Gentlemen,I have read quite some threads about S-turns, related most of the time to ASA; the pmdg MD 11 and FsX.Today however I had a firsthand experience.I am using Fs-9 on a Vista 64 bit PC (so far with hardly any issues). On a client Laptop, I am running ActiveSky 6.5(build 552) trough Wideclient/wideserver.Since I use all this laptop for all other 'side'programs like Flightsim Commander, Navigraph, FlightTracker, and since I have two separate harddisks onwhich I have installed Fs-9 on the first one and Fs-X on the second one, I have also installed ActiveSky X on that laptop.An hour ago, I took off in a 747F (PMDG) from KATL for a flight to Boston Logan. Right from the start it was obvious that something was, let's say, not normal.Right from gear up untill I shut the simulator down in frustration, the aircraft had a difficult time to keep on track. It kept going from left to right to left of the planned route. When reaching cruiselevel (FL410) about halfway between two waypoints, it just turned right and kept on turning....Ok, there was a moderate wind of about 15 Kts from the left but nothing spectacular. Now, I am wondering if the 'double' installation (both ActiveSky 6.5 AND ActiveSky X) on the laptop could be the cause of this behaviour.Or is there something I am missing...Luc BrusselmansBelgium

Hi Luc,No its not the dual install.Try ASX with a default plane and see what happens.Please let us know.Thanks,

Jim,Will try that out later this week. My regular job takes my time for a couple of day so no flying time for me I'm afraid.I have tried a few other suggestions that I found.So, when I disable all 'weather-related' effects in fsuipc (I have the paid-for version), it seems that the problem goes away.The strange thing is that I have NEVER done that before and I had never that kind of a problem.So now I am wondering if there has been some changes to the weatherdata itself....I'm quite sure that you have checked that out for yourself.Anyway, I'll keep you informed when I get back to my flying on thursday or friday.ThanksLuc BrusselmansBelgium