{"id":"F2006B06543","name":"AD/RB211/12 - N3 Governor with Approved Wear Resistance","slug":"ad-rb211-12-n3-governor-with-approved-wear-resistance","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48239,"registerId":"commonwealth-F2006B06543-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/RB211/12 - N3 Governor with Approved Wear Resistance","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 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Rolls Royce Turbine Engines - RB211 Series\n\n \n\nAD/RB211/12 N3 Governor with Approved Wear Resistance 9/90\n\nApplicability: RB211-524G2-19, -524G2-19/11, -524G2-19/15, -524G3-19, -524G3-19/15.\n\nEngines prior to serial no 13118.\n\n \n\nRequirement: Action in accordance with Rolls Royce PLC Service Bulletin RB 211-73-8763 Rev 2. Compliance:               Prior to 6 October 1990.\n\nBackground: In the pump and governor the N3 governor is prone to excessive, premature wear, due to frettage. In extreme circumstances the governing function can be rendered inoperative.\n\n \n\nThe changes introduced by this Service Bulletin have been shown to alleviate the wear problem.\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":3,"scope_assessment":{"changed":false,"description":"The instrument sets a clear, specific scope: particular RB211-524G2 and -524G3 engine variants with serial numbers prior to 13118. The text contains no information indicating the scope has been altered from an earlier or original intent; it presents a single directive with applicability, required action and a compliance deadline. (Applicability; Requirement; Compliance)"},"complexity_factors":["Limited and clear applicability (specific engine models and serial number cut‑off) reduces scope complexity (Applicability).","Mandated single method of compliance (manufacturer Service Bulletin) concentrates technical specification but simplifies compliance choices (Requirement).","Fixed compliance deadline creates time pressure and logistical complexity for scheduling maintenance (Compliance).","Identification of affected units requires checking serial numbers, which is an administrative task for operators (Applicability).","Potential need for manufacturer parts, tooling or approvals can complicate procurement and MRO contracting but is not detailed in the instrument (Requirement)."],"plain_english_summary":"This airworthiness directive requires specified Rolls‑Royce RB211‑524G2 and ‑524G3 engines (serials before 13118) to be modified or repaired per Service Bulletin RB 211‑73‑8763 Rev 2 by 6 Oct 1990 to address premature N3 governor wear. Owners/operators must fund and schedule the work; the regulator mandates the method via the manufacturer’s bulletin. The expected benefit is reduced governor wear; trade‑offs are maintenance costs, downtime, and reliance on manufacturer parts/procedures."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific mechanical defect in specific engine models. It has not expanded beyond its original purpose of mandating a hardware modification to prevent governor failure."},"complexity_factors":["Very short document (under 200 words)","Only 4 defined engine models in applicability section","Single, unambiguous compliance requirement (follow the Service Bulletin)","No nested exceptions or conditional logic","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1988","Clear, fixed deadline with no alternative compliance methods"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance action on aircraft engines.\n\n**What it does:** It orders owners and operators of certain Rolls-Royce RB211 jet engines to modify or replace the **N3 governor** — a component that controls engine speed — with a version that has better wear resistance.\n\n**Who it affects:** Anyone operating specific models of Rolls-Royce RB211-524G2 and RB211-524G3 engines with serial numbers below 13118. These are typically used on wide-body aircraft like the Boeing 747.\n\n**Why it matters:** The original N3 governor was wearing out too quickly due to **frettage** (a type of surface damage caused by tiny repeated movements between metal parts). In worst cases, this wear could cause the governor to fail completely, potentially leading to loss of engine control. The directive mandates a fix proven to solve this problem.\n\n**The deadline:** The work had to be completed before **6 October 1990**.\n\n**How to comply:** Follow the instructions in Rolls-Royce Service Bulletin RB 211-73-8763 Revision 2."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rb211-12-n3-governor-with-approved-wear-resistance","history":"/api/acts/ad-rb211-12-n3-governor-with-approved-wear-resistance/history","analysis":"/api/acts/ad-rb211-12-n3-governor-with-approved-wear-resistance/analysis","conflicts":"/api/acts/ad-rb211-12-n3-governor-with-approved-wear-resistance/conflicts","importantCases":"/api/acts/ad-rb211-12-n3-governor-with-approved-wear-resistance/important-cases","documents":"/api/acts/ad-rb211-12-n3-governor-with-approved-wear-resistance/documents"}}