Hydraulics Flashcards
Name the sources of power each of the hydraulic systems.
Green - engine driven pump.
Blue - RAT & electric pump.
Yellow - engine driven pump, electric pump and hand pump for the cargo doors when there is no electrical power
What services does the green system, yellow system and blue system power?
Refer to hydraulic architecture in QRH but the main ones are:
Green normal brakes, landing gear, flaps and slats.
Blue slats, Emergency Generator.
Yellow flaps, alternate brakes and NWS.
Why in the hydraulic system pages in flight does the green system show slightly lower than the other systems?
Landing gear retracted
How are the hydraulic reservoirs pressurised and why?
Pressurised by engine 1 bleed system or crossbleed to avoid pump cavitation (air in the system).
What is the purpose of the hydraulic priority valves?
To shut off high demand services
What is the purpose of the hydraulic accumulators?
Helps to maintain constant pressure by covering transient demands during normal ops - e.g taking flaps at the same time as dropping the gear
Explain the purpose of the PTU
Bi-directional valve that pressurises the yellow or green system when either the Green or Yellow system has a low pressure (drops by 500psi or more),
PTU uses pump on the working side to drive a motor to power the failed system.
It doesn’t transfer fluid and it has nothing to do with the blue system.
What is the typical system pressure for the 3 hydraulic systems and what pressure would you expect to see when the RAT is powering the blue system?
3000psi
2500psi when powered by the RAT
At what point does the system pressure indicate amber? At what PSI?
1450psi and resets when above 1750psi
Of the the dual hydraulic failures, which in your opinion is worst and why?
Depends where you are. Probably Green and Blue as there are lots of long runways in Europe so G+Y is less of an issue
Which of the dual hydraulic failures maintains the aircraft in normal law?
B+Y
Why is the gear extended by gravity with the blue and yellow system failure, after all the green is still serviceable?
Priority valve closes to protect the green system
What is the purpose of extending the landing gear at 200kts with the green and blue system failure?
To give you better control of the aircraft as you have no slats at around 200kts
Why in the green and yellow system failure is flap 3 selected before the gear is selected down?
The stabiliser is frozen, the aircraft is trimming through the elevators. When the gear goes down you are in direct law and there is no more elevator trim. Although the PFD will now say ‘Use Man pitch Trim’, this isn’t actually available as there is no stab trim available.
The 1, 2, 3, GD technique gets it as close to trimmed as possible to make it easier to fly.
Which hydraulic services power the ailerons?
G+B
