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M11 > 11.11 > Flashcards

11.11 Flashcards

1
Q

Where is the hydraulic fluid kept ?

A

Reservoir

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2
Q

Whats the two types of hydraulic pressure ?

A

Hydrostatic pressure - produced by static fluids
Hydrodynamic pressure - produced by moving liquids

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3
Q

What Is used to require a low pressure demand in a hydraulic system ?

A

Pressure relief valve
( all pressure is high pressure so must reduce it to reach low pressure demand )

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4
Q

How can a pressure relief valve maintain a certain pressure ?

A

Diverts exes pressure down another route back to the reservoir by opening a ball valve

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5
Q

What is a selector valves function ?

A

Select which side of actuator needs to be pressurised and which side is the return.

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6
Q

Explain what an open centre hydraulic system is ?

A

-Has fluid flow but no pressure In the system when the actuating mechanisms are idle.

-only one component can be operated at a single time

-action is delayed compared to a closed centre system

( fluid returns back to reservoir if not in use )

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7
Q

Explain what a closed centre hydraulic system is ?

A

-Fluid is always under pressure whenever the pump is operating.

-actuators are in parallel

-multiple components can be operated at the same time.

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8
Q

What do hydraulic boost systems assist the flight crew with ?

A

Overcoming high control forces.

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9
Q

Whats the three hydraulic fluids used ?

A

-minerals
-polyalphaolefins
-phosphate esters

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10
Q

Explain mineral - based hydraulic fluids ?

A

They can be mixed and are dyed red.
- used in areas where fire hazards are low

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11
Q

Explain polyalphaolefin - based hydraulic fluids ?

A

Fire resistant and has high viscosity at low temperatures

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12
Q

Explain phosphate ester - based hydraulic fluid ( skydrol )?

A

Extremely fire - resistant ( not fire proof )

Has two types of:
Type 1 - low density
Type 2 - standard density

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13
Q

What should happen if a hydraulic system is serviced with the wrong fluid ?

A

Immediately drain and flush system

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14
Q

Whats the two main servicing activities for the hydraulic system ?

A

Reservoir refilling
Fluid sampling

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15
Q

Where is the hydraulic sampling valve located ?

A

HP manifold on each hydraulic system.

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16
Q

How often should you perform a hydraulic fluid sample ?

A

Once a year or every 3000 flight hours.

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17
Q

What materials does skydrol react with if it’s contaminated ?

A

Aluminium
Magnesium
Silver
Zinc
Iron
Stainless steel

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18
Q

Whats used to pressure fill a hydraulic reservoir ?

A

Pressurised Groud equipment

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19
Q

Whats used to manually fill a hydraulic reservoir ?

A

Hand pump

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20
Q

What does a hydraulic system leak test not detect ?

A

Pressure leaks

( opening or closing the selector valve, isolates the internal leakage in specific parts of system )

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21
Q

Whats a baffle plate used for in a hydraulic fluid reservoir ?

A

Maintains fluid in reservoir incase of a sudden altitude drop ?

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22
Q

Which type of aircraft use non-pressurised reservoirs ?

A

Aircraft which are not designed for violent manoeuvres, don’t fly high.

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23
Q

What do non-pressurised reservoirs use to measure the fluid quantity ?

A

Visual gauge
( non-pressurised reservoirs are slightly pressurised due to thermal expansion )

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24
Q

Which aircraft use pressurised hydraulic fluid reservoirs ?

A

Aircraft which fly high.

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25
Q

Why is pressurised reservoirs required to be pressurised ?

A

As they are often located in non-pressurised areas of the aircraft meaning in high altitudes where there Is not enough atmospheric pressure can cause the fluid to reach the pumps.

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26
Q

What does the reservoir pressurisation module supply to the reservoirs ?

A

Aircraft bleed air
( located close to the reservoirs )

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27
Q

Whats the two types of accumulators ?

A

Spherical
Cylindrical

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28
Q

Explain a spherical accumulator ?

A

Steel sphere divided into two chambers where the upper chamber holds fluid and the lower chamber holds nitrogen. When demand is made upon the system, the compressed air forces the fluid out of the accumulator

29
Q

Explain a cylindrical accumulator ?

A

Cylinder with a piston. Piston assembly separated the hydraulic fluid from the air/nitrogen chamber. The piston is sealed internally with double seal rings preventing leakage.

30
Q

Which accumulator is usually used in a high pressure hydraulic system ?

A

Cylindrical

31
Q

Whats the three methods of operation for an accumulator ?

A

Diaphragm
Spring type
Piston type

32
Q

Is the nitrogen chamber in an accumulator pressurised more the same as or lower than the system operating pressure ?

A

Lower

33
Q

What must you ensure is done before checking the accumulator base pressure ?

A

Hydraulic system must be unpressurised

34
Q

Whats the two types of pumps ?

