{"id":"F2006B09129","name":"AD/DHC-6/40 - Wing Struts - Inspection and Modification","slug":"ad-dhc-6-40-wing-struts-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115682,"registerId":"commonwealth-F2006B09129-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/40 - Wing Struts - Inspection and Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  DHC-6 (Twin Otter) Series Aeroplanes\n\n \n\nAD/DHC-6/40 Wing Struts - Inspection and Modification 4/76 Applicability:              All models with S/Nos. 1 to 462, 464, 465, 468, 469, 472, 473, 474, 478 and 481. Document:               De Havilland of Canada SB No. 6/342.\n\nCompliance: 1. Inspect within 120 hours time in service after 31 May 1976.\n\n \n\n2. Modify within 360 hours time in service after 31 May 1976.\n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive issued in 1976 (as indicated by '4/76' in the title). It has not expanded beyond its original narrow purpose of addressing a specific wing strut defect in specific aircraft. Airworthiness Directives are inherently limited in scope by design."},"complexity_factors":["Single, specific technical requirement with clear deadlines","Limited applicability (specific aircraft serial numbers only)","No defined terms section — references external technical document (Service Bulletin) for detailed instructions","Simple conditional structure: inspect by X, modify by Y","No cross-references to other legislation beyond basic enabling regulation (CAR 1998 Part 39)","Extremely short — approximately 100 words of substantive content"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998.\n\n**What it does:** It requires owners and operators of specific De Havilland DHC-6 Twin Otter aircraft to:\n- **Inspect** the wing struts (structural supports connecting the wings to the fuselage) within 120 flight hours after 31 May 1976\n- **Modify** those wing struts within 360 flight hours after the same date\n\n**Who it affects:** Operators of DHC-6 Twin Otter aircraft with specific serial numbers: 1 through 462, plus individual serial numbers 464, 465, 468, 469, 472, 473, 474, 478, and 481.\n\n**Why it matters:** Wing struts are critical structural components. This directive addresses a potential safety defect that could affect aircraft structural integrity. Compliance is **legally mandatory** — operators cannot fly these aircraft without completing these actions within the specified timeframes.\n\n**Key details:**\n- **Legal basis:** Civil Aviation Regulations 1998, Part 39\n- **Technical reference:** De Havilland Service Bulletin No. 6/342 (this contains the actual engineering instructions)\n- **Effective date trigger:** 31 May 1976 (making this a historical directive, though it remains on the books for affected aircraft still in service)"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The supplied text defines a limited scope: it applies only to the listed DHC-6 serial numbers and requires inspection and modification within specified hours-in-service (Applicability; Compliance: 1–2). There is no indication in the supplied text that the applicability or required actions have been altered from the instrument as presented."},"complexity_factors":["Narrow and explicit applicability list (serial numbers) reduces scope ambiguity (Applicability).","Simple, fixed compliance timeframes in hours-in-service (120 and 360 hours) are straightforward to measure (Compliance: 1–2).","Technical details are not included in the directive and are delegated to an external service bulletin, requiring cross-reference (Document).","Compliance depends on availability of the referenced service bulletin and required parts/skills, introducing operational implementation risk (Document).","The directive provides no explicit statement of the underlying safety issue or expected outcome, requiring inference from the title."],"plain_english_summary":"This airworthiness directive applies to specified De Havilland DHC‑6 (Twin Otter) aircraft and mandates a wing‑strut inspection within 120 hours and a prescribed wing‑strut modification within 360 hours time‑in‑service after 31 May 1976. Operators and maintenance organisations must follow De Havilland Service Bulletin No. 6/342 for technical details; owners/operators bear compliance costs and manage scheduling and downtime to meet the mandatory timeframes."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-40-wing-struts-inspection-and-modification","history":"/api/acts/ad-dhc-6-40-wing-struts-inspection-and-modification/history","analysis":"/api/acts/ad-dhc-6-40-wing-struts-inspection-and-modification/analysis","conflicts":"/api/acts/ad-dhc-6-40-wing-struts-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-dhc-6-40-wing-struts-inspection-and-modification/important-cases","documents":"/api/acts/ad-dhc-6-40-wing-struts-inspection-and-modification/documents"}}