{"id":"F2006B07394","name":"AD/TFE 731/10 - No. 1 Bearing - Replacement","slug":"ad-tfe-731-10-no-1-bearing-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49587,"registerId":"commonwealth-F2006B07394-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TFE 731/10 - No. 1 Bearing - 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 \\- TFE731 Series\n\nAD/TFE731/10 No. 1 Bearing \\- Replacement 3/86 TX\n\nApplicability: TFE 731-2, -3, -5 Series with Serial Nos. as listed in the Requirement Document. Requirement: Replace suspect defective Number 1 bearings of affected engines. G.T.E.C. Alert S.B.\n\nTFE 731-A72-3296 refers; or\n\nAD/AIR-T/51.\n\nCompliance: Unless already accomplished, within 25 hours time in service after 23 November 1984.\n\nBackground: This Directive is issued to remove from service defective No. 1 bearings. Following a reported failure, it has been established that defective bearings have been fitted to some engines. These engines have been identified in SB TFE 731-A72-3296.\n\nDefective bearings have insufficient roller end clearance which results in skidding and subsequent failure.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The document’s stated purpose is to remove defective Number 1 bearings from service on specific TFE731-2, -3 and -5 engines (Requirement; Background). Nothing in the text indicates a change from that original intent: the AD specifies which engines are affected, the remedial action (replacement of the No.1 bearing) and a compliance timeframe (Applicability; Requirement; Compliance)."},"complexity_factors":["Narrow, serial-number-specific applicability requiring cross-reference to the Requirement Document and service bulletin TFE 731-A72-3296 (Applicability; Requirement; Background).","Short and fixed compliance window (replace within 25 hours time in service after 23 November 1984) creates operational urgency (Compliance).","Technical diagnosis and replacement require qualified maintenance capability to identify and replace No.1 bearings (Requirement; Background).","Multiple external cross-references (G.T.E.C. Alert S.B.; TFE 731-A72-3296; AD/AIR-T/51) increase administrative steps to confirm applicability and procedure (Requirement; Background).","Potential supply, scheduling and downtime implications for operators but no novel regulatory mechanisms or discretionary approvals in the text (Requirement; Compliance)."],"plain_english_summary":"# What this directive does\n\nThis Airworthiness Directive (AD) orders that certain AlliedSignal (Garrett/AiResearch) TFE731 series turbine engines must have their Number 1 bearings replaced. The directive applies only to engines and serial numbers listed in the Requirement Document or identified in service bulletin TFE 731-A72-3296 (Applicability; Requirement). The mechanical action required is replacement of any suspect or defective No. 1 bearing (Requirement).\n\n# Who it affects\n\n- Aircraft owners and operators who have TFE731-2, -3 or -5 series engines with the serial numbers listed in the referenced documents (Applicability).  \n- Maintenance organisations that perform the bearing replacement and record compliance (Requirement; Compliance).\n\n# Deadline and compliance mechanics\n\n- If not already done, owners/operators must replace the suspect bearings within 25 hours time in service after 23 November 1984 (Compliance).  \n- The AD points operators to the manufacturer/service documents (G.T.E.C. Alert S.B.; TFE 731-A72-3296) that identify which engines are affected and the recommended service procedure (Requirement; Background).\n\n# Why it was issued\n\n- The AD was issued to remove defective Number 1 bearings from service after a reported failure showed that some engines had bearings with insufficient roller end clearance. That deficiency can cause rollers to skid and then fail (Background).\n\n# Practical effects, incentives and costs (mechanics, not judgement)\n\n- Who pays and acts: the aircraft owner/operator bears the direct costs of inspection, parts and labour to replace the bearings and must arrange downtime for the aircraft (Requirement; Compliance).  \n- Compliance burden: owners/operators must check serial numbers against the Requirement Document or service bulletin to determine applicability and then schedule the work within the short, specified window (Applicability; Requirement; Compliance).  \n- Operational trade-offs: replacing bearings may require removing the engine or scheduling maintenance downtime, creating short-term operational disruption and parts/labour demand (Requirement; Compliance).  \n- Safety incentive: operators face a mechanical failure risk if defective bearings remain in service; the AD converts that risk into a regulatory obligation to replace the parts within the set timeframe (Background; Compliance).  \n- Documentary dependencies and administrative steps: the AD relies on external documents (manufacturer alert/service bulletin and the Requirement Document); operators must consult those documents to confirm which serial numbers are covered and the recommended replacement procedure (Requirement; Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive issued in 1984/1986 with a single, specific purpose: mandating replacement of identified defective bearings. It has not expanded beyond its original technical safety scope."},"complexity_factors":["Very short document (approximately 150 words)","Only 3 defined applicability criteria (engine model series)","Single, unambiguous compliance requirement (25 hours time in service)","No nested exceptions or conditional logic","Clear cross-reference to external technical document (Service Bulletin) rather than internal legislative cross-referencing","Straightforward cause-and-effect explanation in Background section"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific repairs or inspections on aircraft.\n\n**What it does:**\nOrders the replacement of faulty \"Number 1 bearings\" in certain AlliedSignal (Garrett/AiResearch) TFE731 jet engines. These bearings are critical components that allow engine parts to rotate smoothly.\n\n**Who it affects:**\nOwners and operators of aircraft using TFE 731-2, -3, or -5 series engines with specific serial numbers listed in the referenced service bulletin.\n\n**Why it matters:**\nThe defective bearings have insufficient clearance (gap) between the rollers, causing them to \"skid\" instead of roll smoothly. This can lead to bearing failure, which could cause catastrophic engine failure in flight.\n\n**What must be done:**\nAffected bearings must be replaced within **25 flight hours** after 23 November 1984 (unless already done).\n\n**Key references:**\n- Service Bulletin TFE 731-A72-3296 (identifies which specific engines are affected)\n- Previous directive AD/AIR-T/51 (alternative compliance path)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-tfe-731-10-no-1-bearing-replacement","history":"/api/acts/ad-tfe-731-10-no-1-bearing-replacement/history","analysis":"/api/acts/ad-tfe-731-10-no-1-bearing-replacement/analysis","conflicts":"/api/acts/ad-tfe-731-10-no-1-bearing-replacement/conflicts","importantCases":"/api/acts/ad-tfe-731-10-no-1-bearing-replacement/important-cases","documents":"/api/acts/ad-tfe-731-10-no-1-bearing-replacement/documents"}}