Airworthiness Directives; The Boeing Company Airplanes

DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 39</CFR> <DEPDOC>[Docket No. FAA-2025-3997; Project Identifier AD-2025-01471-T]</DEPDOC> <RIN>RIN 2120-AA64</RIN> <SUBJECT>Airworthiness Directives; The Boeing Company Airplanes</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Notice of proposed rulemaking (NPRM). <SUM> <HD SOURCE="HED">SUMMARY:</HD> The FAA proposes to adopt a new airworthiness directive (AD) for all The Boeing Company Model 777-200, -200LR, -300, -300ER, and 777F series airplanes. This proposed AD was prompted by a report of overheated alternating current motor pumps (ACMP) that caused a fire in the main landing gear (MLG) wheel well. This proposed AD would require a records check or inspection for any installed ACMP with a certain part number and applicable on-condition actions. This proposed AD would also prohibit the installation of affected parts. The FAA is proposing this AD to address the unsafe condition on these products. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> The FAA must receive comments on this proposed AD by January 2, 2026. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods: • <E T="03">Federal eRulemaking Portal:</E> Go to <E T="03">regulations.gov.</E> Follow the instructions for submitting comments. • <E T="03">Fax:</E> 202-493-2251. • <E T="03">Mail:</E> U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590. • <E T="03">Hand Delivery:</E> Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. <E T="03">AD Docket:</E> You may examine the AD docket at <E T="03">regulations.gov</E> under Docket No. FAA-2025-3997; 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. <E T="03">Material Incorporated by Reference:</E> • 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 <E T="03">myboeingfleet.com.</E> • 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 <E T="03">regulations.gov</E> under Docket No. FAA-2025-3997. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Michael Sheldon, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 651-955-7451; email: <E T="03">michael.e.sheldon@faa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Comments Invited</HD> 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 <E T="02">ADDRESSES</E> section. Include “Docket No. FAA-2025-3997; Project Identifier AD-2025-01471-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 <E T="03">regulations.gov,</E> including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM. <HD SOURCE="HD1">Confidential Business Information</HD> 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 Michael Sheldon, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 651-955-7451; email: <E T="03">michael.e.sheldon@faa.gov.</E> Any commentary that the FAA receives that is not specifically designated as CBI will be placed in the public docket for this rulemaking. <HD SOURCE="HD1">Background</HD> The FAA has received a report from an operator of a fire in the MLG wheel well on a Model 777 airplane. A subsequent investigation found that the cause of the fire was an overheated ACMP. Further investigation found that a lock washer and nut was missing from a moving contact in the related electrical load control unit (ELCU). The missing lock washer and nut left the main contact operator bar unrestrained and in a position which let two-phase power go to the ACMP which caused the ACMP to overheat, leak hydraulic fluid and subsequently start a fire in the MLG wheel well. As a result, the design of the ACMP has been modified to include fusible links as a new feature to prevent the ACMP overheat if one of the electrical phases fails. Additionally, the manufacturer has determined that part number 731966 on continuous two-phase power application may cause the pump to overheat and ignite a fire in the wheel well. Part number 731966 can be subjected to a single failure of the ELCU that results in continuous two-phase power application with no ability to remove power. This condition, if not addressed, could result in the ACMP overheating and igniting a fire in the wheel well and consequent damage to the airplane, loss of continued safe flight and landing and/or personnel injury. <HD SOURCE="HD1">FAA's Determination</HD> 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. <HD SOURCE="HD1">Material Incorporated by Reference Under 1 CFR Part 51</HD> The FAA reviewed Boeing Alert Requirements Bulletin 777-29A0047 RB, dated September 11, 2025. This material specifies procedures for a records check or inspection for any installed ACMP with part number 731966, and applicable on-condition actions. On-condition actions include replacing any ACMP part number 731966 with ACMP part number 3033115-100 or later approved ACMP part number at affected locations. 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 <E T="02">ADDRESSES</E> section. <HD SOURCE="HD1">Proposed AD Requirements in This NPRM</HD> 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 prohibit the installation of affected parts. For information on the procedures and compliance times, see this material at <E T="03">regulations.gov</E> under Docket No. FAA-2025-3997. <HD SOURCE="HD1">Differences Between This Proposed AD and the Referenced Material</HD> The effectivity of Boeing Alert Requirements Bulletin 777-29A0047 RB, dated September 11, 2025, is limited to The Boeing Company Model 777-200, -200LR,-300, -300ER, and 777F series airplanes having line numbers 1 through 1566 inclusive, and 1568 through 1571 inclusive. However, the applicability of this proposed AD includes all Model 777-200, -200LR, -300, -300ER, and 777F series airplanes. Because the affected ACMP are rotable parts, the FAA has determined that these parts could later be installed on airplanes that were initially delivered with acceptable ACMPs, thereby subjecting those airplanes to the unsafe condition. The FAA has confirmed that the Accomplishment Instructions in Boeing Alert Requirements Bulletin 777-29A0047 RB, dated September 11, 2025, are applicable to the expanded group of airplanes. Boeing Alert Requirements Bulletin 777-29A0047 RB, dated September 11, 2025, refers to ACMP part number 3033115-100 as an acceptable part. However, the Boeing aircraft maintenance manual (AMM) identifies part numbers 66133-06 or 66068-08 as additional acceptable parts. Accordingly, the FAA has added paragraph (h)(2) to this proposed AD to allow those parts as alternative replacement parts. <HD SOURCE="HD1">Costs of Compliance</HD> The FAA estimates that this AD, if adopted as proposed, would affect 340 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD: <GPOTABLE COLS="5" OPTS="L2,i1" CDEF="s50,r50,12,12,12"> <TTITLE>Estimated Costs</TTITLE> <CHED H="1">Action</CHED> <CHED H="1">Labor cost</CHED> <CHED H="1">Parts cost</CHED> Cost on U.S. operators </CHED> <ROW> <ENT I="01">Inspection/Records review</ENT> <ENT>2 work-hours × $85 per hour = $170</ENT> <ENT>$0</ENT> <ENT>$170</ENT> <ENT>$57,800</ENT> </ROW> </GPOTABLE> The FAA estimates the following costs to do any ne ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 19k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━