{"id":"F2010L00090","name":"AD/TFE731/26 Amdt 1 - Low Pressure Turbine First and Second Stage Disc Suspect Material Properties","slug":"ad-tfe731-26-amdt-1-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":122785,"registerId":"commonwealth-F2010L00090-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AlliedSignal (Garrett/AiResearch) Turbin","sectionType":"division","heading":"AlliedSignal (Garrett/AiResearch) Turbine Engines - TFE731 Series","content":"### AlliedSignal (Garrett/AiResearch) Turbine Engines - TFE731 Series\n\n| AD/TFE731/26 Amdt 1 | Low Pressure Turbine First and SecondStage Disc Suspect Material Properties | 1/2010 |\n| ------------------- | --------------------------------------------------------------------------- | ------ |\n\n| Applicability: | AlliedSignal TFE731-3 series engines as detailed in AlliedSignal Alert Service Bulletin (ASB) No. TFE731-A72-3557.                                                                                                                                                                                                                                                                                                                                                                                                         |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Replace certain first and second stage low pressure turbine discs as listed by serial number in AlliedSignal Alert Service Bulletin (ASB) No. TFE731-A72-3557.Note: FAA AD 95-07-02 refers.                                                                                                                                                                                                                                                                                                                                |\n| Compliance:    | Unless already accomplished in accordance with the previous issue of this Directive, within 100 hours time-in-service (TIS) after the effective date of this Directive.                                                                                                                                                                                                                                                                                                                                                    |\n|                | This Amendment becomes effective on 22 January 2010.                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |\n| Background:    | 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.This amendment references the applicable State of design Directive which is also applicable to AD/TFE731/24 Amdt 1. For information, AD/TFE731/34 is also applicable to first and second stage low pressure turbine discs, but unrelated to this Directive. |\n\n![](image.001.png)\n\nMike Higgins  \nDelegate of the Civil Aviation Safety Authority\n\n4 January 2010","sortOrder":0},{"sectionNumber":"AD/TFE731/26 Amdt 1","sectionType":"part","heading":"AD/TFE731/26 Amdt 1","content":"## AD/TFE731/26 Amdt 1","sortOrder":1},{"sectionNumber":"Low Pressure Turbine First and SecondSta","sectionType":"part","heading":"Low Pressure Turbine First and SecondStage Disc Suspect Material Properties","content":"## [Low Pressure Turbine First and Second  \nStage Disc Suspect Material Properties](http://casa.gov.au/ADfiles/turbine/tfe731/TFE731-026.pdf)","sortOrder":2},{"sectionNumber":"1/2010","sectionType":"part","heading":"1/2010","content":"## 1/2010","sortOrder":3}],"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"},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"This instrument is an amendment that clarifies and enforces mandatory removal of specific first‑ and second‑stage low‑pressure turbine discs identified by serial number (Requirement), sets a definitive 100‑hour TIS compliance window (Compliance), and aligns the Australian directive with the State of design and FAA directives (Background). In effect it narrows/clarifies which discs are affected and imposes a short, enforceable replacement deadline."},"complexity_factors":["Technical failure mode: material micro‑structure and crack‑growth properties require engineering assessment and safe‑life judgement (Background).","Identification burden: affected items are listed by serial number in the manufacturer ASB, so operators must cross‑check fleet serials (Applicability, Requirement).","Short compliance window: replacement required within 100 hours time‑in‑service creates scheduling and operational disruption pressure (Compliance).","Inter‑jurisdictional cross‑references: the amendment references the State of design Directive and FAA AD, requiring legal and technical alignment with foreign directives (Background, Requirement).","Logistics and supply: mandated disc replacements impose parts ordering, maintenance shop time, and potential lead‑time costs (Requirement).","Enforcement and records: CASA’s directive and effective date impose an administrative compliance obligation on operators and maintainers (Compliance).","Dependency on prior action: wording 'Unless already accomplished in accordance with the previous issue of this Directive' requires operators to track past compliance and updates (Compliance).","Safety consequence weighting: because the risk is in‑flight shutdown and containment, non‑compliance carries high operational risk, increasing the practical urgency and inspection rigor (Background)."],"plain_english_summary":"Requires owners/operators of AlliedSignal TFE731‑3 series engines to replace specific first‑ and second‑stage low‑pressure turbine discs listed by serial number in AlliedSignal Alert Service Bulletin No. TFE731‑A72‑3557 (Requirement). CASA’s Delegate made the amendment effective 22 January 2010 and mandates replacement within 100 hours time‑in‑service (Compliance). The discs are suspected of a material micro‑structure that gives unacceptable crack‑growth properties, creating an in‑flight shutdown and disc containment risk (Background). Operators bear replacement and downtime costs."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is an amendment (Amdt 1) to an existing directive, but it does not expand the scope beyond the original safety purpose. The amendment appears to update the effective date and reference the related State of design Directive, while maintaining the same core requirement: replacement of suspect turbine discs. The scope remains tightly focused on the specific material defect in specific engine models."},"complexity_factors":["Very short document (approximately 250 words)","Only 1 defined term implicitly used ('time-in-service' or TIS)","No nested conditional logic — single straightforward compliance requirement","Minimal cross-referencing (only references to related FAA and CASA directives for context)","Clear applicability criteria based on specific engine model and manufacturer service bulletin","Single compliance pathway with one exception clause ('unless already accomplished')"],"plain_english_summary":"This AD requires operators of AlliedSignal TFE731-3 series engines (as listed in ASB TFE731-A72-3557) to replace certain first- and second-stage low-pressure turbine discs because of a suspected material defect that can accelerate crack growth. The defect risks in-flight engine shutdown and uncontained disc failure, threatening aircraft and occupants.\n\nAffected discs must be replaced within 100 flight hours after the AD takes effect unless already addressed; this action aligns with FAA AD 95-07-02."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tfe731-26-amdt-1-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties","history":"/api/acts/ad-tfe731-26-amdt-1-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/history","analysis":"/api/acts/ad-tfe731-26-amdt-1-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/analysis","conflicts":"/api/acts/ad-tfe731-26-amdt-1-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/conflicts","importantCases":"/api/acts/ad-tfe731-26-amdt-1-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/important-cases","documents":"/api/acts/ad-tfe731-26-amdt-1-low-pressure-turbine-first-and-second-stage-disc-suspect-material-properties/documents"}}