Optimal design of aircraft wing structures: a computer aided design method

Aircraft weight plays a significant role in its design because of its dominating effects on the vehicle overall performance. Statistical results suggested that the amplification impact factor of any weight-carrying component is about 4.525. That is, a 1.0 lb reduction in the structural weight translates to 4.525 lb reduction in gross aircraft takeoff weight. This paper focuses on the preliminary design of aircraft with optimized structural weight. The design concept is based on the optimal arrangement of the major force-carrying components within the aircraft. Further, it is shown that the optimum locations of the longitudinal wing spars results in, not only, minimum shear flows in spar webs and wing skins, but also, minimum axial stresses in the stringers of the wing spars. The net effect is an aircraft with minimum weight. The weight reduction is demonstrated by comparing the structural weight corresponding to the optimal arrangement with that corresponding to a randomly chosen arrangement. The computer aided design program developed in this research effort found the optimal locations of the two wing spars to be at 25% and 60% of the local chord length, respectively, after 136 iterations. Results indicate a 3.0% structural weight reduction (i.e., 13% takeoff) when only two spars are considered.