{"id":"F2006B06463","name":"AD/R44/13 - Rotor Drive Yoke","slug":"ad-r44-13-rotor-drive-yoke","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47942,"registerId":"commonwealth-F2006B06463-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/R44/13 - Rotor Drive Yoke","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)  \nRobinson R44 Series Helicopters\n\nAD/R44/13 Rotor Drive Yoke 10/99 DM\n\nApplicability: All Model R44 helicopters.\n\nRequirement: 1. Determine, by inspection, if the yoke assembly, part number (P/N) C908-1C, from Lot No. 36B, 37, or 38 is installed.\n\nNote 1: Yoke assemblies, P/N C908-1C, from Lot Nos. 36B, 37, and 38 were installed as original equipment in R44 helicopters, Serial Numbers 0219 and 0535 through 0608 (except numbers 0565, 0582, and 0592).\n\n2. Replace any yoke assembly, P/N C908-1C, from Lot No. 36B, 37, or 38, with a serviceable yoke assembly from a lot other than 36B, 37, or 38 in accordance with the compliance procedure, steps 2 through 12, of Robinson Helicopter Company R44 Service Bulletin SB-35, dated July 26, 1999.\n\nNote 2: Priority Letter FAA AD 99-17-17 refers.\n\nCompliance: Before further flight after 25 August 1999, unless already accomplished.\n\nThis Airworthiness Directive becomes effective on 25 August 1999.\n\nBackground: The FAA received a report of an incident in which, during cruise flight, the pilot heard a loud bang and noticed no tail rotor effectiveness after entering autorotation. An investigation revealed that the yoke assembly P/N C908-1C, which connects the main rotor gearbox pinion shaft to the forward flexplate, had failed at a weld joint due to a crack. The cause of the crack is unknown, but still under investigation.\n\nRobinson Helicopter Company has identified the manufacturing lots associated with the failed yoke. Failure of the yoke assembly could result in loss of main and tail rotor drive and subsequent loss of control of the helicopter.","sortOrder":0}],"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 is a targeted safety directive addressing a specific mechanical defect in a specific aircraft model. The scope remains precisely limited to the identified faulty yoke assemblies from three manufacturing lots. There is no evidence of scope creep; the AD does exactly what it says on the tin — inspect and replace if necessary."},"complexity_factors":["Very short document (under 300 words)","Only 1 defined term (P/N for part number)","Single, clear applicability criterion (all Model R44 helicopters)","Straightforward two-step requirement: inspect, then replace if needed","No cross-references to other legislation or complex conditional logic","Single compliance deadline with one simple exception (already accomplished)","Background provided in plain narrative form rather than technical legalese"],"plain_english_summary":"This CASA Airworthiness Directive legally requires all Robinson R44 owners/operators to inspect for and replace any rotor drive yoke P/N C908-1C from manufacturing lots 36B, 37, or 38, using Robinson SB-35.  \n\nAction must be completed before next flight after 25 August 1999. It prevents catastrophic in‑flight yoke failure (an event that already caused loss of rotor power and an emergency autorotation)."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive keeps a narrowly targeted scope: identify and replace yoke assemblies from specified lots on R44 helicopters. It does not expand regulatory subject matter beyond inspection and mandatory replacement of the identified defective parts, nor does it alter affected aircraft classes or introduce new obligations beyond following the cited service bulletin (Applicability; Requirement 1–2)."},"complexity_factors":["Narrow technical scope: applies only to R44 helicopters and a single part number and specific manufacturing lots (Applicability; Requirement 1).","Immediate mandatory compliance: replacement required before further flight after a fixed date, creating operational urgency (Compliance).","External cross-reference: compliance requires following Robinson Helicopter Company R44 Service Bulletin SB-35, steps 2–12, adding dependence on manufacturer instructions (Requirement 2).","Identification burden: operators must inspect serial numbers and lot markings to determine applicability (Requirement 1; Note 1).","Supply/logistics risk: replacement depends on availability of serviceable yokes from other lots, which may impose cost and downtime (Requirement 2).","Safety-critical consequence: failure mode (weld crack) risks loss of rotor drive, which raises enforcement priority but does not add legal complexity (Background).","Limited investigatory clarity: root cause remains unknown, so future directives or corrective actions may follow (Background)."],"plain_english_summary":"This Airworthiness Directive requires operators of Robinson R44 helicopters to inspect for, and if present replace before next flight, a specific rotor drive yoke assembly (P/N C908-1C) manufactured in Lot Nos. 36B, 37 or 38 (Requirement 1–2; Compliance). The measure targets parts traced to a weld crack that can cause loss of main and tail rotor drive; aircraft owners/operators pay for inspection and replacement and must follow Robinson Service Bulletin SB-35 as the compliance method (Requirement 2; Note 2)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-r44-13-rotor-drive-yoke","history":"/api/acts/ad-r44-13-rotor-drive-yoke/history","analysis":"/api/acts/ad-r44-13-rotor-drive-yoke/analysis","conflicts":"/api/acts/ad-r44-13-rotor-drive-yoke/conflicts","importantCases":"/api/acts/ad-r44-13-rotor-drive-yoke/important-cases","documents":"/api/acts/ad-r44-13-rotor-drive-yoke/documents"}}