In a hydraulic system the reservoir is pressurized in order to ? [ Session helipad ]

Question 21-1 : Prevent pump cavitation reduce fluid combustibility seal the system keep the hydraulic fluid at optimum temperature

exemple 121 Prevent pump cavitation. — Cavitation occurs when a liquid moves within tubing or pipes at very fast speeds causing the absolute pressure of the liquid to drop drastically this process occurs with little loss of heat if the absolute pressure drops below the vapour pressure of the liquid cavitation will form this phenomenon is more serious in viscous liquids than in thin liquids .cavitation causes separation of gases that are within the liquid such as air or water vapour from the liquid itself bubbles would form then collapse .in the case of a liquid entering the suction side of a pump the pressure would be low for the liquid to move from one place to another it would have to expend energy thus causing a further decrease in pressure .if you pressurize the hydraulic fluid entering in the hydraulic pump you will avoid cavitation in the pump Prevent pump cavitation.

Shuttle valves will automatically ?

Question 21-2 : Switch hydraulically operated units to the most appropriate pressure supply guard systems against overpressure reduce pump loads shut down systems which are overloaded

exemple 125 Switch hydraulically operated units to the most appropriate pressure supply. — The shuttle valve .sometimes fluid must come from more than one source to meet the demands of a complex system at other times an emergency system might be needed to provide pressure if the normal system fails the emergency system will usually only actuate essential components .the shuttle valve can isolate the normal system from an alternate or emergency one a typical shuttle valve contains three ports . normal system inlet. alternate system inlet. an outlet.inside the shuttle valve there is a sliding part predictably called the shuttle whose purpose is to seal off an inlet port which itself will contain a shuttle seat . 820.when a shuttle valve is in its normal position fluid can flow freely from the normal system inlet port to the actuating unit the shuttle is seated against the alternate system inlet port and held there by normal system pressure where it remains until the alternate system is activated fluid under pressure is then directed from the alternate system to the shuttle valve forcing the shuttle to seal off the normal inlet port fluid from the alternate system then has a free flow to the outlet port Switch hydraulically operated units to the most appropriate pressure supply.

The colour of a fresh synthetic hydraulic fluids is ?

Question 21-3 : Purple pink blue red

The function of a hydraulic selector valve is to ?

Question 21-4 : Direct system pressure to either side of the piston of an actuator select the system to which the hydraulic pump should supply pressure automatically activate the hydraulic system discharge some hydraulic fluid if the system pressure is too high

exemple 133 Direct system pressure to either side of the piston of an actuator. — A selector or control valve enabling the operator to select the direction of the flow of fluid to the required service and providing a return path for the oil to the reservoir . 821 Direct system pressure to either side of the piston of an actuator.

The component that converts hydraulic pressure into linear motion is called ?

Question 21-5 : An actuator or jack a hydraulic pump a pressure regulator an accumulator

exemple 137 An actuator or jack. — The purpose if to convert fluid flow into linear or rotary motion they vary in size and construction depending on the operating loads but all consist of an outer cylinder in which slides a piston and seal assembly attached to the piston is a piston rod which passes through a gland seal fitted into the end of the cylinder An actuator or jack.

The hydraulic device which functionality is comparable to an electronic diode ?

Question 21-6 : Check valve flow control valve distribution valve shutoff valve

exemple 141 Check valve. — A diode is a one way electricity gate actually a diode means a device that has two electrodes but the word has come to mean a one way electricity valve . 822.the most common function of a diode is to allow an electric current to pass in one direction and to block it in the opposite direction thus the diode can be thought of as an electronic version of a check valve Check valve.

Hydraulic fluid entering the hydraulic pump is slightly pressurised to ?

Question 21-7 : Prevent cavitation in the pump prevent overheating of the pump prevent vapour locking ensure sufficient pump output

exemple 145 Prevent cavitation in the pump. — Cavitation occurs when a liquid moves within tubing or pipes at very fast speeds causing the absolute pressure of the liquid to drop drastically this process occurs with little loss of heat if the absolute pressure drops below the vapour pressure of the liquid cavitation will form this phenomenon is more serious in viscous liquids than in thin liquids .cavitation causes separation of gases that are within the liquid such as air or water vapour from the liquid itself bubbles would form then collapse .in the case of a liquid entering the suction side of a pump the pressure would be low for the liquid to move from one place to another it would have to expend energy thus causing a further decrease in pressure .if you pressurize the hydraulic fluid entering in the hydraulic pump you will avoid cavitation in the pump Prevent cavitation in the pump.

