I was flying out of BUF today and encountered the autopilot making what became very wild S-curves. I've heard of such behavior in other PMDG aircraft using ActiveSky products. However, I was using default FSX weather "heavy snows" theme to practice some cold weather procedures (in fact, typically on my other flights I use ASX without problem).I was in the 737-800WL and departed runway 5 on the BUF3.YXU DP. My FD was set up with A/T in TO/GA, HDG SEL armed and VNAV armed. Once passing 3,000' AFE I selected direct to YXU through the FMC legs page and selected LNAV (following BUF3 DP with NADP1). I then selected CMD A while bringing the flaps up on schedule. Once above 10,000' MSL, the aircraft began making S-curves turning 30-40 degrees off to the left, then right, and so forth. Eventually, it ended up in a 360 degree turn and the AP was using 45+ degrees of bank. The autopilot was following the FD cues.Any idea what was going on here? Has anyone encountered this before. I never had this problem before. The only thing I can think of that was different is that this is the first flight where I needed anti-ice on departure. I've also been flying RNAV departures recently, but I think I've used HDG SEL for vectored departures as well.Eric Szczesniak

I had the same thing Over England using Activesky, Autopilot went into 45degree banks and held it until stall, aircraft would barely fly even after taken off Autopilot and hand flown

There are a hundred and one posts about this situation and how to adjust things using FSUIPC, FSX settings and AS settings.

There are a hundred and one posts about this situation and how to adjust things using FSUIPC, FSX settings and AS settings.

Really? Because all of those posts I've found specifically pertain to use of some version of ActiveSky. As I layed out in my post, I was NOT using any version of ActiveSky on this flight, only a default FSX weather theme.Eric Szczesniak

Really? Because all of those posts I've found specifically pertain to use of some version of ActiveSky. As I layed out in my post, I was NOT using any version of ActiveSky on this flight, only a default FSX weather theme.Eric Szczesniak

It isn't just with ase. I used to get that in the 744 and I only got a copy of ase 2 days ago.

Try This .Go to fsx config files weather turbulence file set to 0.500000

Really? Because all of those posts I've found specifically pertain to use of some version of ActiveSky. As I layed out in my post, I was NOT using any version of ActiveSky on this flight, only a default FSX weather theme.

The S-Turn/Curve has Nothing to do with Activesky or Rex. The problem is FSX itself and its poorly coded weather and turbulence. The reason you probably haven't seen it before is that it usually only happens with planes that are very sensitive such as the PMDG planes and all of them do this. Activesky and FSUIPC are not the cause but rather the solution.Go to the link below and adjust your settings accordingly. There are 3 scenerio's discussed there. Yours would be the FSX only option at the bottom.Short quick solution for your situation is adjust FSX.cfg turbulence settings and in FSX under Weather Tab check the box that says disable turbulence and thermal effects on aircraft. This is not the idea solution but its the only one available to you as you only have FSX. If you had ASE and Registered FSUIPC then you could use the less drastic solutions.http://forum.avsim.n..._1#entry21277451) FSX with ASE and Registered FSUIPC2) FSX with FSUIPC3) FSX only

Problem with tracking problems in other PMDG aircraft, is linked to a bad FS Path in the registry. You can correct that with the Flight1 Registry repair utility.You can get it herehttp://www.flight1.com/view.asp?page=library

Problem with tracking problems in other PMDG aircraft, is linked to a bad FS Path in the registry. You can correct that with the Flight1 Registry repair utility.

He is talking about something totally different than you are. His problem is the S-turn / Autopilot Hunting issue and it's caused by turbulence.

Registered version of FSUIPC...Tick... suppress turbulence, gusts and variance. Although I believe it's just turbulence thats the issue.Also use the very effective sudden wind shift setting. I use 8 knots per second.No more S-turns or sudden wind shifts.

Not to trivialize the bug, it can be a pain, but I find problems like this interesting. This beast is so automated that when something like this pops up it's a perfect opportunity to take control of the aircraft and return it to stable flight. Call it a simulated panic attack.Bug or not, I am sure this can happen in the real world and the pilot would have to deal with it.I seem to remember an airline flight many years ago where the AP commanded a roll to 90 degrees and then kicked off. I would have loved to hear the cockpit voice recording of that event ... Cpt - What the .... FO - Mommy ... Cpt - got it.Harry Gentilozzi

I finally got around to registering FSUIPC and was getting these S turns on my first flight. I was using wind smoothing in ASE and FSUIPC so I was perplexed. Then I checked off supress turbulence, gusts, and variance. Now I don't get the S turns but I dont get any turbulence either so its like flying with an unregistered copy of FSUIPC all over again. Wondering why I spent the $32 USD now....

I finally got around to registering FSUIPC and was getting these S turns on my first flight. I was using wind smoothing in ASE and FSUIPC so I was perplexed. Then I checked off supress turbulence, gusts, and variance. Now I don't get the S turns but I dont get any turbulence either so its like flying with an unregistered copy of FSUIPC all over again. Wondering why I spent the $32 USD now....

First off FSUIPC offers a whole lot more than just Weather functions. There are a ton of features in FSUIPC that make it worth buying for any serious flight simmer.If you read the updated tutorial you will see am not using FSUIPC Wind Smoothing at all.http://forum.avsim.n..._1#entry2127745The main things to Change for the optimal weather with ASE and FSUIPC is in the tutorial at the link above.In FSUIPC under About Tab you should click on the Box for Weather Settings Off. This will disable all FSUIPC weather. Then go to the Winds Tab and Check only the Turbulence Box. Do Not check Gusts or Variance. This way Activesky is controlling everything weather wise and FSUIPC is only supressing Turbulence. This is what prevents the S-turns. The only other option is to disable Turbulence in FSX which is a far more drastic solution and I don't recommend it if you have the Registered version of FSUIPC.Even though it does not feel like you are getting any turbulence you will still get a little with the FSUIPC option. It will be noticable when you see your tape jumping up and down. It is also more noticable in the 747-400x cause then you can see the wings flexing and bouncing up and down, which is not as noticable in the NGX.Read the tutorial and setup everything as it is layed out and I think you will be happy with the end result. The S-turn is not specific to the NGX alone. Happens with the 747-400 and MD-11 as well. Not sure it happens with any other PMDG products but I would guess so cause they are all sensitive aircraft. FSX does not model turbulence realistically and so your faced with 3 choices. 1) You can hand fly the whole route. 2) You can disable Turbulence and your aircraft will fly straight. or 3) You can deal with the S-turns. Option 2 seems like the only viable solution to me.

Thanks for your response. I read the tutorial and adjusted the settings. I dont have a CH controller or anything fancy. I primarily registered FSUIPC for more realistic winds with ASE. I also felt after using it for so many years I would help support Pete's efforts.

I got rid of all S-turns just with checking "Suppress turbulence" in registered version of FSUIPC. Nothing else. About 30 flights later... no S-turns with PMDG NGX or MD11 (I didn't check J41 and 744 yet). I also use ASE (DWC mode).