STEP BY STEP DESIGN OF AN AIRPLANE WING FOR MINIMUM WEIGHT.

Computer-aided minimum weight design for an aircraft using step-by-step approach has been tried in this paper. The size of stringers, their number and spacing, skin thickness, size of ribs, spar webs and flanges on tension and compression sides have been worked out separately with minimum weight of wing box between spars as an objective function. Optimization technique of M. J. Box has been used. Various buckling modes for stringers and skin on the compression side are taken as behavior constraints. Spar webs are designed to resist shear stresses due to design torque and shear force. The rib spacing is taken as a parameter to be optimized. Spar positions are assumed as given quantities by starting from the wing root, the wing sections are designed moving in the spanwise direction in steps of optimized rib spacing each time. The software in FORTRAN-IV language has been developed for this purpose and a typical example has been worked out.