ABSTRACT
The aviation environment provides some thermal aspects which, if not absolutely unique, can be extremely challenging for the aviator. Aviation is a global activity, and spans the full range of climatic conditions. Furthermore, as one ascends, the air temperature generally falls at a rate of approximately 2°C per 1000 feet, up to the isothermal layer of the atmosphere. Exposure to cold at altitude can thus be a very significant problem for the occupants of aircraft with open cockpits or helicopters that are required to fly with their doors open for operational reasons, and for high-altitude balloonists or parachutists. However, heat stress is a more common problem than cold stress, as a result of hot operating environments, the various sources of heat in the cockpit and the many layers of specialized clothing that military aviators may have to wear. The ground environment may be a source of heat stress not only for the ground support personnel, but also for the aircrew during their preflight preparations and standby. The high-speed nature of modern flight means that in a matter of hours individuals may be transported from one thermal environment to a completely different one, to which they may not be acclimatized. Finally, if an emergency occurs in flight, the aircraft occupants may be faced with having to survive in whatever environment the aircraft was flying over at the time of the emergency.
