The recommendations of this SAE Aerospace Recommended Practice (ARP) for aircraft compartment automatic temperature control systems are primarily intended to be applicable to occupied or unoccupied compartments of civil and military aircraft.The purpose of this ARP is to outline the design considerations and criteria for automatic temperature control systems, for use as a guide in the aircraft industry. In most environmental control systems (ECS), temperature control is accomplished by an ECS controller; several of the control schemes discussed are based on these controllers. These recommendations are representative of present engineering practices, and necessarily subject to revision from time to time due to rapid development of the industry.