I am looking for a way to control flightgear by telling it the position (velocity and acceration too) and the orientation. Has anyone done this who can help? Does anyone have ideas? The methodology behind this is to have simulink (matlab control program) receive inputs from control surfaces and then output onto a 3d visualization in flightgear.

I think this topic has come up a few times on the FlightGear user/developer mailing lists.Try having a look at the mailing list archives (don't know the url off-hand but you should be able to find them via the FG web-site (www.flightgear.org)If you can't find an answer there try posting on the user or dev lists.