Modeling and Analysis of Aeroelastic Instabilities in a Flexible Full Aircraft Using Quasi-Coordinate Formulation and Minimum State Aerodynamic Model

Document Type : Research Article

Authors

1 Faculty of Aerospace Engineering, Malek-Ashtar University of Technology

2 Aerospace Facutly,, K N Toosi University of Technology

Abstract

An advanced analytical model of a fully flexible aircraft is developed to investigate aeroelastic instabilities, with a focus on the coupled interactions between unsteady aerodynamics and nonlinear flight dynamics. The formulation employs a quasi-coordinate Lagrangian approach, where the aircraft is modeled as a flexible multibody system comprising a deformable fuselage, wings, and empennage, each discretized using Euler-Bernoulli beam theory with modal reduction. Unsteady aerodynamic loads on lifting surfaces are simulated via the Minimum State Variable (MSV) method, which provides a computationally efficient state-space representation while minimizing the number of required states. The model captures key aeroelastic phenomena, including symmetric/antisymmetric wing flutter, body-freedom flutter (coupling short-period pitch dynamics and roll dynamics with wing bending). Additionally, the influence of rigid-body flight dynamics—such as plunge, pitch, roll, and their interactions with structural modes—is rigorously examined. Parametric studies evaluate the sensitivity of flutter boundaries to variations in aircraft mass, pitch/roll inertia, and flight conditions. The results demonstrate that inertial coupling can either stabilize or destabilize certain modes, depending on the configuration. This integrated framework enables comprehensive aeroelastic-flight dynamic analysis, supporting preliminary design trade-offs and multidisciplinary optimization of next-generation aircraft.

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Amirkabir Journal of Mechanical Engineering
Volume 57, Issue 3
June 2025
Pages 283-302

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