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Module 11 Richard > 11.11 Hydraulics > Flashcards

11.11 Hydraulics Flashcards

1
Q

What ATA chapter number is hydraulics?

A

ATA 29

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2
Q

What is the unit for pressure

A

Pascal or NM

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3
Q

What is hydraulic pressure measured in?

A

Bar

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4
Q

What is 1 bar in psi

A

14.5psi

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5
Q

What pressure do most civil aircraft operate at?

A

3000psi or 207 bar

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6
Q

What sort of pressure does the A380 operate at?

A

5080psi or 350 bar

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7
Q

Why do aircraft like the A380 increase the pressure in their system rather than stick to 3000psi

A

To generate the required force with out having to increase the size of hydraulic components

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8
Q

What is the formula for force

A

F=PxA

Force = pressure x area

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9
Q

What are the two types of hydraulic pressure

A

Hydrostatic pressure and hydrodynamic pressure

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10
Q

What type of pressure is used on an aircraft hydraulic system

A

Hydrostatic pressure

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11
Q

What is hydrodynamic pressure

A

Pressure produced by moving liquids ideally with no internal friction

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12
Q

Is it possible to transport force by using solid, liquids and gasses?

A

No, just liquid and gas

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13
Q

What is more easily compressible liquid or gas?

A

Gas is more easily compressible

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14
Q

What substance pressurises more quickly, liquid or gas?

A

Liquid

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15
Q

What two types or hydraulic fluid are there

A

Mineral and synthetic

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16
Q

What colour is mineral oil usually

A

Red

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17
Q

Can mineral oils be mixed together

A

There are many suppliers of mineral oils but they can be mixed together

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18
Q

What colour is synthetic oil usually?

A

Violet or purple

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19
Q

Can synthetic oils be mixed

A

Yes the same grade of synthetic oils can be mixed

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20
Q

Can synthetic and mineral oils be mixed?

A

No

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21
Q

What are the 2 of the most common name of synthetic oil

A

Skydrol and hyjet

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22
Q

What are the prefix’s used by Boeing and Airbus for synthetic oils?

A

Boeing - BMS

Airbus - NSA

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23
Q

What do the oil specifications describe?

A

The oils ability to perform a certain standard through a range of changing conditions

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24
Q

What types of performance characteristics must minders aircraft oils have?

A
  • Low Flammability
  • Good lubricating quality
  • Resistance to freezing
  • Non evaporating
  • Non foaming
  • Chemical stability
  • Hygroscopic quality
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25
Q

What type of chemical stability must aircraft fluids have?

A

Resist oxidation and deterioration over long periods of time.
This will reduce the need of replacing the fluid as frequently

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26
Q

What does hygroscopic mean

A

The ability to absorb water

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27
Q

What is the biggest biggest disadvantage that synthetic oil has over mineral oil

A

Synthetic oil is more hygroscopic which is a disadvantage

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28
Q

Which oils is more toxic to humans mineral or synthetic

A

Synthetic

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29
Q

What does the term packing refer to

A

Within a component housing such as a filter, packing is used to make a seal between the environment and the fluid pressure inside it

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30
Q

What are packings also known as

A

Seals

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31
Q

What would be done if a single seal in a component is not strong enough to perform its task

A

A backup ring is used. This is also a seal

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32
Q

What seals are usually teflon

A

Backup rings

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33
Q

What are normal seals made from

A

Rubber

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34
Q

What is the most common way to damage a seal

A

Using the wrong hydraulic fluid

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35
Q

When choosing seals what things must be remembered

A

What type of temperature and force the seal will be subject to. Also what fluid will be used

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36
Q

How can you double check that the seal you are using is the correct one for the job

