{"id":"F2006B07331","name":"AD/TB20/27 Amdt 2 - Exhaust System Clap Locknuts","slug":"ad-tb20-27-amdt-2-exhaust-system-clap-locknuts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49378,"registerId":"commonwealth-F2006B07331-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB20/27 Amdt 2 - Exhaust System Clap Locknuts","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/TB20/27\n\nAmdt 2\n\n  \nExhaust System Clap Locknuts 5/97\n\nApplicability: All TB20 aircraft not incorporating HSJ Aviation (HSJ) Engineering Order HSJ 1330 or HSJ Drawing 5202, and HSJ Engineering Order HSJ 1486.\n\nRequirement: To prevent failure of the exhaust system; inspect, modify and assemble the exhaust system in accordance with the requirements of Socata Service Bulletin No.\n\nSB 10-072-78 Amendment 2.\n\nNote: DGAC Airworthiness Directive 92-152(A)R4 refers.\n\nCompliance: Unless previously accomplished in accordance with Amendment 1 of this Directive; within 50 hours time in service after 24 April 1997, and thereafter at each disassembly of the exhaust system.\n\nThis Amendment becomes effective on 24 April 1997.\n\nBackground: This Directive was originally issued to address concern for the integrity of the TB20 exhaust system following two TB10 in-flight exhaust system separation events in Australia. Amendment 1 of the Directive reflected the manufacturer's revision to the part numbers of the replacement exhaust pipe and the long manifold to exhaust pipe clamps. This amendment reflects the manufacturer’s second revision of the requirement document. The revision, in part, introduces a new exhaust pipe to engine cylinder seal part number and revises the exhaust assembly torque data.\n\nAmendment 1 of this Airworthiness Directive became effective on 28 March 1996. The original issue of this Airworthiness Directive became effective on 26 May 1994.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original directive (1994) addressed exhaust system integrity following in-flight failures. Amendment 1 (1996) expanded scope to cover revised part numbers for replacement components. Amendment 2 (1997) further expanded scope to include a new seal part number and revised torque data. While still focused on exhaust system safety, the technical requirements have evolved through three iterations, incorporating progressively more detailed engineering specifications from the manufacturer."},"complexity_factors":["Short, single-purpose directive (approximately 250 words)","Only 4 defined/modified terms (applicability criteria, compliance timeline, reference documents)","Single cross-reference to French aviation authority (DGAC) directive and manufacturer service bulletin","Simple conditional logic: 'unless previously accomplished' creates one exception","No nested exceptions or sub-delegations","Clear, sequential structure: applicability → requirement → compliance → background"],"plain_english_summary":"Owners/operators of Socata TB20 Trinidad aircraft must inspect and modify the exhaust clamp locknuts (per Socata Service Bulletin SB 10-072-78 Amendment 2) unless already modified under specified HSJ documents. The work — including a new seal and updated torque settings — must be done within 50 flight hours of 24 April 1997 and thereafter whenever the exhaust is reassembled.\n\nThis mandatory AD prevents in‑flight exhaust separation that previously occurred on similar TB aircraft."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Amendment 2 did not expand which aircraft are covered but changed the technical requirements: it introduces a new exhaust-pipe-to-engine-cylinder seal part number and revises exhaust-assembly torque data (Background; Requirement). Applicability remains limited to TB20s not modified by the listed HSJ engineering orders (Applicability), and the compliance timing (50 hours after 24 April 1997 and thereafter at each disassembly) is retained (Compliance)."},"complexity_factors":["Targeted applicability with carve-outs: applies to all TB20 aircraft except those incorporating HSJ Engineering Order HSJ 1330 or HSJ Drawing 5202 and HSJ Engineering Order HSJ 1486 (Applicability).","Dependence on external technical document: mandates work in accordance with Socata Service Bulletin SB 10-072-78 Amendment 2 (Requirement), requiring operators to obtain and follow the SB.","Technical assembly specifications: Amendment introduces a new exhaust-pipe-to-cylinder seal part number and revised exhaust-assembly torque data, requiring workshop capability and correct tooling.","Time-limited and event-based compliance: initial action due within 50 hours TIS after 24 April 1997 and recurring requirement at each disassembly of the exhaust system (Compliance).","Amendment history and cross-reference risk: multiple amendments and a referenced DGAC AD increase traceability and record-checking burden.","Relatively narrow operational impact: affects a single aircraft type and a defined component, reducing regulatory breadth but concentrating technical compliance requirements."],"plain_english_summary":"This directive requires owners/operators of Aerospatiale (Socata) TB20 aeroplanes (unless already modified by specified HSJ engineering orders) to inspect, modify and reassemble the exhaust system following the manufacturer’s Service Bulletin SB 10-072-78 Amendment 2 to prevent exhaust separation. Compliance must be done within 50 hours time-in-service after 24 April 1997 (unless Amendment 1 already applied) and at every subsequent exhaust-system disassembly."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb20-27-amdt-2-exhaust-system-clap-locknuts","history":"/api/acts/ad-tb20-27-amdt-2-exhaust-system-clap-locknuts/history","analysis":"/api/acts/ad-tb20-27-amdt-2-exhaust-system-clap-locknuts/analysis","conflicts":"/api/acts/ad-tb20-27-amdt-2-exhaust-system-clap-locknuts/conflicts","importantCases":"/api/acts/ad-tb20-27-amdt-2-exhaust-system-clap-locknuts/important-cases","documents":"/api/acts/ad-tb20-27-amdt-2-exhaust-system-clap-locknuts/documents"}}