{"id":"F2006B02244","name":"AD/AL 250/25 Amdt 1 - Power Turbine Outer Coupling Nut - Inspection","slug":"ad-al-250-25-amdt-1-power-turbine-outer-coupling-nut-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41474,"registerId":"commonwealth-F2006B02244-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/25 Amdt 1 - Power Turbine Outer Coupling Nut - Inspection","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 250/25\n\nAmdt 1\n\n\nPower Turbine Outer Coupling Nut - Inspection 10/77\n\n \n\nApplicability: All model 250-C18, -C20, -C20B, B15G, B17 and B17B series engines fitted with power turbine outer coupling Nut P/N 6846278.\n\n \n\nDocument: Allison 250-C18, CSL-88, Rev. 3; OR 250-C20/C20B CSL-1060, Rev. 3; or 250- B15G TP CSL-25, Rev. 3; OR 250-B17/B17B TP CSL-1030, Rev. 3; OR FAA AD\n\n77-15-12, Amendment No. 39-2977.\n\n \n\nCompliance: As detailed in the requirement documents.\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":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow airworthiness directive focused on a single known defect in a specific engine part. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 200 words)","Only 1 substantive requirement: inspect a specific part","No defined terms section — uses plain technical language","No conditional logic or nested exceptions","Single cross-reference to manufacturer documents and one FAA AD","Clear applicability section limiting scope to specific engine models and part numbers"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft engines.\n\n**What it does:**\nThis directive requires owners and operators of specific Allison 250 series turbine engines to inspect a particular part called the **\"power turbine outer coupling nut\"** (part number 6846278). This nut connects components in the engine's power turbine section. The inspection is necessary because this part can develop cracks or fail, which could cause serious engine damage or failure in flight.\n\n**Who it affects:**\n- Anyone operating aircraft with **Allison 250-C18, -C20, -C20B, B15G, B17, or B17B** model engines\n- Specifically, only those engines fitted with the coupling nut part number **6846278**\n- This covers many light helicopters and small fixed-wing aircraft commonly used in Australia for charter work, training, agriculture, and emergency services\n\n**Why it matters:**\nIf this coupling nut fails, the engine can lose power catastrophically. This directive ensures the nut is checked before it reaches a dangerous condition. Compliance is **legally mandatory** — you cannot fly the aircraft until the inspection is done according to the manufacturer's instructions referenced in the document.\n\n**What you must do:**\nFollow the inspection procedures in one of these manufacturer documents (whichever applies to your engine model):\n- Allison 250-C18 CSL-88 Rev. 3\n- 250-C20/C20B CSL-1060 Rev. 3  \n- 250-B15G TP CSL-25 Rev. 3\n- 250-B17/B17B TP CSL-1030 Rev. 3\n- Or the equivalent US FAA directive 77-15-12"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"This instrument is titled as Amendment 1 to AD/AL 250/25 (Amdt 1), indicating it is an amendment to an earlier AD. The text supplied sets out the current applicability (specific Allison 250 models with power turbine outer coupling Nut P/N 6846278) and makes compliance with specified Allison service/technical publications and FAA AD 77-15-12 mandatory. The supplied document does not state how the scope or requirements differ from the original AD text, so the exact nature of the change from the prior version is not specified here. (AD title; Applicability; Document)"},"complexity_factors":["Narrow technical scope (single part number and specific engine models) (Applicability)","Dependence on multiple external documents (Allison CSL/TP publications and FAA AD) for procedural detail (Document)","AD text does not include inspection intervals, methods or corrective actions — requires cross-referencing (Compliance)","Regulatory authority and enforcement are stated but operational details are delegated to referenced documents (Header; Document)","Potential administrative burden for operators to obtain and track the required external documents and to implement their requirements (Document; Compliance)"],"plain_english_summary":"This AD (AD/AL 250/25 Amendment 1) requires inspection of power turbine outer coupling Nut P/N 6846278 on specified Allison 250-series engines, making the inspection and any corrective actions set out in the listed Allison service/technical publications and FAA AD mandatory. It affects owners/operators of those engines, who must obtain and follow the referenced documents and will bear the cost, downtime and repair obligations arising from compliance."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-25-amdt-1-power-turbine-outer-coupling-nut-inspection","history":"/api/acts/ad-al-250-25-amdt-1-power-turbine-outer-coupling-nut-inspection/history","analysis":"/api/acts/ad-al-250-25-amdt-1-power-turbine-outer-coupling-nut-inspection/analysis","conflicts":"/api/acts/ad-al-250-25-amdt-1-power-turbine-outer-coupling-nut-inspection/conflicts","importantCases":"/api/acts/ad-al-250-25-amdt-1-power-turbine-outer-coupling-nut-inspection/important-cases","documents":"/api/acts/ad-al-250-25-amdt-1-power-turbine-outer-coupling-nut-inspection/documents"}}