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 certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. The NPRM published in the Federal Register on September 29, 2016 (81 FR 66874) (''the NPRM''). The NPRM was prompted by a report of a Krueger flap bullnose departing an airplane during taxi, which caused damage to the wing \n\n((Page 39345)) \n\nstructure and thrust reverser. The NPRM proposed to require a one-time detailed visual inspection for discrepancies in the Krueger flap bullnose attachment hardware, and related investigative and corrective actions, if necessary. We are issuing this AD to detect and correct missing Krueger flap bullnose hardware. Such missing hardware could result in the Krueger flap bullnose departing the airplane during flight, which could damage empennage structure and lead to the inability to maintain continued safe flight and landing. \n\nComments \n\n\n\tWe 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\tVincent Romano, a private citizen, and United Airlines (UAL), stated their support for the NPRM. \n\nEffect of Winglets on Accomplishment of the Proposed Actions \n\n\n\tAviation Partners Boeing stated that accomplishing the Supplemental Type Certificate (STC) ST00830SE does not affect the actions specified in the NPRM. \n\tWe concur with the commenter. We have redesignated paragraph (c) of the NPRM as paragraph (c)(1) and added paragraph (c)(2) to this AD to state that installation of STC ST00830SE 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\nRequest To Reference the Latest Service Information \n\n\n\tAll Nippon Airways (ANA), American Airlines (AAL), Boeing, Jet2.com, TUIfly GmbH (HAP), UAL, and Kennedy Juma, requested revising the NPRM to reference Boeing Alert Service Bulletin 737-57A1327, Revision 1, dated September 28, 2016. Some commenters pointed out that the original issue had some errors in the illustrations and needed certain clarifications. ANA and Boeing also requested that we provide credit for accomplishing the original issue of the service information. \n\tWe agree that this final rule should reference the latest service information. Since we issued the NPRM, Boeing issued Boeing Alert Service Bulletin 737-57A1327, Revision 1, dated September 28, 2016. We have revised paragraphs (c)(1) (paragraph (c) of the proposed AD) and (g) of this AD to reference Boeing Alert Service Bulletin 737-57A1327, Revision 1, dated September 28, 2016, for accomplishment of the required actions. We have also revised this AD to provide credit for using Boeing Alert Service Bulletin 737-57A1327, dated May 20, 2016, to accomplish the required actions before the effective date of this AD. \n\nRequest To Correct the Latest Service Information \n\n\n\tAAL requested that Boeing Alert Service Bulletin 737-57A1327, Revision 1, dated September 28, 2016, be corrected to address errors in Figures 1, 2, 3, and 4. AAL stated that these errors affect the depiction of how the clevis assembly, clevis, and bullnose hinge lug are attached to each other, and suggested that revising the figures to correct the errors would clarify which parts must be subject to the detailed inspection. \n\tWe acknowledge that Figures 1, 2, 3, and 4 of Boeing Alert Service Bulletin 737-57A1327, Revision 1, dated September 28, 2016, contain errors in the labeling of parts in the illustrations. However, the instructions in the tables in the figures correctly identify the parts and actions to be accomplished. Sincethe instructions are correct, the service bulletin adequately addresses the unsafe condition. We do not revise manufacturers' service information. However, Boeing might decide to revise Boeing Alert Service Bulletin 737-57A1327, Revision 1, dated September 28, 2016, to correct the errors. We have not changed the AD in this regard. \n\nRequest To Allow Alternate Replacement Procedure \n\n\n\tAAL and Southwest Airlines (SWA) requested that we revise the NPRM to provide an option to replace cracked or deformed bullnose hinge lugs or clevis assemblies with bullnose hinge lugs or clevis assemblies instead of replacement with a Krueger flap assembly, as specified in paragraph 3.B.2.a.(1)(a)1) of Boeing Alert Service Bulletin 737- 57A1327, Revision 1, dated September 28, 2016. AAL suggested that the replacement option could be done using certain sections of a component maintenance manual (CMM). SWA suggested the use of Boeing production installation drawings. Both AAL and SWA also stated thatreplacing only the affected bullnose hinge lugs or clevis assemblies would also reduce the cost of repair or replacement. SWA also stated that there is a limited inventory of Krueger flap assemblies and that limited inventory, combined with a 6-month compliance time could significantly impair operators. \n\tWe understand that the suggested replacement option might reduce the burden on operators. However, we do not agree to revise this AD to include the suggested changes. The repairs provided by the suggested sections of the CMM address normal wear-and-tear, and these repairs may not be appropriate for addressing damage that might result from an improperly attached Krueger flap. Boeing informed us that there is no procedure in the CMM that would provide step-by-step instructions to remove only the bullnose other than by use of the drawing system. Engineering instructions would be needed to ensure that the remainder of the flap assembly is serviceable and not damaged in addition to the damaged bullnose hinge lugs or clevis assembly, and that level of instruction would be too much detail for an AD. However, once we issue this AD, any person may request approval of an AMOC under the provisions of paragraph (i) of this AD. We have not changed the AD in this regard. \n\nConclusion \n\n\n\tWe 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. We have determined that these minor changes: \n\tAre consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM. \n\n((Page 39346)) \n\n\n\tWe also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tWe reviewed Boeing Alert Service Bulletin 737-57A1327, Revision 1, dated September 28, 2016. The service information describes procedures for a one-time detailed visual inspection for discrepancies in the Krueger flap bullnose attachment hardware, and related investigative and corrective 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\tWe estimate that this AD affects 1,495 airplanes of U.S. registry. We estimate 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 ---------------------------------------------------------------------------------------------------------------- Inspection ofthe Krueger flap 3 work-hours x $85 per None................ $255 $381,225 \n\tbullnose hardware. hour = $255. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tWe have received no definitive data that would enable us to provide cost estimates for the on-condition actions specified in this AD. \n\tAccording to the manufacturer, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected individuals. We do not control warranty coverage for affected individuals. As a result, we have included all available costs in our 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\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 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 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, 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.