Abstract
The power and weight requirements of refrigeration equipment constitute a real limitation of aircraft performance at the present stage of aircraft development from the standpoint of thermal tolerance. Since man is the weak link among the components of the aircraft system, a clear understanding of the responses of humans to heat is vital to the achievement of an optimal balance between air conditioning and performance characteristics of the airplane. To obtain the highest combined fitness of man and aircraft for the exigencies of modern air warfare, it is necessary to abandon the time-honored concept that human thermal comfort must be assured, and to substitute the principle of maintaining the physiological and performance effectiveness of the crew for the limited period of the particular flight duration. When this duration is to be many hours, the efficiency criterion will probably demand an environment which also meets the traditional comfort standards.
