{"id":"F2006B08828","name":"AD/DC4/22 - Bus Bar Protector Plate - Installation","slug":"ad-dc4-22-bus-bar-protector-plate-installation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52266,"registerId":"commonwealth-F2006B08828-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/22 - Bus Bar Protector Plate - 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/DC4/22 | Bus Bar Protector Plate - Installation | NK |\n| --- | --- | --- |\n| Document: | 1. Douglas SB (DC4) No. 90, dated 29 March 1948; or |  |\n|  | 2. ANO 105.1.16.2.5.21, 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 \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":2,"scope_assessment":{"changed":false,"description":"The supplied AD text sets a single, narrow requirement (installation of a bus bar protector plate on Douglas DC4 series aeroplanes) and references two documents for the technical procedure (Douglas SB No. 90 and ANO 105.1.16.2.5.21 Issue 2). There is no information in the supplied text indicating a change in scope from any prior or original intent. The AD as given is targeted and relies on the referenced documents for detail; no expanded or reduced applicability is stated in the material provided."},"complexity_factors":["Directive text is very short and states a single required action (installation of a bus bar protector plate). (source: AD/DC4/22 title).","Substantive technical detail is not in the AD itself but in two external documents, increasing reliance on cross-references for compliance specifics. (source: Document list).","One referenced document is historical (Douglas SB No. 90, dated 29 March 1948), which may make locating or interpreting the technical guidance harder. (source: Document list).","The AD text supplied contains no explicit compliance timeframe, alternative compliance procedures, or enforcement mechanisms, creating potential ambiguity about implementation steps. (source: AD text).","Applicability is narrow (limited to Douglas DC4 series), which reduces breadth but concentrates effects on a small, specialised group. (source: AD heading)."],"plain_english_summary":"This document is an airworthiness directive titled \"AD/DC4/22 — Bus Bar Protector Plate - Installation.\" It applies to Douglas DC4 series aeroplanes and directs that a bus bar protector plate be installed. The directive is published under the heading \"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - ... SCHEDULE OF AIRWORTHINESS DIRECTIVES\" (source: heading of the instrument).\n\nWhat the directive does, mechanically\n- It requires installation of a bus bar protector plate on Douglas DC4 series aeroplanes (see AD identifier: AD/DC4/22). \n- The detailed installation instructions or procedures are those set out in either: (a) Douglas Service Bulletin (DC4) No. 90, dated 29 March 1948; or (b) ANO 105.1.16.2.5.21, Issue 2 (see the Document list under AD/DC4/22).\n\nWho this affects\n- Owners and operators of Douglas DC4 series aeroplanes. \n- Maintenance organisations and personnel who carry out modifications or repairs to DC4-series aeroplanes, since they must follow the referenced documents when installing the plate.\n\nWhy it matters (as stated and how that translates into practical effects)\n- As an airworthiness directive, it is issued under the Civil Aviation Regulations framework and therefore imposes a mandatory technical requirement on affected aircraft (source: heading and AD identifier). The stated action is installation of a bus bar protector plate (AD/DC4/22).\n- The immediate costs of compliance (paid by aircraft owners/operators) are the cost of the protector plate, any associated parts, labour to install it, and aircraft downtime while work is arranged and completed (the AD itself gives the requirement; the referenced documents contain the installation detail and so determine scope of labour and parts). \n- The AD shifts decision-making about the technical content of the fix to the two referenced documents: operators comply by following the procedures and specifications in Douglas SB No. 90 or ANO 105.1.16.2.5.21 Issue 2 (see Document list). That means the practical compliance burden and the exact technical steps are set out outside the AD itself.\n\nIncentives, trade-offs and implementation risks (stated as mechanisms)\n- Incentives: affected parties are incentivised to carry out the installation because the AD establishes a regulatory requirement for DC4 operators (source: AD/DC4/22 heading). The time, parts and labour required create direct costs to operators.\n- Trade-offs and opportunity costs: operators must allocate maintenance resources and downtime to perform the installation instead of other uses; the precise magnitude depends on the installation complexity set out in the referenced documents.\n- Compliance burden and clarity risk: the AD is brief and relies on two external documents for technical detail. If those documents are difficult to obtain, are old (one is dated 29 March 1948), or are ambiguous, that can increase compliance cost and regulatory friction (source: Document list). \n- Administrative discretion: the AD binds operators to the installation requirement; implementation details are determined by the referenced documents rather than by additional material in the AD itself (source: AD text and Document list). The AD text contains no further exceptions, timing, or alternative means of compliance within the supplied text.\n\nConcrete behavioural change required\n- Operators/maintenance organisations must install the bus bar protector plate on affected DC4 aircraft in accordance with the procedures/specifications set out in the referenced documents (see AD/DC4/22 and Document list). The AD text supplied does not specify compliance timeframes, alternative compliance methods, or enforcement steps; those may be set elsewhere in the regulatory framework or in the referenced documents.\n\nKey source pointers\n- AD identifier and requirement: \"AD/DC4/22 — Bus Bar Protector Plate - Installation\" (AD heading).\n- Technical instructions referenced: \"Douglas SB (DC4) No. 90, dated 29 March 1948\" and \"ANO 105.1.16.2.5.21, Issue 2\" (Document list under AD/DC4/22)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a vintage Airworthiness Directive from 1948 (referenced via the Douglas Service Bulletin date). It has not expanded beyond its original narrow purpose: mandating a specific electrical safety modification to DC-4 aircraft. The scope remains precisely targeted at the bus bar protector plate installation."},"complexity_factors":["Extremely short document — essentially a single requirement","Only two compliance pathways specified (Douglas SB or ANO reference)","No defined terms section","No conditional logic, exceptions, or nested provisions","Single technical requirement (install one specific component)","No cross-references to other legislation beyond the two source documents"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) for **Douglas DC-4 aircraft** — a type of four-engine propeller plane that was common in the 1940s-1960s.\n\n**What it does:**\nThis directive requires owners and operators of DC-4 aeroplanes to install a **\"bus bar protector plate.\"** A bus bar is a metal strip or bar that conducts electricity inside the aircraft's electrical system. The protector plate is a safety device that prevents electrical faults or short circuits.\n\n**Who it affects:**\n- Owners and operators of Douglas DC-4 series aircraft\n- Maintenance organisations servicing these aircraft\n- The Civil Aviation Safety Authority (CASA), which enforces compliance\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety orders. If you don't comply, you cannot legally fly the aircraft. This particular AD addresses a specific electrical safety issue identified by the manufacturer (Douglas) back in 1948. Even though the DC-4 is a vintage aircraft, these directives remain in force for any still flying today — typically in cargo, firefighting, or heritage aviation roles.\n\n**Compliance documents:**\nTo satisfy this AD, you must follow either:\n- Douglas Service Bulletin No. 90 (dated 29 March 1948), **or**\n- Air Navigation Order 105.1.16.2.5.21, Issue 2"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-22-bus-bar-protector-plate-installation","history":"/api/acts/ad-dc4-22-bus-bar-protector-plate-installation/history","analysis":"/api/acts/ad-dc4-22-bus-bar-protector-plate-installation/analysis","conflicts":"/api/acts/ad-dc4-22-bus-bar-protector-plate-installation/conflicts","importantCases":"/api/acts/ad-dc4-22-bus-bar-protector-plate-installation/important-cases","documents":"/api/acts/ad-dc4-22-bus-bar-protector-plate-installation/documents"}}