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17 Cards in this Set
- Front
- Back
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What are three types of hydraulic fluid currently being used in civil aircraft? |
Vegetable base, mineral base, and phosphate ester base fluids |
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What is the color of mineral base hydraulic fluid? |
Red |
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How do you determine which type of hydraulic fluid to use in a specific system? |
The type fluid is specified in the aircraft maintenance manual or on the instruction plate attached to the reservoir or unit being serviced. |
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What will happen to the seals in a vegetable base hydraulic system if it is serviced with mineral base or phosphate ester base fluids? |
The seals will swell, break down, and block the system. |
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When hydraulic lines have been disconnected, what precautions should be taken to prevent contamination of the system? |
All hydraulic lines and fittings should be capped or plugged immediately after disconnecting. |
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What happens to the hydraulic fluid flow if the filter element becomes clogged with foreign matter? |
There is a bypass valve which routes the hydraulic fluid directly from the inlet port to the outlet port. |
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Why are some hydraulic reservoirs pressured? |
To ensure a positive flow of fluid to the engine-driven pump at high altitudes |
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What methods are used to pressurize hydraulic reservoirs? |
Some systems use air pressure directly from the aircraft cabin pressurization system, or from the engine compressor in turbine-powered aircraft. Another method is an aspirator or venture-tee. |
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Name three types of hydraulic accumulators? |
The diaphragm type, the bladder type, and the piston type |
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What is the purpose of a pressure relief valve in a hydraulic system? |
It is to limit the amount of pressure in the system. It is, in effect, a system safety valve. |
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What is the purpose of an unloading valve in a closed hydraulic system? |
The unloading valve is designed to provide a low pressure path for the fluid to flow from the pump back to the reservoir when the system has no flow requirements. The unloading valve also acts as a pressure regulator. |
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What is the function of a wing flag overload valve? |
The purpose of the valve is to prevent possible structural damage to the flaps or the flap system that might result from the flaps being lowered at excessive speeds. |
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What protects a direct-pressure type hydraulic pressure gauge from pressure surges? |
A dampening device in the form of a very small restrictor is installed in the line leading to the gauge, or at the inlet to the gauge itself. |
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What are pneumatic systems used for in aircraft? |
Pneumatic systems are sometimes used in operating brakes, opening and closing doors, starting, pump driving, and operating emergency devices. |
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What happens to the air when a unit in a pneumatic system is operated? |
The air is dumped overboard. |
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Why should a pneumatic system be purged periodically? |
To remove contamination, moisture, or oil from the components and lines |
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What is the purpose of the relief valve in a pneumatic system? |
The relief valve protects the system against over-pressurization (thermal expansion) by bleeding excess pressure to the atmosphere. |
