Physiological effects of thermal stress on aviators flying a UH-60 helicopter simulator

An evaluation of the physiological effects on aviators of heat stress (90 degrees F wet bulb globe temperature [WBGT]) versus a cooler condition (70 degrees F WBGT) when wearing either a MOPP0 (Mission-Oriented Protective Posture 0) uniform or a MOPP4 ensemble encumbered with a ballistic chest plate and overwater survival gear was performed at the United States Army Aeromedical Research Laboratory. The study used a repeated-measures design with 14 aviators flying 4-hour missions in a UH-60 helicopter simulator. Average crew endurance in the MOPP4-hot condition was reduced to one-third of the fully completed mission time of 309 minutes. For the hot condition, core temperature in the simulator rose 1.4 degrees F/hour when aviators wore the encumbered MOPP4 ensemble versus 0.27 degree F/hour when they wore the MOPP0 uniform. Sweating rate in the MOPP4-hot condition was 1,523 ml/hour, resulting in 2.5% dehydration, in contrast to 183 ml/hour and 0.9% dehydration in the MOPP4-cool condition. In this study, pilots flying realistic UH-60 simulator sorties rapidly incurred significant physiological heat strain when wearing an encumbered MOPP4 flight ensemble in hot cockpit conditions.