A Parametric Analysis of Winglet Effects.

A two part study was undertaken. In the first part, winglet effects were examined on a variety of wing planforms. A nonplaner lifting surface computer program was used to calculate aerodynamic coefficients including lift, induced drag, wing pitching moment, and wing root bending moment coefficients. Typical cruise flight conditions were examined and the coefficients calculated for the wing alone were compared to those obtained for the wing with winglets installed. The calculations were then repeated as the wing aspect ratio, sweep angle, and dihedral angle were varied. Winglet size and orientation remained constant. The percentage induced drag reduction was found to be the greatest on the wing with the highest aspect ratio and wing sweep angle (27.5% for an aspect ratio 7, 45 degree swept wing). Percentage induced drag reduction increased slightly with increasing positive dihedral angle. The greatest incremental drag reduction occurred with the lowest aspect ratio, highest swept wing. The second study examined the effects of winglet cant angle on induced drag reduction. Winglet cant angle on two separate wings was varied from -3 degrees to +3 degrees in an attempt to find an optimum value. The model used in this analysis ignored viscous effects and indicated that positive cant angles (leading edge inboard yielded the greatest reductions in induced drag. (Author)