SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2023-08-04, Amendment 39-22419 (88 FR 33823, May 25, 2023) (AD 2023-08-04). AD 2023-08-04 applied to certain The Boeing Company Model 787-8, 787-9, and 787-10 airplanes. The NPRM was published in the Federal Register on July 3, 2025 (90 FR 29512). The NPRM was prompted by reports of a loss of water pressure during flight and water leaks that affected multiple pieces of electronic equipment. In the NPRM, the FAA proposed to continue to retain the requirements of AD 2023-08-04 and require, for certain airplanes, a detailed inspection of all clamshell couplings for the presence and correct installation of safety straps at door 1 and door 3 lavatories and galleys with a potable water system and applicable on-condition actions, which would terminate the existing requirements. Additionally, Model 787-10 airplanes were included in the applicability of the NPRM to prevent the installation of affected parts on Model 787-10 airplanes as required by the Parts Installation Prohibition paragraph of this AD. The FAA is issuing this AD to prevent the unsafe condition, which, if not addressed, could lead to water leaks and water migration to critical flight equipment, which may affect the continued safe flight and landing of the airplane.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from the Air Line Pilots Association, International (ALPA), and United Airlines who supported the NPRM without change.

The FAA received additional comments from Boeing, Turkish Airlines (THY), Kenya Airlines, an individual commenter, and The Foundation for Aviation Safety. The following presents the comments received on the NPRM and the FAA's response to each comment.

Request for Clarification on Applicability

Boeing requested clarification on why Model 787-10 airplanes were included in the applicability of the proposed AD. Boeing stated that the Background section of the proposed AD includes Model 787-10 airplanes, although the applicability of Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025, is limited to the Model 787-8 and 787-9 airplanes. Boeing noted that revising the Background section to explain that Model 787-10 airplanes were included because of the Parts Installation Prohibition paragraph would avoid confusion.

The FAA agrees to clarify. This AD retains the requirements of paragraph (g) of AD 2023-08-04, which incorporates by reference (IBR) Boeing Alert Requirements Bulletin B787-81205-SB380021-00 RB, Issue 001, dated August 12, 2022, which applies to Boeing Model 787-8, 787-9, and 787-10 airplanes. In addition, some Model 787-10 airplanes may not have been inspected as required by AD 2023-08-04; therefore, the Parts Installation Prohibition paragraph in this AD also applies to Model 787-10 airplanes. For these reasons, the Background section of this AD has been revised to clarify that Model 787-10 airplanes are included because of the Parts Installation Prohibition requirement of this AD.

Request To Revise Listed Part Numbers

Turkish Airlines requested the FAA revise the Parts Installation Prohibition paragraph in the proposed AD that prohibits installation of (P/N) 14C02-08C or P/N AS1655A08. Turkish Airlines explained that P/N AS1655A08 is listed in THY illustrated parts data (IPD) 38-10-01-10 as the specification number for P/N 14C02-08A, and therefore it would be applicable to all THY Model 787 airplanes. ( printed page 23006)

The FAA agrees and has revised the Parts Installation Prohibition paragraph in this AD to identify these part numbers as “P/N 14C02-08C (AS1655C08)” and “P/N 14C02-08A (AS1655A08)”.

Request for Clarification on Applicability and Parts Installation Prohibition Requirements

Turkish Airlines requested clarification on whether the replacement required by the Parts Installation Prohibition paragraph in the proposed AD would apply to its fleet, given that Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025, is not applicable to Turkish Airlines. Turkish Airlines also requested clarification on whether it would be required to perform any actions specified in the Parts Installation Prohibition paragraph for airplanes that are not included in the Effectivity of Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025.

