{"id":"F2006B07447","name":"AD/TPE 331/37 - Second Stage Turbine Rotor Assembly - Cyclic Life Reduction","slug":"ad-tpe-331-37-second-stage-turbine-rotor-assembly-cyclic-life-reduction","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49768,"registerId":"commonwealth-F2006B07447-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TPE 331/37 - Second Stage Turbine Rotor Assembly - Cyclic Life Reduction","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 331/37 Second Stage Turbine Rotor Assembly \\- Cyclic Life Reduction\n\n  \n7/88\n\nDM\n\nApplicability: TPE 331-10 and \\-11 series engine models listed in the Requirement document fitted with second stage turbine wheel assemblies P/N 3102106-1/-6 and -8.\n\nRequirement: Replace second stage turbine wheels in accordance with the Accomplishment Instructions of Garrett SB TPE 331-A72-0571.\n\nCompliance: Forthwith from 9 May 1988 in accordance with the schedule detailed in the Requirement document Para 1D. A copy of which is reproduced below:-\n\nWheel Cycles (CSN)Replacement Schedule\n\n0 to 4400 \\- Replace prior to 4800 cycles since new (CSN).\n\n4401 to 5000 \\- Replace within 400 additional cycles or 5200 cycles since new (CSN), whichever occurs first.\n\n5001 to 5900 \\- Replace within 200 additional cycles or 6000 cycles since new (CSN), whichever occurs first.\n\n5901 to 6800 \\- Replace within 100 additional cycles or 6800 cycles since new (CSN), whichever occurs first.\n\nNote 1: All second stage turbine rotor assemblies with 4800 or more cycles must be replaced prior to 1 January 1989.\n\nNote 2: No second stage turbine rotor assembly shall exceed 6800 Total cycles.\n\nBackground: The manufacturer in SB TPE 331-A72-0571 advises an instance of second stage turbine wheel separation at less than the previously specified cycle life limit. Because of this the cycle life limit of these items have been reduced from 6800 cycles to 4800 cycles. This life change is now reflected in AD/TPE 331/3 Amdt 3 which is issued concurrent with this Directive.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1976},"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive maintains its original safety focus of mandating replacement of specific turbine rotor assemblies following the identification of premature failure risks. It has not expanded beyond this specific technical remediation."},"complexity_factors":["Technical aviation terminology including 'CSN' (Cycles Since New) and manufacturer part numbers (P/N)","Four-tiered conditional compliance schedule with mathematical thresholds","Cross-reference to external manufacturer service bulletin for technical accomplishment instructions","Narrow applicability limited to specific engine series and three distinct part numbers"],"plain_english_summary":"This AD orders owners/operators of AlliedSignal (Garrett) TPE331-10/-11 engines to replace certain second-stage turbine wheels (P/N 3102106-1/6/8) before they hit mandated cycle limits because the wheels may separate prematurely, creating a serious safety hazard. Compliance requires replacement per the manufacturer’s Service Bulletin TPE331-A72-0571, with an absolute prohibition on exceeding 6,800 total cycles."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tpe-331-37-second-stage-turbine-rotor-assembly-cyclic-life-reduction","history":"/api/acts/ad-tpe-331-37-second-stage-turbine-rotor-assembly-cyclic-life-reduction/history","analysis":"/api/acts/ad-tpe-331-37-second-stage-turbine-rotor-assembly-cyclic-life-reduction/analysis","conflicts":"/api/acts/ad-tpe-331-37-second-stage-turbine-rotor-assembly-cyclic-life-reduction/conflicts","importantCases":"/api/acts/ad-tpe-331-37-second-stage-turbine-rotor-assembly-cyclic-life-reduction/important-cases","documents":"/api/acts/ad-tpe-331-37-second-stage-turbine-rotor-assembly-cyclic-life-reduction/documents"}}