{"id":"F2006B07241","name":"AD/T53/12 - Fuel Regulator Main Pressure Regulator Valve Diaphragm Replacement","slug":"ad-t53-12-fuel-regulator-main-pressure-regulator-valve-diaphragm-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49111,"registerId":"commonwealth-F2006B07241-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/T53/12 - Fuel Regulator Main Pressure Regulator Valve Diaphragm Replacement","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)  AlliedSignal (Lycoming) Turbine Engines - T53 Series\n\n \n\nAD/T53/12 Fuel Regulator Main Pressure Regulator Valve\n\nDiaphragm Replacement\n\n\n1/86\n\n \n\nApplicability: All T5307, 09, 11, 13 Series and T53-L-9, -11, -13 Series engines fitted with fuel regulator main pressure regulator valve diaphragms P/N 78958 having a cure date of 1 July 1973 to 30 June 1974 (identified as 3Q73, 4Q73, 1Q74, 2Q74).\n\n \n\nDocument: 1. Lycoming Alert SB No. 0040; or\n\n \n\n2. AD/LYC-T/13. Compliance: Before 30 August 1974.\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":1829},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"Narrow technical safety directive targeting a specific manufacturing defect in identified engine components; scope remains strictly limited to the mandated replacement of the faulty diaphragms."},"complexity_factors":["Single, unambiguous compliance action (replacement of specific part)","Limited applicability clearly defined by engine model and manufacturing date codes","No conditional exceptions or nested legislative references","Only two external technical document references (manufacturer service bulletin and related AD)"],"plain_english_summary":"**What this does:** This rule requires aircraft operators to replace faulty fuel regulator diaphragms in specific Lycoming turbine engines to prevent engine failure.\n\n**Who it affects:** Owners and operators of aircraft fitted with T53 series engines (models T5307, 09, 11, 13 and T53-L-9, -11, -13) that contain fuel regulator diaphragms with part number 78958 manufactured between July 1973 and June 1974.\n\n**What you must do:** Replace the affected diaphragms (identified by date codes 3Q73, 4Q73, 1Q74, and 2Q74) before 30 August 1974, following the procedures in Lycoming Alert Service Bulletin No. 0040 or AD/LYC-T/13.\n\n**Why it matters:** The specified diaphragms were found to be defective and could fail, causing loss of engine power and potential aircraft accidents."}},"importantCases":[],"_links":{"self":"/api/acts/ad-t53-12-fuel-regulator-main-pressure-regulator-valve-diaphragm-replacement","history":"/api/acts/ad-t53-12-fuel-regulator-main-pressure-regulator-valve-diaphragm-replacement/history","analysis":"/api/acts/ad-t53-12-fuel-regulator-main-pressure-regulator-valve-diaphragm-replacement/analysis","conflicts":"/api/acts/ad-t53-12-fuel-regulator-main-pressure-regulator-valve-diaphragm-replacement/conflicts","importantCases":"/api/acts/ad-t53-12-fuel-regulator-main-pressure-regulator-valve-diaphragm-replacement/important-cases","documents":"/api/acts/ad-t53-12-fuel-regulator-main-pressure-regulator-valve-diaphragm-replacement/documents"}}