Discussion \n\n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2018-16-05, Amendment 39-19345 (83 FR 38250, August 6, 2018) (''AD 2018-16-05''). AD 2018-16-05 applied to certain The Boeing Company Model 757-200, -200PF, -200CB, and -300 series airplanes. The NPRM published in the Federal Register on December 17, 2019 (84 FR 68822). The NPRM was prompted by reports of bolt rotation in the engine drag fitting joint and fastener heads; an inspection of the fastener holes revealed that cracks were found in the skin. The NPRM was also prompted by a report of multiple cracks found in the drag fitting at fastener holes during inspections required by AD 2018-16-05. The NPRM proposed to continue to require repetitive inspections for skin cracking and shim migration at the upper link drag fittings, diagonal brace cracking, and fastener looseness; and applicable on-condition actions. The NPRM also proposed to reduce the compliance times for certain inspections and add repetitive inspections at certain fastener hole locations and applicable on-condition actions. The FAA is issuing this AD to address cracking in the wing upper skin and forward drag fittings, which could lead to a compromised upper link and reduced structural integrity of the engine strut. \n\nComments \n\n\n\tThe FAA gave the public the opportunity to participate in developing this AD. The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nSupport for the NPRM \n\n\n\tUnited Airlines (United) and American Airlines (American) stated their concurrence with the NPRM. \n\nEffect of Winglets on Accomplishment of the Proposed Actions \n\n\n\tAviation Partners Boeing (APB) stated that they have reviewed the NPRM and have determined that the installation of winglets per Supplemental Type Certificate (STC) ST01518SE does not affect the accomplishment of the manufacturer's service instructions. \n\tTheFAA agrees with the commenter that STC ST01518SE does not affect the accomplishment of the manufacturer's service instructions. The FAA has redesignated paragraph (c) of the proposed AD as paragraph (c)(1) of this AD and added paragraph (c)(2) to this AD to state that installation of STC ST01518SE does not affect the ability to accomplish the actions required by this AD. Therefore, for airplanes on which STC ST00830SE is installed, a ''change in product'' alternative method of compliance (AMOC) approval request is not necessary to comply with the requirements of 14 CFR 39.17. \n\nRequests To Increase the Inspection Intervals \n\n\n\tAmerican and United requested that the repetitive interval for the general visual inspection of the diagonal brace and diagonal brace fittings be increased from 2,100 flight cycles (FC) to 3,000 FC. In addition, American requested that the initial interval for the inspection also be increased to 3,000 FC. The commenters maintained that 2,100 FC does not align with their maintenance program intervals, which causes a significant burden on operators. United and American also stated that they have completed the inspection of 13 and 20 airplanes respectively and found no evidence of cracking, which indicates that the existing 3,000 FC interval is conservative. \n\tThe FAA disagrees with the requested change to the indicated repetitive inspection interval and initial interval. The FAA acknowledges that incorporating the interval into the existing maintenance program could be challenging for some operators. However, the inspection involves a visual assessment that requires limited disassembly and could be carried out without placing the aircraft in a heavy maintenance configuration. The reduced intervals are based on the re-assessment of the damage tolerance analysis to adjust for eleven additional crack findings since issuance of Boeing Alert Requirements Bulletin 757-57A0073 RB, dated July 14, 2017. The FAA has determined that the reduced inspection interval is necessary to avoid jeopardizing safety. The FAA has not changed the initial and repetitive inspection intervals required in this AD. \n\nRequest for Clarification That Compliance Times Cannot Be Extended \n\n\n\tBoeing requested that clarification be added to the proposed AD to specify that the grace period provided for the newly proposed requirements cannot be used to extend compliance times for actions required by AD 2018-16-05. Boeing suggested that the FAA add a new paragraph to the proposed AD that would explicitly re-state the requirements of AD 2018-16-05. Boeing asserted that the new paragraph would maintain the requirements of AD 2018-16-05 only until the actions of paragraph (g) of the proposed AD are implemented. \n\tThe FAA does not agree to restate the requirements of AD 2018-16-05 or to add a new paragraph regarding the compliance time for the previously required actions. As explained in the NPRM, the requirements of AD 2018-16-05 are referenced in the service information required in this AD. Except for the diagonal brace inspections, the compliance times given in Boeing Alert Requirements Bulletin 757-57A0073 RB, Revision 1, dated August 1, 2019, for all actions required by AD 2018- 16-05 are unchanged. The compliance times are defined both in terms of the effective date of AD 2018-16-05 and the effective date of the service information. For the diagonal brace inspections, the compliance time may provide an additional grace period; however, this affects only one inspection cycle, is applicable to a small number of operators, and is an acceptable compliance time to ensure safety. The FAA has determined all other compliance times will ensure an