dave perry wrote:
Hi All,
snip
Would it not be more realistic to rotate the 3D model about -3 or -4 degrees about the ac3d z-axis.I did not make myself clear in the initial questiion. The video link only detracted from my point. The model in the .ac file is just a rigid body that gets displayed when the fdm says the pitch is zero degrees (or perhaps zero incidence). The fdm then rotates this rigid model for other flight conditions. So if the model starts 3 or 4 degrees too nose high for realistic cruise, it will remain 3 or 4 degrees too high in pitch for all other rotations from the fdm. In particular, it will be 3 or 4 degrees higher than a realistic stall at touch down, burying the tail cone in the runway.
To make this clear, I opened the c172p.ac in ac3d, made a screen capture of the side view, then rotated the model by - 4 degrees and made a 2nd screen capture of the side view and then scaled and combined these into one small .png which is attached.
My only point is that I think the rotated side view pitch (bottom image) looks like a c172p at cruise and the original side view (top image) looks like a c172p in level no flap slow flight. Compare the wing and horizontal stab incidence angles in the two images. In the rotated side view, the horizontal stab is at zero incidence while the non rotated side view shows a noticeable positive incidence for the horizontal stab which would normally require significant up elevator to maintain.
Making this change will be a lot of work since the panel will be messed up. I know because I made a similar rigid rotation correction about a month after I first submitted the pa24-250.
Dave P.
<<inline: c172p-4deg-pitch.png>>
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