{"id":"F2006B07524","name":"AD/UH-1/10 - Tail Rotor Gearbox Duplex Bearings","slug":"ad-uh-1-10-tail-rotor-gearbox-duplex-bearings","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50061,"registerId":"commonwealth-F2006B07524-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/UH-1/10 Tail Rotor Gearbox Duplex Bea","sectionType":"part","heading":"AD/UH-1/10 Tail Rotor Gearbox Duplex Bearings 8/2000","content":"# AD/UH-1/10 Tail Rotor Gearbox Duplex Bearings 8/2000\n\nApplicability: Model UH1A, UH1B, UH1E, UH1F, UH1H, UH1L, and TH1L.\n\nRequirement: Remove from service tail rotor gearbox duplex bearing sets P/N 204-040-424-001 with S/Nos 1 to 182, MB183 to MB382, MB442, MB486, MB513, MB518, MB519, MB524, MB530, MB531, MB544, MB545, MB548, MB549, MB551, MB553, MB554, MB561, MB659, MB743, MB744, MB760 to MB769, and MB927 to\n\nMB936 inclusive installed in tail rotor quill P/N 204-040-012-009.\n\nNote: FAA AD 90-10-05 refers.\n\nCompliance: Before further flight after the effective date of this directive.\n\nThis Airworthiness Directive becomes effective on 10 August 2000.\n\nBackground: This directive is issued to prevent failure of the tail rotor gearbox and subsequent loss of control.\n\n![Signature of David Alan Villiers Delegate of the Civil Aviation Safety Authority](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's scope aligns with its stated purpose: to remove specified duplex bearing sets to prevent tail rotor gearbox failure. There is no indication in the text that the scope extends beyond removing the listed parts installed in the specified quill (Requirement; Background)."},"complexity_factors":["Narrow model-specific applicability requiring fleet identification and tracking (Applicability)","Action targets particular part number and numerous serial numbers, increasing parts‑level inspection work (Requirement)","Immediate compliance deadline: 'before further flight' creates operational disruption and urgent logistics (Compliance)","Costs and replacement logistics fall on operators—direct maintenance and downtime expenses (Requirement/Compliance)","No staged inspection or conditional rectification option—binary remove-from-service directive (Requirement/Compliance)","Cross-reference to FAA AD 90-10-05 requires coordination with foreign airworthiness guidance (Requirement Note)"],"plain_english_summary":"This Airworthiness Directive orders operators of UH‑1A/B/E/F/H/L and TH1L helicopters to remove specific tail‑rotor gearbox duplex bearing sets (P/N 204‑040‑424‑001; listed serial numbers) installed in tail‑rotor quill P/N 204‑040‑012‑009 before the next flight. CASA’s delegate issued the requirement; affected operators pay for removal and any replacement and must take immediate action (Applicability; Requirement; Compliance). The stated aim is to prevent gearbox failure and loss of control (Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific unsafe condition in specific helicopter models with specific defective parts. There is no evidence of scope creep; it is a targeted safety intervention exactly as intended."},"complexity_factors":["Very short document (under 300 words)","Only 3 operative sections: Applicability, Requirement, and Compliance","Single, unambiguous action required (remove specific parts)","Clear part numbers and serial numbers listed explicitly","No nested conditions, exceptions, or cross-references to other legislation (only a note referencing related FAA directive)","Immediate compliance deadline with no alternative methods or phased implementation"],"plain_english_summary":"This AD orders immediate removal, before further flight, of specific tail-rotor gearbox bearing sets from listed Bell UH-1 (UH1A/B/E/F/H/L and TH1L) helicopters because certain part/serial-numbered bearings risk gearbox failure and loss of control. It affects owners/operators of those models and is a mandatory safety requirement under Australian aviation law, effective 10 August 2000."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-uh-1-10-tail-rotor-gearbox-duplex-bearings","history":"/api/acts/ad-uh-1-10-tail-rotor-gearbox-duplex-bearings/history","analysis":"/api/acts/ad-uh-1-10-tail-rotor-gearbox-duplex-bearings/analysis","conflicts":"/api/acts/ad-uh-1-10-tail-rotor-gearbox-duplex-bearings/conflicts","importantCases":"/api/acts/ad-uh-1-10-tail-rotor-gearbox-duplex-bearings/important-cases","documents":"/api/acts/ad-uh-1-10-tail-rotor-gearbox-duplex-bearings/documents"}}