Fighter index of thermal stress: Development of interim guidance for hot-weather USAF operations

Operation of fighter and trainer aircraft in hot climates can impose significant heat strain on aircrew members. Until now, commanders have lacked practical guidance for aircrew thermal protection. A primary obstacle has been the paucity of data relating cockpit conditions to ground weather, but that gap is now being filled. A review of existing heat-stress indices revealed that none of them met the criteria for operational practicality. The Wet Bulb Globe Temperature (WBGT) Index was selected as a starting point because of the large data base already available. A new scheme was then developed, the Fighter Index of Thermal Stress (FITS), which uses recently acquired cockpit data to generate predictive equations. The final product is a single table from which base personnel, using only conventional weather data (ambient air temperature and relative humidity), can read FITS values. Normal, Caution and Danger Zones are designated on the chart, based upon estimates of aircrew physiological status and the need to avoid significant performance decrements. Appropriate protection procedures are recommended for each zone.