AD 2021-26-06

This AD is effective February 15, 2022.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD as of February 15, 2022.

For service information identified in this final rule, contact General Electric Company, GE Aviation, Room 285, 1 Neumann Way, Cincinnati, OH 45215; phone: (513) 552-3272; email: aviation.fleetsupport@ge.com; website: https://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. It is also available at https://www.regulations.gov by searching for and locating Docket No. FAA-2021-0567.

Stephen Elwin, Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; phone: (781) 238-7236; fax: (781) 238-7199; email: Stephen.L.Elwin@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 GE90-76B, GE90-85B, GE90-90B, GE90-94B, GE90-110B1, and GE90-115B model turbofan engines with a certain TGB radial gearshaft installed. The NPRM published in the Federal Register on August 12, 2021 (86 FR 44321). The NPRM was prompted by notification of two separate IFSDs resulting from the failure of the TGB radial gearshaft. After further investigation, the manufacturer determined that rework on the TGB radial gearshaft teeth chamfers during manufacturing may have caused local burrs and micro-cracks which led to high-cycle fatigue failure. GE subsequently issued service information to provide instructions for a one-time visual inspection of the affected radial gearshafts for the presence of burrs or rework on TGB radial gearshaft teeth chamfers. In the NPRM, the FAA proposed to require visual inspection of the TGB radial gearshaft and, depending on the results of the inspection, replacement of the TGB radial gearshaft. The FAA is issuing this AD to address the unsafe condition on these products.

The FAA received comments from 5 commenters. The commenters were Air Line Pilots Association, International, The Boeing Company, FedEx Express, Japan Airlines (JAL), and United Airlines. The following presents the comments received on the NPRM and the FAA's response to each comment.

JAL asked why there is a difference between the affected serial numbers (S/Ns) in this AD and the related service bulletins (SBs).

The FAA notes that the applicable SBs include several populations of TGB radial gearshafts. The FAA determined that TGB radial gearshafts with S/Ns starting with prefix FIAAXXXX, FIA05XXX to FIA09XXX, or FIA0AXXX to FIA0NXXX are not subject to the unsafe condition in this AD. Although this AD does not require that these TGB radial gearshafts be inspected and removed, operators may still elect to inspect these TGB radial gearshaft at the next scheduled engine shop visit.

JAL requested that the FAA clarify disassembly of the compressor discharge pressure (CDP) seal joint in the definition of “engine shop visit.” JAL indicated that they understand that disassembly of the CDP seal joint is the same as disassembly of the CDP seal flange bolt, but not the same as removal of the CDP seal.

The FAA notes that any disassembly of the CDP seal joint meets the definition of an engine shop visit.

JAL asked if the TGB radial gearshaft is required to be inspected during engine QTW. JAL indicated that GE GE90-100 Service Bulletin (SB) 72-0857 R01, dated April 28, 2021 (GE90-100 SB 72-0857 R01), excludes the performance of the inspection during QTW. The proposed AD, however, did not reference QTW in the required inspection. JAL suggested that the FAA update this AD to either exclude QTW from the compliance requirement for inspection or clarify the difference between the service information and this AD.

The FAA understands that the CDP seal joint, in some cases, may require disassembly during a QTW; however, in this scenario the appropriate provisions would exist to perform the required actions of this AD. A QTW that does not disassemble the CDP seal joint would not meet the definition of an engine shop visit, per this AD.

The FAA determined the need to add the Interim Action paragraph to this AD. The manufacturer is investigating if an additional population of TGB radial gear shafts are affected by the unsafe condition of this AD.

Air Line Pilots Association, International, The Boeing Company, FedEx Express, and United Airlines expressed support for the AD as written.

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.

The FAA reviewed GE GE90 Service Bulletin (SB) 72-1201 R01, dated April 28, 2021 (GE90 SB 72-1201 R01), and GE90-100 SB 72-0857 R01, dated April 28, 2021. GE90 SB 72-1201 R01 specifies procedures for performing a one-time inspection of the TGB radial gearshaft for presence of burrs or rework on teeth chamfers on GE90-76B, GE90-85B, GE90-90B, and GE90-94B model turbofan engines. GE90-100 SB 72-0857 R01 specifies procedures for performing a one-time inspection of the TGB radial gearshaft for presence of burrs or rework on teeth chamfers on GE90-110B1 and GE90-115B model turbofan engines. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in ADDRESSES.

The FAA considers this AD to be an interim action. If final action is later identified, the FAA may consider additional rulemaking.

The FAA estimates that this AD affects 126 engines installed on airplanes of U.S. registry.

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

The FAA estimates the following costs to do any necessary replacement that would be required based on the results of the inspection. The agency has no way of determining the number of aircraft that might need this replacement:

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: