NACA-TN-3135

Abstract

Tests were made on three circular-arc-fuselage and nine unswept-vertical-tail models in order to investigate interference effects between fuselages and vertical tails in sideslip. The mutual interference effects, and thus the effectiveness of the vertical tail in producing directional stability, appear to be mainly dependent upon the ratio of the vertical-tail span to the fuselage diameter at the position of the vertical tail and upon the vertical-tail aspect ratio and to be relatively independent of the fuselage fineness ratio. The increase in vertical tail effectiveness is largest for small values of the ratio of the vertical-tail span to the fuselage diameter and decreases as this ratio increases; in general, the effectiveness increases with increase in the vertical-tail aspect ratio. The magnitude of the induced loading on the fuselage is comparable to the magnitude of the corresponding induced loading on the vertical tail. The interference effects of the vertical tail and the fuselage on one another may result in a tail effectiveness of the tail-fuselage combination which is different from that of the tail alone, the difference being an increase of 0 to 100 percent of the tail-alone effectiveness for the configurations tested. The vertical center-of-pressure calculations indicate that, as the span-to-diameter ratio decreases, the fuselage loading becomes proportionally more important and the center of pressure moves downward toward the tail root or the fuselage center line. The longitudinal center of pressure is in the vicinity of the tail quarter-chord line.