Abstract
Each year, one third of the accidents in aeronautics are due to Spatial Disorientation (SD) phenomena. Pilots subject to SD misperceived their environment, which might induce possible dramatic changes in the pilots trajectory. These misperceptions come from diverse reasons : infraliminary magnitude of the gravito-inertial variations, bad weather conditions, non-coherent variations between stimuli... In this thesis, we investigated the perception and control mecanisms of self-motion during a Low-Altitude Flight (LAF) maneuver, which is a common, yet dangerous, military procedure. In LAF, pilots have to fly the nearest to the ground, at high speed. Two sets of experiments were led at the EuroMov laboratory (University of Montpellier, non-pilot participants) and the Ames laboratory (NASA, military expert pilots), in order to evaluate the impact of the visuo-vestibular contribution on height flight perception and control performances. Two different motion simulators, the iMose simulator (EuroMov) and the VMS (Vertical Motion Simulator, Ames) were used. During the experiments, the participants had to complete two tasks. The first one was an observer task of a simulated LAF scenario, in which participants had to report their height above ground. The second one was a controller task, in which participants had to control their height above ground during a simulated LAF scenario. Participants experienced several visuo-vestibular combinations. We studied their impact on the pilots performances. The results enlighted three main items : 1) Participants had a globaly more stable behaviour and better performances in a visuo-vestibular environment than in a visual-only one ; 2) visuo-vestibular stimuli impact the two experimental tasks differently; 3) a high fidelity simulated environment induces not necessarily better performances than a low fidelity one. These results are important for the world of simulation, where pilots performances depends on the simulated environment and its fidelity level. It is thus necessary to simulate coherent multimodal environments to observe realistic pilots behaviour. It would ensure a better training for real flight than with simplified environments.