{"id":"F2006B02526","name":"AD/AS 355/77 - Rear Structure Junction Frame","slug":"ad-as-355-77-rear-structure-junction-frame","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41782,"registerId":"commonwealth-F2006B02526-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# 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\nEurocopter AS 355 (Twin Ecureuil) Series Helicopters","sortOrder":0},{"sectionNumber":"AD/AS 355/77 Rear Structure Junction Fra","sectionType":"part","heading":"AD/AS 355/77 Rear Structure Junction Frame 5/2004","content":"# AD/AS 355/77 Rear Structure Junction Frame 5/2004\n\nApplicability: Model AS 355 E, F, F1, F2, and N helicopters:\n\n    \\- pre-Mod 073215, or\n\n    \\- not equipped with the four reinforcement angles, part numbers 350A08.2493.20 /\n\n.21 / .22 / .23, following the repair carried out in accordance with MRM Work Card 53.10.22.772.\n\nRequirement: Action in accordance with Eurocopter Alert Service Bulletin No. 05.00.42 original issue, or Revision 1.\n\nNote: DGAC AD F-2004-036 refers.\n\nCompliance: As specified in the Requirement document, with the effective date of this Directive substituted for receipt date of the Requirement document.\n\nThis Airworthiness Directive becomes effective on 13 May 2004.\n\nBackground: Reports were received by the manufacturer of cracks in the rear structure / tail boom junction frame during unscheduled inspections. In some cases, the crack lengths were significant and were not visible externally on the tail boom skin. Undetected cracking combined with a high thrust load from the tail rotor, may result in failure due to insufficient strength margins of the junction frame.\n\n![](image.002.png)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 2 April 2004\n\n![](image.001.png)","sortOrder":1}],"analysis":{"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":3,"scope_assessment":{"changed":false,"description":"This AD implements the Eurocopter Alert Service Bulletin for specific AS355 variants and does not broaden applicability or add obligations beyond requiring compliance with that ASB. The principal modification from the ASB is procedural: the AD uses its effective date in place of the ASB receipt date and establishes CASA enforcement under subregulation 39.1(1) (Applicability; Requirement; Compliance; Note)."},"complexity_factors":["Narrow technical applicability limited to AS355 E/F/F1/F2/N before Mod 073215 or without specified reinforcement angles (Applicability).","Mandates following an external manufacturer document (Eurocopter Alert Service Bulletin No. 05.00.42), creating reliance on that bulletin for procedural detail (Requirement).","Compliance timing substitutes the AD’s effective date for the ASB receipt date, which affects scheduling for operators (Compliance).","Hidden-failure risk: reported cracks can be internal and not visible externally, increasing inspection intrusiveness and detection difficulty (Background).","Enforcement authority vested in CASA delegate under CASR subreg 39.1(1), concentrating decision and compliance oversight with the delegate (opening paragraphs/signature).","Operators bear the direct costs and logistical burden of inspections and repairs; the directive does not provide funding or alternative compliance paths (Requirement; Compliance).","Cross-reference to DGAC AD F-2004-036 indicates alignment with a foreign regulator but requires operators to follow the local AD as written (Note)."],"plain_english_summary":"Requires operators of Eurocopter AS355 E/F/F1/F2/N helicopters that are pre‑Mod 073215 or lack four specified reinforcement angles to carry out inspections and any corrective repairs in accordance with Eurocopter Alert Service Bulletin No. 05.00.42 to address cracking at the rear-structure / tail-boom junction (Applicability; Requirement; Background). CASA enforces compliance from 13 May 2004; operators pay for and arrange the inspections/repairs performed under the delegate’s authority in subregulation 39.1(1) (Compliance)."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope — addressing a specific structural defect in specific helicopter models. There is no evidence of scope creep; it targets exactly the safety issue identified in the background (cracks in rear structure junction frame) and applies only to the affected aircraft configurations."},"complexity_factors":["Single specific technical requirement referencing external manufacturer document (Eurocopter Alert Service Bulletin)","Limited applicability criteria based on model numbers and modification status","No nested conditional logic or extensive cross-referencing within the instrument itself","Short, focused scope addressing one specific mechanical defect","Contains one external reference to French aviation authority (DGAC) directive for context"],"plain_english_summary":"Owners and operators of Eurocopter AS355 E/F/F1/F2/N helicopters must inspect and repair hidden cracks where the tail boom joins the airframe (per Eurocopter Alert Service Bulletin No. 05.00.42) if they haven’t received factory Mod 073215 or installed the reinforcement parts. This CASA safety order makes the inspections and repairs mandatory with compliance deadlines referenced from 13 May 2004 — aircraft cannot legally operate without completing the required work."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-77-rear-structure-junction-frame","history":"/api/acts/ad-as-355-77-rear-structure-junction-frame/history","analysis":"/api/acts/ad-as-355-77-rear-structure-junction-frame/analysis","conflicts":"/api/acts/ad-as-355-77-rear-structure-junction-frame/conflicts","importantCases":"/api/acts/ad-as-355-77-rear-structure-junction-frame/important-cases","documents":"/api/acts/ad-as-355-77-rear-structure-junction-frame/documents"}}