839. A Theoretical Contribution to the Study of Weight Growth Factor in Aircraft Design

Paper

Abstract

Definitions of the aircraft growth factor as given by Driggs and Ballhaus and their theories are reported. With reference to the growth factor defined as total weight derivative in respect to fixed weight, the proposed scheme and some suggestions for the evaluations of the involved partial weight derivatives are briefly discussed taking into account the.. particular, nature of the preliminary design. A general approach to the subject seems to be useful. This approach may open out a way to completing the investigation of the promising subject. Hence the aim of the work is, to lay down basic theoretical grounds of the weight growth factor defined by Ballhaus as a starting point for the research on practical data. The more general approach to the subject shows that the weight growth factor is expressed by a formula, where there appear derivatives of weight components in terms of growth functions involved ,in the relevant design solution, and derivatives conditioning the, desired growth type. In certain cases such constraints derivatives shall satisfy compatibility relations. The difficulties of getting reliable expressions of weight derivatives are also examined from a general point of view. For a better understanding, of these concepts, Liebermann’s and Tilyou’s formulas related to the structure weight are adopted as an. Example. Furthermore, the derivatives of such formulas, lacking more reliable data, are obtained for the discussions of the size order of some terms.