11.11 Hydraulic Power Flashcards
(167 cards)
1
Q
What is the origin of the word “hydraulics”?
A) Latin word for fluid
B) Roman word for oil
C) Greek word for water
A
C) Greek word for water
2
Q
Which of the following was an early use of hydraulics in aviation?
A) Actuating slats
B) Operating flight controls
C) Simple brake systems
A
C) Simple brake systems
3
Q
Why do larger aircraft require hydraulic systems?
A) To operate navigation systems
B) To deflect control surfaces against high air pressure
C) To manage cabin pressure
A
B) To deflect control surfaces against high air pressure
4
Q
What is a key benefit of modern hydraulic systems on large aircraft?
A) Reduces lift
B) Increases drag
C) Moves heavy components like landing gear
A
C) Moves heavy components like landing gear
5
Q
What pressure range do large commercial aircraft typically use in their hydraulic systems?
A) 100–500 psi
B) 1000–2000 psi
C) 3000–5000 psi
A
C) 3000–5000 psi
6
Q
Which of the following is NOT listed as a use of aircraft hydraulic systems?
A) Cabin lighting
B) Landing gear actuation
C) Windshield wipers
A
A) Cabin lighting
7
Q
What is a disadvantage of the hydraulic system?
A) Difficult to maintain
B) Fluid contamination can damage the system
C) Sparks during operation
A
B) Fluid contamination can damage the system
8
Q
What is the unit of pressure in hydraulics as used in aviation?
A) Watts
B) Joules
C) psi
A
C) psi
9
Q
How does one generate higher hydraulic force?
A) Reduce actuator diameter
B) Increase fluid temperature
C) Increase actuator size or system pressure
A
C) Increase actuator size or system pressure
10
Q
Which of the following is a component of a basic hydraulic system?
A) Circuit breaker
B) Motor-driven pump
C) Generator
A
B) Motor-driven pump
11
Q
What prevents hydraulic over-pressurisation?
A) Check valve
B) Actuator
C) Pressure relief valve
A
C) Pressure relief valve
12
Q
How are Airbus aircraft hydraulic systems commonly named?
A) Numbers
B) Colors: blue, green, yellow
C) Letters: A, B, C
A
B) Colors: blue, green, yellow
13
Q
What describes an open-centre hydraulic system?
A) Pressure is constant at all times
B) Fluid only flows during actuation
C) Fluid circulates without pressure when idle
A
C) Fluid circulates without pressure when idle
14
Q
What is a key characteristic of a closed-centre system with a variable displacement pump?
A) Uses only manual pumps
B) Has constant fluid flow regardless of pressure
C) Pump compensator reduces flow as pressure increases
A
C) Pump compensator reduces flow as pressure increases
15
Q
Why is the closed-centre system preferred in most aircraft?
A) Slower operation
B) Instant pressure availability
C) Less complex
A
B) Instant pressure availability
16
Q
What did power boost systems allow pilots to do?
A) Fly without instruments
B) Manually override all systems
C) Overcome high control forces
A
C) Overcome high control forces
17
Q
What is a major advantage of hydraulic power pack systems?
A) Requires centralized fluid lines
B) Adds extra weight
C) Reduces system weight
A
C) Reduces system weight
18
Q
What innovation did the Boeing 787 introduce in its systems?
A) Fully manual flight controls
B) Increased use of mechanical systems
C) More electrical than hydraulic systems
A
C) More electrical than hydraulic systems
19
Q
What is the primary function of hydraulic system liquids?
A) To increase the weight of aircraft components
B) To prevent corrosion in fuel tanks
C) To transmit and distribute forces
A
C) To transmit and distribute forces
20
Q
What principle states that pressure applied to a confined liquid is transmitted with undiminished intensity?
A) Newton’s Law
B) Pascal’s Law
C) Bernoulli’s Principle
A
B) Pascal’s Law
21
Q
Why do fluids pressurize more efficiently than gases?
A) They are heavier
B) They compress more
C) They are less compressible
A
C) They are less compressible
22
Q
Which of the following is NOT one of the required properties of modern hydraulic oils for aircraft?
A) High flammability
B) Corrosion resistance
C) Chemical stability
A
A) High flammability
23
Q
What does hygroscopic mean in relation to hydraulic fluid?
A) It is highly flammable
B) It evaporates easily
C) It absorbs water
A
C) It absorbs water
24
Q
Which type of oil is more hygroscopic?
A) Synthetic oil
B) Mineral oil
C) Both equally
A
A) Synthetic oil
25
What is viscosity?
