Theoretical Investigation of Several Types of Single Degree of Freedom Flutter

The possibility of an undamped oscillation of an airfoil (or aerodynamic body) with a single degree of freedom in potential flow was first noted by Glauert in 1929 but has received relatively little attention until recently. These undamped oscillations might have a direct bearing on problems of both "dynamic stability" and "flutter" of airplanes. Because of the many configurations of airplane design now being considered and because of the wide operational ranges of speed and altitude, knowledge of these single degree phenomena becomes more significant. The present paper gives theoretically predicted effects of several primary parameters associated with single degree of freedom flutter. Specific problems dealt with are: (a) pitching oscillation of an unswept wing, oscillation of an aileron about its hinge axis, and bending oscillation of a swept wing in subsonic streams; (b) pitching of an unswept rectangular wing, pitching of a delta or triangular wing, and oscillations of an aileron about its hinge line, in supersonic streams. Results for one series of experiments which confirm the existence of single degree of freedom pitching flutter of an unswept wing at low speeds are included.