acceptable level of safety. This AD has not been changed in this regard. \n\n((Page 79420)) \n\nRequests To Clarify the Effective Date of AD 2018-16-05 \n\n\n\tAmerican and Boeing requested that the proposed AD be revised to include clarification of the effective date of AD 2018-16-05. The commenters observed that some compliance times are given as the number of flight cycles after the ''effective date of AD 2018-16-05,'' and that where Boeing Alert Requirements Bulletin 757-57A0073 RB, dated July 14, 2017, uses that phrase, the proposed AD should require using ''September 10, 2018.'' American asserted that the compliance times should be in terms of the date, not of the superseded AD, and that determining the effective date of the replaced AD could be difficult otherwise. The commenters asserted that including this clarification in the new AD would avoid confusion for operators. \n\tThe FAA agrees to clarify the effective date of AD 2018-16-05. The FAA has added an exception in paragraph (h)(3) to indicate that, where Boeing Alert Requirements Bulletin 757-57A0073 RB, Revision 1, dated August 1, 2019, uses the phrase ''the effective date of AD 2018-16- 05,'' this AD requires using ''September 10, 2018 (the effective date of AD 2018-16-05).'' \n\nRequests To Give Credit for Previously Accomplished Actions \n\n\n\tAmerican, Boeing, and FedEx requested that the proposed AD give credit for previously accomplished actions that were similar to or the same as the actions specified in Boeing Alert Requirements Bulletin 757-57A0073 RB, Revision 1, dated August 1, 2019. American noted that Revision 1 of the service bulletin specifies a high frequency eddy current (HFEC) inspection for cracking at fastener locations 11-18 for airplanes already inspected in accordance with the original issue of the service bulletin. American and Boeing asserted that operators of airplanes with fastener holes 1-10 already inspected per Boeing Alert Requirements Bulletin 757-57A0073 RB, dated July 14, 2017, should get credit for the initial inspection of fastener holes 1-10. \n\tThe FAA agrees and has added paragraph (i) to this AD to provide credit for previous actions accomplished using Boeing Alert Requirements Bulletin 757-57A0073 RB, dated July 14, 2017. The FAA has also reidentified subsequent paragraphs accordingly. As specified in Boeing Alert Requirements Bulletin 757-57A0073 RB, Revision 1, dated August 1, 2019, the new actions for fastener locations 11-18 must still be accomplished for airplanes on which the original revision of the RB was previously done. \n\nRequests To Allow Certain AMOCs Previously Approved for AD 2018-16-05 \n\n\n\tAmerican, Delta Air Lines, FedEx, and United requested that the proposed AD be changed to allow AMOCs previously approved for AD 2018- 16-05 for the corresponding requirements of this AD. American, FedEx, and United observed that the inspections specified in Boeing Alert Requirements Bulletin 757-57A0073 RB, dated July 14, 2017, relating to fastener locations 1-10, as well as the repetitive inspections for these locations, do not change with Boeing Alert Requirements Bulletin 757-57A0073 RB, Revision 1, dated August 1, 2019. The commenters asserted that the repairs and corresponding AMOCs should continue to be acceptable. \n\tTheFAA agrees with the requested change. The FAA has changed paragraph (j)(4) of this AD (referred to as paragraph (i)(4) in the proposed AD) to specify that AMOCs granted to AD 2018-16-05 are acceptable as AMOCs to this AD for the corresponding requirements. \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 AD with the changes described previously, and minor editorial changes. The FAA has 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\tThe FAA also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD. \n\nRelated IBR Material Under 1 CFR Part 51 \n\n\n\tThe FAA reviewed Boeing Alert Requirements Bulletin 757-57A0073 RB, Revision 1, dated August 1, 2019. This service information describes procedures for repetitive inspections, including general visual, detailed, and HFEC inspections, for loose fasteners, skin cracking, and shim migration at the upper link drag fittings and for cracking in the diagonal brace and diagonal brace fittings and applicable on-condition actions. 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\tThe FAA estimates that this AD affects 561 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: \n\n\n\tEstimated Costs For Required Actions ---------------------------------------------------------------------------------------------------------------- \n\tCost on U.S. \n\tAction Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Repetitive inspections (retained 83 work-hours x $85 $0 $7,055 per $3,957,855 per \n\tactions from AD 2018-16-05). per hour = $7,055 inspection cycle. inspection cycle. \n\tper inspection \n\tcycle. Repetitive HFEC inspections (new 2 work-hours x $85 0 $170 per inspection $95,370 per \n\taction). per hour = $170 cycle. inspection cycle. \n\tper inspection \n\tcycle. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tThe FAA has received no definitive data that would enable the agency to provide cost estimates for the on-condition actions specified in this AD. \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. \n\n((Page 79421)) \n\nThis 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\tThe FAA has determined that this 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 andthe 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. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.