A Methodology for Integrated Cost Engineered Systems within Aerospace

The paper is concerned with the modelling of engineering driven costs for integration into a systems engineering approach. The methodology presents a Genetic Causal cost modelling concept that isolates product families and their causal relationship to engineering design parameters. This includes the initial modelling for each stage of assembly build for the fabrication and assembly costs, where material costs are assumed to be calculated directly as a function of the weight and unit cost for each type. The acquisition cost is then considered through the modelling of the recurring unit cost and the non-recurring design cost of larger airframe assemblies. Finally, the through-life cost impact is investigated using a simple model for the relationship between unit cost and operational cost for a range of 11 nacelles. The operational cost is modelled as fuel burn as a function of weight and allows the comparison between predominately metal or composites designs. In general, the systems engineering approach is facilitated by focusing on the modelling of engineering requirements relative to cost, in the light of customer requirements and derived systems requirements. However, ultimately the objective function should be profit. The work does not consider design modifications or maintenance, and the cost modeling does not explicitly include the associated costs of reworking etc, jigs and tooling etc, and overheads. A number of industrial case studies are presented that focus on the realised reduction in unit cost by optimizing part count. The results highlight the opportunity for the early optimization of design by using causal parametric cost drivers to guide the conceptual layout design process for structural assemblies, typical to the Design for Manufacture and Assembly approach. The main body of work is concerned with the Genetic Causal cost modelling and concludes with a suggested approach to the integration of this modelling technology into a systems engineering design model. The main contribution of paper is in the modelling of cost as a function of conceptual design parameters, and in the linking of that to customer requirements through acquisition cost and fuel burn (weight) through direct operating cost.

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