{"id":"F2006B09351","name":"AD/ECUREUIL/46 - Tail Rotor Drive Shaft Bearings","slug":"ad-ecureuil-46-tail-rotor-drive-shaft-bearings","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53584,"registerId":"commonwealth-F2006B09351-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ECUREUIL/46 - Tail Rotor Drive Shaft Bearings","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nEurocopter AS 350 (Ecureuil) Series Helicopters\n\nAD/ECUREUIL/46 Tail Rotor Drive Shaft Bearings 11/91\n\nDM\n\nApplicability: All AS 350 helicopters versions B, D, B1, B2, L1 and AVEX equipped with P/N P.9107.NPP7 FAFNIR tail rotor drive shaft bearings not marked with an “X” on the seal flange.\n\nRequirement: Action in accordance with the Technical Requirements of DGAC AD 91-159-060 (B) for all aircraft acceptance tested by Aerospatiale Marignane between 15 May 1991 and 20 July 1991 or prior to 15 May 1991 and have operated less than 100 hours time in service.\n\nNote: Aerospatiale Telex Service No. 01-34 refers.\n\nCompliance: By 30 August 1991 or prior to issue of Australian C of A, whichever occurs first. Background: Corroded bearings which could seize may have been fitted to the tail rotor drive shaft.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive targets a specific safety issue for a defined subset of AS 350 helicopters (specified part number and acceptance-test date/hours). It imposes a corrective action consistent with that narrow safety objective and does not broaden general regulatory obligations beyond requiring compliance with the referenced technical instructions. (Applicability; Requirement; Compliance; Background.)"},"complexity_factors":["Narrow applicability tied to a specific part number and a physical mark on the part (P.9107.NPP7 FAFNIR; absence of an “X”)","Time-window conditions for applicability (acceptance tested between 15 May 1991 and 20 July 1991; or tested prior to 15 May 1991 with <100 hours)","Requirement refers to an external technical document (DGAC AD 91-159-060 (B)) and an Aerospatiale telex, creating dependency on other texts","A fixed compliance deadline or linkage to issuance of Certificate of Airworthiness (administrative enforcement)","Operational tasks required (record checks, physical inspection, possible removal/repair/replacement) but limited in scope to a specific component and cohort of aircraft"],"plain_english_summary":"This directive requires owners/operators of specified Eurocopter AS350 variants fitted with tail-rotor drive-shaft bearings (P.9107.NPP7 FAFNIR) that lack an “X” mark to carry out the DGAC-prescribed technical actions (and Aerospatiale telex details) by 30 August 1991 or before issue of the Australian C of A. It targets aircraft accepted in mid‑1991 (or earlier with <100 hours). Operators bear compliance costs and the regulator may withhold certification; the measure addresses risk of corroded bearings seizing the tail rotor drive."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific manufacturing defect in a specific component. It has not expanded beyond its original purpose of addressing corroded tail rotor drive shaft bearings in affected Eurocopter AS 350 helicopters."},"complexity_factors":["Short, single-issue directive with one specific mechanical fault","Limited applicability criteria (specific helicopter models, specific part numbers, specific manufacturing date ranges, specific flight hour thresholds)","Single external reference to French aviation authority technical requirements (DGAC AD 91-159-060 (B))","No defined terms section or interpretation provisions","Simple binary compliance deadline (fixed date or prior to certification)","No nested exceptions or conditional logic beyond the applicability criteria"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for specific helicopters.\n\n**What it does:** It orders owners and operators of certain Eurocopter AS 350 helicopters to inspect or replace specific tail rotor drive shaft bearings. These bearings (part number P.9107.NPP7 FAFNIR) might be corroded and could seize up, which would be catastrophic for the tail rotor system that keeps the helicopter stable.\n\n**Who it affects:** \n- **Aircraft:** Eurocopter AS 350 helicopters (versions B, D, B1, B2, L1, and AVEX)\n- **Specific condition:** Only those with bearings that **don't** have an \"X\" marked on the seal flange\n- **Timeframe:** Only helicopters acceptance-tested by Aerospatiale Marignane between 15 May 1991 and 20 July 1991, OR tested before 15 May 1991 but with less than 100 flight hours\n\n**What must be done:** Follow the technical instructions in a French aviation safety document (DGAC AD 91-159-060 (B)) to fix the bearing problem.\n\n**When it had to be done:** By 30 August 1991, or before the helicopter could get its Australian Certificate of Airworthiness (C of A) — whichever came first.\n\n**Why it matters:** Corroded bearings in the tail rotor drive shaft could seize, causing loss of tail rotor control. This could lead to an uncontrolled spin or crash. The directive prevents this by catching affected aircraft before they fly."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ecureuil-46-tail-rotor-drive-shaft-bearings","history":"/api/acts/ad-ecureuil-46-tail-rotor-drive-shaft-bearings/history","analysis":"/api/acts/ad-ecureuil-46-tail-rotor-drive-shaft-bearings/analysis","conflicts":"/api/acts/ad-ecureuil-46-tail-rotor-drive-shaft-bearings/conflicts","importantCases":"/api/acts/ad-ecureuil-46-tail-rotor-drive-shaft-bearings/important-cases","documents":"/api/acts/ad-ecureuil-46-tail-rotor-drive-shaft-bearings/documents"}}