The roll-sway problem and the effects of lateral specific force in full motion flight simulation

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The simulation of aircraft roll rates causes noticeable false g-tilt cues as a result of the simulator cabin roll angle. Although false tilt can be counteracted by swaying the simulator cabin, an improper implementation of the motion drive logic for coordinating sway could cause delayed side-forces. The aim of this paper is to evaluate two methods of driving the coordinating sway, the classical washout filter and the coordination algorithm, and compare those with uncoordinated motion. An experiment was conducted in which 12 experienced pilots performed side-step manoeuvres in a large generic transport. Six motion drive configurations were compared: no-motion, rotations only, coordinated rotations only for the two motion drive logics and full motion for both motion drive logics. Results show unaffected performance, but subjective motion fidelity ratings indicate that pilots prefer the uncoordinated rotations-only condition, suggesting that the current methods for simulation of coordinated turns can be improved upon. The highest rotational accelerations are found in experiment runs without simulator motion, which shows that pilot control behaviour is affected by the presence of motion; pilots steer less acute when motion is turned on. Results suggest that the industry standard, the University of Toronto Classical Washout filter, can be improved if coordinating sway is performed with less phase distortions, which can be achieved if scaling of the coordination sway is allowed and thus lowering high-pass sway filter break frequency becomes achievable within the limited hexapod motion space.