NACA-RM-L51A10

Abstract

INTRODUCTION <br>Considerable interest has been shown in tailless airplanes because of the low drag advantages of such a design. With the advent of the use of sweepback in high-speed airplanes, this interest has heightened because a swept wing offers. an effective tail length for the placement of longitudinal and directional control devices. Furthermore, removing the tail surfaces from the wake region of the wing eliminates certain adverse effects of compressibility in high-speed airplanes. A completely tailless design, however, has certain disadvantages - one being the lack of directional stability. The addition of vertical fins for the purpose of increasing the direction stability results in an arrangement which will be referred to in the present paper as a semi tailless design. <br>The calculation of the dynamic stability of most semi tailless airplanes has involved some. degree of uncertainty because of the unusually short tail lengths and large tail heights of such designs. In order to establish the validity of the application of the usual methods for predicting the stability derivatives of such airplanes and to establish a basis for estimating the effects of fin area and location on these derivatives, a representative model of a semi tailless airplane was tested in straight, yawing, and rolling flow in the Langley stability tunnel. This investigation was undertaken as part of an extensive program being carried out in the Langley stability tunnel to establish the effects of systematic changes in configuration upon the low-speed static and rotary stability characteristics of high-speed airplane designs.