AD/THIELERT/12 - Rail Pressure Control Valve

The AD embodies several core concepts, stated in the source text and relevant for implementation and compliance.

Applicability: The AD applies to Thielert Aircraft Engines GmbH TAE 125-02-99 engines, commercially Centurion 2.0. The AD notes that these engines are installed on multiple aircraft types under various Supplemental Type Certificates. The AD text lists Cessna 172 and Reims-built F172 (EASA STC EASA.A.S.01527), Piper PA-28 series (EASA STC EASA.A.S.01632), APEX (Robin) DR 400 (EASA STC EASA.A.S.01380) and Diamond DA 40 D, DA 42 and DA 42 M. That listing signals that the AD’s reach extends beyond bare engines to aircraft equipped under those STCs.

Mandatory hardware change: The AD requires replacement of a specific part, the rail pressure control valve P/N 05-3940-K001501, and a modification to the VRail Plug as instructed in TAE SB TM 125-1008 P1 R1.2 (Requirement 1). The Background adds that Thielert introduced a new valve P/N 05-7320-E000702; the AD requires operators to adopt that corrective hardware in line with the service bulletin.

Maintenance schedule incorporation: The AD requires amendment of the approved engine maintenance schedule to incorporate Chapter 5 “Airworthiness Limitations” of OM-02-02 Issue 1 Revision 2.3 and then to accomplish tasks within the defined thresholds and intervals set in that chapter (Requirement 2 and the ongoing Requirement 3). This converts a corrective action into a recurring maintenance obligation.

Temporal triggers and sequencing: The AD sets discrete compliance windows: 110 flight hours for the hardware change, three months for the maintenance schedule amendment, and ongoing work thereafter. The AD ties Requirement 3 explicitly to the completion of Requirements 1 and 2.

Exemptions and acceptable alternatives: The AD exempts engines whose serial numbers are already modified per TAE SB TM 125-1008 P1 R1 from Requirement 1. It also explicitly permits the use of later approved revisions of the cited documents for compliance, which creates a limited path for document-version updates without the need for separate amendment to the AD.

Safety rationale in the AD: The Background frames the directive as reaction to "occurrences and service experience" and states that failure of the valve could result in in‑flight shutdown(s). The AD therefore links recommended hardware change and maintenance practice to a safety-critical failure mode.

Regulatory cross-reference: The AD refers to EASA AD 2008-0215 (5 December 2008), indicating regulatory alignment or shared evidence basis between CASA and EASA on this safety issue. The AD was signed by a CASA delegate on 22 December 2008 and became effective on 12 February 2009.

Taken together, the main concepts are: mandatory replacement of a safety‑critical valve and modification, insertion of recurring airworthiness limitations into the approved maintenance schedule, discrete compliance deadlines and sequencing, limited exemptions by serial number, and acceptance of later approved revisions of the cited documents. The AD links all of these actions to an identified potential hazard, engine in‑flight shutdown(s), as the motivating safety concern.

The AD identifies several concrete categories of parties affected and, from the requirements, the distribution of obligations and likely cost-bearing.

Aircraft operators and engine owners: The primary legal addressees are operators and owners of aircraft fitted with the TAE 125-02-99 Centurion 2.0 engine. The AD’s mandatory replacement of P/N 05-3940-K001501 and the subsequent maintenance schedule changes are actions that owners or operators must effect on their engines within the specified compliance windows. The AD lists specific aircraft types and STCs that commonly carry these engines, which signals that owner/operators of those STC installations must review applicability to their fleet.

Maintenance organisations and licensed engineers: Maintenance providers authorised to carry out the work will perform the part replacement, VRail Plug modification and the amendment of the approved maintenance schedule. The AD references a specific Thielert service bulletin (TAE SB TM 125-1008 P1 R1.2) and the engine operator manual (OM-02-02 Chapter 5 Issue 1 Revision 2.3), so maintenance organisations will need access to and compliance with these documents. They are also responsible for correct part numbers and for implementing the modifications in accordance with the SB.

