{"id":"F2006B07406","name":"AD/TFE 731/26 - Low Pressure Turbine First and Second Stage Disc Suspect Material Properties","slug":"ad-tfe-731-26-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49628,"registerId":"commonwealth-F2006B07406-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TFE 731/26 - Low Pressure Turbine First and Second Stage Disc Suspect Material Properties","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 \\- TFE731 Series\n\nAD/TFE731/26 Low Pressure Turbine First and Second\n\nStage Disc Suspect Material Properties\n\n  \n3/95\n\nApplicability: AlliedSignal TFE731-3 series engines as detailed in AlliedSignal Alert Service Bulletin No. TFE731-A72-3557.\n\nRequirement: Replace certain first and second stage low pressure turbine discs as listed by serial number in AlliedSignal Alert Service Bulletin No. TFE731-A72-3557.\n\nCompliance: Effective 2 March 1995: As detailed in the Requirement Document.\n\nBackground: This Directive has been issued to require the removal from service of certain turbine discs suspected of having a material micro-structure with unacceptable crack growth properties. This is both an engine in-flight shutdown and a disc containment concern.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":2658},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive maintains its original narrow scope addressing a specific material defect in specific turbine engine discs. No evidence of scope expansion beyond the original safety concern regarding crack growth properties in TFE731-3 series engines."},"complexity_factors":["Requires cross-reference to external technical document (AlliedSignal Alert Service Bulletin No. TFE731-A72-3557) for serial number identification","Technical aviation terminology (e.g., 'low pressure turbine disc', 'material micro-structure') requires domain knowledge","Specific part identification by serial number rather than general description"],"plain_english_summary":"**What this does:** This is a mandatory safety directive (called an Airworthiness Directive) that orders aircraft operators to replace specific engine parts on certain jet engines.\n\n**Who it affects:** Owners and operators of AlliedSignal TFE731-3 series turbine engines (commonly used in business jets).\n\n**What must be done:** If your engine contains specific first or second stage low-pressure turbine discs (identified by serial numbers listed in AlliedSignal Alert Service Bulletin TFE731-A72-3557), you must replace those discs.\n\n**Why it matters:** Some turbine discs were manufactured with defective material that could develop cracks too easily. This creates two serious safety risks: the engine could shut down during flight, or a disc could break apart and puncture the engine casing (a 'disc containment' failure), potentially damaging the aircraft or injuring passengers."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tfe-731-26-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties","history":"/api/acts/ad-tfe-731-26-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/history","analysis":"/api/acts/ad-tfe-731-26-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/analysis","conflicts":"/api/acts/ad-tfe-731-26-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/conflicts","importantCases":"/api/acts/ad-tfe-731-26-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/important-cases","documents":"/api/acts/ad-tfe-731-26-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/documents"}}