This note shows how the Hill Aero-isoclinic Principle1 works out in practice for a swept wing, fixed at the root and having straight flexural and inertia axes. The conditions assumed are readily represented in a wind-tunnel model and experiments by Lambourne2 show good agreement with theory.nThe further aft the flexural axis from the quarter-chord position, the smaller is the sacrifice of wing torsional stiffness entailed in making a swept wing isoclinic, and previous work has on that account taken a far-aft position as a reasonable basic assumption, with the result that, to avoid aero-elastic instability, a well-forward position for the inertia axis is arrived at. It is shown here, however, that by still further sacrifice of torsional stiffness (whether practicable or not) it is possible to reduce the gap between the two axes very considerably and so simplify one aspect of the constructional problem.
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