I just posted an updated AD-6 that is meant to work with FlightGear post-2.0. I'm calling that "2.0+". This model incorporates the "simulation/sim-time-sec" change mentioned below. It also has a propwash feature that allows the horizontal tail to react to propwash. For example, if you gun the engine and apply nose down elevator you can lift the tail wheel off the ground. You can also flip the airplane up onto the nose, so be careful.
The propwash is not seen by the vertical tail yet. My first attempt at that resulted in a bad reaction between the tail forces and the tail wheel, which caused the airplane to hop and spin around.