{"id":"F2006B11038","name":"AD/JT9D/9 - Fifth Stage Turbine Hubs - Reduction of Cyclic Life","slug":"ad-jt9d-9-fifth-stage-turbine-hubs-reduction-of-cyclic-life","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56651,"registerId":"commonwealth-F2006B11038-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT9D/9 - Fifth Stage Turbine Hubs - Reduction of Cyclic Life","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Pratt and Whitney Turbine Engines - JT9D Series\n\n \n\nAD/JT9D/9 Fifth Stage Turbine Hubs - Reduction of Cyclic Life 4/77\n\nApplicability: JT9D-3A, -7, -7A, -7H, -7AH, -7F and -30 engines containing fifth stage turbine hubs P/N 704705, 714905, 718905, 719205 and 726805.\n\n \n\nDocument: 1. FAA AD 77-01-07 : Amendment 39-2807; or\n\n \n\n2. AD/PW-T/41.\n\n \n\nCompliance: As per the Requirement Document.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD, as presented, limits its scope to the listed JT9D engine models fitted with the specified fifth-stage turbine hub part numbers and requires compliance with the referenced Requirement Document(s). The instrument does not, in this text, expand the affected population beyond those engines and part numbers, nor does it itself specify the new life limits; it delegates those technical changes to the referenced documents (see “Applicability”, “Document”, “Compliance”)."},"complexity_factors":["Directive text is short and delegates technical specifics to external Requirement Documents (FAA AD 77-01-07 or AD/PW-T/41), requiring users to consult additional materials.","Applicability covers multiple engine models and a list of specific part numbers, requiring cross-checking maintenance records to determine which units are affected.","Technical subject matter (turbine hub cyclic life) is engineering-heavy even though the AD itself is procedurally simple.","Compliance depends on obtaining and correctly implementing an external document, introducing administrative steps and potential for misinterpretation."],"plain_english_summary":"What this instrument does, mechanically\n\n- The Airworthiness Directive (AD/JT9D/9) reduces the allowable cyclic life for certain fifth-stage turbine hubs used in Pratt & Whitney JT9D series engines. The directive itself does not set the new cycle limits in this text; it requires compliance with an external Requirement Document (one of two referenced documents) that contains the specific actions and life limits. (See “AD/JT9D/9 Fifth Stage Turbine Hubs - Reduction of Cyclic Life”; “Document”; “Compliance”.)\n\nWho it affects\n\n- Aircraft operators, engine owners, maintenance organisations and parts suppliers that operate or service JT9D-3A, -7, -7A, -7H, -7AH, -7F and -30 engines fitted with fifth-stage turbine hubs having part numbers 704705, 714905, 718905, 719205 or 726805. (See “Applicability”.)\n\nWhat those people must do\n\n- They must follow the Requirement Document specified by the AD. The AD points to either FAA AD 77-01-07 (Amendment 39-2807) or AD/PW-T/41 as the authoritative compliance instructions. The AD here makes compliance mandatory “as per the Requirement Document.” (See “Document”; “Compliance”.)\n\nWhy it matters (stated purpose and practical effects)\n\n- The stated mechanical change is a reduction in the permitted cyclic life of the listed turbine hubs. That change intends to reduce the amount of time or number of cycles each hub may remain in service before mandatory action (inspection, overhaul or replacement) specified in the Requirement Document. The concrete effects are: earlier or more frequent maintenance actions for affected hubs; increased demand for replacement parts and maintenance labour; and potential aircraft downtime while hubs are serviced or replaced. (See “AD/JT9D/9”; “Document”; “Compliance”.)\n\nCosts, incentives and trade-offs (mechanisms, not value judgements)\n\n- Who pays: Operators and engine owners will pay for the additional inspections, overhauls or earlier replacements required by the Requirement Document. Maintenance organisations and parts suppliers may see increased business. (Linked to “Applicability” and “Compliance”.)\n\n- Incentives: With shorter allowable life, operators have an incentive to monitor hub cycles more closely and to budget for earlier replacement or overhaul. Suppliers may have an incentive to prioritise production or stock of the listed hub part numbers. (Linked to “Applicability”; “Document”.)