Conceptual design studies of a strut-braced wing transonic transport

Recent transonic airliner designs have generally converged upon a common ca ntilever low-wing configuration. It is unlikely that further large strides in performance are possible without a significant departure from the presen t design paradigm. One such alternative configuration is the strut-braced w ing (SBW), which uses a strut for wing-bending load alleviation, allowing i ncreased aspect ratio and reduced vying thickness to increase the lift to d rag ratio. The thinner wing has less transonic wave drag, permitting the wi ng to unsweep for increased areas of natural laminar how and further struct ural weight savings. High aerodynamic efficiency translates into smaller, q uieter, less expensive engines and less pollution. A multidisciplinary desi gn optimization (MDO) approach is essential to realize the full potential o f this synergistic configuration caused by the strong interdependence of st ructures, aerodynamics, and propulsion, NASA defined a need for a 325-passe nger transport capable of flying 7500 n miles at Mach 0.85 for a 2010 servi ce entry date. Lockheed Martin Aeronautical Systems (LMAS), as Virginia Pol ytechnic Institute and State University's (Virginia Tech) industry partner placed great emphasis on realistic constraints, projected technology levels , manufacturing, and certification issues. Numerous design challenges speci fic to the strut-braced wing became apparent during the study. Modification s were made to the Virginia Tech formulation to reflect these concerns, thu s contributing realism to the MDO results. The SEW configuration is lighter , burns less fuel, requires smaller engines and costs less than an equivale nt cantilever wing aircraft.