{"id":"F2006B09307","name":"AD/EC 120/11 - Tail Rotor Drive Shaft Damper","slug":"ad-ec-120-11-tail-rotor-drive-shaft-damper","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53409,"registerId":"commonwealth-F2006B09307-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.001.png)  \n\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 CASR 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.\n\n![](image.001.png)  \n\nEurocopter EC 120 Series Helicopters","sortOrder":0},{"sectionNumber":"AD/EC 120/11 Tail Rotor Drive Shaft Damp","sectionType":"part","heading":"AD/EC 120/11 Tail Rotor Drive Shaft Damper 2/2004","content":"# AD/EC 120/11 Tail Rotor Drive Shaft Damper 2/2004\n\nDM\n\nApplicability: EC 120B model helicopters all serial numbers up to and including 1362. Requirement: Inspect the tail rotor drive shaft damper for correct installation in accordance with\n\nEurocopter Alert Telex Number 65A004.\n\nNote: DGAC Airworthiness Directive U F-2003-465 refers\n\nCompliance: Unless previously accomplished:\n\n    Helicopters having less than 500 flying hours time in service since new; prior to exceeding 550 flying hours time in service since new.\n\n    2. Helicopters having more than 500 flying hours time in service since new; within 50 flying hours time in service from the effective date of this directive.\n\nThis Airworthiness Directive becomes effective on 14 January 2004.\n\nBackground: This directive has been issued in response to a report of a tail rotor drive shaft damper being found incorrectly assembled. The damper half clamps were found to be fouling and scoring the drive shaft. Continued operation of the helicopter in that condition may have resulted in the failure of the drive shaft.\n\n![Signature of David Villiers, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 7 January 2004\n\n![](image.001.png)","sortOrder":1}],"analysis":{"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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope. It addresses a specific manufacturing/assembly defect in a particular helicopter model series. There is no evidence of scope creep; the directive remains tightly focused on the tail rotor drive shaft damper installation issue as originally identified."},"complexity_factors":["Single, specific mechanical issue addressed","Only one model of aircraft affected (EC 120B)","Clear serial number cutoff (up to and including 1362)","Simple two-tier compliance schedule based on flight hours","Single inspection requirement referencing external technical document","No nested exceptions, conditional clauses, or defined terms section","Total length: approximately 250 words"],"plain_english_summary":"This safety order requires owners/operators of Eurocopter EC 120B helicopters (serial numbers 1362 and lower) to inspect the tail rotor drive shaft damper for correct installation per Eurocopter Alert Telex 65A004. CASA found clamps can rub the shaft if fitted wrong, leading to damage and possible in‑flight tail rotor drive failure.\n\nAction must be taken by the specified flight‑hour deadlines to prevent loss of tail-rotor control and potential crashes."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD’s scope remains limited to EC120B helicopters serials up to and including 1362 and mandates an inspection per Eurocopter Alert Telex 65A004 with specified flight‑hour compliance windows. The text shows no expansion or narrowing of that original applicability."},"complexity_factors":["Narrow applicability: only EC120B helicopters, serials up to 1362 (Applicability)","Single mandatory action: inspect damper for correct installation (Requirement)","Relies on an external technical document for how to inspect and correct: Eurocopter Alert Telex 65A004 (Requirement)","Compliance tied to aircraft-specific flight-hour thresholds with two timing bands, creating scheduling needs per helicopter (Compliance)","Potential follow-on maintenance costs if incorrect assembly is found (implied by Requirement and Background)","Issued by a CASA delegate under CASR subregulation 39.1(1), not a discretionary or case-by-case mandate (opening paragraph)"],"plain_english_summary":"This Airworthiness Directive requires operators of Eurocopter EC120B helicopters (serial numbers up to 1362) to inspect the tail-rotor drive-shaft damper for correct installation, following Eurocopter Alert Telex 65A004 (Applicability; Requirement). Operators must do the inspection within flight‑hour windows tied to each helicopter’s total time in service (Compliance). The AD responds to a reported incorrect assembly that scored the drive shaft and could cause failure (Background). Operators pay inspection and any corrective work; technical instructions come from the manufacturer’s telex."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ec-120-11-tail-rotor-drive-shaft-damper","history":"/api/acts/ad-ec-120-11-tail-rotor-drive-shaft-damper/history","analysis":"/api/acts/ad-ec-120-11-tail-rotor-drive-shaft-damper/analysis","conflicts":"/api/acts/ad-ec-120-11-tail-rotor-drive-shaft-damper/conflicts","importantCases":"/api/acts/ad-ec-120-11-tail-rotor-drive-shaft-damper/important-cases","documents":"/api/acts/ad-ec-120-11-tail-rotor-drive-shaft-damper/documents"}}