{"id":"F2006B07839","name":"Airworthiness Directives 2004 - Revocation and Remaking - DHC-6 (Twin Otter) Series Aeroplanes","slug":"airworthiness-directives-2004-revocation-and-remaking-dhc-6-twin-otter-series-aeroplanes","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50769,"registerId":"commonwealth-F2006B07839-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"Airworthiness Directives 2004 - Revocation and Remaking - DHC-6 (Twin Otter) Series Aeroplanes","content":"Airworthiness Directives 2004\n\nI, DAVID ALAN VILLIERS, delegate of the Civil Aviation Safety\n\nAuthority, acting under subregulation 39.001 (1) of the Civil\n\nAviation Safety Regulations 1998:\n\n(a) revoke the Airworthiness Directives mentioned in\n\nSchedule 1; and\n\n(b) make, as separate instruments, each Airworthiness\n\nDirective mentioned in Schedule 1 and attached.\n\n![](image.001.png)\n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority\n\n20 December 2004\n\nNote: Each attached Airworthiness Directive is being re-made in exactly the\n\nsame form as appears in the latest published edition of the Directive.\n\n  \nSchedule 1 Revocation and Remaking of\n\nAirworthiness Directives\n\nDHC-6 (Twin Otter) Series Aeroplanes\n\nAD Name AD Number\n\nUpper Rudder Fairing - Modification AD/DHC-6/1\n\nFuel System Crossfeed Thermal Relief - Modification AD/DHC-6/2\n\nAirstair Door Safety Guard - Modification AD/DHC-6/3\n\nNose Landing Gear - Modification AD/DHC-6/4\n\nFuselage Frame and Wing Strut - Modification AD/DHC-6/5\n\nTailplane Attachment Bolts - Modification AD/DHC-6/6\n\nElevator Rear Spar - Inspection and Modification AD/DHC-6/7 Amdt 1\n\nAirspeed Placard Installation and Left Elevator Trim Tab - Inspection AD/DHC-6/8 Amdt 1\n\nLeft and Right Hand Elevators Upper Skin - Modification AD/DHC-6/9\n\nLeft Hand Elevator Trim Tab - Replacement AD/DHC-6/10\n\nFlap Elevator Trim Cables - Modification AD/DHC-6/11\n\nAileron Mass Balance - Modification AD/DHC-6/12\n\nFlap Control Push Rod Assembly - Modification AD/DHC-6/13\n\nFuselage to Wing Front Spar Attachments - Inspection AD/DHC-6/14\n\nWing Strut Jo-Bolt - Inspection AD/DHC-6/15 Amdt 1\n\nWing Front Spar Attachment Fittings AD/DHC-6/16 Amdt 5\n\nControl Column - Lower Sub-Assembly - Inspection AD/DHC-6/17 Amdt 1\n\nRudder and Elevator Pulley Bracket Assembly Stn 106 - Inspection AD/DHC-6/18 Amdt 1\n\nPropeller and Power Control Lever Interlock - Mod AD/DHC-6/19\n\nCANCELLED AD/DHC-6/20\n\nElevator Connecting Rod - Inspection AD/DHC-6/21 Amdt 1\n\nPropeller Auto Feather System - Modification AD/DHC-6/22\n\nInverter Fuses - Replacement AD/DHC-6/23\n\nElevator and Tailplane AD/DHC-6/24 Amdt 3\n\nMain Undercarriage Platen Attach Link Fittings - Inspection AD/DHC-6/25 Amdt 1\n\nNose Landing Gear Fork Lock Pin - Inspection AD/DHC-6/26\n\nFuel Cell Sump Plate Flapper Valve Seals - Modification AD/DHC-6/27\n\nEngine Compressor Inlet Screens - Icing Restrictions AD/DHC-6/28\n\nAirframe De-Icing System - Modification AD/DHC-6/29\n\n  \nAir Conditioning Compartment - Modification AD/DHC-6/30\n\nStructural Component Inspection, Modification and Life Limitation AD/DHC-6/31 Amdt 3\n\nFuel Vent System - Modification AD/DHC-6/32\n\nElevator Root and Nose Ribs AD/DHC-6/33 Amdt 4\n\nPilot Seats Safety Restraint Installations - Modification AD/DHC-6/34\n\nWing Rear Spar Attachment Fittings AD/DHC-6/35 Amdt 2\n\nOverhead Console Control Quadrants AD/DHC-6/36 Amdt 2\n\nSide Seat Rail Attachment Rivets - Inspection and Modification AD/DHC-6/37\n\nHorizontal Stabiliser Rear Spar - Inspection AD/DHC-6/38\n\nElectric Power Cable Below Cockpit - Modification AD/DHC-6/39\n\nWing Struts - Inspection and Modification AD/DHC-6/40\n\nWing Tip Bonding - Modification AD/DHC-6/41\n\nInboard Trailing Flap - Inspection and Modification AD/DHC-6/42\n\nElevator Housing Assembly Lower Mounting Structure AD/DHC-6/43 Amdt 1\n\nLower Wing Skin to Spar Rivets - Inspection AD/DHC-6/44\n\nFuselage Side Frames Stns 218.125 and 219.525 AD/DHC-6/45 Amdt 1\n\nFlap Operating Rod Assemblies and Control Rods AD/DHC-6/46 Amdt 4\n\nPropeller Reversing Interconnect Linkage - CANCELLED AD/DHC-6/47\n\nIntroduction of Beta Range Test Switch AD/DHC-6/48\n\nFlight Control Rods AD/DHC-6/49 Amdt 3\n\nMain Landing Gear Legs - Inspection AD/DHC-6/50\n\nEngine Nacelle Lower Longerons AD/DHC-6/51 Amdt 