[Thee_oddball]

GIGO: wing planforms, props, airfoils, incidences, engine cant, weight, drag data, etc... input all that well and you'll get a pretty accurate flight model. However it won't be perfect because no simulator is, by definition. Modellers tweak the flight model by adjusting these inputs to account for what can't be modelled in order to get closer to published or known behavior. So, X-Plane will tell you to a great extent, but if the input is garbage then the output will be the same.

No, as Brett said above, things like radii of gyration are hard (if not impossible) to find, as are details of propeller twist and aerofoil section, for example. Even things like control surface deflection are often hard to find. Even then, there are always things that you can do in the simulator that you can't in the real thing (by which I mean, the control forces on most aircraft are nothing even remotely like those produced by the spring or force-feedback motors in a joystick).

For detailed comparative analysis of aircraft, you have to fly the real thing. For rough comparison, you might get a basic qualitative feel out of a simulator. If you want to compare, say, a Spitfire and a BF109, they're probably too similar for X-Plane to give a reasonable idea of the differences. You could probably put Spitfire visuals over a BF109 flight model and not notice the difference in terms of handling.

Does anyone here think X-plane could be used toget us %90-95 there in terms of figuring out the handling characteristic of the planes in il2?