{"id":"F2006B09139","name":"AD/DHC-6/50 - Main Landing Gear Legs - Inspection","slug":"ad-dhc-6-50-main-landing-gear-legs-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115697,"registerId":"commonwealth-F2006B09139-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/50 - Main Landing Gear Legs - 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)  \nDHC-6 (Twin Otter) Series Aeroplanes\n\nAD/DHC-6/50 Main Landing Gear Legs \\- Inspection 5/80\n\nApplicability: All model DHC-6 which do not have De Havilland Aircraft of Canada Ltd.\n\nModification 6/1660 incorporated.\n\nRequirement: 1. Inspect as necessary the main landing gear legs in accordance with either Schedule No. 1 or Schedule No. 2 of the De Havilland Aircraft of Canada Ltd. SB No.\n\n6/380. In lieu of the visual external inspections required by paragraph (a) of Schedule No. 1 or Schedule No. 2, refer to the Accomplishment Instructions and Figure 1 of the referenced Service Bulletin, remove the external finish from the Inspection Area and inspect using a dye penetrant method. If no cracks are observed, reprotect the stripped area, and proceed in accordance with paragraph (b) of the appropriate Schedule. If cracks are found, proceed in accordance with Schedule No. 1 paragraph (e), (f) and (g) as appropriate.\n\n2. Perform a Check D inspection in accordance with the Accomplishment Instructions of the De Havilland Aircraft of Canada Ltd. SB No. 6/380.\n\nNote: Transport Canada Airworthiness Directive CF-80-06 De Havilland refers.\n\nCompliance: Para. 1 \\- Within 50 hours time in service after 15 May 1980, unless already accomplished.\n\nPara. 2 \\- Within 2400 hours flight time or before 21 December 1980 whichever comes first, unless already accomplished within the last 9600 hours flight time or 4 years, and thereafter at intervals not to exceed 12000 hours flight time or 5 years whichever comes first.\n\nBackground: Advice from overseas indicated failures of the Main Landing Gear Legs originated from corrosion pockets in the Y-joint weld.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1886},"content_quality":"ok","complexity_score":5,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow safety scope—addressing specific corrosion-related failures in DHC-6 main landing gear Y-joint welds identified through overseas incident reporting. It has not expanded beyond this specific airworthiness issue."},"complexity_factors":["External referencing of unpublished technical documents (Service Bulletin 6/380, Modification 6/1660) requiring specialized aviation knowledge to interpret","Multiple conditional inspection pathways (Schedule 1 vs Schedule 2, dye penetrant alternative to visual inspection)","Nested time-based compliance deadlines with multiple thresholds and exceptions (50 hours time in service, calendar dates, flight hour intervals, and 'unless already accomplished' clauses)","Technical aviation terminology (time in service, Check D inspection, dye penetrant testing, reprotecting stripped areas)","Bifurcated compliance structure with different consequences based on inspection findings (crack detected vs no crack detected)"],"plain_english_summary":"This directive orders owners/operators of De Havilland DHC-6 (Twin Otter) aircraft without factory Modification 6/1660 to carry out urgent inspections of the main landing gear Y-joint welds to detect hidden corrosion that can cause gear collapse.  \n\nIt mandates immediate crack detection using dye‑penetrant methods and a comprehensive Check D overhaul on a specified schedule to prevent in‑service failure, protecting passengers, crew, and aircraft integrity."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-50-main-landing-gear-legs-inspection","history":"/api/acts/ad-dhc-6-50-main-landing-gear-legs-inspection/history","analysis":"/api/acts/ad-dhc-6-50-main-landing-gear-legs-inspection/analysis","conflicts":"/api/acts/ad-dhc-6-50-main-landing-gear-legs-inspection/conflicts","importantCases":"/api/acts/ad-dhc-6-50-main-landing-gear-legs-inspection/important-cases","documents":"/api/acts/ad-dhc-6-50-main-landing-gear-legs-inspection/documents"}}