{"id":"F2006B09912","name":"AD/F50/81 - TCAS Antenna Structural Provisions","slug":"ad-f50-81-tcas-antenna-structural-provisions","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55113,"registerId":"commonwealth-F2006B09912-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.","sortOrder":0},{"sectionNumber":"AD/F50/81 TCAS Antenna Structural Provis","sectionType":"part","heading":"AD/F50/81 TCAS Antenna Structural Provisions 2/2001","content":"# AD/F50/81 TCAS Antenna Structural Provisions 2/2001\n\nApplicability: Model F.27 Mk. 050 aircraft, serial numbers 20168, 20171, 20177, 20180, 20181,\n\n20185 through 20188, 20193 through 20195, 20198, 20199, 20207 through 20209,\n\n20215 through 20219, 20221, 20233, and 20271.\n\nRequirement: Reinforce the affected structure in accordance with the Accomplishment Instructions of Fokker SB F50-53-054, dated May 1 2000.\n\nNote: RLD AD 2000-152 refers.\n\nCompliance: Within the next 12,000 flight cycles after installation of the TCAS antenna.\n\nThis Airworthiness Directive becomes effective on 22 February 2001.\n\nBackground: During a product review, Fokker Services discovered that the structural provisions for the installation of the Traffic Collision Avoidance System (TCAS) top antenna do not meet the pertinent requirements. This condition, if not corrected, could result in reduced service life of the affected structure. This Directive requires installation of an external doubler under the antenna.\n\n![](image.003.png)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 12 January 2001\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 24 January 2001.","sortOrder":1}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard single-issue airworthiness directive addressing one specific technical defect in a defined aircraft population. The scope remains tightly focused on the original safety issue identified by the manufacturer."},"complexity_factors":["Single, clearly defined applicability (22 specific aircraft serial numbers)","One straightforward requirement referencing a single external technical document","Simple compliance trigger (time-based, 12,000 flight cycles)","No defined terms section","No cross-references to other legislation beyond a single note referencing a Dutch aviation authority document","No conditional logic or exceptions","Short document (approximately 250 words of substantive content)"],"plain_english_summary":"This safety order requires owners of 22 specified Fokker F.27 Mk.050 aircraft to reinforce the metal structure beneath the TCAS top antenna by installing an external doubler to remedy a discovered mounting weakness.  \n\nAffected operators must carry out the modification per Fokker Service Bulletin SB F50-53-054 (May 2000) within 12,000 flight cycles of antenna installation; the order takes effect 22 February 2001."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Scope has not changed from the document's stated purpose: it targets the identified TCAS top-antenna structural shortfall on the listed Fokker F.27 Mk. 050 serial numbers and prescribes a specific corrective action and compliance window. The AD does not expand applicability or alter the remedy beyond the stated Service Bulletin requirement and flight-cycle compliance metric."},"complexity_factors":["Narrow applicability to a defined list of F.27 Mk. 050 serial numbers (see \"Applicability\").","Prescriptive technical remedy: work must follow Fokker SB F50-53-054 dated 1 May 2000 (see \"Requirement\"), limiting operator discretion on method.","Compliance metric tied to aircraft utilisation: deadline is expressed as 12,000 flight cycles after TCAS antenna installation (see \"Compliance\").","Operational and financial burden falls on aircraft owners/operators to perform structural reinforcement (implied by Requirement and Background).","Regulatory basis and enforceability: AD issued under CAR 1998 subregulation 39.1(1) and given an effective date (see opening paragraph and effective date).","Safety rationale documented: condition discovered in product review could reduce service life of affected structure, driving mandatory corrective action (see \"Background\")."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of specified Fokker F.27 Mk. 050 aircraft to reinforce the structure under the TCAS top antenna by installing an external doubler in accordance with Fokker Service Bulletin F50-53-054. Compliance must be done within 12,000 flight cycles after TCAS antenna installation; the aircraft operators bear the cost and must schedule the work to prevent reduced structural service life."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-81-tcas-antenna-structural-provisions","history":"/api/acts/ad-f50-81-tcas-antenna-structural-provisions/history","analysis":"/api/acts/ad-f50-81-tcas-antenna-structural-provisions/analysis","conflicts":"/api/acts/ad-f50-81-tcas-antenna-structural-provisions/conflicts","importantCases":"/api/acts/ad-f50-81-tcas-antenna-structural-provisions/important-cases","documents":"/api/acts/ad-f50-81-tcas-antenna-structural-provisions/documents"}}