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Meeting Abstract

Simulation of the Gillingham Postroll illusion

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Nooij, S., Beckers, N., & Groen, E. (2010). Simulation of the Gillingham Postroll illusion. Aviation, Space, and Environmental Medicine, 81(3), 312.

Cite as: https://hdl.handle.net/11858/00-001M-0000-0013-C118-9
INTRODUCTION: The somatogyral effect (i.e. the ceasing rotation perception during constant velocity rotation and the accompanying perception of rotation in the opposite direction when rotation stops) is often demonstrated to student pilots during earth vertical yaw rotation.
However, during roll movements, such as in a coordinated turn, this illusion may also occur and is referred to as the Gillingham Postroll illusion. Due to different sensory dynamics in yaw and roll, the effect occurs much faster than in roll than in yaw and may therefore be more
frequently encountered. In this study we first investigated the effect of coordinated roll movements on the pilot’s control behaviour. Our second aim was to develop a dedicated simulator-demonstration for student pilots.
METHODS: The experiments took place in the Desdemona
motion simulator. Because during a fully coordinated roll movement the gravito-inertial vector is always fixed in relation to the body the cabin was tilted 90° backwards so that the subject’s roll-axis was earthvertical.
Roll motions were either fully automated or self-controlled by having the subject follow a lead aircraft making the required movements. Right after the roll movement the subject was instructed to “hold attitude”, so to cancel all perceived simulator motion without having visual reference. The subject’s stick input and the resulting simulator motion were measured. Roll velocity and duration were varied
in order to obtain different magnitudes of the expected aftereffect (12s at 10°/s, 2s at 30 and 60°/s and 6s at 30 and 60°/s).
RESULTS: Subjects indeed corrected for the perceived (not physical!) rolling back when the roll movement had stopped. They initiated a roll motion in the same direction of the original movement, illustrating the somatogyral effect. Effects were largest when the motions were self-controlled
and the magnitude of the correction was correlated with the size of the expected aftereffect.
DISCUSSION: The results are in line with a model of the dynamics of the semicircular canals. The man-in-the-loop scenario proved adequate to provide a flight-realistic demonstration of the Gillingham Postroll Effect.