Aircraft-Pilot-Coupling: Parametric Study Using Multibody Dynamics Modeling of Pilot Biodynamics, Pilot Seat, and Inceptor

Abstract Aircraft?Pilot?Coupling (APC) refers to undesirable oscillations that emerge from dynamic interactions between the pilot, flight control system, and flexible aircraft structure. These instabilities can compromise safety and handling qualities in modern lightweight aircraft. This study advances APC prediction capability by introducing a novel parameterizable pilot biodynamics model formulated within a unified physics-based framework. The model is a lumped?discrete hybrid representation of torso and arm dynamics with coupled mass, stiffness, and damping elements, producing responses that are physiologically interpretable and enabling systematic variation of pilot properties. Pilot model transfer functions are optimized against experimental transmissibility data to obtain joint stiffnesses and damping coefficients using three optimization techniques in MATLAB: fminsearch, genetic algorithms, and Pareto analysis. The biodynamics model is then integrated into both a high-order aeroelastic aircraft model and a low-order representation to form an Aircraft?Pilot?System (APS) for assessing APC susceptibility. Parametric studies on the APS vary pilot joint stiffness, damping, mass, and side-stick inceptor inclination angle, revealing consistent qualitative trends across model fidelities. Potential APC bandwidths are identified using the low-order aircraft model. Within these bandwidths, a new stability assessment framework measures how close the Nyquist response of the low-order APS comes to the critical -1 point, quantified using the Minimum Return Difference (MRD) and approach angle. This provides APC stability margins even when classical gain/phase metrics are undefined. These contributions establish a physiologically grounded pilot model and practical tools for robust APC analysis in future aircraft design.