Effects of mild hypoxia on pilot performances at general aviation altitudes.

Abstract

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.

Hypoxia and Flight Performance of Military Instructor Pilots in a Flight Simulator

“…This study identifi ed increased deviation errors in altitude, heading, airspeed, vertical velocity, and glide slope, with higher altitudes producing a greater error. A subsequent report assessed both fl ight performance accuracy and the occurrence of procedural errors during crosscountry fl ights in a general aviation simulator while oxygen-nitrogen mixes simulated an altitude up to 12,500 ft (3810 m) MSL ( 7 ). The results showed a significant increase in procedural errors due to hypoxia, but no convincing evidence for any impact on primary fl ight performance, i.e., the pilot's stick and rudder control of the aircraft.…”

General Aviation Hypoxia and Reporting Statistics

“…In general, hypoxia has been less of a concern for general aviation (GA) pilots because they are under the impression that the possibility of hypoxia is not likely due to their flight at lower altitudes. However, in the study entitled Effects of mild hypoxia on pilot performances at general aviation altitudes, the authors found that perceptual-motor performance at pressure-altitude equivalents of 7,000 and 12,000 feet in a hypobaric chamber had significantly slower response times at both altitudes as compared to sea level (Nesthus, Rush, & Wreggit, 1997). This FAAsponsored report explains that GA pilots demonstrated a significant decrease in human performance while flying at various altitudes and performing simple navigational tasks.…”

“…This report highlights the fact that the pilot in this scenario was able to recognize his symptoms and don his oxygen mask, a luxury most GA pilots do not have. It is rare to find GA pilots using oxygen equipment, even though the majority of GA aircrafts can reach altitudes where performance is affected, as seen in the study of Nesthus et al (1997).…”

The Effects of Hypoxic Hypoxia on Cognitive Performance Decay

“…Previous studies have shown cognitive impairment, such as slowed performance [4], but the emphasis of most studies has been on the severity of cognitive impairment relative to altitude, rather than the onset rate of impairment relative to a given altitude or mixed gas alveolar (lung) oxygen pressure (P A O 2 ). Some studies have addressed the effects of hypoxia up to 12,500 feet, without and with moderate exercise, on cognitive performance [5][6][7]. However, the results have been mixed and do not address acute hypoxia effects on performance breathing ambient or low oxygen percentage at altitudes higher than 12,500 feet.…”