{"id":"F2006B10351","name":"AD/HILLER 12/23 Amdt 1 - Main Rotor Blade, Anti Node Weight Retention - Inspection","slug":"ad-hiller-12-23-amdt-1-main-rotor-blade-anti-node-weight-retention-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56121,"registerId":"commonwealth-F2006B10351-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HILLER 12/23 Amdt 1 - Main Rotor Blade, Anti Node Weight Retention - Inspection","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)  \nHiller UH-12 Series Helicopters\n\nAD/HILLER 12/23\n\nAmdt 1\n\n  \n\nMain Rotor Blade, Anti Node Weight Retention \\- Inspection\n\n  \n5/80\n\nApplicability: All models UH-12D, UH-12E and UH-12E(4 place) fitted with main rotor blades assembly “Parson” P/N 2253-1101-03.\n\nRequirement: To prevent failure of the anti node retention system of the main rotor blade of referenced P/N perform the following:\n\n    Remove the antinode bar assembly per para. 4.53 of UH-12E/ UH-12L series structural repair manual.\n\n    2. Clean the thread outboard of the antinode weight anchor nut.\n\n    3. Using a micrometer, measure the thread major diameter\n\n    (a) If the rod thread major diameter is between .3678 and .3750 inches reassemble rod and return the blade to service.\n\n    (b) If the rod thread major diameter is .3677 inches or less the antinode rod must be replaced before the blade is returned to service.\n\nNote. Hiller Aviation SB No. 51-4 refers.\n\nCompliance: Unless already accomplished, within 10 hours time in service after 16 October 1978.\n\nBackground: The inspection requirements for Parsons P/N 2253-1101-04 blades are now promulgated in AD/HILLER 12/28.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing Airworthiness Directive. The amendment simply clarifies that inspection requirements for a different part number (2253-1101-04) have been moved to a separate directive (AD/HILLER 12/28). The core safety mandate — inspecting the anti-node weight retention on P/N 2253-1101-03 blades — remains unchanged from the original 1978 directive."},"complexity_factors":["Very short document (approximately 200 words)","Only 3 procedural steps required","Single defined term (applicability limited to specific part number)","Simple binary decision tree (measure thread → if X do Y, if Z do A)","No cross-references to other legislation (only references a Service Bulletin and another AD for background)","Clear, imperative language throughout"],"plain_english_summary":"This CASA Airworthiness Directive legally requires owners/operators of Hiller UH-12 (UH-12D/E and UH-12E 4-place) helicopters fitted with Parson main rotor blades (P/N 2253-1101-03) to inspect and micrometer-measure the anti-node weight’s threaded rod. If the thread diameter is below the specified limit, the rod must be replaced before further flight. Compliance within 10 flight hours after 16 October 1978 is mandatory — it prevents loss of the anti-node weight and potential catastrophic rotor failure."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD as published targets Parson P/N 2253‑1101‑03 blades and specifies inspection and replacement criteria. The Background notes that inspection requirements for P/N 2253‑1101‑04 blades are handled separately in AD/HILLER 12/28, but this text does not expand or narrow the applicability stated here (Applicability; Background)."},"complexity_factors":["Technical precision: requires micrometer measurement against tight tolerances (.3677 in threshold; .3678–.3750 in acceptable range) (Requirement para. 3).","Procedure dependency: removal must follow para. 4.53 of the UH‑12E/UH‑12L structural repair manual, so operators need access to and familiarity with that manual (Requirement para. 1).","Parts‑specific applicability: limited to blades fitted with Parson P/N 2253‑1101‑03, so operators must verify part numbers before action (Applicability).","Short compliance window: mandatory within 10 hours time‑in‑service after 16 October 1978, creating scheduling and downtime pressure (Compliance).","Potential cost and logistics: failed measurement forces immediate rod replacement before returning the blade to service, imposing parts, labour and possible grounding costs (Requirement para. 3(b)).","External references: notes Hiller Service Bulletin No. 51‑4 and a separate AD for P/N 2253‑1101‑04, requiring cross‑checking of additional documents (Note; Background).","Low discretion: binary outcome based on measured diameter leaves little room for judgement—either reassemble or replace (Requirement para. 3(a)–(b))."],"plain_english_summary":"This directive requires owners/operators of Hiller UH‑12D, UH‑12E and UH‑12E (4‑place) helicopters fitted with Parson main rotor blades (P/N 2253‑1101‑03) to inspect the anti‑node weight retention: remove the antinode bar, clean the threads and measure the rod thread major diameter with a micrometer, then reassemble or replace the rod depending on the measurement. Its aim is to prevent anti‑node retention failure; compliance is mandatory within 10 hours time‑in‑service after 16 October 1978, and operators bear inspection, measurement and any replacement costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hiller-12-23-amdt-1-main-rotor-blade-anti-node-weight-retention-inspection","history":"/api/acts/ad-hiller-12-23-amdt-1-main-rotor-blade-anti-node-weight-retention-inspection/history","analysis":"/api/acts/ad-hiller-12-23-amdt-1-main-rotor-blade-anti-node-weight-retention-inspection/analysis","conflicts":"/api/acts/ad-hiller-12-23-amdt-1-main-rotor-blade-anti-node-weight-retention-inspection/conflicts","importantCases":"/api/acts/ad-hiller-12-23-amdt-1-main-rotor-blade-anti-node-weight-retention-inspection/important-cases","documents":"/api/acts/ad-hiller-12-23-amdt-1-main-rotor-blade-anti-node-weight-retention-inspection/documents"}}