The auto flight system includes the computers and servo systems that automatically control the flight of the aircraft. The computers use data from different sources and feedback circuits to control direction, heading, attitude, altitude, and speed.

The automatic flight control system (AFCS) consists of the flight director, autopilot and yaw damper functions.

The flight director (FD) supplies the calculated steering commands to:

• Electronic flight instrument system (EFIS): The pilot and copilot PFDs display the FD command bars and mode indications
  
  
• Autopilot: If the autopilot is engaged, it uses the steering commands to fly the aircraft automatically. If the autopilot is not engaged, the pilot uses the FD command bars on the PFD to fly the aircraft manually

Mode select pushbuttons on the guidance panel (GP) set the flight director mode of operation.

The autopilot (AP) operates the flight control surfaces to fly the aircraft automatically. The autopilot uses steering commands from the flight director and operates the servos to make the aircraft fly the correct pitch/roll attitude to follow a specific flightpath.

The yaw damper (YD) provides stability augmentation about the yaw axis (Dutch roll) and turn coordination.

The yaw damper uses signals from the flight guidance computers (FGCs) and moves the rudder linear actuators (yaw dampers) to control the yaw of the aircraft. The autothrottle system also provides an electronic engine trim system (EETS). The EETS provides limited authority EPR trim, N1 and N2 synchronization over the full flight regime.