{"id":"F2019L00105","name":"AD/DHC-6/77 Horizontal Stabiliser - Centre Hinge Bracket Flange","slug":"ad-dhc-6-77-horizontal-stabiliser-centre-hinge-bracket-flange","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":98729,"registerId":"commonwealth-F2019L00105-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Viking Air DHC-6 (Twin Otter) Series Aer","sectionType":"part","heading":"Viking Air DHC-6 (Twin Otter) Series Aeroplanes","content":"# Viking Air DHC-6 (Twin Otter) Series Aeroplanes\n\n| AD/DHC-6/77 | Horizontal Stabiliser - CentreHinge Bracket Flange | 4/2019 |\n| ----------- | -------------------------------------------------- | ------ |\n\n| Applicability: | All Viking Air (De Havilland Canada) DHC-6 Model aircraft.                                                                                                                                                                                                                                                                                                                                                                                                                |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Carry out a fluorescent dye penetrant inspection of all flanges of Horizontal Stabiliser Hinge Bracket Part Number (P/N) C6TPM1021 in accordance with the technical instructions of Viking Air (de Havilland Canada) Service Bulletin 6/512 Revision 1 dated 24 April 1992 and as in force at the commencement of this AD.Note: Transport Canada AD CF-92-05 refers.                                                                                                   |\n| Compliance:    | 1. a. Unless previously accomplished in accordance with AD/DHC-6/70, within 250 hours’ time in service after the commencement date of this AD.b. Re-inspect at intervals not to exceed every 1200 hours’ time in service after the inspection referred to in the preceding paragraph a.The repeat inspections are required regardless of hinge bracket replacement.Compliance with the requirement of AD/DHC-6/70 constitutes compliance with the requirement of this AD. |\n|                | This AD commences on 15 February 2019.                                                                                                                                                                                                                                                                                                                                                                                                                                    |\n| Background:    | In-service cracking has been reported in the horizontal stabiliser centre hinge bracket flange.This AD is issued to re-instate the requirement of AD/DHC-6/70 which was inadvertently cancelled due to an administrative error.                                                                                                                                                                                                                                           |\n\n![](image.001.png)\n\nBenjamin Wilson  \nDelegate of the Civil Aviation Safety Authority\n\n7 February 2019","sortOrder":0},{"sectionNumber":"AD/DHC-6/77","sectionType":"part","heading":"AD/DHC-6/77","content":"## AD/DHC-6/77","sortOrder":1},{"sectionNumber":"Horizontal Stabiliser - CentreHinge Brac","sectionType":"part","heading":"Horizontal Stabiliser - CentreHinge Bracket Flange","content":"## Horizontal Stabiliser \\- Centre  \nHinge Bracket Flange","sortOrder":2},{"sectionNumber":"4/2019","sectionType":"part","heading":"4/2019","content":"## 4/2019","sortOrder":3}],"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"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This instrument restores the inspection requirement from AD/DHC‑6/70 that had been inadvertently cancelled; it does not expand applicability or alter the specified inspection method, part number, or the stated compliance intervals."},"complexity_factors":["Technical inspection method specified (fluorescent dye‑penetrant) requiring specialised labour and equipment.","Mandated compliance times: initial inspection within 250 hours TIS and repeats every 1200 hours TIS.","Reference to an external service bulletin (Viking Air Service Bulletin 6/512 Rev 1 dated 24 April 1992) for technical instructions.","Parts specificity: applies to Horizontal Stabiliser Hinge Bracket P/N C6TPM1021.","Cross‑reference to and reinstatement of a prior AD (AD/DHC‑6/70) creates dependency on historical compliance records.","Requirement that repeat inspections occur regardless of hinge bracket replacement increases ongoing compliance burden.","Applicability to the entire fleet of DHC‑6 aircraft concentrates costs on all operators of that model."],"plain_english_summary":"This AD reinstates an inspection rule for all Viking Air (De Havilland Canada) DHC‑6 (Twin Otter) aeroplanes: operators must perform a fluorescent dye‑penetrant inspection of the horizontal stabiliser centre hinge bracket flange (P/N C6TPM1021) following Viking Air Service Bulletin 6/512 Rev 1. The first inspection must be done within 250 hours’ time in service and repeated every 1200 hours; operators pay for and schedule the inspections and accept associated aircraft downtime. It was issued after reports of in‑service cracking and restores a requirement that had been inadvertently cancelled."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD explicitly states it is reinstating the requirement of a previous directive (AD/DHC-6/70) that was accidentally cancelled. The scope remains identical to the original safety intent — inspecting the horizontal stabiliser hinge bracket for cracks. No expansion of scope has occurred."},"complexity_factors":["Single, clearly defined mechanical component (one part number: C6TPM1021)","Straightforward two-tier compliance schedule (initial + recurring)","Only one technical reference document (Service Bulletin 6/512 Rev 1)","Minimal conditional logic (only exception is prior compliance with superseded AD/DHC-6/70)","No defined terms section — uses standard aviation terminology","Short document (approximately 200 words of substantive content)"],"plain_english_summary":"This AD requires owners/operators of Viking Air (formerly De Havilland Canada) DHC‑6 Twin Otter aircraft to perform fluorescent‑dye inspections of the centre hinge bracket flange on the horizontal stabiliser to detect cracks. Cracked brackets can cause loss of pitch control, so the directive reinstates a previously cancelled safety check. Initial inspection is within 250 flight hours and repeats every 1,200 hours; inspections must continue even if the bracket is replaced and must follow Viking Service Bulletin 6/512 Rev.1."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-77-horizontal-stabiliser-centre-hinge-bracket-flange","history":"/api/acts/ad-dhc-6-77-horizontal-stabiliser-centre-hinge-bracket-flange/history","analysis":"/api/acts/ad-dhc-6-77-horizontal-stabiliser-centre-hinge-bracket-flange/analysis","conflicts":"/api/acts/ad-dhc-6-77-horizontal-stabiliser-centre-hinge-bracket-flange/conflicts","importantCases":"/api/acts/ad-dhc-6-77-horizontal-stabiliser-centre-hinge-bracket-flange/important-cases","documents":"/api/acts/ad-dhc-6-77-horizontal-stabiliser-centre-hinge-bracket-flange/documents"}}