smjmitchell wrote...

I agree there is no way that you can accurately simulate the behaviour of
an
airplane without the use of derivatives.

That's not my point. My point is that if you're going to trust
the results of _any_ design and analysis software you better
understand what it can do and how it does it. Particularly if
your design steps outside the bounds of what's 'typical' and thus
might violate some of the assumptions that went into the software.
Kinda what you said early on, I think.

All the "real" simulators work this way.

Quite a few of very good sims use the base parameter in something
like a table lookup, and avoid stability derivatives for anything
but linear analysis.

Dave 'Bode' Hyde