Hydraulic System - Left System Show Schematic only

Left Hydraulic System

Leak from Left System Center System Right System Shutdown Left Engine Shutdown Right Engine Power Transfer Unit (operates if Left engine failed or Left EDP pressure low) Reserve Brakes Ram Air Turbine (automatically operates when both engines have failed) Ram Air Turbine Manual Deployment Switch Alternate Brakes Left Thrust Reverser Rudder Ratio Landing Gear - Normal System Operation Spoilers Yaw Dampers Ailerons ETOPS equiped aircraft only Flaps and Slats - Normal System Operation Nosewheel Steering Elevators Spoilers Rudder Elevator Feel Stabilizer Ailerons Normal Brakes Right Thrust Reverser Power Transfer Unit Spoilers

General

The left hydraulic systems power the:

 

The system consists of a reservoir, engine-driven pump, electric motor-driven pump and a Power Transfer Unit (PTU) pump.

Fluid Supply

Hydraulic fluid is supplied to each hydraulic pump from an independent reservoir. The reservoir is pressurized 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).

Sys Press Rsvr. The RSVR light illuminates and the EICAS advisory message L HYD QTY displays when the reservoir quantity is low (quantity < 0.5). The RSVR also illuminates and the EICAS advisory message L HYD RSVR PRESS displays when the reservoir air pressure is low.

Fluid for the engine pump flows through a shut off valve controlled by the Left Engine Fire Switch. Putting the fire switch, shuts off the flow of fluid to the engine pump and depressurizes the pump.

Engine-Driven Pump

The primary hydraulic system pump is an engine-driven pump. The engine pump can be depressurized with the engine operating by turning off the engine pump.

The pump PRESS light illuminates and the EICAS advisory message L HYD ENG PUMP displays when the pump output pressure is low. The pump OVHT light illuminates and the EICAS advisory message L ENG HYD OVHT displays when the pump temperature is high.

Electric Motor-Driven Pump

An electric motor-driven pump provides additional hydraulic power and is controlled by an Electric Pump Switch.

The pump PRESS light illuminates and the EICAS advisory message L HYD ELEC PUMP displays when the pump output pressure is low. The pump OVHT light illuminates and the EICAS advisory message L ELEC HYD OVHT displays when the pump temperature is high.

Power Transfer Unit

System Pressure Indications

The SYS PRESS light illuminates and the EICAS caution message L HYD SYS PRESS displays when the hydraulic system pressure is low.

Hydraulic system pressure displays on the EICAS status page. When the engine-driven and electric motor-driven pumps are inoperative, the EICAS status page displays the PTU output pressure.

Hydraulic Driven Generator

The Hydraulic Driven Generator is automatically powered by the Left hydraulic system engine driven pump when electrical power is lost from both main AC buses.

Center System