{"id":"F2006B04507","name":"AD/BELL 206/51 Amdt 2 - Vertical Fin Support Forgings","slug":"ad-bell-206-51-amdt-2-vertical-fin-support-forgings","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114207,"registerId":"commonwealth-F2006B04507-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 206/51 Amdt 2 - Vertical Fin Support Forgings","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBell Helicopter Textron Canada (BHTC) 206 and Agusta Bell 206 Series Helicopters\n\nAD/BELL 206/51\n\nAmdt 2\n\n  \nVertical Fin Support Forgings 8/93\n\nApplicability: All models with serial numbers referenced in the Requirement Documents.\n\nRequirement: 1. For aircraft equipped with a vertical fin assembly which has an external doubler installed on the left-hand side, adjacent to the support forgings - inspect and modify in accordance with Bell Alert Service Bulletin 206-91-60, dated 28 June 1991, or Agusta Bollettino Technico 206-202, dated 20 July 1992, as appropriate.\n\n2. For aircraft equipped with a vertical fin assembly which does not have a doubler installed \\- inspect in accordance with Bell Service Bulletin 206-01-73-5 Revision A, dated 21 September 1973.\n\nNote: FAA AD 73-21-3 refers.\n\nCompliance: For Requirement 1: Unless already accomplished, at the next inspection for issue of a Maintenance Release (this shall mean a period not exceeding 110 hours time in service) or by 19 August 1993 whichever occurs first.\n\nFor Requirement 2: Unless already accomplished within the last 1000 hours, at the next inspection for issue of a Maintenance Release (this shall mean a period not exceeding 110 hours time in service) or by 12 March 1991 whichever occurs first.\n\nBackground: Amendment 1 was the result of further instances of cracking in the fin support forgings. For those aircraft fitted with a doubler, action was provided to alleviate unacceptable stress in the forgings. Amendment 2 has been raised to include the Agusta Bell model 206.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 2 expands the AD to include Agusta Bell model 206 aircraft and follows earlier Amendment 1 which introduced actions to address further cracking; it therefore broadens the fleet covered and adds a modification path for aircraft with a doubler (Background; Requirement)."},"complexity_factors":["Conditional requirements depending on whether an external left‑hand doubler is installed (Requirement).","Multiple referenced service documents (Bell Alert Service Bulletin 206-91-60; Agusta Bollettino Technico 206-202; Bell Service Bulletin 206-01-73-5 Rev A) require following external procedures (Requirement).","Different compliance deadlines: ‘next Maintenance Release (≤110 hours)’ or fixed calendar dates, and a separate ‘within last 1000 hours’ trigger for some aircraft (Compliance).","Applicability limited to specific serial numbers, so operators must check serial lists in the service documents (Applicability; Requirement).","Maintenance terminology and thresholds (definition of Maintenance Release as ≤110 hours) create implementation detail that maintenance teams must track (Compliance)."],"plain_english_summary":"This airworthiness directive requires owners/operators of specified Bell and Agusta Bell 206-series helicopters to inspect—and, if fitted with an external left‑hand doubler, modify—the vertical fin support forgings according to the Bell or Agusta service bulletins referenced in the AD. Operators must complete the inspection or modification at the next Maintenance Release (defined here as within 110 flight hours) or by the specific dates set out in the AD (Requirement; Compliance). Operators pay for the work; CASA issued the directive and sets the deadlines."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original AD (implied by Amendment 1) covered Bell helicopters only. Amendment 2 explicitly expands scope to include 'Agusta Bell model 206' helicopters, broadening the directive's reach to additional aircraft variants. This is a modest expansion consistent with the original safety purpose (addressing the same mechanical defect in similar aircraft), rather than a fundamental change in the AD's intent."},"complexity_factors":["Short, single-purpose document (approximately 250 words)","Only 2 defined scenarios (with doubler vs without doubler)","Clear binary applicability test","Simple compliance timeline with 'whichever occurs first' logic","References external technical documents (Service Bulletins) but does not incorporate their content","No nested exceptions or conditional sub-clauses","Minimal cross-referencing (single FAA AD reference in a note)"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections and repairs to Bell 206 and Agusta Bell 206 series helicopters to detect and fix cracking in the vertical fin support forgings. It requires operators to follow the relevant Bell or Agusta service/bulletin procedures, with different inspections depending on whether an external doubler is installed.\n\nThe AD is compulsory because forging cracks can lead to tail‑fin failure and loss of control. Amendment 2 extends the original directive to include Agusta Bell models."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-206-51-amdt-2-vertical-fin-support-forgings","history":"/api/acts/ad-bell-206-51-amdt-2-vertical-fin-support-forgings/history","analysis":"/api/acts/ad-bell-206-51-amdt-2-vertical-fin-support-forgings/analysis","conflicts":"/api/acts/ad-bell-206-51-amdt-2-vertical-fin-support-forgings/conflicts","importantCases":"/api/acts/ad-bell-206-51-amdt-2-vertical-fin-support-forgings/important-cases","documents":"/api/acts/ad-bell-206-51-amdt-2-vertical-fin-support-forgings/documents"}}