{"id":"F2006B06704","name":"AD/S-76/21 Amdt 1 - Main Gear Box Assembly - Shaft and Spur Pinion Inspection and Retirement","slug":"ad-s-76-21-amdt-1-main-gear-box-assembly-shaft-and-spur-pinion-inspection-and-retirement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114515,"registerId":"commonwealth-F2006B06704-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/S-76/21 Amdt 1 - Main Gear Box Assembly - Shaft and Spur Pinion Inspection and Retirement","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-76/21\n\nAmdt 1\n\n\nMain Gear Box Assembly - Shaft and Spur Pinion Inspection and Retirement\n\n\n3/83\n\n \n\nApplicability: All model S-76 using 76351-09000 main gear box assemblies, prior to and including - 062.\n\n \n\nDocument: Sikorsky Alert SB 76-66-16B.\n\n \n\nNote: FAA AD 82-06-51 Amendment 39-43-87 dated 5th March 1982 refers in part.\n\n \n\nCompliance: As per requirement document.\n\n \n\nBackground: Manufacturer’s Amendment “B” includes the -062 main gear box assembly incorporating the -104 shaft and spur pinions plus an additional inspection requirement.\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":4,"scope_assessment":{"changed":true,"description":"This amendment expands the directive’s coverage to include the -062 main gear box assembly and introduces an additional inspection requirement for the -104 shaft and spur pinions incorporated in that assembly. The AD now applies to all S‑76 helicopters using main gear box assembly 76351-09000 up to and including -062 and directs operators to comply with Sikorsky Alert SB 76-66-16B for the specific inspection and retirement procedures (Applicability; Background; Document)."},"complexity_factors":["Narrow technical scope keyed to a specific part number and build variant (76351-09000 up to -062) — requires accurate parts/assembly identification (Applicability).","Directive text delegates all technical detail to an external service bulletin (Sikorsky Alert SB 76-66-16B), so compliance requires consulting another document (Document; Compliance).","Cross-reference to a related FAA airworthiness directive introduces multi-jurisdictional considerations for operators subject to more than one regulator (Note).","The AD does not itself specify inspection intervals or retirement lives — interpretation and operational planning rest on the referenced requirement document (Compliance)."],"plain_english_summary":"This AD requires operators of Sikorsky S‑76 helicopters fitted with main gearbox assembly P/N 76351‑09000 (up to -062) to carry out the inspection and retirement actions set out in Sikorsky Alert SB 76‑66‑16B. It shifts technical detail to that service bulletin.\n\nAffected parties—aircraft owners, operators, and MROs—must fund and perform the inspections/replacements, causing downtime and compliance costs; accurate parts identification is essential."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a narrow, technical airworthiness directive focused on a specific mechanical component in a specific helicopter series. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (under 300 words)","Only 1 defined applicability criterion (specific gearbox part numbers)","Single cross-reference to manufacturer service bulletin and FAA AD","No conditional logic or nested exceptions","Straightforward compliance requirement ('as per requirement document')","Minimal legislative drafting — essentially a regulatory notice adopting external technical standard"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order — issued by Australia's Civil Aviation Safety Authority (CASA) for certain Sikorsky S-76 helicopters.\n\n**What it does:**\n- Requires inspection and eventual replacement (\"retirement\") of specific parts in the main gearbox — namely the shaft and spur pinion gears.\n- Applies to all S-76 helicopter models using main gearbox assemblies numbered 76351-09000 up to and including the -062 variant.\n\n**Why it matters:**\n- The main gearbox is critical — if it fails, the helicopter loses power to the rotors. This AD prevents catastrophic mechanical failures by catching wear or damage before it becomes dangerous.\n- The directive was updated (Amendment 1) to include an additional gearbox variant (-062) and extra inspection requirements after the manufacturer (Sikorsky) revised their service bulletin.\n\n**Who must comply:**\n- Owners and operators of affected S-76 helicopters must follow the inspection and replacement schedule set out in Sikorsky's Alert Service Bulletin 76-66-16B.\n\n**Key point:** This isn't optional — compliance is legally mandatory for airworthiness certification in Australia."}},"importantCases":[],"_links":{"self":"/api/acts/ad-s-76-21-amdt-1-main-gear-box-assembly-shaft-and-spur-pinion-inspection-and-retirement","history":"/api/acts/ad-s-76-21-amdt-1-main-gear-box-assembly-shaft-and-spur-pinion-inspection-and-retirement/history","analysis":"/api/acts/ad-s-76-21-amdt-1-main-gear-box-assembly-shaft-and-spur-pinion-inspection-and-retirement/analysis","conflicts":"/api/acts/ad-s-76-21-amdt-1-main-gear-box-assembly-shaft-and-spur-pinion-inspection-and-retirement/conflicts","importantCases":"/api/acts/ad-s-76-21-amdt-1-main-gear-box-assembly-shaft-and-spur-pinion-inspection-and-retirement/important-cases","documents":"/api/acts/ad-s-76-21-amdt-1-main-gear-box-assembly-shaft-and-spur-pinion-inspection-and-retirement/documents"}}