{"id":"F2006B07458","name":"AD/TPE 331/47 - Third Stage Turbine Stator Assembly","slug":"ad-tpe-331-47-third-stage-turbine-stator-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49811,"registerId":"commonwealth-F2006B07458-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TPE 331/47 - Third Stage Turbine Stator Assembly","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 \\- TPE 331 Series\n\nAD/TPE 331/47 Third Stage Turbine Stator Assembly 1/94\n\nApplicability: TPE331-1, -2, -3, -5 and -6 series engines fitted with part number 868379-3 third stage turbine stator assemblies, as listed by serial number in Table 3 of Allied Signal Aerospace Service Bulletin TPE331-A72-0906.\n\nRequirement: Inspect the third stage turbine stator assembly in accordance with Allied Signal Aerospace Service Bulletin TPE331-A72-0906.\n\nCompliance: Effective 6 January 1994; as detailed in the Requirement document.\n\nBackground: This Directive requires the removal and inspection of certain third stage turbine stator assemblies. The requirement follows advice, certain P/N 868379-3 stators were assembled with the inner seal support sheet metal parts fabricated from an alloy which did not conform to specifications.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific manufacturing defect in a specific aircraft engine component. It has not expanded beyond its original purpose of mandating inspection of defective third stage turbine stator assemblies."},"complexity_factors":["Single, specific technical requirement (one inspection procedure)","Limited applicability (five engine series, one part number, specific serial numbers)","No nested exceptions or conditional logic","Short document (approximately 150 words)","Only one external reference (Service Bulletin TPE331-A72-0906)","Clear compliance date with no alternative methods or phased implementation"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it like a compulsory recall notice, but for aircraft engines rather than cars.\n\n**What it does:**\n- Orders owners and operators of specific **AlliedSignal TPE 331 series turbine engines** to inspect a particular part called the \"third stage turbine stator assembly\"\n- Only applies to engines with a specific part number (868379-3) and specific serial numbers listed in a technical document (Service Bulletin TPE331-A72-0906)\n\n**Why it matters:**\n- Some of these stator assemblies were built using the wrong type of metal alloy for the inner seal support\n- This manufacturing defect could potentially cause engine failure, which is obviously catastrophic in an aircraft\n- The directive makes inspection legally mandatory — operators cannot skip it\n\n**Who it affects:**\n- Anyone operating aircraft with TPE331-1, -2, -3, -5, or -6 series engines\n- Maintenance organisations servicing these engines\n- The compliance deadline was 6 January 1994\n\n**The bottom line:** If you own or operate one of these engines, you must follow the inspection procedure in the referenced service bulletin. It's not optional — it's a legal requirement under civil aviation law."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive’s scope is limited to engines fitted with part number 868379-3 stator assemblies whose serial numbers are listed in Table 3 of the OEM service bulletin. The directive implements the original stated intent—to identify and inspect stators assembled with a potentially non‑conforming alloy—by mandating removal and inspection per the service bulletin. There is no information in the provided text indicating an expansion or narrowing of that original intent."},"complexity_factors":["Narrow technical focus: single part (third stage turbine stator assembly, P/N 868379-3) and specific engine models (TPE331-1, -2, -3, -5, -6) (Applicability)","Dependence on external OEM document (Service Bulletin TPE331-A72-0906) for inspection procedure and serial-number list (Requirement)","Operational logistics: removal/inspection may cause aircraft/engine downtime and require parts and specialised maintenance facilities (Requirement; Compliance)","Serial-number specific applicability requires accurate record-checking by operators (Applicability)","Regulatory timing: fixed effective date imposes a scheduling deadline on affected operators (Compliance)"],"plain_english_summary":"What the directive changes mechanically\n\n- The Civil Aviation Safety Authority requires operators of certain AlliedSignal (Garrett/AiResearch) TPE331 turbine engines to remove and inspect a specific part: the third stage turbine stator assembly, part number 868379-3. The specific affected engines and serial numbers are listed in Table 3 of Allied Signal Aerospace Service Bulletin TPE331-A72-0906. (Applicability; Requirement)\n\nWho is affected and who decides\n\n- Affected parties: operators/owners of TPE331-1, -2, -3, -5 and -6 series engines that are fitted with P/N 868379-3 stator assemblies and whose serial numbers appear in the service bulletin table. (Applicability)\n- The Civil Aviation Safety Authority issued the directive and makes compliance mandatory; Allied Signal (the OEM) supplied the inspection procedure via Service Bulletin TPE331-A72-0906, which the directive requires be followed. (Requirement)\n\nWhy the directive exists (official rationale) and how that rationale maps to costs and incentives\n\n- Official rationale: certain P/N 868379-3 stators were assembled using an inner seal support sheet-metal alloy that did not meet specification. The directive requires removal and inspection to identify and address affected parts. (Background)\n\n- Practical implication: the regulator’s stated safety concern triggers a mandatory inspection program. Operators must check whether their engine stators are on the listed serial-number table and, if so, remove and inspect the stator per the OEM’s service bulletin. (Applicability; Requirement)\n\nCosts, burdens and trade-offs\n\n- Who pays: aircraft owners/operators pay direct costs for removal, inspection, any repairs or replacements, and associated labour. Maintenance providers will perform the work and receive the associated revenue. (Requirement)\n- Operational cost: engines or aircraft may be out of service while the stator is removed and inspected, creating downtime and potential scheduling or revenue impacts for operators. (Requirement; Compliance)\n- Parts and logistics: if inspection finds non-conforming or damaged parts, replacement parts will be needed; availability and lead times affect how long aircraft remain unavailable. (Requirement)\n- Administrative burden: operators must identify affected serial numbers (per the Service Bulletin’s Table 3), schedule maintenance, and document compliance by the effective date. (Applicability; Requirement; Compliance)\n\nIncentives and behaviour\n\n- Operators have an incentive to check serial numbers promptly and schedule inspections before operations are disrupted. Failure to comply risks regulatory enforcement. (Applicability; Requirement)\n- Maintenance providers and OEMs have commercial incentives to deliver inspection and repair services; the OEM’s service bulletin determines the required technical steps. (Requirement)\n\nImplementation risks and discretion\n\n- Technical expertise: the inspection and any necessary repairs require appropriate maintenance skills and facilities; smaller operators may need to outsource the work. (Requirement)\n- Enforcement discretion: the regulator sets the requirement and effective date; day-to-day judgment about scheduling, record-keeping and corrective action is exercised by operators and maintenance organisations following the service bulletin. (Requirement; Compliance)\n\nEffects on markets and private choice\n\n- Competition among maintenance providers may increase locally as operators seek available slots for inspection/repair. (Requirement)\n- Costs of compliance (labour, parts, downtime) are borne by operators, potentially affecting operating economics for aircraft using these engines. (Requirement; Compliance)\n\nNet mechanics in brief\n\n- If your engine is one of the listed TPE331 models and the stator assembly has a serial number shown in the OEM’s Table 3, you must remove and inspect that stator following Service Bulletin TPE331-A72-0906 by the effective date of 6 January 1994. The stated reason is possible non‑conforming sheet‑metal alloy in some assemblies. (Applicability; Requirement; Compliance; Background)\n\nSource citations: Applicability; Requirement; Compliance; Background."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tpe-331-47-third-stage-turbine-stator-assembly","history":"/api/acts/ad-tpe-331-47-third-stage-turbine-stator-assembly/history","analysis":"/api/acts/ad-tpe-331-47-third-stage-turbine-stator-assembly/analysis","conflicts":"/api/acts/ad-tpe-331-47-third-stage-turbine-stator-assembly/conflicts","importantCases":"/api/acts/ad-tpe-331-47-third-stage-turbine-stator-assembly/important-cases","documents":"/api/acts/ad-tpe-331-47-third-stage-turbine-stator-assembly/documents"}}