{"id":"F2008L01627","name":"AD/DHC-6/76 - Floatplane Float to Chassis Bolts","slug":"ad-dhc-6-76-floatplane-float-to-chassis-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":73874,"registerId":"commonwealth-F2008L01627-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"DHC-6 (Twin Otter) Series Aeroplanes","sectionType":"division","heading":"DHC-6 (Twin Otter) Series Aeroplanes","content":"### DHC-6 (Twin Otter) Series Aeroplanes\n\n| AD/DHC-6/76 | Floatplane Float to Chassis Bolts | 6/2008 |\n| ----------- | --------------------------------- | ------ |\n\n| Applicability: | Model DHC-6 Floatplanes, all Series, equipped with Canadian Aircraft Products Model 12000A or 12000B Floats installed prior to Float Serial No. 71.                                                                                                                                                                                                                                                              |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Action in accordance with de Havilland Service Bulletin 6/296 Revision A, dated11 May 1973, or later Transport Canada approved revision.The inspections required by this Directive may be discontinued upon incorporation of either de Havilland Modification 6/1464 described in de Havilland Service Bulletin 6/296 Revision A, or equivalent approved modification.Note: Transport Canada AD CF-73-11 refers. |\n| Compliance:    | At intervals not to exceed 75 flight hours; until modified.                                                                                                                                                                                                                                                                                                                                                      |\n|                | This Airworthiness Directive becomes effective on 5 June 2008.                                                                                                                                                                                                                                                                                                                                                   |\n| Background:    | The actions required by this Directive are intended to prevent loosening and subsequent pull-out failure of certain float to chassis bolts.                                                                                                                                                                                                                                                                      |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n23 April 2008","sortOrder":0},{"sectionNumber":"AD/DHC-6/76","sectionType":"part","heading":"AD/DHC-6/76","content":"## AD/DHC-6/76","sortOrder":1},{"sectionNumber":"Floatplane Float to Chassis Bolts","sectionType":"part","heading":"Floatplane Float to Chassis Bolts","content":"## Floatplane Float to Chassis Bolts","sortOrder":2},{"sectionNumber":"6/2008","sectionType":"part","heading":"6/2008","content":"## 6/2008","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive maintains an explicit, focused scope consistent with its stated safety objective: inspect specified float-to-chassis bolts on DHC‑6 aircraft with particular float models/serials and permit discontinuation only after an approved modification (Applicability; Requirement; Background). There is no indication in the text of an expansion beyond that original intent; it references the supporting service bulletin and Transport Canada AD for the same issue (Requirement; Note)."},"complexity_factors":["Narrow applicability: only DHC-6 floatplanes with CAP Model 12000A/12000B floats installed prior to Float Serial No. 71 (Applicability).","Recurring operational requirement: inspections mandated at intervals not to exceed 75 flight hours until modification is fitted — creates ongoing maintenance scheduling and tracking (Compliance).","Modification as compliance end-point: inspections may cease only after incorporation of de Havilland Modification 6/1464 or equivalent approved modification — requires parts/approval and aircraft downtime (Requirement).","Procedural reliance on an external service bulletin and foreign AD: work must follow de Havilland Service Bulletin 6/296 Rev A or later Transport Canada–approved revision; introduces dependency on manufacturer and TC documentation/approvals (Requirement; Note: Transport Canada AD CF-73-11 refers).","Low regulatory discretion: directive prescribes inspection interval and acceptable compliance path, leaving limited regulator-level interpretation (Requirement; Compliance).","Compliance cost and operator burden: recurring labour/inspection costs and potential modification expense and downtime accrue to aircraft owners/operators (Compliance; Requirement).","Safety objective clearly stated: intended to prevent loosening and pull-out failure of certain float-to-chassis bolts, giving a focused risk mitigation target (Background)."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of DHC‑6 (Twin Otter) floatplanes fitted with Canadian Aircraft Products Model 12000A or 12000B floats (installed before Float Serial No. 71) to perform inspections of the float-to-chassis bolts at intervals not exceeding 75 flight hours, following de Havilland Service Bulletin 6/296 Rev A (or later Transport Canada‑approved revision). The inspections may be stopped only after incorporating the approved modification. The stated purpose is to prevent bolt loosening and pull-out failures."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive targeting a specific mechanical defect in a specific aircraft type. The scope remains tightly focused on bolt inspection requirements for DHC-6 floatplanes with identified float configurations, consistent with the original purpose of addressing the safety risk described in the background."},"complexity_factors":["Single, specific technical requirement referencing an external document (Service Bulletin 6/296 Revision A)","Clear applicability criteria (specific aircraft model, float model, and serial number cutoff)","Simple compliance structure (recurring inspection at fixed interval until modification)","No nested exceptions or conditional logic — only one exemption path (installation of Modification 6/1464)","Minimal defined terms (only implicit technical terms like 'flight hours' and 'float serial number')","Short document length (approximately 200 words of substantive content)"],"plain_english_summary":"This CASA Airworthiness Directive mandates recurring inspections of the bolts that secure older Canadian Aircraft Products floats to certain de Havilland DHC‑6 Twin Otter seaplanes, using the specified de Havilland Service Bulletin every 75 flight hours until a permanent modification is installed. It affects owners/operators of affected Twin Otters (floats installed before Serial No. 71) and aims to prevent bolt loosening and potential float detachment during water operations."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-76-floatplane-float-to-chassis-bolts","history":"/api/acts/ad-dhc-6-76-floatplane-float-to-chassis-bolts/history","analysis":"/api/acts/ad-dhc-6-76-floatplane-float-to-chassis-bolts/analysis","conflicts":"/api/acts/ad-dhc-6-76-floatplane-float-to-chassis-bolts/conflicts","importantCases":"/api/acts/ad-dhc-6-76-floatplane-float-to-chassis-bolts/important-cases","documents":"/api/acts/ad-dhc-6-76-floatplane-float-to-chassis-bolts/documents"}}