A) The rate of oxidation in fluids
B) Internal resistance to flow
C) Ability to evaporate quickly
B) Internal resistance to flow
26
What happens to viscosity as temperature decreases?
A) It remains the same
B) It decreases
C) It increases
C) It increases
27
What is used to measure the viscosity of hydraulic fluids?
A) Thermometer
B) Hydrometer
C) Viscometer
C) Viscometer
28
What does chemical stability refer to in hydraulic fluids?
A) Their freezing point
B) Their ability to flow quickly
C) Their resistance to oxidation and deterioration
C) Their resistance to oxidation and deterioration
29
What is flash point?
A) Temperature at which liquid boils
B) Temperature at which vapour ignites momentarily
C) Temperature at which fluid freezes
B) Temperature at which vapour ignites momentarily
30
What is fire point?
A) Temperature at which fluid starts to boil
B) Temperature at which liquid freezes
C) Temperature at which vapour ignites and continues to burn
C) Temperature at which vapour ignites and continues to burn
31
Which is NOT one of the three principal categories of hydraulic fluids?
A) Polyalphaolefins
B) Alcohol esters
C) Phosphate esters
B) Alcohol esters
32
What should be done if the wrong hydraulic fluid is used?
A) Continue operation as normal
B) Drain, flush, and replace the system fluid
C) Add more of the correct fluid
B) Drain, flush, and replace the system fluid
33
What colour is MIL‑H‑5606 typically dyed?
A) Blue
B) Yellow
C) Red
C) Red
34
What is a disadvantage of MIL‑H‑83282 fluid?
A) High flammability
B) Low viscosity at high temperature
C) High viscosity at low temperature
C) High viscosity at low temperature
35
What type of aircraft typically uses Skydrol® fluids?
A) Gliders
B) Light sport aircraft
C) Commercial transport category aircraft
C) Commercial transport category aircraft
36
What are type V hydraulic fluids designed for?
A) Lower flash point
B) Greater fire resistance
C) Higher thermal stability
C) Higher thermal stability
37
What is a potential consequence of fluid contamination?
A) Higher fuel consumption
B) Hydraulic system malfunction
C) Longer filter life
B) Hydraulic system malfunction
38
What are the two general categories of hydraulic contaminants?
A) Solid and liquid
B) Gas and vapour
C) Abrasive and non-abrasive
C) Abrasive and non-abrasive
39
How should hydraulic fluid samples be taken?
A) From the top of the reservoir
B) With random container bottles
C) According to manufacturer’s instructions
C) According to manufacturer’s instructions
40
What is the main method for controlling hydraulic contamination during normal operation?
A) Cooling systems
B) Visual inspections
C) Filters
C) Filters
41
What is used during hydraulic servicing to manually fill the reservoir?
A) Ground service cart
B) Hand pump
C) Pressurised tank
B) Hand pump
42
What component in pressurised filling prevents system overpressure?
A) Check valve
B) Ground service filter
C) Restrictor
C) Restrictor
43
How often should routine hydraulic fluid sampling be performed?
A) Once every month
B) Every 1000 flight hours
C) Once a year or every 3000 flight hours
C) Once a year or every 3000 flight hours
44
What does the leak measurement solenoid valve do when de-energised?
A) It closes
B) It heats the fluid
C) It remains open
C) It remains open
45
What does a leak measurement manifold help identify?
A) The reservoir level
B) System pressure loss
C) Internal leaks
C) Internal leaks
46
What material is softened by Skydrol® fluids after prolonged exposure?
A) Steel
B) Polyurethane
C) Linoleum
C) Linoleum
47
What type of paints are resistant to Skydrol®?
A) Oil-based
B) Epoxies
C) Nitrocellulose lacquers
B) Epoxies
48
What protective equipment should be used when handling synthetic hydraulic fluids?
A) Apron and hat
B) Gloves and eye protection
C) Insulated boots
B) Gloves and eye protection
49
What is the primary purpose of a hydraulic reservoir?
A) To supply the system with fluid during high-pressure conditions
B) To store an adequate supply of fluid for the system and replenish fluid lost through leakage
C) To prevent contamination from entering the system
B) To store an adequate supply of fluid for the system and replenish fluid lost through leakage
50
What happens if there is a sudden loss of altitude in a pressurised hydraulic reservoir?
A) The fluid will overflow from the reservoir
B) The fluid supply to the pressurisation pump is cut off
C) The reservoir will become over-pressurised
B) The fluid supply to the pressurisation pump is cut off
51
What is the role of baffle plates or fins in most hydraulic reservoirs?
A) To increase the fluid pressure
B) To prevent vortexing and surging of the fluid
C) To filter the fluid before it enters the pump
B) To prevent vortexing and surging of the fluid
52
What type of reservoir is typically used in aircraft not designed for violent manoeuvres or high altitudes?
