{"id":"F2006B07318","name":"AD/TB20/15 Amdt 2 - Landing Gear Articulated Stays","slug":"ad-tb20-15-amdt-2-landing-gear-articulated-stays","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49343,"registerId":"commonwealth-F2006B07318-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB20/15 Amdt 2 - Landing Gear Articulated Stays","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)  \nAerospatiale (Socata) TB20 (Trinidad) Series Aeroplanes\n\nAD/TB20/15\n\nAmdt 2\n\n  \nLanding Gear Articulated Stays 3/91\n\nApplicability: Model TB20 and TB21 series with serial numbers 275 through 1119, except S/N 1109.\n\nRequirement: Action in accordance with the technical requirements of DGAC AD 89-096 (A) R2.\n\nNote: Socata TB SB 40 and 45/2 refer.\n\nCompliance: Unless already accomplished - Prior to exceeding 100 hours time in service after 22 March 1990, and thereafter at intervals not exceeding 500 hours time in service, or 1 year whichever occurs first, until modified in accordance with SB 45/1 or 45/2.\n\nBackground: To prevent the landing gear from jamming.\n\nAmendment 1 referenced latest Requirement Documents. SB 45/1 listed kits 9165 and 9166 which if installed terminate Directive requirements.\n\nAmendment 2 is raised to introduce the Country of origin AD as the Requirement Document plus additional information contained in Rev 2 of SB 45.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Yes. Amendment 2 changed which external technical documents form the Requirement Document by adopting the country-of-origin (DGAC) AD as the Requirement Document and by adding information from Revision 2 of Socata SB 45. Amendment 1 had earlier updated the Requirement Documents and identified kits (9165 and 9166) listed in SB 45/1 that, if installed, terminate the Directive's recurring inspection requirements. Together these amendments alter the set of referenced technical instructions operators must follow and add a specified terminating modification pathway. (Amendment 1; Amendment 2)"},"complexity_factors":["Narrow applicability: specific models and a serial-number range with one serial-number exception (Applicability)","Delegation of technical detail to external documents (DGAC AD 89-096 (A) R2 and Socata SB 45 Rev 2 / SB 45/1 / SB 45/2) increases administrative steps for operators (Requirement; Amendment 2)","Multiple compliance timing rules (initial 100 hours after a fixed date, then recurring 500 hours or 1 year) create monitoring and record-keeping obligations (Compliance)","Existence of terminating modification kits (9165 and 9166) which, if installed, end recurring obligations introduces an economic decision for operators (Amendment 1)","Reference to foreign authority (DGAC) requires access to and interpretation of overseas airworthiness material (Requirement; Amendment 2)"],"plain_english_summary":"What this instrument does (mechanically)\n\n- It requires operators of certain Aerospatiale (Socata) TB20 and TB21 aeroplanes (serial numbers 275 through 1119, except S/N 1109) to carry out specific inspection/modification work on the landing gear articulated stays in accordance with the foreign airworthiness directive DGAC AD 89-096 (A) R2 and the Socata service bulletin revision 2 (SB 45 Rev 2). (Applicability; Requirement)\n- If the work required by the DGAC AD/SB is not already done, the rule requires an initial inspection before the aeroplane exceeds 100 hours time in service after 22 March 1990, and then recurring inspections at intervals not exceeding 500 hours time in service or 1 year, whichever comes first, until a terminating modification specified in SB 45/1 or SB 45/2 is installed. (Compliance)\n\nWho this affects and who pays\n\n- Owners and operators of the listed TB20 and TB21 aeroplanes must perform the inspections and/or modifications and bear the direct costs of labour, parts, and any downtime required to comply. (Applicability; Compliance)\n- If an operator installs the kits listed in SB 45/1 (kits 9165 and 9166), the recurring inspection requirement is terminated; purchasing and fitting those kits is an alternative cost that operators may choose to incur. (Amendment 1; Requirement)\n\nWhy the rule exists (official claim) and how that interacts with costs and incentives\n\n- The stated purpose is to prevent the landing gear from jamming. (Background)\n- The mechanical effect is to create a continuing inspection obligation until a specified modification is fitted. That structure creates a choice for operators: pay recurring inspection and maintenance costs, or pay once to install the terminating modification (kits) and stop the recurring inspections. (Compliance; Amendment 1)\n\nCompliance mechanics, discretion and implementation risks\n\n- The AD does not itself set detailed technical steps; it delegates the technical content to the DGAC AD