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Willys Flashing > 11.11 > Flashcards

11.11 Flashcards

1
Q

What is the only loss in hydraulic systems?

A

Fluid friction

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2
Q

What are the two types of hydraulic pressure?

A

Hydrostatic
Hydrodynamic

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3
Q

How should pressurisation sources be installed?

A

Parallel

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4
Q

What are pumps designed to supply?

A

Highest demand pressure

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5
Q

How do hydraulic systems build the pressure required?

A

Using a motor driven pump which builds pressure against the selector valve

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6
Q

What is the function of the pressure relief valve?

A

It prevents over pressurisation and relieves excessive pressure due to thermal expansion

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7
Q

How many hydraulic systems are in a typical aircraft and why?

A

3 for redundancy

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8
Q

What is the biggest disadvantage of an open circuit system?

A

Only one surface can be operated at once

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9
Q

How are selector valves connected in open hydraulic systems?

A

In series

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10
Q

What is the main advantage of a closed circuit?

A

Multiple surfaces can be operated at once

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11
Q

How are selector valves connected in closed circuits?

A

In parallel

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12
Q

How does a closed system differ in terms of pressure?

A

Static pressure is built and ready in the neutral position

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13
Q

What is the difference between flash point and fire point?

A

Flash point = the point at which a sufficient amount of fuel vapour collects for a momentary flame
Fire point = the same but it continues to burn

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14
Q

What are the characteristics of mineral-based fluids?

A

-older
-used in low fire risk places
-they are interchangeable

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15
Q

What are the characteristics of polyalphaolefin based fluids?

A

-fire resistant
-high viscosity at low temperatures

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16
Q

What are the characteristics of phosphate ester based and its trade name?

A

Skydroll
-fire resistant
-typically class IV and V are used
-class IV comes in a high and low density vatriant

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17
Q

What are the common contaminant types in hydraulic fluids?

A

Abrasive and non abrasive

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18
Q

How do pressure and manual filling methods in hydraulic fluid differ?

A

Manual relies on a hand pump instead of ground service equipment

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19
Q

What is the purpose of hydraulic fluid sampling?

A

Testing for water contamination and a reduction in fluid performance

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20
Q

What is the purpose of hydraulic system leak tests?

A

To find internal leaks

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21
Q

How must leak tests be done?

A

On individual lines not on the entire system

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22
Q

What are the classes of hydraulic reservoir?

A

-pressurised
-non pressurised

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23
Q

What is the purpose of baffles/ fins?

A

To prevent bad flow forming or air going into the pump

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24
Q

What are the applications of non-pressurised reservoirs?

A

-when the reservoir is in a pressurised area
-when aircraft are not designed for violent manoeuvres
-when the aircraft is not designed for high altitudes

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25
Q

How are hydraulically pressurised reservoirs pressurised?

A

-regulated hydraulic pressure pump/ output is applied to a moveable piston inside a cylindrical reservoir
-this small piston moves a larger piston against the fluid in the reservoir
-the small piston protrudes giving a level indicator

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26
Q

How are hydraulically pressurised reservoirs pressurised?

A

-regulated hydraulic pressure pump/ output is applied to a moveable piston inside a cylindrical reservoir
-this small piston moves a larger piston against the fluid in the reservoir
-the small piston protrudes giving a level indicator

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27
Q

How are non pressurised reservoirs filled?

A

Hydraulic fluid is poured in through a fine strainer

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28
Q

How are pressurised reservoirs filled?

A

By a central filling station in a ground service bay

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29
Q

What is an accumulator?

A

Where potential energy is stored in the form of compressed gas, spring or as a raised weight to exert a force against an incompressible fluid

30
Q

What is the function of the accumulator?

A

It acts as a surge pulsation absorber

31
Q

What are the three principle methods of operation of an accumulator?

A

-spring
-diaphragm
-hydro pneumatic piston separated by a thin piston or diaphragm

32
Q

What are the two pump types?

A

-Positive displacement pump
-non positive displacement

33
Q

Hat are the advantages of constant displacement pumps?

A

Regardless of speed they will supply a fixed unwavering quantity of liquid in line with one rotation

34
Q

What are gear type pumps and their output?

A

-positive displacement
-meshing teeth catch liquid and push it out round a housing

35
Q

How can a piston pump become variable output?

A

A swash plate moves and adjusts the piston extension and therefore the output

36
Q

What does a variable displacement pump do?

