11.11 Hydraulic Power Flashcards
(118 cards)
1
Q
What is a common operating pressure for hydraulic systems in large aircraft?
A. 200 psi.
B. 5000 psi.
C. 100 psi.
A
B. 5000 psi.
2
Q
Which of the following is an advantage of hydraulic systems?
A. They are difficult to maintain.
B. They are almost 100% efficient.
C. They often cause sparks.
A
B. They are almost 100% efficient.
3
Q
Which of these is a disadvantage of hydraulic systems?
A. Leakage can cause fire hazards.
B. They are not safe on flights.
C. They are prone to mechanical breakdowns.
A
A. Leakage can cause fire hazards.
4
Q
Which aircraft component is powered by the hydraulic system?
A. Cockpit door
B. Windshield wipers.
C. Engine cooling system.
A
B. Windshield wipers.
5
Q
How many psi does 1 bar correspond to in aviation hydraulic systems?
A. 100 psi.
B. 14.5 psi.
C. 3000 psi.
A
B. 14.5 psi.
6
Q
What are the two types of hydraulic pressure?
A. Static pressure and dynamic pressure.
B. Hydrostatic pressure and hydrodynamic pressure.
C. Atmospheric pressure and fluid pressure.
A
B. Hydrostatic pressure and hydrodynamic pressure.
7
Q
What is the purpose of the reservoir in a hydraulic system?
A. To increase fluid pressure.
B. To store hydraulic fluid.
C. To filter contaminants.
A
B. To store hydraulic fluid.
8
Q
What does a one-way check valve do in a hydraulic system?
A. Prevents over-pressurization.
B. Allows fluid to move in one direction only.
C. Filters contaminants.
A
B. Allows fluid to move in one direction only.
9
Q
Which component prevents the system from over-pressurisation?
A. Pressure relief valve.
B. Directional valve.
C. Hand pump.
A
A. Pressure relief valve.
10
Q
What does an actuator do in a hydraulic system?
A. Stores hydraulic fluid.
B. Provides movement to control surfaces.
C. Filters foreign particles.
A
B. Provides movement to control surfaces.
11
Q
Which component prevents contaminants from reaching other parts of the hydraulic system?
A. Filter.
B. Reservoir.
C. Check valve.
A
A. Filter.
12
Q
Where are the main components of hydraulic systems often located in an aircraft?
A. In the cockpit
B. In the main gear bay
C. In the cargo hold
A
B. In the main gear bay
13
Q
What happens to pressure in an open-centre hydraulic system when actuating mechanisms are idle?
A. High pressure is maintained
B. No pressure in the system
C. Pressure fluctuates constantly
A
B. No pressure in the system
14
Q
In an open-centre system, how are selector valves connected?
A. In parallel
B. In series
C. Independently
A
B. In series
15
Q
In a closed-centre hydraulic system, when is fluid under pressure?
A. Only when actuators are operating
B. Whenever the power pump is operating
C. Only during takeoff and landing
A
B. Whenever the power pump is operating
16
Q
How are the selector valves arranged in a closed-centre system?
A. In series
B. In parallel
C. Independently
A
B. In parallel
17
Q
Which hydraulic system is less likely to cause pressure shock during operation?
A. Closed-centre system, because pressure is constant
B. Open-centre system, because pressure builds gradually
C. Both systems cause the same amount of pressure shock
A
B. Open-centre system, because pressure builds gradually
18
Q
Why are liquids used in hydraulic systems to transmit force?
A. Because they are easily compressed
B. Because they are almost incompressible
C. Because they evaporate quickly
A
B. Because they are almost incompressible
19
Q
Why is gas less efficient than fluids for transmitting force in hydraulic systems?
A. Gas is too heavy
B. Gas is easily compressed
C. Gas cannot be pressurised
A
B. Gas is easily compressed
20
Q
Why is a high flash point important for hydraulic fluids?
A. It helps the fluid freeze quicker
B. It indicates good resistance to combustion
C. It means the fluid evaporates quickly
A
B. It indicates good resistance to combustion
21
Q
What are the three principal categories of hydraulic fluids?
A. Mineral, Polyalphaolefins, Phosphate esters
B. Oil-based, Water-based, Synthetic
C. Hydraulic oil, Brake fluid, Coolant
A
A. Mineral, Polyalphaolefins, Phosphate esters
22
Q
Which types of fluids are currently used in commercial transport aircraft?
