Airframe Oral (Jeppesen) Hydraulic and Pneumatic Power Systems Flashcards
What materials form the bases of the three types of hydraulic fluids?
Vegetable, mineral, and phosphate-esters.
What colors denote mineral-based and phosphate-esters hydraulic fluids?
Mineral based fluids are red and phosphate-ester based fluids are light purple.
What are the results of exposing lacquers, oil-based paint, plastic resins, vinyl compounds to phosphate-ester-based hydraulic fluid?
The materials will be damaged and/or softened, or the paint will peel.
Name several sources used to develop hydraulic pressure.
Hand pumps, engine-driven pumps, and electrically driven pumps.
What would cause the bypass valve in a hydraulic filter to open and allow unfiltered fluid to circulate in the system?
A clogged filter element.
Describe several methods of pressurizing a hydraulic reservoir.
Engine bleed air, system pressure acting on a small piston in the reservoir, using variable-displacement hydraulic pumps.
What feature prevents engine damage if an engine-driven hydraulic pump seizes or is overloaded?
A shear section in the pump driveshaft will break, disconnecting the pump from the engine.
Describe the purpose of a relief valve.
Pressure relief valves limit the maximum pressure produced by the pump, thereby preventing failures of the system components.
Engine-driven pumps deliver the output fluid flow in what two forms?
As a constant volume or a variable volume.
Describe the operation of a gear-type pump.
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.
Describe the purpose of a pressure regulator.
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.
What is the main device that is used in some systems to supplement the pump output during periods of high demand?
An accumulator.
What are the three different types of accumulators?
Piston, diaphragm, and bladder.
What safety precautions must be taken prior to disassembling an accumulator?
Release all of the air or preload.
When a hydraulic unit is replaced, what precautions should be taken to avoid contamination of the system?
All lines should be capped or plugged immediately after they are disconnected.
