Wind-tunnel flutter tests on a delta wing with an all-moving tip control surface

Abstract

Wind-tunnel tests on a half-span model delta wing, fitted with an all-moving tip control surface, are described. The model, which is flexible, has a leading-edge sweepback of 45 deg; and the control surface, which is rigid, has an area 9.3 per cent of the gross wing area. The control surface is hinged at 47.4 per cent of its root chord. Provision is made for varying the circuit stiffness and the position of the centre of gravity of the control surface and its pitching moment of inertia. The tests show that certain combinations of control-surface inertia and circuit stiffness produce very low flutter speeds. The effect of reducing the control-surface area by cropping the tip is examined, and in general is found to be beneficial. It is shown that the most favourable conditions for avoiding low flutter speeds exist when the control surface centre of gravity is well forward of the hinge-line and the control-surface natural frequency is well removed from the natural frequency of the wing in its fundamental flexural mode.