A. Type I and II
B. Type III and IV
C. Type IV and V
A
C. Type IV and V
23
Q
Phosphate ester-based hydraulic fluid is commonly known as:
A. Mineral oil
B. Skydrol
C. Polyalphaolefin
A
B. Skydrol
24
Q
What are the two general types of contaminants in hydraulic fluid?
A. Abrasives and Non-abrasives
B. Solids and Liquids
C. Gases and Liquids
A
A. Abrasives and Non-abrasives
25
What are the two main servicing activities for hydraulic systems?
A) Pressure testing and component replacement
B) Reservoir filling and fluid sampling
C) Cleaning and painting
B) Reservoir filling and fluid sampling
26
What safety precautions should be taken when handling synthetic hydraulic fluids like Skydrol®?
A) Wear proper gloves and eye protection, wash off immediately if contact occurs, and clean spills quickly to avoid damage
B) It is safe to handle without protection; only avoid swallowing the fluid
C) Use any respirator without checking for suitability and avoid touching the fluid only if it smells strong
A) Wear proper gloves and eye protection, wash off immediately if contact occurs, and clean spills quickly to avoid damage
27
What is the primary purpose of a hydraulic reservoir?
A) To store an adequate supply of hydraulic fluid for the system
B) To prevent hydraulic fluid from evaporating under high temperatures
C) To heat the hydraulic fluid before it enters the system
A) To store an adequate supply of hydraulic fluid for the system
28
What are the two main classifications of hydraulic reservoirs?
A) Open-loop and Closed-loop
B) Pressurised and Non-pressurised
C) Thermal and Non-thermal
B) Pressurised and Non-pressurised
29
What components are incorporated in most reservoirs to prevent hydraulic fluid from swirling or surging during movement?
A) Pressurisation pumps
B) Baffle plates and/or fins
C) Finger strainers
B) Baffle plates and/or fins
30
Why should finger strainers never be removed or punctured during reservoir servicing?
A) They are critical for the pressurisation pump’s operation.
B) Removing or puncturing them could allow air to enter the hydraulic system.
C) This could lead to contamination and compromise the reservoir’s performance.
C) This could lead to contamination and compromise the reservoir’s performance.
31
Why are non-pressurised reservoirs slightly pressurised?
A) To ensure positive fluid flow to the hydraulic pump inlets
B) To maintain cabin pressure consistency
C) To prevent thermal expansion of the hydraulic fluid
A) To ensure positive fluid flow to the hydraulic pump inlets
32
Non-pressurised reservoirs are typically used in aircraft that:
A) Perform violent manoeuvres and fly at extreme altitudes
B) Are not designed for violent manoeuvres and do not fly at high altitudes
C) Operate only under pressurised cabin conditions
B) Are not designed for violent manoeuvres and do not fly at high altitudes
33
What is the function of the reservoir quantity transmitter?
A) To transmit fluid quantity information to the flight deck
B) To drain hydraulic fluid for maintenance
C) To regulate pressure inside the reservoir
A) To transmit fluid quantity information to the flight deck
34
Why are pressurised reservoirs on aircraft designed?
A) For high-altitude flight
B) For low-altitude flight
C) For ground operations
A) For high-altitude flight
35
How can non-pressurised reservoirs be serviced?
A) By pouring fluid directly through a filler strainer
B) Only using a hydraulic mule
C) Through an external pressurised fluid source
A) By pouring fluid directly through a filler strainer
36
How are pressurised reservoirs typically serviced on aircraft?
A) From a central filling station in the ground service bay
B) By manually pouring fluid into the filler neck
C) By disconnecting the reservoir from the system
A) From a central filling station in the ground service bay
37
What is the primary purpose of a hydraulic accumulator in a fluid power system?
A) To increase the size of the pump
B) To store potential energy and smooth out pulsations
C) To filter hydraulic fluid
B) To store potential energy and smooth out pulsations
38
What gas is commonly used to charge the gas chamber in accumulators?
A) Oxygen
B) Nitrogen
C) Carbon dioxide
B) Nitrogen
39
Which two general types of accumulators are used in aircraft hydraulic systems?
A) Spherical and Cylindrical
B) Diaphragm and Spring
C) Piston and Bladder
A) Spherical and Cylindrical
40
What personal protective equipment (PPE) is recommended when working on accumulators?
A) Gloves and safety glasses
B) Ear plugs and helmet
C) Respirator and full body suit
A) Gloves and safety glasses
41
What must always be done before disassembling any accumulator?
A) Charge the accumulator with nitrogen
B) Ensure all preload air or nitrogen pressure has been discharged
C) Inflate the accumulator to maximum pressure
B) Ensure all preload air or nitrogen pressure has been discharged
42
What is the primary function of a hydraulic pump in an aircraft hydraulic system?
A) To regulate temperature
B) To drive fluid flow and generate pressure
C) To control the aircraft’s speed
B) To drive fluid flow and generate pressure
43
How can a hydraulic pump be driven in an aircraft?
A) Only mechanically
B) Mechanically, electrically, or pneumatically
C) Only electrically
B) Mechanically, electrically, or pneumatically
44
What type of pump is usually the primary source of pressure generation in most aircraft?
A) Hand pump
B) Pneumatic pump
C) Mechanically-driven pump
C) Mechanically-driven pump
45
What additional type of pump may be included in aircraft hydraulic systems to operate if the main pump fails?
A) Electric pump
B) Hand pump
C) Pneumatic pump
B) Hand pump
46
What type of pump is usually installed for emergencies or ground operations when the engines are not running?
A) Pneumatically-driven pump
B) Electrically-driven pump
C) Mechanically-driven pump
B) Electrically-driven pump
47
What are the two classifications of hydraulic pumps used in aircraft systems?
A) Positive displacement and non-positive displacement
B) Mechanical and electrical
C) Pneumatic and manual
A) Positive displacement and non-positive displacement
48
What type of pump delivers a fixed quantity of fluid per revolution regardless of pressure demands?
A) Variable displacement pump
B) Constant displacement pump
C) Non-positive displacement pump
B) Constant displacement pump
49
How many vanes does a typical vane-type power pump contain?
A) Two
B) Four
C) Six
B) Four
50
What is the primary purpose of hydraulic hand pumps on aircraft?
A) Main source of hydraulic pressure
B) Used for testing and emergency backup
C) To supply continuous hydraulic pressure during flight
B) Used for testing and emergency backup
51
What type of pump is commonly used to maintain hydraulic pressure when the engine-driven pumps fail?
A) Pneumatically-driven pump
B) Hand pump
C) Electrically-driven pump (ACMP)
C) Electrically-driven pump (ACMP)
52
What emergency device is often fitted on large transport aircraft to provide backup hydraulic and electric power?
A) Power Transfer Unit (PTU)
B) Ram Air Turbine (RAT)
C) Air Driven Pump (ADP)
B) Ram Air Turbine (RAT)
53
What is one use of emergency and backup pressurisation related to high user demand?
A) To replace the main pressurisation when a fault occurs
B) To help the main pressurisation if there is high user demand
C) For maintenance purposes on the ground when the engines are not running
B) To help the main pressurisation if there is high user demand
54
When is emergency and backup pressurisation used to replace the main pressurisation?
A) During ground maintenance only
B) When a fault occurs in the main system
C) To assist with high user demand
B) When a fault occurs in the main system
55
For what purpose is emergency and backup pressurisation used on the ground?
A) To replace the main pressurisation when a fault occurs
B) To assist during high user demand
C) For maintenance purposes when engines are not running
C) For maintenance purposes when engines are not running
56
How long does it take for the RAT to deploy once activated?
A) About 5 seconds
B) Less than a second
C) About 10 seconds
B) Less than a second
57
What does RAT stand for?
A) Ram Air Turbine
B) Rapid Air Transfer
C) Rotating Air Turbine
A) Ram Air Turbine
58
What does the Ram Air Turbine (RAT) provide when deployed?
A) Electrical and hydraulic power
B) Only electrical power
C) Only hydraulic power
A) Electrical and hydraulic power
59
What does PTU stand for?
A) Power Transfer Unit
B) Pump Transmission Unit
C) Pressure Transfer Unit
A) Power Transfer Unit
60
What two components make up a PTU?
