COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Radio Communication and Navigation Equipment AD/RAD/49 Collins TPR-720 ATC Radar Beacon System/Mode S Transponders 10/92 Applicability: TPR-720 Air Traffic Control Radar Beacon System/Mode S Transponders Part Numbers 622-7878-020 and 622-7878-120. Requirement: Either modify the transponder software in accordance with the instructions in Collins Service Bulletin 8, TPR-720-34-08 dated 19 September 1990 or alternately, modify the transponder hardware in accordance with the instructions in Collins Service Bulletin C, TPR-720-34-C dated 28 April 1992. Note: FAA AD 92-11-09 Amdt 39-8259 refers. Compliance: Prior to further flight in United States airspace after twelve calendar months from the effective date of this Directive. Background: The FAA has received numerous reports of an inability to track aircraft, equipped with the affected transponders, in high density air traffic areas because of transponder malfunctions. Compliance with this Directive prevents this type of transponder malfunction.