{"id":"F2006B07347","name":"AD/TB20/41 Amdt 2 - Aileron and Elevator Control Gimbal Joint","slug":"ad-tb20-41-amdt-2-aileron-and-elevator-control-gimbal-joint","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49436,"registerId":"commonwealth-F2006B07347-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB20/41 Amdt 2 - Aileron and Elevator Control Gimbal Joint","content":"![](image.001.png)\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/TB20/41 Amdt 1 and issues the following 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\nAerospatiale (Socata) TB20 (Trinidad) Series Aeroplanes\n\nAD/TB20/41\n\nAmdt 2\n\n  \nAileron and Elevator Control Gimbal Joint 4/2004\n\nApplicability: All Model TB20 and TB21 aircraft, without MOD 10-0209-27 or Service Bulletin No. BS 10-140 incorporated.\n\nRequirement: Inspect the aileron and elevator control gimbal joints in accordance with Socata Service Bulletin TB No. 10-130 Revision 2, dated January 2004.\n\nNote: DGAC AD F-2003-368 R2 refers.\n\nCompliance: 1. Within 300 flight hours or 12 months, whichever occurs first; following delivery of the aircraft or replacement of an aileron or elevator gimbal joint;\n\nor\n\nWithin 50 flight hours after 27 November 2003, whichever occurs later.\n\n2. Repeat thereafter at intervals not to exceed 110 flight hours or 14 months, whichever occurs first.\n\nThe compliance times remain unchanged by this issue. This Amendment becomes effective on 15 April 2004.\n\nBackground: Failure of an aileron control gimbal joint shear pin could result in disconnection of the joint and consequent loss of control. This Directive requires inspection of the shear and joint pins for security and the application of paint witness marks to the pins.\n\nAmendment 1 extended the inspection to elevator control gimbal joints and changed compliance times.\n\nAmendment 2 is issued in response to a revision of the related DGAC AD, which changes aircraft applicability to exclude aircraft that have the terminating modification for the requirements of this Directive incorporated.\n\nAerospatiale (Socata) TB20 (Trinidad) Series Aeroplanes\n\nAD/TB20/41 Amdt 2 (continued)\n\nThe original issue of this Airworthiness Directive became effective on 11 July 2002.\n\n![Signature of David Villiers Delegate of the Civil Aviation Safety Authority](image.002.png)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 5 March 2004\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 24 March 2004.","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 amendment maintains the original safety purpose of the AD. The only change is a narrowing of applicability to exclude aircraft that have received a terminating modification. This is a standard refinement rather than scope creep."},"complexity_factors":["Single, clearly defined applicability (two specific aircraft models, with explicit exclusions)","One primary requirement referencing an external technical document (Socata Service Bulletin TB No. 10-130 Rev 2)","Simple compliance structure with two alternative initial deadlines and one recurring interval","Minimal defined terms (only standard aviation terminology like 'flight hours' and 'MOD')","No nested exceptions or conditional logic beyond the applicability exclusion","Short document length (approximately 300 words of substantive text)"],"plain_english_summary":"This CASA safety order targets Socata TB20/TB21 Trinidad-series aeroplanes that lack a specific factory modification, requiring owners/operators to inspect aileron and elevator gimbal joints for secure shear pins and joint pins and to apply paint witness marks to detect movement. \n\nIt aims to prevent loss of control from shear-pin failure. Amendment 2 narrows applicability by excluding aircraft already fitted with the permanent factory fix (MOD 10-0209-27 / SB BS 10-140)."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The current amendment (Amdt 2) changed the AD's scope relative to the original issue in two material ways over time. The original AD (2002) focussed on aileron gimbal joints; Amendment 1 expanded the scope to include elevator gimbal joints and altered compliance times (so the set of required inspections increased). Amendment 2 then narrowed applicability by excluding aircraft that have incorporated the terminating modification (MOD 10-0209-27 or Service Bulletin No. BS 10-140). Mechanically, that means the net scope evolved from a single-component inspection requirement to a broader inspection mandate (ailerons and elevators) and was later constrained to apply only to aircraft that have not adopted the terminating modification. Amendment 2 therefore changes which aircraft must continue recurring inspections (it reduces the population of affected aircraft) and creates a clear pathway (incorporate the mod/SB) to avoid the recurring inspection burden."