When you specify the wing area of a biplane, do you specify the planform area (the projected area) or do you specify the effective area of both the wings?

  • $\begingroup$ I could have sworn we had this exact question, or a very similar one about interference and effective wing area, but I can't find it. $\endgroup$ Oct 25, 2019 at 7:59

1 Answer 1


It's a mixture of both: You add the projected area of both wings, measured separately, without overlap.

The effective (wetted) area is used for friction drag calculations only.


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