BASIC HYDRAULICS – Air – DGCA Question Bank For Politics

#1. A force of 100N is applied to 2 separate jacks, the area of one is 0.02m2 and the other is 0.04m2:

the smaller jack will exert a pressure of 2,000Pa and the larger 4,000 Pa.

the smaller jack will exert a pressure of 5,000 Pa and the larger 2,500 Pa.

both jacks will move at the same speed.

both have the same load.

#2. A pre charge pressure of 1,000 bar of gas is shown on the accumulator gauge. The system is then pressurised to 1,500 bar, so the accumulator will read:

500 bar.

1,000 bar.

1,500 bar.

2,500 bar.

#3. The pressure gauge of an hydraulic system provides information regarding the pressure of:

the air in the accumulator.

the air and hydraulic fluid in the system.

the proportional pressure in the system.

the hydraulic fluid in the system.

#4. A shuttle valve:

is used to replace NRVs.

allows two supply sources to operate one unit.

allows one source to operate two units.

acts as a non-return valve.

#5. Def. Stan 91/48 is ---------- and is ------------- based:

red , mineral

red , synthetic

green, mineral

purple, synthetic

#6. A restrictor valve:

is used to restrict the number of services available after loss of system pressure.

controls the rate of movement of a service.

controls the rate of build up of pressure in the system.

controls the distance a jack moves.

#7. With a hyd lock there is:

flow, but no jack movement.

no flow but jack continues to move under gravitational effects.

no flow, jack is stationary.

constant flow.

#8. The hydraulic fluid is changed, but the wrong fluid is replaced. This would lead to:

high operating fluid temperature.

system failure from leaks and blocked filters, high temp and possible corrosion.

a rise in the reservoir fill level.

normal operation, it does not matter which fluid is used.

#9. Accumulator floating piston:

pushes the fluid up when being charged.

pushes the fluid down when being charged.

provides a seal between the gas and fluid.

prevents a hydraulic lock.

#10. A relief valve:

relieves below system pressure.

maintains pressure to a priority circuit.

relieves at its designed pressure.

prevents excessive pressure through increased fluid temperature.

#11. The primary purpose of a hydraulic reservoir is:

to compensate for leaks, displacement and expansion.

to allow a space into which spare fluid may be stored.

to indicate system contents.

to maintain fluid between a jack and the accumulator.

#12. With air in the hydraulic system you would:

ignore it because normal operation would remove it.

bleed the air out of the system.

allow the accumulator to automatically adjust itself.

expect it to operate faster.

#13. The pressure filter in a hydraulic system:

filters the fluid returning to the tank.

is fitted down stream of the pump.

can be by passed when maximum flow is required.

clears the fluid as it leaves the reservoir.

#14. Pascal’s law states that:

pressure is inversely proportional to load.

liquid is compressible.

oxygen can be used to charge the accumulators.

applied force acts equally in all directions.

#15. A constant pressure hydraulic pump is governed by:

an automatic cut out.

engine RPM.

a control piston.

a swash plate that senses the fluid temperature.

#16. A high pressure hydraulic pump:

needs a positive fluid supply.

does not need a positive fluid supply.

outlet pressure is governed by centrifugal force.

does not need a cooling fluid flow.

#17. Case drain filters are:

fitted to prevent debris from the reservoir reaching the system.

designed to allow hydraulic pump lubricating fluid to drain to atmosphere.

to enable pump lubricating fluid to be used to monitor pump condition.

fitted in the reservoir outlet.

#18. The purpose of an accumulator is to:

relieve excess pressure.

store fluid under pressure.

store compressed gas for tyre inflation.

remove air from the system.

#19. With a one way check valve (NRV):

flow stops when input pressure is greater than output pressure.

flow stops when the thermal relief valve off loads the hand pump.

flow starts when input pressure is less than output pressure.

flow stops when input pressure is less than output pressure.

#20. A restrictor valve is physically fitted in the:

u/c up line and flap up line.

u/c down line and flap up line.

u/c down line and flap down line.

supply line to the u/c retraction actuator.

#21. In the case of a failure of a cut-out valve:

a full flow relief valve is fitted down stream of it.

a full flow relief valve is fitted upstream of it.

a full flow relief valve is not required.

the terminal pressure will be controlled by adjusting the pump RPM.

#22. Hydraulic pressure of 3,000Pa is applied to an actuator, the piston area of which is 0.02m² and the same pressure is exerted on actuator whose area is 0.04m²:

both have the same force.

both jacks will move at the same speed.

the smaller jack will exert a force of 600N and the larger 1,200N.

the smaller jack will exert a force of 60N and the larger 120N.

#23. A separator in an accumulator:

isolates the gas from the fluid.

reduces the size of the accumulator required.

removes the dissolved gases from the fluid.

maintains the fluid level in the reservoir.

#24. In an operating hydraulic actuator the pressure of the fluid will be:

greatest near to the actuator due to the load imposed on the jack.

greatest at the opposite end to the actuator due to the load imposed on the actuator.

high initially, falling as the actuator completes its travel.

the same at all points.

#25. The contents of the hydraulic fluid reservoir are checked. They indicate that the reservoir is at the full level. The system is then pressurised. Will the contents level:

fall below the “full” mark.

fall to a position marked ‘full accs charged’.

remain at the same level.

rise above the “full” mark.

#26. A pressure maintaining or priority valve:

enables ground operation of services when the engines are off.

is used to ensure available pressure is directed to essential services.

is used to control pressure to services requiring less than system pressure.

is used to increase pressure in the system.

