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 737-700 and -700C series airplanes. The NPRM published in the Federal Register on June 28, 2016 (81 FR 41894). The NPRM was prompted by a report that, for airplanes with blended winglets, the nose-up pitch trim limit and associated warning for the horizontal stabilizer control system will allow the stabilizer position to be set outside acceptable limits for a mis-trimmed takeoff condition. The NPRM proposed to require, depending on airplane configuration, replacing the pitch trim light plates on the flight deck control stand, relocating the position warning horn switches of the horizontal stabilizer, revising the software, removing the placard, and doing related investigative and corrective actions if necessary. We are issuing this AD to prevent a stabilizer position set outside acceptable limits for a mis-trimmed takeoff condition. Settings outside of the appropriate pitch trim limits could result in loss of controllability of the airplane during takeoff. \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\n((Page 42582)) \n\nSupport for the NPRM \n\n\n\tAir Line Pilots Association, International (ALPA) stated its support for the NPRM. United Airlines stated that it has no technical objections with the NPRM. \n\nRequest To Use the Latest Service Information \n\n\n\tAviation Partners Boeing requested that the NPRM be updated to include the latest service information, which is Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 3, dated July 19, 2016. \n\tWe agree with the commenter's request. Since the NPRM was issued, we have reviewed Aviation Partners Boeing Service Bulletin AP737-27- 002, Revision 4, dated April 24, 2017, whichprovides minor changes. We have updated this AD to refer to Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017. We have also added credit for Aviation Partners Boeing Service Bulletin AP737-27- 002, Revision 3, dated July 19, 2016. \n\nRequest To Revise Boeing Service Information \n\n\n\tSouthwest Airlines (SWA) requested that Boeing Alert Service Bulletin 737-27A1306, dated September 10, 2015, be revised to reference revised Aviation Partners Boeing service information. SWA stated that Boeing Alert Service Bulletin 737-27A1306, dated September 10, 2015, specifies concurrent accomplishment of Aviation Partners Boeing Service Bulletin AP737-27-002, March 31, 2015. SWA stated that this concurrent requirement should call for the use of Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 2, dated March 1, 2016, as stated throughout the NPRM. \n\tWe acknowledge the commenter's request. After we issued the NPRM, Boeing published Boeing AlertService Bulletin 737-27A1306, Revision 1, dated December 14, 2016, which identifies Aviation Partners Boeing Service Bulletins ''AP737-27-002, Original Issue, Revision 1, Revision 2, or Revision 3,'' as concurrent requirements. Aviation Partners Boeing has since published Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017. We have revised paragraph (g)(2) of this AD to refer to Boeing Alert Service Bulletin 737-27A1306, dated September 10, 2015, as revised by Boeing Alert Service Bulletin 737-27A1306, Revision 1, dated December 14, 2016. As we stated previously, Aviation Partners Boeing has published Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017. Paragraphs (g)(1) and (g)(2) of this AD also refer to Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017. \n\nRequest To Make Service Information Available or Revise the Applicability \n\n\n\tDelta Air Lines (DAL) requested that we either make Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015, available to all operators or revise paragraph (c)(3) of the applicability in the proposed AD to identify specifically affected airplanes. DAL stated that, during its review of the NPRM, it was not able to obtain a copy of Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015. DAL commented that it requested Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015, from Boeing and was advised that the Aviation Partners Boeing service information was not applicable to DAL airplanes, and, therefore, the service information would not be made available to DAL. DAL stated that, as a result, it was unable to independently verify that there are no DAL airplanes identified in Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015. DAL commented that paragraph 1.A.1., ''Aircraft Affected,'' of Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 2, dated March 1, 2016, does identify airplanes having line numbers 384 and 3128 as affected by Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015. DAL stated that, however, paragraph (c)(3) of the proposed AD does not mention Aviation Partners Boeing Service Bulletin AP737-27- 002, Revision 2, dated March 1, 2016, as a method to identify airplanes. \n\tDAL commented that it would prefer that Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015, be available to all operators so that each operator can determine whether or not their airplanes are affected. DAL also stated that if the manufacturer cannot support this, DAL suggested that paragraph (c)(3) in the AD should indicate that Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015, is only applicable to airplanes having line numbers 384 and 3128. \n\tWe partially