A) Pressurised Reservoir
B) Non-pressurised Reservoir
C) Emergency Hydraulic Reservoir
B) Non-pressurised Reservoir
53
What is the purpose of the manual air bleed valve in a non-pressurised reservoir?
A) To control fluid pressure during operation
B) To vent the reservoir and prevent fluid from being blown out during servicing
C) To remove foreign matter from the system
B) To vent the reservoir and prevent fluid from being blown out during servicing
54
Which component prevents over-pressurisation in a pressurised hydraulic reservoir?
A) Sight glasses
B) Reservoir pressure relief valve
C) Reservoir sample/drain valve
B) Reservoir pressure relief valve
55
How is the fluid level in a fluid-pressurised reservoir indicated?
A) Using a digital pressure gauge
B) By markings on the pressurising cylinder cover
C) By sight glasses on the reservoir's exterior
B) By markings on the pressurising cylinder cover
56
What is a key safety precaution when servicing hydraulic reservoirs?
A) Always ensure the aircraft is at a low altitude
B) Ensure that the parking brake accumulator pressure reads at least 2500 psi
C) Keep the landing gear doors open
B) Ensure that the parking brake accumulator pressure reads at least 2500 psi
57
Which type of hydraulic accumulator is most commonly used in modern aircraft?
A) Diaphragm type
B) Spring type
C) Hydro-pneumatic piston type
C) Hydro-pneumatic piston type
58
What is the function of a hydraulic accumulator in an aircraft's hydraulic system?
A) To store energy and smooth out pulsations in the system
B) To filter contaminants from the hydraulic fluid
C) To maintain a constant fluid temperature
A) To store energy and smooth out pulsations in the system
59
In a spherical hydraulic accumulator, what separates the fluid from the air/nitrogen?
A) A piston
B) A diaphragm or bladder
C) A spring
B) A diaphragm or bladder
60
What should be done before servicing or maintaining an accumulator?
A) Ensure the hydraulic system is pressurised
B) Discharge all preload air or nitrogen pressure
C) Use oxygen to inflate the accumulator
B) Discharge all preload air or nitrogen pressure
61
What is the primary danger when working with hydraulic accumulators?
A) Risk of contamination from hydraulic fluid
B) Rapid and violent release of pressurised air/nitrogen
C) Risk of electrical hazards
B) Rapid and violent release of pressurised air/nitrogen
62
What type of gas is used to charge accumulators in hydraulic systems?
A) Compressed air
B) Oxygen
C) Nitrogen
C) Nitrogen
63
What should never be used for pre-charging a hydraulic accumulator due to explosion and fire risks?
A) Nitrogen
B) Compressed air or oxygen
C) Hydraulic fluid
B) Compressed air or oxygen
64
What is the primary function of the hydraulic pump in an aircraft hydraulic system?
A) To generate electricity
B) To drive fluid flow and generate pressure
C) To control the engine speed
B) To drive fluid flow and generate pressure
65
What is the primary source of pressure generation on most aircraft?
A) Pneumatically-driven pump
B) Engine-driven pump
C) Hand pump
B) Engine-driven pump
66
Which type of hydraulic pump is powered by an electric motor?
A) Mechanically-driven pump
B) Pneumatically-driven pump
C) Electrical motor-driven pump
C) Electrical motor-driven pump
67
What is a characteristic of a non-positive displacement pump?
A) It provides a fixed volume of fluid per revolution
B) It produces a continuous flow but varies its output with pressure
C) It uses gears to generate pressure
B) It produces a continuous flow but varies its output with pressure
68
Which of the following types of pumps is a positive displacement pump?
A) Gear type power pump
B) Non-positive displacement pump
C) Both A and B
A) Gear type power pump
69
What does a gerotor pump consist of?
A) A housing, gears, and a coupling to turn the rotor
B) A housing, eccentric-shaped stationary liner, and gears
C) A rotor with vanes and a stator
B) A housing, eccentric-shaped stationary liner, and gears
70
What type of pump is commonly used as the main system pump on aircraft?
A) Vane pump
B) Piston pump
C) Hand pump
B) Piston pump
71
What is the function of a shear section in a pump drive coupling?
A) To increase pump speed
B) To serve as a safety device by preventing damage if the pump jams
C) To reduce hydraulic pressure
B) To serve as a safety device by preventing damage if the pump jams
72
What kind of pumps are typically used in modern aircraft hydraulic systems?
