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 ADDRESSES . Include “Docket No. FAA-2024-2137; Project Identifier AD-2023-00297-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 Courtney Tuck, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone 206-231-3986; email Courtney.K.Tuck@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 2019-22-02, Amendment 39-19781 (84 FR 67854, December 12, 2019) (AD 2019-22-02), for all The Boeing Company Model 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747-8F, and 747-8 series airplanes. AD 2019-22-02 was prompted by reports of uncommanded fore and aft movement of the Captain's and First Officer's seats. AD 2019-22-02 requires an identification of the part number, and if applicable the serial number, of the Captain's and First Officer's seats, and applicable on-condition actions. AD 2019-22-02 also requires a one-time detailed inspection and repetitive checks of the HMS of the Captain's and First Officer's seats, and applicable on-condition actions. AD 2019-22-02 also provides an optional terminating action for the repetitive checks of the HMS for certain airplanes. The FAA issued AD 2019-22-02 to address uncommanded fore and aft movement of the Captain's and First Officer's seats. An uncommanded fore or aft seat movement during a critical part of a flight, such as takeoff or landing, could cause a flight control obstruction or unintended flight control input, which could result in the loss of the ability to control the airplane.

Actions Since AD 2019-22-02 Was Issued

Since the FAA issued AD 2019-22-02, Boeing and the seat supplier (Ipeco) determined that certain seat part numbers were inadvertently omitted from the service information required by AD 2019-22-02. Ipeco subsequently updated their service information to include the additional part numbers, and Boeing updated their service information as well. Based on this, the FAA has determined that additional seats are affected by the unsafe condition.

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 Special Attention Service Bulletin 747-25-3644, Revision 2, dated January 27, 2023. The material describes procedures for identification of the part number, and the serial number if applicable, of the Captain's and First Officer's seats, and applicable on-condition actions. On-condition actions include an inspection of each seat's fore and aft and vertical manual control levers for looseness, installation of serviceable seats, and a seat operational test after any cable adjustment. This material also adds Ipeco seat part numbers 3A258-0041-01-1Z and 3A258-0042-01-1Z.

The FAA also reviewed Boeing Special Attention Service Bulletin 747-25-3653, Revision 2, dated January 27, 2023. This material describes procedures for a detailed inspection and repetitive checks of the HMS (including for any Artus part and amendment numbers of the horizontal actuator of the HMS) for the Captain's and First Officer's seats for findings ( e.g., evidence of cracks, scores, corrosion, dents, deformation, or visible wear; and incorrectly assembled microswitch assemblies, actuators, and limit switches), and applicable on-condition actions. The on-condition actions include clearing the seat tracks of foreign object debris (FOD), overhauling the HMS, and replacing the horizontal actuator. This material also describes procedures for an optional terminating action for the repetitive checks by installing a serviceable Captain's or First Officer's seat.

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 ADDRESSES section.

Proposed AD Requirements in This NPRM

Although this proposed AD does not explicitly restate the requirements of AD 2019-22-02, this proposed AD would retain all of the requirements of AD 2019-22-02. Those requirements are referenced in the service information identified previously, which, in turn, is referenced in paragraphs (g) and (h) of this proposed AD.

This proposed AD would require accomplishing the actions specified in the service information 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 service information at regulations.gov under Docket No. FAA-2024-2137.

Acceptable Methods of Compliance

The FAA has determined that the actions required by paragraphs (g) and (h) of this AD are not required under specific conditions, e.g., if it can be shown through maintenance records that the required actions have already been accomplished by the previous revision of the service information and specific conditions have been met. Paragraph (j) of this AD identifies these conditions. Complying with these conditions adequately addresses the unsafe condition identified in this proposed AD.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 162 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD: