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Module 13 EASA Part 1 > 13.18 Pneumatic/Vacuum > Flashcards

13.18 Pneumatic/Vacuum Flashcards

1
Q

What are the advantages of pneumatic systems?

A

Lightweight
Safe
Reliable
Eco–friendly
Small (can be)
Unaffected by atmospheric changes
Inexpensive components
Pressure seals are usually problem free
Forces transmitted are easy to manage (within acceptable PSI limits)

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2
Q

What is caused by increasing the pressure of a volume of air, and what is therefore required in a compressor?

A

Increasing pressure causes an increase in temperature

Cooling fins on the compressor

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3
Q

How does a compressor increase the pressure of the air?

A

Volume of each successive stage is smaller than the preceding one

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4
Q

What stage of air is exhausted to atmosphere when the pressure regulator is open?

A

Third stage air

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5
Q

What encourages the air to spin in a oil and water trap?

A

Radial drillings

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6
Q

In a pneumatic system, what component is used to remove the last of the oil and water from the system?

A

Dehydrator

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7
Q

What is contained in the dehydrator which will remove oil and water from the air?

A

Dessicant – Activated alumina

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8
Q

What should be carried out if moisture is found in the air filter housing?

A

Oil and water trap should be examined for faults

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9
Q

What are commonly used as filters in the pneumatic system filters?

A

Paper gauze
Glass wool
Felt
Fine metal mesh

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10
Q

How are air storage cylinders usually mounted?

A

In the upright position

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11
Q

How is the operating pressure of a relief valve changed?

A

Adjustable by means of increasing or decreasing spring pressure

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12
Q

How does a pressure maintaining valve operate?

A

Allows pressure to primary/essential systems as well as secondary/non–essential systems

At a loss of pressure, shuts off pressure to secondary/non–essential

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13
Q

What might a pressure maintaining valve also be called?

A

Priority or pressure regulating valve

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14
Q

In a pneumatic actuator, how is damping achieved?

A

Forcing grease through an annular space between the inner wall of the piston rod and a stationary damper piston

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15
Q

What might air extracted from gas turbine engines also be known as?

A

Charge air

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16
Q

What might charge air be used for?

A

Cabin air conditioning and pressurisation
Anti–icing
Drinking water pressurisation
Hydraulic reservoir pressurisation

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17
Q

In an engine air bleed pneumatic system, what is the main supply of compressed air provided by?

A

Low pressure/intermediate stages of the engine compressor

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18
Q

In an engine air bleed pneumatic system, what happens under reduced power settings?

A

High stage valve will open to allow the high–pressure compressor to satisfy the demands of the user system

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19
Q

In an engine air bleed pneumatic system, what does the distribution system do?

A

Interconnects the engine bleeds and the bleed from the APU

Contains all the necessary valves to shut off bleed air at each engine and isolates various ducts

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20
Q

Where does some of the hot air from the low/intermediate stage compressor go?

A

Forward to the engine cowling anti–icing system if selected

21
Q

When will a pressure relief valve open in the duct coming from the low/intermediate stage compressor?

A

If the duct pressure exceeds 100 lb/in²

22
Q

In an engine air bleed pneumatic system, what are the four functions of the Pressure Regulator and Shut–off Valve?

A

Opens or closes in response to the control switch on the bleed air control panel in the crew compartment, or when temperature and pressure limits are exceeded (will also close when the engine fire handle is operated to arm the extinguisher circuit)

Prevents reverse flow when duct pressure exceeds engine supply pressure

Modulates to limit pressure in the pneumatic manifold to approximately 45 lb/in²

Limits temperature to 230 °C

23
Q

In an engine air bleed pneumatic system, what is the pre–cooler also known as, and what temperature does it cool bleed air to?

A

200°C to 230 °C

24
Q

In an engine air bleed pneumatic system, how does a pre–cooler cool the bleed air?