agree with the commenter's request. We disagree with revising the applicability of thisAD. However, the service information specified in paragraphs (c), (g), and (h) of this AD is incorporated by reference in this AD, and it should be available to all operators, as well as the general public, after the AD is published. We have provided availability information for the required service information in both the preamble and regulatory text of this AD. \n\tWe have also clarified the actions for the airplane having line number 3128. Boeing Alert Service Bulletin 737-27A1306, dated September 10, 2015, as specified in paragraph (c)(2) of this AD, also references line number 3128. Paragraph (g)(2) of this AD refers to Boeing Alert Service Bulletin 737-27A1306, dated September 10, 2015, for accomplishing actions. Paragraph (h) of this AD refers to Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015, for accomplishing actions. For line number 3128, the actions in paragraph (h) of this AD should be done instead of paragraph (g)(2) of this AD. We have revisedparagraph (g)(2) of this AD to exclude line number 3128. \n\tIn addition, we have clarified the actions for airplanes identified in paragraph (c)(2) of this AD by excluding those airplanes from paragraph (g)(1) of this AD. Paragraph (g)(1) of this AD specifies actions for airplanes identified in paragraph (c)(1) of this AD, which includes airplanes that are identified in paragraph (c)(2) of this AD. However, for airplanes identified in paragraph (c)(2) of this AD, the actions specified in paragraph (g)(2) of this AD must be done. \n\nRequest To Exclude Certain Airplanes From the Applicability \n\n\n\tSWA requested that any airplane modified per Supplemental Type Certificate (STC) ST00830SE, Amendment dated April 21, 2015, dated August 26, 2015, or subsequent be excluded from the applicability of the proposed AD. SWA stated that it has recently incorporated STC ST00830SE (Amendment dated April 21, 2015) on airplanes that have not previously had blended winglets installed. SWA commented that the Amendment dated April 21, 2015, of the STC incorporates the intent of Aviation Partners Boeing Service Bulletin AP737-27-002. SWA stated that it is currently incorporating STC ST00830SE, Amendment dated August 26, 2015, on airplanes that have not previously had blended winglets installed. \n\tWe partially agree with the commenter's request. We concur with the assertion that installation of STC ST00830SE at Amendment dated April 21, 2015, fulfills the equivalent actions specified in Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017. In \n\n((Page 42583)) \n\naddition, there are later amendments that apply to Model 737-700 series airplanes that fulfill the actions specified in Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017. We have revised paragraph (c) of this AD to exclude airplanes on which winglets are installed as specified in STC ST00830SE, Amendment dated on or after April 21, 2015. \n\nRequestTo Include Certain Line Numbers in the Applicability \n\n\n\tSWA requested that we include certain line numbers in the applicability of the proposed AD. SWA stated that paragraph 1.A.1., ''Aircraft Affected,'' of Aviation Partners Boeing Service Bulletin AP737-27-002 defines the effectivity of Group 2 airplanes as ''. . . manufacturing line number 3100 and on . . . .'' SWA commented that it is unclear if this modification is being incorporated on the Boeing production line. SWA stated that, if this modification is being incorporated on the Boeing production line, then the manufacturing line number should be identified as the upper end of the effectivity of Aviation Partners Boeing Service Bulletin AP737-27-002 and in the upper end of the proposed applicability. \n\tWe agree that operators need to know which airplanes are affected. However, we disagree with including line numbers in the applicability of this AD, because the Aviation Partners Boeing kit configuration identified in section1.A.1., ''Aircraft Affected,'' of Aviation Partners Boeing Service Bulletin AP737-27-002 clearly identifies the airplanes that need the modification. Airplanes delivered from Boeing with other kit configuration numbers are outside the effectivity, and therefore, do not require the accomplishment of Aviation Partners Boeing Service Bulletin AP737-27-002. We have not changed this AD in this regard. \n\nRequest To Revise the Description of the Unsafe Condition \n\n\n\tBoeing requested that we revise the unsafe condition statement throughout the NPRM, so that it is more consistent with the description specified in the service information. Boeing clarified that accomplishing the proposed requirements will not prevent takeoffs with incorrect trim settings, but rather allows for acceptable takeoff limits at specific airplane configurations in which the stabilizer trim has been set at a maximum mis-trim, as specified in 14 CFR part 25. \n\tWe agree to revise the unsafe condition statement as suggested by Boeing for the reason provided. We have revised this final rule accordingly. \n\nRequest To Revise the Proposed Compliance Time \n\n\n\tALPA requested that we reduce the proposed compliance time from ''72 months after the effective date of this AD'' to ''36 months after the effective date of this AD.'' ALPA commented that