Discussion \n\n\n\tWe issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all ATR-GIE Avions de Transport R(eacute)gional Model ATR72 airplanes. The NPRM published in the Federal Register on March 22, 2018 (83 FR 12508). The NPRM was prompted by a determination that more restrictive maintenance instructions and airworthiness limitations are necessary. The NPRM proposed to require revising the maintenance or inspection program, as applicable, to incorporate new or revised maintenance instructions and airworthiness limitations. We are issuing this AD to address fatigue cracking, damage, and corrosion in principal structural elements, which could result in reduced structural integrity of the airplane. \n\tThe European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2017-0223R1, dated December 15, 2017 (referred to after this as theMandatory Continuing Airworthiness Information, or ''the MCAI''), to correct an unsafe condition for all ATR-GIE Avions de Transport R(eacute)gional Model ATR72 airplanes. The MCAI states: \n\n\n\tThe airworthiness limitations and certification maintenance requirements (CMR) for ATR aeroplanes, which are approved by EASA, are currently defined and published in the ATR72-101/-201/-102/-202/ -211/-212/-212A Time Limits (TL) document. These instructions have been identified as mandatory actions for continued airworthiness. \n\tFailure to accomplish these instructions could result in an unsafe condition. \n\tConsequently, ATR published Revision 15 of the ATR72-101/-201/- 102/-202/-211/-212/-212A TL document, which contains new and/or more restrictive CMRs and airworthiness limitation tasks. \n\tFor the reasons described above, this (EASA) AD requires accomplishment of the actions specified in the ATR72-101/-201/-102/- 202/-211/-212/-212A TL document Revision 15, hereafter referred to as 'the TLD' in this (EASA) AD. \n\tThis (EASA) AD, in conjunction with two other (EASA) ADs related to ATR42-200/-300/-320 (EASA AD 2017-0221) and ATR42-400/-500 (EASA AD 2017-0222) aeroplanes, retains the requirements of EASA AD 2009- 0241 and EASA AD 2012-0193. Once all these three ADs are effective, EASA will cancel EASA AD 2009-0242 and EASA AD 2012-0193. \n\tThis (EASA) AD is revised to provide the correct issue date (02 May 2017) of the TLD. The original (EASA) AD inadvertently referenced the EASA approval date for that document. \n\n\n\tThis AD requires revising the maintenance or inspection program to incorporate certain maintenance instructions and airworthiness limitations. The unsafe condition is fatigue cracking, damage, and corrosion in principal structural elements, which could result in reduced structural integrity of the airplane. You may examine the MCAI in the AD docket on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2018-0166. \n\nComment \n\n\n\tWe gave the public the opportunity to participate in developing this final rule. The following presents the comment received on the NPRM and the FAA's response. \n\nRequest To Correct Typographical Error \n\n\n\tEmpire Airlines asked that airworthiness limitations (AWL) task number 572401-1, identified in table 1 to paragraph (h) of this AD, be changed to AWL task number 572402-1. Empire Airlines stated that AWL task number 572401-1 corresponds to maintenance review board report (MRBR) task numbers ZL-500-01-1 and ZL-600-01-1; and the MRBR task numbers ZL-520-01-1 and ZL-620-01-1, identified in table 1 to paragraph (h) of this AD, correspond with AWL task number 572402-1. Empire Airlines provided substantiation data to this effect. \n\tWe agree with the commenter that a typographical error was made in the AWL task number 572401-1, identified in table 1 to paragraph (h) of this AD. We have corrected this error accordingly. \n\n((Page 34032)) \n\nAirworthiness Limitations Basedon Type Design \n\n\n\tThe FAA recently became aware of an issue related to the applicability of ADs that require incorporation of an airworthiness limitations section (ALS) revision into an operator's maintenance or inspection program. \n\tTypically, when these types of ADs are issued by civil aviation authorities of other countries, they apply to all airplanes covered under an identified type certificate (TC). The corresponding FAA AD typically retains applicability to all of those airplanes. \n\tIn addition, U.S. operators must operate their airplanes in an airworthy condition, in accordance with 14 CFR 91.7(a). Included in this obligation is the requirement to perform any maintenance or inspections specified in the ALS, and in accordance with the ALS as specified in 14 CFR 43.16 and 91.403(c), unless an alternative has been approved by the FAA. \n\tWhen a type certificate is issued for a type design, the specific