Airworthiness Directives: The Boeing Company Airplanes

Airworthiness Directives; The Boeing Company Airplanes

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain The Boeing Company Model 757 airplanes. The NPRM published in the Federal Register on March 25, 2024 (89 FR 20565). The NPRM was prompted by reports of several occurrences of a PTU control valve that failed to open when commanded. In the NPRM, the FAA proposed to require installing new relays and changing certain wire bundles leading to the PTU control valve. The FAA is issuing this AD to address failure of the PTU control valve, which in conjunction with a loss of the left engine or engine-driven pump (EDP) during takeoff, may result in a failure of the landing gear to retract in a timely manner. This condition, if not addressed, could add drag, affect climb gradient, and prevent the airplane from clearing obstacles on takeoff. This condition can result in loss of continued safe flight and landing.

Discussion of Final Airworthiness Directive

Comments

The FAA received a comment from the Air Line Pilots Association, International (ALPA), who supported the NPRM without change.

The FAA received additional comments from Aviation Partners Boeing (APB), Boeing, Delta Air Lines (Delta), and United Parcel Service Airlines (UPS Airlines). United Airlines (United) supported the NPRM and also provided additional comments, as discussed below. The following presents the comments received on the NPRM and the FAA's response to each comment.

Effect of Winglets on Accomplishment of the Proposed Actions

APB stated that the installation of winglets per Supplemental Type Certificate STC ST01518SE does not affect the accomplishment of the manufacturer's service instructions.

The FAA agrees with the commenter that STC ST01518SE does not affect the accomplishment of the manufacturer's service instructions. Therefore, the installation of STC ST01518SE does not affect the ability to accomplish the actions required by this AD. The FAA has not changed this AD in this regard.

Request To Revise Unsafe Condition Statement

Boeing requested two changes in the description of the unsafe condition. One change is in the description of the state of the landing gear retraction abilities from "may result in a failure of the landing gear to retract" to "may result in a failure of the landing gear to retract in a timely manner." Boeing explained that the left hydraulic system's electric motor pump would still function, but has a smaller output capacity that results in being unable to retract the landing gear in the time required to clear obstacles. The other requested change is to clarify what conditions lead up to the slowed retraction of the landing gear. Boeing explained that loss of either the left engine or the EDP would lead to use of the electric motor pump and requested that the related phrase "left engine and engine driven pump (EDP)" be changed to "left engine and/or engine driven pump (EDP)."

The FAA agrees to revise the unsafe condition statement. The revisions provide a more accurate description of the unsafe condition and of what conditions lead up to a slow retraction of the landing gear. However, the FAA has revised "left engine and engine driven pump (EDP)" to "left engine or engine-driven pump (EDP)" instead of using "and/or." Although both failure conditions can occur, only one of the conditions is necessary to affect the landing gear retraction. The FAA has revised the Background section of this final rule and paragraph (e) of this AD accordingly.

Requests To Revise AD To Address Missing Information in Service Information

Boeing stated that additional engineering definition for wire routing is necessary for a group of airplanes identified in Boeing Alert Service Bulletin 757-29A0071, dated November 16, 2023, and Boeing Alert Requirements Bulletin 75-29A0071 RB, dated November 16, 2023, and that the service bulletin and requirements bulletin will be revised. Delta and United requested that paragraph (h) of the proposed AD be revised to add an exception to address the errors in the wire routing definition for the airplanes identified as Group 3 airplanes in Boeing Alert Requirement Bulletin 757-29A0071 RB, dated November 16, 2023 (Group 3 airplanes). United also proposed that paragraph (g) of the proposed AD be revised to incorporate Revision 1 of Boeing Alert Requirement Bulletin 757-29A0071 RB, if it is created prior to the release of this AD. Both Delta and United noted that Boeing published Information Notice 757-29A0071 IN 01 to inform operators of issues with work instructions for the Group 3 airplanes and advised to stop work on those airplanes until new service information is published. United also reasoned that the requested revision would help United and other operators of Group 3 airplanes avoid applying for an AMOC when the final rule is issued.

The FAA agrees with the need to provide additional definition for wire routing that affects Group 3 airplanes because those airplanes would be unable to comply with the instructions provided in Boeing Alert Requirement Bulletin 757-29A0071 RB, dated November 16, 2023. However, the FAA does not agree to revise the AD to reference Revision 1 of Boeing Alert Requirement Bulletin 757-29A0071 RB, or to add an exception to address the errors in the instructions for Group 3 airplanes. A later revision of Boeing Alert Requirement Bulletin 757-29A0071 RB, dated November 16, 2023, has not been issued and the publication date is yet to be determined. To delay this action until the revised service information is published would be inappropriate since the FAA has determined that an unsafe condition exists and that the actions must be conducted on the other affected groups of airplanes to ensure continued safety. Operators may apply for approval to use later revisions as an alternative method of compliance with this AD under the provisions of paragraph (i) of this AD. The FAA has not changed this AD in this regard.

Request To Add an Exception To Allow Alternative Positions for Connectors

Delta requested that paragraph (h) of the proposed AD be revised to add an exception that would allow the use of available connector positions on panels and disconnects other than the ones defined in Boeing Alert Requirement Bulletin 757-29A0071 RB, dated November 16, 2023. Delta explained that the figures in Boeing Alert Requirement Bulletin 757-29A0071 RB, dated November 16, 2023, are specific in defining positions within the panels and disconnects where the connectors will be installed. Delta also stated that the specific location of the connector installation and disconnects in the panel are not necessary for the function of the system. Delta reasoned that allowing operators to install the connectors in alternative available positions would be acceptable for compliance with the proposed AD while also giving operators flexibility in addressing variations in each airplane's existing wiring.

The FAA agrees that using only the defined positions within the panels and disconnect brackets for the new connectors to be installed is not necessary to address the unsafe condition, and that allowing alternatives would provide flexibility in complying with the requirements of this AD on airplanes that might have different wiring configurations. The action to perform the operational test verifies the functionality of the system and will continue to be required. The FAA has added an exception to paragraph (h) of this AD to allow for installing connectors in alternative available positions on panels and disconnect brackets than those defined in Boeing Alert Requirement Bulletin 757-29A0071 RB, dated November 16, 2023.

Request To Allow Use of Other Kit Materials

Delta requested a revision to paragraph (h) of the proposed AD to add an exception that would allow the use of operator-supplied materials that are the same as the Boeing-supplied materials in the parts kit specified in Boeing Alert Requirement Bulletin 757-29A0071 RB, dated November 16, 2023. Delta explained that Boeing kits expire within 3 months because of a limitation on the placard (decal) adhesive and opined that operators should have the ability to supply the same decal if the Boeing-supplied decal expires before use. In addition, Delta also reasoned that operators should be able to supply their own materials if Boeing-supplied kits are not available in time to avoid delays in compliance with the proposed AD.

The FAA does not agree to revise this AD regarding this request. The Boeing-supplied kits are specified in Boeing Alert Service Bulletin 757-29A0071, dated November 16, 2023, which is not required by this AD. This AD requires Boeing Alert Requirements Bulletin 757-29A0071 RB, dated November 16, 2023, which identifies parts that are required for compliance. This AD does not require procuring the Boeing-supplied kits that are specified in Boeing Alert Service Bulletin 757-29A0071, dated November 16, 2023. No revision to this AD is necessary in this regard.

Request To Extend Compliance Time Due to Parts Availability

UPS Airlines requested a revision to paragraph (h) of the proposed AD to add an exception to a compliance time identified in Boeing Alert Requirement Bulletin 757-29A0071 RB, dated November 16, 2023. This requested exception would extend the calendar time limit from the proposed 30 months after the effective date of the AD to 36 months after the effective date of the AD. UPS Airlines explained that the availability of the Boeing-supplied parts kit could affect the ability to comply with the proposed compliance times. UPS Airlines stated that there are only 15 of the Boeing-supplied kits in stock as of the date of the NPRM, with an anticipated lead time of 175 to 352 days if all 15 kits are purchased and the inventory depleted. UPS Airlines added that they have 429 airplanes in a configuration group that would require the same part kit.

The FAA does not agree to revise the AD regarding this issue. As explained in the previous comment, the Boeing-supplied kits are not part of the requirements of Boeing Alert Requirement Bulletin 757-29A0071 RB, dated November 16, 2023, and are specified in Boeing Alert Service Bulletin 757-29A0071, dated November 16, 2023, thus operators may procure the parts from their supplies without an AMOC or revision to this AD. In developing an appropriate compliance time for this action, the FAA considered the recommendations of the manufacturer, the urgency associated with the subject unsafe condition, the availability of required parts, and the practical aspect of accomplishing the required modification within a period of time that corresponds to the normal scheduled maintenance for most affected operators. In consideration of these items, the FAA has determined that the compliance time of 30 months or 2,760 flight hours after the effective date of this AD, whichever occurs first, will ensure an acceptable level of safety. However, under the provisions of paragraph (i) of this AD, the FAA will consider requests for approval of an extension of the compliance time if sufficient data are submitted to substantiate that new compliance times would provide an acceptable level of safety.

Conclusion

The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, and any other changes described previously, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed Boeing Alert Requirements Bulletin 757-29A0071 RB, dated November 16, 2023. This material specifies procedures for changing the wire bundle from circuit breaker C4054 to the P33 panel, installing new relays in the P33 panel, and changing wire bundles to the PTU control valve. 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.

Costs of Compliance

The FAA estimates that this AD affects 467 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:

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

This AD will not have federalism implications under Executive Order 13132. This AD will 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 that this AD:

(1) Is not a "significant regulatory action" under Executive Order 12866,

(2) Will not affect intrastate aviation in Alaska, and

(3) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

The Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

PART 39-AIRWORTHINESS DIRECTIVES

[FR Doc. 2025-00371 Filed 1-8-25; 8:45 am]

BILLING CODE 4910-13-P