Evaluation of the Impacts of Objective Function Definition in Aircraft Conceptual Design

This paper presents a successive derivation of basic equations in order to enlighten the implicit relationships between some of the most common objective functions employed in aircraft conceptual design. Correlation between financial and technical figures of merit relies on some important assumptions that may breakdown under certain circumstances, and therefore it is ill-advised to look for financially optimal designs using technical objective functions. As shown in the Results section, relationships between technical-only figures of merit hold and their behavior is even mathematically predictable. On the other hand, technical-financial relationships depend on market variables (price and market forecast, mainly) that can be captured only by proper market and financial models. In the Results section it is shown how optimization using technical-only objective functions overlooks important economical trades and thereby emphasizes the need for a proper modeling of such disciplines within the multidisciplinary analysis and optimization framework.