{"id":"F2006B08675","name":"AD/CT58/17 - Starter Driveshaft Bearing","slug":"ad-ct58-17-starter-driveshaft-bearing","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51785,"registerId":"commonwealth-F2006B08675-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# ![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nGeneral Electric Turbine Engines \\- CT58 Series","sortOrder":0},{"sectionNumber":"AD/CT58/17 Starter Driveshaft Bearing 7/","sectionType":"part","heading":"AD/CT58/17 Starter Driveshaft Bearing 7/2004","content":"# AD/CT58/17 Starter Driveshaft Bearing 7/2004\n\nApplicability: Models CT58-100-1, -100-2, -110-1 Engines; Model CT58-140-1 Engines Serial Numbers (SN’s) 295001 through 295018; Model T58-GE-1 Engines; and Model T58- GE-5 Engines, SN’s 285001 through 285016\n\nRequirement: On installations that incorporate General Electric starter Model 2CM270D3 or 2CM270D5, install front frame accessory drive pinion bearing, P/N 4002T03 (Vendor P/N HDB003-9), and modify starter by incorporating a new field winding assembly, P/N 36A227553G01 or 36A227554G01. Stamp a \"B\" on the starter nameplate after the starter model number on starters, Model 2CM270D3, and a \"C\" on the nameplate after the starter model number on starters, Model 2CM270D5, to indicate the field winding assembly has been changed. (Starter Models 2CM270D3B and 2CM270D5C have been modified at the factory.)\n\nOn installations which incorporate starters other than General Electric Model 2CM270D3 or 2CM270D5, install front frame accessory drive pinion bearing, P/N 4002T03D03 (Vendor P/N HDB003-9).\n\nNote: FAA AD 64-26-02 Amdt 39-3 refers.\n\nCompliance: Unless previously accomplished within 14 days after the effective date of this AD. This Airworthiness Directive becomes effective on 8 July 2004.\n\nBackground: Failure of the starter drive shaft bearing can result in engine power loss. This Directive calls for modification of the starter drive shaft bearing to prevent the unsafe condition from occurring.","sortOrder":1}],"analysis":{"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"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive addresses a narrowly defined safety risk — starter driveshaft bearing failure — and prescribes targeted hardware replacements and a starter winding modification to mitigate that risk. It does not expand beyond that technical fix (no new regulatory programs, fees, or broader operational requirements). Therefore the scope has not grown beyond the original safety-correction purpose set out in the Background and Requirement sections."},"complexity_factors":["Short, single-issue instrument focused on one unsafe condition","Clear applicability limited to specific engine models and serial number ranges (low breadth)","Few part numbers specified (around 4 OEM/vendor part numbers)","Simple conditional branching: one treatment for two specific GE starter models, a different treatment for all other starters","Single, short compliance window (14 days) and no phased or repeated actions","One external cross-reference to an FAA AD (minor cross-reference)"],"plain_english_summary":"**What this directive does (mechanics):**\n\n- Requires particular modifications to the starter/drive-shaft assembly on certain General Electric CT58/T58 turbine engines to correct a risk of starter driveshaft bearing failure. (See: Requirement section.)\n\n**Which engines are affected:**\n\n- Models CT58-100-1, CT58-100-2, CT58-110-1; CT58-140-1 with serial numbers 295001–295018; and T58-GE-1 and T58-GE-5 with serial numbers 285001–285016. (See: Applicability section.)\n\n**What operators must do:**\n\n- If the engine installation uses a General Electric starter Model 2CM270D3 or 2CM270D5:\n  - Fit the front frame accessory drive pinion bearing, part number (P/N) 4002T03 (vendor P/N HDB003-9).\n  - Modify the starter by installing a new field winding assembly, P/N 36A227553G01 or 36A227554G01.\n  - After modification, stamp a \"B\" after the model number on 2CM270D3 starters and a \"C\" after the model number on 2CM270D5 starters to show the field winding was changed. (Factory-modified starters already appear as 2CM270D3B or 2CM270D5C.) (See: Requirement section.)\n- If the installation uses a starter model other than the two GE models above: fit the front frame accessory drive pinion bearing P/N 4002T03D03 (vendor P/N HDB003-9). (See: Requirement section.)\n\n**When it must be done:**\n\n- The work must be completed within 14 days after the AD's effective date. The AD sets an explicit compliance window. (See: Compliance section.)