Heat stress in the A-10 cockpit: flights over desert

Heat stress is a significant problem during low-level flight in hot climates, especially in aircraft that impose high task loads and repetitive maneuvering forces. The A-10 close-support aircraft presents such a combined-stress environment. This report summarizes data from 15 low-level flights over desert. Ground dry-bulb temperature (Tdb,g) was 26-42 degrees C. Cockpit temperature (Tdb,c) was commonly over 40 degrees C on the ground and tended to drop progressively from taxi-out through flight to the range and return; for any given phase it was a linear function of Tdb,g. Small (50-mm) black globe temperature (Tbg,s) exceeded Tdb,c by 2-5 degrees C on the ground and by 4-8 degrees C in flight. The pilot's mean skin temperature was a linear function of Tdb,c in each phase. Auditory canal temperature (Tac) rose from a control value of 37.0 to a mean of 37.4 degrees C in flight, with one pilot reaching 37.8 degrees C. Sweat rate was a linear function of Tdb,g, with weight loss up to 2.3%. These data are compared to earlier studies of the F-4 and F-111 aircraft. Although the performance of the A-10's cooling system resembles that in other aircraft and is somewhat better than the F-4 on the ground, the effects of cockpit heat are exacerbated by its close-support role. Pilots noted lowered G-tolerance and increased general fatigue on the hotter flights. The foot- and leg-area temperatures exceeded those at the head; planned changes in air distribution should partly alleviate that situation.