A350
Engine Driven Pump (EDP) Operation
The hydraulic system can be pressurized by the Engine Driven Pumps (EDPs).There are two EDPs per engine so two per hydraulic system. The Engine Driven Pumps (EDPs) can be in three different states:
•pressurized,
•Depressurized
•declutch
The pressurization and depressurization modes are controlled from the P/Bs installed on the Main Hydraulic Panel. One P/B per EDP is used to select its depressurized mode. The normal state of the EDP P/B is pushed. In this condition there is no indication at the P/B and when the engines are running the system is pressurized automatically. Pressing the P/B causes the related EDP to operate indepressurized mode.
P/B's with red arrows on pic.
The blue arrows are showing grnd maintenance hyd switches.
To put each EDP in the depressurized mode, you must energize the EDP solenoid valve.
This solenoid valve can be energized:
•Manually by a pump OFF pushbutton switch (direct wiring)
•Automatically when the related engine FIRE pushbutton is pressed (due to Fire SOV closure)
•Automatically by the Propulsion Control System(PCS)in case of engine start. The EDPs will pressurize again after engine start. N3>50%(Flight and GND)
(It wil lnot be depressurised during DRY Crank)
•Automatically by the FQMS if there is a fuel low level and a hydraulic temperature of more than 80 °C. Automatic depressurization is only done if the second EDP of the hydraulic system, which is on the opposite engine, supplies pressure (pressure is measured at the EDP HP manifold). OVHT Threshold in RESERVOIR is now modified from 95 deg C to 115 deg C.
Last edited by spannersatcx; 16th January 2018 at 12:59.
Reason: add pic