{"id":"F2006B02528","name":"AD/AS 355/79 - Hydraulic System - Hydraulic Cut Off Function","slug":"ad-as-355-79-hydraulic-system-hydraulic-cut-off-function","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41784,"registerId":"commonwealth-F2006B02528-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AS 355/79 - Hydraulic System - Hydraulic Cut Off Function","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 Safety Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  \n\n\n# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\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 CASR 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\n![](image.001.png)  \n\n\n \n\nEurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\n \n\n# AD/AS 355/79 Hydraulic System - Hydraulic Cut Off Function\n\n\n9/2004\n\n \n\nApplicability: AS 355 E helicopters, pre Modification 073263.\n\n \n\nRequirement: Modify the electrical wiring, in accordance with paragraphs 2.A., 2.B. and 2.C. of Eurocopter AS 355 Alert Service Bulletin No. 29.00.04. dated 14 April 2004.\n\n \n\nNote: DGAC AD F-2004-090 refers.\n\n \n\nCompliance: Before 31 December 2004.s\n\n \n\nThis Airworthiness Directive becomes effective on 2 September 2004.\n\n \n\nBackground: The actions required by this Directive are designed to eliminate the possibility of a load unbalance in the flight controls. This unbalance may occur after the loss of hydraulic assistance following a hydraulic failure.\n\n![](image.002.png)  \n\n\nBernard Malcolm Hole\n\nDelegate of the Civil Aviation Safety Authority 20 July 2004\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![](image.001.png)  \n\n\nThe above AD is notified in the Commonwealth of Australia Gazette on 11 August 2004.\n\n \n\n \n\n\nPage 1 of 1\n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive enforces a manufacturer‑specified wiring modification to address post‑hydraulic‑failure load unbalance (Background; Requirement). It does not expand the fleet scope beyond AS 355 E helicopters pre‑Mod 073263, nor impose obligations beyond completing the specified modification within the stated timeframe (Applicability; Compliance)."},"complexity_factors":["Technical specificity of the required electrical wiring modification (Requirement: refer to Eurocopter Alert Service Bulletin No. 29.00.04, paras 2.A–2.C).","Dependence on an external manufacturer document for the precise corrective action (Requirement references the Alert Service Bulletin).","Safety‑critical nature of the change (affects flight controls and hydraulic failure response) (Background).","Fixed compliance deadline and effective date create scheduling and procedural pressure on operators (Compliance; effective date).","Limited applicability reduces regulatory breadth but concentrates burden on owners/operators of AS 355 E helicopters pre‑Mod 073263 (Applicability).","Compliance likely requires certified maintenance personnel and parts, imposing direct cost and operational downtime on operators."],"plain_english_summary":"This Airworthiness Directive requires operators of Eurocopter AS 355 E helicopters (those not modified by Mod 073263) to change the aircraft electrical wiring per Eurocopter Alert Service Bulletin No. 29.00.04 (paras 2.A–2.C) to add a hydraulic cut‑off function that prevents flight‑control load unbalance after loss of hydraulic assistance. Issued under CASR subreg. 39.1(1), compliance was required before 31 December 2004 (effective 2 September 2004); operators bear the cost and must follow the manufacturer’s instructions to comply."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope: a targeted safety fix for a specific helicopter model's hydraulic system wiring. There is no evidence of scope creep; it addresses exactly one unsafe condition with one required action."},"complexity_factors":["Very short document (approximately 300 words)","Only 1 defined term implicitly referenced (Modification 073263)","Single, clear applicability criterion (AS 355 E helicopters, pre-Modification 073263)","Single mandatory action with external reference to manufacturer service bulletin","No nested conditions, exceptions, or cross-references to other legislation beyond the enabling regulation (CASR 1998, subregulation 39.1(1))","Simple linear structure: Applicability → Requirement → Compliance → Background"],"plain_english_summary":"This AD mandates that operators of AS 355 E (Twin Ecureuil) helicopters that have not had factory Modification 073263 must modify the hydraulic-system electrical wiring per Eurocopter Alert Service Bulletin No. 29.00.04 to prevent flight-control unbalance after hydraulic failure. It took effect 2 Sep 2004 and required compliance by 31 Dec 2004."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-79-hydraulic-system-hydraulic-cut-off-function","history":"/api/acts/ad-as-355-79-hydraulic-system-hydraulic-cut-off-function/history","analysis":"/api/acts/ad-as-355-79-hydraulic-system-hydraulic-cut-off-function/analysis","conflicts":"/api/acts/ad-as-355-79-hydraulic-system-hydraulic-cut-off-function/conflicts","importantCases":"/api/acts/ad-as-355-79-hydraulic-system-hydraulic-cut-off-function/important-cases","documents":"/api/acts/ad-as-355-79-hydraulic-system-hydraulic-cut-off-function/documents"}}