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M11 > 11.11 hyd power > Flashcards

11.11 hyd power Flashcards

1
Q

what psi does civil aircraft hydraulic systems work at

A

3000 psi

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2
Q

what are the 2 types of hydraulic pressure

A

hydrostatic, hydrodynamic

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3
Q

what is hydraulic fluid stored in

A

a reservoir

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4
Q

to have enough redundancy for safe flight what happens with hydraulic systems

A

have multiple systems of the same design

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5
Q

how are the 3 hydraulic systems identified

A

blue, green, yellow

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6
Q

aircraft with two or more hydraulic systems are required to have what

A

independent mechanical system

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7
Q

what is an open-centre hydraulic system

A

one fluid flow but no system pressure when mechanisms are idle

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8
Q

what is a closed-centre hydraulic system

A

fluid is un der pressure whenever power pump is operating

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9
Q

in a closed-centre hydraulic system if constant delivery pumps are used what is also required

A

pressure regulator, relief valve

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10
Q

whats an advantage of the open centre system over the closed centre system

A

continuous pressurisation of the system is eliminated

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11
Q

what is a hydraulic power pack system

A

compact unit with a pump, reservoir, valves, filters, pressure relief valves

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12
Q

whats the advantage of a power pack

A

no need for centralised hydraulic power supply system or long hydraulic lines

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13
Q

what oil properties do modern aircraft require

A

low flammability, corrosion resistant, good lubrication, non-evaporating, chemical stable

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14
Q

if a fluid is hygroscopic what does it tend to do

A

absorb water

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15
Q

whats one of the most important properties of hydraulic fluid

A

viscosity

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16
Q

what is viscosity

A

internal resistance to flow

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17
Q

whats viscosities relation with temperature

A

viscosity increases as temp decreases

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18
Q

what is chemical stability

A

liquids ability to resist oxidation and deterioration for long periods

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19
Q

are liquids with higher viscosity more or less resistant to temp

A

more resistance

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20
Q

what is flash point

A

temp at which a liquid gives off vapour sufficiently to ignite

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21
Q

what is fire point

A

temp at which a substance gives off vapour in sufficient to ignite and continue to burn

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22
Q

what are the 3 principal categories of hydraulic fluids

A

minerals, polyalphaolefins, phosphate esters

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23
Q

when are mineral based fluids usually used

A

when fire hazards are low

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24
Q

can mineral oil be mixed together and what colour are they dyed

A

can be mixed and are dyed red

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25
Q

whats the disadvantage of polyalphaolefin based fluids

A

high viscosity at low temperatures

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26
Q

what is the most used hydraulic fluid

A

phosphate ester based fluid (skydrol)

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27
Q

what are the 2 classes of type IV fluids

A

class I are low density, class II are standard density

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28
Q

what are the 2 general hydraulic fluid contaminants

A

abrasives, non-abrasives

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29
Q

what is used for contamination control

A

filters

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30
Q

if a hydraulic system is found contaminated what must happen

A

system flushed

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31
Q

what are the 2 main servicing activities for the hydraulic system

A

reservoir filling, fluid sampling

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32
Q

where does pressurised filling take place

A

service panel

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33
Q

what do you use for manual filling of the reservoir

A

hand pump

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34
Q

where is the hydraulic fluid sampling valve located

A

high pressure manifold of each hydraulic system

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35
Q

what type of valve is the hydraulic sampling valve

A

needly type valve

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36
Q

where is the hydraulic fluid sampled on boeing aircrfat

A

low pressure part of system

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37
Q

how often does a hydraulic system need to be sampled

A

once a year or every 3000 flight hours

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38
Q

is synthetic oil toxic to humans

A

yes

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39
Q

what is the function of the reservoir

A

store fluid for the system

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40
Q

where is the first place a fluid goes after leaving the reservoir

A

pump

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41
Q

what can a reservoir also serve as in a fluid system

A

overflow basin

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42
Q

what are reservoirs classified as

A

pressurised, non-pressurised

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43
Q

where are mesh filters located in the reservoir

A

filler neck

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44
Q

what aircraft are non-pressurised reservoirs used in

A

aircraft that dont perform violent manoeuvres or at high altitude

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45
Q

what aircraft are pressurised reservoirs used on

A

aircraft that fly at high altitude

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46
Q

whats the function of the reservoir pressurisation module

A

provide bleed air into the reservoir for pressurisation

47
Q

some aircrafts reservoirs arent bleed air pressurised, what else can pressurise them