A

Positive displacement
Non-positive displacement

35
Q

Whats the use for a RAT ( ram air turbine ) ?
Emergency backup

A

Provides electrical and hydraulic power if the primary sources of aircraft power are lost.

36
Q

Whats the primary output from deploying the RAT ( ram air turbine ) ?

A

Hydraulic power incase its lost

37
Q

What is a PTUs operation in an aircraft ?

A

Allows hydraulic power to be transferred between the different hydraulic systems to equally maintain 3000psi

38
Q

Whats the 4 materials a hydraulic filter is available in ?

A

Wire mesh
Stainless steel
Micro glass
Cellulose paper

39
Q

What is wire mesh filters used for ?

A

Surface cleaning

40
Q

What is stainless steel filters used for ?

A

Same as wire mesh but juts made from stainless steel

41
Q

What is micro glass filters used for ?

A

Prevents the passage of solids greater than 10 microns

42
Q

Explain what can happen if the filter gets clogged stopping the fluid from flowing ?

A

This causes an increase of pressure which a spring - loaded valve is opened allowing the unfiltered fluid to bypass the filter element.

43
Q

Explain the function of a relief valve ?

A

Discharges fluid from the pressure line into a reservoir return line when the pressure exceeds the pre determined maximum pressure

44
Q

Whats the 3 relief valves ?

A

-ball type
-sleeve type
-poppet type

45
Q

What the 2 things that a pressure relief valve should be used as ?

A

System relief valve
— to maintain the systems pressure by sending some of the exes pressure back to the reservoir

Thermal relief valve
— relieves excessive pressures that may exist due to thermal expansion.

46
Q

What does the pressure regulator do ?

A

—Manages the output of the pump to maintain the system pressure within a pre determined range.

—Permit the pump to Turn without resistance.

47
Q

Whats the use of the pressure reducing valves ?

A

Used in hydraulic system to reduce the main operating pressure by a specific amount.

( all systems main operating pressure = 3000psi so if you needed a maximum of 2800psi to operate a system you use a pressure reduce valve to provide that expected amount )

48
Q

How is power distribution in a hydraulic system controlled ?

A

Through Flow control valves

49
Q

What does a flow control valve control ?

A

Controls the speed or direction of fluid flow in a hydraulic system.

50
Q

Explain a shut off valve ?

A

Shuts off the flow of fluid to a particular system.

51
Q

Explain a selector valve ?

A

Controls the direction of movement of a hydraulic actuator.

Provides flow of hydraulic fluid both into and out of the unit.

52
Q

Whats the two types of selector valves ?

A

Open centre
Closed centre

53
Q

Explain a solenoid - operated selector valve ?

A

When the solenoids are energised, the pressure port routes the fluid to the actuator by moving 2 ball valves ( LEFT & RIGHT ) in a certain direction which directs the fluid to a specific side of the actuator chamber

54
Q

Explain a sequence valve ?

A

Controls a sequence of operations between two branches in a circuit

( pressure operated )

55
Q

Explain how a sequence valve works ?

A

Works like a relief valve,
After set pressure is met, the sequence valve diverts the fluid to a second actuator or motor to work another part of the system.

56
Q

Explain how a mechanically operated sequence valve works ?

A

Operated by a plunger which extends through body of the valve which unseats the check valve and allows the fluid to flow through the valve.

( rod from actuator hits plunger which moves ball valves allowing fluid to flow )

57
Q

Explain what a priority valves function is ?

A

To give priority to the critical hydraulic subsystems over non critical systems when the system pressure is low.

58
Q

Explain the use of a quick disconnect valve ?

A

Installed in hydraulic lines to prevent loss of fluid when units are removed.

59
Q

Explain a non-return valve ?

A

Allows fluid to flow through itself in only one direction.

60
Q

Explain a shuttle valve ?

A

Valve which has 2 inlets and 1 outlets
( normal system inlet )
( alternate system inlet )
- alternate = emergency inlet

61
Q

Explain the function of a hydraulic fuse ?

A

Detects sudden increase in flow which shuts off the fluid flow preserving hydraulic fluid for the rest of the system.

62
Q

Explain how a hydraulic actuator works ?

A

Transforms energy in the form of fluid pressure into a mechanical force or action.

63
Q

Whats the two types of actuating cylinders ?

A

Single-action
Double-action

64
Q

Whats the three main classes of seals ?

A

Packing - used on a sliding or moving assembly

Gasket - used between non- moving fittings

Wipers - used for cleaning

65
Q

Whats the two pressure sensors used to warn pilots ?

A

Pressure switch
Pressure transducer

66
Q

Explain the operation of the pressure switch ?

A

Measures system pressure which if reaches above or below set point closes a circuit and sounds a alarm in flight deck

( only give signal when circuit is Made )

67
Q

Explain the operation of a pressure transducer ?

A

They sample and record the pressure in the system

( continuously show pressure reading on screen )

68
Q

What is the use for power by wire PBW ?

A

M11 (22 decks)

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