{"id":"F2006B02289","name":"AD/AL 250/8 Amdt 1 - Helical Power Train Drive Gear Internal Spline Inspection","slug":"ad-al-250-8-amdt-1-helical-power-train-drive-gear-internal-spline-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41519,"registerId":"commonwealth-F2006B02289-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/8 Amdt 1 - Helical Power Train Drive Gear Internal Spline 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 250/8\n\nAmdt 1\n\n\nHelical Power Train Drive Gear Internal Spline Inspection\n\n\n2/71\n\n \n\nApplicability: All 250-C18 series non Blue Ribbon gearboxes and all Blue Ribbon gearboxes used with non Blue Ribbon turbines.\n\n \n\nDocument: Allison 250 CSL - 35 Rev. 1.\n\n \n\nCompliance: Between 700 and 775 hours’ time in service since new or last overhaul after 26 February 1961.\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":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a narrow, targeted safety directive focused on a specific mechanical defect in specific engine models. It has not expanded beyond its original purpose of mandating inspection of a known wear-prone component in Allison 250-C18 series engines."},"complexity_factors":["Single, specific mechanical component targeted (helical power train drive gear internal spline)","Narrow applicability limited to specific engine series and gearbox configurations (250-C18 series with specific Blue Ribbon/non-Blue Ribbon combinations)","Simple compliance window: fixed hour range (700-775 hours TIS) with single date condition (after 26 February 1961)","No nested exceptions, conditional logic, or cross-references to other legislation","Single referenced technical document (Allison 250 CSL-35 Rev. 1)","Extremely short length (approximately 100 words of substantive content)"],"plain_english_summary":"This is an **Airworthiness Directive** — 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:**\nThis directive orders inspections of the **helical power train drive gear internal spline** — a critical component inside Allison 250 series turbine engines. The \"internal spline\" is a grooved connection that transfers power between rotating parts; if it fails, the engine could lose power or fail completely.\n\n**Who it affects:**\n- Owners and operators of aircraft using **Allison 250-C18 series engines** with **non-Blue Ribbon gearboxes**\n- Aircraft using **Blue Ribbon gearboxes paired with non-Blue Ribbon turbines**\n\n(\"Blue Ribbon\" refers to a specific factory modification standard for these engines — think of it as a \"newer improved version\" label.)\n\n**What must be done:**\nEngine gearboxes must be inspected **between 700 and 775 flight hours** since the engine was new or last overhauled — but **only if** that overhaul happened after 26 February 1961.\n\n**Why it matters:**\nThis directive prevents catastrophic engine failures caused by wear or damage to the internal spline connection. Compliance is **legally mandatory** — flying without completing this inspection violates civil aviation safety regulations and could ground the aircraft or expose the operator to penalties.\n\n**Key document reference:**\nOperators must follow the procedure in **Allison 250 CSL-35 Revision 1** (the manufacturer's service bulletin) when performing the inspection."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The instrument is titled as Amendment 1 (\"Amdt 1\"), indicating it modifies a prior directive. The text provided sets the applicability, references the Allison procedural document, and specifies the 700–775 hour inspection window, but it does not state what the earlier version required or how the scope was altered. Based solely on this text, the instrument amends an earlier AD, but the specific changes from the original are not contained in the supplied document."},"complexity_factors":["Narrow technical focus: single component (helical power train drive gear internal spline) limits conceptual complexity.","Fixed, short compliance window (700–775 hours) requires precise service-hour tracking.","Reliance on an external referenced document (Allison 250 CSL - 35 Rev. 1) for the inspection procedure shifts procedural detail outside the directive.","Applicability language distinguishes between \"non Blue Ribbon\" and \"Blue Ribbon used with non Blue Ribbon turbines,\" which requires operators to verify gearbox/turbine configurations.","Vintage compliance date language (\"after 26 February 1961\") may raise practical issues for older equipment records and parts/maintenance availability, despite not increasing legal complexity."],"plain_english_summary":"This AD mandates a one-time inspection of the internal splines on the helical power train drive gear for specified Allison 250 turbine-engine gearboxes, using the referenced Allison 250 CSL - 35 Rev. 1 procedure.  \n\nIt applies to owners/operators of the named non‑Blue Ribbon and applicable Blue Ribbon gearboxes, must be done at 700–775 hours since new or last overhaul, and is the operator’s responsibility (scheduling, cost, and corrective actions) to reduce risk of in‑service gearbox failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-8-amdt-1-helical-power-train-drive-gear-internal-spline-inspection","history":"/api/acts/ad-al-250-8-amdt-1-helical-power-train-drive-gear-internal-spline-inspection/history","analysis":"/api/acts/ad-al-250-8-amdt-1-helical-power-train-drive-gear-internal-spline-inspection/analysis","conflicts":"/api/acts/ad-al-250-8-amdt-1-helical-power-train-drive-gear-internal-spline-inspection/conflicts","importantCases":"/api/acts/ad-al-250-8-amdt-1-helical-power-train-drive-gear-internal-spline-inspection/important-cases","documents":"/api/acts/ad-al-250-8-amdt-1-helical-power-train-drive-gear-internal-spline-inspection/documents"}}