{"id":"F2006B08839","name":"AD/DC4/32 - Master Ignition Switch - Modification","slug":"ad-dc4-32-master-ignition-switch-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52312,"registerId":"commonwealth-F2006B08839-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/32 - Master Ignition Switch - 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/DC4/32 Master Ignition Switch - Modification NK\n\nApplicability: All models.\n\n \n\nRequirement: 1. Remove the master ignition switches from the switch boxes mounted on the header panel and modify the ignition control system so that there are no separate master ignition switches for the port and starboard pairs of engines.\n\n \n\nNote: This Order does not prohibit the fitment of a single master ignition switch for all four engines.\n\n \n\n2. Label each individual engine ignition switch so that no confusion can arise in recognising which engine is connected to the switch; or\n\n \n\nANO 105.1.16.2.5.30.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\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 instrument as presented sets clear technical requirements: removal of separate port/starboard master ignition switches, modification of the ignition control system, allowance for a single master switch, and a labelling requirement or alternative compliance via ANO 105.1.16.2.5.30. The text gives no indication that the scope of these requirements has been altered from an earlier version; there is no internal textual evidence of a scope change."},"complexity_factors":["Technical systems-level change to the ignition control system (Requirement 1) requiring electrical/mechanical work and verification.","Human-factors element: requirement to label individual engine switches clearly (Requirement 2).","Regulatory interpretation: alternative compliance route referenced via ANO 105.1.16.2.5.30 (Requirement 2).","Applicability to all DC4 models means a broad set of aircraft configurations may need tailored modification plans (Applicability: All models).","Allowance for a single master switch creates a design choice that affects retrofit complexity (Note)."],"plain_english_summary":"What this instrument changes, mechanically\n\n- It requires removal of the master ignition switches that are mounted in the header-panel switch boxes and a modification of the aircraft ignition control system so there are no separate master ignition switches for the port and starboard pairs of engines. (Requirement 1)\n- The order explicitly allows a single master ignition switch controlling all four engines to be fitted if desired. (Note)\n- It requires each individual engine ignition switch to be clearly labelled so it is obvious which engine each switch operates; alternatively, compliance may be achieved in accordance with ANO 105.1.16.2.5.30. (Requirement 2 / ANO 105.1.16.2.5.30)\n\nWho this affects and who decides\n\n- The directive applies to all Douglas DC4 series aeroplanes (Applicability: All models). The Civil Aviation Safety Authority (under the Civil Aviation Regulations 1998, Part 39) is the issuing authority for this airworthiness directive (header). The practical duty to implement the changes will fall on the operator or owner of an affected aeroplane because the directive sets mandatory technical requirements to the aircraft equipment (Requirement 1 and Requirement 2).\n\nWhat behaviour changes are required\n\n- Remove separate port and starboard master ignition switches from the header-panel switch boxes and rework the ignition control system so those separate master switches no longer exist. (Requirement 1)\n- Either fit a single master ignition switch for all four engines (permitted by the Note) or ensure each individual engine ignition switch is labelled to prevent confusion. (Note; Requirement 2)\n\nClaimed purpose and how that interacts with costs and incentives\n\n- The instrument’s explicit labelling requirement states its intent to prevent confusion about which engine is connected to which switch (Requirement 2). The order’s mechanical change (eliminating separate port/starboard master switches) plus its labelling requirement together aim to change how crews interact with ignition controls. (Requirement 1; Requirement 2)\n\n- Who pays: the operator/owner must carry out removal, modification and labelling work (Applicability; Requirement 1; Requirement 2). The text does not specify funding, timing, or subsidies.\n\n- Compliance burden and implementation risk: the work involves physical removal of switches and a modification to the ignition control system, which is a systems-level electrical/mechanical change (Requirement 1). That requires technical labour, parts and verification that the modified ignition system functions safely. Incorrect wiring or labelling could create safety or operational risks if not done properly (implicit in Requirement 1 and Requirement 2).\n\n- Choice and constraint: the directive eliminates one permissible configuration (separate port and starboard master switches) but leaves an option (a single master for all four engines) and requires labelling of individual engine switches. That narrows acceptable configurations while retaining a defined alternative. (Requirement 1; Note; Requirement 2)\n\n- Regulatory interpretation and alternative compliance: the instrument references ANO 105.1.16.2.5.30 as an alternative compliance route for the labelling requirement, which introduces a regulatory decision point where an operator or maintainer may rely on that ANO provision instead of literal compliance with the labelling text. The need to interpret that ANO or obtain approval under it could add administrative steps. (Requirement 2; ANO 105.1.16.2.5.30)\n\nTrade-offs, opportunity costs and incentives\n\n- Operators trade the option to use separate port/starboard master switches for the mandated configuration, which may require expenditure and time out of service to implement the modification (Requirement 1).\n- The single-master option preserves some configurational flexibility (Note), which may reduce retrofit cost for operators who prefer that arrangement.\n- The labelling requirement reduces reliance on a particular panel configuration to avoid confusion; meeting that requirement requires attention to human factors when applying labels and may impose small additional material and labour costs. (Requirement 2)\n\nPractical effects to watch for\n\n- Work scheduling and inspection to ensure the ignition system modification is correctly designed and installed (Requirement 1).\n- Clear, unambiguous labelling that matches the modified system configuration so the stated aim of preventing confusion is actually achieved (Requirement 2).\n\nSections cited: Applicability: All models; Requirement 1; Note; Requirement 2; ANO 105.1.16.2.5.30."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This appears to be a discrete, targeted safety directive focused specifically on ignition switch modifications for DC-4 aircraft. There is no evidence of scope creep; it addresses a specific technical aviation safety issue with precise applicability."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 2 substantive requirements with clear alternatives","Single defined applicability (all DC-4 models)","No cross-references to other legislation beyond the parent Civil Aviation Regulations 1998 citation","One permissive note clarifying what remains allowed","Minimal conditional logic — straightforward mandatory action with optional alternative (labelling vs system modification)"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nIt requires owners and operators of **Douglas DC-4 series aircraft** to modify the ignition switch system. Specifically, they must:\n- **Remove** the separate \"master ignition switches\" that currently control the port (left) and starboard (right) pairs of engines\n- **Modify** the ignition system so these paired master switches no longer exist\n- **Label** each individual engine's ignition switch clearly, so pilots can't confuse which switch controls which engine\n\n**Important note:** The directive explicitly allows installing a **single master switch** that controls all four engines at once — it just bans having separate master switches for the left pair and right pair of engines.\n\n**Who it affects:**\nAnyone who owns, operates, or maintains Douglas DC-4 aircraft in Australia.\n\n**Why it matters:**\nThis is a **safety fix**. The original design with separate master switches for port and starboard engine pairs apparently created confusion risks or operational hazards. By removing these paired master switches and ensuring clear labelling of individual engine controls, the directive aims to prevent pilots from accidentally cutting ignition to the wrong engines — a potentially catastrophic error during flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-32-master-ignition-switch-modification","history":"/api/acts/ad-dc4-32-master-ignition-switch-modification/history","analysis":"/api/acts/ad-dc4-32-master-ignition-switch-modification/analysis","conflicts":"/api/acts/ad-dc4-32-master-ignition-switch-modification/conflicts","importantCases":"/api/acts/ad-dc4-32-master-ignition-switch-modification/important-cases","documents":"/api/acts/ad-dc4-32-master-ignition-switch-modification/documents"}}