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Module 11 Richard > 11.4 Air Conditioning And Pressurisation > Flashcards

11.4 Air Conditioning And Pressurisation Flashcards

1
Q

What do pneumatic systems deal with on aircraft

A

They deal with compressed or pressurised gas as a source of power.

Typically the gas used is air

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2
Q

On aircraft what would pneumatic power or energy be used for

A

Engine starting, cabin pressurisation, air conditioning, wing de-icing, water reservoirs and hydraulic reservoir pressurisation

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3
Q

What two variables need to be as constant as possible in a pneumatic system to support the different consumers effectively

A

Pressure and temperature

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4
Q

What is the main air source on jet aircraft

A

The engine compressor provides enough air for combustion purposes and also the pneumatic system

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5
Q

What is compressed air which has come from the engines called?

A

Bleed air

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6
Q

When on the ground the aircraft can be supplied by external air.
How would it be delivered

A

Via high pressure ground connectors

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7
Q

As the engines thrust varies what is needed to keep a constant pressure for the pneumatic consumers

A

A pressure regulator

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8
Q

What is the engine pressure regulator also known as

A

The bleed valve

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9
Q

What is used to protect the HP compressor from back flow when it bleeds air

A

A check valve

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10
Q

What type of valves are used for APU bleed air supply

A

No pressure regulator valve is needed but a shut off valve called the APU bleed valve is used to provide or shut off bleed air from the APU.

A check valve is also used to prevent back pressure

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11
Q

What is used to cool bleed air from the engines

A

A pre cooler

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12
Q

Where does the air for the pre cooler come from?

A

A duct directly from the fan air

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13
Q

What is used to allow more or restrict the amount of fan air to pass the pre cooler

A

A fan air valve

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14
Q

What is used to connect all engines bleed air and APU bleed air

A

Cross Bleed manifold

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15
Q

What is used to isolate left to right wing ducts on the manifold

A

A cross bleed valve

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16
Q

How do the pneumatic ducts detect leaking

A

They are monitored by a leak detection system

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17
Q

How would you control the pneumatic system or users

A

Manually via pneumatic control panel in the cockpit or automatically via the pneumatic controller

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18
Q

What is a pneumatic controller

A

To monitor pressure and temperature, detect leaks and monitor the operation of pneumatic components

There is one per engine

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19
Q

What condition would you be effected from if you climbed to high altitude in an aircraft which is unpressurisedk

A

You would be affected by Hypoxia

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20
Q

In passenger aircraft what is the purpose of cabin pressurisation

A

Keeping passengers comfortable

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21
Q

What does pressure differential mean

A

The difference in pressure between cabin/cockpit and outside of the aircraft

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22
Q

What provides pressurisation to the cabin, flight deck, cargo and avionics compartments

A

The air conditioning system

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23
Q

What main areas are not pressurised

A

Landing gear bays, the radomes and tail cone

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24
Q

Can different aircraft zones be heated individually heated

A

Yes

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25
Q

What 5 things must the air con system ensure that air is ?

A
  • Fresh
  • Clean
  • At a comfortable temperature
  • At the correct humidity
  • At the correct pressure
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26
Q

What are the regulation relating to freshness on board

A

Regulations say on average ad acceptable amount of fresh air supplied should be 0.283 cubic meters per person per minute

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27
Q

According to regulations how often should air be exchanged

A

3-5 mins

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28
Q

What are used to keep air clean and safe

A

Air filters and ozone converters

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29
Q

What is the comfortable temperature range for air temp

A

18-30 degrees Celsius

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30
Q

What temperature air holds more water warm or cold

A

Warm

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31
Q

What two things is pressurisation a compromise between

A

Passenger comfort and structural strength

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32
Q

What are cabins usually pressurised to

A

8000ft

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33
Q

What is the cabin pressure regulated by

A

Outflow valves

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34
Q

The temperature of air delivered to the zones is regulated in two steps, what are they

A

Pack controllers control the temperature the air leaves the pack and zone controllers regulate the amount of trim air is mixed with the cold air

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35
Q

Where are the pack and zone controllers located

A

The avionics compartment

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36
Q

What are the 3 types of cooling device on an aircraft

A
  • Heat exchanger
  • Vapour cycle machine
  • Air cycle machine
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37
Q

What process is heat exchanged in a heat exchanger

A

Conduction

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38
Q

When are vapour cycle machines used

A

When bleed air is not available

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39
Q

What type of aircraft would you find a vapour cycle machine

A

Small propeller aircraft, aircraft with out APU or older aircraft

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40
Q

What is a pack valve and what is it also known as

A

A flow control valve. It is spring operated and determines how much air goes into the cabin

It is also known as pack flow control valve or FCV

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41
Q

What must ALWAYS be done before you put on the pack switch

A

Follow a checklist

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42
Q

What is the density of air at 8000ft

A

0.96 kg/m3

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43
Q

What is the most efficient ways air con systems save energy

A

By adjusting the airflow to the number of consumers

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44
Q

When the pack selector is selected to normal what % of airflow is the cabin receiving

