Some Notes on the Induced Drag of Nonplanar Ground Effect Wing

It is shown that the curved lifting line theory for a nonplanar wing is not deficient, at least for evaluating the span efficiency factor. It is exactly shown that the span efficiency factor of a hemielliptic front view GEW e(λ, ε) is sym metric for exchange of λ ?? 1/λ, where λ denotes the height ratio, and ε the tip gap angle parameter. This assures the result in our previous paper, from another viewpoint. A simple method is presented, for analysing a nearly flat GEW.