\n\n- Trade-offs and opportunity costs: Reducing cyclic life lowers the risk of in-service hub failure (the AD’s operational aim), at the cost of higher maintenance spend, increased downtime, and use of maintenance resources and spare parts that could otherwise be deployed elsewhere.\n\nCompliance burden and implementation risk\n\n- The AD delegates the technical specifics to the referenced Requirement Document(s). That creates a compliance burden of obtaining and following the external documents (FAA AD 77-01-07 or AD/PW-T/41). If the Requirement Document requires specific inspection intervals, life limits or replacement procedures, operators must incorporate those into maintenance planning and records. Relying on external documents also creates an implementation dependency: enforcement and effective compliance depend on availability and clarity of those documents. (See “Document”; “Compliance”.)\n\nRegulatory authority and discretion\n\n- The AD prescribes mandatory compliance with the external Requirement Document; this AD text itself provides limited technical detail and limited regulatory discretion to operators beyond following the specified document. The decision to change allowable life and the technical prescriptions are expressed through the referenced ADs/documents. (See “Document”; “Compliance”.)\n\nNet operational effect (concrete, mechanical summary)\n\n- Engines listed with the listed hub part numbers must be treated according to reduced cyclic-life rules laid out in the referenced Requirement Document. Practically, that means earlier or more frequent inspections, overhauls or replacements of the fifth-stage turbine hubs, paid for and managed by the operator/owner, enforced under the Civil Aviation safety framework through the referenced ADs. (See “Applicability”; “Document”; “Compliance”.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific metallurgical fatigue issue identified in 1977. It has not expanded beyond its original purpose of mandating reduced cyclic life limits for specific turbine hub part numbers."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 7 defined engine models and 5 part numbers specified","Single operative requirement: compliance with external reference documents","No nested exceptions, conditional logic, or cross-references to other legislation","No interpretation section or defined terms beyond standard aviation abbreviations (P/N = Part Number, AD = Airworthiness Directive)","Straightforward applicability test: if engine model matches list AND contains listed part numbers, directive applies"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific Pratt & Whitney JT9D jet engines used in aircraft.\n\n**What it does:**\n- **Reduces the 'cyclic life'** of certain fifth-stage turbine hubs — meaning these parts must be replaced or inspected more frequently than originally planned.\n- A 'cyclic life' limit counts how many times an engine can start, run, and shut down (flight cycles) before a part wears out. Metal fatigue from repeated heating and cooling makes parts crack over time.\n\n**Who it affects:**\n- Owners and operators of aircraft with JT9D-3A, -7, -7A, -7H, -7AH, -7F, or -30 engines\n- Specifically those containing turbine hubs with part numbers: 704705, 714905, 718905, 719205, or 726805\n\n**Why it matters:**\n- **Safety critical.** Turbine hubs spin at extreme speeds and temperatures. If they fail, the engine can destroy itself and potentially damage the aircraft.\n- The FAA (American regulator) discovered these hubs wear out faster than expected. This AD adopts the American safety finding for Australian-registered aircraft.\n- Compliance is mandatory — operators must follow the referenced FAA document (AD 77-01-07) or the equivalent Australian document (AD/PW-T/41) to keep their aircraft legally airworthy."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt9d-9-fifth-stage-turbine-hubs-reduction-of-cyclic-life","history":"/api/acts/ad-jt9d-9-fifth-stage-turbine-hubs-reduction-of-cyclic-life/history","analysis":"/api/acts/ad-jt9d-9-fifth-stage-turbine-hubs-reduction-of-cyclic-life/analysis","conflicts":"/api/acts/ad-jt9d-9-fifth-stage-turbine-hubs-reduction-of-cyclic-life/conflicts","importantCases":"/api/acts/ad-jt9d-9-fifth-stage-turbine-hubs-reduction-of-cyclic-life/important-cases","documents":"/api/acts/ad-jt9d-9-fifth-stage-turbine-hubs-reduction-of-cyclic-life/documents"}}