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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
How are hydraulically pressurised reservoirs pressurised?
-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
26
How are hydraulically pressurised reservoirs pressurised?
-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
27
How are non pressurised reservoirs filled?
Hydraulic fluid is poured in through a fine strainer
28
How are pressurised reservoirs filled?
By a central filling station in a ground service bay
29
What is an accumulator?
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
What is the function of the accumulator?
It acts as a surge pulsation absorber
31
What are the three principle methods of operation of an accumulator?
-spring -diaphragm -hydro pneumatic piston separated by a thin piston or diaphragm
32
What are the two pump types?
-Positive displacement pump -non positive displacement
33
Hat are the advantages of constant displacement pumps?
Regardless of speed they will supply a fixed unwavering quantity of liquid in line with one rotation
34
What are gear type pumps and their output?
-positive displacement -meshing teeth catch liquid and push it out round a housing
35
How can a piston pump become variable output?
A swash plate moves and adjusts the piston extension and therefore the output
36
What does a variable displacement pump do?
It converts rotational mechanical energy into hydraulic energy The output can be changed
37
How is output altered on a variable delivery piston pump?
By altering the swash plate angle
38
What are the characteristics of an (EDP) engine driven pump?
-primary source of pressure generation -connected to the engine -variable displacement
39
What are the uses and design of an electric pump/ an alternating current motor pump?
-ground operation/ emergency -electrically driven drive shaft
40
What are the characteristics of an air driven pump?
-demand pumps to supplement other pumps -variable displacement pumps
41
What are the uses of a hand pump?
-fluid displacement -back up method -utilises a single or double rotary action
42
What is the RAT ram air turbine and when is it deployed?
A variable displacement pump to be deployed if power is low
43
What is the function of the PTU?
To pressurise a hydraulic system when a pump has failed
44
What is the purpose of the hydraulic filter module and where is it placed?
-safeguards the hydraulic system against impurities -can be placed anywhere
45
What is the function of a filter?
To capture any contaminants in the hydraulic fluid
46
What is the function of a wire mesh filter in a hydraulic system?
Surface cleaning
47
What is the purpose of the stainless steel filter?
Surface cleaning it is also wire mesh
48
Micros glass filter benefits?
-highest filtration quality -greater than 10 microns filtered
49
What is the structure of a cellulose paper filter?
Resin impregnated cellulose filter pleated + assembled
50
What are the main components of a filter?
-filter head assembly -filter bowl -filter element -filter bypass valve
51
What is the purpose of the bypass, filter bowl and the filter element?
Bowl = housing which holds the element to the filter head drain plug Element = micron, porous metal or magnetic type Bypass = for blockages
52
What happens when the hydraulic filter becomes clogged?
-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
What is the purpose and the types of pressure relief valves?
-Ball -sleeve -poppet They have 2 purposes *System relief valve a safety device against possible pump compensator *thermal relief valve relieves excessive pressure
54
What is the function and design of pressure regulators?
-used when there is a constant delivery type pump -manages the output of the pump when operating range is normal
55
Pressure reducer design and function?
Used to supply a steady lower pressure
56
What are the two main types of selector valves?
Open and closed
57
How are selector valves typically controlled?
A mechanical lever or electronically selected
58
How is a valve electronically selected?
Through a solenoid
59
What is the function of a sequence valve?
It controls the the sequence of operation between two branches in a circuit
60
What is a pressure controlled sequence valve and its function?
A spring holds tension which moves when a set pressure has been met moving the pin allowing pressure to meet the other port
61
How does a mechanically operated sequence valve differ from a pressure operated one?
A ball or poppet is installed between fluid parts
62
How does a priority valve function?
When hydraulic pressure drops flow will be directed to systems that are needed only
63
What are the types of non return valves?
Check Clack Reflux Retention One way They allow flow in only one direction
64
What is the function of a shuttle valve?
A hydraulic operated emergency system which functions like a shuttle with a spring
65
What are the functions of hydraulic fuses and their design?
A safety device, when a sudden increase in flow is detected fluid flow is shut off
66
What is important when installing, removing and inspecting O rings?
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
What must you ensure when installing V seals?
The open end of the V faces the fluid
68
What must you ensure when installing V seals?
The open end of the V faces the fluid
69
What must you ensure when installing O rings?
The lips of the packing seals must face the pressure
70
What is the function of the pressure switch?
When pressure reaches a set value it will ‘switch’ powering a circuit
71
What is the function of the power transducer?
It converts one form of energy to another

Willys Flashing (24 decks)

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