Airframe Ch 8 Hydraulic and Pneumatic Power Systems – Flashcards
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What materials form the bases of the three types of hydraulic fluids?
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Vegetable, mineral, and phosphate-esters. JSAT 8-7
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What colors denote mineral-based and phosphate-ester-based fluids?
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Mineral based fluids are red and phosphate-ester based fluids are light purple. JSAT 8-7
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what are the results of exposing lacquers, oil-based paint, plastic resins, and vinyl compounds to phosphate-ester-based hydraulic fluid?
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The materials will be damaged and/or softened, or the paint will peel. JSAT 8-8
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Name several sources used to develop hydraulic pressure?
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Hand pumps, engine-driven pumps, and electrically driven pumps. JSAT 8-12, 8-15
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What would cause the bypass valve in a hydraulic filter to open and allow unfiltered fluid to circulate in the system?
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A clogged filter element. JSAT 8-14
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Describe several methods of pressurizing a hydraulic reservoir.
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Engine bleed air, system pressure acting on a small piston in the reservoir, using variable-displacement hydraulic pumps. JSAT 8-16
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What feature prevents engine damage if an engine-driven hydraulic pump seizes or is overloaded?
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A shear section in the pump driveshaft will break, disconnecting the from the engine. JSAD 397
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Describe the purpose of a pressure relief valve.
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Pressure relief valves limit the maximum pressure produced by the pump thereby preventing failures of the system components. JSAT 8-23
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Engine-driven pumps deliver the output fluid flow in what two forms?
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As a constant volume of a variable volume. JSAT 8-23
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Describe the operation of a gear-type pump?
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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.
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Describe the purpose of a pressure regulator?
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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.
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What is the device that is used in some systems to supplement the pump output during periods of high demand?
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An accumulator.
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What are the three different types of accumulators?
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Piston, diaphragm, and bladder.
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What system precautions must be taken prior to dissembling an accumulator?
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Release all of the air or preload.
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When a hydraulic unit is replaced, what precautions should be taken to avoid contamination of the system?
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All lines should be capped or plugged immediately after they are disconnected.
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What types of components or systems are pneumatically operated in some aircraft?
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Landing gear, brakes, flaps, and other mechanical actuators.
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Name several sources of pneumatic power?
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Storage bottles, engine bleed air, engine-driven compressors or vane-type pumps.
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What happens to excess pressure in a pneumatic system?
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A relief valve vents it overboard.
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What is the function of a restrictor in a pneumatic system?
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To control the rate of flow of the JSAT.
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What are the reasons for periodically purging a pneumatic system?
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To remove moisture and contaminants.
