Whole Body and Bare Hand Cooling at High Wind Speeds.

Abstract : Men were exposed in a wind tunnel with their backs to the wind, speeds 0 to 110 mph, at ambient temperatures of 21.1C (70F) to -31.7C (-25F) while hanging in a parachute harness clothed in Air Force flight suits at a simulated altitude of 600 feet. In summer flight suits exposures at 100 mph, -1.1C (30F) for 20 minutes following a standard precool of 10 minutes at 10 mph, were tolerated without frostbite. In winter flight suits, after precool at chosen ambient, men withstood 100 mph at -9.4C (15F) for 20 minutes and -17.8C (0 F) for 6.3 minutes. The latter test was terminated when skin on the calf reached the predetermined safety limit of 0 C (32F). At -17.8C (0 F) full 20-minutes exposure was tolerated at 50 mph. Considerable discomfort but no tissue cold damage attended the coldest runs when mean weighted skin temperatures fell as low as 16C (60.8F). Rectal temperatures rose slightly then started down near the end of each 30 minute test run. Skin temperatures measured with embedded thermocouples during direct bare hand exposures correlate well with Siple's low speed windchill data; and both provide excessively conservative exposure criteria for well clothed man. Clothed full body exposure data establish a conservative basis for estimating thermally safe temperature-wind speed regimes for towing men during air-to-air rescue maneuvers. (Author)