{"id":"F2006B04579","name":"AD/BELL 212/47 - Lower Planetary Spider Gear","slug":"ad-bell-212-47-lower-planetary-spider-gear","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114310,"registerId":"commonwealth-F2006B04579-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 212/47 - Lower Planetary Spider Gear","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 212 Series Helicopters\n\n \n\nAD/BELL 212/47 Lower Planetary Spider Gear 9/91\n\nDM\n\n \n\nApplicability: All Models.\n\n \n\nRequirement: Action in accordance with Bell Alert SB No. 212-91-66.\n\nCompliance: As directed in the Requirement Document with a revised effective date 12 July 1991. Background:               A special inspection of the main gearbox lower planetary spider gear P/N 204-040-\n\n785-003 has been introduced by the manufacturer after fatigue cracking has been detected.\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\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's scope as issued remains focused on Bell 212 helicopters and the specific lower planetary spider gear identified by part number 204-040-785-003. It requires action in accordance with Bell Alert SB No. 212-91-66 and sets a revised effective date of 12 July 1991; no expansion or narrowing of that scope is indicated in the text provided (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Directive delegates technical detail to an external document (Bell Alert SB No. 212-91-66) rather than containing inspection procedures itself (Requirement).","Applicability covers all Bell 212 models, increasing the population affected but without quantifying it (Applicability).","Technical subject matter: inspection for fatigue cracking of a specific gearbox part P/N 204-040-785-003 requires specialist maintenance capability (Background).","Compliance timing is fixed by a revised effective date (12 July 1991), creating a deadline operators must meet (Compliance).","Sparse text: the AD is short and procedural details, intervals, and corrective actions are contained only in the referenced service bulletin (Requirement)."],"plain_english_summary":"What this directive does (mechanically)\n\n- It requires operators of Bell 212 series helicopters to carry out the inspection and any related actions set out in the manufacturer's Alert Service Bulletin Bell Alert SB No. 212-91-66 (Requirement).\n- The directive applies to all Bell 212 models (Applicability).\n- The compliance timing is as specified in the Requirement Document, with a revised effective date of 12 July 1991 (Compliance).\n\nWhy this was issued (stated reason)\n\n- The manufacturer introduced a special inspection after fatigue cracking was detected in the main gearbox lower planetary spider gear, part number 204-040-785-003 (Background).\n\nWho decides and who acts\n\n- The regulator has made compliance with the manufacturer's Alert SB mandatory for the affected aircraft (Requirement). The Alert SB itself sets the specific inspection steps and any corrective actions.\n- Owners/operators of affected Bell 212 helicopters must implement the inspection and any remedial work required by the Alert SB (Applicability; Requirement).\n\nPractical effects, incentives and costs (source-grounded)\n\n- Compliance shifts the immediate operational task onto aircraft owners/operators: they must arrange the inspection and any repairs specified by Bell Alert SB No. 212-91-66 (Requirement). The directive does not itself set inspection procedures or intervals; those details are in the referenced Alert SB (Requirement).\n- The directive's compliance date was revised to 12 July 1991, which fixes the timing for when the actions become mandatory (Compliance).\n- The Background statement identifies fatigue cracking of gearbox part P/N 204-040-785-003 as the technical trigger for the inspection; that links the regulatory requirement directly to a specific component failure risk (Background).\n\nImplementation and risk notes (source-grounded)\n\n- The AD delegates technical detail to the manufacturer’s Alert SB (Requirement). That delegation means the exact scope of work, inspection methods, intervals and any part replacement instructions are contained in the SB rather than in this short directive.\n- Because the directive covers \"All Models,\" the universe of affected helicopters is broad; the directive does not itself quantify affected aircraft or estimate the resource burden (Applicability).\n\nSource citations\n\n- Applicability: \"All Models.\" (Applicability)\n- Requirement: \"Action in accordance with Bell Alert SB No. 212-91-66.\" (Requirement)\n- Compliance: \"As directed in the Requirement Document with a revised effective date 12 July 1991.\" (Compliance)\n- Background: \"A special inspection of the main gearbox lower planetary spider gear P/N 204-040-785-003 has been introduced by the manufacturer after fatigue cracking has been detected.\" (Background)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete Airworthiness Directive with a single, specific purpose: mandating inspection of one helicopter component. It has not expanded beyond its original technical safety intent. ADs are by nature narrow, targeted instruments issued under broader Civil Aviation Regulations."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined term implicitly referenced (the part number P/N 204-040-785-003)","No nested legislative cross-references — refers only to external technical document (Bell Alert SB No. 212-91-66)","Simple conditional structure: applicability → requirement → compliance deadline","Single purpose: mandate one specific inspection","No exceptions or exemptions stated","Technical but not legally complex — assumes aviation engineering knowledge rather than legal expertise"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) issued by Australia's Civil Aviation Safety Authority (CASA) for Bell 212 series helicopters.\n\n**What it does:** It mandates a special inspection of a specific helicopter part — the \"lower planetary spider gear\" (part number 204-040-785-003) in the main gearbox. This gear is a critical component that helps transfer power from the engine to the rotor blades.\n\n**Why it matters:** The manufacturer (Bell Helicopter Textron) discovered fatigue cracking in this gear. Fatigue cracking means tiny cracks develop from repeated stress, which can lead to sudden catastrophic failure. If this gear fails in flight, the helicopter could lose rotor power and crash.\n\n**Who must comply:** All operators of Bell 212 series helicopters must follow the inspection procedures outlined in Bell Alert Service Bulletin No. 212-91-66 by the specified deadline (12 July 1991).\n\n**The bottom line:** This is a safety-critical maintenance order. It doesn't change the law itself — it's a technical instruction issued under existing aviation regulations requiring immediate action to prevent mechanical failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-212-47-lower-planetary-spider-gear","history":"/api/acts/ad-bell-212-47-lower-planetary-spider-gear/history","analysis":"/api/acts/ad-bell-212-47-lower-planetary-spider-gear/analysis","conflicts":"/api/acts/ad-bell-212-47-lower-planetary-spider-gear/conflicts","importantCases":"/api/acts/ad-bell-212-47-lower-planetary-spider-gear/important-cases","documents":"/api/acts/ad-bell-212-47-lower-planetary-spider-gear/documents"}}