{"id":"F2006L00746","name":"AD/AS 355/89 - Tail Rotor Drive Shaft - Forward Shaft Section","slug":"ad-as-355-89-tail-rotor-drive-shaft-forward-shaft-section","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":136769,"registerId":"commonwealth-F2006L00746-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Eurocopter AS 355 (Twin Ecureuil) Series","sectionType":"division","heading":"Eurocopter AS 355 (Twin Ecureuil) Series Helicopters","content":"### Eurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\n| AD/AS 355/89 | Tail Rotor Drive Shaft - Forward Shaft Section | 4/2006 |\n| ------------ | ---------------------------------------------- | ------ |\n\n| Applicability: | Eurocopter AS 355 E, F, F1, F2 and N helicopters fitted with tail rotor drive shaft forward shaft section, part number 355A 34-1090-00 with serial numbers from M858 to M873 inclusive.This AD does not apply to helicopters delivered after 1 January 2005.                                                                                                          |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Replace the drive shaft with a drive shaft not listed by serial number in this AD in accordance with Paragraph 2.B of Eurocopter Alert Service Bulletin No. 01.00.51.2. Do not install drive shaft listed by serial number in this AD, held as spares.Note: DGAC AD F-2005-082, EASA approval number 2005-4319 dated18 May 2005 refers.                            |\n| Compliance:    | 1. For drive shafts that have accumulated less than 2,400 flying hours, at the latest at 2,500 hours or by 30 June 2006, whichever occurs first.For drive shafts that have accumulated more than 2,400 flying hours, at the latest within 100 hours from the effective date of this AD or 30 June 2006, whichever occurs first.2. From the effective date of this AD. |\n|                | This Airworthiness Directive becomes effective on 13 April 2006.                                                                                                                                                                                                                                                                                                      |\n| Background:    | The AD is issued following the discovery of non-conformity on the flange of the drive shaft. The non-conformity may significantly reduce the strength and the service life of the component.                                                                                                                                                                          |\n\n![](image.001.png)  \nJayaprakashan Ambali  \nDelegate of the Civil Aviation Safety Authority\n\n21 February 2006","sortOrder":0},{"sectionNumber":"AD/AS 355/89","sectionType":"part","heading":"AD/AS 355/89","content":"## AD/AS 355/89","sortOrder":1},{"sectionNumber":"Tail Rotor Drive Shaft - Forward Shaft S","sectionType":"part","heading":"Tail Rotor Drive Shaft - Forward Shaft Section","content":"## Tail Rotor Drive Shaft - Forward Shaft Section","sortOrder":2},{"sectionNumber":"4/2006","sectionType":"part","heading":"4/2006","content":"## 4/2006","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies only to a defined set of forward drive‑shaft serial numbers and excludes helicopters delivered after 1 January 2005. The text provides no indication that the AD’s scope was expanded or narrowed from its original purpose of removing non‑conforming shafts."},"complexity_factors":["Narrow technical applicability: specific part number and serial numbers (Applicability).","Two-tier compliance timeline tied to accumulated flight hours and a calendar deadline (Compliance).","Mandatory follow-up action referencing an external manufacturer service bulletin for procedural detail (Requirement: Paragraph 2.B of Eurocopter ASB No. 01.00.51.2).","Prohibition on installing listed serial-numbered spare parts, creating logistics and parts-control obligations (Requirement).","Regulatory cross-references and approvals noted (DGAC AD and EASA approval), adding layers for international compliance records (Requirement/Note).","Operational impacts: replacement cost, aircraft downtime, hours-tracking and record-keeping burdens for operators (Compliance/Background)."],"plain_english_summary":"This airworthiness directive requires owners/operators of Eurocopter AS 355 E/F/F1/F2/N helicopters fitted with tail‑rotor forward drive shaft part 355A 34‑1090‑00, serials M858–M873, to replace those shafts and forbids installing those listed spares. It sets replacement deadlines tied to flight hours or a fixed date. The AD says a flange non‑conformity may reduce strength and service life; operators therefore bear replacement costs, must track hours, follow Eurocopter’s service bulletin, and accept aircraft downtime and record‑keeping burdens."},"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 is a targeted safety directive addressing a specific manufacturing defect in a specific aircraft component. The scope remains precisely limited to the identified safety risk and has not expanded beyond the original technical defect remediation."},"complexity_factors":["Very short document (approximately 300 words)","Only 1 defined term (the specific part number and serial number range)","Simple conditional logic based solely on accumulated flight hours (two categories: <2,400 hours vs >2,400 hours)","No cross-references to other legislation or complex regulatory frameworks — only references a Eurocopter service bulletin and a French aviation directive for background","Single, clear compliance action (replacement) with straightforward deadline calculations","Limited applicability (specific helicopter models, specific part numbers, specific serial number range, plus one date-based exclusion)"],"plain_english_summary":"This AD requires owners/operators of Eurocopter AS355 E/F/F1/F2/N helicopters fitted with forward tail-rotor drive shafts SN M858–M873 to replace those shafts per the manufacturer’s repair bulletin and prohibits installing them as spares. \n\nThe affected shafts have a manufacturing defect that can weaken the flange and cause in-flight tail-rotor drive failure, risking loss of directional control. Replacement deadlines depend on hours-in-service (short-term for high-use units)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-89-tail-rotor-drive-shaft-forward-shaft-section","history":"/api/acts/ad-as-355-89-tail-rotor-drive-shaft-forward-shaft-section/history","analysis":"/api/acts/ad-as-355-89-tail-rotor-drive-shaft-forward-shaft-section/analysis","conflicts":"/api/acts/ad-as-355-89-tail-rotor-drive-shaft-forward-shaft-section/conflicts","importantCases":"/api/acts/ad-as-355-89-tail-rotor-drive-shaft-forward-shaft-section/important-cases","documents":"/api/acts/ad-as-355-89-tail-rotor-drive-shaft-forward-shaft-section/documents"}}