29 Hydraulic Flashcards
Which systems have an accumulator?
All three!
What is the hydraulic system pressure normally? (and when supplied by the RAT?)
3000psi +/- 50psi
(2500psi if supplied by RAT)
When does the PTU kick in?
With a difference of 500psi between Green/Yellow system
What are priority valves used for in the hydraulic system?
To cut off hydraulic power to heavy load users if hydraulic pressure in a system gets low
Which are the heavy load users that the priority system can isolate?
Green: Landing Gear, Slats + Flaps
Blue: Emer Gen, Slats
Yellow: Flaps
Which hydraulic system has a hand pump and why?
Only the yellow, for the cargo door
On the HYD SD page, what does the circle represent towards the bottom of the Green and Yellow systems?
The hydraulic fire shut off valve (controlled through FIRE PB)
What do the squares on the HYD SD page system lines represent?
Engine 1 + 2 (G + Y) engine driven hydraulic pumps, and the blue electric pump
Which systems use green hydraulic pressure to operate?
Landing Gear
Slats and Flaps
Rev Eng 1
Normal Brakes
Yaw Damper 1
Rudder
Stabiliser
L Elevator
L + R Spoiler 1 + 5
L + R Aileron
L + R Slat WTB
R Flap WTB
Which systems use yellow hydraulic pressure to operate?
Flaps
Nose Wheel Steering
Alternate/Parking Brake
Rev Eng 2
Yaw Damper 2
Rudder
Stabiliser
R Elevator
L + R Spoiler 2 + 4
L Flap WTB
Which systems use blue hydraulic pressure to operate?
Emer Gen
Slats
Rudder
L + R Flaps WTB
L + R Slats WTB
L + R Elevator
L + R Spoiler 3
L + R Aileron
Can systems be recovered in a green and yellow hydraulic system failure? How?
Engine driven pump fail? Possibly use yellow electric pump
Low reservoir air pressure? System recoverable at lower altitudes
Reservoir overheat? Useable for approach once cooled
What are the key considerations for a green and yellow hydraulic system failure?
Stopping problem (landing distances almost triple)
Alternate law (direct law at gear down)
Gravity gear extension QRH
Flaps/slats locked QRH
Some systems may be recoverable
Can systems be recovered in a blue and yellow hydraulic system failure? How?
Engine driven pump fail? Yellow electric pump or RAT for blue system
Low reservoir air pressure? System recoverable at lower altitudes
Reservoir overheat? Useable for approach once cooled
What are the key considerations for a blue and yellow hydraulic system failure?
Normal law (but without autopilots)
Gravity gear extension QRH (to protect green)
Nose wheel steering is lost
Can systems be recovered in a green and blue hydraulic system failure? How?
Blue electrical pump fail? RAT out
Low reservoir air pressure? System recoverable at lower altitudes
Reservoir overheat? Useable for approach once cooled
What are the key considerations for a green and blue hydraulic system failure?
Handling problem (gear at 200kts)
Aircraft sluggish
Gravity gear extension QRH (at 200kts)
Flaps/slats locked QRH
What should you turn off if you have a G hydraulic low level or low air pressure?
The PTU to prevent it overheating or damaging the other system, and the green engine 1 pump
What should you turn off if you have a Y hydraulic low level or low air pressure?
The PTU to prevent it overheating or damaging the other system, the yellow engine 2 pump, and the yellow electric pump
Typical hydraulic pressures? (With RAT operating?)
3000psi +/- 200psi (2500psi)
How does hydraulic system generate pressure?
Green- engine 1 driven pump
Yellow- engine 2 driven pump (or electric pump/hand pump)
Blue- Electric pump (or RAT)
PTU can pressurise green or yellow system in event of failure of engine pump
What is the hydraulic accumulator and which system supplies it?
Accumulator is a way of storing hydraulic pressure when there is no other pressure available (parking brake)
Powered by yellow
How are reservoirs pressurised?
Bleed air from engine 1.
If engine 1 failed, uses crossbleed air from engine 2.
Prevents cavitation
Which systems have fire shut off valves?
Yellow and green
How does PTU function during engine start procedure?
PTU inhibited during first engine start, self tests during 2nd engine start
When does PTU operate?
Operates when differential pressure of more than 500psi between yellow and green.
Inhibited during 1st engine start and for 40s after cargo door ops
