I've been using FS for nearly a month now and I've found what has been causing the stutters in the sim, it's the AI traffic. Turn it off and you get a very smooth ride, but put it on and and the sim stutters. Intially the stutters were not two bad and I put up with them, but when I installed volume2 of British airports the sim was unflyable, in the British area. I turned off AI traffic and there was no problem.I decided to wait for the British airports patch to see if it would help, but it didn't. At the momemt it's either fly without AI or without British Airports, and I fly without British Airports. I have not touched anything to do with the AI aircraft they are all the default ones.I like to keep the AI on a fairly high setting because I think it is a brilliant feature. Does anyone have any idea why the AI is causing these massive stutters? the problem never appeared FS2002.

Do you use default AI or addon AI, like Project AI or Ultimate Traffic? It's self evident why default AI cases a frame rate drop, as it uses complex aircraft. Addon aircraft specially made for AI are much simpler, but you only see them at distance, so it doesn't matter.- Oyvind

I use all the default aircraft with no addons. It's not the frame rate drop that bothers me it's the fact that the sim stutters. Also do you know of any programs that exist to easily replace all AI lfight plans, rather than replacing each one at a time?

I guess stuttering and framerate are related somehow. The first thing you should do is to get rid of the default traffic, unless you like Landmark, Orbit and the others. To replace all AI in one simple step you would have to get a program like Ultimate Traffic (payware). But you could also download all the freeware auto installers at www.projectai.com . They will replace the default traffic with more realistic schedules based on real airline traffic. Or if you feel like doing a lot of work you could download the "most realistic ai" master file here at avsim and find your own AI aircraft from FSPainter of AI Aardvark. This is very time consuming, but ultimately gives you the best results.- Oyvind

thanks for your help.