AD 2022-18-06

This AD is effective October 26, 2022.

For service information identified in this final rule, contact General Electric Company, 1 Neumann Way, Cincinnati, OH 45215; phone: (513) 552-3272; email: aviation.fleetsupport@ge.com; website: www.ge.com. You may view this service information 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.

Alexei Marqueen, Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; phone: (781) 238-7178; email: Alexei.T.Marqueen@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 all GE GE90-110B1 and GE90-115B model turbofan engines and certain GE90-76B, GE90-85B, GE90-90B, and GE90-94B model turbofan engines. The NPRM published in the Federal Register on May 27, 2022 (87 FR 32098). The NPRM was prompted by notification by the engine manufacturer of the detection of melt-related freckles in the forgings and billets, which may reduce the life of certain rotating CDP seals, interstage HPT rotor seals, and HPT rotor stage 2 disks on GE90-110B1 and GE90-115B model turbofan engines and may reduce the life of certain interstage HPT rotor seals on GE90-76B, GE90-85B, GE90-90B, and GE90-94B model turbofan engines. The manufacturer's investigation determined that, as a result of such freckles forming in the forgings and billets, certain rotating CDP seals, interstage HPT rotor seals, and HPT rotor stage 2 disks (life-limited parts (LLPs)) may have undetected subsurface anomalies that developed during the manufacturing process, resulting in reduced material properties and a lower fatigue life capability. Reduced material properties may cause premature LLP fracture, which could result in uncontained debris release. As a result of its investigation, the manufacturer determined the need to reduce the life limits of certain LLPs. To reflect these reduced life limits, the manufacturer revised the ALS of the affected GE90-100 EMs. Additionally, the manufacturer published service information that specifies procedures for the removal and replacement of certain interstage HPT rotor seals installed on GE90-76B, GE90-85B, GE90-90B, and GE90-94B model turbofan engines. In the NPRM, the FAA proposed to require revising the ALS of the applicable GE90-100 EM and the operator's existing approved maintenance program or inspection program, as applicable, to incorporate reduced life limits for certain LLPs. The NPRM also proposed to require the removal and replacement of certain interstage HPT rotor seals. The FAA is issuing this AD to address the unsafe condition on these products.

The FAA received comments from six commenters. The commenters were Air Line Pilots Association, International (ALPA), American Airlines, The Boeing Company (Boeing), FedEx Express, Japan Airlines, and United Airlines. Five of the commenters, ALPA, American Airlines, Boeing, FedEx Express, and United Airlines, supported the proposal without change. The following presents the comment received on the NPRM and the FAA's response.

Japan Airlines requested that the FAA refer to GE90 SB 72-1211, latest revision, in the AD as the appropriate source of service information for the required actions. Japan Airlines noted that this would confirm the source of the affected interstage HPT rotor seal for the GE90-76B, GE90-85B, GE90-90B, and GE90-94B model engines. The FAA infers that Japan Airlines is requesting for GE90 SB 72-1211 to be incorporated by reference. The FAA disagrees with the request to incorporate GE90 SB 72-1211 by reference. Paragraph (c)(2) of this AD identifies the affected interstage HPT rotor seal installed on the GE90-76B, GE90-85B, and GE90-94B model turbofan engines by part number and serial number. The FAA did not change this AD as a result of this comment.

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, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator.

The FAA reviewed GE GE90-100 SB 72-0851 R00, dated August 17, 2021. This service information provides reduced life limits for certain LLPs. The FAA also reviewed GE GE90 SB 72-1211 R00, dated March 9, 2022. This service information describes procedures for removing and replacing certain interstage HPT rotor seals.

The FAA estimates that this AD affects 248 engines installed on airplanes of U.S. registry. The FAA estimates that zero engines installed on airplanes of U.S. registry will require replacement of the interstage HPT rotor seal.

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: