981. Fuselage Structure Weight Prediction

Paper

Abstract

A method of estimating the fuselage structure weight is developed, the weight of systems and furnishings being omitted. The weight of the shell structure is obtained by using the Mises-Hencky theory of yielding as a basis. The use of this criterion avoids certain difficulties encountered with analyses based upon instabi1ity but departs from the design process. Allowance is made for the effects of cutouts, longerons, the presence of a keel and minimum gauge design. The structure is considered to be subjected to bending, shear, torque and internal pressurization 1oading. Equations are developed which estimate the area of structural material in the shell at a series of stations or the fuselage. Integration then leads to the weight being obtained. The method is restricted to structures which are of the skin-stringer-shallow frame type of construction. The weight of component items, separate from the shell are considered using weight data to give empirical relationships. More numerical information is required to improve the resulting expressions and extend the range of components which can be included. The procedure can be developed further to cover other kinds of construction and include other special features such as fuel tanks, attachment of delta wings and bomb doors. A computer program has been written to perform the lengthy calculations that are involved. The paper represents a stage in the development of the analysis, which is devoted to investigating whether it is feasible to base a weght prediction method on a consideration of the behavior of the structural material. The work is not completed and further development is necessary to improve its scope and accuracy.