{"id":"F2006B07429","name":"AD/TPE 331/20 - Replacement of Reduction Gear Bearing Carrier Bolts, Installation of Lock Plate and Oil Transfer Tube Inspection","slug":"ad-tpe-331-20-replacement-of-reduction-gear-bearing-carrier-bolts-installation-of-lock-plate-and-oil","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49702,"registerId":"commonwealth-F2006B07429-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TPE 331/20 - Replacement of Reduction Gear Bearing Carrier Bolts, Installation of Lock Plate and Oil Transfer Tube 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 - TPE 331 Series\n\n \n\nAD/TPE 331/20  Replacement of Reduction Gear Bearing Carrier Bolts, Installation of Lock Plate and Oil Transfer\n\nTube Inspection\n\n\n3/86\n\n \n\nApplicability: TPE-331-1-101B, F, -1-151A, K, G. -2-201A, -5-251C, K. -6-251M/252M, -6-252B,\n\n-3U-303G, -3UW-303G, -3U-307G, which are listed in the reference document by their S/Nos. and those additional engines which had SB TPE-331-72-0064 incorporated.\n\n \n\nDocument: 1. AiResearch SB-331-72-0092, Rev. 5, or 2. FAA AD No. 76-16-01, or\n\n3. AD/AIR-T/25E.\n\n \n\nCompliance: In accordance with the reference document.\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":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused on a specific mechanical issue in a specific engine series. It has not expanded beyond its original purpose of addressing the reduction gear bearing carrier bolt and oil transfer tube issues identified in the referenced service bulletins."},"complexity_factors":["Very short document (approximately 250 words)","Only 4 defined elements: applicability list, three reference documents, and compliance requirement","No nested conditional logic or exceptions","Single compliance pathway ('in accordance with the reference document')","Technical content is externalized to referenced service bulletins and FAA ADs","Straightforward applicability by engine model and serial number"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) that mandates specific safety work on certain **AlliedSignal (Garrett/AiResearch) TPE 331 series turbine engines**.\n\n**What it requires:**\n- **Replacement** of bolts on the reduction gear bearing carrier (a component that holds bearings in place within the engine's gearbox)\n- **Installation** of a lock plate (a safety device that prevents bolts from loosening)\n- **Inspection** of the oil transfer tube (a pipe that moves lubricating oil through the engine)\n\n**Who it affects:**\n- Owners and operators of specific TPE 331 engine models, including variants like TPE-331-1-101B, -1-151A, -2-201A, -5-251C, and others listed by serial number\n- Also covers engines that previously had Service Bulletin TPE-331-72-0064 installed\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety orders. They are issued when authorities discover a condition that makes an aircraft or engine unsafe. This AD addresses potential mechanical failures that could lead to engine damage or in-flight shutdowns. Compliance is mandatory — operators must complete the specified work according to the referenced technical documents (AiResearch Service Bulletin or FAA AD) to keep their aircraft legally airworthy."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The AD applies to the listed TPE331 engine models and serial numbers and to engines that had SB TPE-331-72-0064 incorporated, as stated in the \"Applicability\" section. The directive delegates detailed requirements to the referenced service bulletin and airworthiness directives. The text gives no indication that this AD expands or contracts coverage relative to an earlier stated intent; it sets a targeted scope defined by referenced serial-number lists and prior incorporation of the specified service bulletin."},"complexity_factors":["Dependence on external reference documents (AiResearch SB, FAA AD, AD/AIR-T/25E) for procedural detail and compliance requirements.","Applicability tied to specific engine models and serial number lists that are contained in the referenced documents rather than fully reproduced in the AD text.","Need to determine whether Service Bulletin TPE-331-72-0064 was previously incorporated for a given engine.","Technical nature of required maintenance (bolt replacement, lock plate installation, oil transfer tube inspection) requiring skilled labour and parts sourcing.","Potential ambiguity about which referenced document to follow where multiple documents are listed and the AD text does not state precedence or differences.","Operational impacts (scheduling, spare parts, downtime) that vary by operator and are not quantified in the AD."],"plain_english_summary":"This airworthiness directive requires replacement of reduction-gear bearing carrier bolts, installation of a lock plate, and inspection of the oil transfer tube on specified AlliedSignal (Garrett/AiResearch) TPE331 engines identified by model and serial number (including engines with SB TPE-331-72-0064).  \n\nIt binds owners/operators and maintenance providers to comply by following the referenced service bulletin or foreign ADs; parts, labour, and downtime are the operators’ responsibility."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tpe-331-20-replacement-of-reduction-gear-bearing-carrier-bolts-installation-of-lock-plate-and-oil","history":"/api/acts/ad-tpe-331-20-replacement-of-reduction-gear-bearing-carrier-bolts-installation-of-lock-plate-and-oil/history","analysis":"/api/acts/ad-tpe-331-20-replacement-of-reduction-gear-bearing-carrier-bolts-installation-of-lock-plate-and-oil/analysis","conflicts":"/api/acts/ad-tpe-331-20-replacement-of-reduction-gear-bearing-carrier-bolts-installation-of-lock-plate-and-oil/conflicts","importantCases":"/api/acts/ad-tpe-331-20-replacement-of-reduction-gear-bearing-carrier-bolts-installation-of-lock-plate-and-oil/important-cases","documents":"/api/acts/ad-tpe-331-20-replacement-of-reduction-gear-bearing-carrier-bolts-installation-of-lock-plate-and-oil/documents"}}