Differential Evolution and DATCOM Implementation to Enhance Airframe Design Longitudinal Stability

Designing an aircraft can indeed be a complex problem, as the aircraft design process involves numerous interrelated variables. On the other hand, it is also crucial to consider the parameters of aircraft stability to ensure that the flying qualities are suitable for the various phases of the mission flight. This paper introduces a novel approach to optimize airframe design processes by utilizing metaheuristic methods to determine the preliminary airframe design that meets the criteria of longitudinal dynamic stability in accordance with regulations, while also considering the weight of the airframe. Candidate aircraft geometries will be generated using Differential Evolution (DE), a powerful stochastic real-parameter optimization algorithm, integrated with DATCOM to determine the aerodynamic derivative parameters for each design population. Additionally, this method involves the implementation of a Fuzzy Inference System (FIS) to map the result of phugoid damping, short period damping, and airframe weight to the output of quality value. This paper demonstrates that the introduced optimization method, by producing 1,554 and 1,780 generations with 3,300 population for each generation, can generate the most optimal design offspring with a level 1 flight quality (referring to MIL-F-8785C) for both commuter and transport aircraft cases. The result shows quality value improvement 70.4136 and 69.3328 (compared to the first generation) for commuter and transport aircraft cases respectively with 4 seconds of mean evaluation time. Based on the obtained results, it can be concluded that the developed optimization method can serve as a new alternative approach to determining the preliminary design of an airframe.

I. Introduction

Over time, significant progress has been made in the design of airframes to ensure their efficiency, safety, and comfort. Among the critical aspects of airframe design, stability holds great importance. Specifically, achieving longitudinal stability is a crucial objective in aircraft design. Longitudinal stability refers to an aircraft’s capability to maintain its pitch attitude and equilibrium during flight. It plays a vital role in ensuring safe maneuvering, stability in gusty conditions, and effective control of the aircraft. However, in the early days, airframe designer relies on iterative testing methods to achieve acceptable levels of stability based on regulations. Nevertheless, these approaches can be time-consuming.