ALS, including revisions, is a part of that type design, as specified in14 CFR 21.31(c). \n\tThe sum effect of these operational and maintenance requirements is an obligation to comply with the ALS defined in the type design referenced in the manufacturer's conformity statement. This obligation may introduce a conflict with an AD that requires a specific ALS revision if new airplanes are delivered with a later revision as part of their type design. \n\tTo address this conflict, the FAA has approved alternative methods of compliance (AMOCs) that allow operators to incorporate the most recent ALS revision into their maintenance/inspection programs, in lieu of the ALS revision required by the AD. This eliminates the conflict and enables the operator to comply with both the AD and the type design. \n\tHowever, compliance with AMOCs is normally optional, and we recently became aware that some operators choose to retain the AD- mandated ALS revision in their fleet-wide maintenance/inspection programs, including those for new airplanes delivered with later ALS revisions, to help standardize the maintenance of the fleet. To ensure that operators comply with the applicable ALS revision for newly delivered airplanes containing a later revision than that specified in an AD, we plan to limit the applicability of ADs that mandate ALS revisions to those airplanes that are subject to an earlier revision of the ALS, either as part of the type design or as mandated by an earlier AD. \n\tThis AD therefore applies to ATR-GIE Avions de Transport R(eacute)gional Model ATR72-101, -102, -201, -202, -211, -212, and - 212A airplanes with an original certificate of airworthiness or original export certificate of airworthiness that was issued on or before the date of approval of the ALS revision identified in this AD. Operators of airplanes with an original certificate of airworthiness or original export certificate of airworthiness issued after that date must comply with the airworthiness limitations specified as part of the approved type design and referenced on the type certificate data sheet. \n\nConclusion \n\n\n\tWe reviewed the relevant data, considered the comment received, and determined that air safety and the public interest require adopting this final rule with the change described previously and minor editorial changes. We have determined that these minor changes: \n\tAre consistent with the intent that was proposed in the NPRM for addressing the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM. \n\tWe also determined that these changes will not increase the economic burden on any operator or increase the scope of this final rule. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tATR-GIE Avions de Transport R(eacute)gional has issued the ATR72 Time Limits document, Revision 15, dated May 2, 2017. This service information describes preventive maintenance requirements and includes updated limitations, tasks, thresholds and intervals to be incorporated into the maintenance or inspection program. 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 the ADDRESSES section. \n\nCosts of Compliance \n\n\n\tWe estimate that this AD affects 26 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\tWe have determined that revising the maintenance or inspection program takes an average of 90 work-hours per operator, although we recognize that this number may vary from operator to operator. In the past, we have estimated that this action takes 1 work-hour per airplane. Since operators incorporate maintenance or inspection program changes for their affected fleet(s), we have determined that a per- operator estimate is more accurate than a per-airplane estimate. Therefore, we estimate the total cost per operator to be $7,650 (90 work-hours x $85 per work-hour). \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\tWe are 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\tThis AD is issued in accordance with authority delegated by the Executive Director, Aircraft Certification Service, as authorized by FAA Order 8000.51C. In accordance with that order,issuance of ADs is normally a function of the Compliance and Airworthiness Division, but during this transition period, the Executive Director has delegated the authority to issue ADs applicable to transport category airplanes and associated appliances to the Director of the System Oversight Division. \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) Is not a ''significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), \n\t(3) Will not affect intrastate aviation in Alaska, and \n\t(4) Will not have a significant economic impact, positive or negative, \n\n((Page 34033)) \n\non 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.