{"id":"F2006B04398","name":"AD/BELL 205/61 - Main Transmission Lower Planetary Spider","slug":"ad-bell-205-61-main-transmission-lower-planetary-spider","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44223,"registerId":"commonwealth-F2006B04398-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 205/61 - Main Transmission Lower Planetary Spider","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nBell Helicopter Textron 205 Series Helicopters\n\nAD/BELL 205/61 Main Transmission Lower Planetary Spider 2/95\n\nApplicability: All Bell 205A, 205A-1 and 205B series helicopters with main transmission lower planetary spider P/N 412-040-785-101 installed.\n\nRequirement: Retire the spider in accordance with Bell Alert Service Bulletin ASB 205-93-54 for Bell 205A and 205A-1 and ASB 205B-93-16 for Bell 205B series helicopters.\n\nNote 1: FAA AD 94-18-09 Amdt 39-9022 refers. Spider P/N 412-040-785-103 is not limited by this AD.\n\nCompliance: Retire the spiders before 2500 hours time in service or within 100 hours time in service after 2 February 1995, whichever is the later.\n\nBackground: Five failures of the main transmission lower planetary spider have been experienced during the manufacturer’s fatigue tests. Accordingly a fatigue life has been established to prevent in service failures.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD does not expand or alter the original safety target: it stays narrowly focused on retiring a specific component (P/N 412-040-785-101) from specified Bell 205 variants to prevent fatigue-related failures. The directive prescribes a retirement life and points operators to the manufacturer’s ASBs for the means of compliance; it does not broaden applicability to other parts or helicopter models, nor does it create additional regulatory obligations beyond the retirement and associated compliance timing (Applicability; Requirement; Compliance; Background; Note 1)."},"complexity_factors":["Narrow applicability limited to specific helicopter models and a single part number (Applicability)","Clear, single mandated action (retirement) tied to manufacturer ASBs rather than a new technical procedure created by the regulator (Requirement)","Fixed compliance metric based on hours time in service and a date-based grace period (Compliance)","Reference to an alternate part number that is excluded from the AD, creating a substitution pathway (Note 1)","Dependence on operators' time-in-service tracking and maintenance scheduling creates operational coordination but not legal ambiguity (Compliance)","Cross-reference to FAA AD and manufacturer ASBs requires users to consult multiple documents for technical details (Requirement; Note 1)"],"plain_english_summary":"This AD requires owners/operators of Bell 205A, 205A‑1 and 205B helicopters to retire main transmission lower planetary spider P/N 412‑040‑785‑101 by 2,500 hours TIS (or within 100 hours after 2 Feb 1995, if later), following the manufacturer’s Alert Service Bulletin procedures. It responds to fatigue-test failures of the spider to prevent in‑service breakage, shifts replacement costs and downtime onto operators and maintenance providers, and explicitly does not apply to spider P/N 412‑040‑785‑103."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused specifically on one defective helicopter component. It has not expanded beyond its original safety purpose of mandating retirement of a fatigue-limited part."},"complexity_factors":["Single, clearly defined applicability criterion (specific part number on specific aircraft models)","Straightforward compliance requirement with two alternative deadlines (whichever is later)","No defined terms section or interpretation provisions","No cross-references to other legislation beyond a single reference to FAA AD for background context","Single operational requirement (retire the part) with no exceptions, exemptions, or conditional logic","Document length: approximately 150 words"],"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 specific Bell 205 series helicopters used in Australia.\n\n**What it does:**\n- **Targets:** Bell 205A, 205A-1, and 205B helicopters that have a specific part installed — the \"main transmission lower planetary spider\" with part number 412-040-785-101. This is a critical component in the helicopter's main gearbox that helps transfer power from the engine to the rotor blades.\n- **Requires:** Owners and operators must permanently remove (\"retire\") this specific part from service before it reaches 2,500 flight hours, or within 100 flight hours after 2 February 1995 — whichever gives them more time.\n- **Why:** The manufacturer found this part can fail due to metal fatigue after extended use. Five failures occurred during laboratory fatigue testing, so a \"safety limit\" (fatigue life) was set to prevent the part from breaking during actual flight, which could cause a catastrophic crash.\n\n**Who it affects:**\n- Australian operators of Bell 205 series helicopters with this specific part installed.\n- Maintenance engineers responsible for tracking component flight hours and scheduling replacements.\n\n**Why it matters:**\nHelicopter transmissions operate under extreme stress. If this spider component fails in flight, the helicopter could lose rotor power entirely. This directive forces replacement before the dangerous fatigue threshold, preventing potential fatal accidents."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-205-61-main-transmission-lower-planetary-spider","history":"/api/acts/ad-bell-205-61-main-transmission-lower-planetary-spider/history","analysis":"/api/acts/ad-bell-205-61-main-transmission-lower-planetary-spider/analysis","conflicts":"/api/acts/ad-bell-205-61-main-transmission-lower-planetary-spider/conflicts","importantCases":"/api/acts/ad-bell-205-61-main-transmission-lower-planetary-spider/important-cases","documents":"/api/acts/ad-bell-205-61-main-transmission-lower-planetary-spider/documents"}}