A) Two hydraulic pumps
B) A hydraulic pump and a hydraulic motor
C) Two hydraulic motors
B) A hydraulic pump and a hydraulic motor
61
What is the primary function of a PTU?
A) To transfer hydraulic fluid between systems
B) To transfer power between two hydraulic systems
C) To increase hydraulic pressure
B) To transfer power between two hydraulic systems
62
Does the PTU transfer fluid from one hydraulic system to another?
A) Yes, it transfers fluid directly
B) No, it transfers power but not fluid
C) Only in one-directional PTUs
B) No, it transfers power but not fluid
63
What does ACMP stand for?
A) Alternating Current Motor Pump
B) Air Cooled Motor Pump
C) Auxiliary Control Motor Pump
A) Alternating Current Motor Pump
64
Can ACMPs serve as a primary source of hydraulic pressure?
A) Yes
B) No
A) Yes
65
What is the purpose of ground equipment in hydraulic systems?
A) To replace the engines
B) To pressurise the hydraulic system when aircraft systems are unavailable
C) To cool the hydraulic fluid
B) To pressurise the hydraulic system when aircraft systems are unavailable
66
What is the primary function of filters in an aircraft hydraulic system?
A) To increase fluid pressure
B) To clean hydraulic fluid and prevent foreign particles from remaining in the system
C) To reduce fluid temperature
B) To clean hydraulic fluid and prevent foreign particles from remaining in the system
67
What percentage of all system failures are due to contamination?
A) 50%
B) 85%
C) 25%
B) 85%
68
Which materials are hydraulic filters commonly made from?
A) Plastic and rubber
B) Wire mesh, stainless steel, micro glass, and cellulose paper
C) Copper and aluminum
B) Wire mesh, stainless steel, micro glass, and cellulose paper
69
Besides particulate matter, what other contaminants can some hydraulic filters separate from the fluid?
A) Only air
B) Air and water
C) Only oil
B) Air and water
70
Which type of hydraulic filter is considered to provide the best filtration quality?
A) Cellulose paper
B) Wire mesh
C) Micro glass
C) Micro glass
71
What size particles does a micro glass filter typically prevent from passing through?
A) Larger than 50 microns
B) Larger than 10 microns
C) Larger than 100 microns
B) Larger than 10 microns
72
What are the four main components of a hydraulic filter assembly?
A) Filter Head Assembly, Filter Bowl, Filter Element, Filter Bypass Valve
B) Filter Pump, Filter Bowl, Filter Screen, Filter Bypass Valve
C) Filter Head Assembly, Filter Screen, Filter Element, Filter Drain Plug
A) Filter Head Assembly, Filter Bowl, Filter Element, Filter Bypass Valve
73
What is the function of the filter bypass valve in a hydraulic filter assembly?
A) To filter smaller particles more effectively
B) To allow hydraulic flow to continue if the filter clogs
C) To enhance the filtration process by adding pressure
B) To allow hydraulic flow to continue if the filter clogs
74
What does a filter differential pressure indicator do when a filter element is clogged?
A) Alerts the pilot directly through the flight controls
B) Activates a visual or electrical warning and opens the bypass valve
C) Increases pressure to clear the clog in the filter
B) Activates a visual or electrical warning and opens the bypass valve
75
What happens when a filter becomes clogged in a system equipped with a differential pressure indicator?
A) The system automatically shuts down.
B) A warning light on the flight deck illuminates.
C) A red button or pin pops out to indicate the filter is clogged.
C) A red button or pin pops out to indicate the filter is clogged.
76
When the filter bypass valve activates and allows fluid to bypass the filter, what should be done?
A) The hydraulic fluid is dirty and should be drained and replaced.
B) The system is functioning normally and no action is needed.
C) The filter element can be ignored as the bypass valve protects the system.
A) The hydraulic fluid is dirty and should be drained and replaced.
77
When the red indicator button or pin pops out on a filter differential pressure indicator, what does it mean?
A) The filter element must be cleaned or replaced.
B) The system is operating normally.
C) The filter bypass valve is closed.
A) The filter element must be cleaned or replaced.
78
When the filter bypass valve activates and allows fluid to bypass the filter, what should be done?
A) The hydraulic fluid is dirty and should be drained and replaced.
B) The system is functioning normally and no action is needed.
C) The filter element can be ignored as the bypass valve protects the system.
