The initial phase of the design of an aircraft is usually thought of as being glamorous and exciting since it is the part of the total exercise which determines those characteristics of the aircraft for all to see. The artistically inclined can let his imagination run away with him as he visualises an aesthetically pleasing concept. The inventor has more than ample scope to propose layout innovations which supposedly confer some advantages, often of ill defined value. Tradition has it that the renowned designers of the past with their vast experience, aesthetic flair and innovatory streak would blend all the numerous possibilities into a satisfying if not always entirely satisfactory, project.

Of course such an idea is a gross over-simplification of the project design process which, as in any design activity, must consist of many configuration iterations before an acceptable solution is achieved. The large number of variables which have to be considered coupled with the extremely demanding performance and safety requirements of any advanced aeronautical system imply such complexity that every aid available must be employed.