AD/PW4000/14 - Low Pressure Turbine Disks

The AD is framed around a small number of tightly specified technical and compliance concepts.

• Applicability by engine model and component identifier: The AD applies to Pratt & Whitney PW4164, PW4168 and PW4168A engines when they have a low pressure turbine stage 4 disk, P/N 51N404, with a serial number listed in the AD’s Table 1. The AD therefore combines an airframe/engine applicability (engine models) with an explicit parts‑level identification (part number plus serial number). This creates a narrow yet binary test of applicability , either the engine has an affected disk listed in Table 1 or it does not.

• Discrete serial‑number targeting: The AD lists a finite set of serial numbers (Table 1). The list is: CLDLC01142, CLDLC01143, CLDLC01144, CLDLC01145, CLDLC01146, CLDLC01148, CLDLC01149, CLDLC01150, CLDLC01151, CLDLC01152, CLDLC01181, CLDLC01182, CLDLC01183, CLDLC01185, CLDLC01186 and CLDLC01187. A serial‑number‑based approach means compliance is determined by parts traceability (logbooks, parts-tagging, inventory records).

• Two primary operative requirements: (1) Remove affected disks from service (Requirement 1). (2) Prohibit installation of any disk P/N 51N404 with a serial number listed in Table 1, and prohibit installation of disks removed under the AD except as allowed by paragraph (h) (Requirement 2). The AD thus establishes both a removal mandate and an ongoing installation prohibition.

• Compliance timing metric: The AD uses maintenance milestones and a life‑metric: “next piece‑part exposure after the effective date” or “within 7,500 cycles‑since‑new” for the removal (Requirement 1). The AD relies on the operator’s maintenance and life tracking systems (piece‑part exposure events and cycles‑since‑new records) as the trigger for mandatory action.

• Safety rationale and causal mechanism: The AD states the root cause as “improperly manufactured LPT stage 4 disks” and the hazard as “low‑cycle fatigue” leading to uncontained engine failure with potential aeroplane damage. The AD therefore links manufacturing defect to fatigue life reduction and containment risk.

• Referential interplay with other airworthiness directives: The AD explicitly refers to FAA AD 2007‑26‑20 (Amdt 39‑15322), signalling that this CASA AD sits alongside or follows action previously taken by another regulator. The AD notes this FAA AD in Note 2.

• Geographic and fleet scope language: Note 1 states these engines are installed on, but not limited to, Airbus A330‑200 and A330‑300 aeroplanes. The AD therefore targets engines that may be on certain airframes but does not limit the requirement to those airframes only.

Taken together, the AD’s main concepts create a compliance regime that is parts‑specific, traceability‑dependent, and time‑limited in its removal obligation but open‑ended in the installation prohibition. The operator’s ability to comply depends on accurate serial‑number records, the ability to identify the next piece‑part exposure, and inventory control processes to prevent installation after the effective date.

The primary addressees of the AD are the operators, maintainers and owners of the Pratt & Whitney PW4164, PW4168 and PW4168A turbofan engines that have a low pressure turbine stage 4 disk (P/N 51N404) with a serial number listed in Table 1. The AD’s applicability clause makes these engine models the point of entry; Note 1 clarifies that these engines are installed on, but not limited to, Airbus A330‑200 and A330‑300 aeroplanes, so owners and operators of those airframes are likely to be impacted but the AD is not strictly limited to those airframes.

Affected parties therefore include:

• Airline operators and aircraft owners who operate aeroplanes with the specified engines. These parties must identify whether an affected disk is installed and, if so, remove it in accordance with the AD’s timing requirement.

• Maintenance organisations and licensed engineers who perform engine maintenance and piece‑part exposures. They must check part numbers and serial numbers, track cycles‑since‑new, perform removal at the required milestone, and implement the installation prohibition at the point of maintenance activities.

• MROs, spare parts managers and supply‑chain custodians who hold inventories of disks P/N 51N404. The installation prohibition (Requirement 2) requires these actors to segregate, tag or otherwise ensure that affected serial‑numbered disks are not installed after the effective date.