A

100%

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45
Q

When the pack selector is in the high position what % of air is being delivered to the cabin

A

More than 100%

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46
Q

When the pack selector is in the LO position what % of air is the cabin receiving

A

80%

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47
Q

What is the main advantage of the two heat exchangers being mounted together

A

Only one cooling duct is necessary

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48
Q

What are the 3 main components of the air cycle machine

A
  • Compressor
  • Turbine
  • Fan
49
Q

How is the air cycle machine lubricated

A

There is no need for lubrication as it uses air bearings

50
Q

What are air cycle machines also known as

A

Boot strap air cycle machines

51
Q

How can you adjust the temperature in the pack

A

By using the turbine bypass valve built in

52
Q

What is a turbine bypass valve also called

A

Temperature control valve

53
Q

How is the turbine bypass valve operated

A

Always electrically

54
Q

What type of valve is the turbine bypass valve

A

A butterfly type with a manual override which also operates as a position indicator

55
Q

What is ram air used for

A

It is used as cooling air

56
Q

What are the ram air inlets and outlets called

A

RAI (ram air inlet) and ram air exit

57
Q

What type of inlet is the ram air inlet

A

NACA type

58
Q

Why would a fan be needed in the ram air system

A

The fan is located on the common shaft of the turbine and the compressor

The fan is used on the ground as there is no ram air effect

As it is on the common shaft, if the packs are on the fan is turning

59
Q

Why must water be removed from the air con system

A

As temperatures can fall as low as -50 could cause freezing and damage

60
Q

Where does water separating occur

A

The water separator in the cooling pack

61
Q

What are the two ways water can be separated

A

High pressure loop or low pressure loop

Depending on manufacturer

62
Q

What is the purpose of the jet pump

A

It sprays the condensed water into the ram air inlet duct. This condensed water increases the cooling efficiency of the heat exchanger

63
Q

What causes the droplets to collect in the drain sump of the water separator

A

Centrifugal force

64
Q

In a high pressure loop what is used to detect icing of the condenser

A

Differential pressure and anti ice valve

65
Q

How many pack controllers does an air con pack have

A

1 main and 1 redundancy

66
Q

What are the 3 minimum required sensors in a pack

A
  • Compressor discharge temperature sensor
  • Pack discharge temperature sensor
  • Compressor overheat switch
67
Q

What does the pack controller monitor

A

The pack flow control valve position and sends it to the EICAS or ECAM indication

68
Q

How is the ram air inlet door measured

A

With limit switches and a position potentiometer

69
Q

How is optimum pack outlet temperature achieved

A

It is achieved by the pack controller modulating the bypass valve, the ram inlet door and the ram outlet door

70
Q

In flight, for maximum cooling, what is the position of the ram inlet doors and the bypass valve

A

Ram air doors are open and the bypass valve is fully closed

71
Q

What are the 3 examples of failures that occur in a pack

A
  • Controller failure
  • Compressor overheat
  • Bypass valve failure
72
Q

If the compressor overheat sensor detects a temperature which is close to overheat what would be done to increase cooling

A

The ram air doors would be opened further

73
Q

Would type of message would indicate in the cockpit as a result of an overheat

A

A FAULT on the pack switch, they pilot would have to turn off the pack and use the backup pack

74
Q

Where does the treated cold air go after the packs have done their job

A

A mixing unit which distributes it to the aircrafts different zones

75
Q

What is another term for a mixing unit

A

Plenum chamber

76
Q

What is mixed in the mixer unit

A

Fresh air from the packs and discharged cabin air

77
Q

What is the passengers individual air supply system called

A

The gasper system

78
Q

What is the system called that is carried out by the mixer unit. (Mixing fresh pack air with discharged cabin air)

A

The recirculation system

79
Q

What is the purpose of the recirculation fans

A

The fans suck discharged cabin air from under the floor area, clean it with filters and feed it into the mixing unit

80
Q

How would you get conditioned air on the ground if the packs are not used

A

You can supply conditioned air directly to the mixing unit via a ground connector port

81
Q

If all packs fail in flight what would be done to ensure that the passengers would still have air to breathe

A

Open the emergency ram air inlet.

