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 737-100, -200, -200C, -300, -400, and -500 series airplanes. The NPRM published in the Federal Register on November 30, 2015 (80 FR 74731) (''the NPRM''). The NPRM was prompted by an evaluation by the DAH indicating that the aft pressure bulkhead is subject to WFD. The NPRM proposed to require repetitive inspections of the aft pressure bulkhead web for any cracking, incorrectly drilled fastener holes, and elongated fastener holes, and related investigative and corrective actions, if necessary. We are issuing this AD to detect and correct fatigue cracking of the aft pressure bulkhead web at the ''Y''-chord, which could result in reduced structural integrity of the airplane and rapid decompression of the fuselage. \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\nEffect of Winglets on Accomplishment of the Proposed Actions \n\n\n\tAviation Partners Boeing stated that the installation of winglets per supplemental type certificate (STC) ST01219SE does not affect the accomplishment of the manufacturer's service instructions. \n\tWe agree with the commenter. We have redesignated paragraph (c) of the NPRM as paragraph (c)(1) in this final rule and added a new paragraph (c)(2) to state that STC ST01219SE does not affect the mitigating action or accomplishment of the actions required by this final rule. Therefore, for airplanes on which STC ST01219SE is installed, ''a change in product'' alternative method of compliance (AMOC) approval request is not necessary to comply with the requirements of 14 CFR 39.71. \n\nRequest To Clarify the Proposed Requirements of the NPRM \n\n\n\tMr. Cas Lausberg stated that the subject of the NPRM is addressed in AD 99-08-23, Amendment 39-11132 (64 FR 19879, April 23, 1999) (''AD 99-08-23''), which was superseded by AD 2012-18-13 R1, Amendment 39- 17429 (78 FR 27020, May 9, 2013) (''AD 2012-18-13 R1''). The commenter questioned the need for the new NPRM. \n\tWe agree to provide clarification. As stated in the ''Discussion'' section of the NPRM, this final rule is being issued as part of the overall joint effort by Boeing and the FAA to satisfy requirements of the FAA's WFD final rule (75 FR 69746, November 15, 2010), which became effective on January 14, 2011. The inspections required by AD 99-08-23 and AD 2012-18-13 R1 do not address WFD concerns. However, Boeing Alert Service Bulletin 737-53A1214, Revision 5, dated January 30, 2015, addresses WFD with new inspection requirements, which incorporate a compliance time (threshold) corresponding to the WFD inspection start point (ISP) and shorter repetitive intervals where indicated. These requirements are included in this AD. We have not changed this AD in this regard. \n\nRequest To Revise the Term ''Global Fatigue Damage'' \n\n\n\tBoeing requested that the term ''global fatigue damage'' be changed to ''widespread fatigue damage'' in the NPRM. Boeing stated that this is the first time it has seen the term ''global'' used to describe WFD. Boeing commented that it is better not to introduce a new term. \n\tWe agree with the commenter. Although the ''Discussion'' section of the proposed rule is not carried over into the final rule, we agree that the term ''global fatigue damage'' should not be introduced as a new term. We have not changed this AD in this regard. \n\nRequest To Correct Reference to Group 1 LOV (Limit of Validity) \n\n\n\tBoeing requested that we change the wording in the ''Differences Between This Proposed AD and the Service Information'' paragraph of the NPRM, which referred to WFD-based inspections specified in certain tables of Boeing Alert Service Bulletin 737-53A1214, Revision 5, dated January 30, 2015. The NPRM stated that the WFD-based inspections would affect only Group 2 airplanes because Group 1 airplanes will reach their LOV before the compliance times specified ''in tables 9, 10, and 11'' of Boeing Alert Service Bulletin 737-53A1214, Revision 5, dated January 30, 2015. \n\tBoeing stated that the inspections listed in tables 9, 10, and 11 of Boeing Alert Service Bulletin 737-53A1214, Revision 5, dated January 30, 2015, also include non-WFD inspections that are required prior to the ISP threshold of 76,000 cycles. Boeing stated that, therefore, it is not true to say that Group 1 airplanes will reach their limit of validity before the compliance times specified in tables 9, 10 and 11. \n\tWe partially agree with the commenter. Although the ''Differences Between This Proposed AD and the Service Information'' paragraph of the proposed rule is not carried over into the final rule, we agree to provide clarification. \n\tSince AD 2012-18-13 R1 was issued, Boeing issued Alert Service Bulletin 737-53A1214, Revision 5, dated January 30, 2015. Affected airplanes are now divided into two groups: Group 1, line numbers 1 through 2565 inclusive; and Group 2, line numbers 2566 through \n\n((Page 72513)) \n\n3132 inclusive. Boeing's evaluation determined that inspections to address WFD concerns are required for the aft pressure