A) The hydraulic fluid is dirty and should be drained and replaced.
79
What are the three common types of pressure relief valves?
A) Ball type, Sleeve type, Poppet type
B) Diaphragm type, Ball type, Rotary type
C) Poppet type, Needle type, Diaphragm type
A) Ball type, Sleeve type, Poppet type
80
What is the primary function of a pressure relief valve?
A) To increase hydraulic pressure in the system
B) To limit pressure by discharging fluid when pressure exceeds a set value
C) To filter contaminants from the hydraulic fluid
B) To limit pressure by discharging fluid when pressure exceeds a set value
81
What is one purpose of a pressure regulator in a hydraulic system with constant delivery pumps?
A) To increase fluid flow
B) To maintain system operating pressure within a set range
C) To shut down the pump completely
B) To maintain system operating pressure within a set range
82
What is the main function of a pressure-reducing valve?
A) To increase system pressure
B) To lower the normal system operating pressure by a specified amount
C) To stop fluid flow
B) To lower the normal system operating pressure by a specified amount
83
What are the three main classes of hydraulic seals?
A) O-rings, washers, bolts
B) Packings, gaskets, wipers
C) Screws, nuts, washers
B) Packings, gaskets, wipers
84
Hydraulic seals used internally on sliding or moving assemblies are called:
A) Gaskets
B) Packings
C) Wipers
B) Packings
85
What is the main purpose of hydraulic seals?
A) To increase fluid pressure
B) To prevent fluid from passing a certain point and keep air/dirt out
C) To speed up fluid flow
B) To prevent fluid from passing a certain point and keep air/dirt out
86
What are the three main types of packing seals?
A) V-rings, U-rings, and O-rings
B) Gaskets, wipers, and seals
C) Bolts, nuts, and washers
A) V-rings, U-rings, and O-rings
87
Which of the following are types of hydraulic pressure control valves?
A) Relief valve, Reduction valve, Regulating valve
B) Relief valve, Expansion valve, Flow valve
C) Check valve, Reduction valve, Pressure switch
A) Relief valve, Reduction valve, Regulating valve
88
What does the red stripe on an O-ring indicate?
A) Hydraulic fluid compatibility
B) Fuel compatibility
C) Vapour compatibility
B) Fuel compatibility
89
What colour stripe indicates hydraulic fluid compatibility on an O-ring?
A) Red
B) Blue
C) Green
B) Blue
90
What is the function of a wiper seal?
A) To seal where stroking or rotational movements occur
B) To prevent dirt entry and protect piston shafts from scoring
C) To support O-rings under high pressure
B) To prevent dirt entry and protect piston shafts from scoring
91
What are gaskets primarily used for in hydraulic systems?
A) Dynamic sealing between moving parts
B) Static seals between two flat surfaces
C) Supporting O-rings under pressure
B) Static seals between two flat surfaces
92
What type of tools should be avoided when removing or installing O-rings?
A) Rounded plastic tools
B) Pointed or sharp-edged tools
C) Special seal installation tools
B) Pointed or sharp-edged tools
93
What is the main function of a shut-off valve?
A) To increase hydraulic pressure
B) To shut off fluid flow to a system or component
C) To filter hydraulic fluid
B) To shut off fluid flow to a system or component
94
What are the two main types of selector valves?
A) Poppet and spool
B) Open centre and closed centre
C) Rotary and plug
B) Open centre and closed centre
95
What is the primary function of a sequence valve in a hydraulic system?
A) To shut off fluid flow completely
B) To control the order of operation between two branches in a circuit
C) To increase system pressure
B) To control the order of operation between two branches in a circuit
96
What is the purpose of a priority valve in a hydraulic system?
a) Gives priority to critical hydraulic subsystems when pressure is low
b) Disconnects hydraulic lines to prevent fluid loss
c) Opens to allow fluid flow only when manually actuated
a) Gives priority to critical hydraulic subsystems when pressure is low
97
Why are quick disconnect valves used in hydraulic lines?
a) To prevent loss of fluid when units are removed
b) To regulate pressure between different system branches
c) To control the sequence of actuator operations
a) To prevent loss of fluid when units are removed
98
What is the primary function of a non-return valve in an aircraft hydraulic system?
