AD 2025-01-03

This AD is effective March 11, 2025.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD as of March 11, 2025.

AD Docket: You may examine the AD docket at regulations.gov under Docket No. FAA-2024-2325; 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 final rule, any comments received, and other information. The address for Docket Operations is U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.

Material Incorporated by Reference:

• For CFM material identified in this AD, contact CFM, GE Aviation Fleet Support, 1 Neumann Way, M/D Room 285, Cincinnati, OH 45215; phone: (877) 432-3272; email: aviation.fleetsupport@ge.com.

• You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 1200 District Avenue, Burlington, MA 01803. For information on the availability of this material at the FAA, call (817) 222-5110. It is also available at regulations.gov under Docket No. FAA-2024-2325.

Mehdi Lamnyi, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone: (781) 238-7743; email: mehdi.lamnyi@faa.gov.

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain CFM Model LEAP-1A and LEAP-1C engines. The NPRM published in the Federal Register on October 2, 2024 (89 FR 80155). The NPRM was prompted by a report of an in-flight shutdown caused by turbine blades that had broken and metal that entered the exhaust. A manufacturer investigation later revealed that the aft arm of the HPT rotor interstage seal had failed due to a non-conforming surface condition in the fillet area coupled with higher-than-expected operating stress due to friction. In the NPRM, the FAA proposed to require removal from service and replacement of the HPT rotor interstage seal. Since the HPT rotor interstage seal part number is interchangeable between LEAP-1A and LEAP-1C engines, the NPRM also proposed to prohibit installation of these affected parts onto any LEAP-1A or LEAP-1C engine. The FAA is issuing this AD to address the unsafe condition on these products.

The FAA received comments from Airline Pilots Association International (ALPA), StandardAero, an individual commenter, and an anonymous commenter. All commenters supported the NPRM without change.

The FAA reviewed the relevant data, considered the comments received, and determined that air safety requires adopting the AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, this AD is adopted as proposed in the NPRM.

The FAA reviewed the following CFM material:

• CFM Service Bulletin (SB) LEAP-1A-72-00-0525-01A-930A-D, Issue 002-00, dated June 28, 2024, which provides the serial numbers (S/Ns) of the affected HPT rotor interstage seals for LEAP-1A engines.

• CFM SB LEAP-1C-72-00-0124-01A-930A-D, Issue 001-00, dated September 5, 2024, which provides the S/Ns of the affected HPT rotor interstage seals that are excluded from installation onto LEAP-1C engines.

This material also includes instructions for removal and installation of the HPT rotor interstage seal. 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.

The FAA estimates that this AD affects 56 engines installed on airplanes of U.S. registry.

The FAA estimates the following costs to comply with this AD:

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.

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.

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

1. The authority citation for part 39 continues to read as follows:

2. The FAA amends § 39.13 by adding the following new airworthiness directive: