Biomedical cost of low-level flight in a hot environment.

The physiologic and performance effects of low-level reconnaissance flying in hot environments were documented and quantitated. RF-4C pilots and weapons system operators were studied in hot and cool seasons during both high and low missions to distinguish environmental temperature from flight level effects. ECG, sternal and thigh skin temperatures, and cockpit temperature at helmet level were monitored continuously. Body weights, oral temperatures, sweat Na/K ratios, and urine electrolytes, steroids, and catecholamines, as well as sleep and fatigue scores, were measured. Mission performance was assessed using photo target acquisition scores. RF-4C aircrews are exposed to moderate heat stress and acute dehydration (1.2% over 90 min) during low-level summer flights were cockpit temperature occasionally exceeded 50 degrees C. Photo target scores indicated that the potential for crew error was increased, and that the margin of safety was accordingly decreased, during such hot missions. The RF-4C cockpit air conditioning system proved inadequate.