Engines Ch.6

Front 1

Explain Pascal's Law.

Back 1

Pressure applied to a confined liquid is transmitted equally in all directions without the loss of pressure and acts with equal force on equal surfaces.

Front 2

Define force, pressure, and area

Back 2

Force: a push or pull
Pressure: the amount of force per unit area.
Area: unit area is a square inch

Front 3

Explain how force, pressure, and area relate to hydraulic theory.

Back 3

P=F/A
Force is applied to piston. If resisitance is on output piston, the input piston is pushed downward, a pressure is created through the fluid.

Front 4

Expalin the relationship between linear displacement and the change of force between the input and output pistons of a closed hydraulic system.

Back 4

Linear displacement is inversely related to the multiplied force.
Linear displacement or distance travelled is exchanged for the change in force. If input distance is 1 inch, output distance is 1/10 inch.

Front 5

Explain why hydraulic systems are required on aircraft.

Back 5

To apply force. To operate various mechanisims.

Front 6

Describe the function of basic hydraulic components used on aircraft.

Back 6

Reservoir: storage tank for hydraulic fluid. Also can serve as an overflow basin for excess fluid forced out of the system
-nonpressurized reservoirs: vented to the ambient air to prevent a vacuum from being formed as the fluid level in the reservoir decreases.
-Pressurized reservoirs: pressurized by bleed air from the compressor or by hydraulic system pressure. Ensure positive fluid flow for any aircraft attitude. Used for high performance aircraft for high altitudes.
Pumps
-Hand pumps: supply fluid under pressure to subsystems. Normally for emergencies
-Power pumps:
-Variable displacement pumps: regulates volume delivery in accordance with system flow demands.
Constant displacement pump: delivers a constant fluid output for any given rotational speed. Must have pressure regulator or unloader valve
Pressure Regulator/unloader valve: always works with constant displacement pump. Pressure regulator maintains set pressure in the system by diverting excess pump flow back to the reservoir. Unloading valve will divert all pump flow back to the reservoir when the preset system pressure is reached.
Check Valve: allows one-way flow in a hydraulic system. It allows the free flow of hydraulic fluid from the pumps, but prevents back flow of system pressure.
Accumulator: Serves as a cushion or a shock absorber by absorbing pressure surges in system. Stores enough fluid under pressure for emergency use.
Filters: ensure delivery of containment free hydraulic fluid by preventing dust, grit, and undesirable impurities from entering the system.
Relief Valves: pressure limiting device Safety valve that prevents pressure from building up and causing damge.
Pressure gauge: indicate the amount of pressure in the hydraulic system.
Pressure switches: used to indicate hydraulic pressure drop that falls below allowable limits.
Hydraulic Fuses: safey devices installed at strategic locations in the system. Designed to detect or gauge ruptures, failed fittings, or leak producing failures.
Selector Control Valves: used to direct the flow of fluid.
Actuators: convert fluid under pressure into linear or reciprocating mechanical motion.

Front 7

Describe the operation of a basic aircraft hydraulic system.

Back 7

Power system includes fluid supply (reservoir), power supply (pump). The selector valves direct the flow of fluid to actuating units. Operate near 3,000 psi