68. Weight Growth of Experimental Jet Fighter Airplanes

Paper

Abstract

Weight growth is a chronic ailment that ha8 plagued the industry for years with experimental airplanes being affected more than any other type. Industry experience usually follows about the same pattern beginning with a weight estimate that covers all known items, followed by an inflationary weight growth spiral caused by the unforeseen items and finally tapering off as the airplane nears completion. For some airplanes the weight growth is small and has a negligible effect; for others it is large and quite serious. While this condition is generally recognized, little information has been available as to the average extent and nature of this tendency.
The purpose of this paper is twofold: (1) to show the results of a survey which was made to measure the aircraft industry’s weight growth experience with experimental jet fighter airplanes; (2) to stimulate an interest in the application of statistical methods to the weight engineering field.
The term ‘weight growth’ is used to define the increment of weight between the specification combat gross weight and the actual combat gross weight at first flight. The somewhat more familiar term ‘overweight’ is roughly synonymous with weight growth but is not used since the implication to most engineers is that of a ‘lousy’ design. Although it is possible that some airplanes may be heavier than estimated because of a poor design, weight increases also result from the addition of certain improvement features.