• Lessors and technical records custodians who manage part traceability across asset transfers. Because the AD targets serial numbers, accurate maintenance records and traceability when engines or parts change hands matter for compliance.

• Regulatory and compliance functions within operators (airworthiness managers). They must schedule the removals to align with “next piece‑part exposure” or the 7,500 cycles‑since‑new deadline and ensure the organisation follows the installation prohibition.

The AD does not identify responsibilities for manufacturers, though the Background cites “improperly manufactured” disks as the root cause. The text also references FAA AD 2007‑26‑20, which may be relevant to operators with multinational fleets, but the supplied AD itself imposes obligations on operators and maintainers in the jurisdiction of the issuing authority (the Civil Aviation Safety Authority, via its delegate).

Because the AD is serial‑number specific, parties with engines of the same model that do not contain any serial numbers listed in Table 1 are not affected by the specific removal or installation prohibitions of this AD. Conversely, any party that cannot demonstrate that an affected serial number is not present will need to treat the engine/airframe as subject to the AD.

The AD places a small set of explicit duties on operators and maintainers. The text of the AD provides the operative obligations; it does not specify any affirmative rights for owners beyond the implied ability to comply or to seek any exception that might be contained in the AD’s paragraph (h) (the content of which is not included in the supplied extract).

Key duties (as expressed in the AD):

• Duty to remove affected parts (Requirement 1): “Remove from service any LPT stage 4 disk that has an S/N listed in Table 1 of this AD.” The duty binds the holder of the engine to take a physical removal action against a specified set of serialized disks.

• Timing duty for removal (compliance for Requirement 1): The removal must occur “at the next piece‑part exposure after the effective date of this AD or within 7,500 cycles‑since‑new, unless the actions have already been done.” This sets two alternative triggers: (a) a maintenance event that exposes the piece part next occurring after the effective date, or (b) a life‑limit threshold of 7,500 cycles‑since‑new. Operators must monitor both their maintenance schedule and life‑tracking metrics to determine the earlier required action.

• Installation prohibition (Requirement 2): “Do not install any disk, P/N 51N404, that has an S/N listed in Table 1 of this AD or any disk removed as specified in paragraph (f) of this AD except as allowed by paragraph (h) of this AD.” This establishes an ongoing prohibition from the AD’s effective date against installing the listed serial numbers and (subject to the missing paragraphs) against reinstalling disks removed under the AD, save for any exception in paragraph (h).

• Compliance timing for the installation prohibition: The AD states compliance for Requirement 2 is required “After the effective date of this AD.” Therefore no grace period for installation is given beyond the effective date.

Rights and implied options in the AD extract:

• No explicit rights or appeal mechanisms are included in the supplied extract. The AD does reference an exception mechanism in paragraph (h) by authorising limited reinstallations “except as allowed by paragraph (h) of this AD,” but the content of paragraph (h) is not supplied here. That suggests the full AD may contain an exception or repair/return‑to‑service pathway, but that cannot be confirmed from the provided text.

• The AD also references FAA AD 2007‑26‑20 in Note 2. Operators may therefore be expected to consult that FAA AD for related instructions or background; however, no explicit right to rely on FAA action is contained in the extract.

Practical implications of these duties as spelled out in the AD:

• The removal duty is operational and pointwise: the duty is triggered by discrete events (piece‑part exposure or cycles‑since‑new metric). Operators must therefore have systems that can identify when those triggers occur for each affected disk serial number.

• The installation prohibition is a process control obligation: it requires operators and maintenance providers to prevent installation at the time work is performed, which in turn requires accurate inventory controls and parts tagging.

• The extract does not specify any documentation, reporting or approval processes for compliance, nor does it specify remedies or appeal processes within the extract; any such mechanisms (for example, requests for alternative methods of compliance) would need to be located in the full AD or the regulator’s wider rules, which are not supplied here.

