{"id":"F2006B07400","name":"AD/TFE 731/17 - L.P. Turbine Third Stage Rotor Disc","slug":"ad-tfe-731-17-l-p-turbine-third-stage-rotor-disc","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49608,"registerId":"commonwealth-F2006B07400-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TFE 731/17 - L.P. Turbine Third Stage Rotor Disc","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/TFE731/17 L.P. Turbine Third Stage Rotor Disc 7/89 DM\n\nApplicability: TFE 731 series engines which may have suspect L.P. turbine third stage rotor disc part number 3074756-1/-2 whose serial numbers are listed in the Requirement document.\n\nRequirement: Remove from service specific serial numbered L.P. turbine third stage rotor disc P/N 3074756-1/-2 (part of rotor assy P/N 3074757-1) whose serial numbers are listed in Table 1 of Allied Signals (Garrett) S.B. TFE 731-72-3387.\n\nCompliance: Unless already accomplished, within 100 hours time in service after 10 May 1989\\. Background: The manufacturer, in Service Bulletin TFE 731-72-3387, has advised that specific\n\nS/No L.P. third stage turbine discs have been manufactured with the outside diameter\n\n0.020 inch oversize. The inspection, rework and reidentification of oversize disc assemblies can be accomplished by fitting shorter blades. This Directive is issued to ensure that suspect assemblies are removed in a timely manner to prevent turbine failures occurring.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive targets specific serial-numbered LP third-stage rotor discs listed in the manufacturer’s Service Bulletin and mandates their removal/rework within a set timeframe. The text shows no expansion beyond those listed parts or beyond the stated compliance window (Applicability; Requirement; Compliance)."},"complexity_factors":["Narrow, serial-numbered applicability reduces scope but requires traceability to SB Table 1 (Applicability; Requirement).","Short, fixed compliance window (100 flight hours after 10 May 1989) creates scheduling pressure for operators (Compliance).","Technical rework option (fitting shorter blades) requires engineering/maintenance capability and possible parts substitution (Background).","Reliance on manufacturer service bulletin for identification and procedures concentrates decision authority and technical detail in the SB (Requirement; Background).","Operational disruption and replacement cost borne by operators; potential need for records/reidentification after rework (Requirement; Background)."],"plain_english_summary":"Mechanically, this airworthiness directive requires operators to remove specific L.P. turbine third-stage rotor discs (`P/N 3074756-1/-2`; serial numbers listed in AlliedSignal Service Bulletin TFE731-72-3387) from service within 100 flight hours after 10 May 1989. It affects operators of TFE731-series engines, who bear inspection, removal and replacement or rework costs; the manufacturer identified a 0.020‑inch oversize outside diameter and advised inspection, rework and reidentification can be done by fitting shorter blades (Requirement; Compliance; Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific manufacturing defect in a specific engine series. It has not expanded beyond its original purpose of mandating removal of defective rotor discs."},"complexity_factors":["Single, specific mechanical defect addressed (oversized disc diameter)","Only one part number family affected (P/N 3074756-1/-2)","Clear compliance deadline (100 hours time in service after fixed date)","No nested exceptions or conditional logic — applies to listed serial numbers, full stop","No defined terms section — uses standard aviation terminology","Single cross-reference to manufacturer's Service Bulletin for serial number table","Approximately 150 words total"],"plain_english_summary":"This AD requires operators of AlliedSignal (Garrett/AiResearch) TFE 731 series engines to identify and remove from service certain low-pressure turbine third-stage rotor discs (PN 3074756-1 and -2) manufactured with an oversize OD. Affected discs must be taken out within 100 flight hours of the effective date. Failure to comply risks turbine failure, engine loss, and potential in-flight emergencies."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tfe-731-17-l-p-turbine-third-stage-rotor-disc","history":"/api/acts/ad-tfe-731-17-l-p-turbine-third-stage-rotor-disc/history","analysis":"/api/acts/ad-tfe-731-17-l-p-turbine-third-stage-rotor-disc/analysis","conflicts":"/api/acts/ad-tfe-731-17-l-p-turbine-third-stage-rotor-disc/conflicts","importantCases":"/api/acts/ad-tfe-731-17-l-p-turbine-third-stage-rotor-disc/important-cases","documents":"/api/acts/ad-tfe-731-17-l-p-turbine-third-stage-rotor-disc/documents"}}