Decisions made during the concept and preliminary stages of an aircraft design have a major impact on the life-cycle cost of the project. Typically, up to the end of the concept and preliminary design stages, the actual spend is about 20% of the total cost but decisions taken during these two phases lock in 70% of the total cost. Poor choices early in the design process not only result in changes and modifications that are expensive to implement but may also delay entry into market and impact sales. Because of this, it is important that these decisions are correct and based on information that can be obtained rapidly and cheaply but is also as reliable and complete a possible.

At the concept and preliminary design stages, several different configurations may be considered as possible candidates to meet a given design specification. As more information becomes available, the range of configurations are reduced to a single choice. This Technical Memo gives an example of the use of rapid aerodynamic analysis tools at the concept and preliminary design stages applied, retrospectively, to three, markedly different historical candidate designs to similar design specifications.