A

hydraulic system pressure

48
Q

how are non-pressurised reservoirs service

A

pouring hydraulic fluid directly into the filler strainer

49
Q

what is a hydraulic accumulator

A

device where potential energy is stored

50
Q

what are the 2 types of accumulators used in hydraulic systems

A

spherical, cylindrical

51
Q

what happens during the pre-load of the accumulator

A

compressed nitrogen in charged to just below system operating pressure

52
Q

what must be done before checking an accumulators pressure

A

hydraulic system must be unpressurised

53
Q

how many power driven pumps do aircrafts hydraulic systems have

A

at least one

54
Q

whats the function of the power driven pump

A

drives fluid in the system

55
Q

what are pumps in the hydraulic system classified as

A

positive displacement, non-positive displacement

56
Q

what classification of pump are mainly used in hydraulic systems

A

positive displacement

57
Q

what do constant displacement pumps do

A

deliver fixed quantities of fluid regardless of pressure

58
Q

is a gear type power pump positive or negative displacement

A

positive

59
Q

is a gerotor pump positive or negative displacement

A

positive

60
Q

whats good about piston pumps

A

can be variable or constant displacement

61
Q

what is a typical constant displacement axial type pump

A

bent axis piston pump

62
Q

what the simplest axial piston pump

A

inline piston pump

63
Q

what is displacement determined by in inline piston pumps

A

size of the piston

64
Q

what is a VDP

A

variable displacement pump

65
Q

what does a variable displacement pump convert

A

mechanical energy to hydraulic energy

66
Q

what generates hydraulic system pressure

A

power driven pump

67
Q

what is an EDP

A

engine driven pump

68
Q

what is the engine driven pump

A

variable displacement pump permanently connected to the engine

69
Q

whats an ACMP

A

alternating current motor pump

70
Q

whats an ADP

A

air driven pump

71
Q

what type of pump is an air driven pump

A

variable displacement pump

72
Q

what are the 3 types of hand pump

A

single action, double action, rotary

73
Q

what are 3 uses for emergency and backup pressurisation

A

maintain pressurisation, replace main pressurisation, maintenance purposes

74
Q

what is emergency and backup pressurisation produced by

A

RAT

75
Q

what is RAT

A

ram air turbine

76
Q

how long does RAT deployment take

A

less than 1 second

77
Q

whats a PTU

A

power transfer unit

78
Q

what can electrically driven hydraulic pumps also be used as

A

primary source of pressurising the hydraulic system in an emergency

79
Q

what is the cause of over 85% of system failure

A

contamination

80
Q

what materials can hydraulic filters come in

A

wire mesh, stainless steel, micro glass, cellulose paper

81
Q

what are wire mesh filters made from

A

steel

82
Q

what hydraulic filter provides best filtration quality

A

micro glass

83
Q

what sized of contamination can micro glass filters stop

A

10 microns or greater

84
Q

whats the function of the filter bypass valve

A

opens if the filter gets clogged

85
Q

what happens when a filter element needs cleaning

A

a red popout will appear

86
Q

whats the purpose of a relief valve

A

open when pressure exceeds a certain level

87
Q

what are the most common types of relief valve

A

ball type, sleeve type, poppet type

88
Q

whats the purpose of pressure regulators

A

regulate the required pressure under different conditions

89
Q

what do pressure reducers do and where are they used

A

when a lower pressure is required than the supply system it slowly decreases its pressure

90
Q

whats the function of seals

A

prevent fluid going pasta certain point

91
Q

what 3 classes are seals divided into

A

packing, gaskets, wipers

92
Q

what types of packing seal are there

A

v-rings, u-rings, o-rings

93
Q

what are the colours of o-rings and their compatibility

A

red- fuel
blue - hydraulic fluid

94
Q

in areas with high differential pressure what other seal may be used

A

backup seal

95
Q

when are static seals used

A

seal against steady or pulsating pressure

96
Q

when are dynamic seals used

A

stroking or rotational movement occurs

97
Q

what material is used when a heat resistant gasket is required

A

asbestos

98
Q

what should you avoid using when installing/removing seals

A

sharp tools

99
Q

what are the types of non-return valves

A

check valves, clack valves, reflux valves, retention valves, one way valves

100
Q

whats the function of a shuttle valve

A

isolate the normal system from the emergency system

101
Q

what are hydraulic fuses

A

safety devices that can shut off flow in conditions

102
Q

what are heat exchangers used for in the hydraulic system

A

cool hydraulic fluid from the pumps before it returns to the reservoir

103
Q

pipe fitting come in 2 types, what are they

A

disconnecting, non-disconnecting

104
Q

what are non-disconnecting pipe fittings used for

A

to repair broken pipes

105
Q

what classification can hoses be separated into

A

low, medium, high

106
Q

are hose fittings non-disconnecting or disconnecting type

A

disconnecting type

107
Q

what are the primary parameters measured of the hydraulic system in the cockpit

A

fluid pressure, temperature

108
Q

whats located in the hydraulic system to display parameters in the cockpit

A

electrohydraulic tranducers

109
Q

what is hydraulic fluid quantity measured using

A

a float in the reservoir

110
Q

pressure sensors can be divided into what subsets

A

pressure switches, pressure transducers

111
Q

for maintenance what are usually attached to the accumulators and are they calibrated

A

pressure gauge, not calibrated

112
Q

what are HMDGS

A

hydraulic motor driven generators

113
Q

in the case of electrical failure what is deployed

A

hydraulic motor driven generator (HMDGS)

114
Q
A

M11 (15 decks)

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