{"id":"F2006B02255","name":"AD/AL 250/43 Amdt 3 - Second Stage Turbine Nozzle","slug":"ad-al-250-43-amdt-3-second-stage-turbine-nozzle","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41485,"registerId":"commonwealth-F2006B02255-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/43 Amdt 3 - Second Stage Turbine Nozzle","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 250/43\n\nAmdt 3\n\n  \nSecond Stage Turbine Nozzle 2/90\n\nApplicability: Allison Model 250-C28B, C28C engines fitted with P/N 6898952 second stage turbine nozzles.\n\nRequirement: Modify P/N 6898952 second stage turbine nozzles in accordance with Allison CEB- A-72-2044 Rev 4.\n\nNote: FAA AD 89-23-12 refers.\n\nCompliance: Prior to 31 March 1990. Background: This Directive has been amended to;\n\n    Delete reference to CSL 2030 which has been cancelled by the manufacturer, and\n\n    2. Require compliance with the requirements of CEB-A-72-2044 Rev 4, and\n\n    3. Make reference to FAA AD 89-23-12.\n\nThe Amendment follows advice of another P/N 6898952 nozzle failure in service. Failure of the nozzle has resulted in uncontained second stage turbine wheel failure.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The amendment changed the compliance mechanism and references compared with the earlier version. Specifically, it removed the cancelled CSL 2030 reference, required compliance with Allison CEB-A-72-2044 Rev 4 as the prescriptive modification instruction, and added an explicit reference to FAA AD 89-23-12. These changes alter which external technical documents operators must follow and therefore change the operational compliance pathway. (Background; Requirement; Note)"},"complexity_factors":["Narrow technical applicability — applies only to Allison Model 250-C28B and C28C engines fitted with P/N 6898952 nozzles (Applicability)","Mandated compliance with an external manufacturer's document (Allison CEB-A-72-2044 Rev 4) which contains the technical steps (Requirement)","Cross-reference to a related FAA AD (FAA AD 89-23-12) which operators may need to consult for context or additional requirements (Note)","Amendment history removing a cancelled document (CSL 2030) and replacing the compliance reference increases change-management complexity for operators and maintainers (Background)","Fixed compliance deadline that concentrates operational and financial impact into a defined period (Compliance)","Technical risk in the event of non-compliance (reported uncontained turbine wheel failure) creates high safety stakes despite the limited scope (Background)"],"plain_english_summary":"This directive mandates modification of Allison Model 250-C28B and 250-C28C engines fitted with second-stage turbine nozzles P/N 6898952, to be done per Allison CEB‑A‑72‑2044 Rev 4 (required before 31 March 1990). Operators/owners must arrange and pay for the work.\n\nIt was tightened after an in-service P/N 6898952 nozzle failure that led to an uncontained second-stage turbine wheel failure; the amendment removes a cancelled CSL 2030 reference and explicitly cites the related FAA AD."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope of the directive. The changes are administrative updates (removing obsolete references, updating to current manufacturer instructions) rather than expansion of the safety mandate. The core requirement — modifying the specific turbine nozzle — remains unchanged."},"complexity_factors":["Very short document (under 300 words)","Only 1 defined applicability criterion (specific engine models and part number)","Single compliance requirement with reference to external technical document","No nested conditions or exceptions","Straightforward deadline (single fixed date)","Minimal cross-referencing (only to one FAA directive and one manufacturer bulletin)"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific repairs or modifications to aircraft engines.\n\n**What it does:**\nOrders owners and operators of certain Allison 250-series helicopter engines to modify a specific part — the \"second stage turbine nozzle\" (part number 6898952) — before 31 March 1990.\n\n**Who it affects:**\nAnyone operating aircraft with **Allison Model 250-C28B or C28C engines** that have this specific nozzle installed. These are commonly used in helicopters and some fixed-wing aircraft.\n\n**Why it matters:**\nThe nozzle has been failing in service. When it fails, it can cause the second stage turbine wheel to break apart uncontrollably — sending high-speed metal fragments through the engine casing. This creates a serious risk of engine failure, fire, or damage to the aircraft.\n\n**What changed in this version (Amendment 3):**\n- Removed an outdated reference to a cancelled manufacturer bulletin (CSL 2030)\n- Updated the required fix to use the manufacturer's latest instructions (CEB-A-72-2044 Revision 4)\n- Added a reference to the equivalent US safety order (FAA AD 89-23-12)\n\nThis amendment was triggered by another reported failure of this nozzle part."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-43-amdt-3-second-stage-turbine-nozzle","history":"/api/acts/ad-al-250-43-amdt-3-second-stage-turbine-nozzle/history","analysis":"/api/acts/ad-al-250-43-amdt-3-second-stage-turbine-nozzle/analysis","conflicts":"/api/acts/ad-al-250-43-amdt-3-second-stage-turbine-nozzle/conflicts","importantCases":"/api/acts/ad-al-250-43-amdt-3-second-stage-turbine-nozzle/important-cases","documents":"/api/acts/ad-al-250-43-amdt-3-second-stage-turbine-nozzle/documents"}}