Background \n\n\n\tEASA AD 2017-0037, dated February 22, 2017 (EASA AD 2017-0037), issued by EASA, which is the Technical Agent for the Member States of the European Union, to correct an unsafe condition for Airbus Helicopters Deutschland GmbH (formerly Eurocopter Deutschland GmbH), Airbus Helicopters Inc. (formerly American Eurocopter LLC) Model MBB-BK 117 D-2 and MBB-BK117 D-2m helicopters. \n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to Airbus Helicopters Deutschland GmbH (AHD) Model MBB-BK 117 D-2 helicopters, with an affected MGB or affected rotor mast nut as identified in Note 1 of EASA AD 2017-0037. The NPRM published in the Federal Register on June 7, 2021 (86 FR 30218). The NPRM was prompted by the discovery that certain parts that are approved for installation on multiple helicopter models are life limited parts when installed on Model MBB-BK 117 D-2 helicopters and some helicopter delivery documents excluded the life limit information, The NPRM proposed to require accomplishing the actions specified in EASA AD 2017-0037, described previously, as incorporated by reference, except for any differences identified as exceptions in the regulatory text of this AD and except as discussed under ''Differences Between this AD and EASA AD 2017-0037.'' The FAA is issuing this AD to address an unsafe condition on these products. See EASA AD 2017-0037 for additional background information. \n\nDiscussion of Final Airworthiness Directive \n\nComments \n\n\n\tThe FAA received no comments on the NPRM or on the determination of the costs. \n\nConclusion \n\n\n\tThese helicopters been approved by EASA and are approved for operation in the United States. Pursuant to the FAA's bilateral agreement with the European Union, EASA has notified the FAA about the unsafe condition described in its AD. The FAA reviewed the relevant data and determined that air safety requires adopting thisAD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tEASA AD 2017-0037 requires establishing a life limit for rotor mast nut part number (P/N) D632K1133-201 and helical gear support P/N D632K1113-201, and replacing these parts before exceeding their life limit. EASA AD 2017-0037 also requires replacing each rotor mast nut P/ N D632K1133-201 for which the hours TIS are unknown and replacing certain part-numbered rotor mast nuts before accumulating 3,708 hours TIS since first installation on a helicopter. EASA AD 2017-0037 requires re-identifying each rotor mast nut P/N 117-12133-01 to P/N D632K1133-201 by following the specified service information. EASA AD 2017-0037 requires replacing any MGB P/N D632K1001-051 with serial number \n\n((Page 50223)) \n\n(S/N) D2-0001 up to D2-0108 inclusive, D2-0123, D2-0126, D2-0127, or D2-0130 up to D2-0136 inclusive with a not affected MGBbefore the affected MGB accumulates 3,708 hours TIS. EASA AD 2017-0037 also prohibits installing an affected rotor mast nut or an affected MGB that has accumulated more than 3,708 hours TIS since first installation on a helicopter. Additionally, EASA AD 2017-0037 requires revising the Aircraft Maintenance Program (AMP). \n\tThis 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 the ADDRESSES section. \n\nOther Related Service Information \n\n\n\tThe FAA reviewed Airbus Helicopters Alert Service Bulletin MBB- BK117 D-2-63A-001, Revision 0, dated December 1, 2016 (ASB 63A-001), which is not incorporated by reference, which specifies procedures for re-identifying the rotor mast nut by using a vibrograph, crossing out the old P/N and marking the new P/N on the outer surface, engraving the letter ''A'' behind the S/N of each part, and updating the historical record and log card toconfirm compliance with ASB 63A-001. ASB 63A-001 also specifies during the next MGB overhaul, making an entry in the log card to confirm re-identification of the helical gear support, and annotating the S/N of the helical gear support. \n\nDifferences Between This AD and EASA AD 2017-0037 \n\n\n\tEASA AD 2017-0037 applies to Model MBB-BK117 D-2 and D2m helicopters, whereas this AD only applies to Model MBB-BK117 D-2 helicopters because Model D-2m is not FAA type-certificated. If the total hours TIS for an affected rotor mast nut cannot be determined, this AD requires removing the rotor mast nut from service before further flight, whereas EASA AD 2017-0037 does not contain this requirement. EASA AD 2017-0037 requires using a vibrograph to re- identify certain rotor mast nuts, whereas this AD requires using a vibro etch instead. EASA AD 2017-0037 requires replacing certain parts, whereas this AD requires removing certain parts from service instead. EASA AD 2017-0037 requires revising theAMP, whereas this AD does not. \n\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects 30 helicopters of U.S. Registry. Labor rates are estimated at $85 per work-hour. Based on these numbers, the FAA estimates the following costs to comply with this AD. \n\tDetermining the total hours TIS on an affected rotor mast nut takes about 1 work-hour for an estimated cost of $85 per helicopter and $2,550 for the U.S. fleet. \n\tRe-identifying a rotor mast nut takes about 1.5 work-hours for an estimated cost of $128 per rotor mast nut. \n\tReplacing a rotor mast nut takes about 6 work-hours and parts cost about $5,351 for an estimated cost of $5,861 per rotor mast nut. \n\tReplacing a MGB, which includes replacing the helical gear support, takes about 42 work-hours and parts cost about $295,000 (overhauled) for an estimated cost of $298,570. \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 helicopters 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 andresponsibilities 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. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.