"Sure- flightgear has an interface that allows sending and receiving of the state of the vehicle being simulated (the FGNetFDM structure) and the position of control surfaces and other things (the FGNetCtrls structure).
I have read about Curtis Olson's use of flightgear for UAV development, but didn't see any applications to download to get started working on an autopilot with. So I've started on my…