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M11 new josh > 11.11 hyd power > Flashcards

11.11 hyd power Flashcards

(114 cards)

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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
whats the disadvantage of polyalphaolefin based fluids
high viscosity at low temperatures
26
what is the most used hydraulic fluid
phosphate ester based fluid (skydrol)
27
what are the 2 classes of type IV fluids
class I are low density, class II are standard density
28
what are the 2 general hydraulic fluid contaminants
abrasives, non-abrasives
29
what is used for contamination control
filters
30
if a hydraulic system is found contaminated what must happen
system flushed
31
what are the 2 main servicing activities for the hydraulic system
reservoir filling, fluid sampling
32
where does pressurised filling take place
service panel
33
what do you use for manual filling of the reservoir
hand pump
34
where is the hydraulic fluid sampling valve located
high pressure manifold of each hydraulic system
35
what type of valve is the hydraulic sampling valve
needly type valve
36
where is the hydraulic fluid sampled on boeing aircrfat
low pressure part of system
37
how often does a hydraulic system need to be sampled
once a year or every 3000 flight hours
38
is synthetic oil toxic to humans
yes
39
what is the function of the reservoir
store fluid for the system
40
where is the first place a fluid goes after leaving the reservoir
pump
41
what can a reservoir also serve as in a fluid system
overflow basin
42
what are reservoirs classified as
pressurised, non-pressurised
43
where are mesh filters located in the reservoir
filler neck
44
what aircraft are non-pressurised reservoirs used in
aircraft that dont perform violent manoeuvres or at high altitude
45
what aircraft are pressurised reservoirs used on
aircraft that fly at high altitude
46
whats the function of the reservoir pressurisation module
provide bleed air into the reservoir for pressurisation
47
some aircrafts reservoirs arent bleed air pressurised, what else can pressurise them
hydraulic system pressure
48
how are non-pressurised reservoirs service
pouring hydraulic fluid directly into the filler strainer
49
what is a hydraulic accumulator
device where potential energy is stored
50
what are the 2 types of accumulators used in hydraulic systems
spherical, cylindrical
51
what happens during the pre-load of the accumulator
compressed nitrogen in charged to just below system operating pressure
52
what must be done before checking an accumulators pressure
hydraulic system must be unpressurised
53
how many power driven pumps do aircrafts hydraulic systems have
at least one
54
whats the function of the power driven pump
drives fluid in the system
55
what are pumps in the hydraulic system classified as
positive displacement, non-positive displacement
56
what classification of pump are mainly used in hydraulic systems
positive displacement
57
what do constant displacement pumps do
deliver fixed quantities of fluid regardless of pressure
58
is a gear type power pump positive or negative displacement
positive
59
is a gerotor pump positive or negative displacement
positive
60
whats good about piston pumps
can be variable or constant displacement
61
what is a typical constant displacement axial type pump
bent axis piston pump
62
what the simplest axial piston pump
inline piston pump
63
what is displacement determined by in inline piston pumps
size of the piston
64
what is a VDP
variable displacement pump
65
what does a variable displacement pump convert
mechanical energy to hydraulic energy
66
what generates hydraulic system pressure
power driven pump
67
what is an EDP
engine driven pump
68
what is the engine driven pump
variable displacement pump permanently connected to the engine
69
whats an ACMP
alternating current motor pump
70
whats an ADP
air driven pump
71
what type of pump is an air driven pump
variable displacement pump
72
what are the 3 types of hand pump
single action, double action, rotary
73
what are 3 uses for emergency and backup pressurisation
maintain pressurisation, replace main pressurisation, maintenance purposes
74
what is emergency and backup pressurisation produced by
RAT
75
what is RAT
ram air turbine
76
how long does RAT deployment take
less than 1 second
77
whats a PTU
power transfer unit
78
what can electrically driven hydraulic pumps also be used as
primary source of pressurising the hydraulic system in an emergency
79
what is the cause of over 85% of system failure
contamination
80
what materials can hydraulic filters come in
wire mesh, stainless steel, micro glass, cellulose paper
81
what are wire mesh filters made from
steel
82
what hydraulic filter provides best filtration quality
micro glass
83
what sized of contamination can micro glass filters stop
10 microns or greater
84
whats the function of the filter bypass valve
opens if the filter gets clogged
85
what happens when a filter element needs cleaning
a red popout will appear
86
whats the purpose of a relief valve
open when pressure exceeds a certain level
87
what are the most common types of relief valve
ball type, sleeve type, poppet type
88
whats the purpose of pressure regulators
regulate the required pressure under different conditions
89
what do pressure reducers do and where are they used
when a lower pressure is required than the supply system it slowly decreases its pressure
90
whats the function of seals
prevent fluid going pasta certain point
91
what 3 classes are seals divided into
packing, gaskets, wipers
92
what types of packing seal are there
v-rings, u-rings, o-rings
93
what are the colours of o-rings and their compatibility
red- fuel blue - hydraulic fluid
94
in areas with high differential pressure what other seal may be used
backup seal
95
when are static seals used
seal against steady or pulsating pressure
96
when are dynamic seals used
stroking or rotational movement occurs
97
what material is used when a heat resistant gasket is required
asbestos
98
what should you avoid using when installing/removing seals
sharp tools
99
what are the types of non-return valves
check valves, clack valves, reflux valves, retention valves, one way valves
100
whats the function of a shuttle valve
isolate the normal system from the emergency system
101
what are hydraulic fuses
safety devices that can shut off flow in conditions
102
what are heat exchangers used for in the hydraulic system
cool hydraulic fluid from the pumps before it returns to the reservoir
103
pipe fitting come in 2 types, what are they
disconnecting, non-disconnecting
104
what are non-disconnecting pipe fittings used for
to repair broken pipes
105
what classification can hoses be separated into
low, medium, high
106
are hose fittings non-disconnecting or disconnecting type
disconnecting type
107
what are the primary parameters measured of the hydraulic system in the cockpit
fluid pressure, temperature
108
whats located in the hydraulic system to display parameters in the cockpit
electrohydraulic tranducers
109
what is hydraulic fluid quantity measured using
a float in the reservoir
110
pressure sensors can be divided into what subsets
pressure switches, pressure transducers
111
for maintenance what are usually attached to the accumulators and are they calibrated
pressure gauge, not calibrated
112
what are HMDGS
hydraulic motor driven generators
113
in the case of electrical failure what is deployed
hydraulic motor driven generator (HMDGS)
114

M11 new josh (23 decks)

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