{"id":"F2006B06721","name":"AD/S-76/40 - Power Train Tail Drive Shaft Bearing Support Assembly","slug":"ad-s-76-40-power-train-tail-drive-shaft-bearing-support-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114542,"registerId":"commonwealth-F2006B06721-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/S-76/40 - Power Train Tail Drive Shaft Bearing Support Assembly","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)  Sikorsky S-76 Series Helicopters\n\n \n\nAD/S-76/40 Power Train Tail Drive Shaft Bearing Support Assembly\n\n\n9/85\n\nTX\n\n \n\nApplicability: All model S76 which have bearing support assembly bearings manufactured by MRC installed.\n\n \n\nRequirement: Action in accordance with Sikorsky Alert Service Bulletin No. 76- 66-20. Compliance:              Before further flight after 31 July 1985.\n\nBackground: It has been determined that some bearings manufactured by MRC may have been assembled without grease.\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\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive's text is consistent with its stated purpose: it targets S-76 helicopters with MRC-manufactured bearing support assembly bearings and requires the actions set out in Sikorsky Alert Service Bulletin No. 76-66-20 to address bearings that may have been assembled without grease. There is no indication in the provided text that the scope was expanded or narrowed from that original stated intent."},"complexity_factors":["Narrow technical scope: applies only to Sikorsky S-76 helicopters with MRC-manufactured bearing support assembly bearings (\"Applicability...\")","Single mandatory remedial action tied to a specific manufacturer service bulletin (\"Requirement: Action in accordance with Sikorsky Alert Service Bulletin No. 76-66-20.\")","Immediate compliance deadline tied to next flight after a fixed date (\"Compliance: Before further flight after 31 July 1985.\"), creating operational urgency but not regulatory ambiguity","Technical nature of the remedy (inspection/greasing/repair/replacement) requires qualified maintenance personnel and parts, introducing logistical considerations","No alternative means of compliance stated in the text—compliance depends on the contents of the referenced service bulletin"],"plain_english_summary":"This directive requires Sikorsky S‑76 helicopters with MRC‑manufactured tail drive shaft bearing support bearings to be inspected and corrected per Sikorsky Alert Service Bulletin No. 76‑66‑20 before further flight after 31 July 1985, because some bearings may have been assembled without grease. It affects owners/operators of fitted S‑76s, who must arrange and pay for the work performed by authorised maintenance organisations."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific manufacturing defect. It has not expanded beyond its original purpose of grounding and repairing affected helicopters with defective bearings."},"complexity_factors":["Very short document (approximately 150 words)","Only one defined applicability criterion (MRC-manufactured bearings)","Single requirement referencing an external technical document (Sikorsky Alert Service Bulletin)","No nested exceptions or conditional logic","No cross-references to other legislation beyond the enabling Civil Aviation Regulations 1998","Clear, unambiguous compliance deadline (before further flight after 31 July 1985)"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nOrders owners and operators of certain Sikorsky S-76 helicopters to inspect and fix a specific mechanical problem with the tail rotor drive shaft bearing support assembly.\n\n**Who it affects:**\nAnyone who owns or operates Sikorsky S-76 helicopters that have bearing support assemblies made by a company called MRC (Marathon Roller Corporation).\n\n**The problem:**\nSome MRC bearings were assembled without grease. This is dangerous because bearings need lubrication to function properly — without grease, they could seize up or fail, potentially causing loss of tail rotor control and a crash.\n\n**What must be done:**\nOperators must follow the instructions in **Sikorsky Alert Service Bulletin No. 76-66-20** (a technical repair notice from the manufacturer) before flying the helicopter again after 31 July 1985.\n\n**Why it matters:**\nThis is a flight safety issue. The directive is mandatory — you cannot legally fly the affected helicopters until the repair is done. It prevents catastrophic mechanical failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-s-76-40-power-train-tail-drive-shaft-bearing-support-assembly","history":"/api/acts/ad-s-76-40-power-train-tail-drive-shaft-bearing-support-assembly/history","analysis":"/api/acts/ad-s-76-40-power-train-tail-drive-shaft-bearing-support-assembly/analysis","conflicts":"/api/acts/ad-s-76-40-power-train-tail-drive-shaft-bearing-support-assembly/conflicts","importantCases":"/api/acts/ad-s-76-40-power-train-tail-drive-shaft-bearing-support-assembly/important-cases","documents":"/api/acts/ad-s-76-40-power-train-tail-drive-shaft-bearing-support-assembly/documents"}}