NACA-RM-L53K09

Abstract

INTRODUCTION <br>Several methods are available for estimating stability derivatives of airplanes (for example, see ref. I); however, these methods do not account well for the effect of unusual airplane geometry on the stability derivatives. This deficiency often results in a poor prediction of the dynamic stability characteristics of the airplane. A similar situation appears to exist for the high-speed fighter airplane employed in this investigation since the damping of the lateral oscillation of this airplane could not be calculated in one investigation with the accuracy desired by using estimated stability derivatives (ref. 2) although better agreement was obtained in another investigation (ref. 3). <br>The purpose of the present investigation, which was made in the Langley stability tunnel, was to obtain the low-speed lateral static and rotary stability derivatives of a 1/12-scale model of a high-speed fighter airplane with unswept wings and to compare the experimental stability derivatives with the derivatives estimated by current methods for the wing-fuselage combination, the vertical- and horizontal-tail combination, and the complete model. In addition, since a large difference existed between the static lateral stability derivatives presented herein and the unpublished derivatives obtained in previous tests of a sting-supported model, a few tests were made to determine the effects on the static lateral stability derivatives of a fuselage modification similar to that necessitated for sting-mounting. This modification consisted of an increase in the cross-sectional sea Of the rear portion of the fuselage under the vertical tail.