AD 2015-23-08

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100,-200,-200C,-300,-400, and -500 series airplanes. This AD was prompted by reports of cracks in fuselage frames, and a report of a missing strap that was not installed on a fuselage frame during production. This AD requires an inspection to determine if the strap adjacent to a certain stringer is installed, and repair if it is missing; repetitive inspections of the frame for cracking or a severed frame web; and related investigative and corrective actions if necessary. This AD also provides optional actions to terminate certain repetitive inspections. We are issuing this AD to detect and correct missing fuselage frame straps and frame cracking that can result in severed frames which, with multiple adjacent severed frames, or the combination of a severed frame and fuselage skin chemical mill cracks, can result in uncontrolled decompression of the airplane.

Final rule.

Adoption of the Amendment \n\n\n\tAccordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: \n\nPART 39--AIRWORTHINESS DIRECTIVES \n\n0 1. The authority citation for part 39 continues to read as follows: \n\n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n\n\nSec. 39.13 (Amended) \n\n0 2. The FAA amends Sec. 39.13 by adding the following new airworthiness directive (AD): \n\n2015-23-08 The Boeing Company: Amendment 39-18324; Docket No. FAA- 2014-0436; Directorate Identifier 2014-NM-010-AD. \n\n(a) Effective Date \n\n\n\tThis AD is effective January 4, 2016. \n\n(b) Affected ADs \n\n\n\tNone. \n\n(c) Applicability \n\n\n\t(1) This AD applies to The Boeing Company Model 737-100, -200, - 200C, -300, -400, and -500 series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 737- 53A1323, dated December 6, 2013. \n\t(2) Installation of Supplemental Type Certificate (STC) ST01219SE (http://rgl.faa.gov/Regulatory_and_Guidance_Library/ rgstc.nsf/0/ebd1cec7b301293e86257cb30045557a/$FILE/ST01219SE.pdf) does not affect the ability to accomplish the actions required by this AD. Therefore, for airplanes on which STC ST01920SE 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\n(d) Subject \n\n\n\tAir Transport Association (ATA) of America Code 53, Fuselage. \n\n(e) Unsafe Condition \n\n\n\tThis AD was prompted by reports of cracks in fuselage frames, and a report of a missing strap that was not installed on a fuselage frame during production. We are issuing this AD to detect and correct missing fuselage frame straps and frame cracking that can result in severed frames. Continued operation of the airplane with multiple adjacent severed frames, or the combination of a severed frame and fuselage skin chemical mill cracks, can result in uncontrolled decompression of the airplane.(f) Compliance \n\n\n\tComply with this AD within the compliance times specified, unless already done. \n\n(g) Actions for Group 1 Airplanes \n\n\n\tFor airplanes identified as Group 1 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013: At the applicable time specified in table 1 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as provided by paragraph (n)(1) of this AD, do the inspection for cracking of the frames and applicable repairs using a method approved in accordance with the procedures specified in paragraph (q) of this AD. \n\n(h) Groups 2 Through 7 Airplanes: Inspection for Strap Installation at Station 312 \n\n\n\tFor airplanes identified as Groups 2 through 7 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013: At the applicable time specified in tables 2 and 3 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as provided by paragraph (n)(1) of this AD, do a general visual inspection of the frame at station 312 to determine if the strap adjacent to stringer S-22 right is installed, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. If the strap is not installed, before further flight, repair using a method approved in accordance with the procedures specified in paragraph (q) of this AD. \n\n(i) Groups 2 Through 6 Airplanes With Less Than 28,300 Total Flight Cycles: Repetitive Inspections, Related Investigative Actions, and Corrective Actions at Stations 328, 344, and 360 \n\n\n\tFor airplanes identified as Groups 2 through 6 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, that have accumulated less than 28,300 total flight cycles as of the effective date of this AD: Do the actions required by paragraphs (i)(1) and (i)(2) of this AD. Operators may do the repair of the frame at station 328 as specified in paragraph (m) of this AD as an optional preventive modification for that frame. \n\t(1) At the applicable times specified in tables 4, 5, 7, and 8 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as provided by paragraphs (n)(1) and (n)(3) of this AD: Do detailed and eddy current inspections of the frame at stations 328, 344, and 360, as applicable, for cracking or a severed frame web; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as specified in paragraph (n)(2) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the applicable inspections thereafter at the applicable time and intervals specified in paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, until the inspection required by paragraph (i)(2) of this AD