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 October 13, 2016 (81 FR 70647). The NPRM was prompted by reports of PSUs becoming detached from the supporting airplane structure in several Model 737 series airplanes during survivable accidents. The NPRM proposed to require modifying the PSUs and life vest panels by removing the existing inboard lanyard and installing two new lanyards on the outboard edge of the PSUs and life vest panels. \n\n((Page 7267)) \n\n\n\tWe issued a supplemental NPRM (SNPRM) 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 SNPRM published in the Federal Register on September 14, 2018 (83 FR 46666). We issued the SNPRM to add airplanes to the applicability, add a measurement of the distance between the hooks of the torsion spring of the lanyard assembly, replace discrepant lanyard assemblies, and re- identify serviceable lanyard assemblies. \n\tWe are issuing this AD to address PSUs and life vest panels detaching from the supporting airplane structure, which could lead to passenger injuries and impede passenger and crew egress during evacuation. \n\nComments \n\n\n\tWe gave the public the opportunity to participate in developing this final rule. The following presents the comments received on the SNPRM and the FAA's response to each comment. \n\nRequest To Include PSU-Mounted Liquid Crystal Display (LCD) Panels \n\n\n\tJeJu Air requested that we consider adding actions similar to those in the SNPRM for PSU-mounted LCD panels. JeJu Air noted that they experienced an incident in which four PSU-mounted LCD panels dropped during flight, resulting in minor injuries to several passengers. JeJuAir stated that PSU-mounted LCD panels are not subject to routine inspections through a manufacturer's maintenance planning document. The commenter added that the PSU-mounted LCD panels are heavier than normal PSUs and therefore could be riskier for passengers if they fall. \n\tWe acknowledge the commenter's concern. However, making the requested change would require issuance of a second SNPRM with another public comment period, delaying the issuance of a final rule. To delay this action would be inappropriate, since we have determined that an unsafe condition exists and that PSU modifications and lanyard replacements must be made to ensure continued safety. We will consider additional rulemaking to address PSU-mounted LCD panels. We have not changed this AD in this regard. \n\nRequest To Revise the Applicability \n\n\n\tBoeing requested that we revise the applicability of the proposed AD (in the SNPRM) to The Boeing Company Model 737-600, -700, -700C, - 800, -900, and -900ER series airplanes ''as identified in Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018.'' Boeing stated that including airplanes beyond those identified in Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018, would not add to the safety of the operating fleet. Boeing added that airplanes with potentially affected lanyard assemblies, whether included in reworked airplanes, installed during production, or issued in kits, are all categorized and addressed in Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018. \n\tWe disagree with the commenter's request. The PSUs and lanyard assemblies are rotable parts that can be installed on airplanes that previously did not have affected PSUs and lanyard assemblies installed. Therefore, the applicability of this AD, ''all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes, certificated in any category, without a Boeing Sky Interior (BSI),'' ensures that no PSUs without the updated lanyard assemblies are installed and the unsafe condition is addressed on all affected airplanes. We have not changed this AD in this regard. \n\nRequest To Correct a Service Bulletin Effectivity Range \n\n\n\tBoeing requested that we revise the ''Differences Between This SNPRM and the Service Information'' section of the SNPRM to note that the effectivity of Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018, is limited to ''line numbers 1 through 6099,'' rather than ''line numbers 1 through 6009.'' \n\tWe acknowledge this typographical error. However, the ''Differences Between This SNPRM and the Service Information'' section does not carry over into this AD. Therefore, we have not changed this AD in this regard. \n\nRequest To Remove a Requirement To Add an Identifying Mark \n\n\n\tAmerican Airlines (AAL) requested that we remove a requirement in the proposed AD (in the SNPRM) to identify new lanyard assemblies as serviceable by adding a permanent white mark. AAL noted that Figure 1, step 3 of Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018, which is Required for Compliance (RC), says to ''Identify the lanyard assembly as serviceable with a permanent white mark, that can be easily seen when the PSU is lowered.'' The commenter stated that new lanyards received in certain kits are deemed serviceable, but not identified with a white mark. AAL asked why the parts would be marked at installation rather than inspection or fabrication, which seems to place the burden on installers to determine the lanyard assembly is serviceable. \n\tWe disagree with the commenter's request. Some previously delivered lanyard assembly kits contained lanyards that were manufactured incorrectly and might not properly secure the PSU in the event of an accident. By inspecting and identifying the lanyard assembly during installation, operators can ensure that the correct lanyard assembly is installed on an airplane. On some airplanes, a correct lanyard assembly may already be installed and only needs to be identified with a white mark. Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018, clearly identifies a serviceable lanyard assembly, and the white mark is an important part of that definition. We have not changed this AD in this regard. \n\nRequest To Provide More Details on PSU Removal and Installation \n\n\n\tAAL requested that the Boeing 737NG Aircraft Maintenance Manual (AMM) 25-23-61 provide more detailed instructions for removing and installing the PSU. AAL noted that Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018, provides detailed instructions for attaching the lanyard clip to the PSU rail, but the AMM does not provide the same level of instructions. We infer that the commenter is asking us to require Boeing to update the AMM to provide more details. \n\tWe acknowledge the commenter's request. The AMM is identified as an affected publication in Boeing Service Bulletin 737-25-1707, Revision 1,dated May 18, 2018; however, this AD does not require compliance with the AMM, and the AMM is not part of an RC step in the service bulletin. The AMM is referred to as one source of information for removing and installing the PSU, but as noted in paragraph (i)(4)(ii) of this AD, operators may rely on their own accepted methods in accordance with the operator's maintenance or inspection program for those steps. In addition, Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018, provides adequate details to address the unsafe condition in this AD. Therefore, we have not changed this AD in this regard. \n\nRequest To Revise the Costs of Compliance \n\n\n\tAAL stated that Boeing Service Bulletin 737-25-1707, dated September 24, 2015, provided a work-hours task total of 1.35 work-hours per PSU. The commenter added that Boeing Service \n\n((Page 7268)) \n\nBulletin 737-25-1707, Revision 1, dated May 18, 2018, increased the scope of work done on the PSU, but reduced the work-hours task total to 0.4 work-hours per PSU. We infer that the commenter is suggesting that the work-hour estimates should be revised in the final rule. \n\tWe agree to clarify the Costs of Compliance section of this AD. Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018, separates the work-hour estimates into multiple tables based on group configurations and the type of work to be done. Adding all of the work- hours from the applicable tables for a given configuration, the total work-hours estimate is higher for certain configurations. Therefore, the estimated costs in this AD represent the highest work-hours and parts cost for all configurations. We have not changed this 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 final rule as proposed, except for minor editorial changes. We have determined that these minor changes: \n\tAre consistent with the intent that was proposed in the SNPRM for addressing the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the SNPRM. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tWe reviewed Boeing Service Bulletin 737-25-1707, Revision 1, dated May 18, 2018. This service information describes procedures for modifying the PSUs and life vest panels by replacing the existing inboard lanyard and installing two new lanyards on the outboard edge of the PSUs and life vest panels, measuring the distance between the hooks of the torsion spring of the lanyard assembly, replacing any discrepant lanyard assemblies, and re-identifying serviceable lanyard assemblies. 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 2,015 airplanes of U.S.registry. We estimate the following costs to comply with this AD: \n\n\n\tEstimated Costs -------------------------------------------------------------------------------------------------------------------------------------------------------- \n\tAction Labor cost Parts cost Cost per product Cost on U.S. operators -------------------------------------------------------------------------------------------------------------------------------------------------------- Measurement and modification........ Up to 75 work-hours x $85 Up to $11,760......... Up to $18,135......... Up to $36,542,025. \n\tper hour = Up to $6,375. -------------------------------------------------------------------------------------------------------------------------------------------------------- \n\n\n\tAccording to the manufacturer, some or all 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 known 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 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 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.