Aircraft Design explores fixed winged aircraft design at the conceptual phase of a project. Designing an aircraft is a complex multifaceted process embracing many technical challenges in a multidisciplinary environment. By definition, the topic requires intelligent use of aerodynamic knowledge to configure aircraft geometry suited specifically to the customer's demands. It involves estimating aircraft weight and drag and computing the available thrust from the engine. The methodology shown here includes formal sizing of the aircraft, engine matching, and substantiating performance to comply with the customer's demands and government regulatory standards. Associated topics include safety issues, environmental issues, material choice, structural layout, understanding flight deck, avionics, and systems (for both civilian and military aircraft). Cost estimation and manufacturing considerations are also discussed. The chapters are arranged to optimize understanding of industrial approaches to aircraft design methodology. Example exercises from the author's industrial experience dealing with a typical aircraft design are included.

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The cost impact of aerodynamic tolerances on the wetted surface of an engine nacelle is considered. Manufacturing tolerance data were obtained from Bombardier Aerospace Shorts, Belfast, while the corresponding costs were calculated according to various recurring elements such as basic and overtime labour, rework, concessions, redeployment, etc., along with amortized non-recurrent costs due to jigs and tooling, machinery, etc. The cost—tolerance relations were modelled statistically so that the influence of tolerance change could be ascertained. It was found that relatively small tolerance relaxations resulted in significantly reduced costs of production but that there was a large variation in the sensitivity, at current levels. The resultant drag penalty was also predicted in conjunction with the cost—tolerance estimation to show that the operational cost effectiveness of the nacelle was increased by 0.33 per cent.

An integrated multidisciplinary approach to aerospace design is presented as a means of improving the present state of the art towards a more effective concurrent methodology empowered by costing tools. Only the most influential drivers are identified and structured into a preliminary costing framework that supports decision making upfront in the design process. The research addressed a range of fundamental aerospace issues in developing key Cost Estimating Relations (CERs), conceming concept design, detailed design, and fitness for purpose. The resulting methodology and costing tools facilitate the sharing and utilization of information in order to best satisfy the ultimate design objective, rather than being limited to only one parameter driving the process at any one or more stages. Relevant data and knowledge were collected from industry, and a commercial Computational Fluid Dynamics (CFD) code was utilized along with a program to predict aircraft Direct Operating Cost (DOC). Notably, it was found that general complexity and both recurring and non-recurring costs were reduced at the conceptual stage; tolerances and design detail were better allocated to reduce non-conformities and recurring costs; and performance requirements were assessed in the light of aircraft DOC in order to improve ultimate competitiveness. However, most significantly, it is shown that a practical concurrent approach can be enabled with supportive costing tools that improve the designers' ability to make more holistic decisions upfront in the design process.

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