{"id":"F2006B09073","name":"AD/DHC-3/24 - Main Landing Gear Fuselage Attachment Bolts","slug":"ad-dhc-3-24-main-landing-gear-fuselage-attachment-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52848,"registerId":"commonwealth-F2006B09073-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-3/24 - Main Landing Gear Fuselage Attachment Bolts","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)  DHC-3 (Otter) Series Aeroplanes\n\n \n\nAD/DHC-3/24 Main Landing Gear Fuselage Attachment Bolts 3/69\n\nApplicability: All models.\n\n \n\nRequirement: Remove and inspect using a magnetic particle method main landing gear to fuselage attachment bolts P/Ns C3U72-3 and C3U142-5 for cracking particularly around the grease outlet hole.\n\n \n\nCompliance: Within 100 hours time in service after 15 April 1969 and thereafter at intervals not exceeding 500 hours time in service.\n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive's scope as stated applies to all DHC-3 models and specifically to the two identified bolt part numbers. The text does not indicate any expansion or narrowing relative to an earlier version; it sets a clear, time‑based inspection regime for those bolts (Applicability; Requirement; Compliance)."},"complexity_factors":["Narrow technical scope: targets two specific part numbers (C3U72-3 and C3U142-5). (Requirement)","Prescriptive inspection method specified (magnetic particle), reducing procedural ambiguity. (Requirement)","Clear compliance timing: initial within 100 hours after a stated date, recurring at ≤500 hours. (Compliance)","Requires removal of parts for inspection, which raises practical maintenance complexity (access, downtime) despite simple regulatory text. (Requirement)","No detailed acceptance criteria or corrective-action steps included in the text, which may require operator judgment or reference to other documents. (Requirement)"],"plain_english_summary":"This Airworthiness Directive (AD/DHC-3/24) requires operators of DHC-3 (Otter) series aeroplanes to remove specific main landing gear-to-fuselage attachment bolts and inspect them for cracks. The bolts named are part numbers C3U72-3 and C3U142-5, and inspections must focus on cracking around the grease outlet hole. The inspection method specified is magnetic particle inspection. (Requirement)\n\nWho it affects\n- All DHC-3 (Otter) aircraft: the AD is applicable to all models. (Applicability)\n- Aircraft owners and operators are the parties who must arrange and pay for the removal and inspection as part of maintaining the aircraft airworthiness. The AD requires action on the aircraft, so the operator or their maintenance provider bears the direct cost and downtime. (Requirement, Compliance)\n\nWhat it requires, mechanically\n- Remove the specified bolts from the aircraft and perform a magnetic particle inspection looking for cracking, in particular around the grease outlet hole. (Requirement)\n- Do the initial inspection within 100 hours time in service after 15 April 1969, and repeat the inspection at intervals not exceeding 500 hours time in service thereafter. (Compliance)\n\nWhy it matters (stated as a mechanical objective)\n- The AD targets possible cracking of the main landing gear attachment bolts. Cracked bolts could compromise the attachment between landing gear and fuselage; the AD addresses that risk by mandating removal and non‑destructive inspection. (Requirement)\n\nPractical effects, incentives and trade-offs\n- Who pays: the aircraft owner/operator pays for removal, inspection, any repairs or bolt replacements, and for aircraft downtime. (Requirement, Compliance)\n- Compliance burden: inspections require removal of the bolts and access to magnetic particle inspection facilities and qualified personnel. The recurring inspection interval (every 500 hours TIS after the initial 100‑hour window) creates an ongoing maintenance task to track and schedule. (Requirement, Compliance)\n- Decision authority and discretion: the directive prescribes the parts to be inspected, the defect area of concern (around the grease outlet hole), and the inspection method (magnetic particle). That limits discretion about method and target parts. (Requirement)\n- Implementation risk and effectiveness: the AD relies on magnetic particle inspection to detect cracking; the effectiveness depends on the quality of the inspection (equipment, technique, inspector skill) and complete removal/access to the bolt. The AD does not specify detailed acceptance criteria or mandatory corrective actions in this text excerpt. (Requirement)\n- Opportunity costs and operational impact: recurring inspections consume maintenance labour and aircraft time. Operators must balance this recurring cost against the risk of in-service bolt failure. (Compliance)\n\nSource citations: Applicability; Requirement; Compliance."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused on a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original purpose of ensuring the airworthiness of DHC-3 Otter landing gear attachment bolts."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 specific part numbers to identify","Single, straightforward inspection requirement","Simple compliance schedule (initial + recurring intervals)","No defined terms section","No cross-references to other legislation","No conditional logic or exceptions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to all models of the **de Havilland Canada DHC-3 Otter** aircraft.\n\n**What it requires:**\nOwners and operators must **remove and inspect specific bolts** that attach the main landing gear (the wheels) to the aircraft's fuselage (the main body). The bolts in question are part numbers C3U72-3 and C3U142-5.\n\n**What to look for:**\nInspectors must use a **magnetic particle inspection** (a technique that detects cracks in metal by applying magnetic fields and iron particles) to check for **cracking**, especially around the grease outlet hole on these bolts.\n\n**When to do it:**\n- **First inspection:** Within 100 hours of flying time after 15 April 1969\n- **Repeat inspections:** Every 500 hours of flying time thereafter\n\n**Why it matters:**\nThese bolts are critical structural components. If they crack and fail, the landing gear could collapse during takeoff, landing, or taxiing — potentially causing a serious accident. This AD was issued to prevent catastrophic failure of the landing gear attachment."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-3-24-main-landing-gear-fuselage-attachment-bolts","history":"/api/acts/ad-dhc-3-24-main-landing-gear-fuselage-attachment-bolts/history","analysis":"/api/acts/ad-dhc-3-24-main-landing-gear-fuselage-attachment-bolts/analysis","conflicts":"/api/acts/ad-dhc-3-24-main-landing-gear-fuselage-attachment-bolts/conflicts","importantCases":"/api/acts/ad-dhc-3-24-main-landing-gear-fuselage-attachment-bolts/important-cases","documents":"/api/acts/ad-dhc-3-24-main-landing-gear-fuselage-attachment-bolts/documents"}}