Hydraulic and Pneumatic systems

Question 1

What are three types of hydraulic fluids?

Answer 1

Vegetable, Mineral and Phosphate Esters.

Question 2

Which color mineral base and phosphate-ester hydraulic fluids have?

Answer 2

Mineral –Red / Phosphate ester – Light purple.

Question 3

What happens to plastic resins, vinyl compositions, lacqers, and oil base paints if exposed to a phosphate
ester base hydraulic fluid such as skydrol?

Answer 3

Damaged, softened and/or peeled.

Question 4

What precautions should be taken to minimize contamination during replacement of a hydraulic unit?

Answer 4

All lines should be plugged or capped after disconnecting.

Question 5

What would cause a hydraulic filter to go into open by-pass, allowing unfiltered fluid into the system?

Answer 5

a clogged filter

Question 6

What are two types of engine-driven hydraulic pumps?

Answer 6

Constant - delivery and Variable - delivery.

Question 7

How does a gear-type power pump operate?

Answer 7

Two meshed gears are driven by a power unit rotate in a housing.
Fluid is carried around the outside of the gears and delivered to the
outlet side as the gears rotate.

Question 8

What feature is built into a hydraulic pump-drive system to prevent engine damage in the event of pump
seizure or overload?

Answer 8

A shear action in the pump drive shaft occurs.

Question 9

What is the purpose of a pressure relief valve?

Answer 9

To limit the amount of pressure, preventing failure of the system components.

Question 10

What is the purpose of a pressure regulator?

Answer 10

To manage the output of the pump to maintain system pressure and allow the pump to turn without resistance(unloading).

Question 11

What is used in some hydraulic systems to supplement the power pump when several units are operated
at the same time?(High Demand)

Answer 11

An accumulator.

Question 12

What are the different types of accumulators?

Answer 12

Piston, Diaphragm and Bladder.

Question 13

What must be accomplished with any accumulator prior to disassembling?

Answer 13

Make sure that the air or preload has been discharged.

Question 14

For what purposes are pneumatic systems used in some aircrafts?

Answer 14

To operate brakes, doors, drive pumps and engine starting.

Question 15

What are sources of pneumatic power?

Answer 15

Storage bottles, vane-type pumps, and turbine engine compressor.

Question 16

What happens to excessive pressure in a pneumatic system?

Answer 16

A Relief Valve will bleed it to the atmosphere

Question 17

What is the purpose of restrictors that are used in aircraft pneumatic systems?

Answer 17

to control the rate of flow

Question 18

Why should a pneumatic system be purged periodically?

Answer 18

To remove contamination and moisture.

Question 19

What are the results of exposing lacquers, oil-baised paint, plastic resins and vynil compounds to
phosphate ester based hydraulic fluid?

Answer 19

The materials will be damaged and/or softened or the paint will peel.

Question 20

Name several sources used to develop hydraulic pressure:

Answer 20

Hand pumps, engine-driven pumps and electrically driven pumps.

Question 21

What types of components or systems are pneumatically operated in some aircraft?

Answer 21

Landing Gear, Brakes, Flaps and other mechanic actuators.

Question 22

Name several sources of pneumatic power:

Answer 22

Storage bottles, engine bleed air, engine-driven compressor or vane-type pumps.