#27. A hydraulic lock occurs:

when the thermal RV operates.

when fluid by passes a system and returns to the tank.

when flow is stopped and the actuator is not able to move.

when fluid and air enters the cylinder and only fluid is allowed to bypass to the reservoir.

#28. In an enclosed system pressure is felt:

more at the piston head than the rest of the cylinder.

more at the cylinder end than the piston head.

more when the piston is moving than when it is stationary.

the same at both ends between the piston and the cylinder head.

#29. A non return valve:

can only be fitted if provided with a by pass selector.

closes if inlet pressure exceeds outlet pressure.

opens if inlet pressure equals outlet pressure.

closes if inlet pressure ceases.

#30. Low gas pressure in accumulator causes:

rapid jack movements.

no effect on system.

rapid pressure fluctuations while system is operating.

rapid and smooth operation of system.

#31. Hammering in system:

is normal and does not affect the systems efficiency.

is caused by pipe diameter fluctuations.

is an indication that a further selection is necessary.

is detrimental to the system.

#32. The specification of hydraulic fluids, mineral, vegetable or ester based is:

always distinguishable by taste and smell.

generally distinguishable by colour.

generally distinguishable by colour only if they are from the same manufacturer.

cannot be distinguished by colour alone.

#33. An ACOV will:

provide an idling circuit when a selection is made.

extend the life of the accumulator.

provide an idling circuit when the accumulator is fully charged.

ensure the pump is always on load.

#34. The purpose of a hydraulic fuse is to:

allow the parking brake to remain on overnight if required.

allow a reduced pressure to the wheel brake system to prevent the wheels locking.

prevent over-pressurising the reservoir as altitude increases.

prevent total loss of system fluid if the brake pipeline is ruptured.

#35. A shuttle valve will allow:

the accumulator to be emptied after engine shut down.

the pressure pump to off-load when the system pressure is reached.

two independent pressure sources to operate a system/component.

high pressure fluid to return to the reservoir if the Full Flow Relief Valve fails.

#36. The purpose of a reservoir is to:

compensates for temperature changes.

compensates for small leaks, expansion and jack displacement.

compensates for fluid loss.

to minimise pump cavitation.

#37. When the hydraulic system pressure is released:

reservoir air pressure will increase.

reservoir fluid contents will rise if reservoir is lower than other components in the system.

reservoir fluid contents will fall if reservoir is the highest point in the system.

reservoir contents are dumped overboard.

#38. Hydraulic pressure in a closed system:

is greater in pipes of larger diameters.

is greater in pipes of smaller diameters.

does not vary with pipe diameter.

varies in direct proportion to the system demands.

#39. Skydrol hydraulic fluid:

needs no special safety precautions or treatment.

is flame resistant but is harmful to skin, eyes and some paints.

is highly flammable and harmful to skin, eyes and some paints.

is highly flammable but not harmful in any other way.

#40. Skydrol hydraulic fluid can be used to replenish:

any hydraulic system without restriction.

hydraulic systems that have butyl rubber seals only.

any hydraulic system in an emergency.

hydraulic systems that have neoprane seals only.

#41. The purpose of a reservoir is:

to provide a housing for the instrument transmitters.

to enable the contents to be checked.

to allow for fluid displacements, small leaks, thermal expansion and contents monitoring.

to provide a housing for the main system pumps and so obviate the need for backing pumps.

#42. Hydraulic Thermal Relief Valves are fitted:

to release all the pressure back to return in an overheat situation.

to release half the pressure back to return in an overheat situation.

to relieve excess pressure back to the actuator in an overheat situation.

in isolated lines only to relieve excess pressure caused by temperature rises.

#43. A main system hydraulic pump:

does not need a positive fluid supply if primed before startup.

always needs a positive fluid supply in order to prevent cavitation.

does not need a positive fluid supply in order to prevent cavitation.

can be run dry without causing any damage.

#44. Different diameter actuators supplied with the same pressure at same rate:

exert the same force.

will lift equal loads.

will move at the same speed.

exert different forces.

#45. A force of 1,500 N is applied to a piston of area 0.002m² and generates a force of-----(1)------Non a piston of area 0.003m². The pressure generated is -----(2)-----and, if the smaller piston moves 0.025m, the work done is-----(3)------.

(1) 56.25J (2) 750,000Pa (3) 750,000N

(1)750,000N (2) 2,250 P (3) 56.25J

(1) 225N (2) 75,000Pa (3) 562.5 J

(1) 2,250N (2) 750,000Pa (3) 37.5 J

#46. The following statements relate to hydraulic accumulators. The function of a accumulator is to: 1. Store fluid under pressure 2. Dampen pressure fluctuations 3. Allow for fluid expansion 4. Replace the need for a reservoir 5. Absorb some of the landing loads 6. Allow for thermal expansion 7. Prolong the period between pump cut-in and cut-out 8. Provide the initial pressure when a selection is made and the pump is cut out 9. Provide an emergency reserve of pressure in the event of pump failure Which of the following applies?

All of the statements are correct.

None of the statements are correct.

Statements 1, 2, 3, 4, 5, 8 and 9 are correct.

Statements 1, 2, 3, 6, 7, and 9 are correct.

#47. The seal materials used with hydraulic fluids to DEF/STAN 91-48 and SKYDROL 700 specification are respectively:

natural rubber and neoprene.

neoprene and natural rubber.

butyl and neoprene.

neoprene and butyl.

#48. To prevent cavitation of the pump a hydraulic reservoir may be:

pressurised.

bootstrapped.

above the pump.

all of the above.

#49. A hand pump is usually fitted:

for ground servicing purposes.

lowering the landing gear in an emergency.

pressurising the oleo struts in the air.

retracting the gear after take-off.

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