Hydraulic and Pneumatic Power Systems Flashcards
What are three types of hydraulic fluid currently being used in civil aircraft?
Vegetable, mineral, 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?
Aircraft Maintenance Manual or 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 of phosphate ester base fluids?
Seals will swell, break down and contaminate or block the system.
When hydraulic line have been disconnected, what precautions should be taken to prevent contamination of the system?
Lines should be plugged or capped immediately after disconnecting.
What happens to the hydraulic fluid flow if the filter element becomes clogged with foreign matter?
A bypass value will open, routing fluid directly from inlet port to outlet port of the filter unit.
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?
Variable displacement hydraulic pumps, engine bleed air, hydraulic system acting on a small piston inside the reservoir, or aspirator (venturi-tee).
Name three types of hydraulic accumulators?
Diaphragm, bladder and piston types.
What is the purpose of a pressure relief value in a hydraulic system?
To prevent high pressure from rupturing the system.
What is the purpose of an unloading value in a closed hydraulic system?
The value acts as a pressure regulator, preventing low pressure paths from allowing flow back to the reservoir when the system has no flow requirements.
What is the function of a wing flap overload valve?
To prevent structural damage to the flaps or flap system that might result from use of the flaps at excessive speeds.
What protects a direct-pressure type hydraulic pressure gauge from pressure surges?
A dampening device (restrictor) installed in the line leading to the gauge or at the inlet to the gauge itself.
What are pneumatic systems used for in aircraft?
Brakes, open and close doors, engine starting, driving pumps, and operating emergency devices.
What happens to the air after a pneumatic system is operated?
The air is dumped overboard.