The supplied AD extract does not set out any specific penalties, civil sanctions, criminal liability or enforcement procedures. The document records that it “becomes effective on 22 October 2009” and is signed by a Delegate of the Civil Aviation Safety Authority, which identifies the issuing authority but does not enumerate enforcement mechanisms or financial penalties in the text provided.

What the extract does indicate, within its limits:

• The instrument is an Airworthiness Directive issued under the authority of the Civil Aviation Safety Authority (signature: James Coyne, Delegate of the Civil Aviation Safety Authority). This identifies the issuing regulator and signals that the AD is an official regulatory instrument, but the extract does not include the enabling statute, penalty clauses or enforcement protocols.

• No enforcement timeline or inspection regime is described in the supplied material. The AD sets compliance timing for the removal and installation duties but does not describe how compliance will be monitored, audited, or enforced.

• No prescribed forms of remedy or corrective action are specified beyond removal from service and prohibition of installation. The AD does not state whether removed disks must be scrapped, returned to the manufacturer, quarantined, or otherwise processed; nor does it state any requirement to notify the regulator upon compliance.

• Penalty exposure is not articulated in this text. The absence of express penalties in the extract does not necessarily mean there are none under the broader legal framework; it means they are not stated in the extract supplied. Operators should not infer from this extract that non‑compliance carries no enforcement consequence; the presence of a CASA delegate signature indicates a regulatory origin and, in practice, AD non‑compliance will typically be of regulatory concern. The AD itself, however, does not specify fines, certificate actions or criminal sanctions in the supplied pages.

• The AD refers to another regulator’s AD (FAA AD 2007‑26‑20). That cross‑reference may inform international oversight or mutual awareness but the extract does not identify cross‑jurisdictional enforcement mechanisms.

Because the extract lacks an explicit enforcement/penalty section, affected parties that require certainty on enforcement and penalties will need to consult the full official AD text, the CASA regulatory framework, or legal counsel to determine the legal consequences of non‑compliance and the enforcement mechanisms CASA would employ. The supplied AD text only establishes duties and timing; it does not itself prescribe enforcement processes or penalties in the portion provided.

The AD as supplied contains a limited formal interaction with other regulatory instruments, but the extract does explicitly reference another regulator’s AD and situates itself within the engine/airframe regulatory space.

Explicit cross‑reference:

• Note 2 states: “FAA AD 2007‑26‑20 Amdt 39‑15322 dated 20 December 2007 refers.” This is an explicit cross‑reference to a United States Federal Aviation Administration Airworthiness Directive. The reference indicates that CASA’s AD draws on or aligns with action previously taken by another civil aviation regulator. The supplied text does not elaborate whether the CASA AD imposes identical, narrower or broader requirements than the FAA AD; it simply records the existence of the FAA AD as relevant information.

Implications within the supplied text:

• The AD’s applicability clause (PW4164, PW4168, PW4168A with P/N 51N404 disks of listed S/Ns) and Note 1 (engines installed on, but not limited to, Airbus A330‑200 and A330‑300) indicate the AD is technical and part‑specific. Its interaction with other laws would therefore be operational: it modifies or augments maintenance and airworthiness obligations under the regulatory regime that binds operators and maintainers in the jurisdiction where this AD is applicable.

• The AD does not detail how it interacts with contractual obligations (for example, manufacturer warranties, supply agreements, lease contracts) in the supplied extract. Because it mandates removal of specific serialized parts by a deadline, the AD is likely to intersect with commercial contracts over parts ownership and warranty claims, but those commercial interactions are not governed by the AD text supplied here.

• The extract does not state how the AD affects maintenance approvals, continuing airworthiness records, or type‑certificate conditions in statutory terms. It does not identify other statutes, regulations, or administrative instruments that are amended or superseded. In the absence of those statements, the AD should be read as an independent directive that imposes obligations on operators in addition to any existing regulatory duties.

