Scale appearance is just that. Your plane must be a scale of whatever documentation you bring. If the documentation is in "error," it should not matter. You're scale building skills are in question, not the variances in documentation that happen to be in the public domain. As far as margins of error, 1% can be overly generous. On a 100" wingspan plane, a 1" error would be ridiculous. I would rather consider a standard to be aligned with the scale itself. For example, the margin for error on a 1/8 plane is 1/8", for a 1/4 plane, 1/4", etc.

Scale flying is another matter. Flak said it best: "The aircraft reduces in size, but the air molecules don't."

Scale flying of a scale-appearance airplane CANNOT BE DONE.

Here's why:

Reynold's Number (RN) for minature (scale) airplanes is dramatically different than for their full-scale counterparts. Airfoils of the same section at different scales (different RN) have different aerodynamic properties (i.e., cL, cD). Also, of course as you scale a plane up, areas increase as a square of the scale and mass as a cube of the scale (please don't quibble about differences in the mass of aluminum and balsa). Thus, the wing loading is also vastly different between scale and full-scale. Then, there is propeller performance (jet guys, please cut me slack), which for the same basic aerodynamic reasons is also vastly different (although most won't notice the difference in RPM )

Taking all this into consideration, in some cases, pilots will be able to fly their scale bird at "scale speed." If that is the case, it is also most certainly the case that the attitude of the plane is not the same as would be for the full-scale. For example, to fly a scale plane at a "scale" landing speed, your angle of attack would be higher (to achieve the necessary lift) than that of the full-scale (although some might argue that a few degrees of AOA is not very noticable). When I've heard people say, "that plane looks great flying at a scale speed," they mostly mean it looks good going relatively slow, and this is a VERY subjective judgement.

"Scale" should only apply to appearance, objectively judged against documentation. Alternatively, scale flight should be considered a separate objective/category, so airfoils, wings, and control surfaces can be modified to produce more "scale" flying characteristics.

- George