Hydraulics

Question 1

Teflon hose that has developed a permanent set from being exposed to high pressure or temperature should

Answer 1

Be immediately replaced.

Question 2

What particular sequence should be followed if it is necessary to adjust several pressure regulating valves in a hydraulic system?

Answer 2

Units with the highest pressure settings are adjusted first.

Question 3

The most probable cause for an aircraft’s constant pressure hydraulic system pump to cycle more frequently than usual, and no fluid leakage can be detected is

Answer 3

Low accumulator preload.

Question 4

Hydraulic systems incorporate restrictors in them to

Answer 4

Control the rate of movement of hydraulically operated mechanisms.

Question 5

The hydraulic component that automatically directs fluid from either the normal source or an emergency source to an actuating cylinder is called a

Answer 5

Shuttle valve.

Question 6

The distinguishing characteristic of a hydraulic system open center selector valve is that

Answer 6

Fluid flows through the valve in the “OFF” position.

Question 7

A hydraulic system operational check indicates that the wing flaps cannot be lowered using the main hydraulic system pump, but can be lowered by using the emergency pump. Which is the most likely cause?

Answer 7

The fluid level in the reservoir is low.

Question 8

In a pneumatic system, the air that is expended and no longer needed when an actuating unit is operated is

Answer 8

Exhausted or dumped, usually overboard.

Question 9

A hydraulic accumulator is charged with an air preload of 1000 PSI. When a hydraulic system pressure of 3000 PSI is developed, the pressure on the air side of the accumulator will be

Answer 9

3000 PSI.

Question 10

After installation of a rebuilt hydraulic hand pump, it is found that handle cannot be moved in the pumping direction (pressure stroke). The most likely cause is an incorrectly installed

Answer 10

Hand pump outport check valve.

Question 11

Which valve installed in a hydraulic system will have the highest pressure setting?

Answer 11

Thermal relief valve.

Question 12

In a high pressure hydraulic system, extrusion on an O-ring seal is prevented by the use of a

Answer 12

Backup ring on the side of the O-ring away from the pressure.

Question 13

How can the air pressure charge in an accumulator be determined if the system pumps are inoperative, but the system still has hydraulic pressure indication?

Answer 13

Operate a hydraulic unit slowly and note the pressure at which a rapid pressure drop begins as it goes to zero.

Question 14

To protect packing rings or seals from damage when it is necessary to install them over or inside threaded sections, the

Answer 14

Threaded section should be covered with a suitable sleeve.

Question 15

Pneumatic systems use relief valves

Answer 15

As damage preventing units.

Question 16

The flap overload valve’s primary function is to

Answer 16

Prevent the flaps from being lowered at airspeeds which would impose excessive structural loads.

Question 17

A systems check of an airplane’s hydraulic system reveals that when the hydraulic pump is running, the pressure is normal. However, when the pump is stopped, the pressure Gage immediately goes to zero and no hydraulic pressure is available. This is an indication of a

Answer 17

Leaking accumulator air valve.

Question 18

Before making adjustments to the relief valve of a main hydraulic system that incorporates a pressure regulator, the mechanic should first

Answer 18

Manually unseat all system check valves to allow unrestricted flow in both directions.

Question 19

What should a mechanic do before removing the filler cap of a pneumatic pressurized hydraulic reservoir?

Answer 19

Relieve the air pressure.