STC holders and aircraft certificants: The AD’s applicability to multiple STCs means STC holders, or organisations responsible for continuing airworthiness under those STCs, must ensure that the AD is applied to aircraft under their STC approvals. Where the AD requires maintenance schedule amendments, the entity with authority over the approved maintenance programme must adopt the specified Chapter 5 limitations.

Parts suppliers and the manufacturer: The AD’s mechanical requirement creates demand for the new rail pressure control valve P/N 05-7320-E000702 and possibly supplies for VRail Plug modification. Thielert (the manufacturer) is the originator of the service bulletin and the engine manual changes, and will be the source of the technical instructions and replacement parts.

Regulator and enforcement: The AD was issued by a CASA delegate, James Coyne, signifying regulator action. While the AD text does not describe enforcement mechanisms, the regulator is the issuing authority and will be the body that expects compliance from Australian operators.

Operators whose engines already comply: Engines with serial numbers identified in TAE SB TM 125-1008 P1 R1 are explicitly exempted from Requirement 1 because they have already incorporated the modification. Parties must consult the SB to determine whether a particular engine serial number is covered.

Who pays and who acts: The AD does not set out funding arrangements. The natural economic incidence is that owners or operators bear the direct costs of parts, labour and the administrative change to the maintenance schedule, while maintenance organisations supply labour and documentation. The AD permits use of later approved revisions of the cited documents, which gives operators and maintainers a limited choice over which revision to adopt (so long as it is an approved later revision).

Operational impact on flight operations: Because Requirement 1 must be accomplished within 110 flight hours of the AD’s effective date, operators must plan aircraft downtime and route maintenance slots accordingly. The Background indicates the action responds to potential in‑flight engine shutdown(s), so operators will need to weigh operational interruption against the safety risk identified.

In sum, the affected persons include owners/operators, maintenance organisations and licensed engineers, STC holders, parts suppliers and the regulator. The AD places immediate obligations on operators to take mechanical and administrative steps within specified windows and on maintenance organisations to carry out those steps in accordance with specified manufacturer documents.

The AD lays down specific duties for operators and maintenance organisations, and it also contains limited procedural flexibilities that could be characterised as rights to use later approved revisions and to rely on serial‑number carve‑outs.

Duties (expressed in the AD):

• Replace the rail pressure control valve P/N 05-3940-K001501 and modify the VRail Plug in accordance with TAE SB TM 125-1008 P1 R1.2 (Requirement 1). This duty is to be completed within 110 flight hours after the effective date of the AD, unless already accomplished. The AD names the exact part number to be removed and the service bulletin that prescribes the process. The Background identifies the replacement valve as P/N 05-7320-E000702, which links the required replacement to a specific corrective part produced by the manufacturer.
• Amend the approved engine maintenance schedule to incorporate the instructions of Chapter 5 “Airworthiness Limitations” of OM-02-02 Issue 1 Revision 2.3 (Requirement 2). This amendment must be done within three months after the effective date of the AD. That amendment converts particular maintenance tasks to mandatory elements of the approved schedule.
• Thereafter, accomplish the tasks within the thresholds and intervals defined in Chapter 5 “Airworthiness Limitations” of OM-02-02 Issue 1 Revision 2 (Requirement 3). The AD explicitly links the commencement of recurring tasks to the completion of the first two requirements.

Temporal sequencing: The AD imposes sequencing. Requirement 3 becomes operative only after Requirements 1 and 2 are completed. The compliance windows for Requirements 1 and 2 are distinct, 110 flight hours and three months respectively.

Exemptions and qualified non-application: Engines identified by serial number in TAE SB TM 125-1008 P1 R1 have already incorporated the modifications and therefore do not need to comply with Requirement 1. The AD therefore creates a factual test (engine serial number in the SB) that removes the hardware-change duty for already-modified engines.

Rights and flexibilities in the AD:

• The AD permits the use of later approved revisions of the referenced documents for compliance with requirements. That is, operators and maintainers may comply using later approved revisions of TAE SB TM 125-1008 and OM-02-02 insofar as those revisions are approved. This language creates a limited administrative flexibility to adopt updated manufacturer instructions without having to seek AD amendment.
• The AD does not specify penalties, nor does it specify mechanisms for granting exemptions beyond the serial number carve‑out; however, the AD’s statement that later approved revisions are acceptable is an explicit procedural flexibility.

Documentation and traceability duties (implied by the AD): While the AD does not itemise record-keeping requirements, the amendment of the approved maintenance schedule and the performance of the valve replacement and VRail Plug modification will typically require maintenance entries in the aircraft/engine logbooks, and the operator and maintenance organisation will need to demonstrate that the modifications followed the TAE service bulletin and OM-02-02 Chapter 5 instructions. The AD itself cites the documents that must be followed; adherence to those documents is the measurable standard.

Operational duties: Because the Background links valve failure to in‑flight shutdown(s), operators have an implied duty to schedule the maintenance in a manner that reduces exposure; that is implemented through the 110 flight hours and three month windows.

Delegation and decision-making: The AD was issued by a CASA delegate, James Coyne. The AD itself fixes duties on operators and maintainers; any discretion regarding alternative means of compliance, waivers or enforcement is not set out in the AD text.

In short, the AD imposes specific hardware and maintenance-programme duties tied to time windows, grants a limited exemption for pre-modified engines by serial number, and allows the use of later approved revisions of the referenced documents. The AD leaves enforcement and any additional discretion to the issuing regulator, but does not itself provide a penalty or waiver framework in the text provided.

The AD text provided does not set out express penalties, sanction mechanisms or enforcement procedures. It is a regulatory instruction issued by a CASA delegate and states mandatory performance obligations with specified compliance windows, but it does not enumerate fines, administrative sanctions or criminal penalties in the text supplied.

What the AD does show about enforcement architecture:

• Issuing authority: The AD is signed by James Coyne, identified as a Delegate of the Civil Aviation Safety Authority (CASA), dated 22 December 2008, and it became effective on 12 February 2009. The fact that the AD is issued under CASA’s authority signals that compliance will be expected within the Australian civil aviation regulatory framework administered by CASA. The AD formalises the required actions and provides the technical instruments (service bulletin and engine manual chapter) against which compliance will be measured.
• Compliance windows and mandatory character: The AD sets explicit deadlines: Requirement 1 within 110 flight hours after the effective date, and Requirement 2 within three months. These explicit time limits supply a clear standard for determining whether an operator has complied. The AD also specifies that Requirement 3 is to be accomplished after Requirements 1 and 2. The presence of those precise timings makes it administratively straightforward for a regulator or an inspector to determine compliance status.

What the AD does not state:

• The AD does not contain express statements as to the consequences of non-compliance such as monetary penalties, grounding, withdrawal of certificates, or other enforcement steps.
• The AD does not specify any process for requesting extensions, alternative methods of compliance, or exemptions (beyond the serial-number carve-out built into Requirement 1).

Practical enforcement implications derived from the AD text:

• Because the AD identifies the specific parts and service documents, an inspector or CASA can verify compliance by checking maintenance records for replacement of P/N 05-3940-K001501 and modification of the VRail Plug in accordance with TAE SB TM 125-1008 P1 R1.2, and the amendment of the approved maintenance schedule to include Chapter 5 OM-02-02 Issue 1 Rev 2.3.
• The AD’s statement that later approved revisions are acceptable provides a compliance pathway that an inspector would need to verify as "approved"; that implies the existence of an approval mechanism outside the AD text.

Where the AD is silent, parties will need to rely on CASA’s published enforcement policies and inspection procedures or to contact CASA for guidance on waivers or alternative compliance paths. The AD itself functions as a binding technical requirement; the AD text, while precise on what must be done and when, leaves enforcement remedies and administrative processes to the broader regulatory framework which is not described in the AD text provided.

The AD explicitly cross-references materials and regulatory instruments outside its own text; those references frame how operators satisfy the AD and hint at interaction with broader aviation regulatory regimes.

References to manufacturer documents: The AD requires actions "in accordance with" TAE SB TM 125-1008 P1 R1.2 and incorporation of Chapter 5 “Airworthiness Limitations” of OM-02-02 Issue 1 Revision 2.3 into the approved engine maintenance schedule. That creates an interaction between the AD and manufacturer-issued documents. Compliance with the AD is measured against those documents, and the AD permits the use of later approved revisions of those documents, establishing that the AD defers to manufacturer technical data once approved.

