WIND-TUNNEL INVESTIGATION OF EFFECTS OF FUSELAGE CROSS-SECTIONAL SHAPE, FUSELAGE BEND, AND VERTICAL-TAIL SIZE ON DIRECTIONAL CHARACTERISTICS OF NONOVERLAP-TYPE HELICOPTER FUSELAGE MODELS WITHOUT ROTORS

摘要

A low-speed investigation was made in the Langley stability tunnel to determine the directional stability characteristics of tandem no overlap-type helicopter fuselages without rotors. The Investigation consisted of a study of both bent and straight fuselages having either circular or essentially elliptical cross sections and with two vertical-tail sizes.nThe results of this investigation indicate that a straight fuselage with circular cross sections, in general, had a more nearly linear vari¬ation of yawing-moment coefficient with angle of sideslip and a smaller variation of directional stability with angle of attack than the bent and straight fuselage models with elliptical cross sections and a bent fuse-lage with a circular cross section. Changing the cross-sectional shape from elliptical to circular resulted in a more nearly linear variation of yawing-moment coefficient with angle of sideslip and a smaller variation of directional stability with angle of attack. Adding the bend in the fuselage, in general, made the adverse effects of flattening the fuse¬lage cross section more pronounced. The basic twin vertical tails/ each having an area of 46.30 square inches, did not provide directional sta¬bility throughout the. Angle-of-attack range for any of the models investi¬gated; however, twin vertical tails of about2 1/4 times this area provided a substantial improvement in the directional stability for all model.