Background \n\n\n\tThe FAA learned of an uncommanded IFSD of a RRC AE 3007A1 model turbofan engine installed on an Embraer S.A. ERJ-145 airplane conducting a revenue flight. The manufacturer's investigation of this incident revealed that the IFSD resulted from a low-cycle fatigue crack in the dovetail slot for the blade attachment in the 3rd-stage compressor wheel, causing one 3rd-stage compressor blade to release. The crack initiated in the dovetail slot due to a sharp corner in the wheel slot geometry. The broaching process was identified as the cause and parts from this manufacturing lot require removal from service. This condition, if not addressed, could result in uncontained release of the 3rd-stage compressor wheel, damage to the engine, and damage to the airplane. The FAA is issuing this AD to address the unsafe condition on these products. \n\nFAA's Determination \n\n\n\tThe FAA is issuing this AD because the agency evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. \n\nRelated Service Information \n\n\n\tThe FAA reviewed Rolls-Royce Alert Service Bulletin (ASB) AE 3007A- A-72-446, Revision 2, dated July 28, 2020. The ASB describes procedures for replacing certain 3rd-stage compressor wheels. \n\nAD Requirements \n\n\n\tThis AD requires replacement of certain 3rd-stage compressor wheels before they accumulate a specified number of cycles. \n\nFAA's Justification for Immediate Adoption and Determination of the Effective Date \n\n\n\tSection 553(b)(3)(B) of the Administrative Procedure Act (APA) (5 U.S.C.) authorizes agencies to dispense with notice and comment procedures for rules when the agency, for ''good cause,'' finds that those procedures are ''impracticable, unnecessary, or contrary to the public interest.'' Under this section, an agency, upon finding good cause, may issue a final rule without providing noticeand seeking comment prior to issuance. Further, section 553(d) of the APA authorizes agencies to make rules effective in less than 30 days, upon a finding of good cause. \n\tAn unsafe condition exists that requires the immediate adoption of this AD without providing an opportunity for public comments prior to adoption. The FAA has found that the risk to the flying public justifies waiving notice and comment prior to adoption of this rule. RRC inspected a RRC AE3007A1 model turbofan engine after it experiences an uncommanded IFSD during a revenue flight on an Embraer ERJ-145 airplane. \n\tThe manufacturer's inspection discovered a low-cycle fatigue crack in a 3rd-stage compressor wheel that allowed a 3rd-stage compressor blade to release during the flight. The manufacturer traced the cause of the cracked 3rd-stage compressor wheel to a specific machining process that occurred during manufacture of the 3rd-stage compressor wheels. The manufacturer's subsequent investigation discovered multiple 3rd-stage compressor wheels in the affected serial numbered population with similar low-cycle fatigue cracks. The 3rd-stage compressor wheels identified in this AD are unable to remain in service beyond the cycles since new limits listed in paragragh (g) of this AD. As a result of the shortened compliance times established based on the FAA's risk assessment, the FAA has determined that there is insufficient time available to allow for notice and opportunity for prior public comment. \n\tThe FAA considers the removal of these 3rd-stage compressor wheels from service to be an urgent safety issue. Exceeding the reduced cycle limits on the 3rd-stage compressor wheels required by this AD could lead to failure of the 3rd-stage compressor wheel and high-energy release of the 3rd-stage compressor wheel, resulting in damage to the engine and damage to the airplane. Accordingly, notice and opportunity for prior public comment are impracticable and contrary to public interest pursuant to 5 U.S.C. 553(b)(3)(B). \n\tIn addition, the FAA finds that good cause exists pursuant to 5 U.S.C. 553(d) for making this amendment effective in less than 30 days, for the same reasons the FAA found good cause to forgo notice and comment. \n\n((Page 45771)) \n\nComments Invited \n\n\n\tThe FAA invites you to send any written data, views, or arguments about this final rule. Send your comments to an address listed under the ADDRESSES section. Include the docket number FAA-2020-0679 and Project Identifier AD-2020-01060-E at the beginning of your comments. The most helpful comments reference a specific portion of the final rule, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this final rule because of those comments. \n\tExcept for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to https://www.regulations.gov, including any personal information you provide. The FAA will also post a report summarizing each substantive verbal contact received about this final rule. \n\nConfidential Business Information \n\n\n\tConfidential Business Information (CBI) is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this final rule contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this final rule, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as ''PROPIN.'' The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docketof this final rule. Submissions containing CBI should be sent to Kyri Zaroyiannis, Aerospace Engineer, Chicago ACO, FAA, 2300 E. Devon Ave., Des Plaines, IL 60018. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking. \n\nRegulatory Flexibility Act \n\n\n\tThe requirements of the Regulatory Flexibility Act (RFA) do not apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt a rule without prior notice and comment. Because the FAA has determined that it has good cause to adopt this rule without notice and comment, RFA analysis is not required. \n\nCosts of Compliance \n\n\n\tThe FAA estimate that this AD affects 4 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.Action Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Remove 3rd-stage compressor wheel..... 40 work-hours x $85 per $0 $3,400 $13,600 \n\thour = $3,400. Replace 3rd-stage compressor wheel.... 85 work-hours x $85 per 32,844 40,069 160,276 \n\thour = $7,225. ---------------------------------------------------------------------------------------------------------------- \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, SubpartIII, 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\nList ofSubjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.