{"id":"F2006B02234","name":"AD/AL 250/11 Amdt 3 - Engine Improvement - Introduction of Blue Ribbon Modifications","slug":"ad-al-250-11-amdt-3-engine-improvement-introduction-of-blue-ribbon-modifications","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41464,"registerId":"commonwealth-F2006B02234-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/11 Amdt 3 - Engine Improvement - Introduction of Blue Ribbon Modifications","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nAllison Turbine Engines \\- 250 Series\n\nAD/AL 250/11\n\nAmdt 3\n\n  \n\nEngine Improvement \\- Introduction of “Blue Ribbon” Modifications\n\n  \n4/71\n\nApplicability: All 250-C18 series.\n\nDocument: 1. Allison Commercial Engine Bulletins numbered 250 CEB 57, 58, 59 Rev. 1, 61,\n\n62, 63, 65, 66, 67, 68, 69 (or 98) 70, 72, 73, 74, (or 105), 75 (or 104), 76, 77, 103,\n\n79, 80, 81, 85 and 89; or\n\n2. FAA AD 69-26-3.\n\nCompliance: 1. At next overhaul after 29 May 1970 but not later than 750 hours’ time in service since last overhaul or since new if never overhauled, modify the engine in accordance with the applicable Allison CEBs listed in this AD.\n\n2. At next overhaul after 29 May 1970 but not later than 1125 hours’ time in service since last overhaul or since new if never overhauled, modify the power and accessories gearbox in accordance with the applicable Allison CEBs listed in this AD.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument, as provided, applies specifically to \"All 250-C18 series\" and mandates modifications via the listed Allison CEBs or FAA AD (Applicability; Document; Compliance). The text does not indicate an expansion or narrowing of the affected population beyond that stated applicability, so there is no evidence in this document that the scope has changed from its stated coverage."},"complexity_factors":["Limited technical scope (applies to a single engine family: \"All 250-C18 series\"). (Applicability)","Mandates work by reference to many external technical documents (numerous Allison CEB numbers or FAA AD 69-26-3), which requires locating and following those documents. (Document)","Two distinct compliance deadlines tied to service hours (750 hours for engine mods; 1125 hours for gearbox mods) that require tracking time-in-service and overhaul scheduling. (Compliance)","Practical implementation issues: need for parts, approved overhaul facilities, and potential aircraft downtime (implied by the requirement to perform modifications at overhaul). (Compliance)","Minimal regulatory discretion—mandatory obligations leave little choice about whether to comply, only how and when within the specified windows. (Compliance)"],"plain_english_summary":"This directive mandates “Blue Ribbon” physical modifications to Allison 250‑C18 turbine engines and their power/accessory gearboxes, requiring work at the next overhaul after 29 May 1970 and by fixed service-hour limits (engines by 750 TIS, gearboxes by 1,125 TIS). Operators, owners and maintenance organisations must follow the listed Allison Commercial Engine Bulletins (or FAA AD 69‑26‑3) to comply.\n\nIt matters because it creates mandatory overhaul work, parts, labour and downtime costs and limits discretion to scheduling and choosing an approved provider."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused specifically on introducing the 'Blue Ribbon' modifications to the Allison 250-C18 engine series. It has not expanded beyond its original purpose of mandating these specific engine improvements."},"complexity_factors":["Short, single-purpose directive with clear applicability (one engine series)","Only two compliance deadlines with straightforward hour-counting mechanics","References external documents (Allison CEBs and FAA AD) but does not reproduce their content","No defined terms section or complex conditional logic","Simple structure: applicability, document references, compliance requirements"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) that mandates safety modifications to a specific type of aircraft engine.\n\n**What it does:**\n- Requires owners and operators of **Allison 250-C18 series turbine engines** to install a package of improvements known as **\"Blue Ribbon Modifications\"**\n- These modifications are detailed in specific **Allison Commercial Engine Bulletins (CEBs)** — essentially manufacturer service instructions that improve engine reliability and safety\n\n**Who it affects:**\n- Anyone operating aircraft with **Allison 250-C18 series engines** (commonly used in helicopters and light aircraft)\n- Maintenance organisations servicing these engines\n\n**The requirements:**\n- **Engine modifications:** Must be completed at the next engine overhaul after 29 May 1970, but **no later than 750 flight hours** since the last overhaul (or since new if never overhauled)\n- **Gearbox modifications:** Must be completed at the next overhaul after 29 May 1970, but **no later than 1,125 flight hours** since the last overhaul (or since new)\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety orders. Non-compliance means the aircraft cannot legally fly. This particular AD addresses known reliability issues in these engines by mandating a comprehensive upgrade package developed by the manufacturer."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-11-amdt-3-engine-improvement-introduction-of-blue-ribbon-modifications","history":"/api/acts/ad-al-250-11-amdt-3-engine-improvement-introduction-of-blue-ribbon-modifications/history","analysis":"/api/acts/ad-al-250-11-amdt-3-engine-improvement-introduction-of-blue-ribbon-modifications/analysis","conflicts":"/api/acts/ad-al-250-11-amdt-3-engine-improvement-introduction-of-blue-ribbon-modifications/conflicts","importantCases":"/api/acts/ad-al-250-11-amdt-3-engine-improvement-introduction-of-blue-ribbon-modifications/important-cases","documents":"/api/acts/ad-al-250-11-amdt-3-engine-improvement-introduction-of-blue-ribbon-modifications/documents"}}