{"id":"F2006B07467","name":"AD/TPE 331/56 - Second Stage Turbine Stator","slug":"ad-tpe-331-56-second-stage-turbine-stator","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49844,"registerId":"commonwealth-F2006B07467-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.","sortOrder":0},{"sectionNumber":"AD/TPE 331/56 Second Stage Turbine Stato","sectionType":"part","heading":"AD/TPE 331/56 Second Stage Turbine Stator 12/2001","content":"# AD/TPE 331/56 Second Stage Turbine Stator 12/2001\n\nApplicability: TPE331-1, \\-2, \\-3, \\-5 and \\-6 series engines incorporating a second stage turbine stator assembly part number (P/N) 894528-1, -2, -3, -5, -6, -10 and -11.\n\nNote 1: Stator assemblies P/N 894528-10 and 894528-11 which have been flow tested and reidentified in accordance with Honeywell Service Bulletin TPE331-72-2085RWK are no longer -10 or -11 stators and are therefore not applicable.\n\nRequirement: Replace second stage turbine stator assembly part number (P/N) 894528-1, \\-2, \\-3, \\-5,\n\n\\-6, \\-10 and \\-11 in accordance with Honeywell Service Bulletin TPE331-A72-2082.\n\nNote 2: The FAA has advised they are working to issue an Airworthiness Directive mandating this requirement.\n\nCompliance: At next access to the second stage turbine stator assembly, but no later than 3100 engine hours in service since last turbine section inspection.\n\nThis Airworthiness Directive becomes effective on 28 November 2001.\n\nBackground: This Directive has been issued to address reports of six uncontained failures of the second stage turbine wheels in TPE331-1, -2, -3, -5 and -6 series engines incorporating a second stage turbine stator assembly part number (P/N) 894528-1, \\-2,\n\n\\-3, \\-5, \\-6, \\-10 and \\-11. The uncontained turbine failures were initiated by fatigue damage to the second stage turbine stator inner seal support, resulting in turbine wheel rub and uncontained rotor failure.\n\n![Signature of Neville Probert Delegate of the Civil Aviation Safety Authority](image.003.png)  \n\nNeville Probert\n\nDelegate of the Civil Aviation Safety Authority 23 October 2001\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 7 November 2001.","sortOrder":1}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific mechanical failure mode in specific engine models. The single exemption for modified stators is a standard safety carve-out, not scope creep."},"complexity_factors":["Single, specific mechanical action required (replacement of one component type)","Clear applicability section with explicit part number listing","Straightforward compliance deadline (next access OR 3,100 hours)","Only one defined term of note ('in service' hours)","No nested exceptions or conditional logic beyond the single Note 1 exemption","No cross-references to other legislation — only references to manufacturer service bulletins","Total length under 400 words"],"plain_english_summary":"This AD mandates replacement of specific second-stage turbine stator assemblies (PNs 894528-1, -2, -3, -5, -6, -10, -11) in certain Honeywell TPE331-1/2/3/5/6 series engines after repeated catastrophic uncontained failures caused by fatigue cracking. It affects owners/operators of engines with those stators; replacement is required at next stator access or by 3,100 engine hours since the last turbine inspection, unless the stator was previously modified and reidentified per Honeywell SB TPE331-72-2085RWK."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD is narrowly targeted to correct a specific unsafe condition (fatigue damage to the second stage turbine stator inner seal support) by mandating replacement of identified stator assemblies. It does not broaden regulatory scope beyond that safety remedy: the action, affected parts, timing, and method are all limited to addressing the reported uncontained failures. There is no evidence in the text that the AD has grown beyond its original corrective purpose."},"complexity_factors":["Short, single-action directive (replace specified parts)","Limited number of affected engine models (5 model variants listed)","Seven listed part numbers with two P/Ns excluded when reidentified (Note 1)","Compliance condition with a single timing rule: ‘next access’ but capped at 3,100 engine hours","Dependence on external technical documents (Honeywell Service Bulletin TPE331-A72-2082 and TPE331-72-2085RWK)","One safety root-cause (fatigue of stator inner seal support) described in Background"],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- This is an Airworthiness Directive (AD) that requires certain Pratt & Whitney (TPE331) turboprop engines to have their second stage turbine stator assemblies replaced. (See: Requirement.)\n- It applies to TPE331-1, -2, -3, -5 and -6 series engines that incorporate second stage turbine stator assemblies with part numbers (P/N) 894528-1, -2, -3, -5, -6, -10 and -11. (See: Applicability.)\n- Engines with P/N 894528-10 and -11 that have been flow tested and reidentified under Honeywell Service Bulletin TPE331-72-2085RWK are excluded, because they are reidentified and therefore no longer considered -10 or -11 stators. (See: Note 1.)\n- The mandated action is to replace the listed second stage turbine stator assemblies in accordance with Honeywell Service Bulletin TPE331-A72-2082. (See: Requirement.)