to the lubrication areas

44
Q

What are the three types of APU oil system pumps?

A
  • gerotor pump
  • gear pump
  • vane pump
45
Q

How does the air/oil separator work?

A

By using rotating action

46
Q

What pressures can the APU gearbox be pressured to?

A

4-5psi

47
Q

When would the APU gearbox need to be pressurised?

A

When operating at high altitudes

48
Q

What is the advantage of pressurising the gearbox of the APU?

A

It supports oil supply and minimises oil foaming

49
Q

Where is the APU start relay installed?

A

The electronic equipment compartment

50
Q

What type of motors start up the APU?

A

DC motors (usually a brush type)

51
Q

What are brushwear indicators used for?

A

To show how worn the brushes are on the start motor

52
Q

Why must you wait for the APU starter motor and battery to cool down?

A

Because they get very hot from the APU start

53
Q

Why are starter limitations in place on the APU?

A

It makes sure that the starter equipment does not get over stressed and overheated

54
Q

What is the APU ignition system usually powered by?

A

DC power that comes from the APU control unit

55
Q

What does the ignition exciter convert low DC voltage to?

A

High voltage for igniter plugs

56
Q

Where would you find the battery voltage in the cockpit?

A

Next to the battery switches

57
Q

When do the indications on the ECAM come available?

A

When AC power is switched on

M15 (15 decks)

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