Well, I got a note back from Cessna and (as I pretty much expected) they were tight-lipped about supplying any aero/mass props data, saying instead that the owner's manual was about all I could get.

After thinking about this some more, there are three possibilities I can see for any perceived problems:

1) The stability derivatives are indeed low-balled. I find this unlikely, as the numbers for rate-damping are in line with other aircraft in the same class.

2) The MoIs are too low. This is possible - I have not yet checked these out, but again I believe we will find these numbers to be pretty good.

3) This one just occurred to me: I wonder if the control inputs from stick and rudder are linear? Or, are they perhaps graduated? In our FCS model, we take the joystick input and map it linearly to the range of values that the control surfaces can see - essentially. It might make sense that for small excursions about center (no control inputs) that control movements are kept small, but as one makes bigger inputs, that the "gain" increases. Does anyone have any comments on this? If this was in fact the case, it would not be difficult to modify our control system to model this.


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