{"id":"F2006B09155","name":"AD/DHC-6/67 - Lower Skin and L/E Rivets at Front Spar","slug":"ad-dhc-6-67-lower-skin-and-l-e-rivets-at-front-spar","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52849,"registerId":"commonwealth-F2006B09155-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/67 - Lower Skin and L/E Rivets at Front Spar","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-6/67 Lower Skin and L/E Rivets at Front Spar 1/94\n\nApplicability: Model DHC-6 aircraft that do not have Modifications 6/1645 and 6/1893 incorporated.\n\nRequirement: 1. Carry out a detailed visual inspection in accordance with Part A of de Havilland Service Bulletin 6/517.\n\nIf any unserviceable rivets are found, proceed in accordance with Part C of Service Bulletin 6/517.\n\nIn addition, if four or more rivets in the joint are missing or defective, proceed in accordance with Part B of Service Bulletin 6/517.\n\n    2. Carry out the following modifications in accordance with Part C of Service Bulletin 6/517:\n\n    On aircraft up to and including serial number 580, incorporate Modification 6/1645.\n\n    b. On all aircraft, incorporate Modification 6/1893.\n\nNote: Transport Canada AD CF-93-25 refers.\n\nCompliance: 1. Within 500 hours time in service after 6 January 1994, or prior to 6 April 1994, whichever occurs first.\n\n2. Prior to 6 July 1994.\n\nBackground: Corrosion has been found on the heads of the rivets attaching the wing lower and leading edge skins to the front spar flanges in the area between the landing light and the engine nacelle. Loss of these rivets will destroy the structural integrity of the joint.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused specifically on rivet corrosion in DHC-6 aircraft wings. It has not expanded beyond its original safety purpose; the scope remains tightly constrained to the specific structural defect identified in the background."},"complexity_factors":["Short, single-purpose directive with clear sequential requirements","Only 2 defined applicability conditions (aircraft model and modification status)","Simple conditional logic: 'if unserviceable rivets found → do X; if 4+ rivets bad → also do Y'","Cross-references to external technical documents (Service Bulletin 6/517 Parts A, B, C) rather than reproducing them inline","Two-tier compliance deadline structure (inspection vs. modification phases)","No nested exceptions or complex definitional sections"],"plain_english_summary":"This AD requires owners/operators of de Havilland DHC‑6 Twin Otters (unless already fitted with two specified factory mods) to inspect and repair corroded rivets that secure the wing lower skin/leading edge to the front spar, and to install mandated modifications. Corroded or missing rivets can compromise wing structural integrity and risk in‑flight failure, so the inspections, repairs and mods are compulsory within the specified compliance windows."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive explicitly targets aircraft lacking Mod 6/1645 and Mod 6/1893 and prescribes inspection, repair and modification actions; the text gives no indication that the scope has been expanded or narrowed from its stated applicability."},"complexity_factors":["Applicability is conditional: only DHC-6 aircraft without Mod 6/1645 and 6/1893 are affected (Applicability).","Inspect-and-repair regime references an external manufacturer Service Bulletin with multiple parts (inspection, repair, modification) so compliance requires obtaining and following that SB (Requirement: Part A/B/C).","Conditional escalation: finding four or more missing/defective rivets triggers additional mandatory work (Requirement: Part B).","Serial-number carve‑out for one modification (Mod 6/1645 applies only to aircraft up to serial number 580) introduces fleet-differentiated obligations (Requirement 2a).","Multiple short, tiered compliance deadlines (inspection within 500 flight hours or by a calendar date; modifications by later dates) create scheduling and operational constraints (Compliance).","Technical nature of inspections and repairs requires specialist maintenance skills, tools and possible structural replacement—raising direct repair costs and potential downtime (Background; Requirement).","Regulatory cross-reference to Transport Canada increases the need to reconcile guidance across authorities (Note)."],"plain_english_summary":"Requires operators of DHC-6 (Twin Otter) aeroplanes that do not already have Mod 6/1645 and Mod 6/1893 to inspect the lower skin and leading-edge rivets at the front spar, repair defective or missing rivets, and install the specified modifications within short, fixed time windows. It matters because corrosion was found on rivet heads in that joint; losing the rivets would destroy the joint’s structural integrity, so operators pay for inspections, repairs and mandated modifications to restore airworthiness."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-67-lower-skin-and-l-e-rivets-at-front-spar","history":"/api/acts/ad-dhc-6-67-lower-skin-and-l-e-rivets-at-front-spar/history","analysis":"/api/acts/ad-dhc-6-67-lower-skin-and-l-e-rivets-at-front-spar/analysis","conflicts":"/api/acts/ad-dhc-6-67-lower-skin-and-l-e-rivets-at-front-spar/conflicts","importantCases":"/api/acts/ad-dhc-6-67-lower-skin-and-l-e-rivets-at-front-spar/important-cases","documents":"/api/acts/ad-dhc-6-67-lower-skin-and-l-e-rivets-at-front-spar/documents"}}