{"id":"F2006B06730","name":"AD/S-76/54 - Main Gearbox Tail Takeoff Flange Locknut","slug":"ad-s-76-54-main-gearbox-tail-takeoff-flange-locknut","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114556,"registerId":"commonwealth-F2006B06730-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/S-76/54 - Main Gearbox Tail Takeoff Flange Locknut","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-76/54 Main Gearbox Tail Takeoff Flange Locknut 7/89\n\nApplicability: All S-76A helicopters fitted with P/N 76351-09500 series main gearboxes.\n\n \n\nAll S-76B helicopters fitted with P/N 76351-09600 series main gearbox up to and including S/N A231-00038.\n\n \n\nRequirement: Action in accordance with Sikorsky Alert Service Bulletin 76-66-23. Compliance: By 31 August 1989.\n\nBackground: Due to torque loss of the tail takeoff flange locknut, specific tests to detect this torque loss are required.\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":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1184},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive maintains a narrow, targeted scope addressing a specific mechanical defect in identified helicopter models, consistent with the standard purpose of airworthiness directives."},"complexity_factors":["Single, discrete mechanical component identified (tail takeoff flange locknut)","Clear applicability criteria using specific part and serial numbers","Single compliance action: follow referenced service bulletin","Fixed, unambiguous compliance deadline","No exceptions, conditional clauses, or nested provisions"],"plain_english_summary":"**What this requires:**\nOwners and operators of specific Sikorsky S-76 helicopters must inspect the **locknut** (a fastening device) on the **main gearbox tail takeoff flange** (the connection point between the main gearbox and the tail rotor drive shaft).\n\n**Why it matters:**\nThe locknut can lose its **torque** (tightness/grip), which could cause the tail rotor to fail in flight—a catastrophic safety risk.\n\n**Who is affected:**\n- **S-76A models:** All helicopters fitted with main gearbox part number 76351-09500 series\n- **S-76B models:** Helicopters with main gearbox part number 76351-09600 series up to serial number A231-00038\n\n**What must be done:**\nOperators must follow the specific inspection and testing procedures outlined in **Sikorsky Alert Service Bulletin 76-66-23** and complete the work by **31 August 1989**."}},"importantCases":[],"_links":{"self":"/api/acts/ad-s-76-54-main-gearbox-tail-takeoff-flange-locknut","history":"/api/acts/ad-s-76-54-main-gearbox-tail-takeoff-flange-locknut/history","analysis":"/api/acts/ad-s-76-54-main-gearbox-tail-takeoff-flange-locknut/analysis","conflicts":"/api/acts/ad-s-76-54-main-gearbox-tail-takeoff-flange-locknut/conflicts","importantCases":"/api/acts/ad-s-76-54-main-gearbox-tail-takeoff-flange-locknut/important-cases","documents":"/api/acts/ad-s-76-54-main-gearbox-tail-takeoff-flange-locknut/documents"}}