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M11 > 11.4 > Flashcards

11.4 Flashcards

1
Q

Whats the 3 thing which provide the aircraft with pressurised air ?

A

Engines
APU
Ground source

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2
Q

What part of the engine takes in air to pressurise the cabin ?

A

Compressor

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3
Q

Whats the three types of compressors ?

A

Positive displacement compressor
Centrifugal compressor
Turbo compressor

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4
Q

How is air pressure adjusted ?

A

Pressure regulating valve or
Bleed air valve

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5
Q

When is low pressure air used ?

A

During take-off climb and cruise.
( high pressure bleed air is used at low engine RPM speeds during decent )

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6
Q

What lowers the hot air which is bled from the engine ?

A

Pneumatic system

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7
Q

What happens to the engines power when air is bled from the compressor ?

A

Power will drop
( this decreases the engine efficiency as the compressor is resulted to work harder )
- individual cabin compressors are designed to minimise the disadvantages which follow from bleeding the air from the engines compressor )

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8
Q

Explain a positive displacement blower ?

A

Two rotors rotate at the same speed in which air travels around the outside of the case and is deposited.

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9
Q

Explain centrifugal cabin compressor ?

A

Takes air from atmosphere into a supercharger, where it is compressed by the high-speed impeller and delivered to a distribution

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10
Q

What does the supercharger have in a centrifugal cabin compressor which produces optimal airflow regardless of the engine speed ?

A

Variable - ratio drive

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11
Q

How does the turbo compressor work ?

A

Bleed air from engine drives a turbine, which directly drives a compressor. Hot air produced is blended with cooled decompressed bleed air.

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12
Q

What is the cabin air compressor powered by ?

A

Three-phase motor

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13
Q

What does the APU compressor supply ?

A

Bleed air to a load compressor

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14
Q

If the APU is designed to provide bleed air extraction in flight, what altitude is the bleed air extraction normally limited to ?

A

22,000 ft

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15
Q

Whats the two APU outputs ?

A

Electrical
Pneumatic ( compressed air )

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16
Q

What does a ground cart air supply consist of to supply air ?

A

Small jet engine inside soundproof steel unit which carry’s conditioned air through ducks from the pack where it is required on the aircraft.

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17
Q

Whats the two types of air conditioning systems used on aircraft ?

A

Air cycle machine - used on large aircraft
Vapour cycle machine - used on small aircraft

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18
Q

Whats the two types of air conditioning systems used on aircraft ?

A

Air cycle machine
Vapour cycle machine

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19
Q

Whats the range that an air conditioning system is capable of maintaining ?

A

21 - 27 degrees

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20
Q

Whats the use of a pack ?

A

To drop air down to around 0 degrees

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21
Q

What two things are found in an air con pack ?

A

Heat exchanges
Air cycle machine

22
Q

How is conditioned air distributed to the cabin ?

A

Trough ducts
( conditioned exits through ceiling vents where it circulates )

23
Q

What are distribution ducts constructed of?

A

Light fibreglass coated to prevent moisture damage
( ducts must be able to expand and shrink without loss of the pressure tight properties )

24
Q

Where are temperature monitoring valves located ?

A

Electronics compartment

25
Q

Whats a thermistor ?

A

Resistor that changes with its exposure to heat and has a shut off control.
( its not a on/off switch. It’s resistant changes as temperature changes )

26
Q

What do on board humidifiers do ?

A

Help passengers stay hydrated

27
Q

How much of the cabin air is filtered and recirculated ?

A

50%
( this means engines only need to supply the other 50% of cabin air which saves fuel )

28
Q

When the air is supplied to cabin and circulates around, how is it discharged out of the cabin ?

A

Through air grilles located on the sidewalls near the floor.

29
Q

*Cannot mix r12 And r134a

A
30
Q

Whats a gaspo fan ?

A

Air conditioning outlet in the cabin

31
Q

What fan is found in packs ?

A

ACU fans

32
Q

Above what altitude does there be a lack of oxygen and cabin pressurisation be needed ?

A

Above 10,000 ft

33
Q

What happens to the outside pressure as the altitude increases ?

A

It decreases

34
Q

What high is the cabin pressure when at cruise ?

A

8,000 ft

35
Q

How much is 1 atm in psi and Hecto pascal ?

A

14.7 psi
1013.2 hPa

36
Q

In the terms of passenger comfort, why do we pressurise the cabin ?

A

Depressurised cabin would make it have for passengers to breathe

37
Q

Whats hypoxia ?

A

Becoming unconscious due to a depressurised cabin.

38
Q

Whats the airframe subjected to when the aircraft’s being pressurised in a high altitude ?

A

Differential pressure
Calculation- (cabin psi - outside psi)

39
Q

Whats the maximum anticipated loads called ?

A

Limit load
( limit load x safety factor = ultimate load )

40
Q

Whats cabin altitude ?

A

Cabin pressure inside of aircraft in terms of altitude above sea level.
( Normally maintained around 8,000 ft )

41
Q

How is the cabin pressurisation controlled in light ?

A

Through an outflow valve which regulates the amount of air that flows out of the cabin. This is controlled from the flight deck.

42
Q

If cabin altitude increases, what happens to the cabin pressure ?

A

It decreases.

43
Q

If you want to increase cabin pressure, should the outflow valve be open or closed ?

A

Closed.

44
Q

Whats the three pressurisation mode ?

A

Isobaric mode - maintains cabin altitude no matter the altitude change.
Differential mode. - maintains cabin pressure
Manual mode ( emergency ) - used if isobaric control is faulty so it controls cabin pressure manually.

45
Q

Explain a positive safety valve ?

A

Outwards pressure relief valve fitted to relive positive pressure in cabin when maximum pressure differential is exceeded.
( if its exceeded by 8 - 10 psi )

46
Q

Explain a negative safety valve

A

Inwards relief valve which is fitted to prevent excessive negative differential pressure which will open if pressure outside the aircraft exceeds that inside the aircraft by 0.5 - 1 psi.
( allows air to enter cabin )
- to much air entering can cause difficulties opening the cabin door or structural damage.

47
Q

Explain the leak detector methods for air conditioning ?

A
  1. Held close to component with a hose connection and an audible and visual alarm will signal.
  2. Apply soapy solution to fittings and inspect for bubbles.
  3. Injecting special leak detection dyes.
48
Q

How do you find cabin differential pressure ?

A

Inside cabin pressure - outside ( ambient ) pressure

49
Q

Explain he difference between a positive and negative negative safety pressure valve ?

A

Positive - opens outwards
- let’s excessive differential pressure out of
Cabin.
Negative - opens inwards
- allows ambient air to enter cabin

50
Q

Whats a dump valve used for ?

A

Quickly remove air from the cabin and operates automatically or by a switch in the flight deck.

51
Q

What is used to allow the flight crew to warn about a bleed air leak or monitor the systems function ?

A

Flight deck gauges
Overheat detectors
Bleed air monitoring systems

M11 (22 decks)

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