{"id":"F2006B09134","name":"AD/DHC-6/45 Amdt 1 - Fuselage Side Frames Stns 218.125 and 219.525","slug":"ad-dhc-6-45-amdt-1-fuselage-side-frames-stns-218-125-and-219-525","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115687,"registerId":"commonwealth-F2006B09134-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/45 Amdt 1 - Fuselage Side Frames Stns 218.125 and 219.525","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-6/45\n\nAmdt 1\n\n  \nFuselage Side Frames Stns 218.125 and 219.525 4/92\n\nApplicability: Model DHC-6 Series with serial numbers 1 through 411 inclusive. Requirement: 1. Action in accordance with de Havilland SB 6/371.\n\n2. Incorporate de Havilland modifications 6/1461 (or 6/1553) and 6/1462.\n\nNote: Transport Canada AD CF-78-17 R1 refers.\n\nCompliance: 1. At intervals as specified in the requirement document, until modified in accordance with Requirement 2.\n\n2. Prior to 1 January 1996.\n\nThe compliance of the previous issue of this Directive was as per Requirement Document.\n\nThis amendment is effective from 2 April 1992.\n\nBackground: Inter-rivet cracking of the fuselage side frame skin flanges at Stations 218.125 and\n\n219.525 has occurred on a number of aircraft in service. Cracks are initiated by stress induced by riveting; side frames of material with improved stress corrosion resistance have been introduced by the manufacturer.\n\nAmendment 1 is issued to align this Directive with a revision of the relevant Country of Origin AD which requires terminating action in lieu of on going repetitive inspections.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment narrows and clarifies the original scope rather than expanding it. The original directive required ongoing repetitive inspections indefinitely; Amendment 1 introduces a terminating action (permanent modification) that ends the inspection requirement. This is a refinement of the original safety purpose, not an expansion beyond it."},"complexity_factors":["Short, single-purpose document (1 page)","Only 2 defined requirements with clear alternatives","Minimal cross-referencing (only references to manufacturer service bulletin and Transport Canada AD)","Simple conditional logic: inspect until modified, or modify by fixed date","Technical aviation terminology requires some domain knowledge but is standard for the industry"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of de Havilland DHC‑6 Twin Otter aircraft (s/n 1–411) to address fatigue cracking found in fuselage side frames at Stations 218.125 and 219.525. Until the permanent repair—installation of improved, corrosion‑resistant side frames by 1 January 1996—is carried out, affected aircraft must undergo recurring inspections per the manufacturer’s service bulletin. Amendment 1 limits repeated inspection as a stopgap, making inspection mandatory only until the permanent modification is installed, aligning with Canadian action."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Yes. The amendment shifts the compliance regime from ongoing repetitive inspections (as originally directed by the requirement document) to a mandatory terminating action: incorporation of specified de Havilland modifications by a set date (Amendment 1; Background; Requirement 2). The applicability (s/n 1–411) and the technical focus (cracking at stations 218.125 and 219.525) remain the same, but the directive now mandates modification rather than indefinite inspection."},"complexity_factors":["Dependent on an external service document for inspection intervals (de Havilland SB 6/371) — operators must follow that document's schedule (Requirement 1, Compliance).","Requires physical structural modifications as terminating action (mods 6/1461 or 6/1553, and 6/1462) with a fixed deadline (Requirement 2; Compliance 2: prior to 1 January 1996).","Offers two alternative modification identifiers for one of the mods (6/1461 or 6/1553), introducing an option that operators must interpret or confirm.","Limited applicability by serial number range (Models DHC‑6 with s/n 1–411), requiring record checks to determine applicability.","Changes compliance regime from ongoing repetitive inspections to a one‑time terminating modification (Background; Amendment 1), affecting maintenance planning.","Cross‑reference to Country of Origin AD and Transport Canada AD CF‑78‑17 R1 — alignment and international coordination are required."],"plain_english_summary":"This Airworthiness Directive applies to DHC‑6 (Twin Otter) aeroplanes, serial numbers 1–411. It requires operators to carry out inspections per de Havilland Service Bulletin 6/371 until they install specified structural modifications (de Havilland mods 6/1461 or 6/1553, and 6/1462); the modifications must be completed by 1 January 1996 (AD effective 2 April 1992).\n\nThe directive responds to inter‑rivet cracking at fuselage side‑frame stations 218.125 and 219.525; Amendment 1 replaces repeating inspections with a terminating modification to address material and stress issues."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-45-amdt-1-fuselage-side-frames-stns-218-125-and-219-525","history":"/api/acts/ad-dhc-6-45-amdt-1-fuselage-side-frames-stns-218-125-and-219-525/history","analysis":"/api/acts/ad-dhc-6-45-amdt-1-fuselage-side-frames-stns-218-125-and-219-525/analysis","conflicts":"/api/acts/ad-dhc-6-45-amdt-1-fuselage-side-frames-stns-218-125-and-219-525/conflicts","importantCases":"/api/acts/ad-dhc-6-45-amdt-1-fuselage-side-frames-stns-218-125-and-219-525/important-cases","documents":"/api/acts/ad-dhc-6-45-amdt-1-fuselage-side-frames-stns-218-125-and-219-525/documents"}}