{"id":"F2006B04420","name":"AD/BELL 206/107 - Main Rotor Mast","slug":"ad-bell-206-107-main-rotor-mast","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44245,"registerId":"commonwealth-F2006B04420-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 206/107 - Main Rotor Mast","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nBell Helicopter Textron Canada (BHTC) 206 and Agusta Bell 206 Series Helicopters\n\nAD/BELL 206/107 Main Rotor Mast 8/87 DM\n\nApplicability: All Model 206A, 206B, 206L, 206L-1 and 206L-3 helicopters fitted with main rotor mast P/N 206-010-332-121 or P/N 206-040-535-105 with serial numbers listed in the Requirement Documents.\n\nRequirement: Remove from service those masts listed in the following documents: For models 206A and 206B: Bell Alert Service Bulletin 206-87-37. For models 206L series: Bell Alert Service Bulletin 206L-87-44.\n\nNote: FAA Telex AD 87-10-11 refers.\n\nCompliance: Within 25 hours time in service after 1 June 1987.\n\nBackground: A batch of main rotor masts has been manufactured from material lots which may contain metallurgical imperfections. These inclusions may degrade the fatigue properties of the masts and could lead to catastrophic failure in flight.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete safety directive addressing a specific manufacturing defect in specific helicopter models. It has not expanded beyond its original purpose of grounding affected rotor masts."},"complexity_factors":["Very short document (under 300 words)","Only 2 defined part numbers and 5 helicopter models specified","Single, clear compliance action (remove affected masts)","No nested exceptions or conditional logic","Cross-references are limited to 2 external service bulletins and 1 FAA telex, all serving as reference material rather than operational dependencies","Straightforward deadline calculation (25 hours after fixed date)"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it like a factory recall for aircraft, but legally enforceable.\n\n**What it does:** It orders the immediate removal from service of specific main rotor masts (the central shaft that connects the helicopter's rotor blades to the engine) on certain Bell helicopter models. These masts came from manufacturing batches with potential metal defects that could cause the mast to crack and fail catastrophically in flight.\n\n**Who it affects:** Owners and operators of:\n- Bell 206A and 206B helicopters\n- Bell 206L, 206L-1, and 206L-3 helicopters\n\n—but **only** if their helicopter has a main rotor mast with specific part numbers (P/N 206-010-332-121 or P/N 206-040-535-105) AND serial numbers listed in the referenced Bell service bulletins.\n\n**What must be done:** Operators must check their maintenance records against two technical documents (Bell Alert Service Bulletins 206-87-37 and 206L-87-44). If their mast is on the list, it must be removed from the helicopter within **25 flight hours** after 1 June 1987.\n\n**Why it matters:** A failed main rotor mast means the rotor blades detach from the helicopter. This is not survivable. The directive addresses a known manufacturing defect in the metal that could lead to fatigue cracking — essentially, the mast could snap after repeated stress from flight operations.\n\n**Key point:** This is **not optional**. Non-compliance means the aircraft cannot legally fly in Australian airspace."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD's scope is confined to removing from service the specific main rotor mast part numbers and the serial numbers listed in the referenced service bulletins for the listed 206 helicopter models. The directive implements that targeted removal for safety reasons stated in the Background and does not broaden coverage beyond the part numbers, models, and serial-number lists identified in the Requirement and Applicability sections."},"complexity_factors":["Narrow applicability to specific helicopter models and two precise part numbers (Applicability).","Identification of affected items depends on serial numbers listed in external service bulletins (Requirement).","Short, fixed compliance window (25 hours time in service after 1 June 1987) creates scheduling pressure (Compliance).","Safety rationale is technical (metallurgical imperfections affecting fatigue) requiring engineering judgment to assess risk but not to comply with the mandated removal (Background).","References to external documents (two Bell Alert Service Bulletins and an FAA Telex) mean operators must consult multiple sources to determine exact scope (Requirement; Note)."],"plain_english_summary":"The directive requires owners/operators of Bell/Agusta Bell 206 series helicopters to check mast serial numbers against two Bell Alert Service Bulletins and remove from service any listed main rotor masts within 25 hours TIS after 1 June 1987. It responds to suspected metallurgical inclusions that may reduce fatigue strength and risk in‑flight rotor failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-206-107-main-rotor-mast","history":"/api/acts/ad-bell-206-107-main-rotor-mast/history","analysis":"/api/acts/ad-bell-206-107-main-rotor-mast/analysis","conflicts":"/api/acts/ad-bell-206-107-main-rotor-mast/conflicts","importantCases":"/api/acts/ad-bell-206-107-main-rotor-mast/important-cases","documents":"/api/acts/ad-bell-206-107-main-rotor-mast/documents"}}