Hydraulics Flashcards
What systems require hydraulic pressure?
Landing gear, brakes, pusher, rudder boost, spoiler/speed brakes
What provides variable flow and pressure to the hydraulic system? And at what rate?
Two engine-driven hydraulic pumps at 3000 psi (located on accesory gear box of each engine)
In case of a hydraulic pump malfunction, what prevents rotation without interfering with the continued operation of the engine?
The hydraulic pump connecting shaft to the accessory gear box (AGB) has a recess designed to work as a shaft shear point if the torque imposed by the hydraulic pump to the AGB exceeds limits….i.e. a mechanical snap point of the limit is exceeded
What is the function of the priority valve in the hydraulic system?
It guarantees hydraulic power to the spoilers, stick pusher, rudder spring actuator or brakes by restricting flow to the landing gear, if being used simultaneously (“landing gear lowest priority”)
Where is the hydraulic fluid stored?
A (spring-biased bootstrap diaphragm type) reservoir. 50 psi reservoir pressure, 3000 psi system pressure
How much fluid can the hydraulic reservoir hold?
Maximum of 1.3 gallons
What provides contamination protection for the hydraulic system?
Two disposable filter elements located on the lower portion of the manifold. (One for low pressure return and one for the high pressure line; the filter can capture any particle greater than 5 microns)
What happens if the hydraulic system filter fails or is blocked by too much contamination?
A bypass valve will open to allow continued flow through the system
What is available to indicate that the filters need to be replaced?
The filters have red “pop-up” differential pressure indicators to provide a visual indication for when the filters need to be replaced
How are the hydraulic fire shutoff valves closed?
Manually by the engine fire extinguisher shutoff buttons automatically in case of hydraulic system high temperature, or through the shutoff switches on the hydraulic panel
What does a “HYD HI TEMP” EICAS message indicate?
Hydraulic fluid temp has risen to above 235+/-7F and both FSOV automatically close
What does a “HYD LO PRESS” EICAS message indicate?
The system is not capable of providing flow at the rated pressure
What does a “HYD SOV [1/2] FAIL” EICAS message indicate?
A FSOV was commanded to close and did not close (or FSOV position does not agree with the switch position)