\n\n**Why the rule exists:**\n\n- The Background section says failure of the starter driveshaft bearing can cause engine power loss. The AD prescribes the bearing replacement and starter modification to prevent that unsafe condition.\n\n**Who pays and who decides:**\n\n- Aircraft owners/operators are responsible for arranging and paying for the parts and maintenance, and for stamping/marking modified starters as required. The CASA delegate issued the AD under aviation safety regulation authority and sets the mandatory actions and timing. (See: opening paragraph and Requirement/Compliance sections.)\n\n**Practical implementation & trade-offs (analytical lens):**\n\n- Direct costs: purchase of specified bearings and field winding assemblies, labour/time in a maintenance environment, and any aircraft downtime during the work. (Requirement + Compliance sections.)\n- Operational effect: the AD forces a short-term operational interruption (up to the time it takes to source parts and complete the work) in exchange for reduced risk of in-service starter/bearing failure. The AD does not quantify reliability gains or costs — operators must judge those when scheduling work.\n- Supply and timing risks: the AD specifies exact part numbers (OEM and vendor P/Ns). If parts are scarce, operators may face scheduling delays or higher prices. Using incorrect parts risks non-compliance and may not mitigate the unsafe condition. (Requirement section.)\n- Administrative burden: modified starters must be physically stamped (a permanent marking), which affects traceability and maintenance records; logbook entries and certification by authorised maintenance personnel will be necessary. (Requirement section.)\n- Choice and substitution: operators with already factory-modified starters (models noted as B or C) do not need to repeat the modification. Operators using non-GE starters have a single bearing-change requirement rather than the winding modification. (Requirement section.)\n- Concentrated vs diffuse effects: the directive creates immediate demand for the specified parts and for authorised maintenance hours (a concentrated commercial benefit to parts suppliers and maintenance providers), while costs are borne across the affected operators (diffuse). The AD itself does not allocate funding or compensation. (Inferred from the Requirement and Compliance structure.)\n- Compliance and safety trade-off: the AD imposes mandatory technical fixes to address a specific safety hazard. This reduces regulatory discretion at operator level (they must follow the parts and modifications specified) but also reduces operator decision-making about how to address the particular bearing-failure hazard.\n\n**Reference to external material:**\n\n- The AD notes a related FAA AD (FAA AD 64-26-02 Amdt 39-3) for further reference; operators may consult that for additional context or technical detail. (See: Note in Requirement section.)"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope — addressing a specific mechanical failure mode (starter driveshaft bearing failure) in specific engine models. The applicability is tightly constrained by model and serial number, and the requirements remain focused on the single safety issue identified in the background."},"complexity_factors":["Multiple conditional requirements based on starter model type (2CM270D3/D5 vs. others)","Specific part numbers and vendor part numbers requiring cross-referencing","Serial number ranges limiting applicability to specific engine batches","Mandatory stamping/marking requirement for traceability","Reference to external FAA directive (AD 64-26-02 Amdt 39-3) for additional context"],"plain_english_summary":"This safety order requires owners/operators of certain GE CT58 and T58 turbine engines (listed models and serial-number ranges) to replace a starter driveshaft bearing, modify the starter’s electrical winding as applicable, and mark the starter (“B” or “C”) to show compliance.  \n\nIt addresses a bearing failure that can cause complete engine power loss in flight; compliance was required within 14 days after 8 July 2004."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ct58-17-starter-driveshaft-bearing","history":"/api/acts/ad-ct58-17-starter-driveshaft-bearing/history","analysis":"/api/acts/ad-ct58-17-starter-driveshaft-bearing/analysis","conflicts":"/api/acts/ad-ct58-17-starter-driveshaft-bearing/conflicts","importantCases":"/api/acts/ad-ct58-17-starter-driveshaft-bearing/important-cases","documents":"/api/acts/ad-ct58-17-starter-driveshaft-bearing/documents"}}