{"id":"F2006B08951","name":"AD/DH114/4 - Aileron Differential Pulley Stud - Modification","slug":"ad-dh114-4-aileron-differential-pulley-stud-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52596,"registerId":"commonwealth-F2006B08951-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DH114/4 - Aileron Differential Pulley Stud - 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)  DH114 (Heron) Series Aeroplanes\n\n \n\nAD/DH114/4 Aileron Differential Pulley Stud - Modification NK\n\nApplicability: All Series 1B and 2. Document: 1. DH Heron Mod. No. 475; or\n\n2. ANO 105.1.14.17.5.4.\n\n \n\nCompliance: Before 28 March 1955.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\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 directive, as supplied, applies specifically to all DH114 (Heron) Series 1B and 2 aeroplanes and requires modification per the two listed documents to be completed before 28 March 1955 (Applicability; Document; Compliance). The text gives no indication that this instrument expands or narrows scope relative to an earlier or different instrument; based on the supplied text alone, the scope is confined to those series and that modification and appears not to have changed from its stated content."},"complexity_factors":["Narrow applicability: limited to DH114 (Heron) Series 1B and 2 (Applicability).","Single, fixed compliance deadline: before 28 March 1955 (Compliance).","Prescriptive reliance on externally referenced technical documents rather than detailed procedures in the directive (Document).","No technical detail or alternative compliance pathways included in the supplied text (Document; Compliance).","Short textual scope with limited legal language reduces interpretive ambiguity but requires consultation of external documents for execution (Document)."],"plain_english_summary":"### What this instrument does, mechanically\n\n- It requires a specific modification to the aileron differential pulley stud on certain de Havilland Heron aeroplanes. The required work must follow one of the two listed documents: either \"DH Heron Mod. No. 475\" or \"ANO 105.1.14.17.5.4\" (Document: 1–2).  \n- The rule applies to \"All Series 1B and 2\" of the DH114 (Heron) aeroplanes (Applicability).  \n- Operators must complete the modification on affected aircraft before 28 March 1955 (Compliance).\n\nThis directive is issued under the Civil Aviation Regulations 1998, Part 39 as a Schedule of Airworthiness Directives published by the Civil Aviation Safety Authority (header information).\n\n### Who it affects\n\n- Owners and operators of DH114 (Heron) Series 1B and Series 2 aeroplanes. They are the parties required to carry out the modification identified in the listed documents (Applicability; Document; Compliance).\n\n### Why it matters (stated purpose and practical implications)\n\n- The instrument mandates a hardware modification by a set date. The directive itself does not include technical detail or an explicit statement of the hazard or failure mode it addresses in the supplied text; it simply prescribes the modification documents to be used (Document). Any claimed safety objective should be treated as the issuer's stated rationale rather than a proved outcome, because the directive text here does not set out underlying findings.\n\n- Who pays: The owners/operators of the affected aircraft must arrange and pay for the modification work; the directive places the compliance obligation on them (Applicability; Compliance).\n\n- Who decides and exercises discretion: The directive is a prescriptive requirement issued through the Civil Aviation Safety Authority process (header). Discretion in this text is limited: compliance must follow one of the two specified documents and be completed before the stated date (Document; Compliance). The text does not grant alternative means of compliance or a notice-and-approval mechanism within the excerpt provided.\n\n- Behaviour change required: Affected operators must schedule the modification, obtain the required documents, secure parts and labour, perform the modification in accordance with the listed document, and record compliance by the deadline (Document; Compliance).\n\n### Costs, incentives and implementation trade-offs (mechanical description)\n\n- Direct costs are the resources needed to implement the modification: components, technician labour, and aircraft downtime. Those costs fall on the aircraft operators/owners because the directive makes them the obligated party (Applicability; Compliance).  \n- Incentives: Compliance is compulsory under the airworthiness directive; operators face a legal obligation to complete the work by the date given (Compliance).  \n- Compliance burden and administrative effect: The directive references external documents for the detailed procedure rather than embedding procedures in the directive itself, which concentrates technical detail in the referenced modifications (Document). That reduces technical detail in the directive but requires operators to obtain and follow the external document(s).\n\n### Implementation risks and practical notes\n\n- The instrument sets a fixed compliance date (before 28 March 1955). The directive text does not specify an approval path for alternative solutions, extensions, or how compliance is to be evidenced in this excerpt (Compliance; Document).  \n- Because the directive relies on named modification documents, successful compliance depends on access to and correct interpretation of those documents (Document).\n\n(References in parentheses point to the corresponding lines in the supplied text: Applicability; Document; Compliance; header identifying the regulatory basis.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused on one specific mechanical modification. It has not expanded beyond its original purpose of mandating a safety fix for the aileron differential pulley stud on specific Heron aircraft models."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 2 defined applicability criteria (aircraft series)","Single compliance requirement with clear deadline","No nested exceptions or conditional logic","No cross-references to other legislation beyond the enabling regulations and two technical documents","Straightforward command structure: applicability → requirement → deadline"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998.\n\n**What it does:**\nIt requires owners and operators of specific de Havilland Heron aircraft (Series 1B and 2) to carry out a **modification to the aileron differential pulley stud**. This is a mechanical fix to a part of the aircraft's control system that helps the plane bank and turn safely.\n\n**Who it affects:**\nAnyone who owns or operates a DH114 Heron Series 1B or Series 2 aircraft in Australia.\n\n**What must be done:**\nOperators must complete the modification described in either:\n- **DH Heron Modification No. 475**, or  \n- **Air Navigation Order 105.1.14.17.5.4**\n\n**When:**\nThe work had to be finished **before 28 March 1955**.\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety instructions. If an operator ignored this directive, their aircraft would not be considered airworthy (legally safe to fly). This particular directive addresses a specific mechanical defect in the aileron control system that could affect the aircraft's handling or safety."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dh114-4-aileron-differential-pulley-stud-modification","history":"/api/acts/ad-dh114-4-aileron-differential-pulley-stud-modification/history","analysis":"/api/acts/ad-dh114-4-aileron-differential-pulley-stud-modification/analysis","conflicts":"/api/acts/ad-dh114-4-aileron-differential-pulley-stud-modification/conflicts","importantCases":"/api/acts/ad-dh114-4-aileron-differential-pulley-stud-modification/important-cases","documents":"/api/acts/ad-dh114-4-aileron-differential-pulley-stud-modification/documents"}}