A Procedure for Inducing the Leans Illusion in a Hexapod Motion Simulator

Ground-based demonstration of spatial disorientation (SD) has been recommended for military as well as commercial pilot training. Although the leans illusion is the most common form of SD, no data exist yet of an effective ground-based leans procedure for a hexapod simulator. In this paper we describe the development of such a procedure and its tuning with nine subjects. The procedure was then used in an experiment with 18 airline pilots, which is described elsewhere. The final procedure started with a prepositioning phase, during which the simulator platform was slowly tilted to a 3.5° prepositioning roll angle, while the pilot performed a distraction task and the instruments and outside visuals indicated level flight. Next followed an adaptation phase, during which the pilot's vestibular system adapted to the new angle, the outside visibility degraded to zero and the instruments were covered. Then the platform was moved back to level, above the perceptual threshold, after which the instruments were shown again. The pilot was then tasked to roll back to level. The addition of the motion cues caused an increase in roll reversal errors by a factor of 3 in airline pilots. The procedure can be implemented in a scenario for demonstrating the leans in a cost-effective simulator.