General aviation pilots may fly continuously at altitudes up to 12,500 ft. without the use of supplemental oxygen. However hypoxia is a condition that can develop at altitudes under 12,500 ft. Research has shown highly variable tolerance and performance of individuals during low altitude laboratory exposures with simple and complex tasking. This study evaluated the physiological and subjective responses, as well as the simulated flight performance of general aviation pilots during a crosscountry flight scenario. Ten pilots of a mild hypoxia group were compared with 10 pilots of a normoxic control group. Measurements or flight performance from the Basic General Aviation Research Simulator (BGARS) and of flight-following procedures were gathered during a 3-day, 2 hr. per day, crosscountry flight scenario. Determined by group membership and terrain elevation during the crosscountry flight, subjects breathed either oxygen mixtures simulating sea level, 8,000 ft., lU.OUU ft., and 12,500 ft. altitudes or compressed air, throughout.-^ , \ n_m\ J The physiological measures of oxygen and carbon dioxide partial pressures (P tc C>2 and P tc C02), heart rate (HRj, and blood oxygen saturation (Sa0 2), provided significant results differentiating the 2 pilot groups and the 4 altitude conditions of the hypoxia group. No significant deviations from assigned altitude, VOR radials, or heading were found during cruise flight. However, significandy more procedural errors were committed by the hypoxia group during cruise flight at 10,000 ft. and during the descent and approach phases of flight from 10,000 ft. on Day 3 and during descent from 12,500 ft. on Day 4. Subjective measures of symptoms, workload, and stress provided limited evidence of hypoxic effects, although the hypoxia group reported significantly greater demands on their time during flight, compared to the control group. Also, significant group differences were found in flight following procedural errors, particularly during the descent and approach phases of flight. Recommendations are made to encourage GA pilots to plan their descents from flights above 10,000 ft. to allow sufficient recovery time as a routine precaution to the often undetectable effects of mild hypoxia.
