{"id":"F2006B02447","name":"AD/ARRIEL/16 - Gas Generator 2nd Stage Turbine Blades","slug":"ad-arriel-16-gas-generator-2nd-stage-turbine-blades","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41703,"registerId":"commonwealth-F2006B02447-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\n![](image.001.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\nTurbomeca Turbine Engines \\- Arriel Series","sortOrder":0},{"sectionNumber":"AD/ARRIEL/16 Gas Generator 2 nd Stage Tu","sectionType":"part","heading":"AD/ARRIEL/16 Gas Generator 2 nd Stage Turbine Blades 8/2002","content":"# AD/ARRIEL/16 Gas Generator 2 nd Stage Turbine Blades 8/2002\n\nApplicability: All Arriel 1B, 1D, 1D1 turboshaft engines installed in rotorcraft in single engine configuration, and incorporating modification TU 204.\n\nRequirement: Replace gas generator 2nd stage TU 204 modified blades as per: Turbomeca SB 292 72 0258 update 1 for Arriel 1B engines; or\n\nTurbomeca SB 292 72 0265 update 1 for Arriel 1D, and 1D1 engines.\n\nNote: DGAC 2002-258(A) refers.\n\nCompliance: Unless previously accomplished, prior to March 31 2003.\n\nThis Airworthiness Directive becomes effective on 8 August 2002.\n\nBackground: Incorporation of Mod TU 204 increased the blade mass and subsequently the stress on the blade root. Failure of the 2nd stage turbine blade has resulted in uncommanded in flight shutdowns.\n\n![](image.002.jpeg)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 28 June 2002\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD remains within the original safety-fix scope: it targets a specific unsafe condition caused by modification TU 204 on a defined set of engines and mandates replacement of the affected blades. It does not broaden to other components, engine types, or operational rules beyond requiring the OEM-prescribed corrective action by a set date."},"complexity_factors":["Very short instrument (single-page AD) with limited text","Clear, narrow applicability: 3 engine models (Arriel 1B, 1D, 1D1) and a single modification (TU 204)","Only two OEM service bulletins cited as the required technical instructions","One fixed compliance deadline (31 March 2003)","Minimal cross-references (a Note referring to DGAC 2002-258(A) but no layered exceptions or multiple conditional branches)"],"plain_english_summary":"**What this instrument does, in simple terms**\n\n- This is an Airworthiness Directive (a mandatory safety order) that requires replacement of certain turbine blades on specified Turbomeca Arriel turboshaft engines. (Applicability & Requirement)\n\n**Which engines and aircraft are affected**\n\n- All Turbomeca Arriel 1B, 1D and 1D1 turboshaft engines that are:  \n  - installed in rotorcraft operating in a *single-engine configuration*; and  \n  - fitted with modification TU 204.  (Applicability)\n\n**What operators must do**\n\n- Replace the gas-generator 2nd-stage turbine blades that were modified under TU 204. The replacement must be done in accordance with the Turbomeca service bulletin appropriate to the engine model:  \n  - Arriel 1B engines — Turbomeca SB 292 72 0258 update 1; or  \n  - Arriel 1D and 1D1 engines — Turbomeca SB 292 72 0265 update 1.  (Requirement)\n\n- If the replacement has not already been done, it must be completed on or before 31 March 2003. (Compliance)\n\n**Why the directive was issued**\n\n- Turbomeca’s modification TU 204 increased the mass of the 2nd-stage turbine blade and raised the stress at the blade root. Blade failures have occurred and led to uncommanded in-flight engine shutdowns. The directive aims to remove the TU 204-modified blades to prevent that unsafe condition. (Background)\n\n**Who pays and who decides**\n\n- Aircraft owners/operators pay for the replacement parts, labour and aircraft downtime. The Civil Aviation Safety Authority (CASA) delegate issued the directive and requires compliance with the specified Turbomeca service bulletins. (Applicability, Requirement)\n\n**How this works in practice and practical effects**\n\n- Safety mechanism: removing/replacing the affected blades eliminates the specific higher-stress configuration believed to cause root failures. (Background)\n- Compliance burden: costs include procurement of replacement blades, certified maintenance work, and aircraft out-of-service time until the work is done. (Requirement, Compliance)\n- Operational effect: single-engine rotorcraft using the listed Arriel variants cannot lawfully return to service after the compliance date unless the replacement has been carried out. Non-compliance means the aircraft is unairworthy under the relevant regulations. (Compliance)\n\n**Implementation and risk considerations**\n\n- Dependence on OEM instructions: the directive refers operators to two specific Turbomeca service bulletins for the technical replacement instructions. This concentrates execution risk on OEM parts availability and the clarity of those bulletins. (Requirement)\n- Timing and logistics: a hard compliance date can create short-term demand for parts and maintenance slots; operators may face supply delays or higher costs. (Compliance)\n- Enforcement: the directive is regulatory — compliance is mandatory; oversight and possible grounding follow from aviation safety enforcement mechanisms. (Applicability, Compliance)\n\n**Trade-offs and incentives**\n\n- Concentrated costs for affected operators (replacement costs and downtime) versus a safety benefit aimed at preventing rare but high-consequence in-flight shutdowns. (Background, Requirement)\n- The directive channels operators to an OEM fix (the Turbomeca SBs), which reduces operator discretion over the technical remedy but aims to standardise the corrective action. (Requirement)\n\n**Source claims vs mechanics**\n\n- The directive’s stated purpose is to correct the unsafe condition caused by TU 204 (Background). Mechanically, it does so by mandating specific blade replacement per the OEM service bulletins and by setting a final compliance date. The practical costs and implementation risks are those of any mandatory parts-replacement directive: parts availability, maintenance capacity, and aircraft downtime. (Requirement, Compliance, Background)\n\n\n"},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope. It addresses a specific unsafe condition in specific engine models with a specific modification. There is no evidence of scope creep; the directive precisely targets the blade root stress issue caused by Mod TU 204 without expanding into broader operational or maintenance requirements."},"complexity_factors":["Single, specific technical requirement (blade replacement)","Limited applicability (3 engine models, single-engine helicopters only, specific modification)","No nested exceptions or conditional logic","Only 2 defined technical references (the Service Bulletins)","Clear, fixed compliance date","Straightforward causal chain in background (modification → stress → failure → shutdown)"],"plain_english_summary":"The Civil Aviation Safety Authority has issued a mandatory safety order for helicopters with Turbomeca Arriel 1B, 1D, or 1D1 engines fitted with Mod TU 204: the modification increased turbine-blade mass, causing attachment fatigue and in-flight blade failure with engine shutdown in single‑engine helicopters.  \n\nOperators must replace the affected blades with corrected parts per Turbomeca Service Bulletins 292 72 0258 or 292 72 0265 before 31 March 2003; flying without compliance is not permitted."}},"importantCases":[],"_links":{"self":"/api/acts/ad-arriel-16-gas-generator-2nd-stage-turbine-blades","history":"/api/acts/ad-arriel-16-gas-generator-2nd-stage-turbine-blades/history","analysis":"/api/acts/ad-arriel-16-gas-generator-2nd-stage-turbine-blades/analysis","conflicts":"/api/acts/ad-arriel-16-gas-generator-2nd-stage-turbine-blades/conflicts","importantCases":"/api/acts/ad-arriel-16-gas-generator-2nd-stage-turbine-blades/important-cases","documents":"/api/acts/ad-arriel-16-gas-generator-2nd-stage-turbine-blades/documents"}}