is done. \n\t(2) At the applicable time specified in tables 4, 5, 7, and 8 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, do the actions specified in paragraph (i)(2)(i) or (i)(2)(ii) of this AD. Accomplishing the initial inspections required by paragraph (i)(2) of this AD terminates the inspections required by paragraph (i)(1) of this AD. \n\t(i) Do detailed and eddy current inspections of the frame at stations 328, 344, and 360, as applicable, for cracking or a severed frame web; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as specified in paragraph (n)(2) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the inspections specified in this paragraph thereafter at the applicable time and intervals specified in paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. \n\t(ii) Do detailed and eddy current inspections of the frame at stations 328, 344, and 360, as applicable, for cracking or a severed frame web; and external detailed and eddy current inspections of the fuselage skin for cracking; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737- 53A1323, dated December 6, 2013, except as specified in paragraph (n)(2) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the inspections specified in this paragraph thereafter at the applicable time and intervals specified in paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. \n\n(j) Groups 2 Through 6 Airplanes With 28,300 Total Flight Cycles or More: Repetitive Inspections, Related Investigative Actions, and Corrective Actions at Stations 328, 344, and 360 \n\n\n\tFor airplanes identified as Groups 2 through 6 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, that have accumulated 28,300 total flight cycles or more as of the effective date of this AD: At the applicable times specified in tables 4, 5, 7, and 8 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as provided by paragraphs (n)(1) and (n)(3) of this AD, do the inspections specified in paragraph (j)(1) or (j)(2) of this AD; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as specified in paragraph (n)(2) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the applicable inspections specified in paragraph (j)(1) or \n\n((Page 73954)) \n\n(j)(2) of this AD thereafter at the applicable time and intervals specified in paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. Operators may do the repair of the frame at station 328, as specified in paragraph (m) of this AD, as an optional preventive modification for that frame. \n\t(1) Do detailed and eddy current inspections of the frame at stations 328, 344, and 360, as applicable, for cracking or a severed frame web. \n\t(2) Do detailed and eddy current inspections of the frame at stations 328, 344, and 360, as applicable, for cracking or a severed frame web; and external detailed and eddy current inspections of the fuselage skin for cracking. \n\n(k) Group 7 Airplanes: Repetitive Inspections, Related Investigative Actions, and Corrective Actions at Station 328 \n\n\n\tFor airplanes identified as Group 7 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013: At the applicable time specified in table 6 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as provided by paragraph (n)(1) of this AD, do a detailed inspection and eddy current inspection of the frame at station 328 for cracking or a severed frame web; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as specified in paragraph (n)(2) of this AD. Do all applicable related investigative and corrective actions before further flight. Repeat the inspections specified in this paragraph thereafter at the applicable time and intervals specified in paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. Operators may do the repair of the frame at station 328, as specified in paragraph (m) of this AD, as an optional preventive modification for that frame. \n\n(l) Groups 2 Through 5 Airplanes: Repetitive Inspections, Related Investigative Actions, and Corrective Actions at Station 380 \n\n\n\tFor airplanes identified as Groups 2 through 5 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013: At the applicable time specified in tables 9 and 10 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as provided by paragraph (n)(1) of this AD, do detailed and eddy current inspections of the frame at station 380 for cracking or a severed frame web; and do all applicable corrective actions; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as specified in paragraph (n)(2) of this AD. Do all applicable corrective actions before further flight. Repeat the inspections specified in this paragraph thereafter at the applicable time and intervals specified in paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, datedDecember 6, 2013. \n\n(m) Terminating Actions for Airplanes Identified as Groups 2, 3, 4, 5, 6, and 7 \n\n\n\t(1) For airplanes identified as Groups 2, 3, 4, 5, and 7 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013: Accomplishing the repair or preventive modification of the frame at station 328, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as required by paragraph (n)(2) of this AD, terminates the inspections of that frame required by paragraphs (i), (j), and (k) of this AD. \n\t(2) For airplanes identified