AD/PW4000/15 - 14th and 15th Stage Rubstrips

The AD rests on a small set of tightly defined technical concepts and thresholds. The principal technical object is the HPC inner rear case assembly and its rear hook, the wear of which affects stage clearances and can lead to high pressure compressor (HPC) surge events during takeoff. The AD targets "14th and 15th stage rubstrips located on the 13th and 14th stage stator set" and mandates borescope inspections to detect wear that has cut through to the parent material of the stator.

Key operational metrics used to trigger different actions are defined in the AD text and tables:

• CSN: cycles-since-new; CSR: cycles-since-refurbishment; CIS: cycles-in-service. Table 1 uses CSN/CSR to determine when the initial borescope inspection must occur. Table 2 and Table 3 use CIS and thresholds expressed in "CIS" for removal or reinspection scheduling.
• Wear thresholds are given as circumferential lengths measured in inches where the rubstrip has worn through to parent material: 1.0 inch on the 14th stage, 2.0 inches on the 15th stage. Those thresholds determine immediate removal within 250 CIS if met, otherwise reinspection intervals apply (Table 2).
• Reinspection intervals after an initial inspection depend on the presence and extent of wear: 300 CIS for limited wear; 600 CIS where no wear through to parent material is found (Table 2).

The AD cross-references manufacturer service information for the inspection method. Specifically, it requires borescope inspection "in accordance with paragraphs 1.A. through 1.I of the Accomplishment Instructions" of PW ASB PW4G-100-A72-170 Rev 3 (31 January 2003). The operator’s inspection technique, disassembly limits, and detailed acceptance criteria therefore are anchored to that ASB text. The AD also recognises earlier ASB revisions, and accepts later ASB revisions only if those later revisions are FAA-approved as an AMOC to FAA AD 2003-09-02.

The AD treats "serviceable engine" as an operationally significant legal status. The AD provides a three-part definition: zero CSN HPC, an engine covered by the terminating action, or an engine inspected and on the 600 CIS reinspection interval. That definition constrains the options available to an operator when an engine must be removed and replaced; it sets the practical market for replacement engines (for example engines with low CSN, or engines already modified under the terminating action).

The terminating action is a hardware modification: replacement of the HPC inner rear case assembly with an assembly containing a Haynes 242 rear hook, or assemblies modified by two specified PW service bulletins PW4G-100-72-159 and PW4G-100-72-187, or Chromalloy Repair Procedure 00-CFL-039-0. The AD states that such replacement "constitutes terminating action for the repetitive engine borescope inspections of this AD."

Finally, the AD explicitly imports FAA material and identifies FAA AD 2003-09-02 (Amdt 39-13131 dated 21 April 2003) as relevant. The AD states that CASA reviewed State of Design ADs and determined this AD "may be applicable to Australian aircraft." The AD therefore operates in a standard international safety-assurance framework where State of Design directives and FAA AMOCs are treated as relevant sources for compliance.

The AD affects a narrowly defined and identifiable group of operators and maintenance providers. It applies only to Pratt & Whitney PW4164, PW4168 and PW4168A turbofan engines that have HPC inner case assembly part number 53H272-01 installed, and only for serial numbers P733301 through P733500 (see Applicability). The AD notes that these engines are "installed on, but not limited to Airbus Industrie A330 aeroplanes," which signals that any operator flying airframes fitted with these engines must comply, regardless of aircraft type.

Primary parties who must act are aircraft operators and their maintenance organisations. Operators are required to schedule and carry out borescope inspections in line with Requirement 1 and Table 1, to interpret inspection results in line with Table 2 and to comply with coordination and replacement measures in Requirement 3 and Table 3 where two affected engines are installed on the same aeroplane. Maintenance organisations performing the borescope inspections must follow "paragraphs 1.A. through 1.I of the Accomplishment Instructions" in PW ASB PW4G-100-A72-170 Rev 3; that ties the procedural responsibilities to the manufacturer’s specified inspection technique.

Parts suppliers and component repair organisations are indirectly affected because the AD introduces potential demand for replacement HPC inner rear case assemblies, assemblies modified or replaced under specified SBs, and Chromalloy repairs. The AD explicitly lists the SB numbers and a repair procedure that will qualify an engine as "covered by the Terminating Action" (PW SB No. PW4G-100-72-159, PW SB No. PW4G-100-72-187, Chromalloy Repair Procedure 00-CFL-039-0). Suppliers of Haynes 242-reinforced assemblies therefore may see concentrated demand from operators electing the terminating action.

Regulatory decision-makers are set out in the AD text but remain implicit as to enforcement mechanics. The AD is issued by the Civil Aviation Safety Authority, signed by David Punshon as delegate. The AD becomes effective 14 August 2010 and CASA's background note records that CASA determined the AD may be applicable to Australian aircraft. The AD also references FAA material and accepts FAA-approved AMOCs for later ASB revisions, indicating that FAA approvals will determine whether a later ASB revision is acceptable to CASA.

Passengers and the public are indirect stakeholders: the AD’s stated safety purpose is to "prevent engine power loss during takeoff due to HPC surge." That is a claimed public safety benefit. The AD does not allocate costs between parties; however operators and maintenance organisations will bear the direct costs of inspections, reinspections, engine removal, replacement and any termination modifications.

Who pays, explicitly: the AD requires operators to perform the work. The AD contains compliance instructions rather than funding mechanisms, so the financial and operational burden is borne by the operator or by any maintenance/lease agreements the operator has with third parties. The AD itself does not contain financial cost estimates.

Duties

• Identify affected engines. The operator must determine whether their fleet includes any PW4164, PW4168 or PW4168A engines with HPC inner rear case assembly P/N 53H272-01 and serial numbers in the range P733301 through P733500 (Applicability).

• Perform initial borescope inspection. Requirement 1 mandates that, unless already accomplished, operators must "borescope-inspect in accordance with paragraphs 1.A. through 1.I of the Accomplishment Instructions" of PW ASB PW4G-100-A72-170 Rev 3, and follow the initial inspection timing set out in Table 1 (Requirement 1, Table 1). Table 1 sets different initial timelines depending on CSN/CSR on the effective date.

• Implement follow-up actions. Requirement 2 requires performing the action specified in Table 2 once inspection results are known. Table 2 sets the immediate operational consequences: removal within 250 CIS for specified wear thresholds, or reinspection at specified intervals for lesser or no wear.

• Coordinate inspections between engines on the same airplane. Requirement 3 and Table 3 require a second-engine inspection within 10 CIS of the first engine’s inspection where two affected engines are installed, and set the action rules where both engines show wear patterns listed in Table 2. If both engines exhibit specified wear, remove either engine within 25 CIS of the second inspection and replace it with a serviceable engine (Requirement 3, Table 3).

• Record and maintain compliance. While the AD text provided does not specify recordkeeping detail, the inspection and removal timeframes create de facto documentation demands for operators: CSN, CSR and CIS counts must be tracked to trigger actions at the correct cycle counts.

• Apply terminating action if chosen. If an operator elects the terminating action, they must replace the HPC inner rear case assembly with one containing a Haynes 242 rear hook, or with an assembly modified or replaced by the specified SBs or Chromalloy procedure (Terminating Action clause).

Rights and options

• Use of AMOCs for later ASB revisions. The AD expressly permits compliance using later revisions of PW ASB PW4G-100-A72-170 if those later revisions are "approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2003-09-02." That provides a defined route to adopt updated manufacturer procedures subject to FAA approval.

• Continue to rely on prior inspections performed under earlier ASB revisions only as a transitional matter. Engines borescope-inspected before the effective date under PW ASB Rev 1 or Rev 2 "must follow Requirements 1 through 3 of this AD, after the effective date of this AD." That narrows but does not entirely eliminate reliance on earlier work: operators must still meet the AD’s formal inspection and scheduling regime from the effective date forward.

• Elect to perform the terminating action. Operators may choose to replace the HPC inner rear case assembly with the Haynes 242 rear hook variant, or assemblies modified by the listed SBs or Chromalloy repair, which the AD treats as terminating action for the repetitive inspections. That is a durable compliance option and changes the operator’s duty profile by eliminating the repetitive borescope cycle for that engine.

Operational specifics to observe

• Measurement thresholds are precise: 1.0 inch circumferential wear through to parent material on the 14th stage triggers removal within 250 CIS; 2.0 inch circumferential wear through parent material on the 15th stage triggers removal within 250 CIS (Table 2).

• Reinspection intervals depend on found wear: 300 CIS for limited wear, 600 CIS if no wear through to parent material (Table 2).

• When both engines are affected on the same aircraft, inspection windows are compressed: second engine inspection within 10 CIS, removal of one engine within 25 CIS if both show specified wear (Table 3).

The AD assigns no express procedural rights to third parties such as lessors, but replacement and removal obligations will interact with lease and maintenance agreements in practice. The AD text does not specify penalties or enforcement procedures in this document, beyond making compliance mandatory as an AD effective 14 August 2010.

The AD text supplied sets mandatory technical obligations and an effective date. It does not, within the body of the AD as provided, state specific monetary fines, criminal penalties, or exact enforcement mechanisms. The instrument is an Airworthiness Directive issued by the Civil Aviation Safety Authority, and the AD explicitly becomes effective on 14 August 2010, signed by David Punshon, Delegate of CASA. The AD also notes that CASA "determined that this AD may be applicable to Australian aircraft" following review of State of Design ADs (Background).

Operationally, ADs are regulatory instruments that impose continuing airworthiness obligations. The AD defines inspection, removal, replacement and terminating modification obligations with precise cycle-count triggers and timeframes: initial inspections per Table 1, actions per Table 2, coordination per Table 3, and a terminating action identified in the AD. Non-compliance with an AD typically affects an operator’s airworthiness compliance status and may affect an aircraft’s fitness to fly, but the AD text does not itself list the administrative remedies CASA might use where operators fail to comply.

The AD accepts alternate methods of compliance (AMOCs) where later revisions of the PW ASB have been "approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2003-09-02" (quoted language from the AD). That indicates CASA intends to accept FAA-approved AMOCs for the relevant ASB updates, and in practice AMOCs require formal approval by the authority.

In short, the AD sets binding technical duties and timescales which CASA expects operators to meet from the effective date. The document as provided does not describe enforcement processes or penalties, instead focusing on the technical requirements and their rationale. Operators and maintenance organisations should therefore treat the AD as a mandatory airworthiness requirement with legal force under CASA’s regulatory framework, and should consult CASA for procedural queries about enforcement, AMOCs, or recordkeeping expectations beyond the technical instructions.

The AD explicitly situates itself within the international airworthiness regulatory context by referencing United States Federal Aviation Administration material and manufacturer service bulletins. The AD identifies FAA AD 2003-09-02, Amendment 39-13131 dated 21 April 2003, as relevant (Note 2). It also requires inspections "in accordance with paragraphs 1.A. through 1.I of the Accomplishment Instructions" of PW ASB PW4G-100-A72-170 Rev 3 dated 31 January 2003, and permits later revisions of that ASB to be acceptable only if they are "approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2003-09-02." That creates a defined interaction: CASA’s AD requires specific manufacturer procedure text, but confers a role for FAA in approving alternative or updated ASB revisions through the AMOC mechanism.

The AD also references Pratt & Whitney service bulletins and a Chromalloy repair procedure as qualifying post-modification states for terminating action. Specifically, the AD identifies PW SB No. PW4G-100-72-159, PW SB No. PW4G-100-72-187, and Chromalloy Repair Procedure 00-CFL-039-0 as modifications that, when implemented, constitute a terminating action for the repetitive inspections. Those SBs and repair procedures are manufacturer and repair-provider instruments that operate alongside regulatory AD requirements; once implemented to the AD’s satisfaction, they change the operator’s lifecycle obligations.

The AD does not explicitly reference Australian aviation legislation such as the Civil Aviation Act or the Civil Aviation Safety Regulations within the text provided. However the form and issuance by CASA implies that the AD is an instrument under CASA’s regulatory authority and is designed to be enforced within that domestic regulatory framework. The AD’s Background states CASA reviewed State of Design ADs and determined the AD "may be applicable to Australian aircraft." CASA’s acceptance of FAA-approved AMOCs for later ASB revisions indicates an intention to rely on the FAA’s determinations as to whether later manufacturer revisions meet FAA AD requirements.

Practical implications of these interactions:

• Operators must apply the specified PW ASB text to carry out borescope inspections, or adopt a later ASB revision only if the FAA has approved it as an AMOC. That channels the update path for inspection technique and acceptance criteria through the FAA AMOC process.

• Implementing the terminating action requires compliance with the manufacturer SBs or the Chromalloy repair procedure listed, which themselves may require FAA approval or CASA acceptance depending on jurisdictional maintenance and certification processes. The AD treats those SBs and repair procedures as qualifying for terminating action once applied.

• Where operators hold international certificates, lease agreements, or parts approvals, the AD’s cross-recognition of FAA AMOCs and its alignment with FAA AD 2003-09-02 will affect cross-border compliance and acceptance of work done under FAA-approved procedures.

• The AD does not alter contractual or commercial arrangements such as warranties, lease indemnities, or insurance directly. However, executing removals, replacements or terminating actions will interact with those commercial arrangements in practice because they affect component condition, downtime and parts replacement liabilities.

Operators should therefore coordinate with their regulatory compliance teams, the engine manufacturer, and maintenance providers when applying later ASB revisions or pursuing the terminating action, so as to ensure that any method of compliance has the necessary regulatory approvals and does not create unintended certification gaps.

The AD text itself records an internal reference and a pathway for updates of the technical service information it mandates. Relevant elements from the AD:

• The AD relies on Pratt & Whitney Alert Service Bulletin PW4G-100-A72-170 Revision 3, dated 31 January 2003, for the borescope inspection procedure (Requirement 1). It explicitly states "borescope-inspect in accordance with paragraphs 1.A. through 1.I of the Accomplishment Instructions" of that revision.

• The AD recognises earlier revisions as transitional. Engines borescope-inspected before the effective date of the AD "in accordance with PW ASB PW4G-100-A72-170, Revision 1, or Revision 2, must follow Requirements 1 through 3 of this AD, after the effective date of this AD." That means earlier inspections are not grandfathered forever; the AD imposes the same ongoing requirements from the effective date forward.

• The AD allows later revisions of the ASB to be used for compliance only if those later revisions are "approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2003-09-02." The AD effectively ties acceptance of ASB updates to FAA AMOC action.

• The AD explicitly references FAA AD 2003-09-02 Amdt 39-13131 dated 21 April 2003 (Note 2). That FAA AD is treated as a foundational State of Design document. The CASA AD itself was issued with the effective date 14 August 2010, and is identified as AD/PW4000/15 (15/2010).

• The AD provides a terminating action specifically tied to certain SBs and a Chromalloy repair procedure. The AD wording treats implementation of those SBs and procedures as a mechanism to cease repetitive inspections. The listed SBs are PW4G-100-72-159 and PW4G-100-72-187, and Chromalloy Repair Procedure 00-CFL-039-0.

Beyond these references, the AD as provided does not list subsequent amendment entries, revisions to the AD itself, or later CASA actions modifying AD/PW4000/15. If operators require a later version of the AD, or confirmation that later ASB revisions have been accepted by the FAA as AMOCs, they must check CASA and FAA repositories and any later AD issuances for updated amendment history. The AD’s acceptance route for later ASB revisions (FAA AMOC approval) is the explicit procedural mechanism it gives for accommodating updated manufacturer guidance.

The AD text supplied contains no references to litigation, court decisions, or disputes concerning this AD. It names no cases, and it does not record any judicial review or legal challenge in the text provided. The document is an administrative airworthiness directive, signed by the CASA delegate and effective 14 August 2010.

Because the AD text does not supply litigation history, users seeking whether this AD has been the subject of judicial or administrative review, or whether disputes arose from its implementation, must consult CASA records, court databases, or regulatory enforcement records. The AD does reference FAA AD 2003-09-02 as the State of Design AD and acknowledges interactions with FAA AMOCs; no litigation involving those FAA instruments is noted within this AD document.

Several operational and legal "gotchas" arise from the text of the AD. These are not policy judgments, they are mechanical features that create traps for unfamiliar operators or maintenance planners.

1. Narrow applicability, broad operational consequences. The AD applies only to engines having HPC inner case assembly P/N 53H272-01 and serial numbers P733301 through P733500. Operators may assume the AD does not apply if engines have different P/Ns or serials. That is correct, but the AD warns "These engines are installed on, but not limited to Airbus Industrie A330 aeroplanes." If engines with the relevant P/N/serial numbers are installed on other types, those aircraft are still within scope.

2. Different cycle counters matter. The AD uses three distinct cycle metrics: cycles-since-new (CSN), cycles-since-refurbishment (CSR), and cycles-in-service (CIS). Table 1 requires assessing CSN or CSR to set the initial inspection schedule. Table 2 and Table 3 use CIS to define reinspection and removal timelines. Operators must ensure their maintenance records accurately track each metric and use the correct one for each action. A misread of "CSN" versus "CIS" could lead to missed deadlines or premature actions.

3. Measurement thresholds are precise and literal. The AD requires removal if "14th stage rubstrip shows wear through to the parent material of the stator, with the circumferential length of the wear being 1.0" or more" and similarly 2.0" for the 15th stage. That implies a precise physical measurement standard and an inspector must be able to measure circumferential length. Maintenance organisations must ensure borescope inspection procedures and personnel capability can reliably detect and measure circumferential wear to those inch thresholds. Ambiguity in measurement technique could lead to disputes about whether removal timetables are triggered.

4. Tight timelines when two affected engines are installed. Table 3 demands the second engine be inspected "Within 10 CIS since borescope inspection of first engine" and if both engines show specified wear, "Remove either the first or second engine from service within 25 CIS since borescope inspection of the second engine" and replace with a serviceable engine. Those compressed windows create logistical pressure for operators that do not have a readily available serviceable engine, for example if the operator lacks a zero CSN engine or the operator has not yet performed the terminating action on a spare.

5. Definition of "serviceable engine" narrows replacement options. The AD defines a serviceable engine as only three categories: zero CSN HPC, engine covered by the terminating action, or an engine inspected and following a 600 CIS reinspection schedule. That excludes many used or partially-worn engines that might otherwise be considered airworthy. Operators depending on engine pools or short-term leases must confirm whether candidate engines meet the AD definition before substituting. This may constrain the market for replacement engines and lengthen ground time.

6. Terminating action is a hardware modification with specific qualifying SBs and repair procedure. The AD treats replacement of the HPC inner rear case assembly with one containing a Haynes 242 rear hook, or assemblies modified by PW SB No. PW4G-100-72-159, PW SB No. PW4G-100-72-187 or Chromalloy Repair Procedure 00-CFL-039-0, as terminating. Implementing those SBs or repairs requires parts, shop capability, and possibly FAA or CASA acceptance steps. Availability of Haynes 242 assemblies or Chromalloy repair slots could be limited, creating operational bottlenecks.

7. Transitional inspections under earlier ASB revisions do not exempt ongoing AD obligations. Engines borescope-inspected before the AD’s effective date under ASB Rev 1 or Rev 2 "must follow Requirements 1 through 3 of this AD, after the effective date." That means prior inspection does not remove the repeating obligations imposed by this AD.

8. Acceptance of later ASB revisions is conditioned on FAA AMOC approval. If a later PW ASB revision exists but has not been FAA-approved as an AMOC to FAA AD 2003-09-02, CASA’s AD text does not accept it as a compliance route. Operators wishing to adopt updated manufacturer procedures must confirm FAA AMOC status before relying on them for CASA AD compliance.

9. The AD text does not state enforcement mechanisms or recordkeeping details. The AD imposes precise technical obligations and timescales but leaves procedural enforcement and documentation practice to the regulatory framework. Operators must proactively ensure their records can justify compliance if audited by CASA.

10. Timing of compliance relative to the effective date. The AD becomes effective 14 August 2010. Table 1 schedules initial inspections relative to the effective date using CSN/CSR and CIS thresholds. Operators who did not previously borescope inspect under the required ASB revision need to calculate current CSN/CSR and CIS correctly, and to apply those schedules to avoid missing mandated windows.

These "gotchas" are mechanical. They arise from the AD’s specificity about engine identification, measurement thresholds, precise cycle metrics and compressed windows for dual-engine installations. The AD supplies the specific clauses and tables that create these operational constraints.

This section gives a practical compliance checklist mapped to the AD’s requirements and quoted language. Operators and maintenance organisations should use the official AD and the referenced PW ASB material when executing compliance steps.

Step 1, identify affected engines

• Confirm engine type and configuration: PW4164, PW4168, or PW4168A.
• Confirm HPC inner rear case assembly part number: P/N 53H272-01.
• Confirm engine serial number is within P733301 through P733500.
• If yes to all above, the AD is applicable (see Applicability).

Step 2, confirm ASB and inspection method

• Obtain Pratt & Whitney Alert Service Bulletin PW4G-100-A72-170, Revision 3, dated 31 January 2003.
• Review and be prepared to perform borescope inspection "in accordance with paragraphs 1.A. through 1.I of the Accomplishment Instructions" of that ASB (Requirement 1).
• If relying on a later ASB revision, confirm that the later revision has been "approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2003-09-02," because the AD accepts later revisions only on that basis.

Step 3, schedule initial inspection per Table 1

• Determine CSN and CSR values for the HPC inner rear case assembly on the AD effective date.
• If the assembly had "Fewer than 900 cycles-since-new (CSN) or cycles-since-refurbishment (CSR) on the effective date," schedule the initial borescope inspection "Before accumulating 1,500 CSN or CSR, whichever occurs later" (Table 1).
• If the assembly had "900 or more CSN or CSR," schedule initial borescope inspection "Within 600 cycles-in-service (CIS) after the effective date of this AD" (Table 1).

Step 4, perform borescope inspection to the ASB procedure

• Carry out borescope inspection per the PW ASB paragraphs 1.A-1.I.
• Ensure inspection personnel and facilities can detect and measure circumferential wear lengths to the thresholds specified in Table 2 (1.0 inch for 14th stage, 2.0 inches for 15th stage) and can document findings.

Step 5, apply Table 2 actions according to inspection findings

• If 14th stage rubstrip wear through to parent material with circumferential length >= 1.0", "Remove engine from service within 250 CIS" (Table 2(1)).
• If 15th stage rubstrip wear through to parent material with circumferential length >= 2.0", "Remove engine from service within 250 CIS" (Table 2(2)).
• If lesser wear through to parent material on those stages is found, reinspect every 300 CIS (Table 2(3) and (4)).
• If neither rubstrip shows wear through to parent material, reinspection interval is every 600 CIS (Table 2(5)).

Step 6, apply Table 3 actions where two affected engines are installed

• If both engines on an aircraft are affected, perform second engine inspection "Within 10 CIS since borescope inspection of first engine" (Table 3).
• If both engines show wear as specified in Table 2 Steps (1) through (4), remove either engine "within 25 CIS since borescope inspection of the second engine and replace with a serviceable engine." Then remove or re-inspect the remaining engine following Table 2 and, if still applicable, follow Requirement 3 (Table 3).
• If one engine shows Table 2 Steps (1)-(4) wear and the other engine shows Table 2 Step (5) wear, the AD requires both engines be removed or reinspected in accordance with Table 2 and then perform subsequent actions as specified in Requirement 3 (Table 3).
• If both engines show no wear (Step (5) on Table 2), inspect the second engine as specified in Table 1 (Table 3(3)), and then proceed according to Table 2 results.

Step 7, determine what constitutes a "serviceable engine"

• A serviceable engine, per the AD, is one of: a. "An engine that incorporates an HPC with zero CSN"; or b. "An engine covered by the Terminating Action detailed in this AD"; or c. "An engine inspected as specified in Requirements 1 through 3 of this AD, and is following the 600 CIS re-inspection interval as specified in Table 2 of this AD."
• Confirm any candidate replacement engine meets one of these categories before using it to comply with Table 3 replacement requirements.

Step 8, consider terminating action where appropriate

• The AD identifies replacement of the HPC inner rear case assembly with one "containing a Haynes 242 rear hook" or assemblies modified or replaced by PW SB No. PW4G-100-72-159, PW SB No. PW4G-100-72-187, or Chromalloy Repair Procedure 00-CFL-039-0 as "Terminating Action" for the repetitive borescope inspections.
• If an operator elects terminating action, plan for procurement of the Haynes 242 assemblies or scheduling of the listed SBs or Chromalloy repair, and coordinate any necessary regulatory acceptance or certification steps to document that the terminating action has been completed in accordance with the AD.

Step 9, document compliance and maintain cycle records

• Maintain records showing CSN, CSR and CIS calculations used to schedule inspections and to trigger removal or reinspection deadlines.
• Document borescope findings, measurements of circumferential wear, removal dates, and records of engine replacements or terminating action implementation.

Step 10, manage logistics and supply-side constraints

• Anticipate potential bottlenecks: availability of Haynes 242 assemblies, space and schedule at repair shops implementing PW SBs or Chromalloy repair procedure, and availability of "serviceable engines" per the AD definition.
• If a serviceable engine is not immediately available under the AD’s definition, plan for timely removal and re-inspection schedules to avoid exceeding 250 CIS or other AD time limits.

Notes and practical clarifications

• Engines previously inspected under earlier ASB revisions (Rev 1 or Rev 2) "must follow Requirements 1 through 3 of this AD, after the effective date of this AD." That means operators cannot rely on prior inspections as a permanent substitution for the AD’s obligations; they must enter the AD’s ongoing inspection cycle as required.
• For operators wishing to use an updated ASB revision, the AD requires FAA AMOC approval of that revision before it can be relied upon for compliance with this CASA AD.
• The AD becomes effective 14 August 2010; calculate CIS intervals and deadlines relative to that effective date as required in Table 1 and Table 2.

If there is any regulatory ambiguity about the acceptability of a specific repair procedure, AMOC status, or documentation format, operators should consult CASA directly and keep contemporaneous records of communications and approvals. The AD text supplies the operative technical thresholds and the acceptable terminating action methods; compliance requires operators to map their maintenance operations to those specific clauses and to ensure they have suitable replacement engines if required by Table 3.