Thermal study of anti-G ensembles aboard F-16 aircraft in hot weather

Continuing advances in the performance of new fighter aircraft have engendered requirements for more sophisticated protective clothing and life support systems. A major goal is prevention of acceleration-induced loss of consciousness. The USAF's Advanced Technology Enhanced Design G-Ensemble (COMBAT EDGE) increases acceleration tolerance by providing positive pressure to the oxygen mask; the work of pressure breathing is reduced by adding a counter-pressure bladder over the chest. However, the addition of impermeable layers over the chest reduces the area available for evaporation of sweat. This study was designed to determine whether COMBAT EDGE (CE) was demonstrably hotter than standard summer flight clothing (ST) during F-16 sorties in hot weather. Eight male pilots served as volunteer subjects, each flying missions at 1430 and 1745 h on two consecutive days, one day with CE and the other with ST. Data were logged at 1-min intervals for rectal temperature (Tre), skin temperatures at the chest and thigh (Tch and Tth) and air temperatures outside the clothing at the same two sites (Tach and Tath). The weather was stable over the 4 d of data collection with highs of 34-36 degrees C and simultaneous dewpoints of 19-23 degrees C (relative humidity 35-45%). The mean Tach was stable at 28 degrees C in flight, while individual means for Tath ranged from 22 to 25 degrees C. The lower value and greater variability at the thigh reflect its proximity to the air conditioning vent. Despite the differences in air temperature, Tch and Tth remained in the range 34-36 degrees C throughout the flights.(ABSTRACT TRUNCATED AT 250 WORDS)