{"id":"F2006B08788","name":"AD/DC3/11 - Tailplane Rib - Modification","slug":"ad-dc3-11-tailplane-rib-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52128,"registerId":"commonwealth-F2006B08788-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC3/11 - Tailplane Rib - 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)  Douglas DC3 Series Aeroplanes\n\n \n\nAD/DC3/11 Tailplane Rib - Modification NK\n\nDocument: 1. Douglas SB (C47A) No. 5; or\n\n \n\n2. ANOs Part 100 Appendix “A” Notice 7/9; or 3. ANO 105.1.16.1.5.11.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted airworthiness directive focused specifically on a structural modification for one aircraft type (DC-3 series). It has not expanded beyond its original safety purpose."},"complexity_factors":["Extremely short document (approximately 150 words)","No defined terms section","No conditional logic or exceptions","Simple directive structure: identifies aircraft type, specifies modification, lists three alternative compliance documents","No cross-references to other legislation beyond the three technical documents","Single operational requirement with no sub-conditions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) for **Douglas DC-3 series aircraft**.\n\n**What it does:**\n- Requires a specific **modification to the tailplane rib** (a structural component at the rear of the aircraft that helps control pitch/stability)\n- Mandates compliance with one of three technical documents:\n  1. Douglas Service Bulletin (C47A) No. 5; or\n  2. Air Navigation Orders (ANOs) Part 100 Appendix \"A\" Notice 7/9; or\n  3. ANO 105.1.16.1.5.11\n\n**Who it affects:**\n- Owners and operators of Douglas DC-3 series aeroplanes (including military variants like the C-47)\n- Maintenance organisations servicing these aircraft\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety orders. This AD addresses a specific structural concern with the tailplane rib that, if unaddressed, could affect aircraft safety. Compliance is mandatory — you cannot legally fly the aircraft without completing this modification or ensuring it has already been done."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The supplied text is a single airworthiness directive that requires modification of the tailplane rib and cites three specific documents for the technical work. The document does not indicate any change from a prior instrument or a previous scope; no earlier version or comparative text is provided in the supplied material, so there is no evidence in this text that the scope has changed from an original intent."},"complexity_factors":["The AD itself is short and non-technical, but it delegates the substantive technical requirements to three external documents (Douglas SB (C47A) No. 5; ANOs Part 100 Appendix 'A' Notice 7/9; ANO 105.1.16.1.5.11), increasing procedural complexity","Technical nature of the work (a structural tailplane rib modification) requires certified maintenance personnel and possibly specialised parts or tooling","Multiple alternative compliance documents create interpretive complexity if the documents differ in scope or method","The AD header contains the marker 'NK', which is present in the supplied text and creates uncertainty about omitted details (for example, compliance time or explanatory notes) not included in the excerpt","Coordination needs: operators must schedule downtime, manage logistics for parts and maintenance resources, and update airworthiness records — all of which add operational complexity"],"plain_english_summary":"What this instrument does, mechanically:\n\n- The document titled \"AD/DC3/11 Tailplane Rib - Modification NK\" is an airworthiness directive that requires modification work on the tailplane rib of Douglas DC3 series aeroplanes. The directive directs operators to carry out the modification in accordance with one of three specified source documents: (1) Douglas Service Bulletin (C47A) No. 5; (2) ANOs Part 100 Appendix \"A\" Notice 7/9; or (3) ANO 105.1.16.1.5.11 (see the Document list in the AD). [AD/DC3/11 title; Document list]\n\nWho is affected and who decides:\n\n- Affected parties are the registered owners and operators of Douglas DC3 series aircraft, and the maintenance organisations or engineers who will perform the modification. The Civil Aviation Safety Authority (as issuer of the AD) sets the requirement to comply with the specified documents. The operator/maintenance organisation is responsible for arranging and paying for the work and for keeping maintenance records showing compliance. [AD/DC3/11 title; Document list]\n\nHow compliance works, practically:\n\n- Operators must have the tailplane rib modified following the procedures and specifications in one of the three named documents. That typically means booking maintenance, sourcing parts or kits if required by the referenced document, and using appropriately certificated maintenance personnel. Completion will need to be recorded in the aircraft maintenance logbooks as evidence of compliance. [Document list]\n\nCosts, incentives and trade-offs (mechanical and economic effects):\n\n- Who pays: the owner/operator pays for parts, labour, and downtime while the aircraft is out of service. [AD/DC3/11 title; Document list]\n- Incentives: operators are compelled to modify to maintain lawful airworthiness and continued operation; they may prioritise the compliance option that minimises cost and downtime among the three referenced documents. [Document list]\n- Opportunity costs: time out of service and maintenance resources assigned to the AD are diverted from other work or revenue-generating flights. [AD/DC3/11 title]\n\nCompliance burden and implementation risk:\n\n- Burden: compliance requires locating and following one of the referenced technical documents, arranging certified maintenance, obtaining parts or kits if specified, and recording the work. This creates direct administrative and operational costs for operators and maintenance providers. [Document list]\n- Discretion and potential ambiguity: the AD lists three possible documents as acceptable compliance methods. Where those documents differ in detail, a responsible person (operator or authorised engineer) and the regulator will need to determine which method has been applied and whether it satisfies the AD. The AD title includes the marker \"NK\", which appears in the AD header; the presence of that marker in the supplied text introduces uncertainty about any additional explanatory material or compliance dates not shown here. [AD/DC3/11 title; Document list]\n\nConcrete behaviour changes required:\n\n- Owners/operators must schedule and complete the tailplane rib modification according to one of the listed documents, engage certificated maintenance personnel, bear the direct cost, and update maintenance records to show compliance. The regulator will treat non-compliance as an airworthiness matter requiring corrective action. [AD/DC3/11 title; Document list]\n\nNotes on source and limits of this summary:\n\n- This summary is based only on the text supplied in the AD, which identifies the action (tailplane rib modification) and lists three documents that contain the technical instructions. The supplied text does not include the technical steps, compliance times, cost estimates, or any enforcement detail; those details will be contained in the referenced documents.\n"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc3-11-tailplane-rib-modification","history":"/api/acts/ad-dc3-11-tailplane-rib-modification/history","analysis":"/api/acts/ad-dc3-11-tailplane-rib-modification/analysis","conflicts":"/api/acts/ad-dc3-11-tailplane-rib-modification/conflicts","importantCases":"/api/acts/ad-dc3-11-tailplane-rib-modification/important-cases","documents":"/api/acts/ad-dc3-11-tailplane-rib-modification/documents"}}