Ministry of Supply

This paper gives the results of an investigation into the effects of wing torsion in a ternary-type spring-tab flutter. The results presented are for a series of calculations on an idealised system having degrees of freedom in wing pitch, rotation of the control surface and rotation of the tab; the pitching degree of freedom is spring restrained and is intended to represent wing torsion. The tab is restrained as a trim tab or pure aerodynamic servo tab, but the results are expected to apply qualitatively to a spring tab. A comparison is made between these results and those of earlier investigations into a similar problem by Wittmeyer-and Wittmeyer and Templeton-, where the main surface mode considered was one of vertical translation to represent wing bending. From this previous work criteria were suggested for the prevention of this type of flutter, and in an analogous manner criteria are now tentatively proposed for prevention of wing torsion-aileron-tab flutter. 1. Introduction.-Past investigations of spring-tab flutter have considered in the main a ternary-type flutter involving one wing mode, rotation of the aileron and rotation of the tab]. The wing mode usually considered was one of wing bending represented by vertical translation under a spring restraint. Little investigation of a general character has been made into the problem of spring-tab flutter where the wing mode involved is one of torsion. This paper gives the results of an investigation into this problem where pitching of the wing replaces vertical translation. The pitching degree of freedom is spring restrained and is intended to represent wing torsion. The tab is restrained as a trim tab (the representation being equally valid for a pure aerodynamic servo tab), but the results can be expected to apply qualitatively to a spring tab also.