Aircraft loads methodology for MDO

A methodology is presented for developing a complete set of aircraft loads to be used in the structural optimization of an aircraft wing during preliminary design. Using the software program ASTROS as the platform, a typical mid-size 100+ seat passenger aircraft was selected as the subject of the study. The methods are used in the design of a wing box optimally for minimum weight. This is accomplished while simultaneously evaluating the applied loads on the structure, including aerodynamic loads that account for the structural flexibility. The procedures make use of a finite element model of the complete aircraft, and have the additional benefit of producing a complete set of loads for the wing. The mass distributions (payload, fuel, etc.) are adjusted to produce the critical inertia for each load case. The loads are consistent (not envelope) and comprise flight, landing, ground handling, and gust conditions. The load levels of limit, ultimate and fatigue are all considered simultaneously for the optimization process, to which the appropriate design conditions are applied.