{"id":"F2006B09116","name":"AD/DHC-6/29 - Airframe De-Icing System - Modification","slug":"ad-dhc-6-29-airframe-de-icing-system-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115669,"registerId":"commonwealth-F2006B09116-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/29 - Airframe De-Icing System - 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-6/29 Airframe De-Icing System - Modification 8/71\n\nApplicability: All models with S/Nos. 1 to 289 incorporating airframe de-icing (De Havilland of Canada SOO 6004).\n\n \n\nDocument: De Havilland of Canada SB 6/275. Compliance: Before 1 September 1971.\n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":2034},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"The instrument maintains its original narrow scope as a targeted safety modification for specific early-production Twin Otter aircraft. It has not expanded beyond the original technical remedy for the de-icing system issue."},"complexity_factors":["Very short text with no defined terms or interpretation sections","Single, unambiguous compliance requirement (follow the referenced service bulletin)","Limited applicability restricted to specific aircraft serial numbers","No conditional logic, exceptions, or nested provisions","Technical details incorporated by reference to external document rather than included in text"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by the Civil Aviation Safety Authority (CASA) that has the force of law. It requires owners of specific De Havilland DHC-6 Twin Otter aircraft to modify their airframe de-icing systems.\n\n**Who it affects:**\n- Owners and operators of DHC-6 Twin Otter aeroplanes with serial numbers 1 to 289\n- Only applies to those fitted with the specific De Havilland airframe de-icing system (designated SOO 6004)\n\n**What it requires:**\n- The airframe de-icing system must be modified according to the manufacturer's instructions in **De Havilland Service Bulletin 6/275**\n- This ensures the de-icing equipment meets safety standards\n\n**Compliance:**\n- The modification had to be completed before **1 September 1971**\n\nAirworthiness Directives are issued when safety defects are discovered. Compliance is mandatory — an aircraft cannot legally fly unless all applicable ADs are satisfied."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-29-airframe-de-icing-system-modification","history":"/api/acts/ad-dhc-6-29-airframe-de-icing-system-modification/history","analysis":"/api/acts/ad-dhc-6-29-airframe-de-icing-system-modification/analysis","conflicts":"/api/acts/ad-dhc-6-29-airframe-de-icing-system-modification/conflicts","importantCases":"/api/acts/ad-dhc-6-29-airframe-de-icing-system-modification/important-cases","documents":"/api/acts/ad-dhc-6-29-airframe-de-icing-system-modification/documents"}}