Design Considerations

In the chapter overview (see Section 17.1), it is pointed out that the public-domain literature is replete with Design for… considerations, including Design for Manu­facture, Design for Assembly, Design for Quality, Design for R&M, DFSS, Design for Recycling, Design for Antipollution, Design for Life Cycle, and Design for Cost, all heading toward a generic Design for X. These considerations led to the appear­ance of new considerations (sixteen listed in this section), with more from the aca­demic circle. The fresh insights of academia may shed new light but may not be amenable to industrial implementation. Only recently have the drive for Design for R&M and DFSS become part of industrial practices and they are still evolving. The industry has yet to address decisively the other costs of LCC (e. g., training and evaluation, logistic supports, and special equipment) at the conceptual design stages of civil aircraft design in order to reduce the ownership costs of operators. Of the various Design for… considerations, only a third are applicable to DFM/A consid­erations. A robust cost model would support trade-off studies to arrive at the best value.

The new challenge for the industry is to examine all aspects of ownership costs at the conceptual design stages of a project. Performance evaluations based on set­ting individual goals of cost minimization at each design consideration may not result in the global minimum when strong interaction within the multidisciplines exists. In an IPPD design environment, the combined effort of various disciplines provides a better approach to make a product right the first time at a lower cost. The holistic approach suggests the role of cost modeling as a tool to address all con­siderations simultaneously; this facilitates performance-versus-cost trade-off studies in order to arrive at the most satisfying product line with the widest customer cov­erage. With this approach, the author introduces the term design for customer as a measuring index for “value for the money” defined in Section 17.9.

The sixteen design considerations appearing as Design for… terms are broadly classified in four categories with brief descriptions. They must provide designers with complete product information in the conceptual design stages based on their expertise and technology level. The purpose of this strategy is to make a product

yield the specific benefits of the lowest LCC (or in civil aviation applications DOC)

in a unified manner, leading to the Design for Customer.