Towards cooperative high-fidelity aircraft MDO: comparison of Breguet and ODE evaluation of the cruise mission segment

Abstract

This report presents an organizational approach towards assembling and maintaining high-fidelity multi-disciplinary optimization (MDO) processes, in the environment of multiple institutes of the German Aerospace Center (DLR). Elements of the approach include both the technical conventions and the specialized software support. The approach is demonstrated on an early MDO process, that minimizes the mission fuel burn of an aeroelastic transport aircraft configuration, by modifying the wing planform, twist, and structural element thicknesses. Two optimizations are performed, one where the fuel burn is approximately evaluated through Breguet range equation, and the other where the ordinary differential equation (ODE) for the step-climb cruise is formally integrated. This is done in order to determine if the Breguet equation is still sufficient in face of high-fidelity aeroelastic simulations. The two optimized designs ended up practically the same, thus confirming the applicability of the Breguet equation, at least for the limited number of design parameters that were open for modification.