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EGK Systems > Pneumatic Systems > Flashcards

Pneumatic Systems Flashcards

1
Q

Pneumatics System Uses on light and large AC

A

Light:
Power gyroscopes
Cabin heating and inflate de-icing boots

Large:
Cabin conditioning
Pressurisation
Ice protection
Bleed air to power pneumatic systems (reduces thrust)

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2
Q

Advantages of Pneumatic Systems

A

+ Air readily available and light
+ easy to generate compressed air using engine drive compressor
+ gas turbine have supply of bleed air system

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3
Q

Disadvantages of pneumatic systems

A

Bleed air reduces thrust and not efficient
Designers moving away from bleed air
Electrical systems replacing pneumatic systems

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4
Q

Light A/C pneumatic sources

A

Engine driven vacuum pump
Pump driven by the engine via quill drive shaft

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5
Q

Quill Shaft

A

Used on light A/C pneumatic systems to generate compressed air
Designed to shear if torque becomes excessive

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6
Q

Large A/C pneumatics air supplies

A

Bleed air from main engines
Compressed air from APU
Compressed air from ground power unit

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7
Q

GPU

A

Ground Power unit
Used to provide conditioning air before APU started
Can start engines with air starter mechanism

+ Save running APU and burning fuel

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8
Q

APU

A

Small turbojet at the rear of fuselage
Provide electrical power and compressed air when engines not running

Drives a compressor to generate air

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9
Q

Bleed Air

A

Generate large amounts of compressed air by tapping it from engine compressor

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10
Q

Problems with Bleed Air

A

Very high temp and pressure variations must be cooled before use

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11
Q

The Bleed Tapping

A

High pressure/low pressure pipelines from engine drawn through system.

High pressure line passes through high pressure shut off valve (HPSOV)

Route:
400psi (HPSOV) 100psi (PRSOV) 40psi

Then goes to the pre cooler

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12
Q

High pressure reducing shut off valve - pneumatics

A

Used to reduce high pressure aired from rear of engine from 400 psi down to 100 psi then onto the PRSOV

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13
Q

Pressure reducing shut off valve

A

Used to reduce pressure further from high pressure line and low pressure line from 100psi to 40 psi for pre cooler

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14
Q

How is air distributed around A/C

A

Ducts and shut off valves to control supply to different systems

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15
Q

Shut off Valves operations

A

Pneumatically operated and electrically controlled
Sensor detect position of valves and pressure and relay to flight deck

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16
Q

Duct Construction

A

Stainless steel for high temp/pressure ducts
Light alloy for mid temp/pressure ducts
Plastic/fibreglass for low temp/pressure ducts

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17
Q

Overheat detection and warning in pneumatic systems

A

Overheat detection loops location in all sensitive areas
Can be operated with one loop inoperative for limited time
Must detect a hot gas leak within 0.3 metres

18
Q

Zones/Loops in Pneumatic system

A

Used for heat detection systems
Two loops for every zone
One loop needed for flight ops minimum

19
Q

Light AC air conditioning

A

Hot air form heat exchanger around exhaust mixed with cold air ram air system

20
Q

Air conditioning requirements CS25

A

1lb of fresh air per minute per seat
0.5lb of fresh air per minute per set in emergency
Temp between 18/24 degrees
Co2 not to exceed 1/20000

21
Q

ECS

A

Environmental control system collective name for components required for conditioning and pressurisation

22
Q

Bootstrap system in operation

A

Air moves from engine compressor to pre cooler
Passed onto the cooling pacts
Ducted to pacts via isolation valve
Passed to primary heat exchanger in ram air duct
Move toward temperature control valve (bypasses or goes through compressor)
Compressor to secondary heat exchanger
Condensed air extracted to ram air
Passed through turbine for further cooling then warmed with bypass air
Off to the cabin

23
Q

Mixing Valve Role

A

Controls hot bleed air allowed to bypass the cold air unit

Temperature control valve or mixing valve

24
Q

Bootstrap system - Cold Air Unit

A

Combined compressor/turbine in the conditioning pack

25
Q

Water Seperator

A

Located downstream and extracts moisture from the air and dumps it in ram air duct

26
Q

Ram Inlet role

A

Control airflow to heat exchanger
NACA ducts on the sides of aircraft’s

27
Q

Pressure Ducts role

A

Located under floor and circulate air up the side of fuselage and up above then flows back down and picked up by recirculation fan

28
Q

Why do we have pressurisation controls

A

Control minimum cabin pressure
Control max differential pressure
Control max rate of change in cabin pressure

29
Q

What is cabin altitude

A

The cabin pressure usually limited to 8000ft

30
Q

Negative relief valve

A

Let’s pressure into the AC if outside has a higher pressure

31
Q

Role of pressure controller

A

Maintains required differential pressure (we set destination QNH)

32
Q

Outflow Valves

A

Allow pressure to be past to atmosphere from the inside

33
Q

Safety Valves

A

Protect from over pressurisation if outflow valves do not operate
0.5psi above max differential pressure they will open

34
Q

Dump Valve

A

Manually operated valve to dump pressure in emergency
Important for emergency landings to get the doors open

35
Q

Ground Pressurisation

A

Slight pressurisation before take off to smooth out variation and help the pressurisation controller

36
Q

Isobaric Range

A

Constant maintained pressure between discharge from outflow and the inflow of air

37
Q

3 types of decompression

A

Normal - 6 to 10 seconds
Rapid - 4 to 6 seconds
Explosive - 0 to 3 seconds

38
Q

Excess cabin altitude warnings x3

A

10,000ft - visual and aural warning
14,000ft - oxygen masks drop

39
Q

Rate of change of cabin pressure is known as

A

Cabin vertical speed

40
Q

Ground cooling fan

A

Draw air through the ram air duct when the aircraft is stationary to ensure heat exchangers are kept cool

EGK Systems (15 decks)

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