and to Socata service bulletins (SB 45 Rev 2, SB 45/1, SB 45/2). That means operators must obtain and follow those external documents to meet the requirement. (Requirement; Amendment 2)\n- Compliance timing is prescriptive (initial 100-hour limit after 22 March 1990; thereafter 500 hours or 1 year). Operators must track hours and calendar time and retain records to demonstrate compliance. (Compliance)\n- The regulator enforces the AD; the text gives no additional domestic discretion or alternative compliance pathways beyond the terminating modifications listed in the referenced service bulletins. (Requirement; Compliance)\n\nTrade-offs, opportunity costs and potential operational effects\n\n- Recurrent inspections increase maintenance workload and aircraft downtime; installing the terminating kits shifts costs toward parts and installation but removes the ongoing inspection burden. (Compliance; Amendment 1)\n- The directive covers a defined set of serial numbers and excludes one serial number (1109), so its operational reach is narrowly targeted. Operators of affected aircraft must choose between repeated inspections or a one-off modification. (Applicability; Compliance)\n\nNotes on document history affecting scope\n\n- Amendment 1 clarified the Requirement Documents and identified kits (9165 and 9166) whose installation ends the inspection requirement. (Amendment 1)\n- Amendment 2 replaced the previous domestic technical reference by specifying the country-of-origin (DGAC) AD as the Requirement Document and adding information from Revision 2 of SB 45. This changes which external documents operators must follow to comply. (Amendment 2)\n\nRelevant source lines: Applicability; Requirement; Compliance; Background; Amendment 1; Amendment 2."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment remains tightly focused on its original purpose: preventing landing gear jamming in specific Socata aircraft. Amendment 2 merely updates reference documents and incorporates the latest service bulletin information without expanding the scope to additional aircraft types, components, or operational requirements."},"complexity_factors":["Short, single-purpose directive (approximately 200 words)","Only 4 defined elements: applicability (specific serial numbers), requirement (reference to external DGAC AD), compliance timeframe, and background","Single cross-reference to external French aviation authority document (DGAC AD 89-096)","Simple conditional logic: compliance required 'unless already accomplished' and terminates if specific modification kits installed","No nested exceptions or layered definitions","Technical but narrow scope—only affects one aircraft type and specific component"],"plain_english_summary":"This is a **safety directive** (called an \"Airworthiness Directive\" or AD) issued by Australia's Civil Aviation Safety Authority (CASA) that applies to specific **Socata TB20 and TB21 aircraft**—small single-engine planes popular in Australia for training and private flying.\n\n**What it does:**\n- Requires owners and operators of affected aircraft to **inspect and maintain the landing gear articulated stays** (the mechanical arms that help the wheels fold up and down)\n- Mandates compliance with a French aviation safety directive (DGAC AD 89-096) because these planes are French-made\n- Sets **strict deadlines**: inspections must happen before 100 flight hours after March 1990, then every 500 flight hours or annually (whichever comes first)\n\n**Who it affects:**\n- Owners and operators of TB20/TB21 aircraft with serial numbers 275–1119 (except serial number 1109)\n- Maintenance engineers servicing these aircraft\n\n**Why it matters:**\nThe directive exists to **prevent landing gear from jamming**—a potentially catastrophic failure that could cause a crash during landing. The \"articulated stays\" are critical components that allow the landing gear to move properly. Without proper inspection and maintenance, these parts could fail.\n\n**Key update in this version (Amendment 2):**\n- Updates the reference documents to use the latest French safety directive as the official requirement\n- Incorporates new information from Service Bulletin 45 (Revision 2)\n- Notes that installing certain modification kits (9165 or 9166) ends the need for ongoing inspections"}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb20-15-amdt-2-landing-gear-articulated-stays","history":"/api/acts/ad-tb20-15-amdt-2-landing-gear-articulated-stays/history","analysis":"/api/acts/ad-tb20-15-amdt-2-landing-gear-articulated-stays/analysis","conflicts":"/api/acts/ad-tb20-15-amdt-2-landing-gear-articulated-stays/conflicts","importantCases":"/api/acts/ad-tb20-15-amdt-2-landing-gear-articulated-stays/important-cases","documents":"/api/acts/ad-tb20-15-amdt-2-landing-gear-articulated-stays/documents"}}