2026-13869: Airworthiness Directives; The Boeing Company Airplanes

Federal Register, Volume 91 Issue 130 (Thursday, July 9, 2026) [Federal Register Volume 91, Number 130 (Thursday, July 9, 2026)] [Proposed Rules] [Pages 42387-42390] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 2026-13869] [[Page 42387]] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. FAA-2026-7215; Project Identifier AD-2025-01558-T] RIN 2120-AA64 Airworthiness Directives; The Boeing Company Airplanes

Agency

Federal Aviation Administration (FAA), DOT.

Action

Notice of proposed rulemaking (NPRM). -----------------------------------------------------------------------

Summary

The FAA proposes to supersede Airworthiness Directive (AD) 2023-07-09, which applies to certain The Boeing Company Model 747-400 and -8 series airplanes. AD 2023-07-09 requires inspecting for wear of the transfer pump housing inlet check valves and transfer pump motor impeller inlet adapters for the horizontal stabilizer fuel tank and doing corrective actions, if necessary, and limits the installation of affected parts. Since the FAA issued AD 2023-07-09, the manufacturer has developed further action to address the unsafe condition. This proposed AD would require repetitive inspections for damage of the transfer pump housing inlet check valves and transfer pump motor impeller inlet adapters for the horizontal stabilizer fuel tank and applicable on-condition actions. This proposed AD would also limit the installation of affected parts under certain conditions. The FAA is proposing this AD to address the unsafe condition on these products.

Dates

The FAA must receive comments on this proposed AD by August 24, 2026.

Addresses

You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods: Federal eRulemaking Portal: Go to regulations.gov. Follow the instructions for submitting comments. Fax: 202-493-2251. Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590. Hand Delivery: Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. AD Docket: You may examine the AD docket at regulations.gov under Docket No. FAA-2026-7215; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this NPRM, any comments received, and other information. The street address for Docket Operations is listed above. Material Incorporated by Reference: For Boeing material identified in this proposed 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. 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. It is also available at regulations.gov under Docket No. FAA-2026-7215.

For Further Information Contact

Samuel Dorsey, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206- 231-3415; email: [email protected].

