Hydraulic and pneumatic power systems Flashcards
What are the three principal categories of hydraulic fluid’s
Mineral, polyalphaolefin, phosphate Esther
What color is mineral-based hydraulic fluid
Red
How do you determine which type of hydraulic fluid to use in a specific system
In the aircraft maintenance manual, we’re on the instruction plate attached to the reservoir on the unit being serviced
What will happen to the seals in a vegetable-based hydraulic system if it is serviced with mineral Base or phosphate Esther base fluids
Seals were swell, breakdown, and block the system
When installing a Chevron seal what must be Considered
Chevron seal is directional and must be installed with the pressure going toward the open side of the seal
When hydraulic lines have been disconnected, what precautions should be taken to prevent contamination of the system
I’ll 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 material
There is a bypass valve which routes the hydraulic fluid directly from the inlet port to the outlet port
What is a micron filter
A filter with a paper element
Name the filter use an aircraft pneumatic systems
Paper pleated and screen type
Why are some hydraulic reservoir is pressurized
To ensure positive flow of fluid to the engine driven pump at high altitude
What methods are used to pressurize hydraulic reservoirs
Some systems use a variable displacement hydraulic pump, engine bleed air, or hydraulic system pressure acting on small piston inside the reservoir.
Another method is an aspirator or Venturi
What are two types of accumulator housing
Spherical and cylindrical
Name three types of hydraulic accumulators
Diaphragm, bladder, piston
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 a system safety valve
What is the purpose of unloading valve in a close hydraulic system
The unloading valve is designed to provide a low pressure path for the fluid flow from the pump back to the reservoir when the system has no flow requirements. The unloading valve also acts as a pressure regulator regulator
What is the function of a wing flap overload valve
The purpose of the valve is to prevent possible structural damage to the flap for the flap system that might result from the flaps being lowered at excessive speed
What is the purpose of the shareable section in a hydraulic pump
If the pump or disease, the Scherer section with disconnect the pump from the engine, allowing the engine to continue to operate
What are two different types of hydraulic pumps
They are hand pumps in power pumps
Palms can also be classified as positive just placement, or non-positive displacement
What pump is most suitable for low pressure pneumatic systems
Vein 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 an aircraft
Pneumatic systems are sometimes used to operate breaks, open and close doors, starting, pump driving, and operating emergency devices
What happens to the air after pneumatic system is operating
The air is dumped overboard
Why should pneumatic system be purged periodically
To remove contamination, moisture, or oil from the components and lines
What is the purpose of a relief valve in pneumatic system
The relief valve protects the system against over pressurization by venting access pressure to the atmosphere
What is the purpose of an accumulator
Used to prevent hydraulic system shock went under high load demand conditions
What is an example of a phosphate Esther base fluid
Skydrol
