hydraulic and pneumatic systems Flashcards
what is the first step when checking hydraulic reservoir fluid level
verify that the hydraulic systems are set to the configuration specified in the maintenance manual
what is the most likely cause of hydraulic fluid flowing through a filter bypass valve
the filter has become clogged
what are 2 basic differences between a hydraulic and a pneumatic system
the fluid in a pneumatic system is compressible and that used in a hydraulic system is incompressible. a pneumatic system has no return system
what are 2 functions of a low pressure pneumatic system in a aircraft
to operate the gyros in flight instruments, and to inflate pneumatic deicer boots
what type of pump is used in a low pressure pneumatic system
a vane-type pump
why do high altitude aircraft that have pneumatic gyro instruments are pressure actuated instruments rather than vacuum actuated instruments
at high altitude there is not enough air mass to drive the gyros at their required speed
what effect would a dirty inline air filter have on the operation of pneumatic gryo instruments
the instruments would not get enough air to spin up to their required speed
of what material are the vanes in a dry type air pump made
carbon
what kind of device is used to control the speed of movement of the piston in a pneumatic actuator
a variable orifice
what is the purpose of the moisture separator in a high pressure pneumatic system
the separator collects moisture from the air and holds it on a baffle until the system is shut down. when the inlet pressure to the moisture separator drops below 450 PSI, a drain valve opens and all of the accumulated moisture is discharged overboard. a moisture separator removes about 98% of the moisture in the air
what are 2 types of filters that are used in an aircraft pneumatic system
micronic (paper) type, and screen type
is a chevron seal a one way or two way seal
a one way seal
to which side of a chevron seal should the pressure be applied
to the open side
is an O ring seal a one way or two way seal
a two way seal
how can you be sure of getting an O ring made of the correct material for a specific hydraulic component
the O ring must have the correct part number and it must have been obtained from reputable source
on which side of an O ring should the backup ring be replaced
on the side away from the source of pressure
what should be done to the sharp edges of threads and actuator pistons when installing O rings
the sharp edges should be covered with paper
what is the purpose of an orifice check valve in an aircraft hydraulic system
an orifice check valve allows full flow of fluid in one direction through the valve, but restricts the flow in the opposite direction
what is the difference in function between a pressure regulator and a pressure relief valve
pressure regulators control overall system pressure. pressure relief valves act a back up to the pressure regulator to prevent overpressure damage to the system and components
what does an unloading valve/ pressure regulator do in a hydraulic system
the unloading valve, or pressure regulator, controls system pressure by shifting the pump outlet fluid from the pressurized system back into the reservoir when the system pressure is high enough. the fluid circulates with very little load on the pump until the system pressure drops to the regulator kick in value. the pump then forces fluid into the system until the pressure builds back up the regulator kick out valve
