{"id":"F2006B07248","name":"AD/T53/19 - N2 Accessory Drive","slug":"ad-t53-19-n2-accessory-drive","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49134,"registerId":"commonwealth-F2006B07248-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/T53/19 - N2 Accessory Drive","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)  \nAlliedSignal (Lycoming) Turbine Engines \\- T53 Series\n\nAD/T53/19 N2 Accessory Drive 8/97\n\nApplicability: AlliedSignal (formerly Textron Lycoming) T5311, T5313, T5317, T53-L-11, T53-L- 13 and T53-L-703 series engines.\n\nRequirement: To prevent possible uncommanded engine acceleration resulting from N2 accessory drive assembly disengagement, remove from service N2 spur gear nut retainers (lock cups) part number (P/N) 1-070-066-01 in accordance with the following AlliedSignal Aerospace Service Bulletins (SB):\n\n1: T5311 and T53-L-11 series engines: 2: T5313B and T5317 series engines: 3: T53-L-13B/SSA/SSB series engines: 4: T53-L-13B/SSD series engines:\n\n5: T53-L-703 series engines:\n\n  \nSB No. T5311/T53-L-11-0080.\n\nSB No. T5313B/T5317-0081 Revision 1\\. SB T53-L-13B-0082 Revision 1\n\nSB T53-L-13B/D-0083.\n\nSB T53-L-703-0084 Revision 1.\n\nNote: FAA Airworthiness Directive 97-07-05 refers.\n\nCompliance: Within 300 hours time in service or prior to 17 July 1999, whichever occurs first.\n\nThis airworthiness directive becomes effective on 17 July 1997.\n\nBackground: This directive has been issued to require the removal from service of certain part number N2 spur gear nut retainers in response to reports of N2 spur gear retainer separation. Separation of the retainer could result in N2 accessory drive disengagement and uncommanded engine acceleration.","sortOrder":0}],"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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope: addressing a specific mechanical defect in specific engine models. It has not expanded beyond its original safety purpose of preventing uncommanded engine acceleration due to N2 accessory drive disengagement."},"complexity_factors":["Single, specific mechanical defect addressed (one part number)","Clear applicability list (6 specific engine series)","Straightforward compliance requirement (remove part per manufacturer bulletins)","Simple time-based compliance deadline (300 hours or fixed date)","No nested exceptions, conditional logic, or cross-references to other legislation","Only one defined term used (N2 accessory drive - explained in context)","Short document (approximately 200 words)"],"plain_english_summary":"This Airworthiness Directive requires operators of specific AlliedSignal (Lycoming) T53-series turbine engines to remove a faulty N2 spur gear lock cup (PN 1-070-066-01) because it can separate in service, allowing the N2 accessory drive to disengage and cause uncommanded engine acceleration—a serious flight safety hazard. \n\nAffected operators must comply within 300 flight hours or by 17 July 1999 (effective 17 July 1997) and follow the applicable service bulletins for removal."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument targets removal of a specified part number on listed T53-series engines and requires compliance within a set timeframe, referencing manufacturer service bulletins. The text contains no indication that the directive's scope was expanded or narrowed from its stated purpose in this document."},"complexity_factors":["Technical specificity: mandates removal of a single part number (P/N 1-070-066-01) that must be correctly identified (Requirement).","Multiple engine models listed, so operators across several fleet types must check applicability (Applicability).","Execution relies on manufacturer service bulletins for procedures, creating dependency on external technical instructions (Requirement).","Short, firm compliance window — 300 flight hours or a calendar date — imposes scheduling and logistics pressure (Compliance).","Safety-critical consequence (risk of uncommanded engine acceleration) raises enforcement and inspection intensity (Background).","Limited regulatory discretion: the AD specifies mandatory action and deadline rather than optional measures (Requirement; Compliance)."],"plain_english_summary":"This airworthiness directive requires operators of AlliedSignal (Lycoming) T53-series engines to remove N2 spur gear nut retainers (lock cups) P/N 1-070-066-01 and follow the listed AlliedSignal service bulletins to prevent possible uncommanded engine acceleration (Requirement; Background). Operators pay for and perform the replacement; compliance is mandatory within 300 flight hours or by 17 July 1999, as required by the Civil Aviation Safety Authority (Compliance)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-t53-19-n2-accessory-drive","history":"/api/acts/ad-t53-19-n2-accessory-drive/history","analysis":"/api/acts/ad-t53-19-n2-accessory-drive/analysis","conflicts":"/api/acts/ad-t53-19-n2-accessory-drive/conflicts","importantCases":"/api/acts/ad-t53-19-n2-accessory-drive/important-cases","documents":"/api/acts/ad-t53-19-n2-accessory-drive/documents"}}