Handling Qualities and Aircraft Pilot Coupling: New Evidence of Neuromuscular Origins

Publication Date


Document Type

Conference Proceeding

Publication Title

AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022




Prior research indicates that the frequency of the open-loop pilot arm neuromuscular (NM) mode is a function of muscle stiffness which is affected by the limb and inceptor feel-system inertia. A piloted simulation experiment demonstrated that vehicle command type significantly influences the open-loop NM response, likely due to muscle stiffness adapting to task demands including inceptor sensitivity and tracking task disturbance forcing function. The analysis in this paper builds on Hess’ pilot Structural Model (SM), bringing new evidence that points towards 1) variability of key parameters that are assumed fixed in the SM, and 2) a generalized form of the SM’s pilot neuromuscular (NM) compensation, arising from limitations imposed by the NM mode dynamics. These findings are applied to roll ratchet (an adverse Aircraft Pilot Coupling (APC) phenomenon), and to predicting handling qualities ratings (HQRs). Ratchet is an APC characterized by oscillations near the closed loop NM mode frequency. Preliminary results suggest a potential source for ratchet is the sensitivity of the pilot’s stick activity to variations in the NM time delay. The paper proposes that the compensatory aspect of HQR is driven entirely by the NM feedback gain, reflecting the costs of lead, lag and time delay associated with a given level of performance.


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