Analysis of various forced oscillation techniques for obtaining dynamic stability derivatives

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Virginia Polytechnic Institute and State University

Existing subsonic wind tunnel methods for obtaining dynamic stability derivatives for aircrafts at high angle of attack are described. From the general equations of motion of an aircraft in space, the perturbation equations of motion are derived for applying to a wind tunnel aircraft model. Data Reduction and test procedures for important dynamic tests are evolved systematically from the restrained perturbed equations of motion. Emphasis is given to the typical single degree of freedom apparatuses and associated data reduction for routine measurement of dynamic stability derivatives due to pitching, rolling and yawing of the model. The translational and snaking motion apparatuses from which the derivatives, α, β, and p, q, r are measured separately, are also presented. Finally, for the purpose of increasing the capabilities of the Virginia Tech dynamic test systems, a single degree of freedom forced oscillatory rig, which gives the exact sinusoidal displacement of the model and also adjustable to the existing curved and rolling flow facilities, is described with its data acquisition/reduction.