The effect of the UK aircrew chemical defence assembly on thermal strain

The thermal strain imposed on helicopter aircrew by chemical protective (NBC) clothing in summer in Germany has been assessed in a laboratory simulation. The environmental conditions used were dry bulb temperature 35 degrees C, wet bulb temperature 19 degrees C and a wind speed of 2.0 m X s-1. The NBC equipment imposed a significant thermal strain on the crewman when compared with standard summer flying clothing, but not on the pilot whose tasks involve lower energy expenditures. Deep body temperature exceeded 37.6 degrees C and a significant degree of dehydration (1% of body weight) also occurred, despite the availability of a drinking facility in the respirator. It is recommended that the only practical way of preventing thermal strain in helicopter crewmen under NBC conditions is by providing personal conditioning.