The ACE-804 Air Conditioning and Air Conditioning/Heating Units provide maximum passenger comfort in all types of aircraft. Available in a wide variety of configurations, these units meet the requirements of all aircraft operators regardless of fleet size or local ambient conditions. The Units employ an air-to-air type refrigeration system and , for operators requiring heat, can be supplied with an optional reverse-cycle “heat-pump” system. Provisions are made to utilize engine coolant heat to augment the reverse cycle heat mode. There are no dangers of combustion or its by-products near the aircraft. The “Change-Over” from one mode to another is so simple that it can be performed by operator on the ramp. Heating and cooling modes are available ad required throughout the day without taking the unit out of service for adjustment.