Measurements of Control-Surface Oscillatory Derivatives on a Sweptback, Tapered Model Wing in two Transonic Tunnels

Results of measurements of control-surface oscillatory derivatives on a sweptback, tapered half-model of a lifting surface of aspect ratio 2 are presented. The measurements were obtained during the development of a derivative rig which measures normal force, pitching moment, wing bending moment and hinge moment due to control surface oscillation. They were made in the 18 in. × 14 in. (0.46 m × 0.36 m) N.P.L. Teddington tunnel and the 3 ft (0.91 m) R.A.E. Bedford tunnel, the rig being found to operate satisfactorily in both situations. Mach number was varied from 0.4 to 1.0 and stagnation pressure from 0.5 to 2.3 bar. With this combination of Mach number and stagnation pressure, Reynolds number varied from 1 to 6 millions based on mean chord. The effects of varying the control-surface deflection amplitude from 0.4 to 1.6 degrees and the oscillation frequency from 20 to 70 Hz were examined. The effect of tunnel interference was assessed by measurements in ventilated and closed wall working sections in each tunnel. Most of the tesfs were carried out with transition bands on the model, but a few tests were made with the bands removed. The measured derivatives are compared with those obtained by theoretical methods of calculation.