The FAA provides the following clarification. The Parts Installation Prohibition paragraph does not describe an action; rather, it prohibits installation of affected part numbers in locations where they have been replaced with approved part numbers. The Parts Installation Prohibition paragraph applies to all airplanes identified in the Applicability paragraph of this AD. Therefore, the Parts Installation Prohibition paragraph of this AD applies to any Turkish Airlines airplanes included in the Applicability paragraph of this AD, even if those airplanes are not listed in the Effectivity of Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025.

Request for Credit for Previous Actions

Kenya Airways requested the FAA include an additional paragraph in the NPRM to provide credit for the actions required by the New Required Actions paragraph if those actions were performed before the effective date of this AD using Boeing Alert Service Bulletin B787-81205-SB250299-00 RB, Issue 001, dated July 31, 2023. Kenya stated that it has accomplished Boeing Alert Service Bulletin B787-81205-SB250299-00 RB, Issue 001, dated July 31, 2023, on some of its airplanes, and therefore requested credit for those completed actions.

The FAA disagrees with the request. Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 001, dated July 31, 2023, omits certain inspection locations. As a result, Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 001, dated July 31, 2023, does not fully address the unsafe condition, and therefore cannot be credited. No changes have been made to this AD in this regard.

Request To Clarify the Parts Installation Prohibition Paragraph

An individual commenter requested the FAA confirm the correct part number referenced as “P/N 14C33-08” in paragraph (m) of the proposed AD. The commenter noted that the listed part number is inconsistent with Boeing documentation and industry parts catalogs, which list “P/N 14C34-08C”. The commenter also requested clarification that the parts installation prohibition applies only to new installations and that properly installed units may remain in service until the next scheduled replacement. The commenter stated that paragraph (m) prohibits installation of P/N 14C02-08C and P/N AS1655A08 at affected locations but does not distinguish between existing and new installations.

The FAA provides the following clarification. The Parts Installation Prohibition paragraph in this AD has been revised as described previously. Both P/N 14C34-08C and P/N 14C33-08 are valid replacement parts; therefore, P/N 14C02-08C (AS1655C08) or P/N 14C02-08A (AS1655A08) may be replaced with either P/N 14C34-08C or P/N 14C33-08. Additionally, paragraph (m) of this AD specifies that the prohibited part numbers cannot be installed in locations where they have been replaced with valid part numbers, indicating that the parts installation prohibition only applies to new installations where the affected parts have already been replaced with P/N 14C34-08C or P/N 14C33-08.

Request To Define Inspection Locations

An individual commenter requested the FAA define the term “inspection locations” as the clamshell coupling points at door 1 and door 3 lavatories and galleys and include a note or diagram to that effect. The commenter stated that the term was not defined in the regulatory text of the proposed AD and could be misconstrued to include all potable-water system fittings.

The FAA disagrees with the request. The inspection locations are defined in Table 5 of Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025. Table 5 instructs operators to “Do a Detailed Inspection (DET) of all clamshell couplings at Door 1 and Door 3 lavatories and galleys with potable water system for a safety strap and that clamshell coupling with a safety strap is correctly installed.” Therefore, the inspection locations are already defined in the referenced service information. No changes have been made to this AD in this regard.

Request To Consolidate Cross-Referenced Documents

An individual commenter requested the FAA provide a consolidated compliance table within the regulatory text or as a standalone matrix in the proposed AD. The commenter stated that the proposed AD incorporated six separate service documents with distinct information that could be technically misinterpreted.

The FAA disagrees that the quantity of service documents referenced in this AD will lead to technical misinterpretation. The issue dates of each referenced service document are identified in this AD. The FAA has determined that the current structure of this AD provides the most accurate and enforceable method for identifying the required actions. No changes have been made to this AD in this regard.

Request for Broader Action To Address Water Intrusion Issues

The FAA received a comment from the Foundation for Aviation Safety asking how many additional water intrusion issues might occur as the airplane ages and what the FAA is doing to ensure that Boeing maintains manufacturing quality to prevent leaks. The Foundation for Aviation Safety also suggested that all affected airplanes be inspected and undergo leak detection testing rather than waiting for electrical or electronic failures.

