{"id":"F2006B09107","name":"AD/DHC-6/2 - Fuel System Crossfeed Thermal Relief - Modification","slug":"ad-dhc-6-2-fuel-system-crossfeed-thermal-relief-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115660,"registerId":"commonwealth-F2006B09107-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/2 - Fuel System Crossfeed Thermal Relief - 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-6/2 Fuel System Crossfeed Thermal Relief - Modification\n\nApplicability: All models with S/Nos. 1 to 14.\n\n \n\nDocument:  De Havilland of Canada Mod. Bulletin 6/1032. Compliance: Before 1 September 1971.\n\n\n5/67\n","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":2102},"content_quality":"ok","complexity_score":1,"scope_assessment":{"changed":false,"description":"This is the original issuance of the directive (issued May 1967), maintaining its original narrow scope targeting only the fuel system thermal relief modification on early-production Twin Otter aircraft serial numbers 1-14."},"complexity_factors":["Extremely concise directive (under 50 words of operative text)","Single, unambiguous applicability criterion (serial numbers 1-14 only)","One discrete compliance action referencing a single external document","No definitions section, exceptions, or conditional logic","Fixed, historical compliance date with no recurring inspection requirements"],"plain_english_summary":"**What it does:** This Airworthiness Directive (AD) orders a safety modification to the fuel system on early model De Havilland DHC-6 Twin Otter aircraft. Specifically, it requires updating the **crossfeed thermal relief** system — a safety mechanism that prevents dangerous pressure or temperature build-up in the fuel pipes that transfer fuel between tanks.\n\n**Who it affects:** Owners and operators of DHC-6 Twin Otter aircraft with serial numbers 1 through 14 (the first 14 planes built).\n\n**What you must do:** Carry out the modification exactly as described in **De Havilland of Canada Modification Bulletin 6/1032** before **1 September 1971**.\n\n**Why it matters:** The directive prevents potential fuel system failures that could arise from thermal expansion issues in the crossfeed lines, ensuring these early-model aircraft remain safe to operate."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-2-fuel-system-crossfeed-thermal-relief-modification","history":"/api/acts/ad-dhc-6-2-fuel-system-crossfeed-thermal-relief-modification/history","analysis":"/api/acts/ad-dhc-6-2-fuel-system-crossfeed-thermal-relief-modification/analysis","conflicts":"/api/acts/ad-dhc-6-2-fuel-system-crossfeed-thermal-relief-modification/conflicts","importantCases":"/api/acts/ad-dhc-6-2-fuel-system-crossfeed-thermal-relief-modification/important-cases","documents":"/api/acts/ad-dhc-6-2-fuel-system-crossfeed-thermal-relief-modification/documents"}}