NACA-RM-A7H29

Abstract

INTRODUCTION <br>Various methods have been devised for relieving the excessive control forces experienced in airplanes when maneuvering at high speeds. These methods usually incorporate some form of control-surface balance the main function of which is to reduce the aerodynamic hinge-moment coefficient and still give a desirable rate of change of hinge-moment coefficient with angle of attack. Many of such balancing devices are subject to the adverse effects of compressibility. These effects can be most accurately evaluated by testing the actual control surface. <br>A full-scale semispan horizontal tail form a fighter airplane was tested in the Ames 16-foot high-speed wind tunnel to investigate the effectiveness of shielded-and unshielded-horn and overhang balances and to evaluate their effects on the floating characteristics of the elevator at high subsonic Mach numbers. <br>Lift, drag, pitching moments, and elevator hinge moments were measured. Critical Mach numbers were determined at two stations from measurements of the chordwise pressure distribution <br>Large-amplitude vibrations and the resultant structural deterioration limited the maximum Mach number to 0.75 for most of the tests. For tests with a reduced semispan, however, the maximum Mach number was extended to 0.825. The Reynolds number range extended from 6,400,000 to 16,900,000 as shown in figure 1.