NACA-ARR-3F28

Abstract

<strong>INTRODUCTION</strong> <br>In calculating the lateral stability of an airplane, difficulty is often experienced in estimating values of the stability derivative c_nr, the rate of change of yawing. moment coefficient with yawing angular velocity. Although theoretical methods for obtaining the value of c_nr cdontrinuted by the vertical tail and the wing are given in references 1, 2, and 3, little recent experimental work has been done to determine values of this derivative. In order to provide experimental data on the contributions of the wing, the fuselage, and the vertical tail to c_nr, some measurements for a midwing airplane model have been made in the NACA free-flight tunnel. Additional measurements were made for a rectangular wing of high-lift section in order to extend the lift coefficients to the high values encountered by full-scale airplanes. The results are presented in the present report. <br>A free-oscillation method similar to that described in reference 4 was used. The values of c_nr were directly determined from the dawping of free-yawing oscillations, which were obtained with the models mounted on a strut that permitted freedom only in yaw.