{"id":"F2006B10983","name":"AD/JT8D/24 Amdt 1 - Seventh Stage Compressor Airseal","slug":"ad-jt8d-24-amdt-1-seventh-stage-compressor-airseal","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56569,"registerId":"commonwealth-F2006B10983-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT8D/24 Amdt 1 - Seventh Stage Compressor 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 \\- JT8D Series\n\nAD/JT8D/24\n\nAmdt 1\n\n  \nSeventh Stage Compressor Airseal 2/90\n\nApplicability: JT8D-1, \\-1A, \\-1B, \\-7, \\-7A, \\-7B,-9, \\-9A, \\-11, \\-15, \\-17, \\-17R engines not incorporating PWA SB No. 5738.\n\nRequirement: 1. Inspect the seventh stage airseal for evidence of corrosion and/or cracking.\n\n2. Action in accordance with PWA SB No. 5738.\n\nCompliance: 1. At next scheduled engine shop visit which requires disassembly of the engine at any flange other than the fan case or thrust reverser, and thereafter at intervals not to exceed 8,000 cycles.\n\n2. (a) For engines with an aircraft fleet annual utilisation of 500 cycles or greater, at next disassembly of the high compressor from the diffuser case.\n\n(b) For engines with an aircraft fleet annual utilisation of less than 500 cycles, at next engine shop visit, but no later than 31 December 1990.\n\nEffective: 22 February 1990.\n\nBackground: This Directive has been amended to alleviate the original calendar compliance requirement, and to reflect advice received from the manufacturer. The Directive now requires repetitive inspections of pre SB No. 5738 airseals until incorporation of SB No. 5738.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Amendment altered the original calendar-based compliance to require repetitive inspections until incorporation of PWA SB No. 5738, and updated timing to reflect manufacturer advice (Background)."},"complexity_factors":["Technical specificity: applies to a long list of JT8D sub-models (Applicability).","Conditional compliance tied to engine disassembly events (Compliance 1: 'next scheduled engine shop visit which requires disassembly at any flange other than the fan case or thrust reverser').","Repetitive inspection interval of 'not to exceed 8,000 cycles' creates ongoing monitoring obligations (Compliance 1).","Differentiated timing based on aircraft fleet annual utilisation threshold of 500 cycles (Compliance 2(a)–(b)).","Reference to external mandatory action: incorporation of PWA SB No. 5738 as the corrective measure (Requirement, Compliance 2).","Combination of event‑based, cycle‑based and calendar deadline (31 December 1990) compliance paths increases scheduling complexity (Compliance 2(b)).","Operational and cost impact concentrated on operators and maintenance providers who must plan shop visits and bear repair/installation costs (Requirement; Compliance)."],"plain_english_summary":"This Airworthiness Directive requires operators of specified Pratt & Whitney JT8D engine models that have not incorporated PWA Service Bulletin No. 5738 to inspect the seventh-stage compressor airseal for corrosion or cracking and to carry out corrective action per SB No. 5738. (Applicability; Requirement.) Inspections must occur at the next qualifying engine shop visit and then every 8,000 cycles; SB incorporation timing varies by fleet utilisation. Operators pay inspection/repair costs and must schedule disassembly to comply. (Compliance 1–2.)"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment narrows and refines the original directive rather than expanding it. The Background explicitly states it 'alleviates the original calendar compliance requirement' — converting a rigid date-based deadline to a more flexible cycle-based system. The core safety purpose (inspecting and upgrading the airseal) remains identical to the original 1990 directive."},"complexity_factors":["Short, single-purpose directive (approximately 200 words)","Only 4 defined applicability criteria (engine models and SB status)","Two-tier compliance structure with a utilisation-based exception (500 cycles/year threshold)","Single cross-reference to external manufacturer document (PWA SB No. 5738)","No nested definitions or recursive conditions","Clear, sequential numbering (1, 2, 2(a), 2(b)) without deep branching"],"plain_english_summary":"This AD mandates inspection of the seventh-stage compressor airseal on certain Pratt & Whitney JT8D engines (common on older 727/737/DC‑9/MD‑80 aircraft) for corrosion/cracking and repeat inspections every 8,000 flight cycles. Operators whose engines lack Service Bulletin 5738 must install the upgrade on a usage-based schedule: at the next appropriate shop visit, with earlier action for high‑cycle aircraft.\n\nThe amendment replaces a fixed calendar deadline with cycle-based compliance to maintain safety while giving operators scheduling flexibility."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt8d-24-amdt-1-seventh-stage-compressor-airseal","history":"/api/acts/ad-jt8d-24-amdt-1-seventh-stage-compressor-airseal/history","analysis":"/api/acts/ad-jt8d-24-amdt-1-seventh-stage-compressor-airseal/analysis","conflicts":"/api/acts/ad-jt8d-24-amdt-1-seventh-stage-compressor-airseal/conflicts","importantCases":"/api/acts/ad-jt8d-24-amdt-1-seventh-stage-compressor-airseal/important-cases","documents":"/api/acts/ad-jt8d-24-amdt-1-seventh-stage-compressor-airseal/documents"}}