BACKGROUND: Adequate instrument scanning is considered an important countermeasure against spatial disorientation (SD). Remarkably, literature on the relation between SD and pilots’ visual scanning is scarce. The objective of this simulator study was to investigate the influence of SD on pilots’ visual scanning and flight performance.METHODS: In a ground-based SD simulator, 10 novice military pilots were asked to manually fly 3 circuits. Unknowingly to the pilots, the final circuit contained one visual and four vestibular SD events. Simulator motion, flight performance, pilots’ gaze direction, and control inputs were recorded and analyzed. Afterwards the pilots filled in a questionnaire about their recognition of events.RESULTS: Three of the five SD events significantly affected pilots’ flight performance and gaze behavior. First, the false horizon during the cloud leans induced an unintended roll rate, 0.41 ± 0.36° · s⁻¹, when the pilots were looking out the window. Second, the Coriolis illusion caused a 0.44 ± 0.18 s delay in the first glance to the attitude indicator and triggered an unintended roll rate, 1.25 ± 1.33° · s⁻¹, and bank angle deviation of 3.4 ± 3.7° during the coordinated turn. Third, the somatogravic illusion affected pilots’ pitch inputs on the stick, but this seems to be confounded by inaccurate simulation of the illusion.DISCUSSION: This study provides direct experimental evidence that SD can evoke inappropriate control inputs and can influence the pilots’ scanning behavior, even when SD is not recognized. We conclude that gaze tracking provides useful feedback on the pilot’s instrument scan during SD simulator training when using appropriate scenarios and simulator motion.Ledegang WD, Groen EL. Spatial disorientation influences on pilots’ visual scanning and flight performance. Aerosp Med Hum Perform. 2018; 89(10):873–882.