An EMB-140 on autopilot with FMS guidance turned the wrong direction after a 'direct to' FMS selection was made following a change in next fix clearance.
Synopsis
An EMB-140 on autopilot with FMS guidance turned the wrong direction after a 'direct to' FMS selection was made following a change in next fix clearance.
Narrative
While at cruise flight at FL280 and 80NE of a VOR; we were given a clearance to proceed direct to the VOR. Both of us selected DTO (Direct to) on the FMS and verified the new course on the PFD and MFD as a turn to the right. Initially the flight director/autopilot commanded an incorrect turn to the left and did not correct back to the right. After a short period of time; the pilot flying (Captain) overrode the automation and selected 'HDG' mode in an attempt to get the aircraft pointed in the correct direction. After we were approaching a direct course to the VOR; the Center controller issued us a new clearance direct to another VOR and then amended that to a clearance direct to the original one again. The event occurred because the autopilot/flight director commanded a turn in the opposite direction of the actual course displayed on the PFD and MFD. To prevent this from occurring again; I think that it would be a safe practice to turn to the new course in heading mode before selecting 'NAV'.
Second reporter narrative
The EMB occasionally turns the opposite direction in the FMS; but usually only for a second.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.