Physiological Factors and Subjective Fatigue Monitoring in Helicopter Pilots During UH-60 Missions

INTRODUCTION: Fatigue poses a serious risk to safety and performance in military aviation. Rotary-wing pilots operating in mountainous regions face unique physiological and cognitive demands, yet few studies evaluate both objective factors and subjective fatigue during real-world missions. METHODS: This study assessed fatigue in 25 UH-60 Black Hawk pilots and copilots during daytime visual flights in Tunceli, Türkiye. Measurements were taken at three phases: pre-, in, and postflight. Physiological factors (heart rate, oxygen saturation) and subjective fatigue (Samn-Perelli scale) were recorded. Paired-sample and Welch's independent t-tests were used for analysis. RESULTS: Oxygen saturation significantly declined from preflight (M = 96.2%) to in flight (M = 94.3%) and partially recovered postflight (M = 95.2%). Heart rate changes across phases were not statistically significant, although preflight heart rate was higher in copilots (M = 105.2 bpm) than in pilots (M = 87.8 bpm). Samn-Perelli scores rose significantly from pre- (M = 1.8) to postflight (M = 3.8), indicating perceptual fatigue accumulation. Copilots also reported greater preflight fatigue. DISCUSSION: Even moderate helicopter missions at altitude can cause measurable fatigue. The divergence between physiological recovery and subjective fatigue highlights the need to combine biometric and perceptual tools in fatigue monitoring and mission planning. Gevrek I, Ata N, Gevrek MI, Eroglu C. Physiological factors and subjective fatigue monitoring in helicopter pilots during UH-60 missions. Aerosp Med Hum Perform. 2026; 97(1):20-25.