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Mod 11 > 11.4 - Air Conditioning and Pressurisation > Flashcards

11.4 - Air Conditioning and Pressurisation Flashcards

1
Q

How does the ozone converter work

A

Catalytic reaction

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2
Q

How does coalescer-type water separators work

A

By encouraging the water to form large droplets that can be centrifuged out

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3
Q

In which part of the vapour cycle machine is the heat energy discharged to the atmosphere

A

Condenser

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4
Q

Which is true for an aircraft that is on the ground and pressurisation is in the ground mode

A

Outflow valves commanded to the fully open position

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5
Q

How is the pressure in an aircraft cabin regulated

A

By the outflow valves regulating the amount of air leaving the cabin

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6
Q

What happens in the pressurisation system at aircraft touchdown

A

The cabin pressure controllers swap rolls and the outflow valves are driven to the fully open position

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7
Q

What happens in the event of excess cabin positive pressure

A

Safety valves open to bleed away pressure

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8
Q

What happens when cabin is at 15000ft

A

The outflow valves are completely closed independent of the normal control system

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9
Q

Which circuit defends the air on system from the duct overheat in the event of component failure or mis control in manual mode

A

The protection circuits of the zone temperature control system

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10
Q

Which condition of air is ideal for a pneumatic system

A

Air at constant pressure and temperature

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11
Q

In which condition is the air arriving at the air conditioning packs normally

A

Approximately 200c at 45psi

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12
Q

Considering the very low temperature of the air leaving the air cycle machine. How is it possible to prevent water from freezing in the system

A

A water separator is located upstream of the cooling pack

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13
Q

How is the quantity of air entering the cabin regulated

A

By the pack valve

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14
Q

Which climb mode of pressurisation is usually more comfortable for passengers

A

External mode

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15
Q

Which devices are installed to prevent damage to the structure in the event of sudden depressurisation of the aircraft

A

Equalisation valves allow pressure in various zones to equalise

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16
Q

How is ozone in the air supplied in the air conditioning system treated

A

Ozone converter incorporates a catalyst that converts ozone to harmless oxygen

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17
Q

What is the purpose of the bleed valve

A

To regulate engine bleed air supply

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18
Q

Which statement is true regarding cabin pressure controllers

A

There are 2 controllers, 1 active and 1 standby

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19
Q

From what do the cabin pressurisation systems safety devices protect the fuselage structure

A

From high positive and negative delta p

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20
Q

What cabin pressure is the cabin raised too during cabin pressure leak checks

A

Approximately 4psi

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21
Q

How many different air sources can be used to supply the air conditioning system in flight

A

2

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22
Q

What is the alternative source of the air conditioning system should engine bleed air become available during flight

A

APU

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23
Q

Why is there a requirement for the ventilation of the temperature sensors in the cabin zone

A

The ventilation delivers the cabin air to the sensor

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24
Q

What components does an air cycle machine comprise

A

A compressor, a turbine and a heat exchanger

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25
Q

Why would an OUTFLOW valve have 2 AC motor and 1 DC motor

A

Each pressure controller can control its own AC motor and if AC is not available the DC motor can control the valve

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26
Q

During a cabin pressure leakage test, why must all instructions be adhered to

A

Injury to personnel inside the cabin could occur as well as damage to pressure sensitive components

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27
Q

What circuit controls air conditioning ducts from potential overheat conditions

A

The protection circuit

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28
Q

What will occur if the cabin depressurises

A

The flight crew are warned to put on their oxygen masks

29
Q

How does an air cycle machine cool the pneumatic flow

A

The air is cooled by one or more heat exchangers and the turbine which are operated by ram air

30
Q

What is the purpose of a turbine bypass valve in the pack

A

It controls the mass of air flowing to the pack

31
Q

What is the cabin altitude

A

The pressure inside the cabin in relation to sea level pressure

32
Q

What is the purpose of the emergency Ram Air Inlet

A

It supplies fresh ambient air to the mixing unit when all packs fail in flight

33
Q

If ice has built up in the condenser or the exit of the turbine, how is it cleared

A

Some air is bypassed around the heat exchangers and the air cycle machine though a temperature control valve and melts the ice

