Definition

A flight control module (FCM) is an element in fly-by-wire systems like those installed in the Embraer 170/190 series aircraft. In the Embraer system, four flight control modules provide software-based assistance to a series of actuator control electronics (ACE) units. Fly-by-wire is an electronic system that replaces conventional control cables. In the Embraer 170/190 series, all flight controls are fly-by-wire except the ailerons.

Description

According to the Embraer 170 systems manual, the FCMs receive input through a communications bus. Inputs come from the following sources:

• Smart probes, which are a combination of a pitot tube, a static air source, and an angle-of-attack sensor.
• An internal reference system (IRS), which provides aircraft attitude and acceleration data.
• A proximity sensor electronics module (PSEM), which provides weight-on-wheels and ground spoiler position data.
• Brake control modules (BCM), which provide wheel speed signals for ground spoiler deployment.
• Full authority digital electronic controls (FADEC), which provide thrust lever angle data.

The FCMs combine these data inputs to provide the flight control system with the following high-level functions:

• Elevator control modulated according to airspeed.
• Autothrust compensation for elevator control.
• Mach trim and autopilot trim.
• Angle-of-attack limiting.
• Rudder control modulated according to airspeed.
• Rudder flight authority.
• Yaw damper and turn coordination.
• Roll spoiler scheduling with airspeed and speed brake deployment.
• Automatic spoiler deployment at high Mach.
• Configuration change compensation for the horizontal stabilizer.

When the above functions are operating, this is described as "normal mode." When the FCM is inoperative, this is described as "direct mode" of the flight control system. High-level functions and the autopilot are not available in direct mode. The flight control module and the fly-by-wire system can always be overridden by pilot inputs.