Exploring Aeroelastic Stability and Design Principles in Aircraft Wings with Distributed Propulsion Systems

Next-generation aircraft designs must balance the increasing demand for mobility with the need to reduce emissions. Large, open, electrically driven, and distributed propeller systems have the potential to become a key concept for efficient modern aircraft. This research focuses on the aeroelastic stability analysis and evaluation of the Distributed Electric Propulsion (DEP) concept, addressing the key challenges in developing and analyzing modern aircraft designs. A primary contribution of this work is the development of a frequency-domain analysis tool (SDBox) for robust and efficient aeroelastic stability assessment. SDBox enhances current methods by modeling the aeroelastic dynamics of wings and propellers, focusing on wing flutter and propeller whirl flutter. It allows the creation of wing models that can accommodate multiple propellers, considering structural dynamic coupling effects. SDBox has been verified against established benchmark models for both wings and propellers, and by applying mid-fidelity nonlinear time-domain simulations using the open-source tools MBDyn and DUST. The results show excellent greement in predicting flutter speeds and mechanisms for various test cases, confirming the SDBox’s reliability and accuracy. The research initially focuses on whirl flutter prediction, introducing workflows to determine unsteady aerodynamic derivatives. These derivatives lead to more conservative flutter onset predictions compared to traditional analytical derivatives. Next, the study explores the coupling effects between wing and propellers in DEP configurations, along with the analysis of DEP systems with different numbers of propellers. The primary aeroelastic flutter mechanism identified is wing flutter, while whirl flutter is unlikely and may only occur in failure scenarios. The coupling effects between wings and propellers stabilize the system, especially when propellers are positioned ahead of the elastic axis near the wingtip. Destabilizing factors include propeller aerodynamics and lower pylon stiffnesses. Aerodynamic interactions between propellers and wings destabilize the system due to locally increasing dynamic pressure, particularly in DEP configurations. Based on these investigations, several design guidelines were derived. From an aeroelastic perspective, wingtip-mounted propellers are recommended for their stability and aerodynamic benefits. Pylon flexibility should be carefully managed to avoid interference with the wing’s natural frequencies. The number of propellers in a DEP system presents a trade-off: fewer propellers reduce wing flutter onset, but larger and heavier propellers may increase susceptibility to whirl flutter. This study highlights the advantages of frequency-domain methods for fast and reliable preliminary stability analysis. However, capturing detailed effects such as coupled wing–propeller aerodynamic interactions currently requires time-domain simulations, as suitable linearized frequency-domain or state-space representations for such coupled systems are currently not available. In addition, it provides practical tools for the conceptual design of electric-driven novel aircraft. Despite limitations like the exclusion of flexible blades or hover conditions, the findings provide a solid foundation for future research.