4\n\nWindscreen Washer/De-Icing System - Discontinued Use of Isopropyl Alcohol AD/DHC-6/52\n\nTailplane Front and Rear Attachment Brackets - Inspection and Replacement - AD/DHC-6/53\n\nSide Folding Cabin Utility Seats - Inspection and Modification AD/DHC-6/54 Amdt 2\n\nFuel Boost Pumps - Inspection, Replacement, Modification AD/DHC-6/55\n\nLanding Gear - Nose Wheel Steering Cables - Inspection and Modification AD/DHC-6/56\n\nVoltage Regulators - Inspection and Provision of Ground Wires AD/DHC-6/57\n\nWing Struts Internal Beam Corrosion AD/DHC-6/58\n\nTailplane Attachment Brackets/Adjacent Spar Structure - CANCELLED AD/DHC-6/59\n\nWing Front Spar Attachment Adaptors AD/DHC-6/60 Amdt 4\n\nWing Main Spar Lower Cap Angles AD/DHC-6/61 Amdt 1\n\nElevator Quadrant Control Column and Elevator/Rudder Pulley Brackets AD/DHC-6/62 Amdt 5\n\nGust Lock Assembly AD/DHC-6/63\n\nElevator Pushrod Ball Ends AD/DHC-6/64\n\nWing Strut Chafing AD/DHC-6/65\n\n  \nStabiliser Attachment Fittings AD/DHC-6/66\n\nLower Skin and L/E Rivets at Front Spar AD/DHC-6/67\n\nHorizontal Stabiliser Centre Hinge Bracket - CANCELLED AD/DHC-6/68\n\nCorrosion Prevention and Control AD/DHC-6/69 Amdt 1\n\nHorizontal Stabiliser - Centre Hinge Bracket Flange AD/DHC-6/70\n\nFuselage Station FS 239 Frame AD/DHC-6/71\n\nCorrosion Prevention and Control - 2 AD/DHC-6/72\n\nWing Spar Strut Lug AD/DHC-6/73","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This instrument does not change the substantive scope of safety obligations. It revokes a consolidated 2004 Airworthiness Directives instrument and re‑issues each listed AD as a separate instrument in identical form. The change is administrative/legal‑form only (separate instruments instead of a single consolidated instrument), not a substantive expansion of obligations. Any practical change is limited to administration, publication and how operators track and reference the requirements."},"complexity_factors":["Single short instrument with straightforward operative language (revoke and remake).","Schedule lists 73 AD entries for DHC‑6 (including several marked CANCELLED), creating operational complexity for affected operators.","No defined terms or nested conditions within this instrument itself—substantive complexity is contained in the individually referenced ADs.","Cross‑reference to subregulation 39.001(1) as the legal authority.","Administrative note that re‑made ADs are identical to the latest published editions (potential for publication/recording mismatch if not managed)."],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- This is an administrative action by a delegate of the Civil Aviation Safety Authority (CASA) that: (a) revokes a previously published consolidated instrument called “Airworthiness Directives 2004”; and (b) re-issues (re-makes) each Airworthiness Directive (AD) listed in Schedule 1 as a separate, standalone legal instrument.  The instrument says each re-made AD is identical to the version that appears in the latest published edition of the Directive.\n\n**Who is affected**\n\n- Owners, operators, maintenance organisations and certificated engineers responsible for De Havilland Canada DHC‑6 (Twin Otter) series aeroplanes.  Those persons must comply with the requirements in the individual ADs (for example, mandated inspections, modifications, replacements or life limits).\n\n**Why it matters**\n\n- Airworthiness Directives are mandatory safety requirements. They tell operators what inspections, repairs or modifications must be done to keep an aircraft legally airworthy. By revoking the consolidated 2004 instrument and re-issuing the ADs as individual instruments, CASA preserves the existing safety obligations while changing the legal form in which they appear.\n\n**How it changes behaviour and who pays**\n\n- Who decides: a CASA delegate acting under subregulation 39.001(1) makes the change. (See the first paragraph of the instrument.)\n- Who pays: aircraft owners/operators bear the direct costs (labour, parts, maintenance downtime) required to comply with the ADs. Maintenance and engineering organisations bear administrative and compliance costs where they perform the work or keep records.