AGK Systems - Hydraulic System Principles

Question 1

Typical uses for hydraulic systems?

Answer 1

Transmit power to remote location.
Landing gear and wheel brakes.
Nose wheel steering.
Primary flight controls.
Etc.

Question 2

How is pressure created in a hydraulic system?

Answer 2

Resistance to flow.

Question 3

What is the static pressure of air at sea level?

Answer 3

14.7psi.

Question 4

At any given depth, if you measure the pressure multiple times along the same depth line, will it be the same?

Answer 4

Yes.

Question 5

Pascals law.

Answer 5

Air is very compressible.
Oil and water incompressible.
500lb load of oil enclosed in a cylinder is felt as 500lb of static pressure at every point.

Question 6

Incompressibility meaning.

Answer 6

Pressure force is instantaneously transferred to all points in the fluid.

Question 7

Basically, what does hydraulics do?
What’s the formula for this?

Answer 7

Turn a small force into a big force.
Input force x Input distance=output force x output distance.

Question 8

How many pumps do active hydraulic systems use?

Answer 8

1 or more.

Question 9

How does a passive hydraulic system raise pressure?

Answer 9

Uses human power.

Question 10

What can active systems supply?

Answer 10

Constant pressure all the time - closed centred systems.
Pressure only when demanded - open centred systems.

Question 11

Hydraulic fluid requirements.

Answer 11

Low viscosity.
Good lubrication qualities.
Corrosion resistance.
Resistance to foaming and creating sludge.
Thermal stability.
High freezing/low freezing points
None flammable.
Flash point +100 degrees.

Question 12

Can you mix hydraulic fluids?

Answer 12

No, must be same, from correct specification from an unopen container.

Question 13

Common forms of hydraulic fluid.

Answer 13

Synthetic Hydro-carbon based, used in systems with butyl rubber/teflon seals, may be orange.

Phosphate ester (synthetic) - Skydrol - Usually purple in colour.

Mineral - E.g. DTD 585, coloured red.

Question 14

Describe a mineral based hydraulic fluid (kerosene).

Answer 14

Red.
Suitable for high pressure systems.
Good resistance to foaming.
High flash point and boil point.
Although flammable.
Synthetic rubber seals.

Question 15

Describe a synthetic based hydraulic fluid (phosphate ester).

Answer 15

500A purple in colour.
Skydrol, 3 grades in use, 500, 500A, 700.
Can be used at very high pressure.
Must only be used with: butyl rubber, ethylene, propylene, teflon seals.