{"id":"F2006B10367","name":"AD/HILLER 12/42 - Main Rotor Mast","slug":"ad-hiller-12-42-main-rotor-mast","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115991,"registerId":"commonwealth-F2006B10367-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HILLER 12/42 - Main Rotor Mast","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 12/42 Main Rotor Mast 6/91 DM\n\nApplicability: All models.\n\nRequirement: Perform a detailed visual inspection of the main rotor mast at both ends of the two elongated collective control terminal pin slots.\n\n![](image.002.png)  \n\nCompliance: Prior to further flight unless accomplished within the previous 100 hours’ time in service, and thereafter at intervals not to exceed 100 hours’ time in service, and immediately upon the onset of any unusual vibration or any stiffness or binding of the collective control.\n\nBackground: Two aircraft have recently been reported as having cracks emanating from the ends of the elongated slots. One aircraft was reportedly cracked through 75% of its cross section while the other was reported to have two cracks 50 mm long. Indications in the worst affected aircraft included lateral and vertical vibration and stiffness and binding of the collective pitch control.\n\n“Emergency Airworthiness Advice for Hiller UH-12 Helicopter” refers.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1404},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific mechanical defect in a single aircraft type. The scope remains narrowly focused on main rotor mast inspections for Hiller UH-12 helicopters with no evidence of expansion beyond this original safety purpose."},"complexity_factors":["Technical aviation terminology requires specialized engineering knowledge to interpret (e.g., 'collective control terminal pin slots')","Conditional compliance trigger ('unless accomplished within the previous 100 hours') creates a dual-track deadline","Multiple timing triggers (pre-flight, recurring 100-hour intervals, and immediate upon symptoms)"],"plain_english_summary":"This rule requires owners and operators of Hiller UH-12 helicopters to urgently inspect the main rotor mast for cracks at the collective terminal-pin slots, with checks before the next flight (unless done within 100 flight hours), every 100 hours thereafter, and immediately if unusual vibration or stiff/binding collective controls occur. It responds to discovered cracks—one nearly through the mast—that could lead to catastrophic rotor separation and a crash."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hiller-12-42-main-rotor-mast","history":"/api/acts/ad-hiller-12-42-main-rotor-mast/history","analysis":"/api/acts/ad-hiller-12-42-main-rotor-mast/analysis","conflicts":"/api/acts/ad-hiller-12-42-main-rotor-mast/conflicts","importantCases":"/api/acts/ad-hiller-12-42-main-rotor-mast/important-cases","documents":"/api/acts/ad-hiller-12-42-main-rotor-mast/documents"}}