AD/PW300/1 Amdt 1 - Engine High Pressure Compressor Drum

The AD revolves around a small set of interlocking technical and compliance concepts drawn from manufacturer material and the regulatory amendment text.

• Applicability and identification of affected parts. The AD targets post-SB PW300-72-24287 HPC drum rotor assemblies P/N 30B2478 and P/N 30B2542 installed in PW305A and PW305B engines, but only where the operator has not incorporated SB PW300-72-24376. The applicability language is precise: engines with those post-SB assemblies and without the terminating SB incorporated are in scope.

• Inspection method and standard. The required inspection is a borescope inspection of the interior of the HPC drum rotor assembly for cracks, performed "in accordance with the PW305 MM 05-20-00 'Periodic Inspections, Boroscope' requirements" (Requirement 1.a). The AD therefore does not invent a new inspection technique; it adopts the manufacturer's maintenance manual procedure as the technical standard to be used.

• Timing and intervals. The compliance schedule has two layers. For engines that have not satisfied earlier inspection requirements, the initial inspection window for Requirement 1.a is "within 500 flight hours after 17 January 2008" (Compliance). Repeat inspections under Requirement 2.a are to be performed "at intervals not to exceed 1350 flight cycles per PW305 MM 05-20-00" (Compliance). If an inspection finds a crack, the action is removal of the engine for HPC drum rotor replacement "before further flight" (Requirements 1.b and 2.b).

• Terminating action. The AD specifies a terminating action: replacement of the affected P/N 30B2478 or 30B2542 with post-SB PW300-72-24376 assembly P/N 31B6325-01 or a later superseding P/N will "constitute terminating action for the inspection requirements of this AD." The AD also notes that SB PW300-72-24462 and prior inspections performed in accordance with PW305 MM satisfy Requirement 1 if done before the effective date.

• Source of the corrective design. Pratt & Whitney Canada issued Service Bulletin PW300-72-24376 to make available P/N 31B6325-01, the replacement drum assembly that the AD identifies as not susceptible to the cracking addressed. The AD references that SB PW300-72-24462 was issued for the initial inspection of affected drums and that PW305 MM Revision No.26 added repeat inspection interval requirements.

• Rationale and evidence cited. The AD background asserts that P&WC determined the subject drums are susceptible to significant cracks in the labyrinth seal region, and that manufacturer data (Service Information Letter: PW300-093) indicated a number of high-time pre-SB drums remained in service and therefore presented a potential for hazardous disk failure in consequence of non-compliance with inspection requirements. The AD is therefore framed as a prescriptive, targeted response to that identified safety risk.

• Amendment nature. The published instrument is an amendment (Amdt 1) that corrects a typographical error in the P/N listing in Requirement 2 of the AD, and sets an amendment effective date of 10 April 2008 while noting the original AD became effective on 17 January 2008. Transport Canada AD CF-2007-25R1 is explicitly referred to for cross-reference.

These concepts structure a compliance regime that delegates technical specifics to manufacturer documentation (SBs and MM), imposes inspection and removal obligations at defined time limits, and provides a defined engineering solution as a terminating action. The AD therefore operates by combining regulatory prescription with manufacturer's technical standards.

The AD places obligations on a narrow set of participants in the aviation supply chain and has financial and operational effects concentrated on those parties.

• Operators and aircraft owners that have PW305A or PW305B engines in service. Specifically, operators whose engines contain post-SB PW300-72-24287 HPC drum rotor assemblies P/N 30B2478 or 30B2542 and who have not incorporated SB PW300-72-24376 are the primary affected parties. The applicability language explicitly targets "All post-Service Bulletin (SB) 24287, Pratt and Whitney Canada PW305A and PW305B Engines without SB PW300-72-24376 incorporated." Those operators must inspect and potentially remove engines from service for replacement if cracks are found.

• Maintenance organisations and licensed engineers tasked with inspections. The AD requires a borescope inspection "in accordance with the PW305 MM 05-20-00 'Periodic Inspections, Boroscope' requirements" (Requirement 1.a and 2.a). Maintenance providers will therefore need access to the PW305 maintenance manual revision cited, the appropriate borescope equipment and competence, and processes to log and act on findings. They carry the immediate operational tasking and associated costs.

• Parts suppliers and the manufacturer. The AD identifies P/N 31B6325-01 as the replacement assembly that constitutes terminating action. Pratt & Whitney Canada, and authorised parts distributors, will supply that assembly through SB PW300-72-24376. Supply chain capacity, parts availability and lead times affect how quickly operators can comply by replacing affected drums.

• Aircraft dispatch and commercial operators. Because a crack found during inspection triggers engine removal "before further flight" (Requirements 1.b and 2.b), operators are exposed to aircraft downtime, potential flight cancellations or substitutions, and the direct cost of engine change-out and replacement parts. The background notes that some high-time pre-SB assemblies remained in-service, meaning certain operators with older drums carry concentrated exposure.

• Airworthiness authorities and regulators. The AD itself is issued by the Civil Aviation Safety Authority as indicated by the signature block naming David Punshon, Delegate of CASA, and the dates; it also explicitly references Transport Canada AD CF-2007-25R1, which means that this AD aligns with or follows related foreign authority actions and service information. The regulators thus coordinate through cross-reference to manufacturer and foreign authority materials.

• Operators who have already complied with the relevant SB or MM requirements. The AD acknowledges that operators who inspected affected assemblies per SB PW300-72-24462 and/or the PW305 MM prior to the effective date satisfy Requirement 1. Those operators are affected only to the extent they must continue with the repeat inspection regime unless they accomplish the terminating replacement.

Who pays and who decides. The owner/operator of the aircraft bearing the affected engine is operationally responsible for arranging and paying for borescope inspections and, if necessary, engine removal and replacement. Maintenance organisations will charge for inspection and replacement labour. The decision to terminate recurring inspections by installing P/N 31B6325-01 is an operator choice constrained by parts availability and cost; the AD sets the technical path but not who pays.

Concentration of costs and risk. The impacts are concentrated on operators with the specific older drum assemblies; the AD identifies these assemblies as "high-time pre-SB-PW300-72-24376" units and notes a non-trivial population remained in service. That concentration implies some operators face immediate parts and labour costs, while operators who had earlier adopted the SB or installed the new P/N have avoided those ongoing inspection costs.

The AD lays out a limited set of prescriptive duties, and it uses manufacturer material to define the technical standard for performance of those duties.

Duties specified in the AD

• Identify applicability. Operators must determine whether their engines have the post-SB PW300-72-24287 HPC drum rotor assemblies P/N 30B2478 or 30B2542 and whether SB PW300-72-24376 has been incorporated. The applicability statement in the AD is the trigger for compliance obligations.

• Conduct borescope inspections. Requirement 1.a directs that operators "gain access to inside of affected HPC rotor assembly and inspect (boroscope) its interior for cracks in accordance with the PW305 MM 05-20-00 'Periodic Inspections, Boroscope' requirements." The PW305 maintenance manual therefore provides the procedural content and acceptance criteria used to determine whether a drum is cracked.

• Timing requirements. The Compliance text requires that the initial inspection occur "within 500 flight hours after 17 January 2008" (for those subject to the original issue), and that repeat borescope inspections occur "at intervals not to exceed 1350 flight cycles per PW305 MM 05-20-00." These are mandatory scheduling constraints in the AD.

• Removal and replacement before further flight if a crack is found. Requirement 1.b and 2.b explicitly mandate removal of the engine for HPC drum rotor replacement "before further flight" when a crack is found on inspection. There is therefore zero tolerance for continuing operation with a cracked drum.

• Terminating action. Replacement of the affected P/Ns 30B2478 or 30B2542 with post-SB assembly P/N 31B6325-01 or later superseding P/N is declared to be terminating action for the inspection requirements. Operators therefore have a clear compliance pathway to remove ongoing inspection obligations by installing the specified replacement assembly via SB PW300-72-24376.

• Credit for prior inspections. The AD provides that prior inspections performed per SB PW300-72-24462 and/or PW305 MM 05-20-00 before the effective date of the directive satisfy Requirement 1, which prevents redundant inspections where appropriate.

Rights and scope limitations expressly or implicitly present in the AD

• Use of manufacturer standards. The AD delegates the procedural particulars to the PW305 MM and relevant SBs, which means an operator's duty is to perform inspections "in accordance with" those manufacturer-prescribed procedures. The AD does not prescribe a different inspection method.

• No alternative terminating actions specified. The AD identifies only P/N 31B6325-01 or later superseding P/N as terminating action. The AD does not provide alternate modification or repair options as terminating actions; therefore, operators must use the specified replacement assembly to cease recurring inspections.

• Discrete time windows for compliance. The Compliance clauses create specific time windows; operators who have already complied before the effective date receive credit as described.

• No rights of appeal or administrative review are contained in the AD text itself. The AD records its mandatory requirements and effective dates but does not articulate a process within the text for seeking an alternate means of compliance or for exemption. Any such processes, if available, are not specified in the provided AD text.

Who records compliance. The AD does not specify record-keeping requirements in its text, but the operative duties imply maintenance records will need to show the borescope inspections and any replacement actions. The AD explicitly references the PW305 Maintenance Manual as the standard for inspection; maintenance documentation consistent with that manual is therefore the natural place to evidence compliance.

In summary, the AD places straightforward, time-bounded duties on operators and maintenance providers to inspect defined P/N drums, remove cracked drums before further flight, and optionally remove the recurring inspection duty by installing a specific replacement assembly. The AD delegates technical detail to manufacturer SBs and the PW305 MM.

The AD text supplied sets mandatory technical and timing requirements but contains no express penalty table, civil sanction schedule, or enforcement procedure within the instrument as published. The AD establishes compliance obligations (inspection windows, repeat intervals, actions on finding a crack, and terminating action by replacement) and records effective dates and amendment history, but it does not state monetary penalties, suspension provisions, or the legal enforcement mechanism in this extract.

What the AD does provide that is relevant to enforcement timing and operational effect

• Effective dates and compliance windows. The amendment became effective on 10 April 2008, with the original AD effective from 17 January 2008. Compliance timings are specified relative to those dates (for example, initial inspections within 500 flight hours after 17 January 2008 for the original issue). These timing provisions frame any enforcement discretion that a regulator may exercise, but no enforcement sanctions are stated in the AD text.

• Prescriptive "before further flight" requirement. The AD includes the unambiguous operational instruction that if a crack is found the engine must be removed for HPC drum rotor replacement "before further flight." The operational force of that requirement means continued flight with a known cracked drum would be contrary to the AD's stated actions, but the AD text does not set out the consequences or fines for continuing to operate.

• Cross-reference to other authorities. The AD refers to Transport Canada AD CF-2007-25R1, which indicates cognate action by another regulator. The AD reproduces manufacturer service information and maintenance manual provisions as mandatory inspection standards. The effectiveness of enforcement therefore in practice will often be tested through acceptance of maintenance documentation and evidence of compliance, but the AD text itself offers no enforcement schedule.

Implication for operators and maintenance organisations

• The text obliges operators to perform inspections and replacements as described and to treat prior qualifying inspections as credit where applicable. While the AD does not contain penalties, operators should treat the AD's requirements as mandatory regulatory instructions, given its issuance by the Civil Aviation Safety Authority and the inclusion of specific "before further flight" language. The absence of explicit penalties in this posted extract does not imply an absence of regulatory enforcement capacity outside this instrument; it simply reflects the content of the AD text provided.

Because the document supplied is limited to the AD text and background, any detailed description of criminal, civil or administrative penalties, or of processes for enforcement, appeal or alternate means of compliance, would be speculation beyond this source. The AD does not provide such mechanisms in the text supplied.

The AD explicitly interfaces with manufacturer materials and at least one foreign airworthiness directive, and it therefore operates by importing technical standards rather than restating them.

References to manufacturer documents and maintenance manual

• The AD makes the PW305 Maintenance Manual (MM) 05-20-00 the operative technical standard for the borescope inspection procedure and the repeat inspection intervals. Requirement 1.a specifies that the borescope inspection must be performed "in accordance with the PW305 MM 05-20-00 'Periodic Inspections, Boroscope' requirements." The Compliance section cites repeat inspection intervals in terms of "per PW305 MM 05-20-00." By doing so, the AD incorporates an external technical document into the compliance regime and requires operators to follow the MM's methodologies and acceptance criteria.

• Several manufacturer Service Bulletins are incorporated by reference. SB PW300-72-24462 was issued by Pratt & Whitney Canada for initial inspection of affected HPC drums. SB PW300-72-24376 is the supplier vehicle for the replacement P/N 31B6325-01 that the AD identifies as terminating action. The AD therefore establishes a direct dependency between regulatory compliance and the SBs; incorporation of SB PW300-72-24376 on an engine is the mechanism by which an operator can remove the recurring inspection obligation.

Cross-reference to foreign airworthiness directive

• The AD explicitly notes "Note: Transport Canada AD CF-2007-25R1 dated 13 February 2008 refers." This cross-reference shows alignment or coordination with a Transport Canada AD addressing the same or related subject matter. The AD therefore does not operate in isolation but in the context of international airworthiness correspondence and potentially harmonised safety action between CASA and Transport Canada.

Absence of broader statutory interaction in the text

• The AD text supplied does not itself cite enabling provisions of aviation statutes or regulations, nor does it set out how it interacts with criminal or administrative sanctioning regimes, appeal processes, or alternate means of compliance (AMOC) frameworks. The AD prescribes technical actions and timings and refers to manufacturer documents and a foreign AD for technical and contextual support. Any procedural interlocks with wider regulatory instruments or legal processes are not described in the AD text provided.

Practical interoperability consequences

• Because the AD designates manufacturer SBs and the PW305 MM as the standards to use, operators must ensure their maintenance practices align with those documents to satisfy the AD. That may create an operational requirement to hold, apply and record compliance with the PW305 MM and relevant SBs. Incorporation of SB PW300-72-24376 is the defined route to cease recurring inspections; operators who have already incorporated that SB are out of scope. Conversely, operators subject to the AD must arrange inspections and potential replacements in a way that harmonises with their existing maintenance schedules and regulatory obligations.

• The AD’s reference to Transport Canada suggests that operators flying under multiple national jurisdictions may face similar instructions from foreign authorities, which can reduce the risk of conflicting obligations but may also require coordination to satisfy multiple authorities’ procedural expectations.

In short, the AD functions by importing manufacturer technical standards and by cross-referencing a related foreign AD. It does not, on its face, describe interactions with broader statutory penalty or administrative procedures in the text supplied.

The instrument provided is AD/PW300/1 Amdt 1. The AD and its amendment(s) as recorded in the supplied text show a short but specific amendment trajectory.

• Original issue. The AD's original issue became effective on 17 January 2008. The original AD established the inspection obligations for the identified HPC drum rotor assemblies and set the initial compliance time of "within 500 flight hours after 17 January 2008" for Requirement 1.a as recorded in the Compliance section.

• Amendment 1. The published document is Amendment 1 (Amdt 1) to AD/PW300/1. The amendment became effective on 10 April 2008. The stated purpose of the amendment is to "correct a typographical error in the P/N of HPC drum assemblies listed in Requirement 2 of this AD." The amendment retains the substantive inspection and replacement obligations and fixes the typographical error to ensure clarity of the part number references used in the recurring inspection requirements.

• Document dating and signature. The AD text includes a signed block naming "David Punshon, Delegate of the Civil Aviation Safety Authority" and is dated 26 February 2008. The amendment effective date is 10 April 2008, which indicates a formal amendment process took place subsequent to the date on the signature block.

• Reference to manufacturer document revisions. The AD background notes that the PW305 Maintenance Manual was revised (Revision No.26) to add the repeat inspection interval requirements. It also records the issuance of P&WC Service Bulletins PW300-72-24462 for initial inspection and PW300-72-24376 to make the replacement assembly available. Thus the amendment history includes not just regulator action but also updates in manufacturer maintenance material and SB provision that underpin the AD.

• Cross-reference to foreign AD. The AD refers to Transport Canada AD CF-2007-25R1 dated 13 February 2008, which indicates that the regulatory action sits alongside or in response to related foreign authority measures. That reference documents a contemporaneous international safety action in the same technical domain.

Taken together, the amendment history is short and technical: an original AD effective 17 January 2008 establishing inspection and replacement requirements, followed by a correction of a typographical error published as Amendment 1 effective 10 April 2008. The AD also documents the sequence of manufacturer outputs (SBs and MM revision) that provided the technical content the AD enforces.

The AD text supplied contains no record of litigation, legal challenges, judicial review, or court decisions associated with AD/PW300/1 or its amendment. The document is limited to the directive text, compliance requirements, background rationale, and the administrative correction in the amendment. There is no mention of court cases, appeals, or other judicial proceedings in the supplied material.

Because the supplied source is silent on litigation, no claims about legal disputes, settled or otherwise, can be made from this text. If a reader requires information about challenges to the AD or dispute resolution processes (for example, appeals of regulatory action, claims for compensation due to forced grounding, or enforcement actions by CASA), that material is not present in the AD as supplied and would need to be obtained from other regulatory records, court dockets, or agency publications outside the supplied text.

The AD contains a number of operational and drafting details that can produce practical traps for operators, and the supplied text contains explicit wording that creates potential compliance pitfalls.

• Narrow applicability wording. Applicability is limited to "All post-Service Bulletin (SB) 24287, Pratt and Whitney Canada PW305A and PW305B Engines without SB PW300-72-24376 incorporated." That phrasing ties applicability to a combination of a particular post-SB drum assembly and the absence of incorporation of a later SB. Operators must verify their engine parts history carefully. Misreading the SB references or failing to confirm incorporation of SB PW300-72-24376 could lead to unnecessary work or missed compliance.

• Two similar SB numbers and multiple P/Ns. The AD references multiple SBs (PW300-72-24287, PW300-72-24462, PW300-72-24376) and multiple part numbers (30B2478, 30B2542, 31B6325-01). The amendment history notes that a typographical error in a P/N in Requirement 2 was corrected. Operators and maintainers must cross-check SB and P/N references carefully to avoid acting on the wrong assembly or failing to apply the terminating action because they used an incorrect part number.

• Dependence on PW305 MM for inspection detail. The AD delegates the inspection procedure and repeat interval standard to the PW305 Maintenance Manual ("in accordance with the PW305 MM 05-20-00 'Periodic Inspections, Boroscope' requirements"). If an operator does not have the cited MM revision (Revision No.26 is mentioned in background) or misapplies an earlier revision’s intervals or acceptance criteria, they may not be performing inspections in accordance with the AD. Maintenance organisations should ensure they use the correct MM revision and interpret boroscope acceptance criteria consistently with the MM.

• Two different compliance metrics: flight hours vs flight cycles. The initial inspection compliance timing is expressed as "within 500 flight hours after 17 January 2008," whereas repeat inspections are expressed as "at intervals not to exceed 1350 flight cycles per PW305 MM 05-20-00." Operators must therefore manage both flight hours and flight cycles records to meet the AD schedule. Confusing the two metrics or misapplying the intervals could yield non-compliance.

• Credit for prior inspections only for Requirement 1. The AD expressly states that inspections performed per SB PW300-72-24462 and/or PW305 MM 05-20-00 prior to the effective date "satisfy the actions detailed in Requirement 1." That credit applies to the initial inspection. The AD does not provide explicit credit for repeat inspections; operators need to determine repeat inspection timing based on the MM and the AD. Failure to treat prior inspections correctly could lead either to unnecessary re-inspection or to missing a required repeat inspection window.

• "Before further flight" obligation on detection of crack. The AD requires removal of the engine for replacement before further flight where a crack is found during borescope inspection. This creates an immediate operational consequence; the discovery of a crack will produce aircraft downtime and the need to source replacement drums. Operators need to plan for contingencies such as spares availability and engine removal slots.

• Terminating action specificity. The AD identifies replacing the affected drum with P/N 31B6325-01 "or later superseding P/N" as terminating action. Operators should ensure that any purportedly superseding P/N is formally designated as such by the manufacturer and is accepted under the SB PW300-72-24376 process. Assuming another modification, repair or alternative P/N constitutes terminating action without manufacturer or regulatory confirmation risks non-compliance.

• High-time population remains in service. The background notes "a number of high-time Pre-SB-PW300-72-24376 HPC drum rotor assemblies (P/Ns 30B2478 and 30B2542) ... are still in-service." Operators with older drums therefore face concentrated operational risk and potentially limited availability of compliant replacement drums. Parts lead times and costs may be significant.

• No penalties or appeal mechanisms specified in the AD. The supplied text does not describe enforcement or administrative review channels. If operators rely on absence of penalties for relief, that expectation is not supported by the AD text. The AD’s prescriptive instructions and "before further flight" language are operationally binding in the instrument even though the AD text supplied does not itself set out sanctioning mechanisms.

• Typographical correction history. The amendment corrects a typographical error in Requirement 2 P/N listing. Operators referencing earlier printed copies of the AD or relying on third-party summaries should confirm they are using the amended text to avoid following erroneous part numbers.

These points are directly traceable to the AD text and background. They highlight where misreading, record-keeping lapses, confusion over SB/P/N cross-references, or supply-chain limitations can produce immediate operational consequences.

The AD provides a clear set of procedural steps to achieve compliance. The following is a practical, source-grounded checklist aligned to the AD text and manufacturer materials referenced.

1. Confirm applicability for each engine

• Verify whether each PW305A or PW305B engine is fitted with a post-SB PW300-72-24287 HPC drum rotor assembly with P/N 30B2478 or 30B2542.
• Confirm whether SB PW300-72-24376 has been incorporated on that engine. If SB PW300-72-24376 has been incorporated (i.e. P/N 31B6325-01 or later superseding P/N installed), the engine is not subject to the inspection requirement in this AD.

2. Review historical compliance credit

• If a borescope inspection of the affected HPC drum assembly was carried out per SB PW300-72-24462 and/or PW305 MM 05-20-00 prior to the effective date of the AD, that inspection "satisfy the actions detailed in Requirement 1 of this AD." Record the inspection and proceed to determine repeat inspection timing per the PW305 MM.

3. Schedule initial inspection within the required window

• For engines without prior qualifying inspection, arrange a borescope inspection "within 500 flight hours after 17 January 2008" as stated in the Compliance section. If that window has already passed prior to your assessment, document corrective timing per the AD and the operator’s maintenance scheduling rules.

4. Conduct borescope inspection in accordance with PW305 MM

• Perform the inspection "in accordance with the PW305 MM 05-20-00 'Periodic Inspections, Boroscope' requirements" as required by Requirement 1.a and 2.a. Use the correct revision of the PW305 MM (Revision No.26 is referenced in the AD background as the revision that added repeat inspection intervals).
• Ensure the maintenance personnel performing the borescope inspections are competent in the MM procedure and that the borescope equipment meets the MM specifications.

5. Actions on findings

• If no cracks are found, log the inspection in accordance with maintenance record practices and schedule the next inspection at the interval mandated by the PW305 MM and the AD (not to exceed 1350 flight cycles).
• If a crack is found, comply with Requirements 1.b and 2.b: remove the engine for HPC drum rotor replacement "before further flight." Do not return the engine to service until the replacement has been effected.

6. Replacement and terminating action

• Where replacement is required or where an operator chooses to remove the recurring inspection burden, install the post-SB PW300-72-24376 assembly P/N 31B6325-01 or a later superseding P/N. The AD declares such replacement to "constitute terminating action for the inspection requirements of this AD."
• Source the replacement drum assembly via the manufacturer's SB process. Ensure all installation work is performed per the manufacturer's instructions and recorded consistent with the PW305 MM.

7. Record-keeping and evidence of compliance

• Although the AD text does not detail record-keeping requirements, retain inspection reports, MM references used, and records of any replacements performed. Documentation should specifically reference the PW305 MM sections used, the SB numbers relied upon, the P/Ns inspected or installed, and dates and times in which the inspections and replacements were performed to demonstrate compliance.

8. Coordinate logistics and contingency planning

• Anticipate potential aircraft downtime where removal is required "before further flight" and plan for engine change-out slots, availability of spare drums or engines, and costs.
• Confirm lead times and availability for P/N 31B6325-01 or later superseding P/N from Pratt & Whitney Canada or authorised distributors so that terminating action can be planned rather than forced under urgent circumstances.

9. Use the correct AD text and amendment

• Ensure the copy of the AD relied upon reflects Amendment 1 (Amdt 1) effective 10 April 2008, which corrects a typographical error in Requirement 2. Using pre-amendment versions with incorrect part numbers could lead to incorrect compliance actions.

10. Coordinate with airworthiness authority or relevant oversight if unsure

• The AD text supplied does not set out procedures for alternate means of compliance or appeals. If an operator believes an alternative inspection method or repair should be accepted as terminating action, or if there is uncertainty arising from part numbering or SB supersession, contact the relevant certificating authority or follow the authority’s established processes for approvals or deviations. The AD itself does not provide those procedures in the supplied text.

This compliance roadmap follows directly from the AD’s stated requirements: identification of affected P/Ns, borescope inspection per PW305 MM, removal of cracked drums before further flight, and replacement with P/N 31B6325-01 (or later superseding P/N) to terminate inspections. All inspection intervals and timing references in the checklist are taken from the Compliance, Requirement and Background text of the AD.