Background \n\n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all RRD Trent XWB-75, Trent XWB-79, Trent XWB-79B, Trent XWB-84, and Trent XWB-97 model turbofan engines. The NPRM published in the Federal Register on February 23, 2021 (86 FR 10878). The NPRM was prompted by the manufacturer revising the TLM to incorporate repairs to the LPC blades and introduce a new fan blade inspection. In the NPRM, the FAA proposed to require revisions to the ALS of the RR Trent XWB TLM, as applicable to each engine model, and to the operator's existing approved AMP, to include new or more restrictive sections of the applicable RR Trent XWB TLM for each affected engine model. The FAA is issuing this AD to address the unsafe condition on these products. \n\tThe European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community, has issued EASA AD 2020-0066, dated March 23, 2020 (referred to after this as ''the MCAI''), to address the unsafe condition on these products. The MCAI states: \n\n\n\tThe Airworthiness Limitations Section instructions for Trent XWB engines, which are approved by EASA, are defined and published in TLM TRENTXWB-K0680-TIME0-01. These instructions have been identified as mandatory for continued airworthiness. Failure to accomplish these instructions could result in an unsafe condition. \n\tRolls-Royce recently revised the TLM, introducing new and/or more restrictive instructions. \n\tFor the reason described above, this (EASA) AD requires accomplishment of the instructions specified in the TLM, as defined in this AD. \n\n\n\tYou may obtain further information by examining the MCAI in the AD docket at https://www.regulations.gov by searching for and locating Docket No. FAA-2021-0022. \n\nDiscussion of Final Airworthiness Directive Comments \n\n\n\tThe FAA received comments from two commenters. The commenters were Air Line Pilots Association, International (ALPA) and Delta Air Lines, Inc. (DAL). The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nRequest To Revise Required Actions \n\n\n\tDAL commented that revising the AMP to include the specific requirements contained in Figure 1 to paragraph (g)(1) or Figure 2 to paragraph (g)(2) is difficult. DAL requested that the FAA revise paragraph (g) of this AD to allow incorporation of the specific language referenced in Figure 1 to paragraph (g)(1) or Figure 2 to paragraph (g)(2) into the AMP instead of only allowing incorporation of the figures into the AMP. \n\tThe FAA agrees and has revised Note 1 to paragraph (g) of this AD to clarify that operators may choose to incorporate the language referenced in Figure 1 to paragraph (g)(1) or Figure 2 to paragraph (g)(2) directly into their existing approved AMP instead of incorporating the respective figures into the existing approved AMP. \n\nRequest To Include Modification Specifications of the Ultra Long Range Operation \n\n\n\tDAL noted that paragraph (g)(1) of the NPRM includes a proposed requirement that applies to Trent XWB-84 Ultra Long Range (ULR) operation. However, the RR Trent XWB TLM does not define the specification of a ULR operation. DAL commented that ULR operation requires modification to the airplane. The Trent XWB-84 can be installed on both A350-900 standard or ULR operations without any modification to the engine. DAL added that the airplane type certification data sheet does not specify the modification standards of a ULR operation. Since the TLM does not include any specifications of ULR operation and the aircraft type certificate data sheet does not define this specific standard, DAL requested that the FAA include the modification specifications of the ULR operation in the final rule. \n\tThe FAA disagrees. Although the airplane requires modification for ULR operation, the Trent XWB-84 model turbofan engine does not require modification for ULR operation and can be installed on a standard airplane or a ULR airplane. The FAA did not change this AD. \n\nSupport for the AD \n\n\n\tALPA expressed support for the NPRM as written. \n\nConclusion \n\n\n\tThe 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. \n\nRelated Service Information \n\n\n\tThe FAA reviewed Rolls-Royce Airworthiness Limitations (Mandatory Inspections), TRENTXWB-A-05-20-01-00A01-030A-D, Revision 013, dated September 1, 2019, of the Rolls-Royce Trent XWB TLM TRENTXWB-K0680- TIME0-01, and Rolls-Royce Airworthiness Limitations (Mandatory Inspections), TRENTXWB-B-05-20-01-00A01-030A-D, Revision 005, dated \n\n((Page 36489)) \n\nApril 1, 2020, of the Rolls-Royce Trent XWB TLM TRENTXWB-K0680-TIME0- 01. These two sections of the TLM specify inspection intervals, differentiated by engine model, for critical rotating parts. \n\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects 22 engines installed on airplanes of U.S. registry. \n\tThe FAA estimates the following costs to comply with this AD: \n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per Cost on U.S. \n\tAction Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Revise the ALS of the RR Trent XWB TLM 1 work-hour x $85 per $0 $85 $1,870 \n\tand the operator's existing approved hour = $85. \n\tAMP. ---------------------------------------------------------------------------------------------------------------- \n\nAuthority for This Rulemaking \n\n\n\tTitle 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. \n\tThe 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. \n\nRegulatory FindingsThis 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. \n\tFor the reasons discussed above, I certify this AD: \n\t(1) Is not a ''significant regulatory action'' under Executive Order 12866, \n\t(2) Will not affect intrastate aviation in Alaska, and \n\t(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. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.