{"id":"F2006B04572","name":"AD/BELL 212/40 - Main Transmission Spiral Bevel Gear","slug":"ad-bell-212-40-main-transmission-spiral-bevel-gear","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114302,"registerId":"commonwealth-F2006B04572-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 212/40 - Main Transmission Spiral Bevel Gear","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBell Helicopter Textron 212 Series Helicopters\n\nAD/BELL 212/40 Main Transmission Spiral Bevel Gear 7/89\n\nApplicability: All 212 series helicopters with main transmission containing spiral bevel gear P/N 204-040-701-103 with less than 250 hours total time in service.\n\nRequirement: 1. Remove and inspect the transmission internal sump oil filter for evidence of metal contamination (eg, steel particles in splinter, granular or flake form). If metal contamination is evident replace worn parts before further flight. Refit oil filter.\n\n2. Remove a quill pad cover P/N 204-040-174-001 or rotor brake quill from the transmission main ring gear case to allow access to the spiral bevel gear. Inspect all teeth of the gear for evidence of cracks, chipping and deformation. If cracks, chipping or metal deformation is evident replace gear before further flight. Refit component removed for access.\n\nNote: FAA Emergency AD 89-08-05 refers.\n\nCompliance: 1. Within 10 hours time in service or seven days whichever occurs first after 8 May 1989. Thereafter reinspect before the first flight of the day until gear has operated for 250 hours time in service.\n\n2. Within 10 hours time in service or seven days whichever occurs first after 8 May 1989. Thereafter reinspect at intervals not exceeding 50 hours time in service until gear has operated for 250 hours time in service.\n\nBackground: After a pilot reported an occasional unusual noise in flight, inspection of the main transmission revealed two large pieces of gear teeth that had fractured from the spiral bevel gear P/N 204-040-701-103. Metallurgical examination revealed the presence of a low alloy metallic inclusion which occurred during processing of the gear material. This inclusion may result in failure of the gear within the first 250 hours time in service.","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The AD's operational scope aligns with the defect described in the Background: it targets the specific bevel gear susceptible to a manufacturing inclusion and limits mandated inspections and replacements to the first 250 hours of service. It does not broaden affected parts, aircraft types, or the defect time-window beyond that described (Background; Applicability; Requirement; Compliance)."},"complexity_factors":["Narrow technical scope tied to a specific part number and a time window (<250 hours) increases operational specificity and record-keeping (Applicability).","Multiple inspection actions with different triggers and frequencies: immediate inspect within 10 hours/7 days, daily inspections for one item until 250 hours, and 50-hour intervals for the gear inspection (Compliance).","Mandated removal of access components (quill pad cover or rotor brake quill) to inspect gear teeth imposes maintenance time, required skills and operational downtime (Requirement).","Condition-based mandatory replacement \"before further flight\" if contamination, cracking, chipping or deformation is found creates potentially immediate parts and labour costs (Requirement).","Technical detection relies on visual/contamination inspection (filter particles, tooth condition) which may vary by inspector skill and raise ambiguity on borderline findings (Requirement; Background).","Cross-reference to FAA Emergency AD creates an international-regulatory coordination dimension but does not add discretionary remedies (Background/Note)."],"plain_english_summary":"**What it does:** This directive requires operators of Bell 212 helicopters with main transmission spiral bevel gear P/N 204-040-701-103 and under 250 hours total time-in-service to inspect the transmission sump oil filter and exposed gear teeth for metal contamination, cracks, chipping or deformation, and to replace any affected parts before further flight (Applicability; Requirement).  \n\n**Why it matters:** Inspections must begin within 10 hours or seven days and recur at short intervals until the gear reaches 250 hours, imposing inspection, removal-for-access and replacement costs and daily operational checks on operators (Compliance; Requirement; Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific manufacturing defect in a specific helicopter model. It has not expanded beyond its original purpose of ensuring the airworthiness of Bell 212 main transmission gears."},"complexity_factors":["Specific part number references (P/N 204-040-701-103, P/N 204-040-174-001) requiring technical familiarity","Dual compliance timelines (10 hours OR 7 days, whichever occurs first)","Different ongoing inspection intervals for two separate requirements (daily vs. 50-hour intervals)","Conditional logic: applicability limited to gears with less than 250 hours total time in service","Cross-reference to FAA Emergency AD 89-08-05 indicating international regulatory coordination","Technical terminology requiring aviation maintenance knowledge (quill pad cover, spiral bevel gear, time in service)"],"plain_english_summary":"This CASA airworthiness directive orders urgent inspections of the spiral bevel gear (P/N 204‑040‑701‑103) in the main transmission of Bell 212 helicopters after a detected metallic impurity that can cause gear teeth to crack and lead to catastrophic transmission failure. \n\nOperators of affected Bell 212s with the gear and less than 250 hours must check the transmission oil filter within 10 flight hours or 7 days and daily until 250 hours, visually inspect the gear within 10 hours/7 days and every 50 hours, and replace any contaminated or damaged parts before flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-212-40-main-transmission-spiral-bevel-gear","history":"/api/acts/ad-bell-212-40-main-transmission-spiral-bevel-gear/history","analysis":"/api/acts/ad-bell-212-40-main-transmission-spiral-bevel-gear/analysis","conflicts":"/api/acts/ad-bell-212-40-main-transmission-spiral-bevel-gear/conflicts","importantCases":"/api/acts/ad-bell-212-40-main-transmission-spiral-bevel-gear/important-cases","documents":"/api/acts/ad-bell-212-40-main-transmission-spiral-bevel-gear/documents"}}