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M15 New > 15.18 > Flashcards

15.18 Flashcards

1
Q

What is the apu

A

Small gas turbine (free) turbo shaft engine

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2
Q

What does the apu supply

A

Pneumatic bleed air and electrical power

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3
Q

What does the apu supply

A

Pneumatic bleed air and electrical power

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4
Q

What does the apu do on ground

A

Allow aircraft to operate without ground support equipment

Primary source of bleed air for engine starting

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5
Q

Where is the apu located

A

Unpressised fireproof compartment in the rear fuselage tail cone

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6
Q

How do you require an ETOPS certification

A

Have an inflight APU

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7
Q

Apu starting altitude

A

15-17k ft

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8
Q

Apu operation altitude

A

Up to 40k

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9
Q

Why are apus started in landing phase

A

Unloads main engine pneumatic burden

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10
Q

3 parts of apu

A

Power

Bleed

Accessory gearbox

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11
Q

Order of operation of the apu

A

Power drives compressor and gearbox

Gearbox drives apu accessories

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12
Q

Power section of GTE

A

Compressor

Combustion chamber

Turbine

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13
Q

What does the electrical control box do (ECB)

A

Start sequence

Turbine sped

EGT

oil and fuel supply

Bleed air outlet

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14
Q

What generator is used in the apu

A

AC

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15
Q

What does normal speed mode do

A

Keeps the apu at 100% regardless of load changes

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16
Q

Why does the apu monitor acceleration

A

Optimize apu start

Protect the apu from damage

17
Q

What correlation does bleed load have with EGT

A

Opening the bleed valve increases bleed load which increases APU EGT

18
Q

What is apu cooldown period

A

0-120 seconds

19
Q

How many pressure switches in the primary apply fuel system

A

Minimum of one

20
Q

What does the positive fuel pressure in the apu fuel feed line do

A

Prevent cavitation at the high pressure fuel pump of the APU

21
Q

What does the cooling system do

A

Supply air to the oil cooler and apu ventilation

22
Q

What 2 things must be done in order for the apu bleed valve to open

A

Apu bleed Switch selected on

Apu start sequence compete

23
Q

What’s an advantage of an apu having a load compressor

A

Makes it more fuel efficient

24
Q

3 parts of the load compressor

A

Variable inlet guide vanes

Inlet guide vane actuator

Apu control unit

25
Q

When is the anti-surge system used

A

On apus without a load compressor

26
Q

How does a anti surge system work

A

Anti surge valve bleeds air off when surging is possible

27
Q

When does the surge control valve open

A

Airflow behind the load compressor decreases or stops

28
Q

When is an automatic apu emergency shutdown activated

A

When fire condition occurs while aircraft is on the ground

29
Q

What’s the quickest way to shut down the apu

A

Activate the fire switch

30
Q

What signals are used by the apu to control a constant speed

A

Speed signal and torque motor signal

M15 New (18 decks)

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