The FAA acknowledges the commenter's concerns. However, the questions and suggestions provided are general in nature and are not specific to the unsafe condition addressed in this AD. Broader concerns regarding potential future water intrusion issues and fleetwide leak detection testing are outside the scope of this AD. Therefore, no changes have been made to this AD in this regard.

Conclusion

The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator. ( printed page 23007)

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025. This material specifies procedures for a detailed inspection for the presence and correct installation of safety straps at the clamshell couplings at door 1 and door 3 lavatories and galleys with a potable water system. The material also specifies applicable on-condition actions including correcting the installation of the safety strap, replacing any clamshell coupling that does not have a strap with a new clamshell coupling that has a safety strap, and performing a water leak test.

This AD also requires Boeing Alert Requirements Bulletin B787-81205-SB380021-00 RB, Issue 001, dated August 12, 2022, which the Director of the Federal Register approved for incorporation by reference as of June 29, 2023 (88 FR 33823, May 25, 2023).

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.

Costs of Compliance

The FAA estimates that this AD affects 165 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:

The FAA estimates the following costs to do any on-condition actions that would be required based on the results of the inspections. The agency has no way of determining the number of aircraft that might need these actions:

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

This AD will not have federalism implications under Executive Order 13132. This AD will 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 that this AD:

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

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

(3) Will 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 Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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:

a. Removing Airworthiness Directive (AD) 2023-08-04, Amendment 39-22419 ( 88 FR 33823, May 25, 2023); and

b. Adding the following new AD:

2026-09-01 The Boeing Company: Amendment 39-23321; Docket No. FAA-2025-1114; Project Identifier AD-2025-00314-T.

(a) Effective Date

This airworthiness directive (AD) is effective June 3, 2026.

(b) Affected ADs

This AD replaces AD 2023-08-04, Amendment 39-22419 (88 FR 33823, May 25, 2023) (AD 2023-08-04).

(c) Applicability

This AD applies to The Boeing Company Model 787-8, 787-9, and 787-10 airplanes, certificated in any category, as specified in Boeing Alert Requirements Bulletin B787-81205-SB380021-00 RB, Issue 001, dated August 12, 2022.

(d) Subject

Air Transport Association (ATA) of America Code 38, Water/waste.

(e) Unsafe Condition

This AD was prompted by reports of a loss of water pressure during flight and water leaks that affected multiple pieces of ( printed page 23008) electronic equipment, and by the determination that some clamshell couplings for certain lavatory and galley doors did not have a required safety strap. The FAA is issuing this AD to prevent the unsafe condition, which, if not addressed, could lead to water leaks and water migration to critical flight equipment, which may affect the continued safe flight and landing of the airplane.

(f) Compliance

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

(g) Retained Clamshell Coupling Inspection, With No Changes

This paragraph restates the requirements of paragraph (g) of AD 2023-08-04, with no changes. Except as specified by paragraph (h) of this AD: At the applicable times specified in the “Compliance” paragraph of Boeing Alert Requirements Bulletin B787-81205-SB380021-00 RB, Issue 001, dated August 12, 2022, do all applicable actions identified in, and in accordance with, the Accomplishment Instructions of Boeing Alert Requirements Bulletin B787-81205-SB380021-00 RB, Issue 001, dated August 12, 2022.

Note 1 to paragraph (g): Guidance for accomplishing the actions required by paragraph (g) of this AD can be found in Boeing Alert Service Bulletin B787-81205-SB380021-00, Issue 001, dated August 12, 2022, which is referred to in Boeing Alert Requirements Bulletin B787-81205-SB380021-00 RB, Issue 001, dated August 12, 2022.

