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ESTIMATION OF ROTARY STABILITY DERIVATIVES AT SUBSONIC AND TRANSONIC SPEEDS
ADVISORY GROUP FOR AERONAUTICAL RESEARCH AND DEVELOPMENT PARIS (FRANCE)
The estimation of subsonic rotary stability derivatives of wings is treated. The unsteady potential flow problem is solved by a superposition of steady-flow solutions. Numerical results for the damping coefficients of triangular wings are presented as functions of aspect ratio and Mach number, and are compared with experimental results over the Mach number range 0 to 1. Experimental results are used to point out a close correlation between the non-linear variations with angle of attack of the static pitchingmoment curve slope and the damping-in-pitch coefficient. The underlying basis for the correlation is found as a result of an analysis in which the indicial function concept and the principle of superposition are adapted to apply to the non-linear problem. The form of the result suggests a method of estimating non-linear damping coefficients from results of static wind-tunnel measurements. Author