Heat stress in front and rear cockpits of F-4 aircraft.

Heat stress can be a serious problem in aircraft flown at low altitudes in warm-to-hot environments. Data are reported here on 36 flights by F-4 aircraft at Eglin AFB, FL. Ground dry-bulb temperatures (Tdb,g) were 19-33 degrees C (mean 28 degrees C) with psychrometric wet-bulb temperatures (Twb) 14-24 degrees C (mean 20 degrees C). Environmental and physiological data were recorded in both front and rear cockpits at 2-min intervals throughout each mission, which simulated low-level ground attack and lasted 94-126 min. Data were analyzed for four phases. A) preflight taxi, B) low-level flight, C) ordnance delivery, and D) postflight taxi. Cockpit dry-bulb temperature (Tdb,c) exceeded Tdb,g during ground operations; the front cockpit cooled in flight, while the rear remained hot. Linear relationships appeared for Tdb,c vs. Tdb,g in the four mission phases, and for globe temperature vs. Tdb,c. Aircrew mean skin temperature was significantly related to Tdb,c, and core (ear canal) temperature rose slightly with heat stress. Sweat rates reflected both Tdb,c and clothing worn. Discussion covers differences in air conditioning in the two cockpits and possible consequences of the observed heat stress and physiological strain.