794. Quickie Weight Estimating Equations – Turning Their Inherent Weakness Into an Advantage

Paper

Abstract

A ‘quickie’ wing weight equation of unknown origin is employed to arrive at some astonishing conclusions. This leads into a discussion of a North American Rockwell (NR) wing weight study; a study consisting of 81 designs, optimized with respect to geometric and construction variables and constrained with respect to several manufacturing requirements. The investigation leads to more surprising consequences.
General content is directed toward spotlighting little-known facts not usually pointed out in a two semester course in statistics and, for that reason, not implemented in practice. One of these facts concerns extrapolation when more than one independent variable is considered explicitly in a weight prediction equation. An extrapolative condition may exist without being immediately recognized. In fact, each independent variable may lie well within the limits defined by source data when each variable is examined separately, yet extrapolation may exist de facto. Extrapolation voids conventional accuracy determination and makes prediction extremely hazardous. This paper attempts to point out the dangers and, in a positive vein, to improve reliability.