{"id":"F2006B04682","name":"AD/BELL 412/9 Amdt 1 - Main Rotor Blade Pitch Horns - Inspection","slug":"ad-bell-412-9-amdt-1-main-rotor-blade-pitch-horns-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44434,"registerId":"commonwealth-F2006B04682-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 412/9 Amdt 1 - Main Rotor Blade Pitch Horns - 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)  Bell Helicopter Textron 412 Series Helicopters\n\n \n\nAD/BELL 412/9\n\nAmdt 1\n\n\nMain Rotor Blade Pitch Horns - Inspection 2/85\n\n \n\nApplicability: All models fitted with main rotor pitch horn P/N 412-010-149-105 and pins P/N 412- 010-180-101.\n\n \n\nDocument: Bell Alert Service Bulletin 412-83-13.\n\n \n\nCompliance: Part 1 - At the next 20 hour inspection after 12 September 1983 and each 20 hour inspection thereafter.\n\n \n\nPart 2 - Each time the pitch horn is removed.\n\n \n\nBackground: The manufacturer has introduced a new horn configuration with improved corrosion protection. This directive has been amended to limit the requirement for repetitive inspections to aircraft fitted with the older design pitch horns and pins. Bell Alert SB No. 412-84-18 refers.\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":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"The original directive likely applied to all Bell 412 pitch horns. Amendment 1 narrows the scope to only aircraft with the older design (P/N 412-010-149-105 and pins P/N 412-010-180-101), excluding those with the improved corrosion-resistant configuration. This is a scope reduction rather than expansion."},"complexity_factors":["Very short document (under 200 words)","Only 2 defined part numbers referenced","Simple two-part compliance structure with clear time/usage triggers","No cross-references to other legislation beyond a single Alert Service Bulletin","Single amendment narrowing scope rather than expanding it","No conditional logic or nested exceptions"],"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 as a \"recall notice\" for aircraft, but legally binding.\n\n**What it does:** It requires owners and operators of Bell 412 series helicopters to inspect specific parts of the main rotor — the \"pitch horns\" (components that help control blade angle) and their connecting pins — for corrosion damage.\n\n**Who it affects:** Anyone operating Bell 412 helicopters fitted with specific older part numbers: pitch horn P/N 412-010-149-105 and pins P/N 412-010-180-101.\n\n**What must be done:**\n- **Part 1:** Inspect these parts every 20 flight hours (starting from the first 20-hour check after 12 September 1983)\n- **Part 2:** Inspect again every time the pitch horn is removed for maintenance\n\n**Why it matters:** Corrosion in rotor components can lead to mechanical failure and catastrophic accidents. The manufacturer (Bell) released a new, better-protected design, so this directive only applies to helicopters still using the older, corrosion-prone version. This amendment (Amdt 1) narrows the original rule to target only the older parts, reducing unnecessary inspections for upgraded aircraft."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The directive was amended to limit the requirement for repetitive inspections to aircraft fitted with the older-design pitch horns and pins. The manufacturer introduced a new horn configuration with improved corrosion protection, and the amendment narrows repetitive inspection obligations to legacy parts (see Background and references to Bell Alert SB No. 412-84-18)."},"complexity_factors":["Narrow applicability tied to specific part numbers (P/N 412-010-149-105 and P/N 412-010-180-101) requires operators to track fitted components precisely.","Two-part compliance schedule: (1) recurring 20‑hour inspections beginning after a fixed date; (2) inspection whenever the pitch horn is removed — different triggers increase administrative steps.","Reliance on an external document (Bell Alert Service Bulletin 412-83-13) for inspection procedure creates dependency on manufacturer's instructions.","Amendment introduces conditional scope (only older-design horns/pins), so operators must distinguish between legacy and new-configured parts.","Implementation risk and ongoing compliance burden fall on operators to schedule inspections, record compliance, and apply the correct parts status."],"plain_english_summary":"This airworthiness directive requires Bell 412 helicopters fitted with pitch horn P/N 412-010-149-105 and pins P/N 412-010-180-101 to follow Bell Alert Service Bulletin 412-83-13: inspect at the next 20‑hour check after 12 September 1983 and at every 20‑hour inspection thereafter, and each time the pitch horn is removed. The amendment confines repetitive inspections to aircraft with the older horn/pin design because the manufacturer introduced a new horn with improved corrosion protection. Operators bear the inspection and compliance costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-412-9-amdt-1-main-rotor-blade-pitch-horns-inspection","history":"/api/acts/ad-bell-412-9-amdt-1-main-rotor-blade-pitch-horns-inspection/history","analysis":"/api/acts/ad-bell-412-9-amdt-1-main-rotor-blade-pitch-horns-inspection/analysis","conflicts":"/api/acts/ad-bell-412-9-amdt-1-main-rotor-blade-pitch-horns-inspection/conflicts","importantCases":"/api/acts/ad-bell-412-9-amdt-1-main-rotor-blade-pitch-horns-inspection/important-cases","documents":"/api/acts/ad-bell-412-9-amdt-1-main-rotor-blade-pitch-horns-inspection/documents"}}