Derivative measurements and flutter tests on a model tapered wing

Abstract

The influence of various parameters, such as wing density and flexural stiffness on the critical speed of a tapered wing was investigated theoretically in R. & M. 1782 using certain fundamental aerodynamic derivative coefficients. The principal object of the present wind-tunnel tests was to provide an experimental confirmation of the theory. A semi-rigid model wing of the R. & M. 1782 type was constructed with two tapered wooden spars of cruciform cross section. Its flexural axis lay at 0.3 chord and its inertia axis at 0.4 chord behind the leading edge. Measurements were made by the forced oscillation method of the following aerodynamical derivatives for a range of values of the frequency parameter: (i) Flexural Damping, (ii) Torsional Damping, (iii) Torsional Stiffness. The still air torsional damping which included the damping due to the internal structure of the wing was also measured, and the virtual inertia effects due to the external air were estimated by two-dimensional strip theory as described in Ref. 3.