},"complexity_factors":["Short, single-issue directive (inspection requirement) with limited parts of the fleet affected","One external document referenced for procedures: Socata Service Bulletin TB No. 10-130 Revision 2","Conditional compliance timing with OR logic (either 300 flight hours/12 months or 50 flight hours after a date)","A repeating compliance interval (110 flight hours or 14 months) adds a recurring obligation","Applicability exclusion based on incorporation of MOD 10-0209-27 or Service Bulletin No. BS 10-140 (cross-reference to terminating modification)","Reference to prior amendments (Amendment 1) and a related foreign AD (DGAC) but no extensive nested exceptions"],"plain_english_summary":"**What this directive does (mechanically)\n\n- Revokes the earlier version of Airworthiness Directive AD/TB20/41 and issues a replacement AD that requires inspection of the aileron and elevator control gimbal joints on certain Aerospatiale (Socata) TB20 and TB21 aircraft.\n- The inspections must be carried out in accordance with Socata Service Bulletin TB No. 10-130 Revision 2 (January 2004). The work required is to check the shear and joint pins for security and to apply paint \"witness\" marks to the pins (so movement or loss is visible).\n- Owners/operators of aircraft that already have MOD 10-0209-27 or Service Bulletin No. BS 10-140 incorporated are excluded from this AD (they are treated as having the terminating modification).\n\nWho is affected\n\n- Owners and operators of Aerospatiale (Socata) TB20 (Trinidad) and TB21 aeroplanes that have not incorporated MOD 10-0209-27 or Service Bulletin No. BS 10-140. \n- Maintenance organisations and engineers who perform inspections and any subsequent rectification work.\n\nKey compliance timing (what must be done and when)\n\n- Initial inspection: within 300 flight hours or 12 months (whichever is first) after delivery of the aircraft or after replacement of an aileron or elevator gimbal joint; or, if applicable, within 50 flight hours after 27 November 2003 (whichever is later).\n- Repeat inspection: thereafter at intervals not exceeding 110 flight hours or 14 months (whichever is first).\n- Inspections must follow the procedures in the referenced Socata Service Bulletin.\n\nWhy it matters (safety reason and mechanical consequence)\n\n- The action responds to a safety concern: failure of an aileron control gimbal joint shear pin can allow the joint to disconnect and could cause loss of control of the aircraft. The inspections and witness-marking are intended to detect looseness, wear or impending pin failure before disconnection occurs.\n\nWho pays, who decides, and how behaviour is likely to change\n\n- Who pays: aircraft owners/operators pay for the inspections, any replacement parts and labour, and for aircraft downtime while inspections/repairs are done.\n- Who decides: the Civil Aviation Safety Authority (CASA) delegate issued the AD under CASR 1998 subregulation 39.1(1); operators must comply with the AD unless they have the terminating modification incorporated.\n- Behaviour changes: affected operators will schedule recurring inspections or choose to incorporate the terminating modification / service bulletin to remove the recurring inspection obligation.\n\nImplementation, costs and incentives\n\n- Implementation is primarily a maintenance and record-keeping task: inspections per the Socata service bulletin and application of paint witness marks.\n- Cost drivers: inspection labour, potential replacement of pins or gimbal joints found defective, and aircraft out-of-service time.\n- Incentive created: because aircraft that have the terminating modification (MOD 10-0209-27 or SB BS 10-140) are excluded, there is a clear economic incentive for operators to incorporate that modification to avoid repeated inspections (one-time cost versus recurring inspection costs).\n\nNotes on provenance and related material\n\n- The AD cites and follows a related DGAC (French authority) AD revision; it aligns applicability with that revised DGAC AD. Amendment 1 previously expanded the AD to include elevator gimbal joints and altered compliance times; Amendment 2 narrows applicability by excluding aircraft with the terminating modification.\n\n(References: requirement and compliance sections of AD/TB20/41 Amdt 2 and Socata Service Bulletin TB No. 10-130 Revision 2.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb20-41-amdt-2-aileron-and-elevator-control-gimbal-joint","history":"/api/acts/ad-tb20-41-amdt-2-aileron-and-elevator-control-gimbal-joint/history","analysis":"/api/acts/ad-tb20-41-amdt-2-aileron-and-elevator-control-gimbal-joint/analysis","conflicts":"/api/acts/ad-tb20-41-amdt-2-aileron-and-elevator-control-gimbal-joint/conflicts","importantCases":"/api/acts/ad-tb20-41-amdt-2-aileron-and-elevator-control-gimbal-joint/important-cases","documents":"/api/acts/ad-tb20-41-amdt-2-aileron-and-elevator-control-gimbal-joint/documents"}}