(h) Retained Exception to Service Information Specifications, With No Changes

This paragraph restates the exception of paragraph (h) of AD 2023-08-04, with no changes. Where the Compliance Time columns of the table in the “Compliance” paragraph of Boeing Alert Requirements Bulletin B787-81205-SB380021-00 RB, Issue 001, dated August 12, 2022, refer to the Issue 001 date of Requirements Bulletin B787-81205-SB380021-00 RB, this AD requires using June 29, 2023 (the effective date of AD 2023-08-04).

(i) Retained Credit for Previous Actions, With No Changes

This paragraph restates the provisions of paragraph (i) of AD 2023-08-04, with no changes. This paragraph provides credit for the actions specified in paragraph (g) of this AD, if those actions were performed before June 29, 2023 (the effective date of AD 2023-08-04), using Multi Operator Message MOM-MOM-21-0554-01B, dated December 14, 2021 (for lavatory inspections); and MOM-MOM-22-0229-01B, dated April 29, 2022 (for galley inspections).

(j) New Required Actions

For airplanes identified in Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025: Except as specified by paragraph (k) of this AD, at the applicable times specified in the “Compliance” paragraph of Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025, do all applicable actions identified in, and in accordance with, the Accomplishment Instructions of Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025.

Note 2 to paragraph (j): Guidance for accomplishing the actions required by paragraph (j) of this AD can be found in Boeing Alert Service Bulletin B787-81205-SB250299-00, Issue 002, dated February 28, 2025, which is referred to in Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025.

(k) New Exception to Service Information Specifications

Where the Compliance Time column of the table in the “Compliance” paragraph of Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025, uses the phrase “the Issue 001 date of Requirements Bulletin B787-81205-SB250299-00 RB,” this AD requires using the effective date of this AD.

(l) Terminating Action for Clamshell Coupling Inspection

For the airplanes identified in Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025: Accomplishment of the actions required by paragraph (j) of this AD terminates the requirements of paragraph (g) of this AD.

(m) Parts Installation Prohibition

As of the effective date of this AD, no person may install a clamshell coupling, part number (P/N) 14C02-08C (AS1655C08) or P/N 14C02-08A (AS1655A08), at inspection locations where P/N 14C02-08C (AS1655C08) or P/N 14C02-08A (AS1655A08) was replaced with P/N 14C34-08C or P/N 14C33-08 on any airplane.

(n) Alternative Methods of Compliance (AMOCs)

(1) 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 responsible Flight Standards Office, as appropriate. If sending information directly to the manager of the Continued Operational Safety Branch, send it to the attention of the person identified in paragraph (o)(1) of this AD. Information may be emailed to: AMOC@faa.gov. Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the responsible Flight Standards Office.

(2) An AMOC that provides an acceptable level of safety may be used for any repair, modification, or alteration required by this AD if it is approved by The Boeing Company Organization Designation Authorization (ODA) that has been authorized by the Manager, AIR-520, Continued Operational Safety Branch, FAA, to make those findings. To be approved, the repair method, modification deviation, or alteration deviation must meet the certification basis of the airplane, and the approval must specifically refer to this AD.

(o) Additional Information

(1) For more information about this AD, contact Joshua Baek, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 562-627-6725; email: joshua.y.baek@faa.gov.

(2) Material identified in this AD that is not incorporated by reference is available at the address specified in paragraph (p)(5) of this AD.

(p) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference (IBR) 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 this AD specifies otherwise.

(3) The following material was approved for IBR on June 3, 2026.

(i) Boeing Alert Requirements Bulletin B787-81205-SB250299-00 RB, Issue 002, dated February 28, 2025.

(ii) [Reserved]

(4) The following material was approved for IBR on June 29, 2023 (88 FR 33823, May 25, 2023).

(i) Boeing Alert Requirements Bulletin B787-81205-SB380021-00 RB, Issue 001, dated August 12, 2022.

(ii) [Reserved]

(5) For Boeing material identified in this AD, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone 562-797-1717; website myboeingfleet.com.

(6) You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195.

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

91 FR 23005