{"id":"F2006B08823","name":"AD/DC4/18 - Gust Lock Safety Latch - Installation","slug":"ad-dc4-18-gust-lock-safety-latch-installation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52252,"registerId":"commonwealth-F2006B08823-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/18 - Gust Lock Safety Latch - Installation","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/DC4/18 Gust Lock Safety Latch - Installation NK\n\nDocument: 1. Douglas SB (DC4) No. 79, dated 21 August 1947; or\n\n \n\n2. FAA AD 47-42-1; or\n\n \n\n3. ANO 105.1.16.2.5.17.\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":6,"scope_assessment":{"changed":false,"description":"The supplied text does not indicate any change in scope from an earlier instrument or intent. It identifies a requirement (installation of a gust-lock safety latch) for Douglas DC4 series aeroplanes and points to three documents as means of compliance. There is no material in the text provided that shows the directive’s scope has been expanded, narrowed, or otherwise altered from an original intent."},"complexity_factors":["Brevity of the instrument text and absence of operative details (no installation steps, deadlines, or explicit compliance requirements in the supplied text).","Reliance on external, historical documents (Douglas SB No.79 dated 1947 and FAA AD 47-42-1) that must be consulted to determine actual technical requirements.","Multiple alternative compliance paths listed, requiring interpretation and choice by operators or maintainers.","Lack of specified compliance timeframe or record-keeping requirements in the text provided, creating potential for regulator discretion and inconsistent implementation.","Potential ambiguity about who bears costs and how installation interacts with current maintenance programmes (not resolved in the supplied text).","Possible interpretive difficulty due to vintage references and differing formats or standards across the referenced documents."],"plain_english_summary":"What this instrument does (mechanically)\n\n- This is an airworthiness directive titled \"AD/DC4/18 Gust Lock Safety Latch - Installation\" that applies to Douglas DC4 series aeroplanes. The directive requires the installation of a gust-lock safety latch (the title identifies the required intervention).\n\n- The directive does not include full installation instructions in the text supplied. Instead it lists three external documents that establish how compliance may be achieved: 1) Douglas SB (DC4) No. 79, dated 21 August 1947; or 2) FAA AD 47-42-1; or 3) ANO 105.1.16.2.5.17 (see Document list in the source). Compliance therefore depends on following one of those referenced documents.\n\nWho is affected and who decides\n\n- The persons and organisations that operate or maintain Douglas DC4 series aeroplanes are the parties required to implement the installation (they must cause the aircraft to meet the directive).\n\n- The directive itself points operators to the three specified documents as the means of compliance. The civil aviation authority or an authorised maintenance organisation will decide whether an operator’s chosen compliance action (for example, following one of the three documents) satisfies the directive when inspecting, approving maintenance, or issuing airworthiness documentation.\n\nCosts, incentives and behaviour changes\n\n- The immediate mechanical effect is a requirement to install a gust-lock safety latch; that requires parts and labour and will therefore create direct costs for operators (installation work, possible aircraft downtime). The document supplied does not specify cost-sharing, time limits, or who pays; those practical and financial details are therefore left to operators and maintainers to resolve in carrying out the installation.\n\n- Because the directive points to three alternative documents for compliance, operators have the option of following any one of them. That creates flexibility in the method of compliance but also a need to consult and interpret older or external documents (including a 1947 Douglas service bulletin and a historic FAA AD).\n\nImplementation, compliance burden and administrative discretion\n\n- The directive’s compliance mechanism is cross-reference: operators must follow one of the listed documents. The supplied text does not state a compliance deadline, record-keeping requirements, or inspection regime. Those elements will be determined by the contents of the referenced documents and by the regulator’s enforcement and approval processes.\n\n- Administrative discretion arises because the directive does not itself set procedural details; authorised inspectors or the regulator will need to judge whether an operator’s actions meet the directive when reviewing maintenance records or issuing approvals.\n\nOfficial rationale and trade-offs\n\n- The text provided does not include an explicit statement of the safety rationale; the title indicates the subject (gust-lock safety latch installation) and the listed documents will likely contain explanatory material. The trade-offs inherent in the requirement are practical: installing the latch increases maintenance and parts costs and may cause downtime, while the intended effect (improved control-surface security when parked or during ground operations) would be achieved if the installation matches the referenced instructions.\n\nSource citations\n\n- The directive title and its compliance route are taken directly from the instrument text: \"AD/DC4/18 Gust Lock Safety Latch - Installation NK\" and the Document list: \"1. Douglas SB (DC4) No. 79, dated 21 August 1947; or 2. FAA AD 47-42-1; or 3. ANO 105.1.16.2.5.17.\""},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a narrow, technical airworthiness directive focused on a specific safety modification for a single aircraft type. It has not expanded beyond its original purpose of ensuring gust lock safety on DC-4 aircraft."},"complexity_factors":["Extremely short document (approximately 150 words)","Only one substantive requirement: install a gust lock safety latch","Three alternative compliance pathways provided (Douglas SB, FAA AD, or ANO)","No defined terms section","No conditional logic or nested exceptions","Single aircraft type applicability (Douglas DC-4 series)","No cross-references to other legislation beyond the three compliance documents"],"plain_english_summary":"This is a **Civil Aviation Safety Authority (CASA) Airworthiness Directive** for **Douglas DC-4 series aeroplanes**.\n\n**What it does:**\nThis directive requires the installation of a **gust lock safety latch** on DC-4 aircraft.\n\n**What is a gust lock?**\nA \"gust lock\" is a device that locks an aircraft's control surfaces (like the rudder, elevators, and ailerons) in place when the plane is parked on the ground. This prevents wind gusts from banging the control surfaces around and damaging them.\n\n**Why a safety latch matters:**\nThe safety latch ensures the gust lock stays properly engaged. Without it, the gust lock could fail or disengage unexpectedly, allowing wind to damage the aircraft's control systems.\n\n**Who it affects:**\n- Owners and operators of Douglas DC-4 series aircraft\n- Maintenance engineers working on these aircraft\n\n**Compliance documents:**\nTo comply with this directive, you must follow one of these documents:\n- **Douglas Service Bulletin (DC4) No. 79** (dated 21 August 1947), **or**\n- **FAA AD 47-42-1** (the US Federal Aviation Administration's equivalent directive), **or**\n- **ANO 105.1.16.2.5.17** (an Australian National Order)\n\n**Why it matters:**\nThis is a **safety-critical requirement**. Proper gust lock installation prevents ground damage to aircraft controls, which could otherwise lead to expensive repairs or, if undetected, potentially dangerous flight control failures."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-18-gust-lock-safety-latch-installation","history":"/api/acts/ad-dc4-18-gust-lock-safety-latch-installation/history","analysis":"/api/acts/ad-dc4-18-gust-lock-safety-latch-installation/analysis","conflicts":"/api/acts/ad-dc4-18-gust-lock-safety-latch-installation/conflicts","importantCases":"/api/acts/ad-dc4-18-gust-lock-safety-latch-installation/important-cases","documents":"/api/acts/ad-dc4-18-gust-lock-safety-latch-installation/documents"}}