Hydraulic fluids must have the following characteristics .1 thermal ? [ Report OACI ]

Question 33-1 : 1 2 3 and 4 1 2 5 and 7 2 3 4 and 5 1 3 4 and 6

exemple 133 1, 2, 3 and 4. — 1, 2, 3 and 4.

Hydraulic fluids ?

Question 33-2 : Are irritating to e and skin are irritating to e and skin and cause high fire risk cause high fire risk do not require special care

exemple 137 Are irritating to eyes and skin. — Are irritating to eyes and skin.

Hydraulic fluids used in systems of large modern airliners are ?

Question 33-3 : Phosphate ester base fluids water base fluids vegetable base fluids mineral base fluids

exemple 141 Phosphate ester base fluids. — Phosphate ester base fluids.

Hydraulic power is a function of ?

Question 33-4 : System pressure and volume flow pump rpm only system pressure and tank capacity pump size and volume flow

exemple 145 System pressure and volume flow. — System pressure and volume flow.

Large transport aeroplane hydraulic systems usually operate with a system ?

Question 33-5 : 3000 psi 4000 psi 2000 psi 1000 psi

exemple 149 3000 psi. — Hydraulic system of the a380 is 5000 psi instead of 3000 psi but usually hydraulic systems operate with a system pressure of 3000 psi 3000 psi.

In hydraulic systems of large modern transport category aircraft the fluids ?

Question 33-6 : Synthetic oil mineral oil water and glycol vegetable oil

exemple 153 Synthetic oil. — Synthetic oil.

The type of hydraulic oil used in modern hydraulic systems is ?

Question 33-7 : Synthetic oil vegetable oil mixture of mineral oil and alcohol mineral oil

exemple 157 Synthetic oil — Synthetic oil

In a modern hydraulic system 'hydraulic fuses' can be found their function is ?

Question 33-8 : To prevent total system loss in case of a leaking hydraulic line to switch to the secondary system in case of a leak in the primary brake system to isolate a part of the system and protect it against accidental pollution to allow by passing of a hydraulic pump in case it is subject to excessive pressure without further damage to the system

exemple 161 To prevent total system loss in case of a leaking hydraulic line. — In hydraulic systems a fuse is a component which prevents the sudden loss of hydraulic fluid pressure it is a safety feature designed to allow systems to continue operating or at least to not fail catastrophically in the event of a system breach it does this by stopping the flow of hydraulic fluid through itself if the flow exceeds a threshold . 819.boeing 737 hydraulic fuses .the term 'fuse' is used here in analogy with electrical fuses which perform a similar function To prevent total system loss in case of a leaking hydraulic line.

In a hydraulic system the reservoir is pressurized in order to ?

Question 33-9 : Prevent pump cavitation reduce fluid combustibility seal the system keep the hydraulic fluid at optimum temperature

exemple 165 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 33-10 : Switch hydraulically operated units to the most appropriate pressure supply guard systems against overpressure reduce pump loads shut down systems which are overloaded

exemple 169 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 33-11 : Purple pink blue red

The function of a hydraulic selector valve is to ?

Question 33-12 : 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 177 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 33-13 : An actuator or jack a hydraulic pump a pressure regulator an accumulator

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

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

Question 33-14 : Check valve flow control valve distribution valve shutoff valve

exemple 185 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 33-15 : Prevent cavitation in the pump prevent overheating of the pump prevent vapour locking ensure sufficient pump output

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

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

Question 33-16 : 100 n 1000 n 20 n 1 n

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

Question 33-17 : 1500 psi 2500 psi 1000 psi 500 psi

exemple 197 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 33-18 : An increased fluid temperature a decreased fluid temperature an increased fluid pressure fluid loss

exemple 201 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 33-19 : The aeroplane's hydraulic system the master cylinders the brake actuators pressure to the rudder pedals

exemple 205 The aeroplane's hydraulic system. — The aeroplane's hydraulic system.

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

Question 33-20 : Decrease slightly always remain the same initially increase with system pressurisation increase as ambient temperature decreases

exemple 209 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 33-21 : Store fluid under pressure increase pressure surges within the system reduce fluid temperature and pressure reduce fluid temperature only

exemple 213 Store fluid under pressure. — Store fluid under pressure.

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

Question 33-22 : 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 217 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 33-23 : 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 221 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 33-24 : A high pressure relief valve a standby hydraulic pump an accumulator auxiliary hydraulic motors

exemple 225 A high pressure relief valve. — 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 A high pressure relief valve.

The ram air turbine rat provides emergency hydraulic power for ?

Question 33-25 : 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 229 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 33-26 : 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

exemple 233 The pump output pressure being insufficient. — The pressure transmitter is located at the pump output The pump output pressure being insufficient.

For an aeroplane hydraulic supply circuit the correct statement is ?

Question 33-27 : 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 237 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 33-28 : By bleed air from the engine in flight only by the air conditioning system by an auxiliary system

A pressure regulator is used in a hydraulic system ?

Question 33-29 : 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 245 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 33-30 : 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

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

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

Question 33-31 : 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 253 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 33-32 : Pressure fluid temperature and quantity pressure and hydraulic pump output pressure and fluid viscosity pressure and rpm of the hydraulic pump

exemple 257 Pressure, fluid temperature and quantity. — Pressure, fluid temperature and quantity.

The purpose of an accumulator in a hydraulic system is ?

Question 33-33 : 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 261 To damp the fluid pressure variations. — To damp the fluid pressure variations.

The viscosity of a hydraulic fluid should be ?

Question 33-34 : 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 265 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 33-35 : N°2 n°4 n°3 n°1

exemple 269 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 33-36 : To damp pressure surges in the system to store fluid to increase the flow to act as a pressure relief valve

exemple 273 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 33-37 : At the pumps in the reservoirs at the actuators at the coolers

exemple 277 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 33-38 : 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 281 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 33-39 : Fluctuate with accumulator pressure always remain the same initially increase with system pressurisation increase as ambient temperature decreases

exemple 285 Fluctuate with accumulator pressure. — Fluctuate with accumulator pressure.

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

Question 33-40 : 1 3 2 4 1 4 2 3

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