A) Pneumatically-driven pumps only
B) Engine-driven pumps only
C) A combination of engine-driven, electrical, and pneumatic pumps
C) A combination of engine-driven, electrical, and pneumatic pumps
73
What is a characteristic of variable displacement pumps (VDPs)?
A) They can only perform one operation
B) Their flow rate and outlet pressure can be changed during operation
C) They are more energy-efficient than fixed displacement pumps
B) Their flow rate and outlet pressure can be changed during operation
74
What is the function of the blocking valve in a variable displacement pump?
A) To control the speed of the pump
B) To remain open during normal operation and allow leakage for lubrication
C) To stop fluid flow when the pump is not in use
B) To remain open during normal operation and allow leakage for lubrication
75
Where are electrically-driven power pumps typically installed?
A) On the engine's accessory gearbox
B) In the wheel well bay or hydraulics bay near the root of the wings
C) Near the hydraulic reservoir
B) In the wheel well bay or hydraulics bay near the root of the wings
76
What does the term "main pressurisation" refer to in an aircraft's hydraulic system?
A) The emergency backup system
B) The generation of primary hydraulic power by the engine-driven pump
C) The function of the electrical pump
B) The generation of primary hydraulic power by the engine-driven pump
77
What is the primary function of pneumatically-driven pumps in modern aircraft?
A) To drive the main engine
B) To supplement the primary pumps and provide pressure when needed
C) To control the hydraulic fluid temperature
B) To supplement the primary pumps and provide pressure when needed
78
What is the role of the hand pump in an aircraft's hydraulic system?
A) To act as a backup when power-driven pumps fail
B) To control the engine's output
C) To power the aircraft's main flight controls
A) To act as a backup when power-driven pumps fail
79
Which of the following is a type of hand pump used in aircraft?
A) Vane pump
B) Double-action hand pump
C) Piston pump
B) Double-action hand pump
80
What is the function of a variable displacement pump (VDP) in an aircraft system?
A) To supply fluid at a constant rate
B) To change the flow rate and outlet pressure during operation
C) To supplement the engine-driven pumps
B) To change the flow rate and outlet pressure during operation
81
How does the gear type power pump generate fluid flow?
A) By rotating a central rotor
B) By the meshing of two gears that capture and move fluid
C) By using hydraulic force from the engine
B) By the meshing of two gears that capture and move fluid
82
What is the purpose of a Power Transfer Unit (PTU) in an aircraft hydraulic system?
A) To increase the power output of the engine
B) To transfer hydraulic power between systems for redundancy
C) To filter the hydraulic fluid
B) To transfer hydraulic power between systems for redundancy
83
What happens when a shear section of a pump drive coupling shears?
A) The hydraulic system becomes inoperative
B) The pump is damaged and cannot be repaired
C) The pump or driving unit is protected from damage
C) The pump or driving unit is protected from damage
84
What is the primary use of emergency and backup pressurisation in aircraft hydraulic systems?
A) To supply fuel to the aircraft
B) To assist the main pressurisation in high-demand situations or replace it when a fault occurs
C) To monitor engine temperature
B) To assist the main pressurisation in high-demand situations or replace it when a fault occurs
85
How is the Ram Air Turbine (RAT) deployed in most aircraft?
A) It is deployed automatically when the hydraulic pressure system fails or an electrical malfunction occurs
B) It is deployed manually by the flight crew using a lever
C) It is deployed only during maintenance
A) It is deployed automatically when the hydraulic pressure system fails or an electrical malfunction occurs
86
How is the RAT retracted once deployed?
A) It is retracted manually by the flight crew
B) It is retracted hydraulically, and only an engineer can do so on the ground
C) It retracts automatically when the power systems are restored
B) It is retracted hydraulically, and only an engineer can do so on the ground
87
What is a key safety precaution when working around the RAT system during maintenance?
A) The area around the RAT should be kept clear and cordoned off as a 'no-entry' safety zone
B) The RAT should always be left deployed
C) The RAT should be manually locked in place to prevent retraction
A) The area around the RAT should be kept clear and cordoned off as a 'no-entry' safety zone
88
What is the function of the Power Transfer Unit (PTU) in an aircraft hydraulic system?
A) To supply power to the aircraft's engines
B) To transfer power between hydraulic systems when one system's pump fails
C) To filter hydraulic fluid
B) To transfer power between hydraulic systems when one system's pump fails
89
How does a PTU transfer power between hydraulic systems?
A) It transfers both fluid and power between systems
B) It uses a hydraulic pump and motor connected via a single drive shaft to transfer power, but not fluid
C) It requires an external power source
B) It uses a hydraulic pump and motor connected via a single drive shaft to transfer power, but not fluid
90
How can the activation of a PTU occur?
A) Only manually by the crew
B) Automatically, using a pressure switch to detect pump failure
C) Only when the aircraft is on the ground
B) Automatically, using a pressure switch to detect pump failure
91
What is the purpose of an electrically-driven hydraulic pump (ACMP) in an aircraft hydraulic system?
A) To act as a primary or emergency backup source of hydraulic pressure
B) To control engine fuel flow
C) To charge the aircraft's electrical systems
A) To act as a primary or emergency backup source of hydraulic pressure
92
What is the cooling mechanism used to prevent overheating of the motor in an electrically-driven hydraulic pump?
A) The motor is cooled by air or hydraulic fluid is circulated through the motor
B) A water-based cooling system is used
C) The pump motor shuts down automatically to avoid overheating
A) The motor is cooled by air or hydraulic fluid is circulated through the motor
93
What type of pump is typically used in the Ram Air Turbine (RAT)?
A) Variable Displacement Pump (VDP)
B) Gear pump
C) Fixed displacement pump
A) Variable Displacement Pump (VDP)
94
What type of power does the Ram Air Turbine (RAT) provide when deployed?
A) Only hydraulic power
B) Only electrical power
C) Both hydraulic and electrical power
C) Both hydraulic and electrical power
95
What is the primary function of ground equipment in relation to aircraft hydraulic systems?
A) To test the aircraft's hydraulic systems
B) To pressurise the hydraulic system when no aircraft pressurisation systems are available
C) To monitor fuel pressure
B) To pressurise the hydraulic system when no aircraft pressurisation systems are available
96
What happens when the hydraulic pump fails in a PTU system?
A) The backup pump automatically kicks in
B) Power is transferred from one hydraulic system to another using the PTU
C) The aircraft loses all hydraulic power
B) Power is transferred from one hydraulic system to another using the PTU
97
What type of hydraulic pump is used in an Alternating Current Motor Pump (ACMP)?
A) A nine-piston variable displacement hydraulic pump
B) A fixed displacement hydraulic pump
C) A gear-type hydraulic pump
A) A nine-piston variable displacement hydraulic pump
98
How does the RAT prevent inadvertent deployment during ground operations?
A) The flight crew must manually lock the RAT in place
B) Aircraft systems are configured to prevent deployment when on the ground
C) The RAT can only be deployed when the aircraft reaches a certain speed
B) Aircraft systems are configured to prevent deployment when on the ground
99
What is the primary function of hydraulic filters in aircraft systems?
A) To supply additional hydraulic fluid to the system
B) To clean the hydraulic fluid by removing foreign particles and contaminants
C) To regulate the pressure within the hydraulic system
B) To clean the hydraulic fluid by removing foreign particles and contaminants
100
Where can filters be located in an aircraft hydraulic system?
A) Only in the return line
B) In the reservoir, pressure line, return line, or other locations as needed by the system designer
C) Only in the pressure line
B) In the reservoir, pressure line, return line, or other locations as needed by the system designer
101
What type of contaminants do hydraulic filters typically remove from the fluid?
A) Only particulate contaminants
B) Particulate, air, and water contaminants
C) Only air contaminants
B) Particulate, air, and water contaminants
102
Which of the following is the best filtration material for hydraulic filters?
A) Wire mesh
B) Micro glass
C) Stainless steel
B) Micro glass
103
What does the micron rating of a hydraulic filter indicate?
A) The cost of the filter
B) The smallest particle size that the filter can remove
C) The size of the filter element
B) The smallest particle size that the filter can remove
104
Which type of filter material is typically used for surface cleaning in hydraulic systems?
A) Micro glass
B) Wire mesh
C) Cellulose paper
B) Wire mesh
105
What is the function of the filter bypass valve?
A) To stop the hydraulic fluid when the filter is clogged
B) To prevent hydraulic fluid from bypassing the filter in all conditions
C) To allow continued hydraulic flow when the filter is clogged
C) To allow continued hydraulic flow when the filter is clogged
106
What happens when the filter element becomes clogged?
A) The hydraulic system stops working completely
B) The differential pressure indicator triggers a warning and the filter bypass is activated
C) The filter automatically cleans itself
B) The differential pressure indicator triggers a warning and the filter bypass is activated
107
What does a red button popping out on the filter indicate?
A) The filter is working properly
B) The filter is clogged, and the bypass valve has been activated
C) The hydraulic fluid is too clean
B) The filter is clogged, and the bypass valve has been activated
108
How should filters with a micron-type element be maintained?
A) Only cleaned
B) Periodically replaced or cleaned according to instructions
C) Left unchanged
B) Periodically replaced or cleaned according to instructions
109
What materials are used to make filter elements?
