Flight Controls - Elevators Show Schematic only

Pitch Control

Elevators Hydraulics Hydraulics default

The pitch control surfaces consist of two elevators and a Stabilizer. A Mach speed trim system operates the stabilizer to improve speed stability.

Note : The 757 does not have a "Pitch Enhancement System".


Elevator

Moving the control column signals hydraulic actuators to move the elevators. Elevator positions are shown on the EICAS status display. Separate pointers indicate the left and right elevator deflection. A full-scale indication corresponds to the maximum elevator deflection.

If one control column should jam, applying significant forward or aft force to the other causes the two columns to override. Pitch control is then available using the free control column path.

Elevator Feel

Two elevator feel systems provide artificial feel forces to the pilots control columns. Mechanical springs provide feel following a loss of the Center and Right hydraulic systems.

Elevator Asymmetry

AMM Elevator asymmetry between captain's and first officer's control system is limited at the aft quadrants by an electrical actuator. The actuator uses an electric motor to position a stop which limits the relative motion between the captain's and first officer's aft quadrants. The motor operates in response to an extend or retract discrete from the Stabilizer/Elevator Asymmetry limiter Module (SAM). Switches on the motor output provide signals back to the SAM to indicate if the motor is in the extended or retracted position. The system is operational full time. Asymmetry is limited to 24 degrees at low speeds and 8 degrees at high speeds.

Elevator asymmetry is indicated by the ELEV ASYM EICAS status message.

Fault Indication

AMM Elevator control system fault monitoring is provided by the Stabilizer/Elevator Asymmetry limiter Module (SAM) and EICAS system. The SAM provides fault monitoring of the elevator/asymmetry limiter actuator.

A PCU monitor system is installed to monitor hydraulic pressure in the Power Control Actuators (PCAs) to detect and warn of an excessive pressure differential (above 1140-1350 psi) between the PCAs (PCA force-fight).

Stabilizer