{"id":"F2006B07410","name":"AD/TFE 731/4 - Transfer Bearing Support - Inspection","slug":"ad-tfe-731-4-transfer-bearing-support-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49640,"registerId":"commonwealth-F2006B07410-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TFE 731/4 - Transfer Bearing Support - Inspection","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  AlliedSignal (Garrett/AiResearch) Turbine Engines - TFE731 Series\n\n \n\nAD/TFE731/4  Transfer Bearing Support - Inspection              3/86 Applicability:              TFE 731-2-1C, -2-2B, -3-1E, -3-1G. Not modified to SB TFE 731-72-3020 standard. Document:               1. AiResearch SB TFE 731-72-2019; or\n\n2. FAA AD 75-07-10 Amdt 39-2189; or\n\n \n\n3. AD/AIR-T/31.\n\n \n\nCompliance: Within 25 hours time in service after 31 March 1977 and thereafter at intervals not exceeding 50 hours time in service until modified in accordance with AiResearch SB TFE 731-72-3020.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The supplied text defines a specific, limited scope: inspections of the transfer bearing support on named TFE731 models not modified to SB TFE 731-72-3020, at prescribed short intervals until that modification is fitted. The excerpt does not indicate any change to that scope from an earlier or alternate intent within the text provided."},"complexity_factors":["Narrow technical scope — applies only to four specific TFE731 engine models (Applicability)","Relies on external technical documents (AiResearch SB TFE 731-72-2019; FAA AD 75-07-10; AD/AIR-T/31) for inspection procedures (Document)","Time-based, short inspection intervals (initial 25 hours after 31 March 1977; then every ≤50 hours) increase operational scheduling complexity (Compliance)","Termination of recurring obligation depends on a specified modification standard (SB TFE 731-72-3020), requiring verification that modification has been performed (Compliance)","Date-specific compliance trigger (31 March 1977) makes the directive historical in origin and requires correct interpretation for legacy records (Compliance)"],"plain_english_summary":"- What this instrument does, mechanically\n  - This Airworthiness Directive (AD) requires recurring inspections of the transfer bearing support on specific AlliedSignal (Garrett/AiResearch) TFE731 turbofan engine models until those engines are modified to a specified service-bulletin standard. (See \"Applicability\" and \"Compliance\")\n\n  - Which engines are affected\n  - The AD applies to TFE 731-2-1C, -2-2B, -3-1E and -3-1G engines that have not been modified to the AiResearch service bulletin identified as SB TFE 731-72-3020. (See \"Applicability\")\n\n  - What operators must do and when\n  - Operators must inspect the transfer bearing support within 25 hours time in service after 31 March 1977 and then repeat that inspection at intervals not exceeding 50 hours time in service. These recurring inspections continue until the engine is modified in accordance with AiResearch SB TFE 731-72-3020, after which the inspection requirement ends. (See \"Compliance\")\n\n  - Documents that set out the inspection procedures\n  - Compliance can be achieved by following one of the referenced documents: AiResearch SB TFE 731-72-2019; FAA AD 75-07-10 Amdt 39-2189; or AD/AIR-T/31. The AD itself points to those documents for the detailed inspection instructions. (See \"Document\")\n\n  - Who issues the requirement and who pays\n  - The AD is published in the Commonwealth of Australia schedule of Airworthiness Directives under the Civil Aviation Safety Authority framework. Operators/owners of the affected engines are responsible for performing the inspections and for any modification to SB TFE 731-72-3020 that will stop the recurring inspections. (Header; \"Applicability\"; \"Compliance\")\n\n  - Why this matters (how the text frames the action)\n  - The text of the AD directs a mechanical inspection regimen for a specific engine component until a corrective modification is fitted. The AD does not include a hazard narrative in the supplied excerpt; it prescribes a preventative compliance regime (inspection intervals) and identifies a terminating action (modification to the SB standard). (Entire excerpt)\n\n  - Immediate incentives, costs and trade-offs implied by the text\n  - Who pays: operators/owners must bear the direct costs of performing the inspections at short intervals and of installing the SB TFE 731-72-3020 modification if they