All aircraft engineers profess a belief in the importance of low structure weight. To implement this belief our efforts must be comprehensive and consistent and in the search for sound method it is important that we review, from time to time, familiar habits that are based on compromise. In the past the comparative merit of a particular aircraft structure has depended on a series of individual assessments, many of them semiarbitrary.These assessments have covered the whole field from the choice of the initial design load factors and the valuation of the working stresses right up to the ultimate maximum permitted all-up weight.

It cannot be denied that many of the prewar valuations were haphazard, usually conservative. This is demonstrated by the successful types of aircraft operating in service at weights considerably in excess of their original design estimate. Although this state of affairs proved highly fortunate it is a method that should not be perpetuated.