In the hydraulic press schematically shown what balancing force would be acting ?

Question 21-8 : 100 n 1000 n 20 n 1 n

Assuming an accumulator is pre charged with air to 1000 psi and the hydraulic ?

Question 21-9 : 1500 psi 2500 psi 1000 psi 500 psi

exemple 153 1500 psi. — Part of an accumulator's job is to store energy in the form of hydraulic fluid under pressure that can be used for short time if the main system fails or needs help at peak times .pressure gauges installed in hydraulic and pneumatic systems are used to indicate existing hydraulic and pneumatic pressures the accumulator gauge will read 1500 psi and if the main system fails it will read 1000 psi 1500 psi.

Internal leakage in a hydraulic system will cause ?

Question 21-10 : An increased fluid temperature a decreased fluid temperature an increased fluid pressure fluid loss

exemple 157 An increased fluid temperature. — As there is internal leakage the hyd pump will cycle on and off depending on pump type to maintain system pressure increasing friction with the pump and fluid thus increasing the fluid temp An increased fluid temperature.

On large aeroplanes equipped with power brakes the main source of power is ?

Question 21-11 : The aeroplane's hydraulic system the master cylinders the brake actuators pressure to the rudder pedals

exemple 161 The aeroplane's hydraulic system. — The aeroplane's hydraulic system.

When powering up a hydraulic system the level in the reservoir will ?

Question 21-12 : Decrease slightly always remain the same initially increase with system pressurisation increase as ambient temperature decreases

exemple 165 Decrease slightly. — The air occupies space that would otherwise be occupied by hydraulic fluid thus when the hydraulic system becomes pressurized some fluids flows into the different pipes Decrease slightly.

An accumulator in a hydraulic system will ?

Question 21-13 : Store fluid under pressure increase pressure surges within the system reduce fluid temperature and pressure reduce fluid temperature only

exemple 169 Store fluid under pressure. — Store fluid under pressure.

In the typical hydraulic system represented in the graphic assuming hydraulic ?

Question 21-14 : A condition of hydraulic lock exists and no movement of the piston will take place the piston is free to move in response to external forces since pressures are equal the piston moves to the left due to pressure acting on differential areas the piston moves to the right due to equal pressure acting on differential areas

exemple 173 A condition of hydraulic lock exists and no movement of the piston will take place. — Img826.a condition of hydraulic lock exists and no movement of the piston will take place A condition of hydraulic lock exists and no movement of the piston will take place.

A hydraulic shuttle valve ?

Question 21-15 : Enables an alternate supply to operate an actuator is a non return valve allows two units to be operated by one pressure source regulates pump delivery pressure

exemple 177 Enables an alternate supply to operate an actuator. — The shuttle valve .sometimes fluid must come from more than one source to meet the demands of a complex system at other times an emergency system might be needed to provide pressure if the normal system fails the emergency system will usually only actuate essential components .the shuttle valve can isolate the normal system from an alternate or emergency one a typical shuttle valve contains three ports . normal system inlet. alternate system inlet. an outlet.inside the shuttle valve there is a sliding part predictably called the shuttle whose purpose is to seal off an inlet port which itself will contain a shuttle seat . 820.when a shuttle valve is in its normal position fluid can flow freely from the normal system inlet port to the actuating unit the shuttle is seated against the alternate system inlet port and held there by normal system pressure where it remains until the alternate system is activated fluid under pressure is then directed from the alternate system to the shuttle valve forcing the shuttle to seal off the normal inlet port fluid from the alternate system then has a free flow to the outlet port Enables an alternate supply to operate an actuator.

To protect against excessive system pressure a hydraulic system usually ?

Question 21-16 : A high pressure relief valve a standby hydraulic pump an accumulator auxiliary hydraulic motors

The pressure relief valve is there to dump fluid back to the reservoir when pressure in the system gets too high as it will do when the system is not being used and the engine driven pump is working all the time . 827

The ram air turbine rat provides emergency hydraulic power for ?

Question 21-17 : Flight controls in the event of loss of engine driven hydraulic power nose wheel steering after the aeroplane has landed undercarriage selection and automatic brake system flap extension only

exemple 185 Flight controls in the event of loss of engine driven hydraulic power. — Img828.a ram air turbine rat is a small turbine that is connected to a hydraulic pump or electrical generator installed in an aircraft and used as a power source the rat generates power from the airstream due to the speed of the aircraft Flight controls in the event of loss of engine driven hydraulic power.

