Integrating Manufacturing Cost and Structural Requirements in a Systems Engineering Approach to Aircraft Design

Abstract

The paper addresses the issue of linking cost into the structural design process in order to meet customer requirement. Rather than only looking at manufacturing cost, Direct Operating Cost (DOC) is also considered in terms of the impact of weight on fuel burn, in addition to the acquisition cost to be born by the operator. Ultimately, there is a trade-off between driving design according to minimal weight and driving it according to reduced manufacturing cost. The analysis of cost is facilitated with a Genetic-Causal cost modelling methodology and the structural analysis is driven by numerical expressions of appropriate failure modes that utilize ESDU reference data. However, a key contribution of the paper is to investigate the modelling of uncertainty and to perform a sensitivity analysis to investigate the robustness of the optimization methodology. Stochastic distributions are used to characterize manufacturing cost distributions and Monte Carlo analysis is performed in modelling the impact of uncertainty on the cost modelling. The results are then used in a sensitivity analysis that incorporates the optimization methodology. In addition to investigating manufacturing cost variance, the sensitivity of the optimization to fuel burn cost and structural loading are also investigated. It is found that the consideration of manufacturing cost does make an impact and results in a different optimal design configuration from that delivered by the minimal weight method. However, it was shown that at lower applied loads there is a threshold fuel burn cost at which the optimization process wishes to reduce weight, this threshold decreasing with increasing load. The new optimal solution results in lower DOC with a predicted saving of 660$/m