This SAE Recommended Practice applies to highway trailer tow bar eye-type applications@ including multiple trailers. These standards are written to cover internal combustion heat exchanger type heaters used in the following application: Cabin heating. (All occupied regions and windshield heating.) Wing and empennage heating. Engine and accessory heating. (When heater is installed as part of the aircraft.) PURPOSE: To specify standards covering minimum safety and performance requirements for internal combustion heaters and certain auxiliary devices which are considered necessary to the safety and performance of the heaters as used in aircraft. These standards are to be considered currently applicable and necessarily subject to revision from time to time due to rapid development of the aeronautical industry. The following standards are based on practical engineering requirements for such internal combustion heat exchanger type heaters as are now used on airplanes and for such as may be developed to meet later requirements.