{"id":"F2006B06511","name":"AD/RAD/54 - Terra Transponders","slug":"ad-rad-54-terra-transponders","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48096,"registerId":"commonwealth-F2006B06511-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/RAD/54 - Terra Transponders","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nRadio Communication and Navigation Equipment\n\nAD/RAD/54 Terra Transponders 10/95\n\nApplicability: This Directive is applicable to the following Terra Corporation Air Traffic Control Transponders:\n\n    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\n\n    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\n\n    c. All digital display Model TRT 250 D P/N 0900-0250-30 with Serial Numbers 1155 and below, modification levels 1 and below.\n\nRequirement: Modify the transponder in accordance with Terra Corporation International Service Bulletin ISB-004 dated 20 July 1995.\n\nNote: FAA AD 95-01-01 Amdt 39-9112 refers.\n\nCompliance: Prior to 30 September 1996.\n\nBackground: 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.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific technical incompatibility identified by the manufacturer. It has not expanded beyond its original purpose of mandating a specific hardware modification to identified transponder models."},"complexity_factors":["Single, specific applicability criteria based on part numbers, serial numbers, and modification levels (three distinct equipment variants)","Single mandatory action with clear reference to external technical document (Service Bulletin ISB-004)","Simple compliance deadline (single date, no phased or flight-hour based requirements)","No defined terms section or interpretive provisions","No nested exceptions or conditional logic — applies straightforwardly to identified equipment","Brief background explanation included but not legally operative","Cross-reference to FAA AD 95-01-01 for context only, not for substantive requirements"],"plain_english_summary":"CASA requires owners and operators of certain Terra TRT 250 transponders to carry out a mandatory hardware modification per Terra Service Bulletin ISB‑004 to restore TCAS II compatibility. It affects aircraft with the specified older units and their maintenance organisations; the fix prevents a TCAS “blind spot” and must be completed before 30 September 1996."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The instrument is narrowly targeted to specified Terra TRT‑250 units and mandates a one-off hardware/software modification to restore TCAS II compatibility. The text gives no indication that the Directive expands or narrows scope beyond that remedial purpose."},"complexity_factors":["Narrow, technical applicability defined by model, part numbers, serial number ranges and modification levels","Reliance on an external technical document (Terra Service Bulletin ISB-004) for the specific modification instructions","Safety-critical interoperability issue (TCAS II) increases urgency and enforcement attention","Fixed compliance deadline (30 September 1996) requiring timely coordination and technical work","Reference to a related FAA airworthiness directive (cross-jurisdictional linkage)"],"plain_english_summary":"This Directive, issued under the Civil Aviation Regulations, requires operators of specified Terra TRT‑250 transponders (listed by model, part number, serial number ranges and modification levels) to have those units modified in accordance with Terra Service Bulletin ISB‑004 (20 July 1995). The Civil Aviation Safety Authority mandates completion before 30 September 1996.\n\n**Purpose:** The mandated modification fixes an identified incompatibility with TCAS II that may prevent the transponders responding to TCAS II interrogations and could reduce airspace separation."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rad-54-terra-transponders","history":"/api/acts/ad-rad-54-terra-transponders/history","analysis":"/api/acts/ad-rad-54-terra-transponders/analysis","conflicts":"/api/acts/ad-rad-54-terra-transponders/conflicts","importantCases":"/api/acts/ad-rad-54-terra-transponders/important-cases","documents":"/api/acts/ad-rad-54-terra-transponders/documents"}}