Tradeoffs of Wing Weight and Lift/Drag in Design of Medium-Range Transport Aircraft

Wing design involves many compromises, but none more important than the one between aerodynamics, represented by lift-to-drag ratio, and structural weight. Multidisciplinary design optimization is used to compare the effect of configuration changes on wing weight and lift/drag ratio for 1) cantilever, 2) strut-braced, and 3) truss-braced wing aircraft for a medium-range, transonic, 162 passenger mission. Pseudo-Pareto fronts are generated to illustrate maximum lift/drag ratio compared to minimum wing weight. Lower lift/drag ratio aircraft have a shorter, more highly swept wing, with a change in taper at 75% semispan. Higher lft/drag ratio aircraft have much greater span and maximum chord at 33% semispan. To increase lift/drag ratio, both wing-weight and takeoff gross weight penalties must be paid. However, there are high lift/drag ratio designs with low wing-weight penalty that are clearly displayed by the pseudo-Pareto front. Fuel weight minima were found in the high lift/drag ratio and low wing-weight region of the pseudo-Pareto front for the truss-braced wing with both fuselage-mounted and wing-mounted engine configurations and for the cantilever configuration. An interesting pseudo-Pareto front was observed for the wing-mounted engine truss-braced wing configuration, where the pseudo-Pareto front almost became an asymptote to a lift/drag ratio of similar to 45. Also, one can look across all the configurations and compare attractive designs from each to search for an overall best aircraft design.