Contributions to aircraft preliminary design and optimization

Abstract

This work covers two related fields a) aircraft preliminary design and optimization, including aircraft cabin design and optimization and b) the optimization of engineering working processes in cabin design and cabin refurbishing. For a) existing equations or methods for aircraft preliminary sizing and conceptual design are adjusted and new equations or methods are introduced (e.g. equation for Oswald factor estimation, method for winglets efficiency estimation, method for estimating cabin length, method for estimating overhead stowage volume). Equations were combined to an Aircraft Design methodology. The methodology was implemented into Microsoft Excel to create a tool called OPerA – Optimization in Preliminary Aircraft Design. Optimization was initially done with a high-level commercial optimization software, Optimus. A technique called Differential Evolution was selected to be programmed in Visual Basic for Applications (VBA) and integrated directly into OPerA. Four objective functions are selected: the classical minimizing of Direct Operating Costs (DOC) represented by equivalent ton-miles costs, minimizing fuel mass, minimizing maximum take-off mass and maximizing of a composed objective function DOC+AV consisting of a weighting of DOC and Added Values which are selected parameters responsible for additional revenues for an airline. For b) three alternatives are proposed to increase efficiency of cabin design activities: i) a partitioning algorithm delivers the sequence that minimizes information feedback, ii) the analysis of the eigenstructure of the matrix underlines those processes with the greatest influence on the engineering system, and iii) a cross impact analysis identifies groups of processes belonging to five spheres: reactive, dynamic, impulsive, low impact and neutral. The selected reference aircraft for optimization is the Airbus A320-200. Three additional versions of the aircraft are investigated: a version with braced wings, a version with natural laminar flow and a version having both innovations at the same time. A number of 24 combinations of aircraft and cabin parameters, as well as requirements are tested for each objective function and each aircraft version. Varying aircraft and cabin parameters and adding the two innovations braced wings and natural laminar flow delivered these improvements: reduces DOC by about 16 %, maximum take-off mass by 24 %, fuel mass by 50 % and increases DOC+AV by 48 %. The tool provided is an efficient Aircraft Design tool, producing traceable optimizations in Preliminary Aircraft Design. It can be used in teaching as well as in the research of conventional and innovative configurations. Optimizing process chains for cabin redesign activities is not only beneficial, but also helps demonstrating required design and certification capabilities to aeronautical authorities.