{"id":"F2006L00448","name":"AD/BELL 412/40 Amdt 1 - Main Rotor Yoke","slug":"ad-bell-412-40-amdt-1-main-rotor-yoke","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":117140,"registerId":"commonwealth-F2006L00448-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Bell Helicopter Textron 412 Series Helic","sectionType":"division","heading":"Bell Helicopter Textron 412 Series Helicopters","content":"### Bell Helicopter Textron 412 Series Helicopters\n\n| AD/BELL 412/40 Amdt 1 | Main Rotor Yoke | 3/2006 |\n| --------------------- | --------------- | ------ |\n\n| Applicability: | Model 412 and 412EP helicopters, serial numbers 33001 through 33213, 34001 through 34036 and 36001 through 36204; and Model 412CF helicopters, serial numbers 46400 through 46499; and All Model AB 412 helicopters: equipped with a main rotor yoke assembly part number 412-010-101-123 or -127.                                          |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Action in accordance with Bell Helicopter Textron Alert Service Bulletins No.412-98-93, or No. 412CF-98-5, or Agusta Alert Technical Bulletin No. 412-74, as applicable.Note: FAA AD 99-23-23 and ENAC AD 1999-179 refer.                                                                                                                   |\n| Compliance:    | As specified in the Requirement documents, as applicable.                                                                                                                                                                                                                                                                                   |\n|                | This Amendment becomes effective on 16 March 2006.                                                                                                                                                                                                                                                                                          |\n| Background:    | The manufacturer determined that main rotor yokes which measured less than 0.478\" across a specific portion of the flexure area, does not have a sufficient fatigue margin of safety and have therefore reduced the life by 500 hours time in service.Amendment 1 is issued to include the Agusta Model AB 412 helicopter in applicability. |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n2 February 2006","sortOrder":0},{"sectionNumber":"AD/BELL 412/40 Amdt 1","sectionType":"part","heading":"AD/BELL 412/40 Amdt 1","content":"## AD/BELL 412/40 Amdt 1","sortOrder":1},{"sectionNumber":"Main Rotor Yoke","sectionType":"part","heading":"Main Rotor Yoke","content":"## Main Rotor Yoke","sortOrder":2},{"sectionNumber":"3/2006","sectionType":"part","heading":"3/2006","content":"## 3/2006","sortOrder":3}],"analysis":{"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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"The original AD (implied by 'Amendment 1') only covered Bell-manufactured helicopters. This amendment expands scope to include Agusta Model AB 412 helicopters, which are license-built versions of the same aircraft. This is a modest expansion to cover equivalent aircraft from a different manufacturer."},"complexity_factors":["Very short document (under 300 words)","Only 4 defined applicability criteria (specific serial number ranges and part numbers)","Single requirement: comply with referenced manufacturer bulletins","No nested conditions or exceptions","No cross-references to other legislation beyond noting related FAA and Italian (ENAC) directives","Straightforward compliance deadline (as per manufacturer documents)"],"plain_english_summary":"This mandatory CASA Airworthiness Directive orders operators of Bell 412-series (including Agusta AB 412) helicopters with main rotor yokes having part numbers ending in -123 or -127 to follow manufacturer service bulletins to inspect/replace those yokes. A critical yoke area was found too thin (under 0.478\"), so the AD shortens the allowable service life by 500 hours to prevent metal-fatigue failure and catastrophic rotor loss."},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"Amendment 1 expands the AD's applicability to include Agusta Model AB 412 helicopters (Background). The original AD applied to Bell 412 series serial ranges and certain 412CF ranges; the amendment adds the Agusta model to the prescribed population. Mechanically, the rule imposes the same measurement, life-reduction (500 hours) and service-bulletin-based corrective actions on the newly included Agusta fleet."},"complexity_factors":["Applicability: multiple specific models and long serial-number ranges plus specific yoke part numbers (Applicability).","Measurement threshold: a precise dimensional limit (0.478\") on the flexure area drives the life reduction decision (Background).","Life-limit change: a uniform 500‑hour reduction in permitted life for affected yokes requires tracking and adjustment of time‑in‑service records (Background; Compliance).","Delegated action: required corrective/inspection work is defined by multiple external manufacturer documents (Bell ASB No.412-98-93, No.412CF-98-5; Agusta ATB No.412-74) rather than fully set out in the AD (Requirement).","Cross-jurisdictional references: the AD cites FAA AD 99-23-23 and ENAC AD 1999-179, creating potential alignment issues for international operators (Requirement/Note).","Amendment scope change: inclusion of Agusta Model AB 412 increases the population affected and requires operators to re-check applicability (Background/Amendment).","Compliance timing: an effective date (16 March 2006) fixes when operators must have actions in place, creating a near-term scheduling and maintenance burden (Compliance; effective date).","Operational impact: inspection, measurement, replacement and recordkeeping tasks fall to operators/maintenance organisations and may require parts procurement and shop time (implicit across Requirement and Compliance)."],"plain_english_summary":"Changes the service life and inspection requirement for certain Bell and Agusta Model 412 main rotor yokes. It requires operators of listed serial-numbered helicopters fitted with yoke P/N 412-010-101-123 or -127 to carry out actions in specified Bell/Agusta service bulletins and to observe a 500‑hour reduction in life where the flexure area measures less than 0.478\". Operators must comply by 16 March 2006 and bear the cost of inspections, repairs and replacements; CASA issued the directive."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-412-40-amdt-1-main-rotor-yoke","history":"/api/acts/ad-bell-412-40-amdt-1-main-rotor-yoke/history","analysis":"/api/acts/ad-bell-412-40-amdt-1-main-rotor-yoke/analysis","conflicts":"/api/acts/ad-bell-412-40-amdt-1-main-rotor-yoke/conflicts","importantCases":"/api/acts/ad-bell-412-40-amdt-1-main-rotor-yoke/important-cases","documents":"/api/acts/ad-bell-412-40-amdt-1-main-rotor-yoke/documents"}}