choose to stop the recurring inspections. (\"Compliance\")\n  - Incentives: continuing to operate without the SB modification imposes repeated inspection costs (every ≤50 hours). Installing the SB modification appears to be a one-off action that ends the recurring inspection obligation, creating a trade-off between an up-front modification cost and ongoing inspection costs. (\"Compliance\")\n  - Compliance burden: short, recurring intervals (25 hours then every ≤50 hours) create operational burden in scheduling maintenance and tracking time in service for affected engines. (\"Compliance\")\n  - Implementation risk and discretion: the AD specifies the terminating modification by reference to a named service bulletin; operators must determine and demonstrate that their engine has been modified to that SB standard to cease inspections. The AD relies on external documents for procedural detail (AiResearch SB, FAA AD, AD/AIR-T/31), so practical compliance requires access to and correct application of those documents. (\"Document\"; \"Compliance\")\n\n  - Effects on private enterprise and market choices (practical, source-grounded)\n  - The requirement directly affects firms that operate, maintain or overhaul the specified TFE731 engines: they must allocate labour and scheduling to meet short inspection intervals or invest in the modification. This changes operating costs and maintenance choices but does not, in the supplied text, change ownership rights, contractual freedoms or competitive rules. The AD sets a technical compliance obligation; how operators meet it (frequency of inspections vs. paying for the SB modification) is left to their commercial decision-making. (\"Applicability\"; \"Compliance\")\n\n  - Notes about the source text\n  - The AD excerpt supplies applicability, referenced documents and a precise inspection schedule with a terminating modification. The excerpt does not include a statement of the specific failure mode, incident history, or engineering rationale in this text; it relies on the referenced service bulletin(s) and FAA AD for procedural and technical detail. (Entire excerpt)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in specific engine models. It has not expanded beyond its original purpose of ensuring transfer bearing support integrity."},"complexity_factors":["Single, specific technical requirement (inspection of one component)","Limited applicability (4 specific engine models, unmodified only)","Simple compliance structure (initial deadline + recurring interval + termination condition)","Only 3 reference documents cited","No defined terms section, no cross-referencing to other legislation parts","Straightforward temporal logic (hours 'time in service' rather than calendar dates for ongoing compliance)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998. It mandates safety inspections for specific AlliedSignal (Garrett/AiResearch) TFE731 series turbine engines used in aircraft.\n\n**What it does:**\n- Requires operators to inspect the **transfer bearing support** — a critical engine component — on specific engine models (TFE 731-2-1C, -2-2B, -3-1E, and -3-1G) that haven't been upgraded to a newer standard (SB TFE 731-72-3020).\n\n**Who it affects:**\n- Aircraft operators and maintenance organisations using these specific engine models in Australian-registered aircraft.\n\n**What must be done:**\n- **First inspection:** Within 25 hours of flying time after 31 March 1977\n- **Ongoing inspections:** Every 50 hours of flying time thereafter\n- **Permanent fix:** Continue these inspections until the engine is modified according to Service Bulletin TFE 731-72-3020\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety orders. They typically address known defects or failure modes that could cause engine failure or accidents. This directive prevents catastrophic engine failure by ensuring a known problem area is regularly checked until a permanent modification is made."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tfe-731-4-transfer-bearing-support-inspection","history":"/api/acts/ad-tfe-731-4-transfer-bearing-support-inspection/history","analysis":"/api/acts/ad-tfe-731-4-transfer-bearing-support-inspection/analysis","conflicts":"/api/acts/ad-tfe-731-4-transfer-bearing-support-inspection/conflicts","importantCases":"/api/acts/ad-tfe-731-4-transfer-bearing-support-inspection/important-cases","documents":"/api/acts/ad-tfe-731-4-transfer-bearing-support-inspection/documents"}}