{"id":"F2006B02256","name":"AD/AL 250/45 - Power Turbine Inner and Outer Coupling Shaft - Replacement","slug":"ad-al-250-45-power-turbine-inner-and-outer-coupling-shaft-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41486,"registerId":"commonwealth-F2006B02256-current","compilationNumber":null,"startDate":"2026-04-01","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/45 - Power Turbine Inner and Outer Coupling Shaft - 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)  Allison Turbine Engines - 250 Series\n\n \n\nAD/AL 250/45 Power Turbine Inner and Outer Coupling Shaft - Replacement\n\n\n7/81\n\n \n\nApplicability: Model 250-B17B, C20B, -C28B and -C30 engines fitted with turbines of S/Nos. specified in the reference document.\n\n \n\nDocument: 1. Allison 250-C20B CEB-A-1173; or\n\n \n\n2. Allison 250-B17B CEB-A-1138; or\n\n \n\n3. Allison 250-C28B CEB-A-72-2055; or\n\n \n\n4. Allison 250-C30 CEB-A-72-3049.\n\n \n\nCompliance: Within 100 hours’ time in service after 31 July 1981.\n\n \n\nBackground: This Directive is issued to preclude a power turbine coupling failure.\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":1653},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive maintains its original narrow, technical scope. It addresses a specific mechanical defect in specific engine models and mandates a specific hardware replacement. There is no evidence of scope expansion beyond the original safety purpose of preventing power turbine coupling failure."},"complexity_factors":["Single, unambiguous compliance requirement (replace specific parts)","Minimal conditional logic - applies only to four specific engine models with identified serial numbers","No nested exceptions, penalty clauses, or complex procedural requirements","Straightforward deadline calculation based on flight hours after a fixed calendar date","Only four external document references, clearly listed as alternatives"],"plain_english_summary":"This mandatory Airworthiness Directive from the Civil Aviation Safety Authority requires owners/operators of specified Allison 250-B17B, C20B, C28B and C30 engines (per manufacturer serial lists) to replace the power turbine inner and outer coupling shafts within 100 flight hours after 31 July 1981. The replacement must follow the manufacturer’s service bulletins to prevent in‑flight coupling failure and potential catastrophic engine loss."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-45-power-turbine-inner-and-outer-coupling-shaft-replacement","history":"/api/acts/ad-al-250-45-power-turbine-inner-and-outer-coupling-shaft-replacement/history","analysis":"/api/acts/ad-al-250-45-power-turbine-inner-and-outer-coupling-shaft-replacement/analysis","conflicts":"/api/acts/ad-al-250-45-power-turbine-inner-and-outer-coupling-shaft-replacement/conflicts","importantCases":"/api/acts/ad-al-250-45-power-turbine-inner-and-outer-coupling-shaft-replacement/important-cases","documents":"/api/acts/ad-al-250-45-power-turbine-inner-and-outer-coupling-shaft-replacement/documents"}}