{"id":"F2006B08845","name":"AD/DC4/38 - Lower Main Plane Stringers Inspection","slug":"ad-dc4-38-lower-main-plane-stringers-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52330,"registerId":"commonwealth-F2006B08845-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/38 - Lower Main Plane Stringers Inspection","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/DC4/38 Lower Main Plane Stringers Inspection NK\n\nApplicability: All models.\n\n \n\nRequirement: Inspect for cracking of stringers 18, 19, 20 and 21 between the front and centre lower mainplane spars from wing station 167 to wing station 281 using a radiographic technique acceptable to the Secretary.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\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":5,"scope_assessment":{"changed":false,"description":"The text sets an inspection requirement that applies to all DC-4 models (Applicability). The directive itself does not indicate any amendment or change of scope from prior material; it states the inspection requirement and applicable parts without describing a widening or narrowing of scope."},"complexity_factors":["Technical specificity of the parts and locations to be inspected (stringers 18–21; between front and centre lower mainplane spars; wing stations 167–281) (Requirement).","Delegation of technical discretion to the Secretary by requiring a radiographic technique \"acceptable to the Secretary\", rather than prescribing a specific method (Requirement).","Absence of procedural detail in the text: no inspection intervals, repeat inspections, or corrective actions are specified (Requirement).","Applicability to all models (broad applicability) increases the set of affected operators (Applicability).","Very short, focused text that places practical implementation details on regulators and operators rather than on the instrument itself (Requirement).","Implicit requirement for radiographic capability or access to radiographic providers to fulfil the mandate (implicit from Requirement)."],"plain_english_summary":"What this directive does (mechanically):\n\n- Applies to Douglas DC-4 series aeroplanes (Applicability: All models).\n- Requires an inspection for cracking of lower main plane stringers numbered 18, 19, 20 and 21 between the front and centre lower mainplane spars, covering wing stations 167 to 281, using a radiographic technique acceptable to the Secretary (Requirement).\n\nWho it affects:\n\n- Aircraft owners and operators of DC-4 series aeroplanes, maintenance organisations engaged to perform the inspections, and the regulator (the Secretary) who determines acceptable radiographic technique (Applicability; Requirement).\n\nWhy it matters (purpose-claims and how they map to costs and implementation):\n\n- Purpose-claim (implicit in the text): the directive requires inspection to detect cracking of specific lower mainplane stringers (Requirement).\n\n- Who pays and who decides: inspection costs fall on DC-4 owners/operators; the Secretary decides which radiographic technique is acceptable because the text requires a technique \"acceptable to the Secretary\" rather than prescribing a single method (Requirement).\n\n- Compliance burden and operational effects: the requirement specifies a radiographic inspection over a defined structural area (stringers 18–21, wing stations 167–281) (Requirement). The text does not specify inspection intervals or corrective actions, so operators must seek regulator guidance to determine timing and scheduling. The radiographic requirement implies use of radiographic methods or providers, so operators or maintenance providers must have access to appropriate radiographic capability or subcontract it (Requirement).\n\nCost allocation and information gaps:\n\n- Inspection costs fall on DC-4 owners/operators; any safety benefit from earlier detection of cracking accrues to the broader aviation system (Requirement).\n- The directive does not quantify the frequency of cracking or the cost-benefit ratio of inspection. The text also does not specify inspection intervals, repeat intervals, or corrective actions that should follow a finding of cracking, so practical implementation details are left to the regulator and operators to determine (Requirement).\n\nImplementation risk and discretion:\n\n- The directive delegates discretion over acceptable radiographic technique to the Secretary, rather than specifying a single method in the text. That delegation means operators must obtain or follow the Secretary's guidance on acceptable radiographic methods before carrying out the mandated inspections (Requirement).\n\nPlain practical summary: the instrument mandates a specific radiographic inspection of lower-mainplane stringers 18–21 across wing stations 167–281 on all DC-4 models. It assigns the choice of acceptable radiographic technique to the Secretary and leaves scheduling, intervals and corrective action details unspecified, so operators bear the inspection costs and must obtain regulator guidance on how and when to comply (Applicability; Requirement)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused on a specific airworthiness issue in a particular aircraft type. It has not expanded beyond its original purpose of ensuring structural integrity of DC-4 wing stringers."},"complexity_factors":["Very short document — only 4 substantive lines of regulatory text","No defined terms section — technical terms (stringers, spars, wing stations) are industry-standard aviation terminology","Single, unambiguous requirement with no exceptions or conditions","No cross-references to other legislation or regulations","Straightforward applicability (all models)","Minimal conditional logic — only requirement is that the radiographic technique be 'acceptable to the Secretary'"],"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:**\nOrders owners and operators of **Douglas DC-4 series aircraft** to inspect specific structural parts of the wings for cracks.\n\n**Who it affects:**\nAnyone who owns or operates any model of Douglas DC-4 aeroplane in Australia.\n\n**The specific requirement:**\nOperators must check **stringers 18, 19, 20 and 21** — these are long, thin structural supports that run along the lower surface of the main wings — for cracks. The inspection must cover the area between the front and centre spars (the main structural beams inside the wing) from wing station 167 to wing station 281 (specific measurement points along the wing).\n\n**How to do it:**\nThe inspection must use **radiographic technique** — essentially X-ray or similar imaging — and the method must be approved by the **Secretary** (the senior government official responsible for aviation safety at the time this was issued).\n\n**Why it matters:**\nCracks in wing stringers can weaken the aircraft structure and potentially lead to wing failure. This directive ensures older DC-4 aircraft (which date from the 1940s) remain safe to fly by catching fatigue damage before it becomes dangerous."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-38-lower-main-plane-stringers-inspection","history":"/api/acts/ad-dc4-38-lower-main-plane-stringers-inspection/history","analysis":"/api/acts/ad-dc4-38-lower-main-plane-stringers-inspection/analysis","conflicts":"/api/acts/ad-dc4-38-lower-main-plane-stringers-inspection/conflicts","importantCases":"/api/acts/ad-dc4-38-lower-main-plane-stringers-inspection/important-cases","documents":"/api/acts/ad-dc4-38-lower-main-plane-stringers-inspection/documents"}}