a) Allows fluid to flow in both directions
b) Allows fluid to flow in only one direction and prevents flow in the opposite direction
c) Regulates system pressure automatically
b) Allows fluid to flow in only one direction and prevents flow in the opposite direction
99
What is the main purpose of a hydraulic fuse in a hydraulic system?
a) To regulate system pressure
b) To shut off fluid flow when a sudden increase in flow is detected
c) To filter hydraulic fluid
b) To shut off fluid flow when a sudden increase in flow is detected
100
What is the main function of a hydraulic actuating cylinder?
a) To regulate hydraulic fluid flow
b) To convert fluid pressure into mechanical force for linear motion
c) To store hydraulic fluid
b) To convert fluid pressure into mechanical force for linear motion
101
What are the two major types of hydraulic actuating cylinders?
a) Rotary and linear
b) Single-action and double-action
c) Piston and diaphragm
b) Single-action and double-action
102
What is the main purpose of a hydraulic fuse in a hydraulic system?
a) To regulate system pressure
b) To shut off fluid flow when a sudden increase in flow is detected
c) To filter hydraulic fluid
b) To shut off fluid flow when a sudden increase in flow is detected
103
What is the main function of a hydraulic actuating cylinder?
a) To regulate hydraulic fluid flow
b) To convert fluid pressure into mechanical force for linear motion
c) To store hydraulic fluid
b) To convert fluid pressure into mechanical force for linear motion
104
What are the two major types of hydraulic actuating cylinders?
a) Rotary and linear
b) Single-action and double-action
c) Piston and diaphragm
b) Single-action and double-action
105
What is the primary purpose of heat exchangers in an aircraft hydraulic system?
a) To increase fluid pressure
b) To cool hydraulic fluid before it returns to the reservoir
c) To filter contaminants from hydraulic fluid
b) To cool hydraulic fluid before it returns to the reservoir
106
What are the two main types of hydraulic lines used in aircraft hydraulic systems?
a) Pipes and valves
b) Pipes and hoses
c) Tubes and cylinders
b) Pipes and hoses
107
What is the purpose of the sleeve in a disconnecting pipe fitting?
a) To provide flexibility
b) To fit over the pipe and help form a leak-proof joint
c) To increase pressure
b) To fit over the pipe and help form a leak-proof joint
108
How are hose fittings classified according to pressure suitability?
a) Low, medium, and high
b) Small, medium, large
c) Soft, hard, and rigid
a) Low, medium, and high
109
How are hydraulic lines marked for easy identification?
a) Using different shapes of fittings
b) With identification markings that show the system, line function, and fluid flow direction
c) By varying the material of the lines
b) With identification markings that show the system, line function, and fluid flow direction
110
What are the primary parameters monitored in a hydraulic system on a flight deck?
a) Fluid quantity and density
b) Fluid pressure and temperature
c) Reservoir size and weight
b) Fluid pressure and temperature
111
What mechanism is used to monitor hydraulic fluid quantity at the reservoir?
a) Thermostat
b) Float gauge or sight glass
c) Pressure switch
b) Float gauge or sight glass
112
Which device is used to convert pressure into an electrical signal?
A) Pressure transducer
B) Pressure switch
C) Pressure alarm
A) Pressure transducer
113
What is a common type of pressure transducer?
A) Piezo switch
B) Strain gauge
C) Valve actuator
B) Strain gauge
114
What are the two main types of pressure sensors?
A) Pressure switches and pressure transducers
B) Pressure regulators and pressure valves
C) Pressure alarms and pressure gauges
A) Pressure switches and pressure transducers
115
What signals do hydraulic system sensors send to the flight deck?
A) Altitude, speed, and pressure
B) Pressure, temperature, and quantity
C) Voltage, current, and power
B) Pressure, temperature, and quantity
116
What color is used to indicate unsafe hydraulic system levels on the flight deck display?
A) Red
B) Amber
C) Blue
B) Amber
117
What two parts make up a hydro-mechanical flight control system?
A) Electronic controls and sensors
B) Mechanical circuit and hydraulic circuit
C) Hydraulic pumps and computers
B) Mechanical circuit and hydraulic circuit
118
What kind of actuator may be used in an Electro Hydrostatic Actuator system?
A) Rotary or linear
B) Only rotary
C) Only linear
A) Rotary or linear
