{"id":"F2006B10355","name":"AD/HILLER 12/28 - Main Rotor Blade Anti-Node Bar - Inspection","slug":"ad-hiller-12-28-main-rotor-blade-anti-node-bar-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115965,"registerId":"commonwealth-F2006B10355-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HILLER 12/28 - Main Rotor Blade Anti-Node Bar - 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)  Hiller UH-12 Series Helicopters\n\n \n\nAD/HILLER 12/28 Main Rotor Blade Anti-Node Bar - Inspection 5/80\n\nApplicability:  All models UH-12D, UH-12E, UH-12E4, H-23F, OH-23G and all models converted by STC178WE or STC177WE, equipped with main rotor blades Parsons P/N 2253- 1101-04.\n\n \n\nDocument: Hiller Aviation SB No. UH-12-51-5. Compliance:  As per requirement document.\n\nBackground:  The manufacturer states that anti-node bars with machine cut threads may be installed on certain main rotor blades of the subject P/N 2253-1101-04.\n\n \n\nNote: The requirement for inspection of these blades has been removed from AD/HILLER 12/23 to this Directive.\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":4,"scope_assessment":{"changed":true,"description":"The directive explicitly moves the inspection requirement for the specified blades out of AD/HILLER 12/23 and into this new directive (\"Note\"). That changes where the obligation is recorded and enforced: the substantive inspection requirement remains but its statutory placement has shifted from the earlier AD to this one. Operators must therefore consult this directive (and its referenced service bulletin) rather than AD/HILLER 12/23 to determine current inspection obligations."},"complexity_factors":["Directive delegates all technical detail (inspection steps, intervals, corrective action) to an external service bulletin rather than stating them in the AD (Document; Compliance).","Applicability covers multiple airframe models and two STC conversions, requiring operators to check model/airframe and modification status before determining applicability (Applicability).","The AD does not specify timeframes or intervals directly, creating potential ambiguity about when inspections must occur absent consulting the service bulletin (Compliance).","Identifying \"anti-node bars with machine cut threads\" may require specialist inspection techniques or disassembly, increasing practical inspection complexity (Background).","Cross-reference to a prior AD (movement from AD/HILLER 12/23) requires operators to reconcile historical compliance records to ensure current obligations (Note)."],"plain_english_summary":"This directive mandates inspection of the main rotor blade anti‑node bar on specified Hiller UH‑12 series helicopters (including certain STC conversions) when fitted with Parsons P/N 2253‑1101‑04 blades, to be done per Hiller Service Bulletin UH‑12‑51‑5. It affects aircraft owners, operators and maintenance organisations (and Hiller as the SB source). The check responds to reports some anti‑node bars may have machine‑cut threads that could be unsafe; owners/operators bear inspection and repair costs."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive with narrow, specific scope targeting particular helicopter models and components. The note indicates this is a reorganization of existing requirements (moved from AD/HILLER 12/23) rather than an expansion of scope."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined terms implicitly referenced (STC numbers treated as identifiers rather than defined terms)","No cross-references to other legislation or regulations beyond the parenthetical reference to Civil Aviation Regulations 1998, Part 39","Simple conditional logic: applicability determined by specific model numbers and part numbers","Single compliance requirement referring to external document (Service Bulletin)","No nested exceptions or conditional clauses"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nThis directive requires owners and operators of specific **Hiller UH-12 series helicopters** to inspect the **main rotor blade anti-node bars** (a component that helps reduce vibration in the rotor blades). The inspection applies only to helicopters equipped with specific rotor blades made by Parsons (part number 2253-1101-04).\n\n**Who it affects:**\n- Owners and operators of Hiller UH-12D, UH-12E, UH-12E4, H-23F, and OH-23G helicopters\n- Also applies to models converted using specific Supplemental Type Certificates (STCs — basically modifications approved by aviation authorities): STC178WE or STC177WE\n\n**Why it matters:**\nThe manufacturer discovered that some anti-node bars have **machine-cut threads** that may need inspection to ensure they are safe. This is a critical safety issue because the main rotor is what keeps the helicopter in the air — if it fails, the aircraft crashes.\n\n**Key detail:**\nThis requirement was moved from an older directive (AD/HILLER 12/23) to this new one (AD/HILLER 12/28). Operators must follow the inspection procedures outlined in **Hiller Aviation Service Bulletin UH-12-51-5**."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hiller-12-28-main-rotor-blade-anti-node-bar-inspection","history":"/api/acts/ad-hiller-12-28-main-rotor-blade-anti-node-bar-inspection/history","analysis":"/api/acts/ad-hiller-12-28-main-rotor-blade-anti-node-bar-inspection/analysis","conflicts":"/api/acts/ad-hiller-12-28-main-rotor-blade-anti-node-bar-inspection/conflicts","importantCases":"/api/acts/ad-hiller-12-28-main-rotor-blade-anti-node-bar-inspection/important-cases","documents":"/api/acts/ad-hiller-12-28-main-rotor-blade-anti-node-bar-inspection/documents"}}