A) Metal, plastic, or paper
B) Rubber or glass
C) Metal and rubber only
A) Metal, plastic, or paper
110
Why is it important to use high-quality hydraulic filters?
A) To reduce the weight of the system
B) To prevent contamination that could lead to system failure
C) To increase the speed of hydraulic fluid flow
B) To prevent contamination that could lead to system failure
111
What does the term "differential pressure" refer to in a hydraulic filter?
A) The difference in pressure between two hydraulic lines
B) The difference in pressure before and after the filter
C) The pressure needed to open the filter bypass valve
B) The difference in pressure before and after the filter
112
Which type of filter material is made from resin-impregnated cellulose?
A) Micro glass
B) Stainless steel
C) Cellulose paper
C) Cellulose paper
113
What should be done if a filter element is damaged?
A) The filter element should be replaced
B) The filter should be cleaned and reinstalled
C) The filter should be ignored until it causes further issues
A) The filter element should be replaced
114
What is the main purpose of pressure control valves in hydraulic systems?
A) To increase the pressure in the system
B) To release, reduce, or regulate the pressure to maintain a required range
C) To store hydraulic fluid
B) To release, reduce, or regulate the pressure to maintain a required range
115
What is the function of a pressure relief valve in a hydraulic system?
A) To increase the hydraulic pressure
B) To limit the pressure exerted on the fluid to prevent system failure
C) To monitor the fluid temperature
B) To limit the pressure exerted on the fluid to prevent system failure
116
Which of the following is a type of pressure relief valve commonly used in hydraulic systems?
A) Poppet type
B) Butterfly type
C) Ball type
A) Poppet type
117
What is the main function of a thermal relief valve?
A) To increase the pressure in the hydraulic system
B) To relieve excessive pressure due to thermal expansion of the fluid
C) To regulate the flow rate of the hydraulic fluid
B) To relieve excessive pressure due to thermal expansion of the fluid
118
What is the function of a pressure regulator in hydraulic systems?
A) To increase the output of the pump
B) To maintain system operating pressure within a predetermined range
C) To remove contaminants from the hydraulic fluid
B) To maintain system operating pressure within a predetermined range
119
What do pressure-reducing valves do in hydraulic systems?
A) They increase the pressure in the system
B) They maintain normal system pressure
C) They lower the normal system operating pressure to a specified value
C) They lower the normal system operating pressure to a specified value
120
What is the purpose of hydraulic seals in hydraulic systems?
A) To prevent fluid from passing a certain point and keep air and dirt out
B) To increase fluid pressure
C) To allow the fluid to flow through the system more efficiently
A) To prevent fluid from passing a certain point and keep air and dirt out
121
Which of the following is a type of packing seal used in hydraulic systems?
A) V-ring
B) Butterfly seal
C) Flat gasket
A) V-ring
122
What is the primary use of a U-ring packing seal in hydraulic systems?
A) To seal low-pressure areas
B) To seal high-pressure areas
C) To reduce the pressure in the system
A) To seal low-pressure areas
123
What does the colour coding on some O-rings indicate?
A) The size of the O-ring
B) The fluid compatibility of the O-ring
C) The manufacturer of the O-ring
B) The fluid compatibility of the O-ring
124
What is the role of backup rings in hydraulic systems?
A) To increase the pressure in the system
B) To support seals in areas with high differential pressure
C) To prevent leakage of fluids in the system
B) To support seals in areas with high differential pressure
125
What is the function of dynamic seals in hydraulic systems?
A) To seal static pressure areas
B) To seal areas where stroking or rotational movements occur
C) To increase the system pressure
B) To seal areas where stroking or rotational movements occur
126
What material is commonly used for high-temperature gaskets in hydraulic systems?
A) Rubber
B) Cork
C) Asbestos
C) Asbestos
127
What should be done when installing O-rings in hydraulic systems?
A) Use sharp-edged tools to fit the O-ring into place
B) Clean and inspect parts before installation and avoid twisting or rolling the O-ring
C) Install the O-ring without checking the hydraulic fluid
B) Clean and inspect parts before installation and avoid twisting or rolling the O-ring
128
How should backup rings made of Teflon™ be inspected?
A) Check for separation in the coils of more than 1/4 inch when unrestrained
B) Ensure that the surface is coated with lubricant
C) Check for signs of corrosion and rust
A) Check for separation in the coils of more than 1/4 inch when unrestrained
129
What is the main purpose of flow control valves in hydraulic systems?
