{"id":"F2006B08817","name":"AD/DC4/12 - Main Undercarriage Door - Rework","slug":"ad-dc4-12-main-undercarriage-door-rework","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52231,"registerId":"commonwealth-F2006B08817-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/12 - Main Undercarriage Door - Rework","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/DC4/12 | Main Undercarriage Door - Rework | NK |\n| --- | --- | --- |\n| Document: | 1. Douglas SB (DC4) No. 15, dated 30 September 1946; or |  |\n|  | 2. ANO 105.1.16.2.5.11, 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":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue Airworthiness Directive focused specifically on DC-4 main undercarriage door rework. It has not expanded beyond its original technical safety purpose. ADs are typically narrow, technical instruments and this follows that pattern precisely."},"complexity_factors":["Extremely short document — essentially a single table entry with two alternative compliance documents referenced","Only one substantive requirement (rework main undercarriage doors)","Two alternative technical references provided for compliance (Douglas SB or ANO)","No defined terms section, no conditional logic, no exceptions","No cross-references to other legislation beyond the parent Civil Aviation Regulations 1998","Standardised AD format — boilerplate structure with minimal variation"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order — issued by Australia's Civil Aviation Safety Authority (CASA) for **Douglas DC-4 series aircraft**.\n\n**What it does:**\nThis directive (numbered AD/DC4/12) requires owners and operators of DC-4 aeroplanes to perform **rework on the main undercarriage doors** (the landing gear doors). The work must follow one of two technical documents:\n- **Douglas Service Bulletin No. 15** dated 30 September 1946; or\n- **ANO 105.1.16.2.5.11, Issue 2** (an Airworthiness Notice Order — essentially an official technical instruction).\n\n**Who it affects:**\nAnyone who owns, operates, or maintains Douglas DC-4 aircraft in Australia. These are vintage four-engine propeller aircraft from the 1940s, now mostly used for cargo, aerial firefighting, or heritage flying.\n\n**Why it matters:**\nAirworthiness Directives are **legally binding**. If you don't comply, you cannot fly the aircraft. This particular directive addresses a specific structural or mechanical issue with the main landing gear doors — likely a fatigue, wear, or design flaw discovered after years of operation. Non-compliance means the aircraft is grounded."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The supplied instrument text sets an AD requiring rework of the main undercarriage door for Douglas DC4 series aeroplanes and lists two documents to be used. The text provided does not show amendments or a change in scope from an earlier version; based on the available material, the scope remains the rework requirement as evidenced by AD/DC4/12 and its document references."},"complexity_factors":["AD relies on external technical documents (Service Bulletin and ANO) rather than containing full operative requirements.","One referenced document is historic (Douglas SB No. 15, dated 30 September 1946), which may require additional interpretation or locating archival material.","The provided text does not include compliance timing, acceptance of alternative methods, or details of enforcement, requiring cross-reference to regulator practice under Part 39.","Operational impacts (downtime, parts, labour) depend on technical detail absent from the AD text, increasing implementation uncertainty.","Regulatory framework (CASA enforcement under Civil Aviation Regulations 1998, Part 39) must be understood to determine formal compliance obligations."],"plain_english_summary":"What this instrument does mechanically:\n\n- This is an Airworthiness Directive (AD) issued under Part 39 of the Civil Aviation Regulations 1998 (Civil Aviation Safety Authority schedule of ADs). The AD is titled \"AD/DC4/12 — Main Undercarriage Door - Rework\" and applies to Douglas DC4 series aeroplanes (see header: \"Douglas DC4 Series Aeroplanes\").\n- The AD refers operators and maintenance organisations to two external documents for the required work: (1) Douglas Service Bulletin (DC4) No. 15, dated 30 September 1946; or (2) ANO 105.1.16.2.5.11, Issue 2. The AD text supplied does not reproduce the operative technical steps or a compliance schedule; it directs readers to those referenced documents for the rework instructions. (Source: AD/DC4/12; Document list.)\n\nWho this affects and who pays:\n\n- Aircraft owners and operators of Douglas DC4 series aeroplanes on the Australian register must follow this AD and the referenced documents. They bear the direct costs: parts, labour, and aircraft downtime needed to carry out the rework.\n- Approved maintenance organisations or qualified engineers perform the rework and will invoice owners/operators for the work and any associated testing.\n- The Civil Aviation Safety Authority (CASA) is the regulator that issues and enforces ADs under Part 39; CASA decides compliance requirements and may record or audit compliance (Civil Aviation Regulations 1998, Part 39). (Source: header and statutory citation.)\n\nWhy it matters (stated purpose and practical effects):\n\n- The title and placement in the schedule of Airworthiness Directives indicate the AD is intended to require a rework of the main undercarriage door on DC4 aircraft. The AD therefore changes maintenance obligations for affected aircraft by making a particular rework standard the mandatory reference for compliance.\n- Practically, compliance will change operator behaviour: scheduling maintenance/downtime, contracting maintenance providers, and keeping whatever compliance records CASA requires. The immediate financial effect falls on owners/operators; operations may be disrupted while rework is carried out. (Source: AD title and references.)\n\nImplementation, costs, incentives, and risks:\n\n- Compliance mechanics: operators must implement the rework according to one of the two referenced documents. Because the AD does not include detailed steps or a compliance timeframe in the supplied text, operators must consult the listed Service Bulletin or ANO to know the exact tasks and timing. (Source: Document list in AD/DC4/12.)\n- Costs and incentives: owners/operators pay for parts, labour and downtime. Maintenance organisations are incentivised to supply the required work. There is an administrative burden in locating and applying an older service bulletin (dated 1946) or the specified ANO issue.\n- Regulatory discretion and substitution: the AD points to alternate documents (SB No.15 or ANO 105.1.16.2.5.11 Issue 2). The supplied text does not specify whether alternative methods of compliance (AMOC) are acceptable; any such discretion would rest with CASA under Part 39 but is not set out in the provided instrument. (Source: AD text and statutory header.)\n- Implementation risk: the technical direction is external to the AD and relies on historical documents; that can create ambiguity or require interpretative work by maintenance providers. There is an operational risk (aircraft out of service) while work is completed.\n\nTrade-offs and opportunity costs:\n\n- The immediate trade-off for owners/operators is paying for and scheduling the rework versus continuing current operations. The AD centralises the required technical standard by reference rather than embedding it in the AD text; this reduces the AD’s length but requires users to obtain and apply separate documents.\n\nKey source citations: AD/DC4/12 (title and application to Douglas DC4 series); Document references — Douglas SB (DC4) No. 15 (30 Sept 1946) and ANO 105.1.16.2.5.11 Issue 2; Civil Aviation Regulations 1998, Part 39 (statutory basis and schedule of ADs)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-12-main-undercarriage-door-rework","history":"/api/acts/ad-dc4-12-main-undercarriage-door-rework/history","analysis":"/api/acts/ad-dc4-12-main-undercarriage-door-rework/analysis","conflicts":"/api/acts/ad-dc4-12-main-undercarriage-door-rework/conflicts","importantCases":"/api/acts/ad-dc4-12-main-undercarriage-door-rework/important-cases","documents":"/api/acts/ad-dc4-12-main-undercarriage-door-rework/documents"}}