Tiltrotor multidisciplinary optimization

A short-haul transportation system using civil tiltrotor aircraft has recently been considered as a means for alleviation of airport congestion. Several technical sub-problems have been addressed separately. Multidisciplinary Design Optimization (MDO) techniques facilitate integration of these solutions. Published applications, however, did not employ a structured approach to problem decomposition down to the single data item, and existing integration frameworks were "hard-wired" for specific design problems.; In this dissertation, an integration method was developed which incorporates a four step decomposition-recomposition procedure. The method aids conversion of a given design problem in general terms into a specific infrastructure of available resources. Flexibility during the recomposition is provided by the representation of the information flow in matrix form. The matrix serves as a problem-dependent "program" for utilization of a set of problem-independent software tools. This structure permits free choice of optimization strategy (non-hierarchic, multi-level, Concurrent Subspace Optimization, CSSO, etc.), and allows restructuring of the process during its execution. The technique therefore enables exploration of specific design problems with a generic design framework.; A computational infrastructure employing this integration method was developed, and applied to a large-scale civil tiltrotor optimization problem with an emphasis on aeroelastic modeling. The objective function was the Productivity Index, PI, which served as an indicator of the aircraft's productivity-to-cost ratio. The impact of using a variable diameter rotor design (Variable Diameter Tiltrotor, VDTR), airframe aeroelastic tailoring, and active flutter suppression was explored using a non-hierarchic decomposition approach. Unfavorable results for VDTR aircraft were partially attributed to very limited available performance and weight data about this rotor system. The impact of aeroelastic and aeroservoelastic tailoring was outshadowed by the trade-off between rotor/airframe clearance and center of gravity location constraints. The single objective/non-hierarchic decomposition approach chosen contributed to this effect. A multilevel optimization scheme, or multi-objective optimization is suggested for future investigations.