A

Check the associated part numbers

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37
Q

What types of pressures are static seals used on

A

Steady or pulsating pressure

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38
Q

What type of pressure are dynamic seals usually subject to

A

Stroking or rotational movement

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39
Q

How do Airbus name their hydraulic systems

A

Usually yellow,blue and green

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40
Q

How do Boeing name their hydraulic systems

A

The numbering system 1,2,3,4

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41
Q

Where are the main hydraulic components kept in Airbus aircraft

A

They are usually in the main gear bay

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42
Q

Do all hydraulic systems share a reservoir

A

No they have independent reservoirs to supply each system

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43
Q

What is the purpose of the hydraulic reservoirs

A

To keep enough fluid for all systems and redundancy fluid in case of a leak

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44
Q

What monitors the hydraulic fluid levels which is then sent to the cock pit

A

A quantity transmitter is located on the side of the reservoirs housing

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45
Q

We’re is the hydraulic reservoirs drain valve located

A

The lowest point of the reservoirs

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46
Q

Why is the hydraulic reservoir pressurised

A

To ensure a positive supply of hydraulic fluid always reaches the pump

It also prevents foaming, evaporation and cavitation

47
Q

What are the two methods of pressuring the hydraulic reservoir

A

One by air and one by hydraulic pressure

48
Q

What is the most common way to pressurise the hydraulic reservoir? What happens if this fails

A

By the engines if they stop providing pressurisation it is done by the pneumatic system

49
Q

What pressure will the hydraulic reservoir be pressurised to

A

Around 50 psi

50
Q

What is an accumulator

A

A device which potential energy is stored in the form of compressed gas or spring

51
Q

Why are accumulators used

A
  • Absorb pulsations
  • cushion operating shock
  • supplements pump delivery
  • maintains pressure
52
Q

What are the 4 main types of accumulators

A
  • Weight loaded piston type
  • Diaphragm or bladder type
  • Spring type
  • Hydropneumatic piston type
53
Q

What are the two categories or accumulators

A

Pneumatic and Mechanical

54
Q

What type of accumulators are the Bladder and Piston

A

Pneumatic

55
Q

What are the two mechanical accumulators

A

Weight and spring

56
Q

If you are using a pneumatic system will you need a reducing valve ?

A

No, they are already regulated

57
Q

What are check valves used for?

A

To prevent air from the hydraulic system going back in to the engine

58
Q

Can you disconnect a hydraulic pump in flight

A

Yes but if you want to reconnect it must be done on the ground

59
Q

What must be done prior to checking accumulator base pressure

A

The system must be unpressurised

60
Q

What are responsible for the system pressurisation

A

Hydraulic pumps

61
Q

What do hydraulic pumps do

A

They create high pressures and fluid flows in the system

62
Q

How are the hydraulic pumps usually powered

A

Either by the engine or electric motor

63
Q

What are the two types of hydraulic piston pump?

A

variable displacement and fixed displacement

64
Q

What is an IDG

A

Integrated Drive Generator

65
Q

What is an EDP

A

Engine Driven Pump

66
Q

What is a VDP

A

Variable Displacement Pump

67
Q

What is an FDP

A

Fixed Displacement Pump

68
Q

What does a fixed displacement pump consist of

A

A pump unit and a handle

69
Q

What would a fixed displacement pump usually be used for?

A

Manual filling of the reservoir or manual opening of the cargo doors

70
Q

How is a fixed displacement pump regulated

A

It is regulated by the mechanic operating it, there is no internal regulation

71
Q

How many pumps are used for power and what are they

A

3 main pumps

Hydraulic
Pneumatic
Electric

72
Q

What type of pump is the EDP

A

Permanently connected variable displacement pump

73
Q

When is it necessary to cut off the supply of hydraulic fluid to an EDP

A

If the engine which it is connected to has a fire

74
Q

Hat type of pump Is the electric pump?

A

Also a variable displacement pump

75
Q

Electric pumps generate a lot of heat, what ways are used to prevent overheating?

A

They are cooled by air or hydraulic fluid. If they become too hot they must be shut off completely

76
Q

What are electric pumps also called

A

Demand pumps

77
Q

Where is the on/off switch for the electric pump

A

The cockpit

78
Q

What is the ADP

A

Air Driven Pump

79
Q

How are the ADP’s switched on or off

A

They cut in automatically if the EDP’s cannot maintain 3000psi or they can be turned on manually in the cockpit

80
Q

Where does the ADP get its air/pressure

A

The pneumatic system

81
Q

What is used to slow down the air from the turbine of a Air Driven Pump to a suitable speed for the VDP?

