{"id":"F2006B02446","name":"AD/ARRIEL/15 - Centrifugal Impeller","slug":"ad-arriel-15-centrifugal-impeller","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41702,"registerId":"commonwealth-F2006B02446-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/15 Centrifugal Impeller 6/2002","sectionType":"part","heading":"AD/ARRIEL/15 Centrifugal Impeller 6/2002","content":"# AD/ARRIEL/15 Centrifugal Impeller 6/2002\n\nApplicability: All Arriel 2 turboshaft engines.\n\nRequirement: 1. Carry out installation of a sleeve in the bleed valve boss as described in Turbomeca Service Bulletin (SB) No. 292 72 2054.\n\n2. Carry out bonding of sleeve in the bleed valve boss as described in Turbomeca SB No. 292 72 2070 Update 1.\n\nNote: DGAC AD 2002-127(A) refers.\n\nCompliance: Unless previously accomplished; within 100 hours time in service or prior to 31 July 2002, whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 13 June 2002.\n\nBackground: Several contained centrifugal impeller blade ruptures have been observed in service.\n\nThese failures led to a power loss but could have led to non commanded in-flight shutdowns. Investigations revealed that acoustic excitation was the cause of the failures. The excitation caused by coupling that may occur between the impeller blades and the acoustic cavity. Incorporation of SB No. 292 72 2054 and SB No. 292 72 2070 will suppress this excitation.\n\n![](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 12 April 2002\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD does not expand or narrow the product group beyond its stated target: it applies to all Arriel 2 engines and mandates two specific modifications per the cited service bulletins within the stated compliance window. The requirement and compliance terms align with the safety rationale in the Background and do not introduce additional inspection classes, operators, or engine models (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Narrow applicability — applies only to Turbomeca Arriel 2 turboshaft engines (Applicability).","Prescriptive technical remedy — requires specific physical modifications identified by two Turbomeca Service Bulletins (Requirement).","Fixed compliance deadline — within 100 flight hours or by a calendar date (Compliance).","Dependence on external manufacturer documents — enforcement relies on SB Nos. 292 72 2054 and 292 72 2070 Update 1 (Requirement).","Clear regulatory authority — issued under CAR 1998 subregulation 39.1(1) by CASA delegate (preamble/signature).","Implementation cost and scheduling burden falls on operators — modification must be carried out in-service (Requirement; Compliance).","Technical causal finding (acoustic excitation) informs a narrowly targeted fix rather than ongoing monitoring (Background).","Limited administrative discretion — directive prescribes action and timing rather than granting broad exemptions or choices (Requirement; Compliance)."],"plain_english_summary":"This Airworthiness Directive requires operators of Turbomeca Arriel 2 turboshaft engines to install and bond a sleeve in the bleed-valve boss following Turbomeca Service Bulletins No. 292 72 2054 and No. 292 72 2070 Update 1 to stop acoustic excitation that has caused centrifugal impeller blade ruptures (Applicability; Requirement; Background). CASA (delegate under CAR 1998 subreg 39.1(1)) mandates the work within 100 flight hours or by 31 July 2002; operators must schedule and pay for the modification during maintenance windows (Compliance; Requirement)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow airworthiness directive addressing a specific mechanical defect in a specific engine series. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (under 300 words)","Only 2 substantive requirements, both referencing external technical documents (Service Bulletins)","Single applicability criterion (all Arriel 2 engines)","Simple compliance deadline (100 hours OR fixed date)","No defined terms section, no cross-references to other legislation beyond the enabling regulation (CAR 1998 subreg 39.1(1))","No conditional logic or exceptions"],"plain_english_summary":"This CASA safety order requires operators of Turbomeca Arriel 2 engines to install and bond a metal sleeve in the bleed‑valve boss per Service Bulletins 292‑72‑2054 and 292‑72‑2070. It fixes vibration in a cavity that has led to centrifugal impeller blade failures and in‑flight power loss. Compliance was mandatory within 100 flight hours or by 31 July 2002 (if not already done)."},"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-arriel-15-centrifugal-impeller","history":"/api/acts/ad-arriel-15-centrifugal-impeller/history","analysis":"/api/acts/ad-arriel-15-centrifugal-impeller/analysis","conflicts":"/api/acts/ad-arriel-15-centrifugal-impeller/conflicts","importantCases":"/api/acts/ad-arriel-15-centrifugal-impeller/important-cases","documents":"/api/acts/ad-arriel-15-centrifugal-impeller/documents"}}