bulkhead web at the ''Y'' chord at an ISP of 76,000 total flight cycles. Since Group 1 airplanes will reach their LOV of 75,000 total flight cycles (34,000 total flight cycles for line numbers 1 through 291 inclusive), which is prior to this ISP, no WFD inspections are provided for those airplanes. For Group 2 airplanes, which have an LOV of 85,000 total flight cycles, new tables 9, 10, and 11 of Boeing Alert Service Bulletin 737-53A1214, Revision 5, dated January 30, 2015, include inspections to address WFD. We have not changed this AD in this regard. \n\nRequest To Clarify the Applicability \n\n\n\tBoeing requested that we clarify the applicability of the proposed AD. Boeing stated that Model 737-100, -200, and -200C airplanes should be removed from the ''Applicability'' paragraph. Boeing stated that the Group 2 airplanes only include Model 737-300, -400, and -500 airplanes. \n\tWe agree with the commenter's request for the reasons stated above. We have revised the applicability in paragraph (c) of this AD to remove Model 737-100, -200, and -200C series airplanes and revised the SUMMARY section to specify certain Model 737-300, -400, and -500 series airplanes. \n\nRequest To Clarify Airplanes Affected by Terminating Action Provisions \n\n\n\tBoeing requested that we change the wording for the terminating action in paragraph (j) of the proposed AD. Boeing stated that the paragraph should specify that the terminating action applies only to Group 2 airplanes. Boeing stated that specifying Group 2 airplanes clearly states the intent of the terminating action. \n\tWe agree with the commenter's request for the reasons stated above. We have expanded the structure of paragraph (j) of this AD accordingly. In addition, we have clarified that the terminating action does not apply to stringer S-5L to S-7L and stringer S-5R to S-9R, as specified in AD 2012-18-13 R1 and Boeing Alert Service Bulletin 737-53A1214, Revision 5, dated January 30, 2015. \n\nRequest To Revise the Inspections for Group 2 Airplanes \n\n\n\tAll Nippon Airways (ANA) requested that we revise the inspection requirements in the proposed AD for Group 2 airplanes. ANA requested that we either mandate the inspections in tables 10 and 11 of Boeing Alert Service Bulletin 737-53A1214, Revision 5, dated January 30, 2015, for only Group 2 airplanes with 76,000 flight cycles and more, or create a new NPRM to supersede AD 2012-18-13 R1 to mandate all inspection requirements using Boeing Alert Service Bulletin 737- 53A1214, Revision 5, dated January 30, 2015. ANA stated that if a new proposed rule is created, it requests that credit be given for any previously approved AMOCs to AD 2012-18-13 R1, to reduce additional burden for operators and the FAA. \n\tWe agree with the commenter's request for the reasons stated by the commenter. The intent of this final rule is to address the WFD concerns in accordance with the FAA's WFD final rule (75 FR 69746, November 15, 2010). We have revised paragraphs (g), (h), and (l) of this AD accordingly. \n\nAdditional Changes to This AD \n\n\n\tIn paragraphs (g) and (h) of this AD, we have clarified the compliance times by explicitly stating the compliance times instead of referring to the compliance tables in paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1214, Revision 5, dated January 30, 2015. \n\tThe actions in paragraph (h) of the proposed AD states to do detailed and eddy current inspections of the aft pressure bulkhead web from the forward or aft side of the bulkhead for any cracking, incorrectly drilled fastener hole, and elongated fastener hole. In this AD, we have clarified the actions by providing theoperators the option of doing detailed and LFEC inspections from the aft side of the aft pressure bulkhead, or doing a detailed and HFEC inspections from the forward side of the aft pressure bulkhead, for any cracking, incorrectly drilled fastener hole, and elongated fastener hole. \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\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 737-53A1214,Revision 5, dated January 30, 2015. The service information describes procedures for, among other actions, repetitive inspections of the aft pressure bulkhead web for any cracking, incorrectly drilled fastener holes, and elongated fastener holes; 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 122 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost on U.S. \n\tAction Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Inspections of the web at the Up to 60 work-hours x $0 Up to $5,100 per Up to $622,200 \n\t''Y''-chord. $85 per hour = Up to inspection cycle. per inspection \n\t$5,100 per inspection cycle. \n\tcycle. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tWe have received no definitive data that will enable us 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\tWe are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: \n\n((Page 72514)) \n\n''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\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.