{"id":"F2006B10680","name":"AD/HU 369/17 - Tail Rotor Drive System - Inspection","slug":"ad-hu-369-17-tail-rotor-drive-system-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116624,"registerId":"commonwealth-F2006B10680-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 369/17 - Tail Rotor Drive System - Inspection","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  McDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters\n\n \n\nAD/HU 369/17 Tail Rotor Drive System - Inspection 6/75\n\nApplicability: All models equipped with metal tail rotor blades and all models with drive shafts not previously indexed.\n\n \n\nDocument: Hughes SIN No. HN-86.\n\n \n\nCompliance: For Part 1 - Within 100 hours time in service after 30 June 1975.\n\n \n\nFor Part 2 - At intervals not exceeding 100 hours time in service after 30 June 1975.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The supplied text sets a confined applicability and clear compliance intervals and does not indicate any change from an earlier or different scope. There is no information in the supplied instrument suggesting the directive’s scope has been expanded or narrowed relative to an original intent."},"complexity_factors":["Narrow, specific applicability criteria (metal tail rotor blades; drive shafts not previously indexed)","Two-part timing scheme with an initial deadline tied to a fixed date and recurring 100‑hour intervals (potentially confusing scheduling)","Dependence on an external document (Hughes SIN No. HN-86) for technical inspection steps","Use of a technical term (“indexed”) without definition in the supplied text, creating scope/interpretation issues","Regulatory origin and enforcement by CASA implied by the header, requiring operator record-keeping and regulator oversight"],"plain_english_summary":"What this instrument does (mechanical change)\n\n- This Airworthiness Directive (AD/HU 369/17) requires inspections of the tail rotor drive system for specified McDonnell Douglas (Hughes) and Kawasaki 369 series helicopters. (header; Applicability)\n- It directs operators to follow the inspection procedure set out in Hughes Service Information Notice No. HN-86. (Document)\n- Two timing rules apply: an initial inspection (Part 1) to be completed within 100 hours time-in-service after 30 June 1975, and recurring inspections (Part 2) at intervals not exceeding 100 hours time-in-service after 30 June 1975. (Compliance)\n\nWho is affected\n\n- Operators of all 369-series helicopters that have metal tail rotor blades. (Applicability)\n- Operators of any 369-series helicopter whose tail rotor drive shafts have not previously been indexed. The directive excludes drive shafts that have already been indexed. (Applicability)\n\nWho pays, who decides, and what changes in behaviour\n\n- Who decides: The Civil Aviation Safety Authority issued this directive as part of the Schedule of Airworthiness Directives under the Civil Aviation Regulations 1998. (header)\n- Who pays: Aircraft operators absorb the direct costs — labour, downtime and any parts or repairs found necessary when carrying out the required inspections and any follow‑on maintenance. (Compliance; Applicability)\n- What changes: Operators must schedule and carry out an initial inspection within the specified 100‑hour window and then repeat inspections every 100 hours. Operators with drive shafts that are not indexed may face a continuing inspection obligation until indexing (if performed) changes their applicability. (Compliance; Applicability)\n- Operators must obtain and follow Hughes SIN No. HN-86 for the technical steps of the inspection, so complying requires access to, and reliance on, that manufacturer document. (Document)\n\nExplicit purpose and the text’s silence on rationale\n\n- The text mandates inspections and references a manufacturer instruction. The supplied text does not include an explicit statement of the directive’s underlying rationale or the safety findings that led to it. (Document; Compliance)\n\nCosts, incentives and trade-offs (mechanisms, not judgements)\n\n- Direct compliance cost: recurring inspection labour and aircraft downtime every 100 hours for affected helicopters. (Compliance)\n- Follow‑on cost risk: inspections may reveal defects that require repair or parts replacement; those are additional operator costs. (Compliance)\n- Incentives: because the applicability excludes drive shafts that are already indexed, operators have an incentive to have drive shafts indexed (or to show they were previously indexed) to avoid the recurring inspection requirement; the text does not specify the process or criteria for proving prior indexing. (Applicability)\n- Dependence on external technical detail: the AD delegates the specific inspection steps to Hughes SIN HN-86, so compliance requires consulting that external document. The AD text itself does not spell out the technical procedure. (Document)\n\nCompliance burden and implementation risk\n\n- Administrative burden: operators must track time-in-service to meet the 100‑hour initial and recurring windows and keep records of inspections and any corrective actions. (Compliance)\n- Ambiguities that can affect implementation: the AD uses the term “indexed” without defining it in the supplied text and relies on an external service instruction for procedure — both create points where operators or regulators may need to interpret whether a particular helicopter meets the applicability or compliance conditions. (Applicability; Document)\n\nNet operational effect (mechanical summary)\n\n- Mechanical effect: an identifiable subset of 369-series helicopters must undergo a specified inspection process at fixed intervals, following a manufacturer service notice. The operator bears the time, labour and parts costs; the regulator prescribes the schedule and references the maker’s procedure. (Applicability; Document; Compliance)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive from 1975 addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original purpose of ensuring tail rotor drive system integrity through periodic inspection."},"complexity_factors":["Single, specific mechanical system targeted (tail rotor drive)","Only two compliance requirements: initial inspection and recurring interval","Simple applicability test: two criteria (metal blades + non-indexed shafts)","No defined terms section, no cross-references to other legislation","Short document (approximately 150 words of substantive content)","Single external reference (Hughes SIN HN-86) with no incorporation by reference complexity","No conditional logic, exceptions, or nested provisions"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it like a compulsory recall notice, but for aircraft rather than cars.\n\n**What it does:** It requires owners and operators of specific McDonnell Douglas (Hughes) and Kawasaki 369 series helicopters to inspect their **tail rotor drive system** — the mechanical components that spin the tail rotor (the small propeller at the back that stops the helicopter from spinning uncontrollably).\n\n**Who it affects:** \n- All Hughes/Kawasaki 369 helicopter models fitted with **metal tail rotor blades**\n- Any models where the drive shafts haven't been \"indexed\" before (meaning the shafts haven't been marked or aligned in a specific rotational position to ensure even wear)\n\n**What must be done:**\n- **Part 1:** A one-time inspection within 100 hours of flying time after 30 June 1975\n- **Part 2:** Ongoing inspections every 100 hours of flying time after that date\n\n**Why it matters:** The tail rotor is critical for helicopter control. A failure here can cause catastrophic loss of control. This AD likely responds to a known defect or incident pattern identified in Hughes Service Information Notice HN-86.\n\n**Key point:** This is not optional. Non-compliance grounds the aircraft — it cannot legally fly until the work is done."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-17-tail-rotor-drive-system-inspection","history":"/api/acts/ad-hu-369-17-tail-rotor-drive-system-inspection/history","analysis":"/api/acts/ad-hu-369-17-tail-rotor-drive-system-inspection/analysis","conflicts":"/api/acts/ad-hu-369-17-tail-rotor-drive-system-inspection/conflicts","importantCases":"/api/acts/ad-hu-369-17-tail-rotor-drive-system-inspection/important-cases","documents":"/api/acts/ad-hu-369-17-tail-rotor-drive-system-inspection/documents"}}