Interfering Lifting Surfaces in Unsteady Subsonic Flow - Comparison Between Theory and Experiment,
ADVISORY GROUP FOR AEROSPACE RESEARCH AND DEVELOPMENT PARIS (FRANCE)
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The ever increasing use of highly swept wings, T-shaped tail units and variable geometry wings has rendered it necessary to take account of aerodynamic interactions between the aircraft lifting surfaces in flutter computations and this has given rise to many theoretical developments. However, the unsteady forces thus calculated have seldom been verified in wind-tunnel tests. The author has undertaken to carry out such tests on a half wing unit consisting of a variable sweep half-wing, followed at a short distance by a fixed sweep half tail-unit. These quasi-rigid models are subjected to harmonic pitch and roll oscillations. Up to now, tests have only been performed at low speeds from 20 to 40 ms corresponding to a practically incompressible flow. Such tests should also be conducted at subsonic and supersonic speeds.