as Groups 2, 3, 4, and 5 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013: Accomplishing the repair or preventive modification of the frame at station 328 and the preventive modification of the frame at station 360, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as required by paragraph (n)(2) of this AD, terminates the inspections of the frame at station 344 and the fuselage skin inspections required by paragraphs (i) and (j) of this AD. \n\t(3) For airplanes identified as Groups 2, 3, 4, and 5 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013: Accomplishing the repair or preventive modification of the frame at station 360, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as required by paragraph (n)(2) of this AD, terminates the inspections of that frame required by paragraphs (i) and (j) of this AD. \n\t(4) For airplanes identified as Group 6 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013: Accomplishing the repair or preventive modification of the frame at station 328, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, except as required by paragraph (n)(2) of this AD, terminates the fuselage skin inspections and the station 328 frame inspections required by paragraphs (i) and (j) of this AD. \n\n(n) Exceptions to Service Information \n\n\n\t(1) Where Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, specifies a compliance time after the ''original issue date of this service bulletin,'' this AD requires compliance within the specified compliance time after the effective date of this AD. \n\t(2) If any cracking is found during any inspection required by this AD, and Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, specifies to contact Boeing for appropriate action: Before further flight, repair the cracking using a method approved in accordance with the procedures specified in paragraph (q) of this AD. \n\t(3) The Condition column of Tables 4, 5, 7, and 8 in paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, refers to total flight cycles ''at the original issue date of this service bulletin.'' This AD, however, applies to the airplanes with the specified total flight cycles as of the effective date of this AD. \n\n(o) Post-Repair Inspections and Post-Modification Inspections \n\n\n\t(1) The post-repair and post-modification inspections specified in tables 13 through 15 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, are not required by this AD. \n\t(2) The post-repair and post-modification inspections specified in Tables 13 through 15 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, may be used in support of compliance with section 121.1109(c)(2) or 129.109(b)(2) of the Federal Aviation Regulations (14 CFR 121.1109(c)(2) or 14 CFR 129.109(b)(2)). The corresponding actions specified in the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, are not required by this AD. \n\n(p) Credit for Previous Actions \n\n\n\tThis paragraph provides credit for repairs of the station 328, 344, 360, and 380 frames in the areas addressed by this AD that have been approved by the Boeing Organization Designation Authorization (ODA) via FAA Form 8100-9 (Statement of Compliance with Airworthiness Standards) prior to the effective date of this AD for the repairs specified in paragraphs (i), (j), (k), and (l) of this AD. \n\n(q) Alternative Methods of Compliance (AMOCs) \n\n\n\t(1) The Manager, Los Angeles Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the ACO, send it to the attention of the person identified in paragraph (r) of this AD. Information may be emailed to: 9-ANM-LAACO-AMOC-Requests@faa.gov. \n\t(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office. \n\t(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD if it is approved by the Boeing Commercial Airplanes Organization Designation Authorization that has been authorized by the Manager, Los Angeles ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane, and the approval must specifically refer to this AD. \n\n(r) Related Information \n\n\n\tFor more information about this AD, contact Galib Abumeri, Aerospace Engineer, Airframe Branch, ANM-120L, FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5324; fax: 562-627-5210; email: galib.abumeri@faa.gov. \n\n(s) Material Incorporated by Reference \n\n\n\t(1) The Director of the Federal Register approved the incorporation by reference \n\n((Page 73955)) \n\n(IBR) of the service information listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51. \n\t(2) You must use this service information as applicable to do the actions required by this AD, unless this AD specifies otherwise. \n\t(i) Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. \n\t(ii) Reserved. \n\t(3) For service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, WA 98124-2207; telephone 206-544- 5000, extension 1; fax 206-766-5680; Internet https://www.myboeingfleet.com. \n\t(4) You may view this service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, WA. For information on the availability of this material at the FAA, call 425-227-1221. \n\t(5) You may view this service information that is incorporated by reference at the National Archives andRecords Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibr-locations.html.

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 June 30, 2014 (79 FR 36672). The NPRM was prompted by reports of cracks in fuselage frames, and a report of a missing strap that was not installed on a fuselage frame during production. The NPRM proposed to require an inspection to determine if the strap adjacent to a certain stringer is installed, and repair if it is missing; repetitive inspections of the frame for cracking or a severed frame web; and related investigative and corrective actions if necessary. The NPRM also provided optional actions to terminate certain repetitive inspections. We are issuing this AD to detect and correct missing fuselage frame straps and frame cracking that can result in severed frames. Continued operation of the airplane with multiple adjacent severed frames, or the combination of a severed frame and fuselage skin chemical mill cracks, can result in uncontrolled decompression of the airplane. \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 (79 FR 36672, \n\n((Page 73950)) \n\nJune 30, 2014) and the FAA's response to each comment. \n\nEffect of Winglets on AD \n\n\n\tAviation Partners Boeing stated that installation of winglets per Supplemental Type Certificate (STC) ST01219SE (http://rgl.faa.gov/ Regulatory_and_Guidance_Library/rgstc.nsf/0/ ebd1cec7b301293e86257cb30045557a/$FILE/ST01219SE.pdf) does not affect the actions specified in the NPRM (79 FR 36672, June 30, 2014. \n\tWe concur with the commenter. We have redesignated paragraph (c) of the proposed AD (79 FR 36672, June 30, 2014) as paragraph (c)(1) of this AD, and have added a new paragraph (c)(2) to this AD to state that installation of STC ST01219SE (http://rgl.faa.gov/ Regulatory_and_Guidance_Library/rgstc.nsf/0/ ebd1cec7b301293e86257cb30045557a/$FILE/ST01219SE.pdf) does not affect the ability to accomplish the actions required by this AD. 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 39.17. \n\nRequest To Revise Preamble Wording \n\n\n\tBoeing noted that the SUMMARY of the NPRM (79 FR 36672, June 30, 2014) explained that some optional actions would terminate ''certain'' repetitive inspections. Boeing requested that we use this same wording in the Proposed AD Requirements section of the NPRM (which omitted the word ''certain''). \n\tAlthough we agree with the commenter's statement, the Proposed AD Requirements section is not repeated in a final rule. Since the referenced omission does not affect the required actions or the unsafe condition, no changes to this final rule are needed. \n\nRequest To Specify Inspection Method \n\n\n\tBoeing requested that we add an inspection in paragraph (g) of the proposed AD (79 FR 36672, June 30, 2014). Boeing stated that this is consistent with the compliance information described in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. \n\tWe agree with the commenter's request. We inadvertently omitted the inspection requirement in paragraph (g) of the proposed AD (79 FR 36672, June 30, 2014), which is described in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. We have revised paragraph (g) of this AD to require that the inspection and applicable repair be done by using a method approved in accordance with the procedures specified in paragraph (q) of this AD. Paragraph (g) of this AD applies only to airplanes identified as Group 1 in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. Currently, there are no Group 1 airplanes in service in the United States, so notice of this new requirement is not necessary. \n\nRequest To Revise Terminating Action Wording \n\n\n\tBoeing requested that we revise the wording in paragraphs (i) and (j) of the proposed AD (79 FR 36672, June 30, 2014) to state the following actions. \n\tDoing the repair or preventive modification of the frame at station 328 terminates the applicable repetitive inspection requirements. \n\tDoing the preventive modification of the frame at station 360 terminates the applicable station 360 inspection requirements. \n\tDoing the repair or preventive modification of the frame at station 328, and doing the preventive modification of the frame at station 360 terminates the applicable repetitive inspection requirements of the frame at station 344, and the Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, skin inspections. \n\tBoeing stated that the proposed wording in paragraphs (i) and (j) of the proposed AD (79 FR 36672, June 30, 2014) is not clear. Boeing stated that inspections of the frame at station 328 or at station 360 can be terminated by a single action (applicable repair or modification). Boeing explained that accomplishing both specified actions at station 328 and station 360 terminates the station 344 frame inspections and the option 2 skin inspections. \n\tWe agree to clarify the acceptable terminating actions. We have added new paragraph (m) of this AD, which provides the following terminating actions. We have redesignated subsequent paragraphs accordingly. \n\tAccomplishing the repair or preventive modification of the frame at station 328 terminates the inspections of that frame required by paragraphs (i), (j), and (k) of this AD. \n\tAccomplishing the repair or preventive modification of the frame at station 328 and the preventive modification of the frame at station 360, terminates the inspections of the frame at station 344 and the fuselage skin inspections required by paragraphs (i) and (j) of this AD. \n\tAccomplishing the repair or preventivemodification of the frame at station 360 terminates the inspections of that frame required by paragraphs (i) and (j) of this AD. \n\tAccomplishing the repair or preventive modification of the frame at station 328 terminates the fuselage skin inspections and the station 328 frame inspections required by paragraphs (i) and (j) of this AD. \n\nRecommendation To Specify Optional Preventive Modification \n\n\n\tBoeing recommended that we specify in paragraphs (i) and (j) of the proposed AD (79 FR 36672, June 30, 2014) that the station 328 repair described in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, can be used as an optional preventive modification. \n\tWe partially agree with the commenter's request. The commenter's request is already addressed in the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. However, additional text might help clarify this provision. We have added additional text to paragraphs (i), (j), and (k)of this AD that operators may do the repair of the frame at station 328, as specified in paragraph (m) of this AD, as an optional preventive modification for that frame. \n\nRequests To Revise Paragraph Format and Inspection Method \n\n\n\tBoeing requested that we revise paragraphs (i) and (j) of the proposed AD (79 FR 36672, June 30, 2014) by moving the requirements for Group 6 airplanes to a new paragraph. Boeing stated that the service information for Group 6 airplanes provides directed inspection instructions for the station 328 frame only, as provided in table 5 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737- 53A1323, dated December 6, 2013. Boeing added that for Group 6 airplanes, there are no directed inspections for station 344 or station 360, but there are related investigative and corrective actions for detailed inspections of the frame at station 312 and station 344. \n\tSouthwest Airlines (SWA) requested that we specify that the frame at station 344requires detailed inspections, not detailed and eddy current inspections. SWA stated that Boeing Alert Service Bulletin 737- 53A1323, dated December 6, 2013, describes only detailed inspections at station 344. \n\tWe partially agree with both commenters. We disagree with making the changes requested by the commenters. However, we agree that certain actions are only done at certain locations and for certain airplanes. The inspections at station 344 are detailed inspections only. Application of the \n\n((Page 73951)) \n\nappropriate inspection method to a given frame is addressed by the phrase ''as applicable,'' i.e., actions are applicable to the frames identified in the service information for each group of airplane. We have revised paragraphs (i)(1), (i)(2)(i), (i)(2)(ii), (j)(l), and (j)(2) of this AD by adding ''as applicable'' after the station locations. This revision clarifies that those actions are done only as specified in the service information. \n\nRequest To Add Sub-Paragraph Headers \n\n\n\tBoeing requested that we add the subtitles ''Initial Inspections'' and ''Follow-on Inspections'' to paragraphs (i)(1) and (i)(2), respectively, of the proposed AD (79 FR 36672, June 30, 2014). Boeing also requested that we change the wording in paragraph (i)(2) the proposed AD to ''Accomplishing the follow(hyphen)on inspections required by paragraph (i)(2) of this AD,'' instead of ''Accomplishing the initial inspections . . . '' Boeing stated that paragraph (i) of the proposed AD would mandate the inspections for airplanes with fewer than 28,300 total flight cycles, where compliance (tables 4, 7, and 8 of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013) consists of initial inspections and then follow-on inspections that contain options. Boeing explained that paragraph (i)(1) of the proposed AD would mandate the initial inspections, and paragraph (i)(2) of the proposed AD would mandate the follow-on inspections. Boeing also explained that