On the influence of airframe flexibility on rotorcraft pilot couplings

Abstract

Abstract. A set of numerical simulations of the interactional dynamics of the pilot-rotorcraft system is performed. The aim of the numerical analysis is to evaluate the stability of the closed-loop system in hovering conditions, focusing on the influence of the first airframe flexible mode, the one with the most participation in relative motion between the main rotor and the pilot’s seat and closest in frequency to pilot-vehicle interaction. Two approaches are employed. First, a linear analysis, in which the modal representation of the airframe flexible mode is added to a linearized model of the helicopter vertical motion and the helicopter dynamics is coupled with a single degree of freedom linearized model of the pilot biomechanics. Subsequently, a multibody model of the helicopter is coupled with the same linear model of the pilot, trimmed in hover and perturbed by a vertical gust. A sensitivity analysis shows that such mode has a significant influence on the stability of the closed loop system, especially if its frequency is close to the natural frequency of the pilot’s biomechanics, as one might expect.