it is of the upmost importance to ensure the airplane is taking off in the correct trim setting and the associated warning system has to work properly in order to alert the flight crew of a possible misconfiguration before takeoff. \n\tWe do not agree to reduce the compliance time for the requirements of this AD. We agree that it is important to have the correct configuration of the airplane for takeoff, because of the potential unsafe conditions that incorrect configurations might pose. However, this AD does not address that safety concern. After considering the available information, we have determined that the compliance time, as proposed, represents an appropriate interval of time in which the required actions can be performed in a timely manner within the affected fleet, while still maintaining an adequate level of safety. In developing an appropriate compliance time, we considered the safety implications, parts availability, and normal maintenance schedules for timely accomplishment of the modifications. Further, we arrived at the proposed compliance time with the manufacturer's concurrence. To reduce the proposed compliance time would necessitate (under the provisions of the Administrative Procedure Act) reissuing the notice, reopening the period for public comment, considering additional comments subsequently received, and eventually issuing a final rule. In light of this, and in consideration of the amount of time that has already elapsed since issuance of the original notice, we have determined that further delay of this final rule is not appropriate. However, if additional data are presented that would justify a shorter compliance time, we may consider further rulemaking on this issue. We have not changed this AD in this regard. \n\nRequest To Clarify Certain Acceptable Operator-Supplied Parts \n\n\n\tDAL requested that we clarify the NPRM to specify whether certain alternative lockwire part numbers (P/Ns) are acceptable alternatives to those specified in Aviation Partners Boeing Service Bulletin AP737-27- 002. DAL stated that table 3 of Aviation Partners Boeing Service Bulletin AP737-27-002 calls for the use of lockwire having P/N MS20995NC20 and P/N MS20995NC32. DAL stated that review of parts available on MyBoeingFleet Part Page shows that those part numbers are no longer available. DAL commented that the Part Page provides substitute P/Ns M000200850 and P/N M000320850, respectively. DAL stated that Aviation Partners Boeing Service Bulletin AP737-27-002 includes a note in the Accomplishment Instructions, which refers operators to chapter 51 of the Boeing 737 Structural Repair Manual (SRM) for use of approved fastener and process material substitutions. DAL commented that this SRM reference does not detail any substitutes for the lockwire. DAL stated that, lacking an approval source other than the Boeing Part Page, an alternative method of compliance (AMOC) would be required to use lockwire having P/N M000200850 and P/N M000320850. DAL commented that specifying these would facilitate operator procurement efforts and minimize potential AMOC requests. \n\tWe agree to clarify. Part Number M000200850 and P/N M000320850 are the Boeing stock numbers, which meet the MS20995 lockwire specifications in Aviation Partners Boeing Service Bulletin AP737-27- 002. In addition, specific lockwire part numbers are not included in the Required for Compliance (RC) steps of Aviation Partners Boeing Service Bulletin AP737-27-002. Therefore, we find that it is not necessary to revise this AD to address this issue, and we have not changed this AD in this regard. \n\nRequest To Clarify Recordkeeping RequirementsDAL requested that we exclude the explicit instruction in Note 3 of the Accomplishment Instructions of Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 2, dated March 1, 2016, that specifies making a recordkeeping entry in the airplane records once the service information is completed. DAL requested that, if the exclusion of Note 3 cannot be granted in the AD, the final rule provide an allowance for operators to use their existing recordkeeping procedures to record completion of Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 2, dated March 1, 2016. \n\tDAL commented that its recordkeeping process would track compliance with a specific engineering document number used to embody a specified service bulletin on the airplane. DAL stated that it would not typically record service bulletin accomplishment using a phrase similar \n\n((Page 42584)) \n\nto that given in Note 3 of the Accomplishment Instructions of Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 2, dated March 1, 2016. DAL commented that the requirement to show compliance with the subject service information does not require such explicit requirements. DAL stated that recording the service information exactly as detailed in the note does not improve airplane safety, and therefore, latitude should be given to operators regarding their method for recording compliance with Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 2, dated March 1, 2016. DAL stated that this will prevent the need for future AMOC requests. \n\tWe agree that operators may use their existing recordkeeping processes to document maintenance actions performed using Aviation Partners Boeing Service Bulletin