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AGK Systems > Hydraulic Systems > Flashcards

Hydraulic Systems Flashcards

1
Q

Hydrostatic Pressure

A

Pressure generated purely and simply by the height of the fluid.

The pressure exerted is dependant only on the height of fluid.

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2
Q

Pascal’s Law

A

Pressure will increase equally throughout, at 90° to the sides of the container, irrespective of area, diameter or shape.

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3
Q

What is the effect of the hydraulic force by increasing the surface area?

A

A larger force will be felt

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4
Q

Relationship between force, pressure and area

A

Force is equal to pressure x area

FAP Triangle

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5
Q

Passive hydraulic system

A

No pump

Pressure is only applied when this force applied to a piston

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6
Q

What is the role of a hydraulic pump?

A

The pump’s purpose is to deliver a flow of fluid to obtain a correct pressure

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7
Q

What are symptoms of air in a passive hydraulic system?

A

Spongy

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8
Q

If air in the passive hydraulic system is detected what is the correct action to take?

A

Air must be bled normally

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9
Q

What is the normal hydraulic operating region?

A

3000psi

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10
Q

Advantage of a high-pressure hydraulic system?

A

Saves weight, eliminating the need for actuators

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11
Q

Chevron seals in a hydraulic system

A

Effective in one direction, ideal for high-pressure usage.

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12
Q

The viscosity of a hydraulic fluid should be:

A

Low to minimise power consumption and resistance to flow.

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13
Q

Filtration in a modern hydraulic system is usually ensured by filters where?

A

Filters in both the pressure and return lines.

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14
Q

A separate pressure regulator is used in a hydraulic system:

A

In conjunction with a constant delivery type pump.

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15
Q

What type of piston pumps are used in a hydraulic system?

A

Axial piston pumps - powerful, but can be off loaded to reduce power consumption.

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16
Q

Formula for Hydraulic Pressure

A

F = A x P

A = F ÷ P therefore.

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17
Q

Synthetic hydraulic fluid

A

Skydrol

Phosphate ester-based synthetic oil, irritable to skin and eyes.

Fire resistant less prone to cavitation and has a high boiling point.

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18
Q

What colour identifies synthetic hydraulic fluid

A

Green or purple

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19
Q

What colour identifies mineral oil

A

Red

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20
Q

What is the purpose of backing rings in a basic hydraulic system

A

Prevents extrustion

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21
Q

If the incorrect fluid was used in a hydraulic system;

A

Damage to the seals could result

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22
Q

Basic System layout of the hydraulic system

A

Reservoir, pump, actuator/jack and selector valve

23
Q

Actuator/Jack

A

Convert pressure energy into linear motion.

Provides the output.

Consist of piston, seals and ram.

Present on undercarriages and flap system.

24
Q

Selector valve

A

Allows the supply and return either side of service

For example, extension and retraction of undercarriage.

Extension- small force.

Retraction- lots of force

25
Q

Single Acting Actuator

A

Is powered in one direction only by hydraulic power.

The return movement being under another force, for example a spring.

26
Q

What is the purpose of the arrow on non-return valve?

A

Prevents the direction of flow

27
Q

Function of the non-return valve

A

As soon as pressure drops the valve shuts.

Prevents return.

28
Q

Selectors on the hydraulic system

A

Purpose is to direct hydraulic flow, dependent on the pilot selection.

29
Q

Hydraulic Lock

A

When fluid is trapped between the piston of a jack, and a non-return valve. Hydraulic lock is formed.

Fluid cannot flow through the system, and the piston is locked.

30
Q

Open-centre hydraulic system

A

Found on light aircraft.

  • Flaps
  • Undercarriage

Can only operate one service at a time

31
Q

Types of hydraulic circuits

A

Passive:

No hydraulic pump
Brakes on the light aircraft
Brahma press

Active:

Mechanically driven pump

32
Q

Hydraulic Power Pack

A

Self-contained independent system

Main disadvantage on light aircraft: can operate one service at a time.

33
Q

Where is the temperature sensor located in a hydraulic system?

A

In the reservoir

34
Q

Hydraulic accumulators

A

Gives impetus by energy stored in nitrogen gas.

Store of hydraulic fluid under pressure

Dumps out pressure fluctuations

35
Q

What is the purpose of the separator in the accumulator

A

Separate liquids from gas

36
Q

Constant Delivery/ Constant Volume hydraulic pump

A

Produces a constant delivery

Needs to be equipped with an ACOV

37
Q

Automatic cut out valve (ACOV)

A

Senses power downstream to keep within a reasonable range.

System leaks will cause cut in/ cut out

38
Q

Effect of low hydraulic pressure on accumulators

A

Fluctuation occurs on an increased level

Hammering of valves

39
Q

What’s the purpose of a Case Drain Filter?

A

Monitor conditions of the parts

40
Q

Thermal relief valve

A

PRESSURE SENSING, extreme temperatures

41
Q

Restrictors in a hydraulic system

A

Located in up line

Restricts flow in the flap system during up flap selection.

Restricts flow in landing your system and creates a restriction gear down selection.

42
Q

Implications of a single pump failure on a hydraulic system

A

Pressure is constant

Delivery and flow is halved.

“Operating times extended”

43
Q

Shuttle valves

A

Enables an alternate supply to operate an actuator

Switch hydraulic unit to most appropriate supply

44
Q

Pressure maintaining valves

A

Priority valve ensure pressure is provided to basic systems in case of failure

45
Q

Pressure reducing valves

A

Reduces from 3000 to 1800 for brakes.

46
Q

Hydraulic fuse

A

Prevent total system loss in an event of a hydraulic leak

47
Q

Power transfer unit (PTU)

A

Transfers power not fluid

Consists of: pump, shaft, motor

48
Q

Mechanical Overload Protection (RELIEF)

A

Fitted in flat circuits and spoiler circuits

Prevent damage during high-speed

Flaps move to intermediate position

As we slowdown they will deploy normally

49
Q

With what type of air is the pressurisation managed in the reservoir?

A

Bleed Air

50
Q

Purpose of the filter in the hydraulic system

A

Prevent ingress of debris and dirt

51
Q

Should a hydraulic pump seize during operation:

A

The quill drive will shear to offload and protect the gearbox.

52
Q

A stack pipe is fitted in a hydraulic reservoir to provide:

A

Emergency supply

53
Q

Check Valve

A

Allows hydraulic fluid to flow in one direction only.

Operates similarly to a diode.

AGK Systems (10 decks)

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