{"id":"F2006B02455","name":"AD/ARRIEL/9 - Overspeed Sensor","slug":"ad-arriel-9-overspeed-sensor","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41711,"registerId":"commonwealth-F2006B02455-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ARRIEL/9 - Overspeed Sensor","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Turbomeca Turbine Engines - Arriel Series\n\n \n\nAD/ARRIEL/9 Overspeed Sensor 4/95\n\nApplicability: Arriel 1A, 1A1 engines not incorporating modification TU 13, plus Arriel 1A2, 1C, 1C1, 1C2, 1E, 1E2, 1K, 1K1, 1S and 1S1 engines.\n\n \n\nRequirement: Carry out a check of the power turbine overspeed sensor in accordance with Turbomeca Arriel Service Bulletin 292-77-0194 Revision 1.\n\n \n\nNote: DGAC Airworthiness Directive 94-218(B) refers.\n\n \n\nCompliance: Prior to 30 April 1995.\n\n \n\nBackground: This Directive requires a once only check of the overspeed detector sensor to establish correct electrical connection. The requirement follows advice of a reversed connection between the two coils of the free power turbine overspeed sensor and the connector linking the sensor to the helicopter electrical harness.\n\n \n\n \n\ns\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-limited safety directive with a narrow, specific purpose. Airworthiness Directives are inherently limited in scope — they address particular unsafe conditions in specific aircraft or components. This AD maintains its original narrow scope: correcting a known manufacturing defect in a specific sensor on specific engine models."},"complexity_factors":["Single, discrete requirement (one specific check)","Limited applicability (12 engine variants, with one exclusion)","No defined terms section — all technical terms reference external manufacturer documentation","No conditional logic or nested exceptions","Single compliance deadline with no alternative methods","Short document (approximately 150 words of substantive content)","Cross-reference to only one external technical document (Turbomeca Service Bulletin)"],"plain_english_summary":"This AD mandates a one-time inspection of the power-turbine overspeed sensor wiring on specified Turbomeca Arriel 1-series engines (excludes 1A/1A1 with TU 13), to verify electrical connections are not reversed. A reversed connection could disable automatic shutdown during an overspeed and risk catastrophic engine failure. Operators must follow Turbomeca Service Bulletin 292-77-0194 Rev.1 and complete the check by 30 April 1995."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive imposes a targeted, one‑off inspection on a defined set of engines to verify correct electrical connection of the overspeed sensor. It does not expand ongoing regulatory obligations or broaden affected equipment beyond the listed models; it implements a corrective action aligned with the stated safety concern."},"complexity_factors":["Narrow applicability: specific Arriel engine models listed, with an exclusion for engines with modification TU 13 (Applicability).","Single, discrete action: a once‑only check rather than recurring inspections (Background; Requirement).","External technical reference: compliance requires following Turbomeca Service Bulletin 292‑77‑0194 Revision 1 (Requirement), so implementation depends on that document's procedures.","Fixed deadline: must be completed prior to 30 April 1995 (Compliance), creating a time‑bound compliance obligation.","Technical labour and access: requires qualified maintenance personnel and access to the sensor/connector (implied by the technical nature of the check).","Safety‑critical consequence: addresses reversed coil wiring that could impair overspeed detection (Background), raising implementation and verification importance.","Administrative verification: operators must be able to demonstrate the check was carried out to meet the AD (implied compliance burden)."],"plain_english_summary":"Requires operators of specified Turbomeca Arriel helicopter engines to perform a one‑time electrical check of the power‑turbine overspeed sensor, using Turbomeca Service Bulletin 292‑77‑0194 Revision 1. It applies to the listed Arriel models (excluding engines incorporating modification TU 13) and addresses a reported reversed connection between the sensor coils and the helicopter electrical harness that could stop the sensor working correctly."}},"importantCases":[],"_links":{"self":"/api/acts/ad-arriel-9-overspeed-sensor","history":"/api/acts/ad-arriel-9-overspeed-sensor/history","analysis":"/api/acts/ad-arriel-9-overspeed-sensor/analysis","conflicts":"/api/acts/ad-arriel-9-overspeed-sensor/conflicts","importantCases":"/api/acts/ad-arriel-9-overspeed-sensor/important-cases","documents":"/api/acts/ad-arriel-9-overspeed-sensor/documents"}}