Multidisciplinary design optimization of a transonic commercial transport with a strut-braced wing

This paper details the multidisciplinary design optimization (MDO) of a strut-braced wing aircraft and its benefits relative to the cantilever wing configuration. The multidisciplinary design team is subdivided into aerodynamics, structures, aeroelasticity and synthesis of the various disciplines. The aerodynamic analysis consists of simple models for induced drag, wave drag, parasite drag and interference drag. The interference drag model is based on detailed computational fluid dynamics (CFD) analyses of various wing-strut intersection flows. The wing structural weight is partially calculated using a newly developed wing bending material weight routine that accounts for the special nature of strut-braced wings. The remaining components of the aircraft weight are calculated using a combination of NASA's Flight Optimization System (FLOPS) and Lockheed Martin Aeronautical System formulas. The strut-braced wing and cantilever wing configurations are optimized using Design Optimization Tools (DOT). Offline NASTRAN aerolasticity analysis preliminary results indicate that the flutter speed is higher than the design requirement.