A) To control the speed and/or direction of fluid flow
B) To prevent fluid leaks
C) To increase the pressure in the system
A) To control the speed and/or direction of fluid flow
130
Which valve is used to shut off the flow of fluid to a particular system or component in a hydraulic system?
A) Selector valve
B) Shut-off valve
C) Sequence valve
B) Shut-off valve
131
Which type of selector valve allows a continuous flow of hydraulic fluid even when it is not actuating a unit?
A) Closed centre selector valve
B) Open centre selector valve
C) Priority valve
B) Open centre selector valve
132
What is the primary function of a sequence valve in a hydraulic system?
A) To control fluid flow direction
B) To control the sequence of operation between two branches
C) To increase fluid pressure
B) To control the sequence of operation between two branches
133
What is the function of a priority valve in a hydraulic system?
A) To increase system pressure
B) To give priority to critical hydraulic subsystems
C) To control the sequence of operations
B) To give priority to critical hydraulic subsystems
134
Where are hydraulic fuses commonly installed in a hydraulic system?
A) Hydraulic actuators
B) Brake system, landing gear lines, and thrust reverser lines
C) Heat exchangers
B) Brake system, landing gear lines, and thrust reverser lines
135
Which type of hydraulic actuator transforms fluid pressure into mechanical force to perform work?
A) Rotary actuator
B) Linear actuator
C) Servo actuator
B) Linear actuator
136
What is the key difference between single-action and double-action hydraulic actuating cylinders?
A) Single-action cylinders only extend, while double-action cylinders can both extend and retract
B) Single-action cylinders use two ports, while double-action cylinders use one port
C) Double-action cylinders require a selector valve, while single-action cylinders do not
A) Single-action cylinders only extend, while double-action cylinders can both extend and retract
137
What type of actuator is commonly used in Nose Wheel Steering (NWS) mechanisms?
A) Piston-type actuator
B) Rotary actuator
C) Linear actuator
B) Rotary actuator
138
What is the primary function of heat exchangers in hydraulic systems?
A) To increase the pressure of hydraulic fluid
B) To cool the hydraulic fluid before it returns to the reservoir
C) To filter the hydraulic fluid
B) To cool the hydraulic fluid before it returns to the reservoir
139
Which type of pipe fitting is used to repair broken pipes in a hydraulic system?
A) Non-disconnecting pipe fitting
B) Disconnecting pipe fitting
C) Swivel pipe fitting
A) Non-disconnecting pipe fitting
140
What is the classification of hoses used in hydraulic systems based on?
A) Their color
B) Their resistance to heat
C) Their suitability for different pressures
C) Their suitability for different pressures
141
What is the primary function of hydraulic line identification markings?
A) To indicate the pressure of the fluid
B) To indicate the fluid type used
C) To identify the aircraft system, function, and direction of fluid flow
C) To identify the aircraft system, function, and direction of fluid flow
142
Which valve is used to isolate the normal hydraulic system from an alternate or emergency system in case of failure?
A) Shuttle valve
B) Sequence valve
C) Non-return valve
A) Shuttle valve
143
What is the purpose of a non-return valve in a hydraulic system?
A) To control the sequence of operations
B) To allow fluid to flow in one direction while preventing flow in the opposite direction
C) To increase the fluid pressure
B) To allow fluid to flow in one direction while preventing flow in the opposite direction
144
What are the primary hydraulic system indications monitored on the flight deck?
A) Pressure, temperature, and fluid quantity
B) Fluid color, pressure, and pump speed
C) Fluid pressure, temperature, and hydraulic valve position
A) Pressure, temperature, and fluid quantity
145
Where are system pressure sensors typically located in a hydraulic system?
A) In the hydraulic reservoirs
B) At the hydraulic system pressure filter modules
C) At the hydraulic pumps
B) At the hydraulic system pressure filter modules
146
Which device is used to monitor brake pressure in a hydraulic system?
A) Pressure transducer
B) Electrohydraulic transducer
C) Separate transmitter and indication
C) Separate transmitter and indication
147
What type of device is a pressure switch?
A) A mechanical device that measures pressure
B) A passive device that records pressure changes
C) An active electromechanical device that opens or closes a circuit
C) An active electromechanical device that opens or closes a circuit
148
What is the main purpose of a pressure transducer in a hydraulic system?
A) To measure and record pressure changes and convert them to electrical signals
B) To trigger alarms when pressure reaches certain levels
C) To measure mechanical deformation under pressure
A) To measure and record pressure changes and convert them to electrical signals
149
Where is the hydraulic fluid quantity typically monitored?
A) At the reservoir using a float gauge, sight glass, or other sensing mechanism
B) At the pressure filter
C) At the pump
A) At the reservoir using a float gauge, sight glass, or other sensing mechanism
150
Which of the following types of pressure transducers is commonly used in hydraulic systems?
