HYDRAULICS Flashcards
How many hydraulic systems does the aircraft have?
3 Hydraulic systems: Blue, Green and Yellow. Each system has its own reservoir.
What is the normal system operating pressure?
3000 PSI, 2500 PSI when powered by RAT.
Can fluid be transferred from a system to the other?
NO
Which type of pump do the systems hold?
GREEN: 1 pump driven by engine 1.
BLUE: 1 electric pump, 1 pump driven by the RAT to pressurize in emergency.
YELLOW: 1 pump driven by engine 2, 1 electric pump that allows to pressurize the system on the ground with engine stopped. 1 hand pump to operate the cargo doors if no electric power is available.
Can we transfer pressure from a system to the other?
A Power Transfer Unit allows the yellow system to pressurize the green system and vice versa. Come on automatically when differential pressure of more than 500psi between both systems.
The PTU is inhibited during the first engine start and automatically tested during the second engine start.
Explain the RAT.
A Ram Air Turbine coupled to a hydraulic pump allows blue system to work in electrical emergency or both engines fails. Deploys automatically if AC BUS 1&2 fail. Can be dropped manually and stowed only on ground.
How is the pressure maintained constant in each system?
Via accumulators that maintain the pressure by covering transient demands during normal operations.
What is a priority valve?
Priority valves cut off hydraulic to heavy load if pressure in a system gets low.
What is a fire shut off valve?
Green and Yellow fire shut off valves upstream off the engine driven pump in case of fire. Can manually operate it vie FIRE PB.
What is a leak measurement valve?
Upstream of the flight controls in each system located on the maintenance panel, measure leakage in each system.
Do the systems hold filters?
- HP filters on each system and on the reservoir filling system and the normal braking system
- return line filters on each line
- case drain filters on engine pumps and the blue electric pump (which permit maintenance crew to monitor pump wear by inspecting the filters for the presence of metallic particles).
How are the reservoirs pressurized?
Normally, HP bleed air from engine 1 pressurizes the hydraulic reservoirs automatically.
If the bleed air pressure is too low, the system takes bleed air pressure from the crossbleed duct.
The systems maintain a high enough pressure to prevent their pumps from cavitating.
Which systems are upstream of the priority valves?
GREEN: Landing gear and slats and flaps.
BLUE: EMER GEN and slats.
YELLOW: Flaps.
When does the ENG PUMP Fault light come ON?
This amber light comes on, and the ECAM caution appears, if :
The reservoir level is low
The reservoir overheats
The reservoir air pressure is low
The pump pressure is low (inhibited on the ground, when the engine is stopped).
This light goes out, when the crew selects OFF, except during an overheat. (The light stays on as long as the overheat lasts).
When does the BLUE PUMP fault light come ON?
This amber light comes on, and a caution appears on the ECAM, if :
The reservoir level is low
The reservoir overheats
The air pressure in the reservoir is low
The pump is delivering low pressure (inhibited on the ground, when the engines are stopped)
The pump overheats.
The light goes out, when the crew selects OFF, except during an overheat. (The light stays on as long as the overheat lasts).