\n- Timing: replacement must occur at the next time the second stage turbine stator assembly is accessed for maintenance, but no later than 3,100 engine hours since the last turbine section inspection. (See: Compliance.)\n\n**Who this affects**\n\n- Aircraft operators and maintenance organisations that operate or service the specified TPE331 engine models with the listed stator part numbers. They must schedule replacement work and comply with the Honeywell service instructions.\n- Maintenance providers (MROs) who will carry out the replacement and potentially supply the replacement stator assemblies or coordinate with parts suppliers.\n- The engine OEM (Honeywell/Pratt & Whitney) and parts suppliers, who may see demand for replacement parts and will be the source of technical instructions (service bulletin).\n\n**Why the AD was issued (official rationale) and how the rule addresses it**\n\n- The AD was issued because of six reported uncontained failures of the second stage turbine wheels on engines that used these stator assemblies. The failures were traced to fatigue damage to the stator inner seal support, which led to rotor rub and uncontained rotor failure. (See: Background.)\n- The AD’s corrective measure is mandatory replacement of the affected stator assemblies following the manufacturer’s service bulletin. The intent (as stated) is to remove assemblies that may be susceptible to the initiating fatigue damage and thereby reduce the risk of uncontained rotor failures. (See: Requirement; Note 2 referring to FAA action.)\n\n**Practical mechanics, incentives and compliance effects**\n\n- Who pays: aircraft operators bear the direct cost of parts and labour to replace the stator assemblies, and any downtime while the work is performed. Operators may also incur logistics costs to obtain parts and schedule inspections earlier than planned. (See: Requirement; Compliance.)\n- Who decides and how: the CASA delegate has mandated the action and set the timing; the detailed method of replacement is governed by Honeywell’s Service Bulletin TPE331-A72-2082, which operators and MROs must follow. This centralises technical direction with the OEM’s published instructions. (See: Preamble; Requirement.)\n- Behaviour change required: operators must track affected engines and stator P/Ns, plan replacement at the next access or before 3,100 engine hours, and follow the specified service bulletin. This may accelerate maintenance schedules and shift workload to MROs.\n- Market effects: demand for compliant replacement stators and MRO labour will increase in the short term. The AD does not prescribe a specific replacement part beyond following the service bulletin, so suppliers that meet the bulletin’s requirements can supply parts. The AD therefore imposes a compliance cost but does not explicitly restrict supplier competition beyond technical conformity requirements.\n\n**Trade-offs, risks and implementation considerations**\n\n- Cost vs safety: the AD imposes parts and labour costs (and associated aircraft downtime) to reduce the probability of a rare but high-consequence hazard (uncontained rotor failure). The AD forces internalisation of that safety risk by operators through mandatory replacement. (See: Background; Requirement; Compliance.)\n- Timing trade-off: the compliance window is conditional (“at next access… but no later than 3,100 engine hours”), which lets operators defer replacement until the stator is next accessed but caps deferral. This reduces immediate downtime for some operators but still ensures the corrective action within a defined exposure period. (See: Compliance.)\n- Implementation risk: operators must correctly identify P/Ns and any reidentified parts (Note 1). Misidentification could lead to unnecessary replacements or failure to replace an affected unit. Clear maintenance record-keeping and parts-traceability are required. (See: Applicability; Note 1.)\n- Administrative and discretion risks: the AD delegates technical detail to the manufacturer’s service bulletin, so the CASA delegate enforces compliance while the manufacturer supplies the technical remedy. That split means regulatory compliance hinges on access to, and correct application of, the service bulletin.\n\n**Other notable points**\n\n- The AD cross-references Honeywell service bulletins for the exact replacement procedure; operators must obtain and follow those bulletins. (See: Requirement.)\n- The AD notes the FAA was working to issue a corresponding directive, which indicates parallel regulatory concern but does not change the Australian compliance requirement in this instrument (Note 2).\n\n(Section citations in parentheses refer to the corresponding parts of the AD: Applicability; Requirement; Compliance; Background; Notes.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-tpe-331-56-second-stage-turbine-stator","history":"/api/acts/ad-tpe-331-56-second-stage-turbine-stator/history","analysis":"/api/acts/ad-tpe-331-56-second-stage-turbine-stator/analysis","conflicts":"/api/acts/ad-tpe-331-56-second-stage-turbine-stator/conflicts","importantCases":"/api/acts/ad-tpe-331-56-second-stage-turbine-stator/important-cases","documents":"/api/acts/ad-tpe-331-56-second-stage-turbine-stator/documents"}}