{"id":"F2006B04344","name":"AD/BELL 204/40 - Main Gearbox - Planetary Spider","slug":"ad-bell-204-40-main-gearbox-planetary-spider","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44159,"registerId":"commonwealth-F2006B04344-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.","sortOrder":0},{"sectionNumber":"AD/BELL 204/40 Main Gearbox - Planetary ","sectionType":"part","heading":"AD/BELL 204/40 Main Gearbox - Planetary Spider 8/2000","content":"# AD/BELL 204/40 Main Gearbox \\- Planetary Spider 8/2000\n\nApplicability: Model 204B with a main rotor gearbox lower planetary spider P/N 204-040-785-003 installed.\n\nRequirement: Remove the spider from the transmission and inspect for fatigue cracking using an approved magnetic particle inspection method.\n\nAny cracking is unacceptable.\n\nNote: FAA AD 93-17-12 refers.\n\nCompliance: Unless already accomplished within the last 2 400 hours time in service, within 600 hours time in service after 29 July 1994; thereafter at intervals not exceeding 3 100 hours.\n\nThis Airworthiness Directive becomes effective on 10 August 2000.\n\nBackground: A fatigue failure of the transmission spider would result in failure of the gearbox and loss of control of the helicopter. This directive also follows the re-introduction of the AD Series after sixteen years.\n\n![](image.003.png)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 6 July 2000\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 12 July 2000.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies only to Model 204B helicopters with the specified spider P/N and mandates removal and magnetic particle inspection at stated intervals. The scope is consistent with the stated safety objective in the Background and does not broaden or narrow applicability beyond that technical focus."},"complexity_factors":["Narrow technical scope tied to a single part and airframe model (Applicability)","Specific approved inspection method required (magnetic particle inspection) (Requirement)","Non-standard compliance timing: conditional initial requirement (unless done within last 2,400 hours), a 600‑hour window after 29 July 1994, then recurring intervals not exceeding 3,100 hours (Compliance)","Safety-critical consequence drives mandatory compliance and limits discretion (Background)","Reference to an external FAA AD creates cross-jurisdictional traceability (Note/Requirement)"],"plain_english_summary":"Requires operators of Bell Model 204B helicopters fitted with the lower planetary spider P/N 204-040-785-003 to remove that spider and inspect it for fatigue cracking using an approved magnetic particle inspection; any cracking is unacceptable (Applicability; Requirement). Compliance times are specified for initial and recurring inspections. The measure addresses the risk that spider fatigue failure would cause gearbox failure and loss of control. Operators pay for removal, inspection and any replacement; CASA enforces the directive under CAR 1998 subreg 39.1(1)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical failure mode in a specific aircraft component. It has not expanded beyond its original purpose of preventing gearbox failure through mandatory inspection."},"complexity_factors":["Single, clearly defined applicability criterion (one helicopter model with one specific part number)","Straightforward two-step requirement: remove and inspect, with binary pass/fail outcome","Simple compliance schedule with only two conditions (initial inspection deadline + recurring interval)","No defined terms section, no cross-references to other legislation beyond a non-binding note about a US FAA directive","No exceptions, exemptions, or conditional logic","Total length under 300 words"],"plain_english_summary":"This CASA safety order targets Bell Model 204B helicopters fitted with the main rotor gearbox lower planetary spider, requiring removal and magnetic inspection for fatigue cracks and mandatory replacement if any cracking is found.  \n\nInspections are required within 600 flight hours if not done in the prior 2,400 hours, and thereafter every 3,100 flight hours — to prevent catastrophic gearbox failure and loss of control affecting operators of these older helicopters."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-204-40-main-gearbox-planetary-spider","history":"/api/acts/ad-bell-204-40-main-gearbox-planetary-spider/history","analysis":"/api/acts/ad-bell-204-40-main-gearbox-planetary-spider/analysis","conflicts":"/api/acts/ad-bell-204-40-main-gearbox-planetary-spider/conflicts","importantCases":"/api/acts/ad-bell-204-40-main-gearbox-planetary-spider/important-cases","documents":"/api/acts/ad-bell-204-40-main-gearbox-planetary-spider/documents"}}