{"id":"F2006B11011","name":"AD/JT9D/18 - Low Pressure Turbine Airseal","slug":"ad-jt9d-18-low-pressure-turbine-airseal","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56611,"registerId":"commonwealth-F2006B11011-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT9D/18 - Low Pressure Turbine Airseal","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nPratt and Whitney Turbine Engines \\- JT9D Series\n\nAD/JT9D/18 Low Pressure Turbine Airseal 3/89\n\nApplicability: JT9D-3A,-7,-7A,-7AH, \\-7H, \\-7F, \\-7J, \\-20 engines.\n\nRequirement: Action in accordance with FAA AD 88-24-05 amdt 39-6018, items (a)(1)(2), (b), (c).\n\nNote: Subject airseals modified in accordance with the requirements of PWA SB 4835 revision 4 are considered to be in compliance with the requirements of this Directive.\n\nCompliance: 1. Airseals conforming to FAA AD 88-24-05 amdt 39-6018 item (a)(1) \\- Within the next 500 cycles in service after 1 March 1989.\n\n    2. Airseals conforming to FAA AD 88-24-05 amdt 39-6018 item (a)(2) \\- At next disassembly of the low pressure turbine module.\n\n    3. FAA AD 88-24-05 amdt 39-6018 items (b), (c) \\- At next disassembly of the low pressure turbine module.\n\nBackground: This Directive has been issued to require modification and/or inspection of certain sixth stage low pressure turbine airseals. The Requirement follows advice that airseal rub could result in seal rupture and uncontained engine failure.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete airworthiness directive addressing a specific safety defect in specific engine models. It has not expanded beyond its original purpose of mandating inspection/modification of the low pressure turbine airseal."},"complexity_factors":["Single technical subject matter (one engine part on specific engine models)","Only 3 compliance deadlines with clear triggers (flight cycles or next disassembly)","Minimal cross-referencing (references one FAA directive and one manufacturer service bulletin)","No nested exceptions or conditional logic — straightforward applicability and requirements","Short document (approximately 200 words)","Only 2 defined terms effectively (the engine models listed, and the airseal itself)"],"plain_english_summary":"This safety order requires operators and maintenance organisations to inspect or modify the sixth-stage low-pressure turbine airseal on Pratt & Whitney JT9D engines to prevent rubbing, seal failure, and potential uncontained engine failures. It affects airlines using JT9D-powered wide-body aircraft and sets near-term compliance deadlines (including a 500-flight-cycle trigger); engines already modified per P&W Service Bulletin 4835 Rev. 4 are compliant."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive implements and adopts the FAA AD requirements for the specified JT9D models; it does not expand or narrow the class of affected engines beyond the stated applicability, and it expressly recognises PWA SB 4835 revision 4 as an acceptable means of compliance."},"complexity_factors":["Cross-reference to FAA AD 88-24-05 creates dependence on external document for full technical steps","Multiple compliance timelines (500 cycles vs. next disassembly) require operational scheduling","Applicability limited to a set of engine models—requires fleet-level tracking","Technical work requires LPT module disassembly and parts modification or inspection","Compliance note allowing PWA SB 4835 rev 4 as alternative adds an additional normative reference"],"plain_english_summary":"This Airworthiness Directive requires inspection and/or modification of the sixth-stage low-pressure turbine (LPT) airseals on specified Pratt & Whitney JT9D engine models, by adopting the actions in FAA AD 88-24-05. It applies to JT9D-3A, -7, -7A, -7AH, -7H, -7F, -7J and -20 engines.\n\nThe Directive aims to prevent airseal rub that could rupture seals and cause uncontained engine failure. Engine operators must schedule inspections or modifications within the stated time limits (next 500 cycles or at next LPT disassembly); operators pay the maintenance cost and decide timing within those bounds. Compliance can be achieved by installing parts per PWA SB 4835 rev 4."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt9d-18-low-pressure-turbine-airseal","history":"/api/acts/ad-jt9d-18-low-pressure-turbine-airseal/history","analysis":"/api/acts/ad-jt9d-18-low-pressure-turbine-airseal/analysis","conflicts":"/api/acts/ad-jt9d-18-low-pressure-turbine-airseal/conflicts","importantCases":"/api/acts/ad-jt9d-18-low-pressure-turbine-airseal/important-cases","documents":"/api/acts/ad-jt9d-18-low-pressure-turbine-airseal/documents"}}