on the following route flown twice to check out whether the issue recurs the aircraft suddenly turns an abrupt left despite being on auto pilot, getting it back to heading requires off with auto pilot, manually manouvering the acft to the correct heading and when the adrenaline has returned to normal on with auto pilot.details of the flight:route: EGCC-EKBIfl: 370winds calmframe rates 25rapid turn to left bank angle warning around 75nm before Descent.it only happens on this route so perhaps it is a navigraph issue, although route is clear on the pfd??only add on is ultimate traffic and none was visible as time of flight around 10pm GMT.tried the route with the level d 767 with no issues, some waypoints, height etc.any clues?lastly all the best to the forum for a peaceful and rewarding 2012.Mel

Have you tried using fsuipc? Fsx weather has alot of problems with ngx and for me, fsuipc fixed my problem which was similar to this. also, make sure you uncheck "download winds aloft" in the fsx weather menu. Happy New Year!

Turbulence issue, turn it off.