{"id":"F2006B02469","name":"AD/AS 355/10 Amdt 4 - Main Rotor Mast","slug":"ad-as-355-10-amdt-4-main-rotor-mast","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41725,"registerId":"commonwealth-F2006B02469-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AS 355/10 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 355 (Twin Ecureuil) Series Helicopters\n\nAD/AS 355/10\n\nAmdt 4\n\n  \nMain Rotor Mast 5/88\n\nApplicability: All models with main rotor masts P/N 350A37.1076.04, .05 or .06.\n\nRequirement: 1. (a) Perform the visual check and if necessary, the dye penetrant/inspection called for in Aerospatiale SB 05-08 Rev 2 para’s C(1) and C(2).\n\n(b) Protect any reworked surfaces in accordance with Aerospatiale SB 05-08 Rev 2 para C(3).\n\n2. Aerospatiale SB 05-08 Rev 2.\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 85-94-25(b) and Bureau Veritas AD 83-174-20(b) 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 05-08 Rev 2 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 85-94-25(B) which requires a one time 10 hour inspection of the main rotor shaft. The requirements of Bureau Veritas AD 85-94-25(B) supplement those of Bureau Veritas AD 83-174-20(b), which were noted in the previous issue of this AD. This Amendment incorporates Revision 2 of the Service Bulletin.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is Amendment 4 of an existing Airworthiness Directive. The amendments have remained tightly focused on the original safety issue (main rotor mast fatigue cracking) and have not expanded beyond the specific part numbers and inspection requirements originally targeted. The amendments incorporate updated service bulletin revisions and clarify compliance with related foreign directives, but do not broaden the applicability or introduce new unrelated requirements."},"complexity_factors":["Short, single-purpose directive (approximately 250 words)","Only 3 defined part numbers in applicability section","Two main requirements with sub-paragraphs (1(a), 1(b), and 2)","Two notes providing alternative compliance methods","Cross-references to 2 foreign airworthiness directives (Bureau Veritas ADs) and 1 service bulletin","Single compliance deadline with conditional exception ('unless already accomplished')","No nested exceptions or complex conditional logic"],"plain_english_summary":"This AD mandates urgent inspections and repairs of main rotor masts on Eurocopter AS 355 Twin Ecureuil helicopters with specified part numbers, after a fatigue crack from hidden corrosion was found. Owners/operators must perform visual and dye‑penetrant (or preferred magnetic particle) inspections, repair and protect any affected surfaces, and follow Aerospatiale Service Bulletin 05‑08 Rev 2. It’s intended to detect cracks early and prevent catastrophic mast failure."},"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"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"This amendment incorporates Aerospatiale SB 05‑08 Rev 2 and adopts the requirements of Bureau Veritas AD 85‑94‑25(B), which supplement the previously noted Bureau Veritas AD 83‑174‑20(b). As amended, it expressly mandates a one‑time inspection within 10 hours and protective treatment of any reworked surfaces, clarifying and adding to the directive’s earlier requirements."},"complexity_factors":["References and reliance on external technical documents: Aerospatiale SB 05‑08 Rev 2 and Bureau Veritas ADs (85‑94‑25(B) and 83‑174‑20(b))","Technical inspection options and preferences (dye penetrant or magnetic particle) requiring specific skills/equipment","Short compliance window (one‑time inspection within 10 hours TIS after the specified date)","Part‑number‑specific applicability (limits scope to masts P/N 350A37.1076.04/.05/.06)","Requirement both to inspect and to protect any reworked surfaces (inspection plus follow‑on work and materials)","Amendment history: incorporates Revision 2 of the Service Bulletin, creating potential differences from earlier instructions"],"plain_english_summary":"This airworthiness directive requires owners/operators of Eurocopter AS 355 helicopters fitted with main rotor mast P/N 350A37.1076.04, .05 or .06 to carry out a one‑time visual and dye‑penetrant (magnetic particle preferred) inspection and to protect any reworked surfaces per Aerospatiale Service Bulletin 05‑08 Rev 2, within 10 hours time in service. The measure is prompted by a fatigue crack from an undetected corrosion pit and adopts related Bureau Veritas AD requirements; inspection and any corrective work are carried out and paid for by the aircraft owner/operator."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-10-amdt-4-main-rotor-mast","history":"/api/acts/ad-as-355-10-amdt-4-main-rotor-mast/history","analysis":"/api/acts/ad-as-355-10-amdt-4-main-rotor-mast/analysis","conflicts":"/api/acts/ad-as-355-10-amdt-4-main-rotor-mast/conflicts","importantCases":"/api/acts/ad-as-355-10-amdt-4-main-rotor-mast/important-cases","documents":"/api/acts/ad-as-355-10-amdt-4-main-rotor-mast/documents"}}