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/54 Terra Transponders 10/95 Applicability: This Directive is applicable to the following Terra Corporation Air Traffic Control Transponders: 1. All push-button Model TRT 250 Part Number (P/N) 0900-0250-00 with Serial Numbers 4194 and below, modification level 4 and below, and b. All push-button three inch ATI mounted Model TRT 250 P/N 0900-0250-20 with Serial Numbers 5324 and below, modification level 4 and below, and c. All digital display Model TRT 250 D P/N 0900-0250-30 with Serial Numbers 1155 and below, modification levels 1 and below. Requirement: Modify the transponder in accordance with Terra Corporation International Service Bulletin ISB-004 dated 20 July 1995. Note: FAA AD 95-01-01 Amdt 39-9112 refers. Compliance: Prior to 30 September 1996. Background: Terra Corporation has advised that the Traffic Alert Collision Avoidance System (TCAS II) is incompatible with certain Terra transponders and that the transponders may not respond to TCAS II interrogations. This incompatibility could result in a loss of airspace separation between aircraft. This Directive mandates a modification that ensures that the affected transponders respond to TCAS II interrogations.