Notes on the approximate solution of lifting-surface theory used in the RAE standard method

Abstract

The downwash induced by planar vorticity distributions has been computed by exact linear theory and by the R.A.E. Standard Method to examine the accuracy of the approximate method. The results on wings of infinite span with load distributions which are uniform across the span are used to derive a modification of the downwash equation of the approximate method. It is shown that this modification can explain some of the difference between the exact and the approximate results for the spanwise CL distribution of a plane wing of infinite span at an angle of incidence. The downwash distributions on finite wings of constant chord, unswept and sweptback by 45 degrees, with given load distributions, computed by the exact and the approximate method are compared. The lift distribution for wings of given shape derived by the approximate method is also compared with more accurate results.