936. Post-Design Analysis for Structural Weight Estimation

Paper

Abstract

This paper presents the methodology of post-design analysis (PDA) for determining structural weight penalties. The discussion is primarily oriented toward transport aircraft although the philosophy may be extended to other aircraft types. The derivation of equations for estimating weight penalties is avoided. Instead, a process is described for determining these penalties through the study of production aircraft in order that real-life penalties may be extrapolated to a particular advanced design situation.
The techniques involved in post-design analysis are presented by examining three basic considerations in the development and utilization of the process.
1. Selection and Classification of Weight Factors
The need for judicious planning in selecting the weight factors is discussed and some specific elements to consider are suggested. The discussion calls attention to the requirement for thoroughness and flexibility in order to ensure maximum benefit from the PDA results.
2. Determination of Weight Penalties
Methods for deriving weight penalties pertaining to the selected categories are explained and some consideration is given to the type of design data which should be collected along with these weights. Typical examples of actual penalties for certain structural members are presented.
3. Application of PDA
The principles involved in applying historical weight factors to a new design are discussed and a variety of examples to clarify the extrapolation process are given. Use of PDA data for cross-checking weight estimates derived through analytical techniques is also demonstrated.