AIRCRAFT HYDRAULIC AND PNEUMATIC POWER SYSTEM

Question 1

What device in a hydraulic system with a constant delivery pump allows
circulation of the fluid when no demands are on the system?

Answer 1

Pressure regulator.

Question 2

An O ring intended for use in a hydraulic system using MIL-H-5606 (mineral base)
fluid will be marked with __________.

Answer 2

a blue stripe or dot.

Question 3

What condition would most likely cause excessive fluctuation of the pressure
gauge when the hydraulic pump is operating?

Answer 3

Inadequate supply of fluid.

Question 4

The purpose of an orifice check valve is to_________________ .

Answer 4

restrict flow in one direction and allow free flow in the other.

Question 5

To prevent external and internal leakage in aircraft hydraulic units, the most commonly
used type of seal is the _____________.

Answer 5

O ring seal.

Question 6

Which allows free fluid flow in one direction and no fluid flow in the other direction?

Answer 6

Check valve.

Question 7

What function does the absolute pressure regulator perform in the pneumatic
power system?

Answer 7

Regulates the compressor inlet air to provide a stabilized source of air for the
compressor.

Question 8

Relief valves are used in pneumatic systems__________ .

Answer 8

to reduce the rate of airflow.

Question 9

An aircraft pneumatic system, which incorporates an engine driven multistage
reciprocating compressor, also requires __________.

Answer 9

a moisture separator.

Question 10

Pneumatic systems utilize________.

Answer 10

relief valves.

Question 11

The component in the hydraulic system that is used to direct the flow of fluid is the
________.

Answer 11

selector valve.

Question 12

The purpose of the pressure regulator in a hydraulic system is to_____.

Answer 12

maintain system operating pressure within a predetermined range and to unload
the pump.

Question 13

What is one advantage of piston type hydraulic motors over electric motors?

Answer 13

There is no fire hazard if the motor is stalled.

Question 14

Generally, the first step in removing an accumulator from an aircraft is to…

Answer 14

relieve system pressure.

Question 15

If a hydraulic brake system uses neoprene rubber packing materials, the correct
hydraulic fluid to service the system is…

Answer 15

mineral base oil

Question 16

The internal resistance of a fluid which tends to prevent it from flowing is called

Answer 16

viscosity.

Question 17

Which is a characteristic of petroleum base hydraulic fluid?

Answer 17

Flammable under normal conditions.

Question 18

Petroleum base hydraulic fluid is which color?

Answer 18

red.

Question 19

Which is a characteristic of synthetic base hydraulic fluid?

Answer 19

High flash point.

Question 20

Where can information be obtained about the compatibility of fire-resistant hydraulic
fluid with aircraft materials?

Answer 20

Manufacturer’s technical bulletins.

Question 21

Characteristics of MIL-H-5606 hydraulic fluid are __________ .

Answer 21

red color, petroleum base, will burn, synthetic rubber seals.

Question 22

Characteristics of MIL-H-5606 hydraulic fluid are_____________ .

Answer 22

red color, petroleum base, will burn, synthetic rubber seals.

Question 23

A unit which transforms hydraulic pressure into linear motion is called_________.

Answer 23

an actuating cylinder.

Question 24

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

Answer 24

Thermal relief valve.

Question 25

Excluding lines, which components are required to make up a simple hydraulic
system?

Answer 25

Pump, reservoir, selector valve, and actuator.

Question 26

In a gear type hydraulic pump, a mechanical safety device incorporated to protect
the pump from overload is the________.

Answer 26

shear pin

Question 27

Pressure is a term used to indicate the force per unit area. Pressure is
usually expressed in____________.

Answer 27

pounds per square inch.

Question 28

The unit which causes one hydraulic operation to follow another in a definite order
is called a_______ .

Answer 28

sequence valve.

Question 29

A hydraulic accumulator is charged with an air preload of 1,000 PSI. When a
hydraulic system pressure of 3,000 PSI is developed, the pressure on the air side of
the accumulator will be______.

Answer 29

193,000 PSI.

Question 30

Before removing the filler cap of a pressurized hydraulic reservoir ______.

Answer 30

relieve the air pressure