{"id":"F2006B07247","name":"AD/T53/18 - Gas Producer and Power Turbine Discs and Spacers","slug":"ad-t53-18-gas-producer-and-power-turbine-discs-and-spacers","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49132,"registerId":"commonwealth-F2006B07247-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/T53/18 - Gas Producer and Power Turbine Discs and Spacers","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)  AlliedSignal (Lycoming) Turbine Engines - T53 Series\n\n \n\n# AD/T53/18 Gas Producer and Power Turbine Discs and Spacers\n\nApplicability: T5313B turboshaft engines.\n\n# 9/87\n\nDM\n\n \n\nRequirement: Remove from service: GPT disc P/N 1-100-133-01, PT disc P/N 1-140-272-01, GPT spacer P/N 1-100-294-03, PT spacer P/N 1-140-169-03, and PT spacer P/N 1- 140-169-04 in accordance with FAA AD 87-12-05 Amdt 39-5640.\n\n \n\nNote: Lycoming SB No. 0020 Revision 2 dated 3 January 1986 refers (this is the Requirement Document of AD/T53/1 Amdt 1).\n\n \n\nCompliance: Unless already accomplished; in accordance with the schedules detailed in FAA AD 87-12-05 Paras (a) to (e) with effect from 20 July 1987.\n\n \n\nBackground: The service cyclic life for the GPT disc and the PT second stage disc has been reduced and a cyclic life limit established for GPT and PT spacers.\n\n \n\nThis Directive is issued to assure the timely removal from service of affected components to prevent uncontained engine failures.\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":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-limited safety directive issued in 1987. It has not evolved beyond its original purpose of mandating removal of specific at-risk components. The scope remains tightly confined to the T5313B engine and the five enumerated parts."},"complexity_factors":["Single, specific applicability (one engine model: T5313B)","Clear parts list with 5 specific part numbers","References external FAA directive for detailed compliance schedules rather than reproducing them","No defined terms section","No nested exceptions or conditional logic — straightforward removal requirement","Short document (approximately 200 words of substantive content)"],"plain_english_summary":"This Airworthiness Directive mandates early removal of five specific parts (two turbine discs and three spacers) from AlliedSignal/Lycoming T5313B turboshaft engines because they wear faster than expected and can cause catastrophic in‑flight failures. \n\nIt applies to operators, owners and maintenance organizations of affected helicopters and began taking effect 20 July 1987 with staged removal schedules based on engine usage."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Yes. The directive narrows allowable in-service life by reducing cyclic life for the GPT and PT second‑stage discs and by establishing cyclic life limits for GPT and PT spacers, thereby expanding the set of components that must be removed earlier than before (Background; Requirement; Note referencing Lycoming SB No. 0020 Rev 2)."},"complexity_factors":["Direct cross‑reference to FAA AD 87-12-05 Amdt 39-5640 as the mandatory compliance schedule (Requirement: \"in accordance with FAA AD 87-12-05 Amdt 39-5640\").","Multiple specific part numbers required for removal (GPT disc P/N 1-100-133-01; PT disc P/N 1-140-272-01; GPT spacer P/N 1-100-294-03; PT spacers P/N 1-140-169-03 and P/N 1-140-169-04) increasing inventory-tracking tasks (Requirement).","Introduction of reduced cyclic life limits and new cyclic life limit for spacers requires operators to track cycles and maintenance records (Background: \"service cyclic life ... reduced\"; \"cyclic life limit established\").","Compliance effective date and scheduled paras impose retrospective action and a required timetable (Compliance: \"with effect from 20 July 1987\").","Reliance on a manufacturer service bulletin as the requirement document (Note: Lycoming SB No. 0020 Revision 2 dated 3 January 1986), creating dependency on SB interpretation for implementation.","Safety-critical consequence (risk of uncontained engine failures) raises urgency and reduces regulator/operator discretion (Background: \"to prevent uncontained engine failures\").","Operational and logistical burdens: replacing retired parts may require sourcing scarce spares and planning out-of-service time for engines (implied by Requirement and Background)."],"plain_english_summary":"This airworthiness directive orders operators of T5313B turboshaft engines to remove specified gas‑producer (GPT) and power‑turbine (PT) discs and spacers by the timelines in FAA AD 87‑12‑05 (effective 20 July 1987). Removal is compulsory for the listed part numbers and must follow the FAA schedule.  \n\nThe directive states cyclic life limits for the GPT and PT discs were reduced and new life limits set for spacers to prevent uncontained engine failures. Compliance and replacement costs fall to operators, who must track component cycles and source replacements."}},"importantCases":[],"_links":{"self":"/api/acts/ad-t53-18-gas-producer-and-power-turbine-discs-and-spacers","history":"/api/acts/ad-t53-18-gas-producer-and-power-turbine-discs-and-spacers/history","analysis":"/api/acts/ad-t53-18-gas-producer-and-power-turbine-discs-and-spacers/analysis","conflicts":"/api/acts/ad-t53-18-gas-producer-and-power-turbine-discs-and-spacers/conflicts","importantCases":"/api/acts/ad-t53-18-gas-producer-and-power-turbine-discs-and-spacers/important-cases","documents":"/api/acts/ad-t53-18-gas-producer-and-power-turbine-discs-and-spacers/documents"}}