{"id":"F2006B07465","name":"AD/TPE 331/53 - Third Stage Replacement","slug":"ad-tpe-331-53-third-stage-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49834,"registerId":"commonwealth-F2006B07465-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TPE 331/53 - Third Stage Replacement","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 (Garrett/AiResearch) Turbine Engines \\- TPE 331 Series\n\nAD/TPE 331/53 Third Stage Replacement 6/98\n\nApplicability: TPE331-1, \\-2, \\-2UA, \\-3U, \\-3UW, \\-3U, \\-5, \\-5A, \\-5AB, \\-5B, \\-6, \\-6A engines\n\nincorporating a part number (P/N) 868379-3 third stage turbine stator not inspected in accordance with National Flight Services Alert Service Bulletin (ASB) Number NF- A72-10961.\n\nRequirement: Replace applicable third stage turbine stator P/N 868379-3 in accordance with AlliedSignal Service Bulletin TPE331-A72-0861 Revision 2.\n\nNote 1: FAA Airworthiness Directive 98-04-15 refers.\n\nNote 2: The requirements of this directive do not supersede the in-service inspection requirements of Airworthiness Directive AD/TPE331/41 Amdt. 2.\n\nCompliance: As detailed in the requirement document.\n\nThis Airworthiness Directive becomes effective on 21 May 1998.\n\nBackground: This directive has been issued to require the replacement of certain third stage turbine stators. The requirement reflects advice of fatigue cracking may result in the stator moving aft and contacting the third stage turbine wheel. If uncorrected, this could result in uncontained failure of the third stage turbine wheel.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in specific engine models. It has not expanded beyond its original purpose of mandating replacement of a faulty turbine component."},"complexity_factors":["Short, single-purpose directive (approximately 200 words)","Only 1 defined term implicitly used (part number P/N 868379-3)","Clear applicability section listing specific engine models","Single requirement with reference to external technical document (Service Bulletin)","Two straightforward notes clarifying relationship to other regulations","No nested conditional logic or exceptions within the directive text itself","Complexity arises primarily from external cross-references to technical service bulletins rather than internal legislative structure"],"plain_english_summary":"This CASA Airworthiness Directive mandates replacing a specific faulty third-stage turbine stator (P/N 868379-3) installed in certain AlliedSignal (Garrett/AiResearch) TPE331 engines. Operators with affected engines must comply by the service-bulletin deadlines or grounding applies.\n\nIt’s required because fatigue cracking can let the stator break into the turbine wheel, causing uncontained failure and potential catastrophic engine damage. This AD complements an earlier inspection AD and aligns with FAA AD 98-04-15."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive targets replacement of a specific third-stage stator that was not previously inspected per the referenced ASB; it does not broaden inspection obligations and explicitly preserves the in-service inspections required by AD/TPE331/41 Amdt. 2."},"complexity_factors":["Narrow technical scope: applies only to specific TPE331 engine models and a single part number (P/N 868379-3).","Dependence on an external service bulletin (AlliedSignal TPE331-A72-0861 Rev 2) to set replacement procedures and timing.","Cross-reference to previous inspection AD (AD/TPE331/41 Amdt. 2) preserves separate obligations and creates interaction risk.","Ambiguous compliance timing in the directive text (‘as detailed in the requirement document’) increases implementation reliance on the service bulletin.","Operational cost and logistics sit with aircraft operators (parts, downtime, maintenance resources)."],"plain_english_summary":"This Airworthiness Directive requires operators of listed AlliedSignal TPE331 engines that contain third-stage turbine stator P/N 868379-3 (and that were not inspected under NF‑A72‑10961) to replace that stator following AlliedSignal Service Bulletin TPE331‑A72‑0861 Revision 2. The Civil Aviation Safety Authority enforces the requirement. The stated safety purpose is to prevent fatigue cracking that could let the stator move aft and contact the third-stage turbine wheel. Aircraft operators pay for replacements and must follow the specified service bulletin timing and procedures."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tpe-331-53-third-stage-replacement","history":"/api/acts/ad-tpe-331-53-third-stage-replacement/history","analysis":"/api/acts/ad-tpe-331-53-third-stage-replacement/analysis","conflicts":"/api/acts/ad-tpe-331-53-third-stage-replacement/conflicts","importantCases":"/api/acts/ad-tpe-331-53-third-stage-replacement/important-cases","documents":"/api/acts/ad-tpe-331-53-third-stage-replacement/documents"}}