{"id":"F2006B07315","name":"AD/TB20/12 Amdt 1 - Fuselage Frame 9","slug":"ad-tb20-12-amdt-1-fuselage-frame-9","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49336,"registerId":"commonwealth-F2006B07315-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB20/12 Amdt 1 - Fuselage Frame 9","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/TB20/12\n\nAmdt 1\n\n  \nFuselage Frame 9 6/88\n\nApplicability: TB20 and TB21 series aeroplanes with S/N 1 to 795 without modification No 70 embodied.\n\nRequirement: Action in accordance with Aerospatiale (Socata) Service Bulletin No 35/1.\n\nCompliance: (a) For aircraft with 1500 hours or more total time in service \\- inspect before further flight after 9 October 1987.\n\n    (b) For aircraft with less than 1475 hours total time in service \\- inspect within 25 hours time in service after 9 October 1987.\n\n    (c) Thereafter, reinspect at each issue of a new Maintenance Release.\n\nNote: Embodiment of Aerospatiale (Socata) modification No 70 constitutes terminating action for this Directive.\n\nBackground: Notification has been received from the manufacturer of in service cracking on overseas aircraft. This Directive has been amended to reflect the terminating action specified in the Requirement document.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is an amendment (Amdt 1) to an existing Airworthiness Directive, but the scope remains tightly focused on the original safety issue (Fuselage Frame 9 cracking). The amendment merely clarifies the terminating action (Modification No 70) without expanding the applicability or requirements beyond the original intent."},"complexity_factors":["Very short document (under 300 words)","Only 4 defined elements: specific aircraft models (TB20/TB21), serial number range (1-795), specific modification number (No 70), and specific service bulletin (35/1)","Simple conditional logic: two-tier compliance schedule based on flight hours (≥1500 vs <1475), plus ongoing periodic requirement","Single cross-reference to external technical document (Service Bulletin No 35/1) — standard for airworthiness directives","No nested exceptions or legislative cross-references","Clear terminating action specified"],"plain_english_summary":"This is a **safety inspection order** for specific small aircraft.\n\n**What it does:**\nOrders owners and operators of certain **Socata TB20 and TB21 Trinidad aeroplanes** (specifically those with serial numbers 1 to 795 that haven't had a particular factory modification) to inspect a critical part of the fuselage called **\"Frame 9\"** for cracks.\n\n**Who it affects:**\n- Owners and operators of TB20/TB21 aircraft with serial numbers 1–795\n- Only applies if the aircraft **hasn't** had \"Modification No 70\" installed\n- Maintenance engineers who issue Maintenance Releases (official documents that allow an aircraft to fly)\n\n**What must be done:**\n- **High-time aircraft** (1,500+ flight hours): Inspect **immediately** — before the next flight after 9 October 1987\n- **Lower-time aircraft** (under 1,475 flight hours): Inspect within **25 flight hours** after 9 October 1987\n- **Ongoing:** Re-inspect every time a new Maintenance Release is issued (typically annually or at major maintenance checks)\n\n**Why it matters:**\nThe manufacturer discovered **cracks developing in actual use** on aircraft overseas. Frame 9 is a structural part of the fuselage — cracks here could lead to structural failure. The inspection prevents potentially catastrophic accidents.\n\n**How to make it stop (terminating action):**\nInstalling factory **Modification No 70** permanently fixes the problem and ends the requirement for repeated inspections."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The directive was amended to reflect a terminating action specified in the Requirement document: embodiment of Aerospatiale (Socata) Modification No 70 constitutes terminating action for the Directive (Note). The amendment therefore changes the ongoing scope of the directive from indefinite recurring inspections to a regime that can be ended for an individual aircraft once the specified modification is embodied. The Background confirms the amendment was made to reflect that terminating action."},"complexity_factors":["Reference to an external technical document (Aerospatiale (Socata) Service Bulletin No 35/1) for the inspection procedure increases operational complexity because the directive does not itself describe the inspection steps (Requirement).","Different near-term compliance timings based on total time in service (>=1500 hours vs <1475 hours) require operators to check flight hours and schedule inspections accordingly (Compliance (a)–(b)).","Ongoing reinspection tied to each new Maintenance Release adds recurring compliance obligations and scheduling complexity (Compliance (c)).","A single specified terminating action (Modification No 70) changes the long-term compliance pathway, creating a binary choice for operators between repeated inspections and a one-off modification (Note).","Applicability is limited to a serial-number range and to aircraft that have not embodied a particular modification, so record-checking and maintenance-history verification are required (Applicability; Note)."],"plain_english_summary":"This airworthiness directive requires Aerospatiale (Socata) TB20/TB21 aeroplanes (S/N 1–795) that haven’t had Modification No 70 to undergo inspections of fuselage Frame 9 per the manufacturer’s Service Bulletin, prompted by in‑service cracking overseas. Operators must fund and schedule the inspections (and follow the bulletin’s remedial steps); embodying Modification No 70 is a one‑time terminating action that removes the recurring inspection obligation."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb20-12-amdt-1-fuselage-frame-9","history":"/api/acts/ad-tb20-12-amdt-1-fuselage-frame-9/history","analysis":"/api/acts/ad-tb20-12-amdt-1-fuselage-frame-9/analysis","conflicts":"/api/acts/ad-tb20-12-amdt-1-fuselage-frame-9/conflicts","importantCases":"/api/acts/ad-tb20-12-amdt-1-fuselage-frame-9/important-cases","documents":"/api/acts/ad-tb20-12-amdt-1-fuselage-frame-9/documents"}}