A Low-Load Three-Component Force Balance for Measurements in a Low-Density Wind Tunnel

This paper describes a three-component force balance which has been developed for measurement of lift, drag and pitching moment acting on models in a low-density, hypervelocity wind tunnel. Although designed for a particular wind tunnel, the general arrangement and the principles involved should be applicable to similar situations. The balance is of the external type operating on the nulling principle. Nulling of each component is accomplished automatically through the use of closed loop control systems. Calibration data and sample wind tunnel measurements are presented which demonstrate that the balance is suitable for the intended application.