{"id":"F2006B09125","name":"AD/DHC-6/37 - Side Seat Rail Attachment Rivets - Inspection and Modification","slug":"ad-dhc-6-37-side-seat-rail-attachment-rivets-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115678,"registerId":"commonwealth-F2006B09125-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/37 - Side Seat Rail Attachment Rivets - Inspection and 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)  DHC-6 (Twin Otter) Series Aeroplanes\n\n \n\n# AD/DHC-6/37  Side Seat Rail Attachment Rivets - Inspection and Modification\n\nApplicability: All models with S/Nos. 136 to 350, 353, 356, 360 to 366 and 368. Document:  De Havilland of Canada SB No. 6/302.\n\n# 12/73\n\nCompliance: 1. For aeroplanes with side facing seats: Within 200 hours time in service after 1 January 1974 or before 1 April 1974 whichever occurs first.\n\n \n\n2. For aeroplanes with forward or aft facing seats: Within 1200 hours time in service after 1 January 1974 or before 1 January 1975 whichever occurs first.\n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused specifically on seat rail rivet inspection and modification for a limited fleet of DHC-6 aircraft. It has not expanded beyond its original technical safety purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined applicability criteria (aircraft serial numbers and seat orientation)","Simple binary compliance structure based on seat configuration","No cross-references to other legislation beyond the parent regulation (Civil Aviation Regulations 1998, Part 39)","No nested exceptions or conditional logic — straightforward deadlines based on flight hours and calendar dates","Single technical reference to manufacturer service bulletin (De Havilland SB No. 6/302)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nOrders owners and operators of certain **De Havilland DHC-6 Twin Otter aeroplanes** (specific serial numbers 136–350, 353, 356, 360–366, and 368) to inspect and modify the **rivets that attach side seat rails** to the aircraft structure.\n\n**Why it matters:**\nFaulty or loose seat rail attachment rivets could compromise passenger safety during flight, particularly in turbulence or emergency situations. The directive ensures these critical structural fasteners meet safety standards.\n\n**Who must comply:**\n- **Aircraft with side-facing seats:** Must complete the work within 200 flight hours after 1 January 1974, or before 1 April 1974 — whichever comes first.\n- **Aircraft with forward or aft-facing seats:** Must complete the work within 1,200 flight hours after 1 January 1974, or before 1 January 1975 — whichever comes first.\n\n**Key point:** This is not optional. Compliance is legally mandatory under the Civil Aviation Regulations 1998, Part 39."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The text presents a single AD with a defined applicability and two compliance timelines. It does not reference prior versions or amendments nor indicate any change from an earlier scope. Based on the supplied text alone, there is no indication that the AD's scope was changed from an earlier intent."},"complexity_factors":["Specific serial-number applicability narrows scope but requires operators to check serial numbers (Applicability).","Two-tier compliance schedule based on seat orientation with different hour and calendar-date triggers increases scheduling complexity (Compliance 1 and 2).","'Whichever occurs first' wording requires monitoring both flight hours and calendar deadlines (Compliance 1 and 2).","Technical method is cross-referenced to a manufacturer service bulletin rather than detailed in the AD, requiring access to and reliance on another document (Document: De Havilland of Canada SB No. 6/302).","The AD is prescriptive with no discretionary alternative stated, so compliance choices are limited and operational planning is required (Compliance)."],"plain_english_summary":"### What this directive does\nThis is an Airworthiness Directive (AD) that requires inspection and any necessary modification of the side seat rail attachment rivets on specified De Havilland DHC-6 (Twin Otter) aeroplanes. The AD points operators to De Havilland of Canada Service Bulletin No. 6/302 for the technical details (Document: De Havilland of Canada SB No. 6/302).\n\n### Which aircraft are affected\nAll DHC-6 models with the following serial numbers: 136 to 350, 353, 356, 360 to 366 and 368. (Applicability)\n\n### Who decides and who must act\nThe Civil Aviation Safety Authority (under the Civil Aviation Regulations, Part 39) issues the AD and sets the mandatory requirement. Aircraft owners/operators of the affected serial-numbered aeroplanes must comply.\n\n### What operators must do and by when\n- For aeroplanes with side-facing seats: inspect and modify the rivets within 200 hours time-in-service after 1 January 1974, or before 1 April 1974, whichever occurs first. (Compliance 1)\n- For aeroplanes with forward- or aft-facing seats: inspect and modify the rivets within 1,200 hours time-in-service after 1 January 1974, or before 1 January 1975, whichever occurs first. (Compliance 2)\n\nThe phrasing \"whichever occurs first\" means operators must comply by the earlier of the two limits (hours-in-service or the calendar date). The AD itself prescribes the timing; the Service Bulletin named provides the technical method for inspection/modification.\n\n### Who pays and what it costs (mechanics, not estimates)\nAircraft owners/operators bear the direct costs of carrying out the inspections and any required modifications, and the indirect costs of aircraft downtime while work is performed. The AD does not state funding or subsidy arrangements (Document: De Havilland of Canada SB No. 6/302). (Applicability; Compliance)\n\n### Compliance burden and operational effects\n- The AD creates a mandatory scheduling requirement tied to both flight hours and specific calendar deadlines (Compliance 1 and 2). That imposes planning and maintenance workload on operators to meet the earlier of the two triggers.\n- The AD is prescriptive about the need to inspect and modify rivets; no discretionary alternative is provided in the text. Operators must follow the directive and the referenced Service Bulletin to fulfil it. (Document: De Havilland of Canada SB No. 6/302)\n\n### Implementation and risk trade-offs to note\n- Differential deadlines: aircraft with side-facing seats face a much shorter compliance window (200 hours or 1 April 1974) than aircraft with forward/aft seats (1,200 hours or 1 January 1975). That concentrates near-term workload and costs on operators of side-facing-seat configurations. (Compliance 1 and 2)\n- The AD cross-references a manufacturer service bulletin for the technical procedure; compliance therefore requires access to that document and to parts/skills to perform the modification. (Document: De Havilland of Canada SB No. 6/302)\n\n### Stated purpose vs. mechanical effect\nThe directive requires inspection/modification of a specific component (side seat rail attachment rivets) on specified serial-numbered aeroplanes within set timeframes. The AD's mechanical effect is to force inspection and correction of those rivets on affected aircraft. The text itself does not include a narrative explaining broader policy goals; the action is implemented through mandatory compliance deadlines and a technical cross-reference. (Applicability; Compliance; Document: De Havilland of Canada SB No. 6/302)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-37-side-seat-rail-attachment-rivets-inspection-and-modification","history":"/api/acts/ad-dhc-6-37-side-seat-rail-attachment-rivets-inspection-and-modification/history","analysis":"/api/acts/ad-dhc-6-37-side-seat-rail-attachment-rivets-inspection-and-modification/analysis","conflicts":"/api/acts/ad-dhc-6-37-side-seat-rail-attachment-rivets-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-dhc-6-37-side-seat-rail-attachment-rivets-inspection-and-modification/important-cases","documents":"/api/acts/ad-dhc-6-37-side-seat-rail-attachment-rivets-inspection-and-modification/documents"}}