Hydraulic and Pneumatic Power Systems Flashcards
What are the three types of hydraulic fluid currently being used in civil aircraft?
Vegetable base, mineral base, and phosphate ester base fluids.
What is the color of mineral base hydraulic fluid?
Red
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.
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.
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.
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 form the inlet port to the outlet port.
Why are some hydraulic reservoirs pressurized?
To ensure a positive flow of fluid to the engine driven pump at high altitudes.
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 venturi-tee.
Name three types of hydraulic accumulators?
The diaphragm type, the bladder type. and the piston type.
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.
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.
What is the function of a wing flap 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 a. excessive airspeeds.
What protects a direct-pressure type hydraulic pressure gage from pressure surges?
A dampening device in the form of a very small restrictor is installed in the line leading to the gage, or at the inlet to the gage itself.
What are pneumatic systems used for in aircraft?
Pneumatic systems are sometimes used to operate brakes, open and close doors, starting, pump driving, and operating emergency devices.
. What happens to the air when a unit in a pneumatic system is operated?
The air is dumped overboard.