It has an electrical actuator that extends the inlet flap into the ambient airflow

82
Q

What parameters can affect cabin temperature

A
  • The ambient temperature
  • Radiation from the sun
  • Cabin insulation
  • Heat from equipment
  • Heat from passengers
  • Temperature and rate that air is supplied to the cabin
83
Q

To allow for individual control of all zone temperatures what is required

A

A trim air system

84
Q

What is the purpose of pack valves

A

They are flow control and shut off valves

85
Q

With regards to automatic temperature control, what’s is the name of the computer that controls the temperature for that zone

A

The zone controller

86
Q

What is the ‘Anticipator’

A

a special temperature rate sensor found in some circuits

87
Q

What protects the system from duct overheat in the event of manual mode or component malfunctions

A

The protection circuits

88
Q

What type of sensors are used in the temperature zone system

A

Thermistor type

89
Q

What must be done for the sensors to read the temperature accurately

A

They must be ventilated, usually done by an electrical fan

90
Q

What are the typical indications on an air conditioning page in the flight deck

A
  • Actual cabin temperature
  • Actual duct temperature
  • Actual trim air valve position
91
Q

On the control panel what button is used to reset the trim air system

A

HOT air

92
Q

What are the main ventilation systems on aircraft

A
  • For galleys and lavatories (remove humid and stale air)
  • Cargo compartments (used especially when carrying live cargo)

There is also a separate system for equipment cooling

93
Q

What 4 subcategories does cargo ventilation fall in to

A
  • Non ventilated cargo
  • Ventilated and heated cargo
  • Ventilated and unseated cargo
  • Air conditioned cargo
94
Q

What happens to the air in a ventilated cargo compartment

A

It travels through exit grills and through the cargo hold. The air is then extracted by fans and dumped overboard by outflow valves

95
Q

In a ventilated cargo compartment what must be done in the case of a fire

A

Two motor operated isolation valves must close to prevent airflow and starve the fire

96
Q

What are the two methods of heating a heated and ventilated cargo bay

A
  • Bleed air

- Electric heater

97
Q

What are the two temperature selections that can be made for a heated cargo bay

A

7 degrees or 21 degrees

98
Q

What would happen if an overheat in a cargo compartment occurs

A

An overheat circuit is activated and the light on the heat cargo aft button will illuminate arming the extinguishers

99
Q

Where does the air come from for the air conditioned cargo bay

A

Most comes from the cabin through an inlet isolation valve

100
Q

What removes air from the galleys and lavatories

A

Extraction fans

101
Q

For equipment cooling valves are used to carry air flow what would happen in the case of smoke

A

Extra valves are opened and an override valve

102
Q

When pressurising the cabin what rate or pressurisation and depressurisation should the aircraft not exceed

A

Positive cabin rate should not exceed 500ft/min

Negative cabin rate should not exceed 300ft/min

103
Q

Protection functions must become active when when there is an excess in cabin altitude or excessive differential pressure.

What 3 things must happen at different altitudes

A

> At 10,000ft - Flight crew gets a warning to put on oxygen masks

> At 14,000ft - Oxygen masks automatically deploy in the cabin

> At 15,000ft - The outflow valves must close automatically

104
Q

What are the positive pressure relief valves for

A

To prevent structural stress on the aircraft. The re must be 2 safety valves and they are usually located on the aft pressure bulkhead

105
Q

What is used to prevent pressure differences in cargo bay areas

A

Spring loaded flapper valves will open at a predetermined value

106
Q

What are the 3 modes that the pressurisation of the aircraft works on

A
  • Automatic
  • Semi automatic
  • Manual
107
Q

What is the main input that is required when in semi automatic mode (Pressurisation)

A

The landing field elevation must be entered manually

108
Q

When would you have to select manual pressurisation mode

A

When both pressure controllers fail in flight.

Manual mode will require manually controlling outflow valves with a toggle switch

109
Q

What is the ditching button used for

A

To isolate the cabin from water entering during an emergency landing on sea (outflow valves close)

110
Q

What position are the outflow valves when the aircraft is on the ground

A

Fully open to avoid accidental cabin pressurisation

The equipment cooling valves are also open

111
Q

What controls cabin pressurisation in automatic mode

A

The cabin pressure controller

112
Q

When the aircraft leaves the ground what activates ground mode

A

Air ground logic

113
Q

In inertial climb mode the cabin controller calculates the cabin rate in proportion with aircraft altitude ( so they go up linear together I.e when at 40,000ft the max cabin altitude is reached on 8,000ft). What is this mode also called

A

Proportional mode

114
Q

What mode of pressurisation is more comfortable for passengers

A

The external climb mode

The external climb mode controller calculates a smooth and constant cabin rate

115
Q

After touchdown, which is detected by the ground air logic the controller switches back to ground mode, what should also happen

A

Outflow valves should go to fully open

116
Q

In aircraft with 2 cabin pressure controllers what should happen to them after every flight

A

They swap roles. The primary becomes the standby and vice versa

117
Q

How many forms of power do the outflow valves have

A

2 AC and 1 DC

When pressure controller one is primary it will use AC1
When pressure controller 2 is primary it will use AC2

When selected to manual DC is used to ensure power is available in emergency

118
Q

Before carrying out a cabin pressure leakage test what must be done

A

To prevent damage pressure sensitive equipment must be removed I.e computers with pressure ports, oxygen regulators and masks, sensitive pressure switches, fluid tanks like water tanks and auxiliary fuel tanks

119
Q

When doing a cabin pressurisation leak test what ATA chapter in the AMM must be read

A

Chapter 5

Module 11 Richard (19 decks)

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