{"id":"F2006B09111","name":"AD/DHC-6/24 Amdt 3 - Elevator and Tailplane","slug":"ad-dhc-6-24-amdt-3-elevator-and-tailplane","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115664,"registerId":"commonwealth-F2006B09111-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/24 Amdt 3 - Elevator and Tailplane","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-6/24\n\nAmdt 3\n\n  \nElevator and Tailplane 9/94\n\nApplicability: All model DHC-6 aircraft.\n\nRequirement: 1. Accomplish the inspections defined in the Accomplishment Instructions in de Havilland Service Bulletin 6/421 Revision B.\n\n2. Install Modification 6/1799 in accordance with de Havilland Service Bulletin 6/421 Revision B.\n\nNote 1: Incorporation of Modification 6/1799 provides terminating action for the inspection requirements of this Directive.\n\nNote 2: Transport Canada AD CF-83-11R1 refers.\n\nCompliance: 1. Within 50 hours time in service after 31 August 1983, and thereafter at intervals not to exceed 1200 hours time in service.\n\n2. Unless already accomplished, prior to 31 March 1995.\n\nThe compliance of the previous issue of this Directive remains unchanged as Requirement 1, while Requirement 2 is introduced in this issue.\n\nThis amendment is effective from 18 August 1994.\n\nBackground: There have been reported instances of cracking, galling, and enlargement of bolt holes in the elevator outboard hinge assemblies, a lug failure on the tailplane fitting, and elongated holes in the elevator attachment fitting at the attachment to the hinge arm assembly.\n\nAmendment 2 relaxed the repeat inspection interval.\n\nAmendment 3 is issued to align this Directive with a revision of the related Transport Canada AD which requires modification action pursuant to Transport Canada’s Ageing Aircraft Program.","sortOrder":0}],"analysis":{"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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"Originally this Directive only required repeated inspections (Requirement 1). Amendment 3 expanded the scope to mandate a permanent structural modification (Requirement 2), transforming it from an ongoing inspection regime to a 'inspect-until-modified' approach. This aligns with Transport Canada's Ageing Aircraft Program, indicating the scope evolved from routine maintenance to active airframe life-extension."},"complexity_factors":["Short, single-purpose document (2 requirements only)","Minimal defined terms (relies on external technical references like 'Service Bulletin 6/421 Revision B')","Simple conditional logic: Requirement 2 only applies 'unless already accomplished'","One cross-reference to foreign regulation (Transport Canada AD CF-83-11R1)","Clear compliance dates and flight hour intervals","No nested exceptions or interpretive provisions"],"plain_english_summary":"This Airworthiness Directive mandates safety action for all de Havilland DHC‑6 Twin Otter aircraft in Australia after reports of cracking/wear at the elevator–tailplane connection. Operators must inspect the elevator and tailplane at short intervals and, by 31 March 1995, install a specified modification that permanently cures the defect and ends the need for repeated inspections. The amendment aligns Australian requirements with Canadian standards to prevent loss of pitch control from component failure."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Yes. This amendment introduced a new mandatory modification requirement (Modification 6/1799) in addition to existing recurring inspections. The modification is required to be completed by 31 March 1995 and, when installed, terminates the inspection requirement (Requirement 2; Note 1; Compliance 2). The change aligns the Directive with a revision of the related Transport Canada AD (Background)."},"complexity_factors":["Dependence on an external technical document (de Havilland Service Bulletin 6/421 Revision B) for inspection and modification instructions (Requirement 1 & 2).","Dual compliance regime: short initial deadline (50 hours after 31 Aug 1983) and a long repeat interval (1,200 hours) for inspections (Compliance 1).","A mandatory modification with a fixed calendar deadline (by 31 Mar 1995) that provides terminating action for inspections (Requirement 2; Note 1; Compliance 2).","Regulatory alignment with a foreign authority (Transport Canada AD CF-83-11R1) which can introduce cross-jurisdictional reference dependence (Note 2; Background).","Amendment history changes the directive’s scope by adding Requirement 2 while leaving Requirement 1 unchanged, creating layered obligations (text: \"The compliance of the previous issue ... remains unchanged as Requirement 1, while Requirement 2 is introduced\")."],"plain_english_summary":"This Airworthiness Directive requires all DHC‑6 (Twin Otter) operators to perform inspections per de Havilland Service Bulletin 6/421 Revision B and to install Modification 6/1799 under the same bulletin. Inspections begin within 50 hours after 31 Aug 1983 and repeat every 1,200 hours; the modification must be done by 31 Mar 1995 unless already completed. (Reqs 1–2; Compliance 1–2; Note 1).\n\nAircraft owners/operators pay and schedule the work. The Directive targets cracking, galling, lug and hole failures in elevator and tailplane fittings; installing the modification terminates the repeated inspections. (Background; Note 1)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-24-amdt-3-elevator-and-tailplane","history":"/api/acts/ad-dhc-6-24-amdt-3-elevator-and-tailplane/history","analysis":"/api/acts/ad-dhc-6-24-amdt-3-elevator-and-tailplane/analysis","conflicts":"/api/acts/ad-dhc-6-24-amdt-3-elevator-and-tailplane/conflicts","importantCases":"/api/acts/ad-dhc-6-24-amdt-3-elevator-and-tailplane/important-cases","documents":"/api/acts/ad-dhc-6-24-amdt-3-elevator-and-tailplane/documents"}}