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
註釋 The results of this investigation indicated that a straight fuselage with circular cross sections, in general, had a more nearly linear variation of yawing-moment coefficient with angle of sideslip and a smaller variation in directional stability with angle of attack than the bent and straight fuselage models with elliptical cross sections and a bend fuselage with a circular cross section. Change 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 fuselage cross section more pronounced. The basic twin vertical tails, each having an area of 46.30 squre inches, did not provide directional stability throughout the angle of attack range for any of the models investigated; however, twin vertical tails of about 2 1/2 times this area provided a substantial improvement in the directional stability for all models. 