Chapter 8 - Hydraulic and Pneumatic Power Systems - Oral Questions

Question 1

What materials form the bases of the three types of hydraulic fluids?

Answer 1

Vegetable (MIL-H-7644 Blue Vegetable Base)

Mineral (MIL-H-5606 Red Kerosene/Petroleum Base)

Phosphate-esters (Skydrol Purple Phosphate-ester Base)

Question 2

What colors denote mineral-based and phosphate-ester based hydraulic fluids?

Answer 2

Mineral based fluids are red

Phosphate-ester based fluids are light purple

Question 3

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

Answer 3

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

Question 4

Name several sources used to develop hydraulic pressure.

Answer 4

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

Question 5

What would cause the bypass valve in a hydraulic filter to open and allow unfiltered fluid to circulate in the system?

Answer 5

A clogged filter element

Question 6

Describe several methods of pressurizing a hydraulic reservoir.

Answer 6

Engine bleed air,

system pressure acting on a small piston in the reservoir,

using variable-displacement hydraulic pumps

Question 7

What feature prevents engine damage if an engine-driven hydraulic pump seizes or is overloaded?

Answer 7

A shear section in the pump driveshaft will break, disconnecting the pump from the engine

Question 8

Describe the purpose of a pressure relief valve.

Answer 8

Pressure relief valves limit the maximum pressure produced by the pump, thereby preventing failures of the system components

Question 9

Engine-driven pumps deliver the output fluid flow in what two forms?

Answer 9

As a constant volume or a variable volume

Question 10

Describe the operation of a gear-type pump.

Answer 10

Two meshed gears, driven by a power source, rotate in a housing. Inlet fluid is carried around the outside of the gears and delivered to the outlet side as the gears rotate

Question 11

Describe the purpose of the pressure regulator.

Answer 11

Pressure regulators manage the output of the pump to maintain system pressure. They allow the pump to be unloaded so it turns without significant resistance

Question 12

What is the device that is used in some systems to supplement the pump output during periods of high demand?

Answer 12

An accumulator

Question 13

What are the three different types of accumulators?

Answer 13

Piston, diaphragm, and bladder

Question 14

What safety precautions must be taken prior to disassembling an accumulator?

Answer 14

Release all of the air or preload

Question 15

When a hydraulic unit is replaced, what precautions should be taken to avoid contamination of the system?

Answer 15

All lines should be capped or plugged immediately after they are disconnected

Question 16

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

Answer 16

Landing gear,

brakes,

flaps, and

other mechanical actuators

Question 17

Name several sources of pneumatic power

Answer 17

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

Question 18

What happens to excess pressure in a pneumatic system?

Answer 18

A relief valve vents it overboard

Question 19

What is the function of a restrictor in a pneumatic system?

Answer 19

To control the rate of flow of the airflow

Question 20

What are the reasons for periodically purging a pneumatic system?

Answer 20

To remove moisture and contaminants