{"id":"F2006B06727","name":"AD/S-76/48 - Main Gearbox Lower Housing Jet Port Liners","slug":"ad-s-76-48-main-gearbox-lower-housing-jet-port-liners","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114553,"registerId":"commonwealth-F2006B06727-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/S-76/48 - Main Gearbox Lower Housing Jet Port Liners","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-76/48 Main Gearbox Lower Housing Jet Port Liners 13/87\n\nDM\n\nApplicability: All model S-76A and S-76B helicopters fitted with a main gearbox with S/No as listed in Table 1 of the Requirement document.\n\nRequirement: Action in accordance with Sikorsky Alert Service Bulletin No 76-66-11. Compliance:               Within 50 hours time in service after 15 October 1987, inspect in accordance with\n\nSection 2 of the Requirement document.\n\n \n\nBackground: A gearbox returned for overhaul due to lower than normal oil pressure was found to have a liner which had moved in one of the oil pressure jet ports. The gearboxes listed in Table 1 of the SB require inspection to ensure all magnesium liners are correctly pinned in place.\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":2031},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive maintains its original narrow technical scope addressing a specific mechanical defect in S-76 main gearbox oil systems. It has not expanded beyond the original safety concern regarding jet port liner retention in specified gearbox serial numbers."},"complexity_factors":["Single, discrete mechanical inspection requirement with no conditional branches","Minimal cross-referencing (refers to one external technical document for serial numbers and detailed procedures)","Specific compliance trigger (50 hours 'time in service' rather than ambiguous calendar conditions)","Narrow applicability limited to specific aircraft models and component serial numbers","No defined terms section or interpretive provisions"],"plain_english_summary":"This **Airworthiness Directive** is a mandatory safety order for certain Sikorsky S-76 helicopters. It requires a one-time inspection of the main gearbox to prevent catastrophic failure.\n\n**The Problem:** Inside the gearbox, small metal liners sit in the oil pressure jet ports. If these liners shift position (as happened in one incident), oil pressure drops, which can destroy the gearbox and potentially cause the helicopter to crash.\n\n**Who Must Act:** Owners of S-76A and S-76B helicopters with specific main gearbox serial numbers listed in Sikorsky Alert Service Bulletin 76-66-11.\n\n**What You Must Do:** Within 50 hours of flying time after 15 October 1987, inspect the gearbox to ensure all magnesium liners are properly pinned in place, following the procedures in the Sikorsky service bulletin.\n\n**Why It Matters:** This prevents in-flight gearbox failure caused by loose liners blocking oil flow—a defect already found in one gearbox returned for overhaul."}},"importantCases":[],"_links":{"self":"/api/acts/ad-s-76-48-main-gearbox-lower-housing-jet-port-liners","history":"/api/acts/ad-s-76-48-main-gearbox-lower-housing-jet-port-liners/history","analysis":"/api/acts/ad-s-76-48-main-gearbox-lower-housing-jet-port-liners/analysis","conflicts":"/api/acts/ad-s-76-48-main-gearbox-lower-housing-jet-port-liners/conflicts","importantCases":"/api/acts/ad-s-76-48-main-gearbox-lower-housing-jet-port-liners/important-cases","documents":"/api/acts/ad-s-76-48-main-gearbox-lower-housing-jet-port-liners/documents"}}