{"id":"F2006B08826","name":"AD/DC4/20 - Rudder Gust Lock Bolt Guard - Installation","slug":"ad-dc4-20-rudder-gust-lock-bolt-guard-installation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52260,"registerId":"commonwealth-F2006B08826-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/20 - Rudder Gust Lock Bolt Guard - 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\n \n\n| AD/DC4/20 | Rudder Gust Lock Bolt Guard - Installation | NK |\n| --- | --- | --- |\n| Document: | 1. Douglas SB (DC4) No. 84, dated 19 December 1947; or |  |\n|  | 2. ANO 105.1.16.2.5.19. |  |\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 \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":4,"scope_assessment":{"changed":false,"description":"The instrument, as presented, establishes a requirement to install a rudder gust‑lock bolt guard on Douglas DC‑4 series aeroplanes and refers implementers to Douglas SB No.84 or ANO 105.1.16.2.5.19 for the technical details (see AD/DC4/20 table and Document references). The text supplied does not indicate any alteration or expansion of that subject compared with the stated title and referenced documents, so there is no evidence in this instrument that the scope has changed from its original stated purpose."},"complexity_factors":["Reference to external technical documents (Douglas SB No.84 and ANO 105.1.16.2.5.19) rather than containing installation detail in the AD itself (see Document references).","Application to an older aircraft type (Douglas DC‑4) where parts, drawings or tooling named in a 1947 service bulletin may be scarce (Douglas SB No.84 dated 19 December 1947).","Regulatory enforcement and record‑keeping obligations flow from Part 39 of the Civil Aviation Regulations 1998, which requires familiarity with ongoing airworthiness processes (header: PART 39 - 105).","Ambiguity in the AD text provided: the AD title and references set the requirement but do not state compliance timeframes or alternative methods in the supplied text (AD/DC4/20 entry; Document references).","Operational impact depends on operator choices (when and how to schedule work), availability of maintenance capacity, and whether authorised alternative methods are needed — factors external to the text but triggered by it (implicit from delegation to external documents)."],"plain_english_summary":"This AD (AD/DC4/20) requires installation of a rudder gust‑lock bolt guard on Douglas DC‑4 series aeroplanes, to be done in accordance with Douglas Service Bulletin No.84 (19 Dec 1947) or ANO 105.1.16.2.5.19. CASA issues and enforces the directive under Part 39.\n\nIt affects DC‑4 owners/operators and maintenance organisations, who must fund and carry out the work, follow the referenced documents for compliance, and retain records."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive for a specific aircraft type. It has not expanded beyond its original purpose of mandating a single safety modification to DC-4 aircraft."},"complexity_factors":["Extremely short document — essentially a single requirement","Only 2 compliance pathways referenced (Douglas SB or ANO)","No defined terms section","No conditional logic or exceptions","Single aircraft type affected (Douglas DC-4 Series)","Single mechanical modification required (bolt guard installation)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nRequires owners and operators of **Douglas DC-4 series aeroplanes** to install a **rudder gust lock bolt guard**.\n\n**Why it matters:**\nA \"gust lock\" is a device that locks an aircraft's control surfaces (like the rudder) while the plane is parked on the ground, preventing wind damage. This directive mandates adding a protective guard around the bolt of this lock — likely to prevent accidental damage, corrosion, or improper engagement that could lead to control issues during flight.\n\n**Who it affects:**\nAnyone who owns, operates, or maintains Douglas DC-4 aircraft in Australia. These are vintage four-engine propeller aircraft (mostly from the 1940s), so this affects historical aircraft operators, museums, and cargo operators still flying these planes.\n\n**Compliance documents:**\nOperators must follow either:\n- Douglas Service Bulletin No. 84 (dated 19 December 1947), or  \n- Air Navigation Order 105.1.16.2.5.19\n\n**In short:** If you fly a DC-4 in Australia, you must fit this specific safety guard to your rudder gust lock mechanism to keep the aircraft airworthy."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-20-rudder-gust-lock-bolt-guard-installation","history":"/api/acts/ad-dc4-20-rudder-gust-lock-bolt-guard-installation/history","analysis":"/api/acts/ad-dc4-20-rudder-gust-lock-bolt-guard-installation/analysis","conflicts":"/api/acts/ad-dc4-20-rudder-gust-lock-bolt-guard-installation/conflicts","importantCases":"/api/acts/ad-dc4-20-rudder-gust-lock-bolt-guard-installation/important-cases","documents":"/api/acts/ad-dc4-20-rudder-gust-lock-bolt-guard-installation/documents"}}