Appraisal of Method of Flutter Analysis Based on Chosen Modes by Comparison with Experiment for Cases of Large Mass Coupling

Donald S. Woolston · Harry L. Runyan

Ene 1949 · National Advisory Committee for Aeronautics

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The present paper reports the results of a series of flutter studies including comparisons of experimental results with calculations based on a Rayleigh type analysis, in which chosen modes are assumed. The model studied was a straight uniform cantilever wing of high aspect ratio and carried a single concentrated weight An extensive set of experimental flutter data existed in which the mass coupling varied over a wide range. The theoretical results of a differential-equations approach, not requiring chosen modes, in which good agreement with experimental results had been obtained were also available for a number of these cases. An unusual opportunity was therefore afforded to appraise the validity of the assumptions involved in the more universally applicable Rayleigh type analysis. In general, a deterioration in agreement between the experimental and the approximate theoretical results is noted as mass coupling increases. Computed results are found to be high, that is unconservative, for weights ahead of the elastic axis but conservative for weights behind the elastic axis.