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 the ADDRESSES section. Include ``Docket No. FAA-2026-7215; Project Identifier AD-2025-01558-T'' 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 Samuel Dorsey, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-231-3415; email: [email protected]. Any commentary that the FAA receives that is not specifically designated as CBI will be placed in the public docket for this rulemaking. Background The FAA issued AD 2023-07-09, Amendment 39-22411 (88 FR 22895, April 14, 2023) (AD 2023-07-09), for certain Model 747-400 and -8 series airplanes. AD 2023-07-09 was prompted by reports of wear-through of the transfer pump motor impeller inlet adapter of the horizontal stabilizer fuel tank transfer pump caused by contact between the transfer pump housing inlet check valve and the inlet adapter. AD 2023- 07-09 requires inspecting for wear of the transfer pump housing inlet check valves and transfer pump motor impeller inlet adapters for the horizontal stabilizer fuel tank and doing corrective actions, if necessary, and limits the installation of affected parts. The agency issued AD 2023-07-09 to address the development of an ignition source within the horizontal stabilizer fuel tank resulting from wear to the transfer pump housing inlet check valves and transfer pump motor impeller inlet adapters of the horizontal stabilizer fuel tank. This condition, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane. Actions Since AD 2023-07-09 Was Issued The preamble to AD 2023-07-09 specifies that the FAA considers that AD to be an interim action and that the FAA might consider further rulemaking if final action is identified. Since the FAA issued AD 2023- 07-09, the manufacturer has developed final action to address the unsafe condition, and the FAA has determined that further rulemaking is necessary. The proposed AD would replace the one-time inspections required by AD 2023-07-09 with repetitive inspections. [[Page 42388]] The repeat intervals for these inspections are based upon analysis of reports submitted to the manufacturer following the issuance of AD 2023-07-09. Inspection of the transfer pump housing inlet check valve is proposed to be required in intervals not to exceed 20,000 flight hours. Notably different from AD 2023-07-09, the proposed AD would require an initial inspection of the transfer pump motor impeller inlet adapter within 1 year or 5,000 flight hours, whichever occurs first, and would not allow any level of wear to the inlet adapter. This inspection would be required to be repeated in intervals not to exceed 20,000 flight hours thereafter. The proposed AD would also remove the 0.20-inch wear allowance for the transfer pump motor impeller inlet adapter. When the FAA issued AD 2023-07-09, up to 0.20-inch of wear to the transfer pump motor impeller inlet adapter was permitted as an operational consideration due to that depth of wear being safe for the immediate future, the number of affected pumps, and the need for a short compliance time. Because of this allowance, the present level of wear across the fleet is uncertain, as some operators may have repaired pumps with any wear, while others may have returned pumps to service just below the wear limit. This, combined with uncertainty in the rate of wear progression determined from AD 2023-07-09 reports and subsequent analysis by the manufacturer, necessitate an accelerated initial inspection as specified in Boeing Alert Requirements Bulletin 747-28A2373 RB, dated November 6, 2025, for this proposed AD. Therefore, the FAA and manufacturer have reduced the initial compliance time for the transfer pump motor impeller inlet adapter inspection relative to the repeat interval. The FAA believes this initial compliance time to be practical because the transfer pumps are designed to be removed without defueling or purging the horizontal stabilizer fuel tank. Additionally, due to the need for an operationally feasible repeat interval with multiple opportunities to detect damage prior to any wear reaching a critical level, the FAA considers it necessary to remove the acceptable damage allowance previously provided under AD 2023-07-09 for transfer pump motor impeller inlet adapters, as retaining the acceptable damage allowance would require a shortened repeat interval to ensure detection of unacceptable wear prior to reaching a critical level. This action will ensure that transfer pumps installed in the horizontal stabilizer fuel tank remain at a safe level of wear between inspection opportunities. FAA's Determination 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. Material Incorporated by Reference Under 1 CFR Part 51 The FAA reviewed Boeing Alert Requirements Bulletin 747-28A2373 RB, dated November 6, 2025. This material specifies procedures for repetitive detailed inspections of the transfer pump housing inlet check valves and transfer pump motor impeller inlet adapters for any damage and applicable on-condition actions. On-condition actions include replacing the damaged transfer pump housing inlet check valve with a new or serviceable transfer pump housing inlet check valve (Option 1), or replacing the affected transfer pump housing with a transfer pump housing containing a new or serviceable transfer pump housing inlet check valve (Option 2); and replacing an affected transfer pump motor impeller with a new or serviceable transfer pump motor impeller. 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. Proposed AD Requirements in This NPRM This proposed AD would require accomplishing the actions specified in the material already described, except for any differences identified as exceptions in the regulatory text of this proposed AD. This proposed AD would also limit the installation of affected parts. For information on the procedures and compliance times, see this material at regulations.gov under Docket No. FAA-2026-7215. Interim Action The FAA considers that this proposed AD would be an interim action. The main and center wing tanks utilize the same pump design but are currently not subject to the same unsafe condition due to the shutoff logic of the pumps. However, if further analysis or reports related to the main or center tank pumps change this assessment, the FAA might consider further rulemaking for those tanks. Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 31 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD: Estimated Costs ---------------------------------------------------------------------------------------------------------------- Cost on U.S. Action Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Inspection of transfer pump 18 work-hours x $85 $0 $1,530 per $47,430 per housing inlet check valve (2 per per hour = $1,530 inspection cycle. inspection cycle. airplane). per inspection cycle. Inspection of transfer pump motor 18 work-hours x $85 0 $1,530 per $47,430 per impeller inlet adapter (2 per per hour = $1,530 inspection cycle. inspection cycle. airplane). per inspection cycle. ---------------------------------------------------------------------------------------------------------------- * * * * * The FAA estimates the following costs to do any necessary replacements that would be required based on the results of the proposed inspection. The agency has no way of determining the number of aircraft that might need these replacements: On-Condition Costs ---------------------------------------------------------------------------------------------------------------- Action Labor cost Parts cost Cost per product ---------------------------------------------------------------------------------------------------------------- Replacement of transfer pump motor 2 work-hours x $85 per Up to $2,400........... $2,570. impeller. hour = $170. Replacement of transfer pump housing 2 work-hours x $85 per $1,800................. $1,970. inlet check valve (Option 1). hour = $170. [[Page 42389]] Replacement of transfer pump housing 2 work-hours x $85 per Up to $20,000.......... Up to $20,170. (Option 2). hour = $170. ---------------------------------------------------------------------------------------------------------------- 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. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. The Proposed Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows: PART 39--AIRWORTHINESS DIRECTIVES 0