{"id":"F2005L03046","name":"AD/ARRIEL/21 - Free Turbine Containment Shield","slug":"ad-arriel-21-free-turbine-containment-shield","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":37954,"registerId":"commonwealth-F2005L03046-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Turbomeca Turbine Engines - Arriel Serie","sectionType":"division","heading":"Turbomeca Turbine Engines - Arriel Series","content":"### Turbomeca Turbine Engines - Arriel Series\n\n| AD/ARRIEL/21 | Free Turbine Containment Shield | 12/2005 DM |\n| ------------ | ------------------------------- | ---------- |\n\n| Applicability: | Turbomeca ARRIEL 2B and 2B1 engines, pre-mod TU 22.Note 1: These engines are installed in but not limited to AS 350 B3 and EC 130 helicopters.                                                                                                                                                                                                                                                                                                                                                   |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | 1. Carry out a visual inspection of the free turbine shield in accordance with paragraph 2 of TURBOMECA Mandatory Service Bulletin (MSB) No 292 72 2821 dated 27 June 2005 or later DGAC approved revisions.2. Remove free turbine shield from service, if the length or position of the crack(s) exceed(s) the criteria laid down in paragraph 2 of MSB No. 292 72 2821 or later DGAC approved revisions.Note 2: DGAC AD F-2005-162 EASA Approval No. 2005-6251 dated 20 September 2005 refers. |\n| Compliance:    | 1. Within 10 operating hours after the effective date of this directive, thereafter at a frequency dependent on the results of the inspection, as specified in paragraph 2 of MSB No. 292 72 2821 or later DGAC approved revisions.Note 3: The inspection interval is based on the results of each ongoing inspection.2. Before further flight.                                                                                                                                                  |\n|                | This Airworthiness Directive becomes effective on 12 October 2005.                                                                                                                                                                                                                                                                                                                                                                                                                               |\n| Background:    | On several pre-mod TU 22 ARRIEL 2 engines, large circular cracks have been found on the free turbine shield at the blending radius between the containment shield and the rear flange.                                                                                                                                                                                                                                                                                                           |\n\n|     | Under the effects of manoeuvring loads, such cracks may potentially cause a loss of alignment of the engine and lead to its shutdown. |\n| --- | ------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJayaprakashan Ambali  \nDelegate of the Civil Aviation Safety Authority\n\n6 October 2005","sortOrder":0},{"sectionNumber":"AD/ARRIEL/21","sectionType":"part","heading":"AD/ARRIEL/21","content":"## AD/ARRIEL/21","sortOrder":1},{"sectionNumber":"Free Turbine Containment Shield","sectionType":"part","heading":"Free Turbine Containment Shield","content":"## Free Turbine Containment Shield","sortOrder":2},{"sectionNumber":"12/2005 DM","sectionType":"part","heading":"12/2005 DM","content":"## 12/2005 DM","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies specifically to pre‑mod TU22 Turbomeca Arriel 2B and 2B1 engines and mandates inspections/removal per the cited MSB. The text contains no indication that the applicability or substantive scope has been broadened or narrowed from the instrument's stated purpose."},"complexity_factors":["Dependence on an external Turbomeca Mandatory Service Bulletin (MSB No. 292 72 2821) and any later DGAC‑approved revisions (Requirement cross-reference).","Short initial compliance window (within 10 operating hours) creates immediate operational disruption risk (Compliance).","Inspection frequency is outcome‑dependent (intervals vary based on results), requiring judgment, recordkeeping and repeat actions (Compliance).","Decision to remove a shield depends on measuring crack length/position against MSB criteria—requires technical maintenance judgement and possible part replacement (Requirement).","Applicability limited to pre‑mod TU22 Arriel 2B/2B1 engines requires operators to track modification status and affected fleet (Applicability)."],"plain_english_summary":"This Airworthiness Directive requires operators of Turbomeca Arriel 2B and 2B1 (pre‑mod TU22) engines to visually inspect the free‑turbine containment shield per Turbomeca MSB No. 292 72 2821 within 10 operating hours and thereafter at MSB‑specified intervals, and to remove the shield if crack length or position exceed the MSB criteria (Requirement; Compliance).\n\nThe stated purpose is to detect cracks at the blending radius that could lead to loss of engine alignment and shutdown; operators pay for inspections, grounding and replacement and must comply before further flight."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific mechanical defect in specific engine models. It has not expanded beyond its original purpose of preventing free turbine shield failures."},"complexity_factors":["Single, specific mechanical component targeted (free turbine containment shield)","Only two defined engine models affected (ARRIEL 2B and 2B1)","Clear binary compliance: inspect, then either continue or remove from service","References external technical document (Turbomeca MSB) rather than embedding complex technical specifications","Simple temporal trigger (10 operating hours) with straightforward conditional follow-up","No nested exceptions, no cross-references to other legislation, no interpretive provisions"],"plain_english_summary":"This AD requires owners/operators of Turbomeca ARRIEL 2B and 2B1 engines (pre‑mod TU22) to inspect the free turbine containment shield for cracking and remove any shield that exceeds allowable crack limits before further flight. It affects helicopters using those engines (e.g., AS350 B3, EC130) and aims to prevent in‑flight shield failure that can misalign and shut down the engine. Initial inspection: within 10 hours' operation after 12 Oct 2005."}},"importantCases":[],"_links":{"self":"/api/acts/ad-arriel-21-free-turbine-containment-shield","history":"/api/acts/ad-arriel-21-free-turbine-containment-shield/history","analysis":"/api/acts/ad-arriel-21-free-turbine-containment-shield/analysis","conflicts":"/api/acts/ad-arriel-21-free-turbine-containment-shield/conflicts","importantCases":"/api/acts/ad-arriel-21-free-turbine-containment-shield/important-cases","documents":"/api/acts/ad-arriel-21-free-turbine-containment-shield/documents"}}