Free Flight, Free Speech

bomber wrote:

Richard wrote:A flat plate normalized by its surface area would be around 1.2; however the Cd is for the entire aircraft in which case using the wing surface area to normalize drag force is going to result in a higher value than for the wings alone.

And that''s the point I'm making.... you can't apply the ground effect to the whole plane Cd.... just to Cdi

I understand your point; but as always with aerodynamics it depends on how it was originally measured / calculated; the normalization process could use anything - it is just by convention that each axes has a standard normalization.

CDi (induced drag) is the drag that is a result of the airflow; compared to CDo (form drag) which is the drag due to the shape; sometimes these are combined into a single Cd.

OK so what we know about ground effect is that it effects 3 properties only

1) Produces a reflected force perpendicular to the ground
2) Reduces the downwash angle coming off the training edge of the wing effectively increasing the angle of attack on the h-stab
3) Reduces induced drag from the wings and h-stab by interrupting the vortex flow along these airfoils.