{"id":"F2005L03581","name":"AD/BEA 121/8 Amdt 4 - Rudder Control Torque Tubes","slug":"ad-bea-121-8-amdt-4-rudder-control-torque-tubes","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":39171,"registerId":"commonwealth-F2005L03581-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Beagle B121 (Pup) Series Aeroplanes","sectionType":"division","heading":"Beagle B121 (Pup) Series Aeroplanes","content":"### Beagle B121 (Pup) Series Aeroplanes\n\n| AD/BEA 121/8 Amdt 4 | Rudder Control Torque Tubes | 13/2005 |\n| ------------------- | --------------------------- | ------- |\n\n| Applicability: | All Model Beagle B.121 series aircraft.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Inspect the rudder torque tube assemblies in accordance with de Havilland Support Ltd Service Bulletin B121/65 Issue 2, or later CAA approved revision.Cracked rudder torque tube assemblies must be replaced before further flight.Note: UK CAA AD G-2005-0030 refers.                                                                                                                                                                                                                                                                                                    |\n| Compliance:    | Within 100 hours time in service since the last inspection performed in accordance with the previous issue of this Directive. Inspect thereafter at intervals not to exceed 100 hours time in service.                                                                                                                                                                                                                                                                                                                                                                     |\n|                | This Amendment becomes effective on 22 December 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |\n| Background:    | The Type Certificate Holder has received several reports of failed rudder torque tube assemblies. The recent failures occurred in service after inspections performed in accordance with the previous issue of the Requirement document. In the event of such failures, loss of directional control through both the rudder and nosewheel steering may occur. Reports were also received of loose rivets attaching the inboard anchor assembly to the starboard torque tube. This Directive mandates revised detailed repetitive inspection of the torque tube assemblies. |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n11 November 2005","sortOrder":0},{"sectionNumber":"AD/BEA 121/8 Amdt 4","sectionType":"part","heading":"AD/BEA 121/8 Amdt 4","content":"## AD/BEA 121/8 Amdt 4","sortOrder":1},{"sectionNumber":"Rudder Control Torque Tubes","sectionType":"part","heading":"Rudder Control Torque Tubes","content":"## Rudder Control Torque Tubes","sortOrder":2},{"sectionNumber":"13/2005","sectionType":"part","heading":"13/2005","content":"## 13/2005","sortOrder":3}],"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 amendment remains tightly focused on its original purpose: preventing rudder torque tube failures in Beagle B.121 aircraft. The amendment simply updates inspection requirements based on new failure data, without expanding to other aircraft types, components, or operational areas."},"complexity_factors":["Single, specific mechanical component targeted (rudder torque tube assemblies)","Only one technical reference document required (Service Bulletin B121/65 Issue 2)","Simple compliance timeline: 100 hours since last inspection, then every 100 hours","Binary pass/fail outcome: cracked = replace, not cracked = continue with periodic inspections","No nested exceptions, conditional clauses, or alternative compliance methods","Minimal defined terms (only standard aviation terms like 'time in service')","Short document length (approximately 200 words of substantive content)"],"plain_english_summary":"CASA requires owners/operators of Beagle B.121 (Pup) aircraft to inspect the rudder control torque tube assembly per de Havilland Support Ltd Service Bulletin B121/65 Issue 2 because several tubes have cracked and failed in flight, causing loss of rudder and nosewheel steering.  \n\nInspections are mandated every 100 flight hours and any cracked tube must be replaced before further flight — tightening prior inspection requirements to prevent catastrophic directional-control failures."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The amendment revises and tightens inspection requirements for rudder torque tube assemblies: it mandates detailed repetitive inspections using the specified service bulletin, sets a 100‑hour reinspection interval and transitional requirement to inspect within 100 hours if inspected under the previous issue, and requires replacement of cracked assemblies before further flight (see Requirement, Compliance, Background)."},"complexity_factors":["Narrow applicability to a single aircraft type reduces regulatory breadth (Applicability).","Mandatory repetitive inspections at fixed 100‑hour intervals create an ongoing maintenance schedule (Compliance).","Requirement to replace cracked assemblies before further flight imposes immediate parts/replacement costs and operational downtime (Requirement).","Technical inspection procedure is delegated to an external Service Bulletin, including later CAA‑approved revisions, introducing reliance on an external document and regulator discretion (Requirement).","Background reports that failures occurred despite prior inspections suggest heightened inspection detail or technique in the new mandate (Background).","Cross‑reference to UK CAA AD introduces potential for international coordination and differing approval processes (Requirement/Note).","Timing clause requiring inspection within 100 hours since the last inspection performed under the previous issue raises transitional compliance tracking needs (Compliance)."],"plain_english_summary":"Mandates repetitive inspections of rudder torque tube assemblies on all Beagle B.121 aircraft, using de Havilland Support Ltd Service Bulletin B121/65 Issue 2 (or a later CAA‑approved revision). Cracked assemblies must be replaced before further flight; inspections must occur within 100 hours since the last inspection under the previous issue and then every 100 hours. It responds to in‑service torque tube failures and reports of loose rivets. Aircraft operators pay for inspections and any replacements; compliance depends on following the referenced service bulletin and CAA approvals."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bea-121-8-amdt-4-rudder-control-torque-tubes","history":"/api/acts/ad-bea-121-8-amdt-4-rudder-control-torque-tubes/history","analysis":"/api/acts/ad-bea-121-8-amdt-4-rudder-control-torque-tubes/analysis","conflicts":"/api/acts/ad-bea-121-8-amdt-4-rudder-control-torque-tubes/conflicts","importantCases":"/api/acts/ad-bea-121-8-amdt-4-rudder-control-torque-tubes/important-cases","documents":"/api/acts/ad-bea-121-8-amdt-4-rudder-control-torque-tubes/documents"}}