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Pilot–vehicle interaction represents a critical aspect of aircraft design. Very low-frequency, voluntary although unintentional interaction has been extensively investigated in fixed and rotary wing aeromechanics. Higher frequency, involuntary and thus passive interaction received similar attention in fixed wing aeromechanics, but not as much for rotary wing. The results of an experimental campaign for the characterization of the passive behaviour of rotorcraft pilots' biomechanics are presented. A flight simulator has been used to excite human subjects. The accelerations of their limbs and the motion induced by the vibrations of the limbs in the control inceptors have been recorded. The vertical, longitudinal and lateral directions have been independently excited, while measuring the motion of the arm directly involved in the control inceptor mostly affected by motion in each direction, namely the left and the right arms for the collective and the cyclic sticks, respectively. The frequency domain response has been evaluated; resulting noteworthy behaviour is discussed, addressing its relevance in modelling the passive behaviour of pilots within the bioaeroservoelastic rotorcraft analysis. The measurements of human body impedance, under realistic cockpit motion, are used to identify the direct transfer functions between the motion of the seat and the controls inadvertently fed back into the rotorcraft.

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The involuntary interaction of pilots with vehicles is often an undesired consequence of the biodynamic feedthrough of cockpit vibrations into the control system in relation with the characteristics of the man-machine interface. This work presents a numerical study of how the estimated muscular activation patterns associated with performing basic helicopter piloting tasks may affect the variability of the pilot's biodynamic feedthrough and admittance. The limbs' motion is predicted using an inverse kinematics formulation for redundant manipulators imposing the motion of the hand from measurements. Articulation torques are then estimated by inverse dynamics. Activation of the involved muscles is estimated according to the 'total activation' paradigm. Equivalent pilot feedthrough is obtained by consistent linearization of the constitutive model of the muscles about the reference activation. The effect on equivalent feedthrough of nonoptimal activation, resulting from the addition of torque-less activation modes to the optimal activation, is evaluated and discussed. The multibody model of the pilot's biodynamic feedthrough is incorporated in a detailed multibody model of a helicopter, to perform coupled bioaeroservoelastic simulations.