Fundamentals of Conceptual Design Optimization of Subsonic Transport Aircraft

摘要

Various merit functions and feasible design program structures are discussed and program elements common to most design exercises were analyzed. Criteria for optimum cruise conditions are presented for aircraft with or without Mach number dependent drag polars and arbitrary propulsion systems. Constrained and unconstrained optima for design cruise speed and altitude, engine thrust, wing loading, aspect ratio and lift coefficient are presented in the form of generalized analytical expressions. Different criteria were found when engines were sized for optimum cruising flight or for specified low speed performance. A generalized cruise performance analysis is presented for modern turbofan and propeller aircraft, resulting in new criteria for optimum flight conditions. A detailed account of the aircraft mass breakdown sensitivity to parametric variations, derivations for the payload fraction, and partial (constrained) and global optima were derived. Some opportunities for improvements and extended applications to non-conventional and advanced designs are discussed briefly.