Amplified ego motion drift indication for helicopter landing

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Schmerwitz, S.
Knabl, P.M.
Lueken, T.
Doehler, H.-U.
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Helicopter flight in degraded visual environment (DVE) can pose a serious safety hazard especially during lowlevel operations. One cause for rapidly losing the visual cues is introduced by surface properties such as sand or snow. They are prone to stir up particles due to the helicopters downwash and encase the helicopter in a nontransparent cloud. This effect is referred to as brownout or whiteout. Under such conditions lateral speeds introduce a high risk that when touching the ground may cause the helicopter to rollover. Therefore helicopter operators could benefit from some type of "drift indication" that mitigates the influence of degraded visual environment. To enhance the perception of ego motion in a conformal HMD symbol set the measured own ship movement was used to generate a "pattern motion" in the forward field of view close or on the landing pad [4]. As a next step the part task study presented here takes a closer look at the mechanism of subconscious drift indication. It is believed that providing this type of constant subliminal information can enhance the reaction time to unforeseen movements like from gusts. The study focused on none-professional participants. 31 candidates took part in this study. The main task was to steer the lateral position to the center of the presented landing pad. A second task forced the participant to react as fast as possible to a frequent presentation of two different characters on the display. The experiment was displayed on an Oculus Rift DK2™ virtual reality glass. The added "pattern motion" significantly supported participants in assessing drift, which reflected in lower lateral speeds during touchdown compared to the static presentation. Two of the three visualization concepts did not show a change in reaction time of the secondary task. Only marginally fewer correct responses to the secondary task were found. 24 candidates favoured the moving presentation rather than the static one. Few but some participants experienced pilot induced oscillation revealing that the chosen gain might have been too large. A follow-up experiment will try to optimize the gain.