The airplane has three independent hydraulic systems: left, right, and centre. The hydraulic systems power the:

  - flight controls
  - leading edge slats
  - trailing edge flaps
  - landing gear
  - wheel brakes
  - nose wheel steering
  - thrust reversers
  - autopilot servos
  - tailskid (757-300 only)

Flight control system components are distributed so that any one hydraulic system can provide adequate airplane controllability.

Hydraulic fluid is supplied to each hydraulic pump from the associated system reservoir. The reservoirs are pressurised by the bleed air system.

The Hydraulic Control Panel is located on the Overhead Panel.


The top row of lights are the system pressure lights (marked SYS PRESS) for each hydraulic system. When illuminated (amber) the respective system pressure is low.

The second row of lights are the reservoir low quantity lights (marked RSVR) for each hydraulic system. When illuminated (amber) the reservoir quantity or pressure is low in that hydraulic system.

The switches on the hydraulic panel are for the left and right engine hydraulic pumps (marked L and R ENG) and both the left, right and centre (two) electric hydraulic pumps (marked ELEC).

The switches are off when ON is not visible on the switch itself. Switching them on pressurises the hydraulic pumps for the respective hydraulic system (note that the engine pumps only work with the engines running).

Each switch incorporated an amber low pressure light (marked PRESS), which illuminate to indicate low pump output pressure.

Below each switch an amber pump overheat light (marked OVHT) indicate high pump temperature.


The Status Display shows the hydraulic fluid quantities on the top row (marked HYD QTY), 1.00 being the normal service level. RF in magenta is displayed when the reservoir requires refilling.

Hydraulic pressures are also shown on the status display on some aircraft (as fitted), marked HYD PRESS, displaying the pressure in psi of the pump supplying the highest pressure to the respective system.

Two additional controls for the hydraulics system are the Power Transfer Unit (PTU) switch, located on the Accessory Panel, and the Ram Air Turbine (RAT) switch, located on the overhead panel.

The left hydraulic system powers:

  - flight controls
  - flaps and slats
  - landing gear
  - alternate brakes
  - nose wheel steering
  - left engine thrust reverser
  - hydraulic driven generator
  - tailskid (757-300 only)

The system consists of a reservoir, engine–driven pump, electric motor–driven pump, and a power transfer unit (PTU) pump.

Hydraulic fluid is supplied to each hydraulic pump from a reservoir. The reservoir is pressurised by the bleed air system. A quantity measuring system provides information to the EICAS status display. RF displays when a reservoir requires refilling prior to dispatch. The RSVR light illuminates and the EICAS advisory message L HYD QTY displays when the reservoir quantity is low. The RSVR light also illuminates and the EICAS advisory message L HYD RSVR PRESS displays when the reservoir air pressure is low.

The reservoir maintains reserve hydraulic fluid for use by the PTU in the event of a left system hydraulic leak.

Fluid for the engine–driven pump flows through a shutoff valve controlled by the engine fire switch. Pulling the fire switch shuts off the flow of fluid to the engine pump and depressurises the pump.

The primary hydraulic system pump is an engine–driven 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.

An electric motor–driven pump provides additional hydraulic power.

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.

The PTU is a hydraulic motor pump which transfers hydraulic power from the right system to the left system. The PTU is automatically activated if the left engine fails or the left engine–driven pump pressure is low. When activated, the PTU supplements the left hydraulic system electric motor–driven pump to operate the following:

  - flaps and slats
  - landing gear
  - nose wheel steering
  - hydraulic driven generator

PTU operation is inhibited if the right engine is not operating.

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 on some aircraft (as fitted). When the engine–driven and electric motor–driven pumps are inoperative, the EICAS status page displays the PTU output pressure.

The right hydraulic system is similar to the left system. The right system powers:

  - flight controls
  - normal brakes
  - reserve brakes
  - right engine thrust reverser
  - power transfer unit (PTU)

The system consists of a reservoir, engine–driven pump, and an electric motor–driven pump.

The right reservoir is similar to the left system. The associated EICAS messages for low reservoir quantity or low reservoir air pressure are R HYD QTY and R HYD RSVR PRESS.

The reservoir maintains a reserve hydraulic fluid for use by the reserve brakes in the event of a right system hydraulic leak.

The right engine–driven pump is identical to the left system. The associated EICAS messages for low pump output pressure or high pump temperature are R HYD ENG PUMP and R ENG HYD OVHT

The right electric motor–driven pump is identical to the left system. The associated EICAS messages for low pump output pressure or high pump temperature are R HYD ELEC PUMP and R ELEC HYD OVHT.

The right system pressure indications are similar to the left system. The associated message for low system pressure is R HYD SYS PRESS.

Pushing the RESERVE BRAKES switch configures the hydraulic system to use the reservoir’s reserve fluid, activates the electric motor–driven pump regardless of the pump switch position and isolates the pump output power to only the normal brakes.

The centre system powers only flight controls. The system consists of a reservoir, two electric motor–driven pumps, and a ram air turbine (RAT) pump.

The centre reservoir is similar to the left system. The associated EICAS messages for low reservoir quantity or low reservoir air pressure are C HYD QTY and C HYD RSVR PRESS.

The reservoir maintains reserve hydraulic fluid for use by the ram air turbine in the event of a centre system hydraulic leak.

The two centre electric motor–driven pumps are similar to the left system pump.

The C2 pump may be load shed automatically to reduce electrical loads. The associated EICAS messages for low pump output pressure or high pump temperature are C HYD ELEC 1, C HYD ELEC 2, C HYD 1 OVHT, and C HYD 2 OVHT.

The centre system pressure indications are similar to the left system. The associated message for low system pressure is C HYD SYS PRESS.

The RAT, when deployed provides hydraulic power to the flight controls portion of the centre hydraulic system. The RAT provides adequate hydraulic power at speeds above 130 knots. In flight, the RAT deploys automatically when both engines fail.

The RAT can be deployed manually by pushing the RAM AIR TURB switch. The UNLKD light illuminates and the EICAS advisory message RAT UNLOCKED displays when the RAT is not stowed and locked. When the RAT is producing pressure the ram air turbine PRESS light illuminates. Once deployed, the RAT cannot be stowed in flight.