A

It converts rotational mechanical energy into hydraulic energy
The output can be changed

37
Q

How is output altered on a variable delivery piston pump?

A

By altering the swash plate angle

38
Q

What are the characteristics of an (EDP) engine driven pump?

A

-primary source of pressure generation
-connected to the engine
-variable displacement

39
Q

What are the uses and design of an electric pump/ an alternating current motor pump?

A

-ground operation/ emergency
-electrically driven drive shaft

40
Q

What are the characteristics of an air driven pump?

A

-demand pumps to supplement other pumps
-variable displacement pumps

41
Q

What are the uses of a hand pump?

A

-fluid displacement
-back up method
-utilises a single or double rotary action

42
Q

What is the RAT ram air turbine and when is it deployed?

A

A variable displacement pump to be deployed if power is low

43
Q

What is the function of the PTU?

A

To pressurise a hydraulic system when a pump has failed

44
Q

What is the purpose of the hydraulic filter module and where is it placed?

A

-safeguards the hydraulic system against impurities
-can be placed anywhere

45
Q

What is the function of a filter?

A

To capture any contaminants in the hydraulic fluid

46
Q

What is the function of a wire mesh filter in a hydraulic system?

A

Surface cleaning

47
Q

What is the purpose of the stainless steel filter?

A

Surface cleaning it is also wire mesh

48
Q

Micros glass filter benefits?

A

-highest filtration quality
-greater than 10 microns filtered

49
Q

What is the structure of a cellulose paper filter?

A

Resin impregnated cellulose filter pleated + assembled

50
Q

What are the main components of a filter?

A

-filter head assembly
-filter bowl
-filter element
-filter bypass valve

51
Q

What is the purpose of the bypass, filter bowl and the filter element?

A

Bowl = housing which holds the element to the filter head drain plug
Element = micron, porous metal or magnetic type
Bypass = for blockages

52
Q

What happens when the hydraulic filter becomes clogged?

A

-differential pressure switch triggers a warning the filter bypass is activated
-a spring loaded bypass is activated
-a red button may become visual showing that it needs changing or cleaning

53
Q

What is the purpose and the types of pressure relief valves?

A

-Ball
-sleeve
-poppet
They have 2 purposes
*System relief valve a safety device against possible pump compensator
*thermal relief valve relieves excessive pressure

54
Q

What is the function and design of pressure regulators?

A

-used when there is a constant delivery type pump
-manages the output of the pump when operating range is normal

55
Q

Pressure reducer design and function?

A

Used to supply a steady lower pressure

56
Q

What are the two main types of selector valves?

A

Open and closed

57
Q

How are selector valves typically controlled?

A

A mechanical lever or electronically selected

58
Q

How is a valve electronically selected?

A

Through a solenoid

59
Q

What is the function of a sequence valve?

A

It controls the the sequence of operation between two branches in a circuit

60
Q

What is a pressure controlled sequence valve and its function?

A

A spring holds tension which moves when a set pressure has been met moving the pin allowing pressure to meet the other port

61
Q

How does a mechanically operated sequence valve differ from a pressure operated one?

A

A ball or poppet is installed between fluid parts

62
Q

How does a priority valve function?

A

When hydraulic pressure drops flow will be directed to systems that are needed only

63
Q

What are the types of non return valves?

A

Check
Clack
Reflux
Retention
One way

They allow flow in only one direction

64
Q

What is the function of a shuttle valve?

A

A hydraulic operated emergency system which functions like a shuttle with a spring

65
Q

What are the functions of hydraulic fuses and their design?

A

A safety device, when a sudden increase in flow is detected fluid flow is shut off

66
Q

What is important when installing, removing and inspecting O rings?

A

When installing
-do not use sharp edge tools use specialised tools if available
When removing
-inspect them and clean before reinstalling immerse the O rings in hydraulic fluid

67
Q

What must you ensure when installing V seals?

A

The open end of the V faces the fluid

68
Q

What must you ensure when installing V seals?

A

The open end of the V faces the fluid

69
Q

What must you ensure when installing O rings?

A

The lips of the packing seals must face the pressure

70
Q

What is the function of the pressure switch?

A

When pressure reaches a set value it will ‘switch’ powering a circuit

71
Q

What is the function of the power transducer?

A

It converts one form of energy to another

Willys Flashing (24 decks)

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