73. A Realistic Approach to Structural Weight Estimation

Paper

Abstract

This paper is intended to show the steps which the weight engineer may take toward solving the problem of structural weight estimation of present day aircraft. An effort is made to approach the problem in a basic and realistic manner in order that the suggestions made may be of lasting value.
(a) The recent structural changes in piloted aircraft and missiles which have added to the cop1exity of weight estimation are viewed.
(b) The phases of weight estimation in preliminary design, from choice of propulsion and design objectives to advanced layout and their requirements in regard to detail and accuracy are analyzed.
(c) The basic methods of weight estimation statistical and design, are studied in their relation to the requirements of the phases of weight estimation. The optimum weight approach, which has been suggested as a method of weight estimation, is shown to be of limited value.
(d) Accuracy for either the statistical or design methods is shown to be achieved by structural breakdown on a functional basis. An example, using this approach, is given for 1anding gear weight estimation.
(e) The calculation of the standard deviation of statistical data is offered as a semi-qualitative basis for determining its accuracy.
(f) The failure of statistics is considered to be due mainly to the over-lapping functions of structure which prevent the correlation of structural weight with parameters relating to geometry, loads, and load factors. It is pointed out, for this reason that statistics based upon a multiplicity of parameters do not lead to greater accuracy.
(g) The concurrent use of statistical and design methods is considered to provide the quickest and best answer to structural weight estimation.
(h) Based upon the suggested approach to the problem, the future work for the weight and structure engineers is outlined.