A hydraulic low pressure alert is the first indication of ?

Question 21-18 : The pump output pressure being insufficient the reservoir level being at a minimum acceptable level a leak in the reservoir return line the hydraulic system accumulator becoming deflated

The pressure transmitter is located at the pump output

For an aeroplane hydraulic supply circuit the correct statement is ?

Question 21-19 : The accumulators constitute a reserve of hydraulic fluid maintained under pressure by a pneumatic back pressure air or nitrogen the pumps are always electric due to the high pressures which they must deliver 140 to 210 kg/cm² the regulation system deals only with emergency operation and is not applied to all hydraulic services but only those considered as essential the security components comprise the filters the pressure relief valves the by passes and the fire shut off valve

exemple 193 The accumulators constitute a reserve of hydraulic fluid maintained under pressure by a pneumatic back pressure (air or nitrogen). — The accumulators constitute a reserve of hydraulic fluid maintained under pressure by a pneumatic back pressure (air or nitrogen).

The reservoirs of a hydraulic system can be pressurized ?

Question 21-20 : By bleed air from the engine in flight only by the air conditioning system by an auxiliary system

exemple 197 By bleed air from the engine. — By bleed air from the engine.

A pressure regulator is used in a hydraulic system ?

Question 21-21 : In conjunction with a constant delivery type pump in conjunction with a variable delivery type pump to ensure that an equal pressure flow is delivered to critical components such as servo actuators as an interface between the system and the cockpit indicators

exemple 201 In conjunction with a constant delivery type pump. — A constant delivery pump forces a fixed or unvarying quantity of fluid through the outlet port during each revolution of the pump .the pressure regulator unloads or relieves the power driven pump when the desired pressure in the system is reached thus it is often referred to as an unloading valve .when a constant delivery type pump is being operated and pressure in the line between the pump and selector valve builds up to a desired point a valve in the pressure regulator automatically opens and fluid is bypassed back to the reservoir In conjunction with a constant delivery type pump.

Filters in hydraulic systems often incorporate pop out indicators to ?

Question 21-22 : Warn of an impending by pass situation indicate that the filter is clogged and unfiltered oil is passing around the system warn of a hydraulic system overheat indicate that the filter is due maintenance

exemple 205 Warn of an impending by-pass situation. — Filters are necessary in hydraulic systems for filtering out contamination and debris . 829.a filter may include a filter bypass provision a filter bypass allows fluid to flow around bypass the filter when the pressure across the filter is high i e filter is clogged . 830.a bypass functions similar to a priority valve where the pressure overcomes a spring when the pressure is sufficiently high Warn of an impending by-pass situation.

Maximum power output and low mass of aeroplane hydraulic systems can be ?

Question 21-23 : High system pressure and low volume flow medium system pressure and low volume flow medium system pressure and high volume flow low system pressure and high volume flow

exemple 209 High system pressure and low volume flow. — High system pressure and low volume flow.

Parameters to monitor a hydraulic system in the cockpit can be ?

Question 21-24 : Pressure fluid temperature and quantity pressure and hydraulic pump output pressure and fluid viscosity pressure and rpm of the hydraulic pump

exemple 213 Pressure, fluid temperature and quantity. — Pressure, fluid temperature and quantity.

The purpose of an accumulator in a hydraulic system is ?

Question 21-25 : To damp the fluid pressure variations to eliminate the fluid flow variations to bypass the pumps in the hydraulic system to enable the starting of some devices

exemple 217 To damp the fluid pressure variations. — To damp the fluid pressure variations.

The viscosity of a hydraulic fluid should be ?

Question 21-26 : The lowest to minimize power consumption and resistance to flow the lowest to provide excellent lubrication properties the highest to minimize power consumption and resistance to flow the highest to provide excellent lubrication properties

exemple 221 The lowest to minimize power consumption and resistance to flow. — The viscosity must be as low as possible to limit the power required for the operation of the system reducing the resistance of the flow The lowest to minimize power consumption and resistance to flow.

The hydraulic systems which works correctly is shown in the figure . 831 ?

Question 21-27 : N°2 n°4 n°3 n°1

exemple 225 N°2. — The non return valve the directional arrow after the pumps are unidirectional flow devices used primarily in hydraulic systems to eliminate potential damage caused by fluid back pressure .diagram n°2 is the only one correct N°2.

One of the functions of an accumulator in a hydraulic system is ?

