Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cat B- Mod 11 Aircraft Systems > 11.4 Air Conditioning > Flashcards

11.4 Air Conditioning Flashcards

1
Q

How is the aircraft pressurised?

A

Engines
APU
Air Cart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do the outflow valves do?

A

Control the amount of air that goes out of the aircraft.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why do most pressurisation systems have a built in for cooling pressurised air?

A

So that air at any altitude can be cooled.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where is the bleed air typically taken from?

A

Compressor stage 5 and 9

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is air from the 5th stage considered?

A

Low pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When is low pressure bleed air used?

A

Take off, climb and cruise.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

When is high pressure bleed air used?

A

Low engine rpm speeds, during descent.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is bleed air pressure adjusted?

A

Pressure regulating valve (PRV) or bleed air valve (BAV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the independent cabin compressors designed to do?

A

Reduce the amount of bleed air required.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the three groups of cabin compressor?

A

Positive displacement
Centrifugal
Turbo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a positive displacement compressor also known as?

A

Roots type

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does a root type blower build pressure?

A

By supplying more air than the system needs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a centrifugal cabin compressor?

A

Fundamentally an air pump, air is compressed by an impeller.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do centrifugal compressors have a variable ratio drive for?

A

To offset engine fluctuations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does a turbo compressor system work?

A

Bleed air from the engine drives a turbine which in turn drives a compressor.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is a CAC?

A

Cabin air compressor.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How many phases is a CAC?

A

Three phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

When a ground air cart is not available, what can be used instead to supply high volume, high pressure starting air?

A

APU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What job has the greatest demand on an APU?

A

Supplying bleed air.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What three methods does an APU have of supplying bleed air?

A

Bleed air from the compressor
Bleed air from the load compressor
Bleed air from the two stage axial turbine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the limit of bleed air extraction on an APU?

A

22,000 feet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does the APU master switch do?

A

Primes and opens the flaps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is cart air pressure regulated too?

A

Normal pneumatic system pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is ACS?

A

Air conditioning system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is adiabatic?

A

Temperature change without the addition or removal of heat.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is conduction?

A

Transfer of heat from one object to another due to contact.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is radiation?

A

Transfer of energy without a medium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is convection?

A

Transfer of heat through a medium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is latent heat?

A

Causes a substance to change state without a change in temp.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is sensible heat?

A

When applied causes a temp change that can be sensed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is super heat?

A

Heat energy added to a gas after complete evaporation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What are basic gas laws?

A

Turbine- expands and cools
Compressor- squeezes and heats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What temp range are most ACS able to produce?

A

21 to 27 degrees c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What two types of ACS are there?

A

Air Cycle machine
Vapour Cycle machine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What ACS system is more common on turbine aircraft?

A

Air cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Where does hot bleed air first enter and at what pressure?

A

Primary Heat Exchanger
30-40psi @ 150c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

When ram air cools bleed air in the primary heat exchanger what is the temp drop?

A

100 degrees c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is the second section of the air cycle?

A

Travels to the compressor section, temp rises to approx 30-40 degrees c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is the third stage of the air cycle?

A

Passes through a turbine to cool by 60 degrees.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Water

What follows stage 3?

A

Water extractor, as the water is removed it enters the water collector.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is stage 4 of the air cycle?

A

Re-heater and into a condenser

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What does the air that flows across the condenser coming from the turbine do?

A

Lowers the dew point of the air into the water extractor to enlarge the water drops.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

How do water extractors extract?

A

Centrifugal force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What happens to the water extracted from the extractor?

A

It is used in spray nozzles for ram air, to improve cooling efficiency of heat exchangers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What is the purpose of the temperature control valve?

A

When there is ice build up etc in the system bleed air is bypassed from before the heat exchangers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

When is the air cycle machine at its minimum?

A

High altitude due to lower ambient temps, most of the bleed air only passes through the heat exchangers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What is the pack/flow control valve?

A

Valve that regulates bleed air from the pneumatic manifold.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What is another name for a pack/flow control valve?

A

Supply shut off valve.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What happens when an overheat is detected?

A

The pack/flow valve automatically shuts off.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What type of valve is the pack valve?

A

Venturi type butterfly valve.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What happens when the pack switch is operated?

A

The pack valve solenoid is de-energised and if there is bleed air available the valve opens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Due to fail-safe philosophy what does the pack valve do when electrics drop out?

A

Open

53
Q

What is the ICAO minimum airflow per person?

A

0.283m cubed

54
Q

What is the calculation to work out if an aircraft meets the ICAO standard airflow?

A

Convert volume flow to minutes by x60 then divide by max pax.

55
Q

What is volume flow measured in?

A

Seconds

56
Q

When the LO position is selected how much air is the pack supplying?

A

80%

57
Q

On the ground there is insufficient ram air to use in the heat exchanger, what is used to generate flow?

A

A fan

58
Q

What is a bootstrap system?

A

Transfer heat to the ram air, but majority is removed by expansion and converting into work.

59
Q

What are the two types of ACM?

A

Oil lubricated
Air lubricated

60
Q

What do slingers do in an oil ACM?

A

Pump oil mist into the bearings.

61
Q

What is the benefit of air lubricated ACM?

A

No oil contamination.

62
Q

What is the negatives of air lubricated ACM?

A

Noisy and require careful handling.

63
Q

What two functions does a reheater/condenser have?

A

Cool before water collection
Heat to help the turbine in ACM.

64
Q

What are trim air valves?

A

Used in some systems to mix conditioned air and provide accurate temp controlled air.

65
Q

What is the mix chamber?

A

The final part of the system in which the conditioned air is mixed with warm air and distributed to the desired areas.

66
Q

On the ECAM A/C temp colours meanings?

A

Green- Duct temps
White- Actual zone temp
Blue- Selected temps

67
Q

To increase ram air recovery what is used on the ram air exhaust?

A

Modulating vanes

68
Q

How does a vapour cycle machine act?

A

Moves hot air from the cabin to outside the cabin.

69
Q

What principle does a vapour cycle machine work on?

A

Vapour compression refrigeration cycle.

70
Q

How does the refrigeration cycle work?

A

Heat goes to the liquid, which turns to vapour as it gains heat. Vapour is then compressed which makes it very hot. Vapour goes outside cooling the air inside

71
Q

What happens to the boiling point if pressure is reduced?

A

Reduced

72
Q

What are refrigerants?

A

Chemical compounds that are alternately compressed and condensed into a liquid and then allowed to expand into a vapour.

73
Q

What is a refrigerant?

A

A working fluid that undergoes repeated phase transition from a liquid to a gas and back again.

74
Q

What is the compressor in a vapour cycle machine?

A

This component pressurizes the refrigerant gas, causing its temperature to rise significantly.

75
Q

What is the condensers role in the system?

A

Where the refrigerant releases heat to the external environment.

76
Q

What is the expansion valve?

A

The high-pressure liquid refrigerant passes through an expansion valve, causing it to rapidly expand and decrease in pressure. This results in a drop in temperature.

77
Q

What is the evaporator?

A

Inside the cabin, the low-pressure, low-temperature refrigerant evaporates, absorbing heat from the surrounding air.

78
Q

What happens at the receiver-dryer process?

A

Acts as a reservoir to store any of the liquid refrigerant.

79
Q

What is a commonly used refrigerant?

A

Dichlorodifluoromethane (R12)

80
Q

Why is R12 not used anymore?

A

It has an impact on the ozone.

81
Q

What has R12 been replaced with?

A

R134a

82
Q

What can result if R12 and R134a are mixed up?

A

Damage to components

83
Q

What is the boiling point of R134a?

A

-26 degrees c

84
Q

Why does the receiver-dryer have desiccant in it?

A

To capture any water in the fluid.

85
Q

What two problems does water in the refrigerant have?

A

Forms an acid
Could form ice

86
Q

How do you know if the system is low on refrigerant?

A

Bubbles on the sight glass.

87
Q

What does the expansion valve do?

A

Control the amount of refrigerant to make sure it is the amount that can be vapourised.

88
Q

What are most evaporators made of?

A

Copper or aluminium

89
Q

Why do evaporators have fins?

A

To increase surface area

90
Q

Vapour air cycle machines are closed systems, how is servicing carried out?

A

Two service valves, one on the high side and one on the low.

91
Q

What type of service valve is used on R12 systems?

A

Schrader valve

92
Q

In what position does a service valve allow the system to be worked on?

A

Intermediate

93
Q

Where does conditioned air enter and exit the cabin?

A

Ceiling vents into floor vents.

94
Q

What is gasper air?

A

Individual pax air

95
Q

Up to what altitude is the quantity of oxygen sufficient to support humans?

A

10,000 feet

96
Q

What equivalent altitude do aircraft pressurisation systems produce?

A

8000 feet or less

97
Q

At what height must pax be on emergency oxygen?

A

15,000 feet

98
Q

What is atmospheric pressure measured in?

A

Hectopascals

99
Q

What is 1013 hPa equal too?

A

14.7 psi

100
Q

What is the rate of change in temp in the troposhere?

A

-2 degrees c per 1000 feet

101
Q

What is cabin altitude?

A

Cabin pressure in terms of the equivalent above sea level.

102
Q

What is cabin differential pressure?

A

The difference between air pressure inside and outside the cabin.

103
Q

What is cabin rate of climb?

A

Rate of change of air pressure inside the cabin expressed in feet per minute.

104
Q

What 3 modes of cabin pressurisation are there?

A

Isobaric
Differential
Manual (Emergency)

105
Q

How does isobaric cabin mode work?

A

Maintain cabin altitude at a single pressure

106
Q

How does differential cabin pressure mode work?

A

Constant pressure difference between inside and outside

107
Q

What happens when isobaric mode is being used and the aircraft climbs beyond a certain altitude?

A

It automatically switches to differential mode.

108
Q

An increase in cabin altitude is?

A

A decrease in cabin pressure.

109
Q

What is a positive safety valve also known as?

A

Excessive differential pressure relief valve.

110
Q

What does a positive safety valve do?

A

Outwards pressure relief.

111
Q

When does a positive safety valve open?

A

Between 8 and 10psi over the maximum differential.

112
Q

What is the trigger point for a negative safety valve?

A

If the pressure outside the aircraft exceeds the inside by 0.5 to 1 psi

113
Q

When does a dump valve open?

A

When the aircon pack fails or emergency pressurisation is selected.

114
Q

What three pressure indications are there?

A

Cabin altimeter
Cabin rate of climb
Cabin differential

115
Q

On modern aircraft what page displays all the information?

A

ECS- Environmental control system

116
Q

When the aircraft is in auto, what happens as the aircraft takes off?

A

Switches from Ground to proportional control.

117
Q

When the aircraft is in auto, what happens as the aircraft reaches cruise?

A

Switch to isobaric

118
Q

What is the maximum permissible rate of change of cabin pressure?

A

0.16 psi/min (1500ft/min)

119
Q

During climb what is the rate of cabin climb?

A

500ft/min

120
Q

During descent what is the rate of cabin climb?

A

300ft/min

121
Q

When are system tests required?

A

Initial proof pressure test
AMM
System malfunction
After repairs

122
Q

What should a good leak detector be able to detect?

A

1/2 ounce of refrigerant a year

123
Q

What does a low pressure gauge read on a manifold set?

A

Up to 150psi

124
Q

What is the CWP?

A

Central Warning Panel, provides information on system status.

125
Q

What is a red indicating light?

A

Critical failure

126
Q

What is an amber indicating life?

A

Caution

127
Q

What is a green indicating light?

A

System is ready for operation

128
Q

What is a white/blue indicating light?

A

System is in use

Cat B- Mod 11 Aircraft Systems (28 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions