Airframe Systems and Components (Hydraulics and Pneumatics) Flashcards
What are the three principal categories of hydraulic fluids?
Mineral, Polyalphaolefin, phosphate ester
what color is mineral based hydraulic fluid?
Red (5606)
how do you determine which type of hydraulic fluid do use any specific system?
In the aircraft maintenance manual, or on the instruction plate attached to the reservoir.
What will happen to the seals in a vegetable base hydraulic system if it is service with a mineral base or phosphate master base fluids?
The seals will swell, breakdown, and block the system.
When installing a Chevron seal what must be considered?
And chevron seal must be installed with pressure going toward the open side of the seal.
When hydraulic lines have been disconnected, what precaution 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 from the inlet port to the outlet port.
What is a Micronic filter?
Hey filter with a paper element.
Name the filters used in aircraft pneumatic systems?
Paper pleated and screen type.
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 pump, engine bleed air, or hydraulic system pressure acting on a small piston in the reservoir. another method is an aspirator or Venturi.
What are the two types of hydraulic accumulators?
Spherical , and cylindrical
Name the three types of hydraulic accumulators.
Diaphragm type, bladder type, and piston type.
What is the purpose of a pressure relief valve in a hydraulic system?
To limit the amount of pressure in the system. (safety valve)
What is the purpose of an unloading valve in a closed hydraulic system?
It acts as a pressure regulator. Designed to provide a low pressure path for the return fluid to flow from the pump back to the reservoir when the system has no flow requirements.
What is the function of a wing flap overload valve?
to prevent possible structural damage to the flap or the flap system from flaps being lowered at excessive speeds.
What is the purpose of the shearable section in a hydraulic pump?
the shear section will disconnect the pump from the engine if the pump were to seize. This allows engine to continue to operate.
What are two different types of hydraulic pumps?
Hand pumps and power pumps (positive and nonpositive displacement)
what pump is most suitable for low pressure pneumatic systems?
Vane type pump
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 of the gauge itself.
what are pneumatic systems used for in aircraft?
Brakes, open and close doors, starting, pump driving, and operating emergency devices.
What happens to the air after a pneumatic starter is operated?
The air is dumped overboard.
Why should a pneumatic system be purged periodically?
To remove contamination, moisture, oil from the components and lines.
What is the purpose of the relief valve in a pneumatic system?
Protect system against thermal expansion by venting excess pressure to the atmosphere.
What is the purpose of an accumulator?
To prevent hydraulic system shock when under high load demand conditions.
what is an example of a phosphate ester base fluid?
Skydrol