Question 21-28 : To damp pressure surges in the system to store fluid to increase the flow to act as a pressure relief valve

exemple 229 To damp pressure surges in the system. — The function of accumulator in hydraulic system is to receive and store excess oil pumped through the system which is used to compensate sudden increase in loads To damp pressure surges in the system.

In a hydraulic system overheat detectors are mostly installed ?

Question 21-29 : At the pumps in the reservoirs at the actuators at the coolers

exemple 233 At the pumps. — The overheat detector is fitted at the pump to give indication of possible pump failure . 832. t for the temperature probe location q for quantity p for pressure.the electric motor driven pumps do a large part of the work to produce flow for the hydraulic system the harder they work the hotter they get .the engine driven pumps are not fitted with an overheat detector since the engines already have overheat and fire detection systems At the pumps.

Which of these statements about an aeroplane's hydraulic system is correct ?

Question 21-30 : The filters the pressure relief valve s the by pass valve s and the fire shut off valve are safety features installed in the system the pumps are always electrically driven because they need to deliver a high pressure of 3000 psi a hydraulic leak in a return line does not affect the functioning of the hydraulic system the hydraulic reservoir contains a membrane and is pressurised by nitrogen on one side of this membrane

exemple 237 The filters, the pressure relief valve(s), the by-pass valve(s), and the fire shut-off valve are safety features installed in the system. — The filters, the pressure relief valve(s), the by-pass valve(s), and the fire shut-off valve are safety features installed in the system.

The level in a hydraulic reservoir will ?

Question 21-31 : Fluctuate with accumulator pressure always remain the same initially increase with system pressurisation increase as ambient temperature decreases

Purposes of an accumulator in an hydraulic system are .1 to damp pressure ?

Question 21-32 : 1 3 2 4 1 4 2 3

The purpose of an accumulator in an hydraulic system is to ?

Question 21-33 : Store energy store fluid cool the fluid store pressure

The type of hydraulic fluid which has the greatest resistance to cavitation is ?

Question 21-34 : Synthetic fluid mineral oil based fluid vegetable oil based fluid caster oil water and glycol based fluid

exemple 253 Synthetic fluid. — .cavitation occurs when a liquid moves within tubing or pipes at very fast speeds causing the absolute pressure of the liquid to drop drastically this process occurs with little loss of heat if the absolute pressure drops below the vapour pressure of the liquid cavitation will form this phenomenon is more serious in viscous liquids than in thin liquids .cavitation causes separation of gases that are within the liquid such as air or water vapour from the liquid itself bubbles would form then collapse .in the case of a liquid entering the suction side of a pump the pressure would be low for the liquid to move from one place to another it would have to expend energy thus causing a further decrease in pressure .the hydraulic fluid used will be synthetic because of the high temperatures involved and the lesser risk of cavitation compared other fluids mineral oil or vegetable oil based fluids Synthetic fluid.

Filtration in a hydraulic system is usually ensured by ?

Question 21-35 : Filters in both the pressure and return lines a filter in the pressure line only a filter on the return line only the use of sealed containers only during replenishment

exemple 257 Filters in both the pressure and return lines. — Filters in both the pressure and return lines.

The relationship between pressure force and area is ?

Question 21-36 : Force = pressure x area pressure = force x area pressure = area x distance force = volume / area

exemple 261 Force = pressure x area — Force = pressure x area

In a commercial transport aeroplane the landing gear normal operating system is ?

Question 21-37 : Hydraulically driven electrically driven mechanically driven pneumatically driven

exemple 265 Hydraulically driven. — Hydraulically driven.

Generally on modern jet transport aircraft how can the landing gear be extended ?

Question 21-38 : Mechanically electrically by hydraulic accumulators pneumatically

exemple 269 Mechanically. — Mechanically.

The type of brake unit found on most transport aeroplanes is a ?

Question 21-39 : Multiple disk brake belt brake drum type brake single disk brake

exemple 273 Multiple disk brake. — Img833 Multiple disk brake.

The reason for fitting thermal plugs to aeroplane wheels is that they ?

Question 21-40 : Release air from the tyre in the event of overheating prevent the brakes from overheating prevent heat transfer from the brake disks to the tyres release air from the tyre in the event of overpressure

exemple 277 Release air from the tyre in the event of overheating. — Tyres are fitted with thermal plug to release air from the tyre in the event of overheating after a landing or a rejected take off with overweight and overspeed conditions the tyres and brakes are extremely hot and thermal plug can malfunction on the video you can see a tyre explosion .vdo834 Release air from the tyre in the event of overheating.

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