My plane keeps making weird turns while flying along a straight airway. I have disabled turbulence in FSX and followed the instructions in AS2012 manual but to no avail.

Make sure you update FSUIPC as well. Also check out this link. http://forums.flightsimlabs.com/index.php?/topic/1947-asa-ase-settings-with-fsuipc-and-fsx/

 

It may help. And do yourself a favor and perform a search; not only on avsim, but even on google. Lots of topics and solutions floating out there.

I did disable FSUIPC as per AS2012 instructions.

There should be absolutely no problems with AS2012 and NGX. Which mode in AS2012 are you using? DWC has enough smoothing and flight should be flawless, while with Smooth Clods Transitions and Standard there will be rapid changes in wind direction and speed. There was bug in some older versions of FSUIPC, which could lead to s-turns, the walkaround was to set all weather options to off (in FSUIPC cfg), this bug was fixed long time ago, but you can always try flight with FSUIPC removed from FSX to check it out.

I've been having the same issues for a while as well. Here's what I did the day before yesterday.

 

In FSUIPC I set icing to 1, I disabled random icing in clouds as well, I also suppressed cloud turbulence and turbulence in general. I have flown two flights and have not seen the problem since.

 

I will be adding the FSUIPC items back one by one. I am almost certain it has to do with icing because when I disengage the autopilot and fly manually, I get uncommanded left and right upsets. So I know it's not the autopilot correcting for winds or temps, it's a control issue.

 

On my next flights I will re-disable turbulence suppression in clouds and in general and see if the problem re-appears.

On a side note, I am using AS2012 in high altitude mode. Do not know if that makes a difference in this particular case.

 

Try it out and let us know.

 

Cheers,