{"id":"F2006B10261","name":"AD/GBK 117/14 - Tail Rotor Drive Bearings","slug":"ad-gbk-117-14-tail-rotor-drive-bearings","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55932,"registerId":"commonwealth-F2006B10261-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 BK 117 Series Helicopters","sortOrder":0},{"sectionNumber":"AD/GBK 117/14 Tail Rotor Drive Bearings ","sectionType":"part","heading":"AD/GBK 117/14 Tail Rotor Drive Bearings 13/2003","content":"# AD/GBK 117/14 Tail Rotor Drive Bearings 13/2003\n\nApplicability: MBB-BK117 helicopters models A-1 though C-1 inclusive and incorporating any of the following:\n\n    A tail rotor transmission part number (P/N) 4639003001 or 4639003007 with a serial number (S/N) 900 through 932 inclusive; or\n\n    b. An intermediate gearbox P/N 4639002001 or 4639002005 with a S/N 902 though 928 inclusive; or\n\n    c. A tail rotor transmission P/N 4639003001 or 4639003007 that had been overhauled or repaired in the period 16 July 2001 to 14 April 2003, the effective date of Eurocopter Alert Service Bulletin (ASB) MBB-BK117-30-108 Revision 1; or\n\n    d. An intermediate gearboxes that had been overhauled or repaired in the period 16 July 2001 to 14 April 2003, the effective date of Eurocopter ASB MBB-BK117- 30-108 Revision 1; or\n\n    e. The tail rotor transmission and/or the intermediate gearbox is fitted with a bearing P/N 4639310006, S/N 3246 through 3598 inclusive; and\n\n    f. The tail rotor transmission and/or the intermediate gearbox has not been inspected in accordance with Paragraph 2.B.2 of Eurocopter ASB MBB-BK117- 30-108 Revision 1.\n\nRequirement: 1. Installed tail rotor transmission and intermediate gearboxes not incorporating an electrical chip detector in the tail rotor transmission or intermediate gearboxes:\n\n    Inspect the magnetic plug of the tail rotor transmission in accordance with Paragraph 2A of Eurocopter ASB MBB-BK117-30-108 Revision 1.\n\n    b. Inspect the magnetic plug of the intermediate gearbox in accordance with Paragraph 2A.”Accomplishment Instructions” of Eurocopter ASB MBB- BK117-30-108 Revision 1.","sortOrder":1}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD appears focused on its original safety purpose — addressing a specific bearing defect in BK 117 helicopters. The applicability criteria are detailed but remain targeted at the identified unsafe condition rather than expanding beyond it."},"complexity_factors":["Multiple nested applicability conditions using 'and/or' logic (6 separate criteria with mixed conjunctions)","Cross-reference to external technical document (Eurocopter ASB MBB-BK117-30-108 Revision 1) without reproducing the actual inspection steps","Date range dependencies (16 July 2001 to 14 April 2003) tied to external document effective dates","Part number and serial number ranges requiring precise matching (P/N 4639003001, S/N 900-932, etc.)","Exception clause in applicability (paragraph 2.B.2 of the ASB) creating a negative condition","Requirement section splits based on presence/absence of electrical chip detectors"],"plain_english_summary":"This AD requires owners/operators of certain Eurocopter MBB‑BK117 A‑1 through C‑1 helicopters with specified tail rotor transmissions or intermediate gearboxes to inspect the magnetic oil drain plugs for metal debris (per Eurocopter Alert Service Bulletin) when chip detectors are not fitted.\n\nIt tackles potentially failing tail rotor drive bearings that can cause loss of tail‑rotor control and catastrophic accidents, forcing checks to catch metal wear early and prevent failure."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive confines its remit to specified BK117 A‑1 to C‑1 helicopters and particular tail rotor transmission/intermediate gearbox part and serial number ranges, plus units overhauled/repaired in the stated period and those not previously inspected under Paragraph 2.B.2 of the Eurocopter ASB. The text does not expand scope beyond those criteria; it targets inspection of magnetic plugs per the named ASB to address the identified unsafe condition."},"complexity_factors":["Applicability tied to multiple specific part numbers and narrow serial number ranges (adds administrative tracking and verification).","Conditional applicability based on overhaul/repair dates (16 July 2001 to 14 April 2003) and prior inspection status (Paragraph 2.B.2), creating record-check burden.","Compliance requires following an external manufacturer document (Eurocopter ASB MBB‑BK117‑30‑108 Revision 1) rather than fully self-contained procedures in the AD.","Technical nature of inspection (magnetic plug/magnetic chip detection) requires maintenance competence and access to gearbox components.","Exemption condition “not incorporating an electrical chip detector” adds an equipment-status check before action is required.","Enforcement basis under CASR subregulation 39.1(1) means CASA delegate discretion in issuing the AD and operators must follow regulatory timetable and instructions."],"plain_english_summary":"This Airworthiness Directive requires operators of MBB‑BK117 A‑1 through C‑1 helicopters with specified tail rotor transmission or intermediate gearbox part/serial numbers, or units overhauled or repaired between 16 July 2001 and 14 April 2003, to inspect the magnetic plug (chip collection) of those gearboxes. The CASA delegate requires the inspection to be done in accordance with Eurocopter ASB MBB‑BK117‑30‑108 Revision 1; operators pay for and perform the inspections unless the parts were already inspected per Paragraph 2.B.2 of that ASB."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-gbk-117-14-tail-rotor-drive-bearings","history":"/api/acts/ad-gbk-117-14-tail-rotor-drive-bearings/history","analysis":"/api/acts/ad-gbk-117-14-tail-rotor-drive-bearings/analysis","conflicts":"/api/acts/ad-gbk-117-14-tail-rotor-drive-bearings/conflicts","importantCases":"/api/acts/ad-gbk-117-14-tail-rotor-drive-bearings/important-cases","documents":"/api/acts/ad-gbk-117-14-tail-rotor-drive-bearings/documents"}}