paragraph (i)(2) of the proposed AD phrase ''accomplishing the initial inspections'' is understood to refer to the first follow-on inspection directed by the compliance time (threshold). \n\tWe do not agree with the commenter's request. Paragraph (i)(2) of this AD follows the format of Boeing's service bulletin compliance tables, which has a different repeat interval from the inspections specified in paragraph (i)(1) of this AD. Paragraphs (i)(1) and (i)(2) of this AD contain both initial and repetitive inspections as well as related investigative actions. We have not changed this AD in this regard. \n\nRequest To Revise Repetitive Inspection Wording \n\n\n\tBoeing requested that we revise the last sentence of paragraph (i)(2)(ii) of the proposed AD (79 FR 36672, June 30, 2014) to state, ''Repeat the inspections specified in this paragraph thereafter . . . '' Boeing stated that this wording would then match the wording for the repetitive inspections specified in paragraph (i)(2)(i) of the proposed AD. \n\tWe agree with the commenter's request. In this case, similar wording will provide consistent paragraph wording without changing the intent of the NPRM (79 FR 36672, June 30, 2014). We have revised the wording in paragraph (i)(2)(ii) of this AD to ''Repeat the inspections specified in this paragraph thereafter at the applicable time and intervals specified in . . . .'' \n\nRequest To Clarify a Certain Compliance Time \n\n\n\tEurope Airpost requested that, in order to avoid any confusion, we clearly state a compliance time for paragraph (j) of the proposed AD (79 FR 36672, June 30, 2014) for airplanes that have 28,300 total flight cycles or more. The commenter asked whether those airplanes would fall under the condition 28,300 total flight cycles but less than 32,800 total flight cycles, or 32,800 total flight cycles or more. \n\tWe agree that clarification is necessary. In this case, paragraph (j) of this AD states to use the applicable times specified in tables 4, 5, 7, and 8, of paragraph 1.E., ''Compliance,'' of Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. Individual airplanes within an operator's fleet could fall into different categories and thus have different compliance times. Operators are to use the appropriate compliance times and repetitive intervals based upon the applicable number of total flight cycles that have been accumulated on each airplane as of the effective date of this AD. We have added new paragraph (n)(3) of the AD to inform operators that the ''Condition'' columns of the compliance tables also contain compliance information that corresponds to the effective date of the AD. We have also revised paragraphs (i)(1) and (j)(1) of this AD to refer to paragraph (n)(3) of this AD. \n\nRequest To Clarify Terminating Action Wording \n\n\n\tSWA requested that we revise the terminating action portion of paragraph (j) of the proposed AD (79 FR 36672, June 30, 2014) to clarify the specified actions. SWA stated that, as written, the terminating action statement seems to imply that the operator is required to accomplish both the preventive modification of the frame at station 360 and the repair of the frame at station 328 to terminate the repetitive inspection requirements for any of the station 328, 344, and 360 frames. SWA also stated that the terminating action in paragraph (j) of the proposed AD does not specify actions or terminating actions if a repair is installed at the station 344 frame. SWA explained that Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, contains terminating action in the footnotes of the compliance tables in paragraph 1.E., ''Compliance,'' which the commenter thinks should be restated in the AD. \n\tWe agree with the commenter's request. For clarity, we have moved the terminating action provisions that were specified in paragraphs (i)(1), (i)(2), (j), and (k) of the proposed AD (79 FR 36672, June 30, 2014) to new paragraphs (m)(1) through (m)(4) of this AD. We have redesignated subsequent paragraphs accordingly. \n\nRequests To Specify Eddy Current Inspection \n\n\n\tEurope Airpost requested that we clarify whether we meant to exclude the eddy current inspection at station 328 described in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, in paragraph (k) of the proposed AD (79 FR 36672, June 30, 2014). Boeing requested that we add the eddy current inspection at station 328 described in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, in paragraph (k) of the proposed AD. \n\tWe agree with Boeing's request to specify the eddy current inspection and Europe Airpost's request to clarify the eddy current inspection requirement. We inadvertently omitted the