Drag prediction methods for preliminary design of an aircraft

Preliminary design or feasibility study is the first stage13; of an aircraft design during which the designer is investigating, may be an apparent market opportunity or a draft requirement for a military aircraft. At this stage, the designer is examining suitability of choosing alternate configurations for the desired purpose and hence for the results to be realistic, it is necessary that the drag forecast is accurate. It is important to note that pessimistic drag estimates at this early but crucial stage, may result finally in poor cost effectiveness, while an optimistic estimate may lead to frustration during detailed design and broken promises at the end. Thus, we see considerable merit in adopting a systematic and detailed approach for drag prediction even at the preliminary design stage and subjecting the results to careful scrutiny to ensure realism