Airworthiness Directives; The Boeing Company Airplanes

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2024-2144; Project Identifier AD-2024-00424-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 Raja Vengadasalam, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-231-3859; email: raja.vengadasalam@faa.gov. 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 2022-15-06, Amendment 39-22126 (87 FR 47334, August 3, 2022) (AD 2022-15-06), for all The Boeing Company Model 777-200, -200LR, -300, -300ER, and 777F series airplanes. AD 2022-15-06 was prompted by high electrical resistance within the gust suppression sensor (GSS) transorb modules due to corrosion on the transorb threads. AD 2022-15-06 requires disconnecting certain connectors and capping and stowing the wires that had been attached to the affected transorb modules. The FAA issued AD 2022-15-06 to address high electrical resistance in both transorb modules, which can result in two actuator control electronics (ACEs) being exposed to damaging lightning transient voltages in excess of the qualification levels, potentially inducing erroneous or oscillatory outputs to flight control surfaces. The unsafe condition, if not addressed, could result in loss of control of the airplane.

Actions Since AD 2022-15-06 Was Issued

Since the FAA issued AD 2022-15-06, a replacement mitigating action has been developed to address the unsafe condition, which would terminate the existing actions. The preamble to AD 2022-15-06 explains that the FAA considers the requirements “interim action” and may consider further rulemaking. The FAA has now determined that further rulemaking is indeed necessary, and the replacement specified in this proposed AD follows from that determination.

In addition, Boeing and several operators notified the FAA that certain bundles/connectors were not identified in AD 2022-15-06. Boeing noted that there are connector designation variances between earlier and later Model 777 airplanes and that bundle/connector W7314/D02099P is on the right-hand side of certain line number airplanes. Boeing stated it sent a Boeing multi-operator message to operators to reduce confusion and recommended bundle/connector W7314/D02099P be identified as an affected bundle/connector. American Airlines, Qatar Airways, and United Airlines also noted that bundle/connector W7314/D02099P is not identified in AD 2022-15-06. United Airlines, All Nippon Airways, and Kilitta Air, LLC, noted that bundle/connector W6313/D02098P is not identified in AD 2022-15-06 but it is identified as a bundle/connector for certain airplanes.

The FAA has determined the additional connectors are affected by the unsafe condition. Therefore, this proposed AD would require that operators disconnect the connectors and cap and stow the wires to bundles/connectors W6313/D02098P and W7314/D02099P until the proposed replacement is done as specified in paragraph (h) of this proposed AD.

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 777-27A0125 RB, dated February 3, 2023. This material specifies procedures for replacing affected transorb modules with new or serviceable transorb modules or testing affected transorb modules and accomplishing applicable on-condition actions. The on-condition actions include part marking any module that meets certain specifications or replacing any modules that do not meet the specifications.

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 retain all requirements of AD 2022-15-06 and would require those actions for additional connectors. This proposed AD would also require determining if affected transorb modules are installed, replacing or testing affected transorb modules, and applicable on-condition actions. This proposed AD would also prohibit the installation of affected parts.

For information on the procedures and compliance times, see Boeing Alert Requirements Bulletin 777-27A0125 RB, dated February 3, 2023, at regulations.gov under Docket No. FAA-2024-2144.

Differences Between This Proposed AD and the Referenced Material

The effectivity of Boeing Alert Requirements Bulletin 777-27A0125 RB, dated February 3, 2023, is limited to Model 777-200, -200LR, -300, -300ER, and 777F series airplanes, having certain line numbers. However, the applicability of this proposed AD includes all Model 777-200, -200LR, -300, -300ER, and 777F series airplanes. Because the affected parts are rotable parts, the FAA has determined that these parts could later be installed on airplanes that were initially delivered with acceptable parts, thereby subjecting those airplanes to the unsafe condition. The FAA has confirmed with Boeing that the Accomplishment Instructions in Boeing Alert Requirements Bulletin 777-27A0125 RB, dated February 3, 2023, are applicable to the expanded group of airplanes.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 312 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD: