AF213 FAA Practice Quiz #3 Flashcards
An aircraft pneumatic system, which incorporates an engine-driven multistage reciprocating compressor, also requires
a moisture separator.
A hydraulic motor converts fluid pressure to
rotary motion.
What is the main purpose of a pressurized reservoir in a hydraulic system?
Prevent hydraulic pump cavitation.
If fluid is added to a reservoir in a constant pressure hydraulic system while the system is pressurized, what will result?
The fluid level will increase when system pressure is reduced.
If an engine-driven hydraulic pump of the correct capacity fails to maintain normal system pressure during the operation of a cowl flap actuating unit, the probable cause is
restriction in the pump outlet.
Extrusion of an O-ring seal is prevented in a high-pressure system by the use of a
backup ring on the side of the O-ring away from the pressure.
Where can information be obtained about the compatibility of fire-resistant hydraulic fluid with aircraft materials?
Fluid manufacturer’s technical bulletins.
How many of these seals are used with petroleum base hydraulic fluids?
Neoprene, Buna-N.
If an aircraft hydraulic system requires mineral base hydraulic fluid, but phosphate ester base hydraulic fluid is used, what will be the effect on the system?
System will be contaminated, fluids will not blend, and the seals will fail.
An emergency supply of fluid is often retained in the main hydraulic system reservoir by the use of a standpipe. The supply line is connected to the
Inlet of the main hydraulic system.
Characteristics of MIL-H-8446 (Skydrol 500 A & B) hydraulic fluid are
light purple color, phosphate ester base, fire resistant, butyl rubber seals.
Which of the following lists only desirable properties of a good hydraulic fluid that has chemical stability?
Low viscosity, high flash point, high fire point.
How would the air pressure charge in the accumulator be determined if the engine is inoperative, but the system still has hydraulic pressure?
Operate a hydraulic unit slowly and note the pressure at which a rapid pressure drop begins as it goes toward zero.
After installation of a rebuilt hydraulic hand pump, it is found that the handle cannot be moved in the pumping direction (pressure stroke). The most likely cause is an incorrectly installed
hand pump outport check valve.
If hydraulic fluid is released when the air valve core of the accumulator is depressed, it is evidence of
a ruptured diaphragm or leaking seals.
What function does the absolute pressure regulator perform in the pneumatic power system?
Regulates the compressor inlet air to provide a stabilized source of air for the compressor.
The component in the hydraulic system that is used to direct the flow of fluid is the
selector valve.
Which seals are used with petroleum base hydraulic fluids?
Buna-N.
What is the purpose of using backup rings with O-rings in hydraulic systems above 1,500 PSI?
Prevent high pressure from extruding the seal between the moving and stationary part.
Some hydraulic systems incorporate a device which is designed to remain open to allow a normal fluid flow in the line, but closed if the fluid flow increases above an established rate. This device is generally referred to as a
hydraulic fuse.
What safety device is usually located between the driving unit and hydraulic pump drive shaft?
Pump drive coupling shear section.
In a typical high-pressure pneumatic system, if the moisture separator does not vent accumulated water when the compressor shuts down, a likely cause is a
malfunctioning solenoid dump valve.
After installation of a rebuilt hydraulic hand pump, it is found that the handle cannot be moved in the pumping direction (pressure stroke). The most likely cause is an incorrectly installed
hand pump outport check valve.
The internal resistance of a fluid which tends to prevent it from flowing is called
viscosity.
If an engine-driven hydraulic pump of the correct capacity fails to maintain normal system pressure during the operation of a cowl flap actuating unit, the probable cause is
restriction in the pump outlet.
A hydraulic pump is a constant-displacement type if it
delivers a uniform rate of fluid flow.
Chattering of the hydraulic pump during operation is an indication
that air is entering the pump.
The installation of a new metal hydraulic line should be made with
enough bends to allow the tube to expand and contract with temperature changes and to absorb vibration.
How can the proper hydraulic fluid to be used in an airplane be determined?
By consulting the aircraft manufacturer’s service manual.
A pilot reports that when the hydraulic pump is running, the pressure is normal. However, when the pump is stopped, no hydraulic pressure is available. This is an indication of a
l leaking accumulator air valve.
Heat exchanger cooling units are required in some aircraft hydraulic systems because of
high pressures and high rates of fluid flow.
A loud hammering noise in a hydraulic system having an accumulator usually indicates
too low or no preload in the accumulator.
