Airworthiness Directives; The Boeing Company Airplanes

DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 39</CFR> <DEPDOC>[Docket No. FAA-2026-0741; Project Identifier AD-2025-00817-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, and -300ER series airplanes. This proposed AD was prompted by a report of corrosion found on a satellite communications (SATCOM) high gain antenna adapter plate. This proposed AD would require repetitive inspections for corrosion of the SATCOM high gain antenna adapter plate and applicable on-condition actions. 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 March 23, 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-2026-0741; 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-2026-0741. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Stefanie Roesli, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-231-3964; email: <E T="03">stefanie.n.roesli@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-2026-0741; Project Identifier AD-2025-00817-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 Stefanie Roesli, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-231-3964; email: <E T="03">stefanie.n.roesli@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 indicating that during a heavy maintenance check on a Model 767 airplane, corrosion was found on a certain SATCOM high gain antenna adapter plate. The most severe corrosion was found at the nutplates around the edge of the adapter plate; the nutplates are used to fasten the antenna assembly to the adapter plate. Corrosion was also found at the adapter plate mounting lugs and the area around the bonding strap that is connected between the adapter plate and the airplane skin. Contributing factors that lead to an increase in risk of a parts departing airplane (PDA) event include a lack of nutplate or nutplate recess corrosion protection, lack of instructions for re-application of primer and paint, lack of maintenance inspections and repair procedures, and moisture protection appears to be inadequate for the environment. Undetected corrosion of the adapter plate could lead to a PDA event. A PDA event of the SATCOM high gain antenna adapter system could damage the primary flight control surfaces, which could result in loss of continued safe flight and landing. The SATCOM high gain antenna for Model 777 airplane has a similar adapter plate to the one installed on Model 767 airplanes. In related rulemaking, the FAA issued an NPRM, Docket No. FAA-2025-0741 (90 FR 17741), to address the unsafe condition on Model 767 airplanes. <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 777-23A0454 RB, dated May 16, 2025. This material specifies procedures for repetitive detailed inspections for corrosion of the SATCOM high gain antenna adapter plate and applicable on-condition actions. On-condition actions include repairing the SATCOM high gain antenna adapter plate or replacing it with a new or serviceable SATCOM high gain antenna adapter plate if any corrosion found is less than or equal to 0.005 inch in depth; and replacing the SATCOM high gain antenna adapter plate with a new or serviceable SATCOM high gain antenna adapter plate if any corrosion found is greater than 0.005 inch in depth. 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. For information on the procedures and compliance times, see this material at <E T="03">regulations.gov</E> under Docket No. FAA-2026-0741. <HD SOURCE="HD1">Costs of Compliance</HD> The FAA estimates that this AD, if adopted as proposed, would affect 238 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD: <GPOTABLE COLS="5" OPTS="L2,i1" CDEF="s40,r50,xs54,r50,r60"> <TTITLE>Estimated Costs</TTITLE> <CHED H="1">Action</CHED> <CHED H="1">Labor cost</CHED> <CHED H="1">Parts cost</CHED> <CHED H="1">Cost per product</CHED> <CHED H="1">Cost on U.S. operators</CHED> <ROW> <ENT I="01">Detailed inspection</ENT> <ENT>11 work-hours × $85 per hour = $935 per inspection cycle</ENT> <ENT>None</ENT> <ENT>$935 per inspection cycle</ENT> <ENT>$222,530 per inspection cycle.</ENT> </ROW> </GPOTABLE> The FAA estimates the following costs to do any necessary repairs or 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 repairs or replacements: <GPOTABLE COLS="4" OPTS="L2,i1" CDEF="s50,r50,xs60,12"> <TTITLE>On-Condition Costs</TTITLE> <CHED H="1">Action</CHED> <CHED H="1">Labor cost</CHED> <CHED H="1">Parts cost</CHED> <ENT I="01">Repair of adapter plate</ENT> <ENT>5 work-hours × $85 per hour = $425</ENT> <ENT>Negligible</ENT> <ENT>$425</ENT> </ROW> <ROW> <ENT I="01">Replacement of adapter plate</ENT> <ENT>2 work-hour × $85 per hour = $170</ENT> <ENT>$18,000</ENT> <ENT>18,170</ENT> </ROW> </GPOTABLE> <HD SOURCE="HD1">Authority for This Rulemaking</HD> 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. 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