Okay, I've been flight testing the SA-43 Hammerhead from Space: Above and Beyond I just picked up off flightsim.com, and everything seems to be working just fine, except for a certain glitch.

Seemingly at random, the a/c would start to 'weave', slipping the nose from side to side.  At first its just a little, and slowly gets worse.  Never happens below 300 kts, but occurs every time if I fly more than a couple of minutes.

I haven't done anything to the original other than change the empty weight and max weight up a bit and the static thrust for the engines up a bit.  I can change the .air file and I know how to edit the .cfg file, so if anyone can point me in the right direction I would sure appreciate it!