BACKGROUND: Circumstances in flight can adversely affect a pilots spatial abilities and lead to spatial disorientation (SD), increasing the potential for fatal accidents. To systematically understand the impact of SD, it is important to quantitatively and qualitatively analyze pilots flight performance and mental stress, and to verify the effectiveness of verbal reports (VR) in enabling pilots to deal with an SD situation. This study investigated the effects of VR execution and type of SD on flight performance and mental stress.METHODS: SD simulation experiments were conducted on 30 Air Force fighter pilots (15 in the VR group and 15 in the non-VR group) with electrocardiography (ECG) sensors attached. The pilots gave their VRs by immediately verbalizing their attention to instrument information and six potentially disorientating scenarios were implemented in each flight phase. Flight performance was analyzed using instructor evaluation and self-evaluation scores, and mental stress was measured using heart rate variability (HRV) and perceived distress score.RESULTS: In maintaining flight performance, the VR group, respectively, had 8% and 10% higher scores for altitude and speed than the non-VR group. The self-evaluation scores were lowest for Coriolis, while Graveyard Spin was scored lowest in the instructor evaluations. Regarding mental stress, the VR group tended to have higher HFs and lower LF/HF ratios among HRV measures than the non-VR group, and an 11% lower perceived distress score. The highest perceived distress score was for Coriolis.DISCUSSION: We suggest that pilots can be assisted to understand and overcome SD situations through VR.Kang Y, Yun MH, Kim S. Verbal reports influence on pilot flight performance and mental stress under spatial disorientation. Aerosp Med Hum Perform. 2020; 91(12):948955.