• The AD’s serial‑number specificity means it interacts practically with maintenance‑record retention and parts‑traceability requirements under airworthiness regulations: operators will need to reconcile their records with the Table 1 list. The AD’s timing trigger “next piece‑part exposure” interacts operationally with maintenance scheduling rules, but those rules are not quoted in the extract.

• International fleets and multinational operators may need to consider both the CASA AD and FAA AD referenced. The extract’s cross‑reference to the FAA AD signals that operators with operations in multiple jurisdictions should check both instruments to ensure coordinated compliance, as the two regulators may have related but distinct requirements.

Because the supplied extract is limited to the AD’s operative requirements and a brief background and does not quote broader statutory provisions, any definitive statement about legal hierarchy, preemption, or statutory amendments cannot be made from this extract alone. The only explicit inter‑instrument relationship in the text is the reference to FAA AD 2007‑26‑20.

The supplied extract contains explicit metadata and a single cross‑reference that together form the limited amendment history and provenance available in the document.

• AD identification and date: The AD is identified as AD/PW4000/14 and carries the date 11/2009 in the heading. The printed effectivity statement declares that “This Airworthiness Directive becomes effective on 22 October 2009.” The document is signed and dated 2 September 2009 by James Coyne, Delegate of the Civil Aviation Safety Authority. Those dates give a short timeline: signature on 2 September 2009, effective date 22 October 2009, with the AD nominally recorded as 11/2009.

• Cross‑referenced earlier action: Note 2 states that FAA AD 2007‑26‑20, Amendment 39‑15322, dated 20 December 2007, “refers.” That indicates prior regulatory action on the same technical issue by the FAA in 2007. The inclusion of that reference in the AD’s text serves as a historical pointer; the CASA AD of 2009 follows the FAA’s 2007 action, at least chronologically.

• No internal amendments included in extract: The extract supplied does not include any internal amendment trace (for example, “as amended by X”) or any record of subsequent changes to AD/PW4000/14. The document as supplied appears to be the AD as issued in late 2009; no later corrigenda, revisions or supersessions are included in the provided pages.

• No legislative or regulatory amendment clauses: The AD text provided does not contain explicit amendment clauses (for example, “This AD supersedes AD X”) or references to earlier CASA ADs. The only cross‑jurisdiction link is to the FAA AD referenced above.

• Signature and delegated authority: The AD is signed by a CASA delegate, which indicates the AD was issued under delegated regulatory authority. The extract does not include the enabling instrument, the specific delegation order, or any record of amendment to the directive after issue.

Users requiring a comprehensive amendment history (for example, subsequent revisions, corrections, supersessions or revocations) will need to consult the official CASA AD database or the complete AD document and related notices. The supplied extract provides the issuance date, effective date, AD identifier and a single cross‑reference to the FAA AD as the only amendment/historical pointers available in the text provided.

The supplied AD extract contains no information on litigation, appeals, judicial review, or administrative challenges. There are no references in the text to prior or ongoing court cases, tribunal decisions, or dispute resolution regarding this AD or the specified parts.

Consequently, from the document provided:

• There is no litigation history recorded within the text. The AD does not recount any legal proceedings or case law related to the subject matter.

• The document lists the issuing authority (the Civil Aviation Safety Authority, via its delegate) and provides technical and compliance requirements, but it does not include any narrative or footnote regarding legal challenges.

• Any judicial or administrative proceedings that may have related to this AD (for example, challenges to its validity, enforcement actions for non‑compliance, or disputes over the scope of the parts list) are not disclosed in the supplied extract. To determine whether this AD has been the subject of litigation or appeals, one would need to consult court records, CASA administrative records, or legal databases; that material is not part of the supplied text.

In the absence of any litigation material in the extract, analysts and practitioners should treat the AD as a technical regulatory instrument whose legal contestation history is not reported in the provided document. Parties seeking information about disputes, enforcement actions or judicial review must obtain sources beyond the AD extract supplied here.

The AD contains a number of technical and documentary features that create compliance traps or areas of uncertainty that deserve attention, given the text supplied.

