{"id":"F2006B10359","name":"AD/HILLER 12/33 - Tail Rotor Blade P/N 55073 - Inspection","slug":"ad-hiller-12-33-tail-rotor-blade-p-n-55073-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115973,"registerId":"commonwealth-F2006B10359-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HILLER 12/33 - Tail Rotor Blade P/N 55073 - 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 12/33 Tail Rotor Blade P/N 55073 - Inspection 11/81\n\nApplicability: All UH-12 series fitted with tail rotor blades P/N. 55073. Document:  Hiller Aviation SB No. 55-1.\n\nCompliance: At each daily or overnight inspection.\n\n \n\nNote: This inspection may be performed and certified for by the pilot in command.\n\n \n\nBackground: There is a possibility of the vent holes located at the inboard and outboard ends of the blade becoming obstructed with dirt or debris.\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":2,"scope_assessment":{"changed":false,"description":"The directive's scope is a targeted, model-and-part-specific inspection requirement: it applies only to UH-12 series helicopters fitted with tail rotor blades P/N 55073 (Applicability). The instrument, as published, does not expand beyond that population or add other parts or models; it prescribes inspection frequency (each daily or overnight inspection) and references a specific service bulletin for procedure (Compliance; Document)."},"complexity_factors":["Narrow applicability limited to UH-12 series fitted with tail rotor blades P/N 55073 (Applicability).","Single, simple action required (visual check at each daily or overnight inspection) (Compliance).","Pilot in command may perform and certify inspection, lowering administrative complexity but transferring judgment to pilot (Note).","Reference to an external service bulletin (Hiller Aviation SB No. 55-1) requires operators to consult another document for procedural detail (Document).","No technical thresholds or corrective-action procedures are included in the AD text, increasing reliance on the service bulletin and operator maintenance practice (Background; Document)."],"plain_english_summary":"The directive requires daily/overnight inspections of tail-rotor blades P/N 55073 on Hiller UH‑12 helicopters to check for obstructed vent holes (per Hiller Aviation SB No. 55‑1). It lets the pilot in command perform and certify the check, placing routine inspection responsibility on operators to clean or seek maintenance if obstructions are found."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused specifically on Hiller UH-12 helicopter tail rotor blade inspections. It has not expanded beyond its original narrow technical purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined term implicitly used (P/N = Part Number)","No cross-references to other legislation sections","Simple unconditional requirement: inspect at each daily/overnight check","Single exception/note clarifying pilot authority to perform inspection","No nested conditions or exceptions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to **Hiller UH-12 series helicopters** that use a specific tail rotor blade part number (P/N 55073).\n\n**What it requires:**\n- **Who must comply:** Owners and operators of affected helicopters\n- **What to do:** Inspect the tail rotor blades at every daily or overnight inspection\n- **What to look for:** Blocked vent holes at both ends of the blade (these holes let air escape; if clogged with dirt or debris, they can cause safety problems)\n- **Who can do it:** Unlike many maintenance tasks, this inspection can be done and signed off by the **pilot in command** (the person flying the helicopter) — not just a licensed mechanic\n\n**Why it matters:**\nBlocked vent holes in tail rotor blades can lead to dangerous flight conditions. This AD ensures regular checks happen frequently enough to catch problems before they cause accidents.\n\n**Key details:**\n- Based on **Hiller Aviation Service Bulletin No. 55-1**\n- Directive number: AD/HILLER 12/33\n- Originally issued: November 1981 (11/81)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-hiller-12-33-tail-rotor-blade-p-n-55073-inspection","history":"/api/acts/ad-hiller-12-33-tail-rotor-blade-p-n-55073-inspection/history","analysis":"/api/acts/ad-hiller-12-33-tail-rotor-blade-p-n-55073-inspection/analysis","conflicts":"/api/acts/ad-hiller-12-33-tail-rotor-blade-p-n-55073-inspection/conflicts","importantCases":"/api/acts/ad-hiller-12-33-tail-rotor-blade-p-n-55073-inspection/important-cases","documents":"/api/acts/ad-hiller-12-33-tail-rotor-blade-p-n-55073-inspection/documents"}}