The role of visual cues and whole-body rotations in helicopter hovering control

Helicopters in flight are unstable, and hovering at one spot requires the pilot to do a considerable amount of active control. To date, it is still under discussion which sensory cues helicopter pilots use for this stabilization task, and how these cues are combined. Here we investigated how cues from different sensory modalities (visual cues and body cues) are used when humans stabilize a simulated helicopter at a target location in a closed perception-action loop. Participants were seated inside a closed cabin on a Stewart platform equipped with a projection screen. They had to stabilize a simulated helicopter on a target spot. To investigate the influence of individual visual cues on the stabilization, a minimalistic visual scene was used. Two spheres in the scene represented the location of the target and the position of the helicopter. Optical flow was provided by world-stationary random dots, and a horizon was produced by a black ground plane and white sky. We measured stabilization performance in ten different conditions: black background, horizon, optical flow, both horizon and optical flow, and horizontal stripes; all of these both with and without platform rotation cueing. Physical pitch and roll body rotations were presented by tilting the platform exactly as the simulated helicopter tilted. Our results show that all manipulated cues - horizon, optical flow, and platform rotations - can help the participants to stabilize a simulated helicopter. In particular, adding physical rotation cues to visual stimulation in a simulator can significantly improve the ability of trained participants to stabilize the simulated helicopter at a target location.