{"id":"F2007L04507","name":"AD/BELL 427/8 - Vertical Fin Attachment","slug":"ad-bell-427-8-vertical-fin-attachment","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":70954,"registerId":"commonwealth-F2007L04507-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Bell Helicopter Textron 427 Series Helic","sectionType":"division","heading":"Bell Helicopter Textron 427 Series Helicopters","content":"### Bell Helicopter Textron 427 Series Helicopters\n\n| AD/BELL 427/8 | Vertical Fin Attachment | 13/2007 |\n| ------------- | ----------------------- | ------- |\n\n| Applicability: | BHTC Model 427 helicopters, serial numbers 56001 through 56057, 58001 and 58002.                                                                                                                                                                                                            |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Inspect the area of the vertical fin to tail rotor gearbox attachment and install a new hardware, in accordance with BHTC Alert Service Bulletin 427-06-15 original issue, dated 13 November 2006, or later Transport Canada approved revision.Note: Transport Canada AD CF-2007-22 refers. |\n| Compliance:    | Before 31 December 2007, unless already accomplished.                                                                                                                                                                                                                                       |\n|                | This Airworthiness Directive becomes effective on 20 December 2007.                                                                                                                                                                                                                         |\n| Background:    | The manufacturer has determined that the existing hardware connecting the vertical fin to the tail rotor gearbox requires upgrading, in order to ensure vertical fin security.                                                                                                              |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n7 November 2007","sortOrder":0},{"sectionNumber":"AD/BELL 427/8","sectionType":"part","heading":"AD/BELL 427/8","content":"## AD/BELL 427/8","sortOrder":1},{"sectionNumber":"Vertical Fin Attachment","sectionType":"part","heading":"Vertical Fin Attachment","content":"## Vertical Fin Attachment","sortOrder":2},{"sectionNumber":"13/2007","sectionType":"part","heading":"13/2007","content":"## 13/2007","sortOrder":3}],"analysis":{"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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive targeting a specific mechanical defect in a specific aircraft model. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 2 defined applicability criteria (specific serial number ranges)","Single, unambiguous compliance requirement with clear external reference","No nested exceptions or conditional logic — one deadline with one exemption (already accomplished)","No cross-references to other legislation beyond a single note about the Canadian equivalent AD","Straightforward temporal compliance (calendar date deadline)"],"plain_english_summary":"This AD mandates owners/operators of Bell 427 helicopters (S/N 56001–56057, 58001–58002) to inspect the vertical fin and replace the hardware attaching it to the tail rotor gearbox per Bell Alert Service Bulletin 427-06-15 (13 Nov 2006). It responds to inadequate bolts that could allow fin separation and catastrophic loss of control. Compliance is required before 31 Dec 2007; the AD is effective 20 Dec 2007."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Scope aligns with the manufacturer's stated need to upgrade the vertical fin attachment on the listed Bell 427 serial numbers. The AD confines action to those serial numbers and to work performed per the specified service bulletin or later Transport Canada‑approved revisions, without expanding applicability beyond that identified set (Applicability and Requirement entries)."},"complexity_factors":["Technical hardware upgrade: requires physical inspection and installation of new attachment hardware (Requirement entry).","Reliance on an external technical document: work must follow Bell Alert Service Bulletin 427‑06‑15 or a later Transport Canada‑approved revision (Requirement entry).","Narrow applicability: applies only to specific serial-numbered helicopters (Applicability entry), requiring operators to check serial records.","Fixed compliance timeline: a clear compliance deadline (by 31 December 2007) and an effective date (20 December 2007) create scheduling pressure (Compliance entry).","Cross-jurisdictional reference: references Transport Canada AD CF‑2007‑22, creating potential coordination for approved revisions (Requirement entry).","Operational impact: noncompliance may ground affected aircraft until work is done; owners/operators bear cost and logistics (Compliance & Background entries)."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of specified Bell 427 helicopters (serial numbers 56001–56057, 58001–58002) to inspect the vertical fin to tail rotor gearbox attachment and fit new attachment hardware following Bell Alert Service Bulletin 427‑06‑15 or a later Transport Canada‑approved revision. Compliance must be done by 31 December 2007; the AD is effective 20 December 2007. Operators must arrange and fund the inspection and hardware installation."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-427-8-vertical-fin-attachment","history":"/api/acts/ad-bell-427-8-vertical-fin-attachment/history","analysis":"/api/acts/ad-bell-427-8-vertical-fin-attachment/analysis","conflicts":"/api/acts/ad-bell-427-8-vertical-fin-attachment/conflicts","importantCases":"/api/acts/ad-bell-427-8-vertical-fin-attachment/important-cases","documents":"/api/acts/ad-bell-427-8-vertical-fin-attachment/documents"}}