{"id":"F2005L02094","name":"AD/ARRIUS/10 - Oil - Check-Valve Piston O-ring","slug":"ad-arrius-10-oil-check-valve-piston-o-ring","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":36322,"registerId":"commonwealth-F2005L02094-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Turbomeca Turbine Engines - Arrius Serie","sectionType":"division","heading":"Turbomeca Turbine Engines - Arrius Series","content":"### Turbomeca Turbine Engines - Arrius Series\n\n| AD/ARRIUS/10 | Oil - Check-Valve Piston O-ring | 9/2005 |\n| ------------ | ------------------------------- | ------ |\n\n| Applicability: | TURBOMECA turboshaft engine ARRIUS 2F fitted to EC 120B helicopters.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Carry out paragraph 2 of Turbomeca Mandatory Alert Service Bulletin No A319 79 4802 or later DGAC approved revisions.2. Repeat Requirement 1 of this Directive.Note: DGAC AD F-2005-122 EASA approval reference No 2005-6069 dated 12 July 2005 refers.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |\n| Compliance:    | 1. After the effective date of this Directive, unless previously accomplished, carry out within the next 50 operating hours if the number of operating hours is greater than:300 hours for engines operating with HTS-class oil and engines for which the history of the oils used is not available or engines which used to operate with HTS-class oil and which no longer do so;450 hours for engines operating with STD class-oil since their introduction into service.2. Every 300 hours for engines operating with HTS-class oil and engines for which the history of the oils used is not available or engines which used to operate with HTS-class oil and which no longer do so;Every 500 hours for engines operating with STD class-oil since their introduction into service. |\n|                | This Airworthiness Directive becomes effective on 1 September 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |\n| Background:    | Investigations of incidents which occurred on ARRIUS 2 turboshaft engines have revealed the interruption of engine lubrication due to oil passage blockage within the lubrication unit check valve.This blockage comes from the excessive swelling of the check valve piston O-ring. The level of swelling of the O-ring depends from the class of the oil used (STD or HTS) and the engine operating time.                                                                                                                                                                                                                                                                                                                                                                              |\n\n|     | An interruption of the engine lubrication may lead to an uncommanded in-flight shutdown. |\n| --- | ---------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n19 July 2005","sortOrder":0},{"sectionNumber":"AD/ARRIUS/10","sectionType":"part","heading":"AD/ARRIUS/10","content":"## AD/ARRIUS/10","sortOrder":1},{"sectionNumber":"Oil - Check-Valve Piston O-ring","sectionType":"part","heading":"Oil - Check-Valve Piston O-ring","content":"## Oil - Check-Valve Piston O-ring","sortOrder":2},{"sectionNumber":"9/2005","sectionType":"part","heading":"9/2005","content":"## 9/2005","sortOrder":3}],"analysis":{"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"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"Scope is limited to Turbomeca Arrius 2F engines installed on EC 120B helicopters and prescribes inspections/repeats per oil class. The instrument, as presented, does not expand or narrow that applicability beyond the stated aircraft/engine combination."},"complexity_factors":["Variable compliance intervals tied to oil class and engine operating hours (Compliance section)","Requirement depends on following an external technical document (Turbomeca Mandatory Alert Service Bulletin A319 79 4802)","Repeat inspection obligation (ongoing maintenance scheduling and record-keeping burden)","Cross-reference to foreign regulator approvals (DGAC/EASA) increasing multi-jurisdictional dependency","Technical cause relates to O‑ring swelling and oil chemistry, requiring specialist maintenance knowledge (Background)"],"plain_english_summary":"This directive requires operators of EC 120B helicopters fitted with Turbomeca Arrius 2F engines to carry out the Turbomeca Mandatory Alert Service Bulletin A319 79 4802 procedure to address swelling of the lubrication unit check‑valve piston O‑ring. Initial and repeat inspection intervals vary by oil class: for HTS or unknown oil history, initial within 50 hours if engine hours >300 and then every 300 hours; for STD‑oil engines, initial within 50 hours if >450 hours and then every 500 hours. Operators pay for inspections and repairs; CASA enforces compliance."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive addressing a specific mechanical defect in specific engine models. It has not expanded beyond its original safety purpose."},"complexity_factors":["Short, single-purpose document (1 page)","Only 2 main requirements with clear conditional logic based on oil type","4 defined scenarios for compliance timing (HTS vs STD oil, initial vs repeat inspections)","Single cross-reference to French aviation authority (DGAC) and manufacturer service bulletin","No nested exceptions or recursive definitions","Technical but straightforward — assumes aviation maintenance knowledge but doesn't create legal complexity"],"plain_english_summary":"CASA requires owners/operators of EC 120B helicopters with TURBOMECA ARRIUS 2F engines to inspect and, if needed, repair the oil check‑valve O‑ring because it can swell and block oil flow, risking engine failure. Inspections must start promptly and recur every 300 hours for HTS/unknown oil or every 500 hours for STD oil to prevent in‑flight engine loss."}},"importantCases":[],"_links":{"self":"/api/acts/ad-arrius-10-oil-check-valve-piston-o-ring","history":"/api/acts/ad-arrius-10-oil-check-valve-piston-o-ring/history","analysis":"/api/acts/ad-arrius-10-oil-check-valve-piston-o-ring/analysis","conflicts":"/api/acts/ad-arrius-10-oil-check-valve-piston-o-ring/conflicts","importantCases":"/api/acts/ad-arrius-10-oil-check-valve-piston-o-ring/important-cases","documents":"/api/acts/ad-arrius-10-oil-check-valve-piston-o-ring/documents"}}