For normal purposes, hydraulic fluid is considered to be. Highly compressible Relatively incompressible Resistant to cyclic compressibility surges.
With a system pressure of 3000 psi, the work done by a jack with a piston area of 4 inches compared with a jack of piston area of 2 inches. Twice as much The same Half as much.
A pressure of 100 psi acts on two hydraulic jacks, one with a piston area of 2 inches, the other with a piston area of 4 inches The smaller jack will exert a force of 200 lbs, and the larger jack a force of 400lbs The smaller jack will exert a force of 50lbs, and the larger jack a force of 100lbs The smaller jack will exert a force of 100lbs,and the larger jack a force of 50 lbs.
Under the same system pressure, the force applied by the hydraulic jack, of 50 mm piston area will be Equal to that of a similar jack of 25 mm piston area Half that applied by a similar jack of 25 mm piston area Twice that applied by a similar jack of 25 mm piston area.
If the system pressure is 1800 psi,the force provided by a 6 inch area jack, if compared to the force provided by a jack of 2 inches area will be. Exactly the same 3600lbs greater 7200lbs greater.
A hydraulic pump Does not require a positive supply of hydraulic fluid, provided it is primed before use Does not require a positive supply of hydraulic fluid, as it is self-priming Always require a positive supply of hydraulic fluid to avoid pump cavitation
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The output of a constant delivery pump is regulated by
A compensator built into the pump An accumulator An automatic cut off valve
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A variable stroke pump A constant pressure pump A constant volume pump A constant flow pump
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Hand pump in aircraft hydraulic system are generally Rotary acting Single acting Double acting.
Hand pumps are usually fitted to aircraft systems for Ground servicing and as an emergency power supply To maintain the level of fluid in the reservoir To ensure that the gas charge in both the accumulator and the reservoir remain constant
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A double acting hand pump is one which Provides twice the normal pressure on each stroke Provides pressure once every two strokes Provides pressure on each stroke.
In a hand pump system, how many non-return valves are required
One Two Four.
Which of the following device have an actuating cylinder A device for converting hydraulic pressure to mechanical motion A device for transforming mechanical motion to hydraulic pressure A device for controlling the direction of flow of hydraulic fluid.
A powered flying control unit is normally Fitted with a single acting actuator Fitted with a balanced actuator Fitted with a differential actuator.
A non-return valve is designed to close If inlet pressure exceeds outlet pressure If the system pressure exceeds a pre-set value If the inlet pressure supply to the valve fails
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The automatic cut-out valve controls The pressure output of the pump The sum of the main system liquid and air pressures The flow of hydraulic fluid from the reservoir.
A thermal relief valve
Senses fluid temperature change Senses fluid pressure Provides cooling for the fluid.
A shuttle valve Ensures that the hydraulic pump circuit is self-regulation Is a self-lapping non-return valve Allows two possible sources of pressure to operate one unit.
Thermal relief valves are set to The same pressure as the automatic cut-out valve “cut in” The same pressure as the automatic cut-out valve “cut out” A higher pressure than the automatic cut-out valve “cut out”
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Restrictor valves are used to Control the rate of system operation Restrict the rate of pressure build-up Limit the maximum system pressure.
How is hydraulic pump wear reduced by an automatic cut-out valve By preventing hydraulic locking and fluid aeration By maintaining pump pressure to a minimum By maintaining a cooling and lubricating flow through the pump at all times during operation
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Which of the following would cause the main pressure relief valve to open An excessive rate of system operation A failure of the automatic cut-out valve Excessive initial pressure from the accumulator.
The process of undercarriage doors operating in the correct order in respect of the rest of the system is normally controlled by Restrictor valves Selector valves Sequence valves.
An automatic cut-out valve is situated Between the pump and the reservoir Between the pressure manifold and the accumulator Between the power pump and the pressure manifold
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Thermal expansion in a hydraulic system is provided for by A thermal relief valve A reservoir The pressure relief valve.
The purpose of a reservoir is To pressurize the system after the failure of an engine driven pump To make the fluid content easily accessible and visible To compensate for actuator displacements, thermal expansion and small leakages
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One reason for pressuring a reservoir with air is To prevent cavitation of the pump To prevent the formation of airlocks in the system when the pump is idling To prevent any losses due to leaks and thermal expansion
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A stack pipe in a reservoir supplying an engine driven pump, and an emergency hand pump, is included to Prevent an aeration of the hydraulic fluid Retain a reserve supply of fluid for emergency use Prevent contamination of the pump by sludge.
If no quantity gauge is included, a hydraulic reservoir should be approximately
Half full Three quarters full Completely full.
Before the charge pressure of an accumulator can be accurately checked The automatic cut-out valve must be opened The pressure relief valve must be operated The pressure release valve must be operated.
A hydraulic accumulator Is always fitted with the gas section uppermost Is always fitted with the fluid section uppermost Can be fitted horizontally.
The floating diaphragm in a hydraulic accumulator Indicates the fluid content in the accumulator Increases the system pressure Maintains a seal between the fluid and the air charge
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The effect of low air pressure in an accumulator would be System pressure would be slow to build up All actuators would have rapid movements System pressure would fluctuate rapidly.
In an aircraft system, the normal operating pressure is 1800 psi. The accumulator is air-charged initially to 1000psi. When the system is activated and reaches normal operating pressure, what will the pressure gauge indicate? 2800 psi 1800 psi 1000 psi.
DTD 585 hydraulic fluid is Red in colour and mineral based Green in colour and castor based Green in colour and mineral based.
Hydraulic fluids approved for aircraft use May be freely mixed for use I any aircraft system May not be freely mixed, but different fluids may be used with the same type of
seal Have a particular seal material specified for each different type
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The reason for bleeding a hydraulic system is to Remove all sludge and contaminants from the system To remove all the fluid from the system To remove all air from the fluid lines.
What materials are seals made from for use in a mineral oil system
Synthetic rubber PVC Natural rubber.
An air bottle included in a hydraulic system is for Re-charging accumulator air pressure Supplying emergency services Maintaining reservoir pressure.
A pressure gauge fitted to a main pressure line indicates
Fluid pressure Air pressure Fluid and air pressure combined
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If the element of a main filter becomes blocked A relief, or by-pass, valve will open and allow filtered fluid to by-pass the element All fluid will be prevented from passing the filter Unfiltered fluid will be allowed to by-pass the element.
Sluggish operation of hydraulic services is caused by
Air trapped in the reservoir under pressure Air at to high a pressure in the system accumulator Air in the system
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Fluid leakage around the ram of a hydraulic actuator is most likely to be caused by Air in the fluid The failure of a seal Improper maintenance.
The normal operating pressure of an aircraft hydraulic system is between 100 and 1000 psi 1000 and 4000 psi 500 and 1000 psi.
An open center system causes A heavy load on the hydraulic pump The accumulator to open the automatic cut-out valve A high pressure return of the fluid to the reservoir.
With the flap selector in the down position, the flaps fail to lower. This could be caused by A split accumulator diaphragm An unserviceable relief valve A leak in the upline.
A Power pack incorporates an accumulator which Controls the pressure delivered to the piston jacks Controls the amount of fluid delivered to the piston jacks Controls the operation of the pump.
In the event of a reduction in the supply pressure, the pressure maintaining valve reserves pressure for the Wing flap system Powered flying controls Undercarriage system
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A powered flying control unit is normally Fitted with a single acting actuator Fitted with a balanced actuator Fitted with a differential area jack assembly
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