{"id":"F2008L04460","name":"AD/ARRIUS/17 - Engine Lubrication Unit Check Valve","slug":"ad-arrius-17-engine-lubrication-unit-check-valve","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":76461,"registerId":"commonwealth-F2008L04460-current","compilationNumber":null,"startDate":"2026-04-02","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/17 | Engine Lubrication Unit Check Valve | 13/2008 |\n| ------------ | ----------------------------------- | ------- |\n\n| Applicability: | Turbomeca ARRIUS 2F turbo-shaft engines which do not embody modification Tf75.Note 1: These engines are known to be installed on, but not limited to, Eurocopter EC120B helicopters. |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement: | Replace the check valve piston and remove preformed packing in accordance with Turbomeca Service Bulletin no. 319 79 4075 or later approved revision.Note 2: EASA AD 2008-0170 dated 25 September 2008 refers. |\n| Compliance: | No later than 31 May 2009. |\n| | This Airworthiness Directive becomes effective on 18 December 2008. |\n| Background: | Investigations of incidents which occurred on ARRIUS 2 turboshaft engines have revealed the interruption of engine lubrication further 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 on the class of the oil used (Standard (STD) or High-Thermal Stability (HTS)) and the engine operating time. This phenomenon only affects ARRIUS 2F engines which do not embody modification Tf75.Blockage of the check valve may result in bearing damage caused by a lack of lubrication to the bearings which may lead to an uncommanded or commanded in-flight shutdown which, on a single-engine helicopter, leads to an emergency autorotation landing.This AD is issued to eliminate the possibility of a check valve blockage due to an excessive swelling of the check valve piston o-ring, by mandating the replacement of the current check valve piston by a check valve with seal-free piston. |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n6 November 2008","sortOrder":0},{"sectionNumber":"AD/ARRIUS/17","sectionType":"part","heading":"AD/ARRIUS/17","content":"## AD/ARRIUS/17","sortOrder":1},{"sectionNumber":"Engine Lubrication Unit Check Valve","sectionType":"part","heading":"Engine Lubrication Unit Check Valve","content":"## Engine Lubrication Unit Check Valve","sortOrder":2},{"sectionNumber":"13/2008","sectionType":"part","heading":"13/2008","content":"## 13/2008","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's scope aligns with the stated intent in the source text: it targets ARRIUS 2F engines without modification Tf75 and mandates replacing the check‑valve piston to eliminate o‑ring swelling and potential oil blockage. The instrument does not broaden or narrow applicability beyond that stated."},"complexity_factors":["Narrow applicability: only ARRIUS 2F engines that do not embody modification Tf75 (Applicability).","Single mandatory technical action: replace check valve piston and remove preformed packing per Turbomeca Service Bulletin no. 319 79 4075 (Requirement).","Fixed compliance deadline (No later than 31 May 2009) creates scheduling and operational constraints for affected operators (Compliance).","Reference to an external document and later approved revisions (service bulletin; EASA AD 2008-0170) requires tracking of approved revisions.","Safety consequence linkage: failure to comply risks bearing damage and engine shutdown, increasing enforcement pressure (Background).","Logistical and cost considerations: parts availability, maintenance labour and aircraft downtime fall on owners/operators.","Regulatory enforcement: CASA delegateed issuance and effective date set (becomes effective 18 December 2008), leaving limited administrative discretion."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of Turbomeca ARRIUS 2F engines without modification Tf75 to replace the lubrication-unit check‑valve piston with a seal‑free piston and remove preformed packing, following Turbomeca Service Bulletin no. 319 79 4075, by 31 May 2009. Owners/operators pay for and arrange the work; the Civil Aviation Safety Authority issued and enforces the requirement to prevent oil‑passage blockage from o‑ring swelling that can cause bearing damage and engine shutdown."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in a specific engine model. It has not expanded beyond its original purpose of preventing check valve blockage in ARRIUS 2F engines."},"complexity_factors":["Single, specific technical requirement (replace one component)","Only one defined applicability criterion (engine model + modification status)","Simple compliance deadline (single date, no flight hours or cycles)","No nested exceptions or conditional logic","Cross-reference to only one external document (EASA AD and manufacturer service bulletin)","Short, single-issue scope with clear background explanation"],"plain_english_summary":"This mandatory AD requires owners/operators of Turbomeca ARRIUS 2F turboshaft engines (e.g., on Eurocopter EC120B) not modified with Tf75 to replace a check‑valve piston with a seal‑free design and remove packing per Turbomeca SB 319 79 4075. It addresses swollen o‑rings that can block oil flow, risk bearing seizure and in‑flight engine failure. The directive was effective 18 Dec 2008 with compliance required by 31 May 2009."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-arrius-17-engine-lubrication-unit-check-valve","history":"/api/acts/ad-arrius-17-engine-lubrication-unit-check-valve/history","analysis":"/api/acts/ad-arrius-17-engine-lubrication-unit-check-valve/analysis","conflicts":"/api/acts/ad-arrius-17-engine-lubrication-unit-check-valve/conflicts","importantCases":"/api/acts/ad-arrius-17-engine-lubrication-unit-check-valve/important-cases","documents":"/api/acts/ad-arrius-17-engine-lubrication-unit-check-valve/documents"}}