{"id":"F2006B02123","name":"AD/AC/64 - Fatigue Life Limitation - Pressurised Fuselage","slug":"ad-ac-64-fatigue-life-limitation-pressurised-fuselage","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41353,"registerId":"commonwealth-F2006B02123-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC/64 - Fatigue Life Limitation - Pressurised Fuselage","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-description: CASA Airworthiness Directive\nmeta-generator: Aspose.Words for .NET 22.10.0\nmeta-keywords: Issue 6/1977,Aircraft below 5700 kg,Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes,Fatigue Life Limitation - Pressurised Fuselage,64\ntitle: Airworthiness Directive - AD/AC/64 - Fatigue Life Limitation - Pressurised Fuselage\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes\n\n \n\n \n\n| AD/AC/64 | Fatigue Life Limitation - Pressurised Fuselage | 6/77 |\n| --- | --- | --- |\n| Applicability: | Models 680T, 680V, 680W, 680FL(P), 681, 685, 690, 690A and 690B. |  |\n| Requirement: | Retire the pressure hull and related structure from service. |  |\n\n\n \n\nCompliance: For models 680T, 680V, 680W, 680FL(P), 681 and 690: On or before achieving 7500 pressurised flight cycles.\n\n \n\nFor models 685, 690a and 690B: On or before 10,000 pressurised flight cycles.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope. It addresses a specific airworthiness concern (fatigue life limits for pressurised fuselages) for a discrete set of aircraft models. There is no evidence of scope creep; the document remains a targeted safety directive without expansion into operational, maintenance, or certification matters beyond the specific structural retirement requirement."},"complexity_factors":["Extremely short document (approximately 200 words)","Only 9 specific aircraft models covered with straightforward applicability table","Simple binary compliance structure: two distinct flight cycle thresholds based on model type","No defined terms section, no cross-references to other legislation, no conditional exceptions","Single unambiguous requirement: mandatory retirement of pressurised structure","No procedural steps, no alternative compliance methods, no delegated legislative provisions"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of certain Twin Commander models to permanently retire their pressurised fuselages once they reach prescribed pressurised-flight-cycle limits (7,500 cycles for some models, 10,000 for others), effectively grounding those aircraft for pressurised operations at the threshold. \n\nIt’s intended to prevent catastrophic metal‑fatigue failure from repeated pressurisation cycles by imposing a hard service‑life limit on these older twin‑engine airplanes."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive sets clear, model-specific retirement thresholds for pressurised fuselages and does not indicate any expansion or narrowing of its original scope; it is limited to the listed models and the specified cycle limits."},"complexity_factors":["Narrow applicability: specific Twin Commander model list","Simple, numeric life-limits (7,500 or 10,000 pressurised flight cycles)","Single mandated action (retire pressure hull and related structure)","Operational requirement to monitor and record pressurised flight cycles to determine compliance","No procedural detail in text about retirement method, disposal, or alternative compliance options"],"plain_english_summary":"This Airworthiness Directive requires owners/operators of specified Twin Commander pressurised-fuselage models to retire the pressure hull and related structure from service once a fixed number of pressurised flight cycles is reached. It applies only to the listed models and sets firm lifecycle cut-offs rather than inspection or repair alternatives.\n\nDeadlines: models 680T, 680V, 680W, 680FL(P), 681 and 690 — retire at or before 7,500 pressurised flight cycles; models 685, 690A and 690B — retire at or before 10,000 pressurised flight cycles. Operators bear replacement/disposal and record-keeping costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-64-fatigue-life-limitation-pressurised-fuselage","history":"/api/acts/ad-ac-64-fatigue-life-limitation-pressurised-fuselage/history","analysis":"/api/acts/ad-ac-64-fatigue-life-limitation-pressurised-fuselage/analysis","conflicts":"/api/acts/ad-ac-64-fatigue-life-limitation-pressurised-fuselage/conflicts","importantCases":"/api/acts/ad-ac-64-fatigue-life-limitation-pressurised-fuselage/important-cases","documents":"/api/acts/ad-ac-64-fatigue-life-limitation-pressurised-fuselage/documents"}}