{"id":"F2006B10979","name":"AD/JT8D/17 - Eighth Stage Rear Compressor Front Hub","slug":"ad-jt8d-17-eighth-stage-rear-compressor-front-hub","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56563,"registerId":"commonwealth-F2006B10979-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT8D/17 - Eighth Stage Rear Compressor Front Hub","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/17 Eighth Stage Rear Compressor Front Hub 9/80\n\nApplicability: All JT8D engines fitted with eighth stage rear compressor front hubs P/N 690908, 701308, 717608, 717708 and 738308 which contain balance cuts.\n\nDocument: 1. FAA Emergency Telegraphic AD TAD No. T80 15 51; or\n\n2. Pratt & Whitney Aircraft Alert SB ASB 5154 Rev. 1; or 3. AD/PW-T/53.\n\nCompliance: As detailed in Requirement Document No. 1.\n\nBackground: Overseas, a JT8D engine experienced an uncontained rupture of a rear compressor front hub, P/N 738308. Subsequent investigation concluded that a fracture originated in the transition radius of a machining cut on the balance flange. This Directive is issued in order to provide inspection procedures and compliance requirements needed to detect cracks in the affected areas of P/N 738308 and similar JT8D hubs.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive's scope matches the stated investigative finding: it targets eighth stage rear compressor front hubs of specified part numbers that contain balance cuts to detect cracks originating at the machining transition radius (Background; Applicability). The instrument requires inspections and corrective actions as detailed in the referenced requirement documents and does not expand beyond that stated remedial purpose (Document; Compliance)."},"complexity_factors":["Requires cross-referencing multiple external documents (FAA AD, Pratt & Whitney SB, or AD/PW-T/53) to determine exact inspection procedures (Document).","Applicability is limited to specific part numbers and only to those hubs that contain balance cuts, requiring accurate part verification on each engine (Applicability).","The AD defers technical detail (inspection method, intervals, corrective action) to a separate Requirement Document, which maintenance organisations must obtain and interpret (Compliance).","Potential logistical complexity from coordinating inspections, parts supply and aircraft downtime across operators and maintenance providers (implied by Compliance)."],"plain_english_summary":"This airworthiness directive mandates inspections and any required repairs for certain Pratt & Whitney JT8D eighth-stage compressor hubs that have machining balance cuts. It affects operators, owners and maintenance organisations that have those hubs installed.\n\nIssued after an overseas uncontained hub rupture, the AD aims to detect cracks at the balance-flange machining area to prevent failures; compliance costs, parts replacement and downtime fall to operators and their maintenance providers."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical failure mode in specific engine part numbers. It has not expanded beyond its original purpose of mandating inspections for cracked compressor hubs."},"complexity_factors":["Very short document (approximately 200 words)","Only 5 specific part numbers affected, clearly listed","Simple conditional trigger: 'which contain balance cuts'","Incorporates external documents by reference rather than reproducing technical procedures","No nested exceptions or complex conditional logic","Single compliance pathway with alternative reference documents","No defined terms section — uses standard aviation terminology"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order for aircraft engines. It applies to specific Pratt & Whitney JT8D jet engines used in planes like the Boeing 727 and early 737s.\n\n**What it does:**\n- Requires inspections of a particular engine part called the \"eighth stage rear compressor front hub\" — a critical component in the engine's compressor section\n- Targets specific part numbers (P/N 690908, 701308, 717608, 717708 and 738308) that have \"balance cuts\" (machining grooves used to balance the rotating component)\n\n**Why it matters:**\n- An engine overseas suffered an \"uncontained rupture\" — meaning the hub broke apart and pieces escaped the engine casing, which can damage the aircraft or injure people on the ground\n- The investigation found cracks starting in the curved transition areas of machining cuts on the balance flange\n- Without inspection, these cracks could lead to catastrophic engine failure\n\n**What must happen:**\n- Operators must follow the inspection procedures in the referenced FAA Emergency AD or Pratt & Whitney Alert Service Bulletin\n- Compliance is mandatory \"as detailed\" in those documents — meaning the actual inspection steps aren't repeated here but are incorporated by reference\n\n**Who it affects:**\n- Airlines and operators flying aircraft with JT8D engines (common in older commercial jets)\n- Maintenance organisations servicing these engines"}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt8d-17-eighth-stage-rear-compressor-front-hub","history":"/api/acts/ad-jt8d-17-eighth-stage-rear-compressor-front-hub/history","analysis":"/api/acts/ad-jt8d-17-eighth-stage-rear-compressor-front-hub/analysis","conflicts":"/api/acts/ad-jt8d-17-eighth-stage-rear-compressor-front-hub/conflicts","importantCases":"/api/acts/ad-jt8d-17-eighth-stage-rear-compressor-front-hub/important-cases","documents":"/api/acts/ad-jt8d-17-eighth-stage-rear-compressor-front-hub/documents"}}