{"id":"F2006B04655","name":"AD/BELL 412/20 - Bolts P/N AN4-5A - Pylon Support","slug":"ad-bell-412-20-bolts-p-n-an4-5a-pylon-support","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44407,"registerId":"commonwealth-F2006B04655-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 412/20 - Bolts P/N AN4-5A - Pylon Support","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\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)  Bell Helicopter Textron 412 Series Helicopters\n\n \n\nAD/BELL 412/20 Bolts P/N AN4-5A - Pylon Support 11/88\n\nApplicability: All model 412 helicopters S/N 33001 through 33171. Requirement:  Action in accordance with Bell Helicopter Alert SB 412-88-38.\n\nCompliance: At the next scheduled inspection for Maintenance Release after 3 November 1988.\n\n \n\nBackground:  It has been determined that some model 412 helicopters were delivered with 8 bolts missing from the pylon support installation.\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\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1511},"content_quality":"ok","complexity_score":1,"rejection_reason":"","scope_assessment":{"changed":false,"description":"This directive remains narrowly focused on its original purpose: correcting a specific manufacturing defect (missing pylon support bolts) on identified aircraft. There is no evidence of scope creep or expansion beyond this specific safety issue."},"complexity_factors":["Document is only 4 short paragraphs long","Single, unambiguous compliance action (inspect and install per service bulletin)","Applicability defined by simple serial number range with no exceptions","No defined terms, interpretation clauses, or cross-references to other legislation","Incorporation by reference to only one external technical document (the Service Bulletin)"],"plain_english_summary":"**What this is:** An Airworthiness Directive (a legally binding safety order) requiring operators to fix a manufacturing defect on specific Bell 412 helicopters.\n\n**Who it affects:** Owners and operators of Bell 412 helicopters with serial numbers 33001 through 33171.\n\n**What you must do:**\n*   Check the **pylon support** (the structural frame connecting the rotor system to the helicopter body) for missing bolts\n*   Install any missing bolts according to the manufacturer's instructions in **Bell Alert Service Bulletin 412-88-38**\n*   Complete this work by the next scheduled maintenance inspection after 3 November 1988\n\n**Why it matters:** Some helicopters were delivered from the factory missing 8 critical bolts from the pylon support. Missing structural bolts can lead to catastrophic failure of the rotor assembly during flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-412-20-bolts-p-n-an4-5a-pylon-support","history":"/api/acts/ad-bell-412-20-bolts-p-n-an4-5a-pylon-support/history","analysis":"/api/acts/ad-bell-412-20-bolts-p-n-an4-5a-pylon-support/analysis","conflicts":"/api/acts/ad-bell-412-20-bolts-p-n-an4-5a-pylon-support/conflicts","importantCases":"/api/acts/ad-bell-412-20-bolts-p-n-an4-5a-pylon-support/important-cases","documents":"/api/acts/ad-bell-412-20-bolts-p-n-an4-5a-pylon-support/documents"}}