Hydraulic Questions Flashcards
(15 cards)
Name the sources of power for the different hydraulic systems?
Green: ENGINE 1 pump and PTU.
Yellow: ENGINE 2 pump/PTU/Electric Pump/Cargo Door Handle.
Blue: Electric Pump and RAT.
What does each hydraulic system supply?
Green: Landing Gear/Flaps/Slats/Engine 1 Reverser/Normal Brakes/Flight Controls
Yellow: Flaps/Alternate Brakes/Engine 2 Reverser/Parking Brake/NWS/Flight Controls.
Blue: Slats/Emergency Generator/Flight Controls.
In flight, why does the green system look significantly depleted?
It is holding the gear in position through use of the green hydraulic system.
How are the hydraulic systems pressurised and why?
Reservoirs are pressurised via HP bleed air from engine 1. If it gets too low, system takes bleed air pressure from the crossbleed duct. Pressure is enough such that it will prevent cavitation in the pumps.
What is the purpose of the HYD priority valves?
They cut off hydraulic power to heavy load users of hydraulic pressure in a system gets low.
What is the purpose of hydraulic accumulators?
They help to maintain a constant pressure by covering transient demands during normal operation.
What is the purpose of the PTU?
The PTU enables the green system to pressurise the yellow system and vice versa. Kicks in when the pressure differential is greater than 500 psi between the green and yellow system. It enables the green system to be pressurised on the ground when the engines are stopped via the yellow electric pump.
Typical pressure for the 3 systems? What pressure would you expect from the blue system when being supplied by the RAT?
3000 psi normally +/- 200 psi.
2500 psi on the blue system when supplied by the RAT.
At what point does the system pressure display in Amber?
When the system pressure drops below 1450psi.
Of the dual hydraulic failures, what in your opinion is the worst and why?
Green and Yellow (Goodyear - Stopping)
Blue and Yellow (Best Yet)
Green and Blue (Gusting Bad - Controllability)
Green and Yellow worst failure due stopping distance approx 2500m. No flaps so high approach speed and no reversers. Braking on accumulator only. Max 7 applications.
Which of the dual HYD failures does the aircraft remain in normal law?
Blue and Yellow.
Why is the L/G gravity extended during a B+Y dual hydraulic failure?
In order to preserve the integrity of the green hydraulic system.
What is the purpose of lowering the landing gear at 200kts with a dual G+B HYD failure?
Direct law will activate sooner (as soon as gear is down) which will provide a better pitch control than when in alternate law with one elevator lost and all slats lost.
Why in the dual G+Y failure is flaps 3 selected before gear down?
In order for the aircraft to stabilise in trim at VAPP before lowering the gear and the aircraft reverting to direct law.
Which hydraulic services supply the ailerons?
Green and Blue
