{"id":"F2006B09148","name":"AD/DHC-6/60 Amdt 4 - Wing Front Spar Attachment Adaptors","slug":"ad-dhc-6-60-amdt-4-wing-front-spar-attachment-adaptors","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115713,"registerId":"commonwealth-F2006B09148-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/60 Amdt 4 - Wing Front Spar Attachment Adaptors","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)  \nDHC-6 (Twin Otter) Series Aeroplanes\n\nAD/DHC-6/60\n\nAmdt 4\n\n  \nWing Front Spar Attachment Adaptors 5/92\n\nApplicability: Model DHC-6 series fitted with aluminium wing to fuselage front adaptor fittings.\n\nRequirement: 1. Inspect fittings in accordance with de Havilland Service Bulletin No 6/476 Revision C.\n\n2. Replace all aluminium fittings with steel fittings in accordance with de Havilland Service Bulletin No 6/500 Revision C. This ends the need for the inspections of para 1 above.\n\nNote: Transport Canada AD CF-85-12R3 refers.\n\nCompliance: 1. Inspect fittings reworked in accordance with de Havilland Service Bulletin No A6/476 at intervals not exceeding 250 hours time in service. Inspect all other aluminium fittings at intervals not exceeding 500 hours time in service.\n\n2. Replace all aluminium fittings with steel fittings before 1 September 1995.\n\nBackground: Fatigue and stress corrosion cracks have been widely reported in the aluminium fittings. Earlier issues of this directive controlled the problem by means of regular inspections, and permitted rework of fittings found to be cracked. Amendment 4 requires mandatory modification \\- the installation of steel fittings \\- in line with the recommendations of Transport Canada’s Aging Aircraft program.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 4 changes scope from inspection-and-rework as a continuing mitigation to a compulsory design modification: it converts an inspection regime (earlier amendments permitting rework) into a mandate to replace all aluminium adaptors with steel fittings by a fixed date, ending the need for further inspections on modified fittings (Background; Requirement; Compliance)."},"complexity_factors":["Clear, limited applicability to DHC-6 series with aluminium front adaptor fittings (Applicability).","Two-step regulatory design: interim inspections plus a firm modification deadline (Requirement; Compliance).","Different inspection intervals depending on prior rework status (250h for reworked fittings; 500h for others) increasing record-keeping complexity (Compliance para 1).","Mandatory retrofit deadline creates upfront cost and logistics for parts, labour and grounding time (Requirement para 2; Compliance para 2).","Dependence on manufacturer service bulletins (de Havilland SB No 6/476 Rev C and No 6/500 Rev C) for technical execution and compliance proof (Requirement).","Reference to related foreign AD (Transport Canada AD CF-85-12R3) may affect interpretation and accepted repairs (Note).","Enforcement and compliance verification lie with the Civil Aviation Safety Authority under Part 39, requiring administrative oversight and record audits (implied by instrument source)."],"plain_english_summary":"Requires inspection of aluminium wing-to-fuselage front adaptor fittings on DHC‑6 (Twin Otter) aeroplanes and mandates replacement of all aluminium fittings with steel fittings by 1 September 1995. Replacing the fittings ends the recurring inspections.\n\nApplies to aircraft owners/operators; it prescribes inspection intervals (250 hours for reworked fittings, 500 hours for other aluminium fittings) and a mandatory modification that shifts costs to operators (parts, labour, downtime) in exchange for removing the ongoing inspection requirement. (Source: Applicability; Requirement; Compliance; Background.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is Amendment 4 to an existing Airworthiness Directive. The document explicitly states that earlier versions required inspections and permitted rework, while Amendment 4 mandates the permanent modification (steel fittings). This represents an evolution within the original safety purpose — moving from monitoring to mandatory replacement — rather than scope creep beyond the original intent of ensuring wing attachment integrity."},"complexity_factors":["Single, specific aircraft model and component targeted","Only 2 substantive requirements (inspect and replace)","Clear compliance deadlines and intervals (250 hours, 500 hours, 1 September 1995)","Minimal cross-referencing (2 service bulletins, 1 Canadian AD reference)","No nested exceptions or conditional logic — straightforward 'inspect until replaced' structure","Short document (approximately 200 words)"],"plain_english_summary":"This is a **safety order for specific aircraft** — the de Havilland DHC-6 Twin Otter series planes that have aluminium (rather than steel) fittings where the wings attach to the fuselage.\n\n**What it does:**\n- **Requires regular inspections** of these aluminium wing attachment fittings to check for cracks caused by metal fatigue and stress corrosion.\n- **Mandates replacement** of all aluminium fittings with stronger steel ones by 1 September 1995.\n- Once the steel fittings are installed, the regular inspections are no longer needed.\n\n**Who it affects:**\n- Owners and operators of DHC-6 Twin Otter aircraft with aluminium wing-to-fuselage front adaptor fittings.\n\n**Why it matters:**\n- Cracks in these fittings pose a serious flight safety risk — the wing could detach from the fuselage. This directive moves from temporary monitoring (inspections) to a permanent fix (steel replacement) following reports of widespread cracking and recommendations from Canada's aviation safety authority."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-60-amdt-4-wing-front-spar-attachment-adaptors","history":"/api/acts/ad-dhc-6-60-amdt-4-wing-front-spar-attachment-adaptors/history","analysis":"/api/acts/ad-dhc-6-60-amdt-4-wing-front-spar-attachment-adaptors/analysis","conflicts":"/api/acts/ad-dhc-6-60-amdt-4-wing-front-spar-attachment-adaptors/conflicts","importantCases":"/api/acts/ad-dhc-6-60-amdt-4-wing-front-spar-attachment-adaptors/important-cases","documents":"/api/acts/ad-dhc-6-60-amdt-4-wing-front-spar-attachment-adaptors/documents"}}