Generation Flashcards
How is green system pressure generated?
A pump drive by engine 1
How is the blue system pressurised?
An electric pump. In an emergency a pump driven by the RAT pressurises the system.
How is the yellow system pressurised?
A pump driven by engine 2.
An electric pump can also be used to enable the yellow system hydraulics to be used on the ground.
Can also use a hand pump on the ground when no electric pump is available, in order to operate the cargo doors.
What is the role of the PTU?
To enable the yellow system to pressurise the green system and vice versa.
Operates when the differential pressure between the yellow and green system is greater than 500 psi.
Allows green system to be pressurised on the ground when the engines are stopped.
A drop out RAT coupled to a hydraulic pump allows?
The blue system to be pressurised should electrical power be lost or both engines fail.
The RAT automatically deploys if?
AC Bus 1 and 2 fail.
Can the RAT be manually deployed?
Yes, by a guarded switch on the OHP.
It can only be stowed on the ground.
How many accumulators are there?
One for each system.
Helps maintain constant pressure by covering transient demands during normal operation.
Priority valves?
Cut off hydraulic power to heavy load users if pressure in a hydraulic system gets low.
Fire shutoff valves?
The green and yellow systems each have a fire shutoff valve located upstream of its engine driven pump.
Closed when crew select ENG 1(2) FIRE PB.
Leak measurement valves?
Each system has a leak measurement valve upstream of the primary flight controls.
Measure leakage in each circuit.
Can only be closed by operation of the LEAK MEASUREMENT VALVES PB on the maintenance panel.
Filters clean the system in 3 ways:
1) HP filters on each system and on the reservoir filling system and normal braking system.
2) Return line filters on each line.
3) Case drain filters on engine pumps and blue electric pump (permit maintenance crew to monitor pump wear by inspecting the filters for the presence of metallic particles)
What normally pressurised the hydraulic reservoirs automatically?
HP Bleed air from engine 1.
If the Bleed air pressure is too low, the system takes Bleed air pressure from the cross bleed duct.
The system maintains a high enough pressure to prevent the pumps from cavitating.