\n- What behaviour changes: there is no change to the substance of the obligations because the ADs are re-made “in exactly the same form”; but compliance management may change in practice because each AD now exists as a separate legal instrument (operators may track and reference separate AD documents rather than a single consolidated document).\n\n**Operational and administrative effects to note**\n\n- The Schedule lists a long series of ADs that apply to DHC‑6 Twin Otter aeroplanes (AD/DHC‑6/1 through AD/DHC‑6/73, with some entries marked CANCELLED). The substantive requirements in those ADs include inspections, modifications, replacements, installation of placards or parts, life‑limits, and corrosion control.\n- By keeping the content identical to the latest published ADs, CASA claims no substantive change; the practical effects are primarily administrative: clearer citation of individual ADs, easier individual amendment or repeal of an AD in future, and potential changes in record‑keeping for operators and regulators.\n\n**Costs, incentives and trade‑offs**\n\n- Concentrated costs fall on the owners/operators who must perform and document mandated work; benefits (airworthiness and safety) are concentrated on operators’ passengers and broader aviation users. The ADs impose legally binding technical obligations, so non‑compliance can have regulatory or safety consequences.\n- Administrative costs for CASA and for operators may increase marginally because there are more separate instruments to issue, publish and manage. The benefit is greater modularity (each AD can be varied or revoked without changing a consolidated instrument).\n- Implementation risk is low on the substantive side (the ADs themselves are unchanged), but there is modest administrative risk: errors in re-issuing, publication, or operators’ tracking could cause temporary confusion about which document to follow.\n\n**Legal basis and scope**\n\n- The delegate acts under subregulation 39.001(1) of the Civil Aviation Safety Regulations 1998 to revoke the consolidated instrument and make the individual ADs.\n\n(References: the instrument text and Schedule 1 listing the ADs for DHC‑6 Twin Otter series aeroplanes.)"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"The scope remains exactly as intended. This is a pure administrative remaking exercise under new regulations — the instrument explicitly states that each directive is being re-made 'in exactly the same form as appears in the latest published edition.' No expansion of scope has occurred."},"complexity_factors":["Single, clear purpose: revocation and remaking of existing instruments","No conditional logic or nested exceptions in the instrument itself","Simple two-part structure: (a) revoke, (b) remake","Schedule 1 is a straightforward table listing 73 directives by name and number","No defined terms requiring interpretation within this instrument","Cross-references only to the empowering regulation (subregulation 39.001(1)) and the attached directives","Note clarifies that content remains unchanged — no substantive amendments to parse","However, complexity exists in the *attached* directives (not fully reproduced here), which contain detailed technical specifications for aircraft maintenance"],"plain_english_summary":"This CASA order revokes and reissues 73 Airworthiness Directives for DHC‑6 Twin Otter aircraft, re‑making them as fresh, legally valid instruments without changing the safety requirements. It affects Australian owners, operators, maintenance organisations and pilots of these aircraft.\n\nThis is administrative housekeeping: the directives are reissued to align with post‑1998 legal powers so the existing mandatory safety instructions remain enforceable."},"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/airworthiness-directives-2004-revocation-and-remaking-dhc-6-twin-otter-series-aeroplanes","history":"/api/acts/airworthiness-directives-2004-revocation-and-remaking-dhc-6-twin-otter-series-aeroplanes/history","analysis":"/api/acts/airworthiness-directives-2004-revocation-and-remaking-dhc-6-twin-otter-series-aeroplanes/analysis","conflicts":"/api/acts/airworthiness-directives-2004-revocation-and-remaking-dhc-6-twin-otter-series-aeroplanes/conflicts","importantCases":"/api/acts/airworthiness-directives-2004-revocation-and-remaking-dhc-6-twin-otter-series-aeroplanes/important-cases","documents":"/api/acts/airworthiness-directives-2004-revocation-and-remaking-dhc-6-twin-otter-series-aeroplanes/documents"}}