This report sets forth Environmental Test Procedures applicable to airborne radio equipment. The purpose of these tests is to provide a laboratory means of determining the reliability of the equipment by evaluating its perfor:aa.'1ce under conditions repre3antat.i'T-3 of those which may be encountered in actual aeronautical operations. The formulation of these Test Procedures was undertaken by the RTCA at the request of the Civil Aeronautics Administration for application in connection with the approval of airborne radio equipment. Civil Air Regulations. currently in effect as of the date of this report require the installation of approved radio equipment only in scheduled air carrier aircraft. However@ in that the objective of the Environmental Test Procedures is the improvement of the reliability ty of airborne radio equipment under actual service operating conditions@ it is the recommendation of RTCA that they be considered for application in all future developments of such equipment.