{"id":"F2006B08821","name":"AD/DC4/16 - Tailplane Outer Hinge Bracket - Modification","slug":"ad-dc4-16-tailplane-outer-hinge-bracket-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52246,"registerId":"commonwealth-F2006B08821-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/16 - Tailplane Outer Hinge Bracket - 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 DC4 Series Aeroplanes\n\n \n\nAD/DC4/16 Tailplane Outer Hinge Bracket - Modification NK\n\nDocument: 1. Douglas SB (DC4) No. 73, dated 23 September 1947; or\n\n \n\n2. FAA AD 47-33-1; or\n\n \n\n3. ANO 105.1.16.2.5.15, Issue 2.\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\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The supplied text contains a single airworthiness directive requiring a tailplane outer hinge bracket modification and names three documents that specify how to carry out the work. The text does not indicate any amendment, expansion, or narrowing of scope relative to an earlier or original instrument. No change of scope is stated in the supplied material."},"complexity_factors":["Directive text is short and contains no technical steps; substantive requirements are contained in three externally referenced documents.","References include an historical service bulletin dated 23 September 1947, which may be harder to locate or interpret.","Applicability is narrow (only Douglas DC-4 series), but the precise compliance method depends on which referenced document is used.","Lack of timing, inspection intervals or certification detail in the AD itself increases reliance on maintenance organisations to interpret and apply the referenced documents.","Regulatory placement under Part 39 - 105 means enforceability is statutory, requiring formal compliance despite limited detail in the AD text."],"plain_english_summary":"What this instrument changes mechanically:\n\n- It requires a specific modification to the tailplane outer hinge bracket on Douglas DC-4 series aeroplanes. The modification must be carried out in accordance with one of the following referenced technical documents: Douglas Service Bulletin (DC4) No. 73 dated 23 September 1947; FAA Airworthiness Directive 47-33-1; or ANO 105.1.16.2.5.15, Issue 2.\n\nWho it affects:\n\n- Owners and operators of Douglas DC-4 series aeroplanes, and the maintenance organisations that service them. The directive appears in the Civil Aviation Safety Authority schedule of airworthiness directives under Part 39 - 105.\n\nWhy it matters (mechanical and compliance effects):\n\n- Mechanically, the AD mandates modification of a structural hinge component on the tailplane. Compliance requires performing the work listed in one of the three referenced documents.\n\n- Who pays: aircraft owners/operators bear the cost of parts, labour, and any aircraft downtime needed to carry out the modification.\n\n- Who decides and enforces: the Civil Aviation Safety Authority issues and enforces the airworthiness directive; the technical steps to comply are set out in the referenced service/airworthiness documents.\n\nPractical implementation points, trade-offs and risks (source-grounded):\n\n- The directive provides three alternate sources for the required modification, so operators can comply by following any one of those documents.\n\n- One referenced document is a 1947 Douglas service bulletin (dated 23 September 1947). The vintage and multiplicity of references may affect how easily operators can obtain the required instructions or parts.\n\n- Compliance imposes a direct operational cost (labour, parts, downtime) on affected operators. The text does not specify costs, intervals, inspection outcomes, or approval pathways beyond naming the three documents.\n\n- The AD text itself contains no further technical detail; the concrete work and inspection steps are contained in the referenced documents. That places the substantive technical discretion and compliance detail in those external documents rather than in the AD text.\n\nSources cited in the directive (as listed in the instrument):\n\n- Douglas SB (DC4) No. 73, dated 23 September 1947\n- FAA AD 47-33-1\n- ANO 105.1.16.2.5.15, Issue 2\n\nNote: The AD is titled \"AD/DC4/16 Tailplane Outer Hinge Bracket - Modification\" with identifier \"NK\". The text supplied contains only the directive title and the three listed documents; no further procedural or timing details are included in the supplied text."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a historical Airworthiness Directive from 1947 (based on the referenced documents). It addresses a specific, narrow safety issue with a single aircraft component. There is no indication of scope creep; it remains focused on its original purpose of mandating a structural modification to prevent tailplane hinge bracket failure."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only one substantive requirement: modify the tailplane outer hinge bracket","Three alternative compliance documents referenced, but no cross-referencing within the text itself","No defined terms section","No conditional logic or exceptions","Standard template format for Airworthiness Directives","Single aircraft type and single component addressed"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) for **Douglas DC-4 series aircraft**.\n\n**What it does:**\n- Requires owners and operators of DC-4 planes to modify the **tailplane outer hinge bracket** — a structural component that helps connect the horizontal tail (the small wings at the back of the plane) to the fuselage.\n- The modification is mandatory to address a known safety issue with this bracket.\n\n**Who it affects:**\n- Anyone who owns, operates, or maintains Douglas DC-4 aircraft in Australia.\n\n**Why it matters:**\n- The tailplane is critical for controlling the aircraft's pitch (nose up/down). A failure in the hinge bracket could lead to loss of control.\n- This AD ensures Australian DC-4 operators follow the same safety standard originally issued by the manufacturer (Douglas) in 1947 and later adopted by the US FAA.\n\n**Compliance documents:**\nOperators must follow one of these three approved documents to make the modification:\n1. Douglas Service Bulletin No. 73 (September 1947)\n2. US FAA Airworthiness Directive 47-33-1\n3. Australian National Order 105.1.16.2.5.15, Issue 2"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-16-tailplane-outer-hinge-bracket-modification","history":"/api/acts/ad-dc4-16-tailplane-outer-hinge-bracket-modification/history","analysis":"/api/acts/ad-dc4-16-tailplane-outer-hinge-bracket-modification/analysis","conflicts":"/api/acts/ad-dc4-16-tailplane-outer-hinge-bracket-modification/conflicts","importantCases":"/api/acts/ad-dc4-16-tailplane-outer-hinge-bracket-modification/important-cases","documents":"/api/acts/ad-dc4-16-tailplane-outer-hinge-bracket-modification/documents"}}