A

A gearbox

82
Q

What are the 3 uses for auxiliary pressurisation?

A
  • To help maintain pressurisation if there is high user demand
  • To replace the main pressurisation when a fault occurs
  • For maintenance purposes on the ground when engines are not running
83
Q

How is auxiliary pressurisation produced?

A

Ram Air Turbine (RAT), a power transfer unit and an electric pump. Also from sources on the ground.

84
Q

What type of pump is the RAT

A

Variable displacement pump

85
Q

How can the RAT be retracted after it has been deployed

A

It is retracted hydraulically and can only be done on the ground by a mechanic

86
Q

How long will the RAT take to deploy once the button in the cockpit has been pressed?

A

Less than 1 second

87
Q

Is there a way of preventing the RAT being accidentally deployed on the ground?

A

Yes a device is installed, usually made of wood

88
Q

What does PTU stand for?

A

Power Transfer Unit

89
Q

What is the PTU used for

A

It is another way for providing auxiliary pressurisation

Transfers hydraulic power between two systems.

NO FLUIDS are transferred

90
Q

How is the power regulation of the PTU done

A

It is automatic

91
Q

When using ground power to gain hydraulic pressure where would the cart be connected to?

A

The ground service panel

92
Q

There are two connections on the service panel for the hydraulic pressurisation what are they for

A

One is for pressure connection and the other is a return connection

These allow fluid circulation in the system

93
Q

When using the ground power unit for pressurisation which of the 2 connections on the cart has a bigger diameter?

A

The return line to reduce flow resistance

94
Q

What are filters used for?

A

Filters are screening devices used to remove foreign particles from air and fluid systems

95
Q

Why are filters so important?

A

The foreign material that they remove could cause serious damage to vital system components

96
Q

What are the main components of a filter?

A
  • The filter head
  • The filter bowl
  • The filter element
  • The filter bypass

They also have a differential pressure indicator (pop out indicator)

97
Q

The filter element is the most important part of the filter, what are they made from?

A
  • Metal
  • Plastic
  • Paper material
98
Q

What happens if a filter gets clogged?

A

The pressure increases in the unit and the bypass is activated

99
Q

What are the two types of pressure indicator used to tell if a filter is clogged?

A

Pop out and electrical

100
Q

What components are used to move hydraulic fluid from the pumps to the users?

A
  • Lines
  • Hoses
  • Valves
  • And Manifolds (Airbus) / Modules (Boeing)
101
Q

Why do manifolds/modules combine the major distribution components such as valves, filter, switches and transmitters in one place?

A

To make maintenance easier

102
Q

What two sections are manifolds divided in to?

A

High pressure (HP) and Low pressure (LP)

103
Q

What manifold distributes pressurised hydraulic fluid to the users?

A

The HP manifold

104
Q

What are Boeing modules subdivided into?

A

Pressure, return and case drain modules

105
Q

What similar components do the high pressure manifold and pressure module share?

A
  • A system pressure relief valve
  • A pressure switch
  • A filter
106
Q

Airbus manifolds have some additional components over the Boeing modules what are they?

A
  • Pressure transmitter
  • Fluid sampling valve
  • Leak measurement solenoid valve
107
Q

What component on the HP manifold ensures the flows in the right direction to the users?

A

The check valve

108
Q

What component prevents the system from being damaged due to overpressure?

A

The pressure relief valve

109
Q

What does the HP manifolds leak measurement solenoid valve do?

A

Check for internal leakage. Can be opened or closed from cockpit

110
Q

What type of manifold is the priority valve fitted to?

A

Not a part of the HP manifold or module but fitted to different manifolds depending on aircraft type

111
Q

What is the purpose of the Priority valve?

A

To give priority of a more important hydraulic user in at times of great hydraulic demand

112
Q

What type of systems would the Priority Valve give priority to?

A

Flight control surfaces

113
Q

What sensors would be found on a HP manifold

A
  • Two pressure switches which detect low system pressure caused by pump malfunctions or system leaks
  • A pressure transmitter which monitors the pressure at all times.

All data is sent to the cockpit

Module 11 Richard (19 decks)

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