AP737-27-002. For this AD, recordkeeping is not a critical step that addresses the unsafe condition. As DAL pointed out, the actions specified in Note 3 are not called out in an RC step in the Accomplishment Instructions. We have added paragraph (j)(2) to this AD to clarifythat recordkeeping is not required by this AD. \n\nRequest To Clarify the Requirements for the Onboard Performance Tool (OPT) \n\n\n\tDAL requested that we clarify the requirements for incorporating the OPT. DAL stated that Aviation Partners Boeing Service Bulletin AP737-27-002 specifies concurrent actions recommending that users of the OPT contact Boeing for an updated database and instructions on how to incorporate this database into the OPT. DAL commented that it does not use the OPT and that the proposed AD does not give any guidance with respect to this concurrent requirement. DAL commented that the concurrent requirement is actually written as a recommendation, which would imply that it is not a mandatory action and that compliance is optional. \n\tWe agree to provide clarification regarding the OPT. We infer that DAL meant to refer to Aviation Partners Boeing Service Bulletin AP737- 34-005, as there are no concurrent actions specified in Aviation Partners Boeing Service BulletinAP737-27-002. The usage of the OPT, as specified in the concurrent requirements section of Aviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015, is optional and is not a requirement of this AD. We have not changed this AD in this regard. \n\nRequest To Use Later-Approved Software Versions \n\n\n\tSWA requested that the proposed AD allow for the installation of later-approved versions of the Flight Management Computer (FMC) Model Engine Database (MEDB) and/or FMC Operational Program Software (OPS). SWA stated that Part 4 of Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 2, dated March 1, 2016, specifies the installation of FMC MEDB software having P/N BCG-01T-A0 with compatible FMC OPS Versions U10.8A, U11, or U12. SWA commented that if any later versions of FMC MEDB or FMC OPS are installed at a future date an AMOC would be needed to stay in compliance with the AD. \n\tWe disagree with the commenter's request. This AD requires, for certain airplanes, the actions specified in Aviation Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017, which identifies specific software that must be installed. That software must be installed to address the identified unsafe condition. However, under the provisions of paragraph (k) of this AD, we will consider requests for approval of new software if sufficient data are submitted to substantiate that the new software would provide an acceptable level of safety. We have not changed the final rule 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 inthe NPRM. \n\tWe 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\tWe reviewed the following Aviation Partners Boeing service information. \n\tAviation Partners Boeing Service Bulletin AP737-27-002, Revision 4, dated April 24, 2017. This service information describes procedures for replacing the pitch trim light plates on the flight deck control stand, relocating the horizontal stabilizer position warning horn switches, and updating the software for the MEDB of the FMC. \n\tAviation Partners Boeing Service Bulletin AP737-34-005, dated July 17, 2015. This service information describes procedures for updating the software in the MEDB for the FMC and removing a certain placard on the control stand. \n\tWe also reviewed the following Boeing service information. \n\tBoeing Alert Service Bulletin 737-27A1306, dated September 10, 2015. This service informationdescribes procedures for replacing the pitch trim light plates on the flight deck control stand, relocating the position warning horn switches of the horizontal stabilizer, and installing new software for the MEDB for the FMC. \n\tBoeing Alert Service Bulletin 737-27A1306, Revision 1, dated December 14, 2016. This service information is a short form revision that specifies changes to the concurrent requirements and the affected publications identified in Boeing Alert Service Bulletin 737- 27A1306, dated September 10, 2015. \n\tThis 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 569 airplanes of U.S. registry. \n\tWe 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 -------------------------------------------------------------------------------------------------------------------------------------------------------- Relocation................................. Up to 4 work(dash)hours x $0 Up to $340.................... Up to $193,460. \n\t$85 per hour = $340. Replacement................................ Up to 3 work(dash)hours x 1,973 Up to $2,228.................. Up to $1,267,732. \n\t$85 per hour = $255. Software installation...................... 2 work-hours x $85 per hour 0 $170.......................... $96,730. \n\t= $170. \n\n((Page 42585)) \n\n\n\nPlacard removal (2 airplanes).............. 1 work-hour x $85 per hour 0 $85........................... $170. \n\t= $85. -------------------------------------------------------------------------------------------------------------------------------------------------------- \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 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.