{"id":"F2006B10257","name":"AD/GBK 117/10 - Introduction of a Life Limit on Tail Rotor Drive Bevel Gear","slug":"ad-gbk-117-10-introduction-of-a-life-limit-on-tail-rotor-drive-bevel-gear","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55928,"registerId":"commonwealth-F2006B10257-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/GBK 117/10 - Introduction of a Life Limit on Tail Rotor Drive 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)  \nEurocopter BK 117 Series Helicopters\n\nAD/GBK 117/10 Introduction of a Life Limit on Tail Rotor Drive Bevel Gear\n\n  \n3/98\n\nApplicability: Eurocopter MBB-BK 117 helicopters Serial Number (S/N) 7001 \\- 7250 (incl) and 7500 - 7509 (incl).\n\nRequirement: Enter a life limitation of 18,500 hours against Bevel Gear 117-12215-01(tail rotor (output) drive unit of the main transmission) in the Accessory Replacement Record and Historical Record “Main Transmission”. To calculate the replacement time for the installed bevel gear, the total operating time for the component needs to be known. If this is not known, the total operating time for the component shall be considered to be the operating time of the main transmission.\n\nNote: LBA AD 97-350 dated 18 December 1997 refers.\n\nCompliance: Action must be performed by 31 March 1998.\n\nThis airworthiness directive becomes effective on 26 February 1998.\n\nBackground: The working life of the tail rotor (output) drive unit of the main transmission has been recalculated by the manufacturer. This has resulted in the introduction of a life limit on bevel gear part number 117-12215-01 of 18,500 hours.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The directive introduces a new mandatory life limit where none was recorded before for bevel gear 117-12215-01: 18,500 hours. It requires operators to enter that limit into the Accessory Replacement Record and the Historical Record “Main Transmission”, to calculate replacement time from the component’s known hours or, if unknown, use the main transmission’s operating time, and to comply by 31 March 1998 (effective 26 February 1998). Operators bear the replacement, record-keeping and scheduling costs arising from the change."},"complexity_factors":["Narrow applicability: specific helicopter model and serial-number ranges limit scope but require targeted compliance.","Single numeric life limit (18,500 hours) is simple to apply but requires accurate hours tracking.","Record-keeping requirement: must enter life limit into two specific maintenance records (Accessory Replacement Record; Historical Record “Main Transmission”).","Fallback rule for unknown component hours: operators must assume main transmission operating time, creating potential estimation issues.","Fixed, short compliance deadline (31 March 1998) imposes immediate administrative and operational action.","Replacement obligation creates direct costs and aircraft downtime for affected operators.","Authority and origin: change driven by manufacturer recalculation and mandated by the Civil Aviation Safety Authority, concentrating decision-making upstream."],"plain_english_summary":"This directive requires operators of Eurocopter MBB‑BK 117 helicopters (S/N 7001–7250 and 7500–7509) to record and enforce an 18,500‑hour life limit for tail‑rotor bevel gear part 117‑12215‑01, entering it in the Accessory Replacement Record and the Historical Record “Main Transmission”. If the gear’s hours are unknown, operators must use the main transmission’s operating time. The limit follows a manufacturer recalculation and must be complied with by 31 March 1998."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-limited safety directive for a specific aircraft part. It has not expanded beyond its original purpose of imposing a life limit on the tail rotor drive bevel gear for affected BK 117 helicopters."},"complexity_factors":["Single, specific mechanical component targeted (one part number)","Straightforward calculation method with one fallback provision","No cross-references to other legislation (only a non-binding note about a German authority document)","Minimal defined terms (only standard aviation abbreviations like S/N)","Single compliance action with fixed deadline","Narrow applicability (specific serial number ranges only)"],"plain_english_summary":"This mandatory CASA airworthiness directive imposes an 18,500‑hour life limit on the tail rotor drive bevel gear (P/N 117‑12215‑01) for specified Eurocopter BK 117 serials. Operators must record the limit in maintenance records and, if the gear’s own hours are unknown, assume it has the main transmission’s hours. It’s aimed at preventing in‑flight gear failure; compliance was due by 31 March 1998."}},"importantCases":[],"_links":{"self":"/api/acts/ad-gbk-117-10-introduction-of-a-life-limit-on-tail-rotor-drive-bevel-gear","history":"/api/acts/ad-gbk-117-10-introduction-of-a-life-limit-on-tail-rotor-drive-bevel-gear/history","analysis":"/api/acts/ad-gbk-117-10-introduction-of-a-life-limit-on-tail-rotor-drive-bevel-gear/analysis","conflicts":"/api/acts/ad-gbk-117-10-introduction-of-a-life-limit-on-tail-rotor-drive-bevel-gear/conflicts","importantCases":"/api/acts/ad-gbk-117-10-introduction-of-a-life-limit-on-tail-rotor-drive-bevel-gear/important-cases","documents":"/api/acts/ad-gbk-117-10-introduction-of-a-life-limit-on-tail-rotor-drive-bevel-gear/documents"}}