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 certain The Boeing Company Model 737-800 series airplanes. The NPRM published in the Federal Register on May 14, 2019 (84 FR 21279). The NPRM was prompted by reports of inadequate clearance between a FQIS tank unit at rib 21 and the stringer U-14 reinforcement angle added as a part of a split winglet modification per supplemental type certificate (STC) ST00830SE. The NPRM proposed to require a detailed inspection to measure the clearance between the FQIS tank unit and a certain reinforcement angle installed as a part of the split winglet modification, and repair if necessary. \n\tThe FAA is issuing this AD to address inadequate clearance between a certain FQIS tank unit and a certain reinforcement angle upon accomplishment of a certain split winglet modification, which could result in a potential source of ignition in a fuel tank and consequent fire, overpressure, and structural failure of the wing and possible loss of the airplane. \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\nSupport for the NPRM \n\n\n\tUnited Airlines stated that it concurs with the proposed actions with no additional comments. \n\nRequest To Clarify Paragraph (c) Applicability of the Proposed AD \n\n\n\tBoeing and Aviation Partners Boeing (APB) requested that we revise paragraph (c) of the proposed AD to include more detail as to which airplanes are affected. Boeing explained that STC ST00830SE has multiple configurations, and the proposed AD is applicable to only one configuration; airplanes in that configuration are identified in Aviation Partners Boeing Service Bulletin AP737-57-020, dated April 5, 2018. APB clarified further that STC ST00830SE includes both blended and splitscimitar winglet configurations, but operators with aircraft modified to receive the blended winglets do not install the reinforcement that may interfere with the tank unit, and are not subject to the unsafe condition and requirements of the proposed AD. \n\tThe FAA agrees with the commenters' request for the reasons provided. The FAA has revised paragraph (c) of this AD to state that this AD applies to The Boeing Company Model 737-800 series airplanes, certificated in any category, line numbers 4919 through 5063 inclusive, modified with split winglets per STC ST00830SE and listed in Aviation Partners Boeing Service Bulletin AP737-57-020, dated April 5, 2018. \n\nRequest To Delete ODA Provisions \n\n\n\tBoeing and APB requested that the FAA delete paragraph (h)(3) of the proposed AD because The Boeing Company Organization Designation Authorization (ODA) does not have AMOC authority for the referenced split scimitar winglet STC ST00830SE. \n\tThe FAA agrees with the request for the reasonsprovided. The FAA has removed paragraph (h)(3) of this AD. \n\nRequest To Clarify the Cost of Compliance Section of the NPRM \n\n\n\tBoeing requested that the FAA revise the Cost of Compliance section of the NPRM to clarify that APB is responsible for warranty coverage. Boeing reasoned that the NPRM's language of ''according to the manufacturer . . .'' did not specify which manufacturer, Boeing or APB, would be responsible for warranty coverage. \n\tThe FAA agrees with the request for the reasons provided. The FAA has revised the Costs of Compliance section of this final rule to clarify that APB is the manufacturer responsible for warranty coverage. \n\n((Page 64724)) \n\nRequest To Revise the Summary of the NPRM \n\n\n\tBoeing requested that the FAA revise the SUMMARY section of the NPRM to further clarify which airplanes are affected by the proposed AD. Boeing suggested that the FAA add ''modified with split winglets and listed in Aviation Partners Boeing Service Bulletin AP737-57-020,dated April 5, 2018,'' as a qualifier for the airplanes affected. In addition, Boeing requested that the FAA clarify what prompted the AD and the requirements of the AD by adding language that makes clear the reinforcement angle was added as a part of the referenced split scimitar winglet STC ST00830SE. \n\tThe FAA partially agrees with the request. The FAA disagrees with the request to add the qualifying statement of ''modified with split winglets and listed in Aviation Partners Boeing Service Bulletin AP737- 57-020, dated April 5, 2018,'' because the SUMMARY section serves only as a brief introduction to the NPRM, and the level of detail requested by Boeing is reserved for the Regulatory Section of the proposed AD. As discussed earlier, the FAA has revised paragraph (c) of this AD to clarify that this AD applies only to The Boeing Company Model 737-800 series airplanes modified with split winglets per STC ST00830SE and listed in Aviation Partners Boeing Service Bulletin AP737-57-020,dated April 5, 2018. However, the FAA has revised the SUMMARY section of the final rule to clarify that a certain reinforcement angle was added as a part of a certain split winglet modification. \n\tThe FAA agrees with Boeing's request to clarify what prompted the NPRM and the requirements of the NPRM, for the reasons provided. The SUMMARY section of this AD has been revised accordingly. \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 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 final rule. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tThe FAA reviewed Aviation Partners Boeing Service Bulletin AP737- 57-020, dated April 5, 2018. This service information describes procedures for a detailed inspection to measure the clearance between the FQIS tank unit at rib 21 (WSTA 617) and stringer U-14 reinforcement angle on the left-hand wing, and repair including trimming the stringer U-14 reinforcement angle to obtain minimum clearance. 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 16 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: \n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per Cost on U.S. \n\tAction Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Detailed Inspection................ 7 work-hours x $85 per hour $0 $595 $9,520 \n\t= $595. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tThe FAA estimates the following costs to do any necessary repair that would be required based on the results of the inspection. The FAA has no way of determining the number of aircraft that might need this repair: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Repair..................................... 4 work-hours x $85 per hour = $340. $0 $340 ---------------------------------------------------------------------------------------------------------------- \n\n\n\tAccording to Aviation Partners Boeing, some or all 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 known costs in the agency's 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\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 \n\n((Page 64725)) \n\n13132. 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. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.