A

Uses cold air from the engine fan

25
Q

In an engine air bleed pneumatic system, what happens to the fan air which is used to cool bleed air in the pre–cooler?

A

Discharged to atmosphere after passing through the cooler matrix

26
Q

In an engine air bleed pneumatic system, how is the amount of cooling air from the fan controlled?

A

By the pre–cooler control valve

27
Q

What delineates the air conditioning system from the bleed air system?

A

Pack valve

28
Q

At what RPM will the APU bleed valve open to supply air to the pneumatic system?

A

95%

29
Q

In an engine air bleed pneumatic system, what are the three positions of the isolation valve?

A

Close
Open
Auto

30
Q

In an engine air bleed pneumatic system, what position is the isolation valve in when ‘auto’ is selected and all engine bleed air and air conditioning packs are operating?

A

Closed

31
Q

Under what conditions will the APU bleed valve close automatically, even if the APU is running at 95% or above RPM?

A

APU fire–warning switch is operated to arm the fire extinguisher

32
Q

What must all external supplies, whether from high pressure storage cylinders or mobile compressors, be fitted with to ensure that the air is clean and dry?

A

Oil and water traps

Preferably a dyhydrator

33
Q

How are you to check for leaks of a pneumatic system?

A

Not using hands

Strips of cloth placed on a rod
or
Special leak detection liquids

34
Q

What are the three conditions which usually apply to duct maintenance and repair?

A

Smooth dents are normally permissible providing they do not restrict the flow of air through the duct

Shallow scratches and gouges are permissible if they are not more than 10% of duct wall thickness, and providing the bottom of the scratch is smooth

Any defect or damage within approximately 1/4 (6mm) of a weld renders the duct unserviceable and it should be replaced”

35
Q

What is the system identification label for:

Fuel
Pneumatic
Lubrication
Hydraulic

A

Fuel – four pointed star
Pneumatic – no–matic
Lubrication – black square
Hydraulic – black circle

36
Q

What is the maximum pressure supplied through the pneumatic ground service connection?

A

40 – 45 lb/in²

37
Q

How does a pneumatic ground service connection prevent loss of air through the connection during normal operation of the aeroplane bleed air system?

A

One way valve

38
Q

What is the pressure in the potable water system provided by engine bleed air?

A

10 – 15 lb/in²

39
Q

In an engine air bleed pneumatic system, how does the pre–cooler control valve work?

A

Oil filled sensing element which operates a push rod

When normal temperature is reached, the oil expands and a ball is unseated by the push rod

Valve opens, increasing the flow of cooling air from the fan

40
Q

What are the two basic types of air pumps?

A

Wet and dry

41
Q

What component vents third stage air pressure to atmosphere in a pneumatic system?

A

Pressure regulator

42
Q

What is the main disadvantage of pneumatic power generation?

A

Loud
Compressible fluid
Difficult to control position

43
Q

In order, what are the components in a typical high pressure system up to the service selector valve?

A

Compressor (pumps)
Oil and water trap
Dehydrator
Air filter
Air storage cylinder
Pressure relief valve
Pressure reducing valve
Pressure maintaining valve
Isolation valve

44
Q

What happens when duct temperature reaches 230°C?

A

Atmospheric port is opened

Reducing control air pressure at the bleed air regulator

Regulator and shut–off valve move towards the closed position

Reduces the amount of bleed air passing through the pre–cooler

Less hot bleed air flowing, the pre–cooler will cool it more efficiently

45
Q

What will happen when the bleed air over temp switch operates?

A

At 255°C

Warning light on the bleed air control panel will illuminate

Closes the pressure regulator and shut–off valve

46
Q

What is the purpose of the check valve?

A

Prevents reverse flow from the high pressure stage

47
Q

What happens when duct pressure exceeds 100 psi?

A

Pressure relief valve will open

48
Q

APU air is selected but no air services are operating, state the potential cause?

A

APU is running below 95 rpm

Module 13 EASA Part 1 (20 decks)

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