eddy current inspection from paragraph (k) of the proposed AD (79 FR 36672, June 30, 2014) which applies to Group 7 airplanes. Our intention was to match the actions described in Boeing Alert Service Bulletin 737-53A1323, dated December6, 2013. In the NPRM (79 FR 36672, June 30, 2014), we did not identify any differences with Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, in regards to the required inspections, which includes repetitive eddy current inspections at station 328. For Groups 2 through 7 airplanes, paragraphs (i) and (j) of the proposed AD do specify detailed and HFEC inspections for Groups 2 through 6 airplanes. Therefore, we have revised paragraph (k) of this AD to specify doing eddy current inspections, in addition to the detailed inspections, of the frame at station 328 for Group 7 airplanes. \n\nRequest To Specify Terminating Actions for Station 380 \n\n\n\tSWA requested that we specify procedures or terminating actions for repairs installed at the station 380 frame, since paragraph (l) of the proposed AD (79 FR 36672, June 30, 2014) does not specify such actions. \n\n((Page 73952)) \n\n\n\tWe do not agree with the commenter's request. Boeing has not provided such repairs for our approval in Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013. Therefore, we have no specific engineering data to review and approve. We have not changed this AD in this regard. \n\nRequest for Credit for Certain Repairs \n\n\n\tSWA requested that we revise paragraphs (i) through (l) of the proposed AD (79 FR 36672, June 30, 2014) to include provisions for existing repairs that were done using the service repair manual (SRM) or the original equipment manufacturer (OEM) instructions. SWA requested that the NPRM be revised to either terminate the inspections or include alternative actions if existing repairs inhibit the ability to perform the inspections. \n\tWe partially agree with the commenter's request. We agree that repairs approved by Boeing via FAA Form 8100-9 (Statement of Compliance with Airworthiness Standards) would have also included the appropriate inspections. We disagree that SRM repairs would necessarily provide the same level of safety. The commenter did notspecify for which SRM repairs it was requesting approval. Such repairs might or might not have included consideration of the safety issues addressed by Boeing Alert Service Bulletin 737-53A1323, dated December 6, 2013, and this AD (e.g., skin cracking combined with frame cracking). We have added a new paragraph (p) to this AD to provide credit for repairs of the station 328, 344, 360, and 380 frames in the areas addressed by this AD that have been approved by the Boeing ODA via FAA Form 8100-9 prior to the effective date of this AD for the repairs specified in paragraphs (i), (j), (k), and (l) of this AD. We have redesignated subsequent paragraphs accordingly. \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 proposedin the NPRM (79 FR 36672, June 30, 2014) for correcting the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM (79 FR 36672, June 30, 2014). \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 737-53A1323, dated December 6, 2013. The service information describes procedures for inspection for cracking and missing straps, modification, and repair of certain fuselage frames. 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 of this AD. \n\nCosts of Compliance \n\n\n\tWe estimate that this AD affects 417 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.................... 21 work-hours x $85 per $0 $1,785 per $744,345 per \n\thour = $1,785 per inspection cycle. inspection \n\tinspection cycle. cycle. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tWe have received no definitive data that would enable us to provide cost estimates for certain on-condition actions specified in this AD. However, we estimate the following costs to do any necessary repairs of the station 328 frame and the station 360 frame. We have no way of determiningthe number of aircraft that might need these repairs: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Frame 328 repair...................... 25 work-hours x $85 per hour = Negligible.............. $2,125 \n\t$2,125. Frame 360 repair...................... 5 work-hours x $85 per hour = Negligible.............. 425 \n\t$425. ---------------------------------------------------------------------------------------------------------------- \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. SubtitleVII: 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\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\n((Page 73953)) \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.