Flight Controls - Ailerons

Introduction

The roll control surfaces consist of hydraulically powered ailerons and spoilers that are controlled by rotating either Control Wheel.

Roll Control

An aileron is located on each wing on either side of the outboard trailing edge flap. Two hydraulic actuators are used for each aileron. Aileron surface deflections are proportional to control wheel displacement. Spoilers begin to extend to augment roll control after several degrees of control wheel rotation. Control wheel forces increase as control displacement increases.

The control wheels are connected so that, if one control wheel jams, using significant force causes the control wheels to override. Roll control is then available using the free control wheel.

Ailerons

Aileron positions are shown on the EICAS status display. A full-scale indication corresponds to maximum aileron deflection.

Aileron Trim

Dual aileron trim switches located on the aft aisle stand must be pushed simultaneously to command trim changes. The switches provide arming and direction signals to an electric motor that repositions the aileron neutral (trimmed) point. Hydraulic power from one of the three Hydraulic systems is necessary to accurately set aileron trim.

The amount of aileron trim is indicated on a scale on the top of each control column.

Note: If the flight crew inadvertently activates aileron trim while an autopilot is engaged, the repositioning of the aileron neutral point is not apparent to the crew. When the autopilot is disengaged, the control wheels and ailerons move to the new (possibly undesired) neutral point and the airplane will roll proportional to the amount of trim input.

Spoilers