Cross-jurisdictional reference: The AD explicitly references EASA AD 2008-0215 dated 5 December 2008 (Note 2). This signals alignment or shared technical findings between CASA and EASA on the valve failure risk and the corrective measures. The AD thereby interacts with foreign regulator actions; operators that are subject to EASA AD 2008-0215 will likely be addressing materially similar obligations under the EASA directive.

Interaction with approved maintenance programmes and STCs: The AD requires amendment of the "approved engine maintenance schedule" to incorporate OM-02-02 Chapter 5. Approved maintenance schedules are administrative approvals maintained within the civil aviation regulatory system. The AD therefore interacts with the approval processes for maintenance programmes: whoever holds authority to maintain and to update that approved schedule must do so. The AD also lists several EASA STC numbers that identify particular STC installations on aircraft types. Those STC approvals are separate regulatory approvals, and the AD affects aircraft operated under those STCs because they carry the TAE 125-02-99 engine.

Document revision and approval process: The AD permits use of later approved revisions of the referenced documents. That creates an interaction with whatever approval mechanism governs acceptance of revised service bulletins or revised maintenance manual chapters. The requirement that revisions be "approved" means operators cannot simply adopt an unapproved revision; they must use a revision that has gained whatever approval is necessary under the applicable regulatory framework.

Serial-number-based carve-out: The exemption for engines with serial numbers identified in TAE SB TM 125-1008 P1 R1 interacts with the manufacturer’s serial-number records and the engine logbooks. Operators must rely on accurate serial-number traceability, and inspectors will verify that the serial numbers correspond to the SB list. This connects the AD to record-keeping and traceability obligations.

Absence of explicit statutory citations: The AD text does not quote or cite the specific statutory power under which CASA issued the AD. The AD does, however, operate as a binding directive from the regulator and cites the technical documents that form the compliance standard. Any legal interplay with general aviation law, safety regulations or enforcement statutes is not set out in the text provided.

In practice, compliance with this AD will require operators to coordinate with and rely upon: the manufacturer's service bulletin and manual chapters, STC approvals relevant to their installations, and potentially EASA actions if operations are international. The AD’s wording that later approved revisions are acceptable shows an interaction point where document-approval regimes intersect with AD compliance; operators will need to ensure that any revision relied upon is properly approved under the relevant regulatory approval process.

The AD itself provides several dated references and document revisions that form an internal amendment history relevant to compliance. The material in the AD shows the following sequence and references.

Issuance and effective dates: The AD is signed by James Coyne, Delegate of the Civil Aviation Safety Authority, on 22 December 2008, and the AD becomes effective on 12 February 2009. The AD identifier is AD/THIELERT/12 (2/2009), indicating its issuance in the 2/2009 batch.

Referenced manufacturer document revisions: The AD requires actions "in accordance with" TAE SB TM 125-1008 P1 R1.2 for the valve replacement and VRail Plug modification. The AD also requires amendment to incorporate Chapter 5 "Airworthiness Limitations" of OM-02-02 Issue 1 Revision 2.3, and thereafter to accomplish tasks within the thresholds and intervals defined in Chapter 5 OM-02-02 Issue 1 Revision 2. The AD therefore fixes specific revisions of manufacturer documents as the baseline for compliance: SB TM 125-1008 P1 R1.2 and OM-02-02 Issue 1 Rev 2.3 (and Chapter 5 Issue 1 Rev 2 for the recurring tasks).

Serial-number identification: The AD states that "Engines with Serial Numbers (S/N) as identified in TAE SB TM 125-1008 P1 R1 have already incorporated these modifications and therefore do not need to comply with Requirement 1 of this AD." That indicates an earlier or related revision P1 R1 of the same SB included a serial-number list; the AD therefore creates an exemption anchored to that prior SB version.

Acceptance of later revisions: The AD contains the explicit statement that "The use of later approved revisions of these documents is acceptable for compliance with the requirements of this AD." That allows for the substitution of later approved document versions without amendment to the AD, provided the later revisions are approved.

Cross-reference to EASA AD: The AD notes that EASA AD 2008-0215 dated 5 December 2008 refers. That earlier EASA AD is part of the regulatory lineage that led to CASA issuing AD/THIELERT/12. The presence of the EASA AD provides an external regulatory antecedent dated before this CASA AD’s signature date.

No further in-text amendments: The AD text provided does not include subsequent amendments, cancellations, superseding directives, or revocation language. It does not include an internal amendment log beyond the document references and dates noted above. There is no statement of later CASA revisions to AD/THIELERT/12 in the text provided.

Practical implication for compliance history: Operators and maintainers will need to consult the specified revisions of the SB and OM, check engine logbooks for serial-number exceptions noted in the SB, and then either adopt the specified revisions or any later approved revisions. If subsequent updates to the AD or to the referenced documents exist, those would have to be examined outside the AD text supplied.

In summary, the AD record within the supplied text shows issuance on 22 December 2008, an effective date of 12 February 2009, baseline references to SB TM 125-1008 P1 R1.2 and OM-02-02 Issue 1 Rev 2.3 (with Chapter 5 Issue 1 Rev 2), a serial-number list in an earlier SB revision (P1 R1) that provides an exemption, and express permission to use later approved revisions for compliance. The AD text itself does not record any amendments after its issuance in the material provided.

The AD text supplied contains no litigation history, and it does not reference any legal proceedings, appeals, or court decisions involving AD/THIELERT/12, Thielert Aircraft Engines GmbH, or affected operators. The document is an administrative directive issued by CASA and signed by a delegate; it contains no mention of litigation, disputes, or judicial review outcomes.

What the absence of litigation history in the text implies for practitioners:

• The AD does not summarise any contested legal issues or prior adjudications in its own text. Any disputes about the AD, its applicability, or enforcement actions would be dealt with in separate records, court files or regulatory proceedings which are not present in the AD as provided.
• To determine whether any litigation arose after the AD’s issuance, or whether CASA enforcement actions were contested in court, practitioners must consult external case law databases, regulator enforcement logs or administrative tribunal records. Those materials are not part of the AD text provided.

Practical notes for counsel and compliance officers:

• Because the AD sets precise technical obligations and compliance deadlines, those obligations create a factual basis for enforcement action, which could in principle become the subject of litigation or administrative challenge. The AD text itself, however, contains no record of such challenges.
• If a client needs information about any litigation that may have followed the AD’s issuance, the AD text provides the necessary identifiers (AD/THIELERT/12, effective date, parts and document references, and the name of the CASA delegate) to assist with external legal research, but the AD does not supply litigation outcomes or disputes.

In short, the supplied AD text contains no litigation history or references to legal proceedings; it is solely the regulatory directive and its technical and timing requirements.

The AD contains several operational and administrative details that are easy to mis-handle unless carefully attended to. The following are practical pitfalls and items that warrant attention, each grounded in the AD text.

Different compliance windows and sequencing: The AD imposes distinct deadlines. Requirement 1 must be completed within 110 flight hours from the effective date, whereas Requirement 2 must be completed within three months. Requirement 3 becomes operative only after Requirements 1 and 2 are completed. Failing to observe the different triggers and sequencing is a common operational error. Operators must track both calendar and flight-hour metrics and must not treat the deadlines as interchangeable.

Serial-number carve-out: The AD exempts engines with serial numbers identified in TAE SB TM 125-1008 P1 R1 from Requirement 1 because they have already incorporated the modifications. Practically, this requires precise serial-number verification against the SB’s list. Errors in reading serial numbers, relying on supplier statements without documentary proof, or using a different SB revision that lacks the serial-number list can lead to incorrect non‑compliance claims.

Part numbers and version control: The AD names the valve to be replaced as P/N 05-3940-K001501. The Background refers to a new valve P/N 05-7320-E000702 introduced by the manufacturer. Operators must ensure they remove the correct part and fit the correct replacement part. Using an incorrect replacement part P/N or failing to follow the exact SB instructions for fitting and modification risks non‑compliance or degraded safety.

Document revision reliance: The AD requires compliance "in accordance with TAE SB TM 125-1008 P1 R1.2" and OM-02-02 Issue 1 Revision 2.3 for Chapter 5. The AD also allows later approved revisions. Operators must confirm whether a later revision is approved and must be able to show that the revision used for compliance was an approved revision. Relying on an unapproved later revision or failing to document approval status is a compliance trap.

Maintenance schedule amendment mechanics: The AD requires the amendment of the "approved engine maintenance schedule" to incorporate the Chapter 5 “Airworthiness Limitations.” Practically, this requires submission and approval of a maintenance schedule change under the applicable approval process. Assuming that a mere entry in the company’s internal maintenance plan suffices without formal approval risks non‑compliance.

Record keeping and evidence: The AD does not spell out record-keeping requirements, but the tasks required (part replacement, modification, schedule amendment) must be shown in maintenance records. Failure to record the work correctly in engine logbooks or maintenance approval documents may prevent an operator from demonstrating compliance during an inspection.

Interplay with STCs and installed aircraft: The AD lists multiple STCs and aircraft types. Operators of aircraft with STC-installed engines must ensure that the AD actions are applied under the STC conditions. Assuming that compliance for the bare engine suffices without accommodating STC-specific installation differences can create gaps.

Assuming EASA compliance is sufficient: The AD notes EASA AD 2008-0215. Operators should not assume that compliance with an EASA AD automatically satisfies CASA’s AD unless the operator verifies the equivalence. The AD’s specific document-revision requirements are the controlling text for CASA compliance.

Timing from the effective date: The AD became effective on 12 February 2009. The compliance windows are measured from that effective date. Miscalculating the start date for the 110 flight‑hour or three‑month windows is a simple but consequential mistake.

Task interdependence: Requirement 3 is subject to completion of Requirements 1 and 2. Beginning recurring tasks before completing the initial hardware change and maintenance program amendment could be out of sequence with the AD’s requirements.

Maintenance organisation competence: The AD references a specific service bulletin and engine manual chapter. Ensure the maintenance organisation holds appropriate authorisations and access to the manufacturer’s SB and manuals. Attempting to perform the modifications without appropriate training or approvals could lead to ineffective or non‑compliant work.

In summary, the main "gotchas" are sequencing and timing errors, serial-number verification failures, part-number confusion, improper reliance on unapproved document revisions, failures to correctly amend and have approved maintenance schedules, poor record keeping, and assumptions about regulatory equivalence with EASA. Each of these risks is directly traceable to the AD text and its specified requirements.

Below is a practical, source-grounded compliance checklist based on the AD text and the referenced documents. The checklist is sequenced to reflect the AD’s requirements and timing, and it notes verification points that will be relevant for demonstrating compliance.

Step 1 , Confirm applicability to engine/aircraft:

• Identify whether the engine is a Thielert TAE 125-02-99 (Centurion 2.0). The AD lists common STC installations (Cessna 172/Reims F172 EASA.A.S.01527; Piper PA-28 EASA.A.S.01632; APEX Robin DR 400 EASA.A.S.01380; Diamond DA 40 D, DA 42, DA 42 M). Check aircraft logbooks and STC documentation to confirm the engine model and installation.
• Verify the engine serial number against the list in TAE SB TM 125-1008 P1 R1 to determine whether Requirement 1 is already satisfied by prior incorporation of the modification. If the engine’s S/N appears in that SB list, Requirement 1 does not apply.

Step 2 , Obtain the required documents and parts:

• Acquire TAE SB TM 125-1008 P1 R1.2 and OM-02-02 Issue 1 Revision 2.3 (Chapter 5). Confirm whether there are later approved revisions; the AD permits use of later approved revisions for compliance. Ensure that the revision(s) you rely on are approved under the applicable approval process.
• Source the replacement rail pressure control valve, as indicated in the Background (the new valve P/N 05-7320-E000702), and any parts or kits required for the VRail Plug modification as specified by the SB. Ensure the parts bear the correct part numbers.

Step 3 , Plan the work to meet timing requirements:

• Requirement 1 deadline: schedule replacement of the rail pressure control valve P/N 05-3940-K001501 and modification of the VRail Plug within 110 flight hours from the AD effective date (12 February 2009), unless already accomplished. Compute remaining flight hours and plan aircraft downtime accordingly.
• Requirement 2 deadline: schedule amendment of the approved engine maintenance schedule to incorporate Chapter 5 OM-02-02 Issue 1 Rev 2.3 within three months of the AD’s effective date. Identify the person or organisation with authority to amend the approved maintenance schedule and prepare any required submission documentation.
• Ensure Requirement 3 (recurring tasks and thresholds) will be tracked and scheduled to commence after the completion of Requirements 1 and 2.

Step 4 , Perform the hardware modification and record the work:

• Have a suitably authorised maintenance organisation or licensed engineer perform the valve replacement and VRail Plug modification strictly in accordance with TAE SB TM 125-1008 P1 R1.2 (or a later approved revision). Ensure the work card, maintenance release and logbook entries specify the part removed (P/N 05-3940-K001501), the part fitted (P/N 05-7320-E000702 where indicated), the SB revision used, and the person or organisation performing the work. Keep supporting documentation such as parts receipts and SB compliance pages.

Step 5 , Amend the approved engine maintenance schedule:

• Prepare and submit the amendment to the approved engine maintenance schedule to incorporate Chapter 5 “Airworthiness Limitations” of OM-02-02 Issue 1 Revision 2.3 within three months of the effective date. Ensure the submission follows the authority or approval process for maintenance schedule changes. Document the approval and make the amended schedule available to maintenance personnel.

Step 6 , Implement ongoing tasks and interval tracking:

• After completing Requirements 1 and 2, execute the recurring tasks, inspections, and replacements in accordance with the thresholds and intervals defined in Chapter 5 OM-02-02 Issue 1 Revision 2. (Requirement 3). Establish or update maintenance tracking and scheduling systems to capture the intervals and thresholds. Ensure that personnel understand when the recurring tasks are due relative to the date or hours dates established by the amended maintenance schedule.

Step 7 , Maintain traceable records and evidence of compliance:

• Record in the engine and aircraft logbooks the completion of the SB-mandated modification, including SB number and revision, parts removed/installed (with part numbers and serial numbers), dates, and sign-off by the authorised maintenance organisation or licensed engineer. Maintain copies of the amended approved maintenance schedule and evidence of its approval. Retain all supporting documentation to demonstrate compliance during any inspection.

Step 8 , If relying on exemptions or later revisions, document approval authority:

• If claiming the serial-number exemption for Requirement 1, retain the SB pages showing the relevant serial-number list and any supporting evidence that the engine serial number is included.
• If using a later revision of the SB or OM, ensure and document that the later revision was approved for compliance, and record the approval authority and approval date.

Step 9 , Coordinate with any STC holders and relevant authorities:

• Where the engine is installation‑specific under an STC, liaise with the STC holder or continuing airworthiness authority to ensure the modifications are compatible with the STC conditions and that the aircraft-level maintenance schedule reflects the engine maintenance schedule changes. Notify CASA or the relevant authority where local approval processes require notification of AD compliance.

Step 10 , Safety and operational planning:

• Given the Background’s statement that failure of the valve could result in in‑flight shutdown(s), factor the maintenance into flight operation planning in a way that minimises exposure. Plan ferry flights, if required, in accordance with applicable operational authority guidance and with full awareness of the AD timing.

Step 11 , Seek regulatory clarification if necessary:

• The AD does not provide penalty or waiver procedures in the text supplied. If an operator needs an extension, an alternative method of compliance, or clarification about approval of document revisions, they should contact CASA or the relevant approving authority to obtain formal guidance or approval before relying on any deviation from the AD text.

By following this sequence and maintaining documentary evidence at each step, operators can align their physical works and administrative approvals to the specific requirements and timelines stated in AD/THIELERT/12. All actions must be carried out "in accordance with" the specified service bulletin and operation & maintenance manual chapters, or later approved revisions, and recorded in the engine and aircraft maintenance records.