• Serial‑number specificity requires immaculate traceability: The AD’s applicability depends on identifying whether an installed LPT stage 4 disk has one of the serial numbers listed in Table 1. That places the operational burden on an operator’s parts‑traceability systems (logbooks, tags, inventory records). Mistakes in serial‑number records, lost tags or ambiguous documentation can lead to inadvertent non‑compliance with either the removal duty or the installation prohibition.

• “Next piece‑part exposure” as a trigger: The phrase “at the next piece‑part exposure after the effective date” is a maintenance scheduling trigger. Operators must correctly understand what constitutes a “piece‑part exposure” for this engine and disk, and must schedule to perform the removal at that event if it occurs before the 7,500 cycles‑since‑new threshold. Failure to correctly recognise or record piece‑part exposures can create timing disputes over compliance.

• Dual compliance metric (piece‑part exposure or cycles‑since‑new): The AD gives two alternative triggers (piece‑part exposure or 7,500 cycles‑since‑new). Operators must monitor both metrics and apply the earlier required action correctly. Misapplication (for example, failing to track cycles‑since‑new accurately) could result in missed deadlines.

• Installation prohibition includes removed disks subject to paragraph (f) and exception in paragraph (h): Requirement 2 bars the installation of any disk P/N 51N404 with a serial number listed in Table 1 and “any disk removed as specified in paragraph (f) of this AD except as allowed by paragraph (h) of this AD.” The supplied extract does not include the content of paragraphs (f) or (h). Therefore, there is an important missing cross‑reference: the status of disks removed under paragraph (f) and any permitted reinstallation under paragraph (h) cannot be determined from this extract. That absence is a critical operational “gotcha”: operators cannot rely on the supplied text alone to know whether any rework or conditional return‑to‑service process exists.

• Scope phrase “installed on, but not limited to, Airbus A330‑200 and A330‑300”: Note 1 indicates these engines are installed on those Airbus types but “not limited to” them. This phrasing may lead to confusion: operators of other airframes need to check whether the specified engines are installed on their types. The AD is not constrained to A330‑200/300 airframes, so operators of other fleets must check for applicability.

• Inventory and spare pool risk: The AD’s installation prohibition is effective “After the effective date of this AD.” Any spare disk inventory, vendor stock, or third‑party spares pools containing P/N 51N404 with listed serial numbers must be screened. If parts have migrated between operators or across borders, operators may unknowingly hold affected spares. The AD does not provide procedures for disposition of such spares in the supplied extract.

• Lack of explicit disposition instructions: The AD mandates removal but does not prescribe disposition steps (e.g., scrapping, return‑to‑manufacturer, quarantine) in the supplied extract. The absence of explicit instructions creates ambiguity about treatment of removed parts unless the remainder of the AD (not supplied) or other guidance is consulted.

• Reference to FAA AD without full harmonisation details: The AD refers to FAA AD 2007‑26‑20, but the supplied extract does not state whether CASA’s requirements mirror, extend, or differ from the FAA’s. Operators with international operations should not assume automatic equivalence; the absence of harmonisation text in this extract is a potential compliance pitfall.

• No stated enforcement or reporting procedure in the extract: The AD does not spell out reporting obligations or how to demonstrate compliance to the regulator in the supplied pages. That creates an administrative risk for operators who may need to document compliance for airworthiness records or audits. Practically, operators should preserve removal records and maintenance entries even though the AD extract does not mandate a particular format.

Taken together, these gotchas centre on recordkeeping, interpretation of maintenance triggers, missing cross‑referenced paragraphs, spare‑parts management, and uncertainty about post‑removal disposition and exception pathways. The AD extract supplies the core removal and installation prohibitions but leaves several operationally important details unexpressed in the pages provided.

The AD itself provides the immediate, operative steps required for compliance. Below is a concise, source‑grounded checklist and process based strictly on the text supplied, together with practical recordkeeping steps that follow logically from the AD’s form and triggers.

1. Identify affected engines and parts.

   • Check all Pratt & Whitney PW4164, PW4168 and PW4168A engines in your fleet for LPT stage 4 disks P/N 51N404.
   • For each disk, confirm the serial number and compare it to Table 1 in the AD. Table 1 lists: CLDLC01142, CLDLC01143, CLDLC01144, CLDLC01145, CLDLC01146, CLDLC01148, CLDLC01149, CLDLC01150, CLDLC01151, CLDLC01152, CLDLC01181, CLDLC01182, CLDLC01183, CLDLC01185, CLDLC01186 and CLDLC01187.

2. Schedule removal as required (Requirement 1).

   • If an affected serial number is installed, remove that disk from service at the next piece‑part exposure after the AD’s effective date (22 October 2009) or within 7,500 cycles‑since‑new, whichever trigger applies and unless the actions have already been done. The AD’s text sets those two alternate triggers; the operator must determine which applies based on its maintenance events and life records.

3. Prevent installation after the effective date (Requirement 2).

   • From the AD effective date forward, do not install any disk P/N 51N404 that has a serial number in Table 1.
   • Do not (re)install any disk removed under the AD as specified by the cross‑reference to paragraph (f), except as may be permitted by paragraph (h). Because the extract supplied does not contain paragraphs (f) or (h), consult the full AD for the exact conditions concerning removed parts and any authorised exceptions in paragraph (h).

4. Inventory and spare parts control.

   • Immediately screen spare parts inventories and supply pools for P/N 51N404 with the listed serial numbers and segregate any affected parts to prevent inadvertent installation.
   • Update inventory records and parts tags to reflect the AD status and installation prohibition.

5. Maintenance and technical records.

   • Record removal actions in the engine and airframe maintenance logbooks, specifying the serial number removed, the date, the reason (reference the AD), and the compliance method (next piece‑part exposure or cycles‑since‑new).
   • Record the disposition of removed parts. The AD extract does not prescribe disposal or return procedures; document your chosen disposition and, if necessary, retain the part in quarantine pending instructions from manufacturer or regulator.

6. Consult full AD text and related instruments.

   • The supplied extract references paragraphs (f) and (h) and FAA AD 2007‑26‑20. Obtain and review the complete CASA AD text and the referenced FAA AD to determine whether there are permitted repair, rework, return‑to‑service, or reporting procedures not included in this extract.
   • Because Note 1 indicates the engines are installed on, but not limited to, Airbus A330‑200 and A330‑300 aeroplanes, operators with other airframes should confirm engine installations and applicability for their fleet.

7. Operational scheduling.

   • Where the “next piece‑part exposure” trigger will occur after the 7,500 cycles‑since‑new threshold, the cycles count may force earlier removal. Track cycles‑since‑new closely and reconcile with upcoming maintenance events to ensure removal within the AD’s deadlines.

8. Consider communications.

   • Communicate within the organisation (maintenance control, procurement, flight operations) about affected serial numbers, restrictions on installation, and steps for quarantining parts to prevent accidental installation during line maintenance or overhaul.

9. Retain evidence of compliance.

   • Preserve maintenance entries, parts‑tagging photographs, quarantine records, and any correspondence with the regulator or manufacturer that document the removal and installation prohibition in case of future audit.

10. Seek clarification where needed.

    • Because the extract does not include paragraphs (f) and (h) or any explicit enforcement language, if an operator requires certainty about permitted exceptions, disposition, or reporting, they should obtain the full AD text and, if necessary, seek formal clarification from CASA or legal/technical counsel.

These steps reflect the AD’s operative requirements as supplied: removal of specified serial‑numbered disks at a defined maintenance or life milestone, and a prohibition against installation of listed serial numbers (and of removed disks unless an exception applies). The critical compliance dependencies under the AD are accurate serial‑number records, maintenance event scheduling to capture piece‑part exposures, cycles‑since‑new tracking, and inventory control measures to prevent installation of prohibited parts.