{"id":"F2006B08844","name":"AD/DC4/37 - Spar Web - Inspection","slug":"ad-dc4-37-spar-web-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52326,"registerId":"commonwealth-F2006B08844-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/37 - Spar Web - Inspection","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nDouglas DC4 Series Aeroplanes\n\nAD/DC4/37 Spar Web \\- Inspection NK\n\nApplicability: All models.\n\nRequirement: 1. Inspect the spar web structure in accordance with the following procedure:-\n\n    1.1. Open the quick-opening type inspection doors in the bottom of the outer wing and centre section surfaces forward of the front spar and aft of the centre spar.\n\n    1.2. Inspect the spar web structure for loose rivets, cracks, seam defects and other irregularities, particular attention being paid to signs of fuel leakage.\n\n2. Repair cracks in the spar web which occur in the area covered by Douglas SB No. (C54)205, or in any other area of the spar, in accordance with the following Douglas Drawings:-\n\n5354811 “Service Rework \\- Station 463, Outer Wing, Centre Spar” 3344236 \"Repair - Integral Tank Spar Web Cracks”; or\n\nANOs Part 100, Appendix “A” Notice No. 7/25; or FAA AD 47-27-2; or\n\nANO 105.1.16.2.6.6.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The source text sets out a clear, limited scope: inspection of spar web structure on all Douglas DC‑4 models and repair where cracks are found, using specified drawings or regulatory notices. The instrument itself does not indicate any change of scope from an earlier intent within the text provided."},"complexity_factors":["Technical specificity of the inspection (accessing quick‑opening inspection doors and examining particular spar locations) (Requirement 1.1–1.2).","Multiple cross‑references to external technical and regulatory documents for repair methods (two Douglas drawings, ANOs, FAA AD) creating dependency on external materials (Requirement 2).","Applicability to all models of the Douglas DC‑4 series increases operational scope and number of affected operators (Applicability).","Operational constraints and potential limited visibility because inspection is conducted via specified inspection doors (Requirement 1.1–1.2).","Constrained repair choices — repairs must follow the named drawings or notices — which raises administrative and approval complexity for alternative methods (Requirement 2)."],"plain_english_summary":"What this instrument does, mechanically:\n\n- It requires inspection of the spar web structure on Douglas DC‑4 series aeroplanes (applicability: all models). (Applicability; Requirement 1)\n- The inspection procedure specified is to open the quick‑opening inspection doors in the underside of the outer wing and centre section in the locations described (forward of the front spar and aft of the centre spar) and examine the spar web for loose rivets, cracks, seam defects and other irregularities, with particular attention to signs of fuel leakage. (Requirement 1.1–1.2)\n- If cracks are found in the areas covered by Douglas Service Bulletin No. (C54)205 or elsewhere in the spar, repairs must be carried out in accordance with specified Douglas drawings (5354811 and 3344236) or in accordance with one of the listed regulatory/airworthiness documents (ANOs Part 100 Appendix A Notice No. 7/25; FAA AD 47‑27‑2; or ANO 105.1.16.2.6.6). (Requirement 2)\n\nWho this affects and who decides:\n\n- Aircraft owners and operators of Douglas DC‑4 series aeroplanes must perform the inspection and, where necessary, carry out repairs as specified. (Applicability; Requirement 1–2)\n- The technical content and acceptable repair methods are determined by the referenced technical drawings and regulatory notices; compliance is achieved only by following those specified items. (Requirement 2)\n\nWhy it matters (stated purpose and operational effect):\n\n- The directive targets structural defects in the spar web (loose rivets, cracks, seam defects) and specifically flags fuel leakage as a point of attention. The mechanical effect is to require active inspection and mandated repair pathways when defects are found. (Requirement 1.2; Requirement 2)\n\nPractical implications, incentives, trade‑offs and implementation considerations:\n\n- Who pays: aircraft owners/operators bear the cost and operational impact of carrying out the inspection and any required repairs, including potential downtime to access inspection doors and complete repairs. (Requirement 1.1–2)\n- Compliance burden: the directive prescribes specific access steps (opening quick‑opening doors) and inspection targets, and it prescribes repair methods by reference to particular drawings and regulatory notices, which requires access to those documents and competence to apply them. (Requirement 1.1–1.2; Requirement 2)\n- Limits on discretion and on choice of repair method: repairs must conform to the named Douglas drawings or the listed ANO/FAA documents; that constrains repair options to those methods unless an alternate method is authorised under the regulatory framework. (Requirement 2)\n- Effects on maintenance market and providers: maintenance work will flow to providers able to perform the specified inspections and repairs and to those with access to and authority to use the referenced drawings and notices. Independent providers lacking that access or approved methods may need to obtain them to compete for the work. (Requirement 1–2)\n- Implementation risk / scope of inspection: the inspection is carried out through the quick‑opening doors described, so detectability is limited to what is visible and reachable from those openings unless additional access is provided. (Requirement 1.1–1.2)\n- Cross‑jurisdictional reference: the directive accepts repair methods listed in a foreign authority’s AD (FAA AD 47‑27‑2) as an option, creating a reliance on externally published technical solutions alongside Australian Notices of Order (Requirement 2).\n\nNet procedural effect:\n\n- Operators must inspect the spar web as described and, if cracks or other defects are present, repair them according to one of the prescribed technical documents. The regulator enforces compliance by reference to these procedures and documents. (Applicability; Requirement 1–2)"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive (AD) — a targeted safety instrument with a single, specific purpose. It has not expanded beyond its original intent of ensuring DC-4 wing structural integrity. The scope remains precisely limited to inspection and repair requirements for the spar web structure."},"complexity_factors":["Short, single-purpose directive (approximately 200 words)","Only 1 defined term implicitly used ('spar web' — explained through context)","Simple sequential structure (inspection procedure followed by repair requirements)","Minimal cross-referencing (references to specific Douglas Service Bulletins, Drawings, and FAA/ANO equivalents rather than legislative cross-references)","No conditional logic or nested exceptions — straightforward 'inspect and repair if found' structure","Technical aviation terminology assumes specialist knowledge but is standard for the field"],"plain_english_summary":"This is a **safety inspection rule** for old Douglas DC-4 aeroplanes (the kind used in the 1940s-50s). It requires airlines and aircraft owners to **check the wing structure for dangerous cracks and fuel leaks**.\n\n**What it does:**\n- **Mandates regular inspections** of the \"spar web\" — a critical internal wing structure that holds the wings together\n- **Requires visual checks** through special inspection panels for loose rivets, cracks, seam defects, and fuel leaks\n- **Specifies repair methods** if cracks are found, using official Douglas aircraft drawings or equivalent American safety directives\n\n**Who it affects:**\n- Anyone operating or maintaining Douglas DC-4 series aircraft in Australia\n- Licensed aircraft maintenance engineers performing these inspections\n\n**Why it matters:**\nCracks in the spar web can cause **catastrophic wing failure**. This directive prevents accidents by catching structural fatigue before it becomes dangerous. The DC-4 is an elderly aircraft design, so ongoing structural monitoring is essential for safety."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-37-spar-web-inspection","history":"/api/acts/ad-dc4-37-spar-web-inspection/history","analysis":"/api/acts/ad-dc4-37-spar-web-inspection/analysis","conflicts":"/api/acts/ad-dc4-37-spar-web-inspection/conflicts","importantCases":"/api/acts/ad-dc4-37-spar-web-inspection/important-cases","documents":"/api/acts/ad-dc4-37-spar-web-inspection/documents"}}