Discussion \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 IAE V2500-A1, V2522-A5, V2524-A5, V2525-D5, V2527-A5, V2527E-A5, V2527M-A5, V2528-D5, V2530-A5, V2531-E5, and V2533-A5 model turbofan engines with a certain diffuser case assembly installed. The NPRM published in the Federal Register on December 16, 2019 (84 FR 68374). The NPRM was prompted by a report of a manufacturing quality escape that could impact the life of the diffuser case assembly. The NPRM proposed to require removal of the affected diffuser case assembly from service and replacement with a part eligible for installation. The FAA is issuing this AD to address the unsafe condition on these products. \n\nComments \n\n\n\tThe FAA gave the public the opportunity to participate in developing this final rule. The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nRequestTo Revise the Required Actions \n\n\n\tDelta Air Lines (DAL) requested that the FAA revise paragraph (g), Required Actions, of this AD to include instructions applicable to IAE V2500-D5 model turbofan engines. DAL reasoned that IAE Non-Modification Service Bulletin (NMSB) V2500-ENG-72-0707, dated July 1, 2019 (''IAE NMSB V2500-ENG-72-0707''), referenced in paragraph (g) of this AD, only includes procedures for replacing the affected diffuser case assemblies on IAE V2500-A1/A5 model turbofan engines. If one of the affected diffuser case assemblies was installed on a V2500-D5 model engine, DAL would not be able to accomplish the required actions of this AD. \n\tAs an alternative to revising paragraph (g) of this AD, DAL requested that the FAA add an installation prohibition or parts installation limitation to this AD to prevent the installation of the affected diffuser case assembly in any model turbofan engine. If the FAA adds the installation prohibition to this AD, then DAL requested that the FAA remove the IAE V2500-D5 model turbofan engine from paragraph (c), Applicability, of this AD. \n\tThe FAA disagrees. This AD does not require operators to use IAE NMSB V2500-ENG-72-0707 to replace the affected diffuser case assembly. The note to paragraph (g) of this AD, referencing use of IAE NMSB V2500-ENG-72-0707, is provided as guidance. \n\tThe FAA disagrees with adding an installation prohibition or parts installation limitation to this AD because paragraph (g) of this AD requires the removal of all affected diffuser case assemblies from service. \n\nSupport for the AD \n\n\n\tThe Air Line Pilots Association, International, expressed support for the AD as written. \n\nNo Concerns With the AD \n\n\n\tUnited Airlines commented that it does not operate any of the affected diffuser case assemblies and indicated it does not have any concerns with the proposed AD. \n\nConclusion \n\n\n\tThe FAA reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this final rule as proposed. \n\nRelated Service Information \n\n\n\tThe FAA reviewed IAE NMSB V2500-ENG-72-0707, dated July 1, 2019. The NMSB describes procedures for replacing the affected diffuser case assemblies on IAE V2500-A5 model turbofan engines. \n\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects two engines installed on airplanes of U.S. registry. \n\tThe FAA estimates the following costs to comply with this AD: \n\n((Page 22957)) \n\n\n\n\n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per Cost on U.S. \n\tAction Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Replace the diffuser case assembly.. 70 work-hours x $85 per $250,000 $255,950 $511,900 \n\thour = $5,950. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tAccording to the manufacturer, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected individuals. The FAA does not control warranty coverage for affected individuals. As a result, the FAA has included all costs in our cost estimate. \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 Findings \n\n\n\tThis 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 that 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.List of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.