34
Q

What type of valve is the pack valve

A

Venturi type

35
Q

How is the pack valve operated

A

Electronically opened, spring loaded to close

36
Q

How is the pack vale shut off function controlled

A

Fire handle, during engine start and from the pack switch

37
Q

What is the minimum volumetric flow allowed per person by the ICAO regulations into the cabin

A

0.283m3/min

38
Q

What are the two types of Air Cycle Machine

A

Oil lubricated and air lubricated

39
Q

What operation does the Trim Air Valve perform

A

They control the bleed air directly fed into the mixing chamber

40
Q

Wheat happens to the ram air doors during flight

A

They modulate to reduce both the ram air flow and drag

41
Q

What are the components of a Vapour Cycle Machine

A

The refrigerant, the compressor, the condenser, the expansion valve and the Evaporator

42
Q

What refrigerant has replaced R12

A

Tetrafluoroethane (R134a) which is classed as safer for the environment

43
Q

Can R12 and R134a be mixed

A

No, nor can one be used in a system designed for the other

44
Q

Where is the condenser in the system

A

Located downstream of the condenser and upstream of the expansion valve

45
Q

What is inside the receiver dryer

A

Filters and desiccant material

46
Q

How does air get into the evaporator

A

The evaporator is situated in such a way that cabin air is pulled into it by a fan

47
Q

What drives the compressor

A

Modern compressors are either engine driven or driven by an electric motor

48
Q

What are cabin temperature pick up units and duct temperature sensors

A

Thermistors

49
Q

What is the temperature selector

A

A rheostat

50
Q

In the venturi system, where does the humidifier get its water supply

A

Potable water supply

51
Q

How much air normally filtered and recirculated

A

Up to 50%

52
Q

Where is the cabin air normally exhausted from

A

Most aircraft this exhaust is extracted from the lower compartments after of the wings by outflow valves and fwd of the wings by the recirculation fans

53
Q

Cabin pressurisation systems are designed to produce conditions of how many ft?

A

Approximately 8000ft or less

54
Q

At what cabin altitude must people use oxygen

A

Flight crew 10,000ft
Passengers 15,000ft

55
Q

Why do the regulations limit the maximum cabin altitude during flight to 8000ft

A

A compromise between acceptable environmental conditions and the structural stress applied to the fuselage

56
Q

What is atmosphere pressure at sea level

A

1 atm
14.7 psi
29.92 Hg
1013.2 hPa
1013.2 mb
760 mm Hg

57
Q

What is the rate of change in temperature with altitude in the troposphere

A

-2’C for every 1000 ft

58
Q

What are the different modes of operation for cabin pressurisation

A

Isobaric mode - maintains altitude as set by aircrew
Differential - maintains cabin pressure to a constant pressure difference with ambient
Manual - used for trouble shooting

59
Q

When in isobaric mode, what happens if the aircraft climbs beyond a certain altitude and maintains the cabin altitude selected my result in a differential pressure above what the fuselage was designed

A

Switches from isobaric to differential mode

60
Q

What is the normal cabin pressure rate of change

A

Normal climb - 500 fpm
Normal descending - 300 fpm

61
Q

When do cabin safety valves open

A

When pressure differential is between 8 and 10 psi approximately

62
Q

When do negative differential pressure valves open

A

When the outside pressure exceeds the inside by 0.5 - 1.0 psi

63
Q

Can you release refrigerant into the atmosphere

A

R12 is illegal to release
R134a is illegal in some countries

64
Q

What are the health implications of inhalation of R134a

A

Inhalation of high quantities of R134a vapour may cause cardiac irregularities, unconsciousness and death

65
Q

What gauges are on the manifold

A

Low pressure 0 -150 psi with blue hose
High pressure 0 - 500 psi with red hose

66
Q

How much pressure is required for a leak check

A

About 50psi

67
Q

What are the normal pressures in the system

A

Low pressure 10 - 50 psi
High pressure 125 - 250 psi

68
Q

How is bleed air leak monitored

A

Flight deck gauges
Overheat detection located near the ducts
Bleed are monitoring system detect loss of pressure

69
Q

What would cause the pack overheat warning to be displayed

A

Outlet temp of more than 260c or outlet temp of more than 230c four times in one flight

Mod 11 (21 decks)

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