SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments using a method listed under ADDRESSES . Include “Docket No. FAA-2026-8781; Project Identifier MCAI-2024-00182-E” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this proposal because of those comments.

Except for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.

Confidential Business Information

CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this NPRM contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as “PROPIN.” The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI should be sent to Barbara Caufield, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.

Background

EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2024-0070, dated March 14, 2024 (EASA AD 2024-0070) (also referred to as the MCAI), to correct an unsafe condition on RRD Model Trent XWB-75, XWB-79, XWB-79B, and XWB-84 engines. The MCAI states that occurrences have been reported of in-service engines measuring differential oil pressures that were lower than expected. A manufacturer investigation identified a need to restrict excess oil supply to the front bearing housing bearing chamber because oil pressure could drop below the amber limit during operation at the extremes of the flight envelope. To address this potential unsafe condition, RRD developed a modification that introduced an improved oil tube assembly that re-distributes the oil flow between all bearing chambers and gearboxes, thereby increasing the overall differential oil pressure within the oil feed system. RRD also published service material with instructions for replacement of affected front bearing housing oil feed tube assemblies with the improved modification assemblies. The FAA is proposing this AD to prevent oil pressure from dropping below the safe operating range. This condition, if not addressed, could result in front bearing housing bearing chamber firing, which could lead to an engine in-flight shutdown (IFSD) or dual IFSD with consequent reduced control or loss of control of the airplane.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2026-8781.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed EASA AD 2024-0070, which specifies procedures for modification of the engine with an improved front bearing housing oil feed tube assembly. EASA AD 2024-0070 also prohibits the installation of an affected front bearing housing oil feed tube assembly on any engine. This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

FAA's Determination

These products have been approved by the civil aviation authority (CAA) of another country and are approved for operation in the United States. Pursuant to the FAA's bilateral agreement with this State of Design Authority, that authority has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing the actions specified in the MCAI, described previously, as incorporated by reference, except for any differences identified as exceptions in the regulatory text of this proposed AD.

Explanation of Required Compliance Information

In the FAA's ongoing efforts to improve the efficiency of the AD process, the FAA developed a process to use some CAA ADs as the primary source of information for compliance with requirements for corresponding FAA ADs. The FAA has been coordinating this process with manufacturers and CAAs. As a result, the FAA proposes to incorporate EASA AD 2024-0070 by reference in the FAA final rule. This proposed AD would, therefore, require compliance with EASA AD 2024-0070 in its entirety through that incorporation, except for any differences identified as exceptions in the regulatory text of this proposed AD. Using common terms that are the same as the heading of a particular section in EASA AD 2024-0070 does not mean that operators need comply only with that section. For example, where the AD requirement refers to “all required actions and compliance times,” compliance with this AD requirement is not limited to the section titled “Required Action(s) and Compliance Time(s)” in EASA AD 2024-0070. Material required by EASA AD 2024-0070 for compliance will be available at regulations.gov under Docket No. FAA-2026-8781 after the FAA final rule is published.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 80 engines installed on airplanes of U.S. registry.

The FAA estimates the following costs to comply with this proposed AD: ( printed page 53202)

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.

The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify this proposed regulation:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Would not affect intrastate aviation in Alaska, and

(3) Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

2. The FAA amends § 39.13 by adding the following new airworthiness directive:

Rolls-Royce Deutschland Ltd & Co KG: Docket No. FAA-2026-8781; Project Identifier MCAI-2024-00182-E.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by October 1, 2026.

(b) Affected ADs

None.

(c) Applicability

This AD applies to all Rolls-Royce Deutschland Ltd & Co KG Model Trent XWB-75, XWB-79, XWB-79B and XWB-84 engines.

(d) Subject

Joint Aircraft System Component (JASC) Code 7931, Engine Oil Pressure.

(e) Unsafe Condition

This AD was prompted by reports of differential oil pressures that were lower than expected on in-service engines. The FAA is issuing this AD to prevent oil pressure from dropping below the safe operating range. The unsafe condition, if not addressed, could result in front bearing housing bearing chamber firing, which could lead to an engine in-flight shutdown (IFSD) or dual IFSD with consequent reduced control or loss of control of the airplane.

(f) Compliance

Comply with this AD within the compliance times specified, unless already done.

(g) Required Actions

Except as specified in paragraphs (h) and (i) of this AD: Perform all required actions within the compliance times specified in, and in accordance with, European Union Aviation Safety Agency (EASA) EASA AD 2024-0070, dated March 14, 2024 (EASA AD 2024-0070).

(h) Exceptions to EASA AD 2024-0070

(1) Where EASA AD 2024-0070 refers to its effective date, this AD requires using the effective date of this AD.

(2) Where the service material referenced in EASA AD 2024-0070 specifies to discard certain parts, this AD requires those parts be removed from service.

(3) This AD does not adopt the “Remarks” paragraph of EASA AD 2024-0070.

(i) No Reporting Requirement

Although the material referenced in EASA AD 2024-0070 specifies to submit certain information to the manufacturer, this AD does not include that requirement.

(j) Alternative Methods of Compliance (AMOCs)

The Manager, AIR-520 Continued Operational Safety Branch, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the AIR-520 Continued Operational Safety Branch, send it to the attention of the person identified in paragraph (k) of this AD and email to: AMOC@faa.gov. Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office.

(k) Additional Information

For more information about this AD, contact Barbara Caufield, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone: (781) 238-7146; email: barbara.caufield@faa.gov.

(l) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference of the material listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) You must use this material as applicable to do the actions required by this AD, unless the AD specifies otherwise.

(i) European Union Aviation Safety Agency (EASA) AD 2024-0070, dated March 14, 2024.

(ii) [Reserved]

(3) For EASA material identified in this AD, contact EASA, Konrad-Adenauer-Ufer 3, 50668 Cologne, Germany; phone: +49 221 8999 000; email: ADs@easa.europa.eu; website: easa.europa.eu. You may find this material on the EASA website at ad.easa.europa.eu.

(4) You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 1200 District Avenue, Burlington, MA 01803. For information on the availability of this material at the FAA, call (817) 222-5110.

(5) You may view this material at the National Archives and Records Administration (NARA). For information on ( printed page 53203) the availability of this material at NARA, visit www.archives.gov/​federal-register/​cfr/​ibr-locations or email fr.inspection@nara.gov.

91 FR 53200