Hydraulic System - Centre System 
General
The centre system powers only the flight controls.
The system consists of a reservoir, two electric motor-driven pump and a Ram Air Turbine (RAT) pump.
Fluid Supply
Hydraulic fluid is supplied to each hydraulic pump from an independent reservoir. The reservoir is pressurised by the Bleed Air system to ensure positive fluid flow. A quantity measuring system provides information to the EICAS status display. RF displays when a reservoir requires refilling prior to dispatch (quantity < 0.75).
The RSVR light illuminates and the EICAS advisory message C HYD QTY displays when the reservoir quantity is low (quantity < 0.5). The RSVR also illuminates and the EICAS advisory message C HYD RSVR PRESS displays when the reservoir air pressure is low.
The reservoir has a stand pipe to maintain reserve hydraulic fluid for use by the Ram Air Turbine in the event of a centre system hydraulic Leak. With fluid level at the top of the standpipe, quantity is approximately 0.15.
Electric Pumps
The two centre electric motor-driven pumps are similar to the left system pump. The C2 pump is load shed automatically to reduce electrical loads if only one electrical generator is operating and both Electric Pump Switches are ON.
The pump PRESS light illuminates and the EICAS advisory message C HYD ELEC 1 or C HYD ELEC 2 displays when the pump output pressure is low. The pump OVHT light illuminates and the EICAS advisory message C HYD 1 OVHT or C HYD 2 OVHT displays when the pump temperature is high.
System Pressure Indications
The SYS PRESS light illuminates and the EICAS caution message C HYD SYS PRESS displays when the hydraulic system pressure is low.
Hydraulic system pressure displays on the EICAS status page. When both electric motor-driven pumps are inoperative, the EICAS status page displays the Ram Air Turbine output pressure.
