{"id":"F2006B09336","name":"AD/ECUREUIL/23 Amdt 4 - Main Rotor Mast","slug":"ad-ecureuil-23-amdt-4-main-rotor-mast","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53528,"registerId":"commonwealth-F2006B09336-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ECUREUIL/23 Amdt 4 - Main Rotor Mast","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/23\n\nAmdt 4\n\n  \nMain Rotor Mast 5/88\n\nApplicability: All models with main rotor masts P/N 350A37.1076 .00 to .06\n\nRequirement: 1. (a) Perform the visual check and if necessary, the dye penetrant check called for in Aerospatiale SB 05-13 Rev 3 para’s C(1) and C(2).\n\n(b) Protect any reworked surfaces in accordance with Aerospatiale SB 05-13 Rev 3 para C(3).\n\n2. Aerospatiale SB 05-13 Rev 3.\n\nNote 1: Magnetic particle inspection may be carried out in lieu of dye penetrant and is the preferred technique.\n\nNote 2: Bureau Veritas AD 85-95-40(B) and Bureau Veritas AD 83-173-36(c) refer.\n\nCompliance: 1. Within 10 hours time in service after 30 November 1985, unless already accomplished.\n\n2. As detailed in the requirement document \\- Aerospatiale SB 05-13 Rev 3 para D.\n\nBackground: A fatigue crack initiated from an undetected corrosion pit on an overseas operated helicopter, and propagated to a critical size in 170 hours time in service. This AD has been amended in accordance with the requirement of Bureau Veritas AD 85-94-40(B) which required a one time 10 hour inspection of the main rotor shaft. The requirements of Bureau Veritas AD 85-95-40(B) supplement those of Bureau Veritas AD 83-173-36(c), which were noted in the previous issue of this AD. This Amendment incorporates Revision 3 of the S.B.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original 1985/1988 directive has been amended four times. This version incorporates Revision 3 of the manufacturer's service bulletin and aligns with updated French aviation authority requirements (Bureau Veritas AD 85-95-40(B)). While the core safety purpose remains unchanged (preventing main rotor mast failures), the scope has evolved to include updated inspection techniques and clarified compliance requirements. However, it has not expanded beyond its original safety-critical purpose."},"complexity_factors":["Short, single-purpose document focused on one mechanical component","Only 2 main requirements with clear cross-reference to manufacturer service bulletin (SB 05-13 Rev 3)","Limited applicability (specific part number range: P/N 350A37.1076 .00 to .06)","Simple conditional logic: visual check first, then dye penetrant only 'if necessary'","Contains 2 notes and references to 2 foreign airworthiness directives for context, but these don't create additional compliance burden","No defined terms section — uses standard aviation terminology","Clear compliance deadline (10 hours time in service after specific date)"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of Eurocopter AS350 (Ecureuil/Squirrel) helicopters with main rotor masts P/N 350A37.1076.00–.06 to inspect the mast for hidden corrosion/cracks: visual inspection, with dye‑penetrant (magnetic particle preferred) follow‑up and specified protection of any repairs, within 10 flight hours after 30 Nov 1985 unless already done.\n\nPrompted by a fatigue crack incident, this 4th amendment aligns CASA with French authorities and the manufacturer’s Service Bulletin Revision 3 to prevent catastrophic rotor failure."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"This amendment updates the AD to incorporate Aerospatiale SB 05-13 Revision 3 and to align with Bureau Veritas AD requirements, creating a one‑time, urgent (10‑hour) inspection obligation and specifying rework protection and acceptable NDT methods. In short, the amendment refines and expands procedural detail and ties the AD directly to the Rev 3 service bulletin and referenced Bureau Veritas ADs (Requirement; Compliance; Background)."},"complexity_factors":["Narrow, parts-based applicability limited to mast P/N 350A37.1076.00–.06 (Applicability).","Dependence on external technical documents: Aerospatiale SB 05-13 Rev 3 as the operative requirement (Requirement 1 and 2).","Urgent compliance timeframe (within 10 hours TIS after 30 Nov 1985) creates operational disruption and scheduling pressure (Compliance).","Multiple NDT options permitted (dye penetrant or magnetic particle) requiring technical judgement and equipment (Requirement 1; Note 1).","Mandate to protect any reworked surfaces adds material/labour scope beyond inspection (Requirement 1(b)).","Cross-references to Bureau Veritas ADs add layered regulatory obligations and possible interpretive complexity (Notes; Background).","Background justification is event-driven (single overseas occurrence: crack to critical size in 170 hours), limiting the breadth of empirical evidence (Background)."],"plain_english_summary":"Mandates a one‑time inspection and any necessary repair/protection of the main rotor mast (P/N 350A37.1076.00–.06) on Eurocopter AS350 helicopters by following Aerospatiale Service Bulletin 05‑13 Rev 3: visual and dye‑penetrant (or magnetic particle) checks and protection of reworked surfaces. Work must be done within 10 hours time‑in‑service after 30 Nov 1985 unless already accomplished. The AD responds to a fatigue crack traced to a corrosion pit; operators pay for inspections and repairs under the referenced service bulletin."},"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-ecureuil-23-amdt-4-main-rotor-mast","history":"/api/acts/ad-ecureuil-23-amdt-4-main-rotor-mast/history","analysis":"/api/acts/ad-ecureuil-23-amdt-4-main-rotor-mast/analysis","conflicts":"/api/acts/ad-ecureuil-23-amdt-4-main-rotor-mast/conflicts","importantCases":"/api/acts/ad-ecureuil-23-amdt-4-main-rotor-mast/important-cases","documents":"/api/acts/ad-ecureuil-23-amdt-4-main-rotor-mast/documents"}}