{"id":"F2006B03586","name":"AD/BEA 121/21 - Nose Undercarriage and Rudder Control System","slug":"ad-bea-121-21-nose-undercarriage-and-rudder-control-system","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43159,"registerId":"commonwealth-F2006B03586-current","compilationNumber":null,"startDate":"2026-04-01","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BEA 121/21 - Nose Undercarriage and Rudder Control System","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Beagle B121 (Pup) Series Aeroplanes\n\n \n\nAD/BEA 121/21 Nose Undercarriage and Rudder Control System 11/78\n\nApplicability: All model B121.\n\n \n\nRequirement: Action in accordance with British Aerospace (Scottish Division) SB No. B121/77. Compliance:              Before further flight following report of severe nosewheel shimmy.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1871},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive remains tightly focused on its original purpose: addressing the specific safety defect of nosewheel shimmy in Beagle B121 aircraft. It references the manufacturer's 1977 service bulletin and imposes a straightforward flight prohibition until compliance, without expanding into broader operational or maintenance requirements."},"complexity_factors":["Very short text with single applicability (all Model B121)","Single trigger condition (report of severe nosewheel shimmy) with immediate compliance","Incorporates external technical standard by reference (British Aerospace SB B121/77) rather than reproducing detailed mechanical procedures","No defined terms section, exceptions, or conditional logic"],"plain_english_summary":"This CASA Airworthiness Directive applies to all Beagle B121 (Pup) aircraft and makes it mandatory that if severe nosewheel shimmy is reported, the owner must have the required maintenance done before the aircraft flies again. Compliance is achieved by following British Aerospace Service Bulletin B121/77. The rule prevents undercarriage or rudder damage and loss of steering during takeoff or landing."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bea-121-21-nose-undercarriage-and-rudder-control-system","history":"/api/acts/ad-bea-121-21-nose-undercarriage-and-rudder-control-system/history","analysis":"/api/acts/ad-bea-121-21-nose-undercarriage-and-rudder-control-system/analysis","conflicts":"/api/acts/ad-bea-121-21-nose-undercarriage-and-rudder-control-system/conflicts","importantCases":"/api/acts/ad-bea-121-21-nose-undercarriage-and-rudder-control-system/important-cases","documents":"/api/acts/ad-bea-121-21-nose-undercarriage-and-rudder-control-system/documents"}}