A) Piezoelectric
B) Strain gauge
C) Thermistor
B) Strain gauge
151
What happens when a temperature switch in the hydraulic system is triggered?
A) The pump will stop immediately
B) A pre-set temperature is reached, and the system displays an 'OVERHEAT' warning
C) The hydraulic fluid will be cooled automatically
B) A pre-set temperature is reached, and the system displays an 'OVERHEAT' warning
152
What is the main function of hydraulic pressure gauges in aircraft?
A) To measure and record system temperatures
B) To provide quick reference for accumulator pressure during maintenance
C) To monitor the fluid flow rate
B) To provide quick reference for accumulator pressure during maintenance
153
Which mechanical device is commonly used to measure pressure in a hydraulic system?
A) Bourdon tube
B) Manometer
C) Strain gauge
A) Bourdon tube
154
What happens when system pressure or reservoir content falls below safe levels?
A) The system automatically shuts down
B) The associated box(es) are displayed in amber, and a caution message is posted
C) The hydraulic fluid is automatically replenished
B) The associated box(es) are displayed in amber, and a caution message is posted
155
What is typically shown on the flight deck hydraulic synoptic display?
A) Pressure, temperature, and fluid color
B) Reservoir contents, flight control pressures, and utility pressures
C) The status of each hydraulic component
B) Reservoir contents, flight control pressures, and utility pressures
156
Which systems in an aircraft are powered by pressurised hydraulic fluids?
A) Flight controls, landing gear, brakes, slats, flaps, thrust reversers
B) Flight controls, communication systems, and lighting
C) Flight controls, landing gear, and fuel pumps
A) Flight controls, landing gear, brakes, slats, flaps, thrust reversers
157
How are hydraulic system parameters and status conditions input into the controlling computer?
A) Manually by the flight crew
B) Automatically by the hydraulic system components
C) Through the mechanical power of the hydraulic system
C) Through the mechanical power of the hydraulic system
158
What happens when hydraulic system parameters are out of the normal operating range?
A) The flight crew manually adjusts the hydraulic system
B) The system operates in alternate modes
C) The hydraulic system is shut down completely
B) The system operates in alternate modes
159
What is the function of a Hydraulic Motor-Driven Generator (HMDG)?
A) To provide an alternative source of hydraulic power
B) To act as a backup power supply for electrical failure
C) To control the hydraulic actuators in flight controls
B) To act as a backup power supply for electrical failure
160
Which of the following is part of a hydro-mechanical flight control system?
A) Electrohydraulic servo valves
B) Fly-by-wire control system
C) Mechanical rods, cables, pulleys, and chains
C) Mechanical rods, cables, pulleys, and chains
161
What does the hydraulic circuit in a hydro-mechanical flight control system include?
A) Flight deck controls and control surfaces
B) Pumps, reservoirs, filters, pipes, valves, and actuators
C) Hydraulic motors and electrical generators
B) Pumps, reservoirs, filters, pipes, valves, and actuators
162
What does a Fly-by-wire (FBW) system replace in an aircraft?
A) The mechanical flight control systems
B) The hydraulic flight control actuators
C) The electrical power generation system
A) The mechanical flight control systems
163
What is the main disadvantage of a Fly-by-wire system?
A) It is too complex and expensive
B) If a single actuator fails, the entire hydraulic system must stop
C) It does not provide adequate control response
B) If a single actuator fails, the entire hydraulic system must stop
164
What does Power-By-Wire (PBW) technology do?
A) It replaces the mechanical flight controls with electronic signals
B) It replaces the centralised hydraulic system with localised actuators
C) It uses electrical power to drive the entire hydraulic system
B) It replaces the centralised hydraulic system with localised actuators
165
What is the primary feature of an Electro Hydrostatic Actuator (EHA)?
A) It is a manual control system
B) It uses a self-contained, modular actuator system for flight control surfaces
C) It replaces hydraulic actuators with pneumatic systems
B) It uses a self-contained, modular actuator system for flight control surfaces
166
How is the movement of the actuator controlled in an Electro Hydrostatic Actuator (EHA)?
A) By the speed and direction of the servo motor
B) By the flight crew directly
C) By hydraulic valves regulating the fluid flow
A) By the speed and direction of the servo motor
167
What does the controller in an Electro Hydrostatic Actuator (EHA) do?
A) Controls the speed of the hydraulic pump
B) Provides an output signal based on the error between desired and measured displacement
C) Monitors the fuel consumption of the system
B) Provides an output signal based on the error between desired and measured displacement
