Discussion \n\n\n\tWe issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2004-12-07, Amendment 39-13666 (69 FR 33561, June 16, 2004). AD 2004-12-07 applied to certain The Boeing Company Model 757 series airplanes equipped with Rolls-Royce RB211 engines. The NPRM published in the Federal Register on April 15, 2013 (78 FR 22215). The NPRM was prompted by reports indicating that the actual operational loads applied to the nacelle are higher than the analytical loads that were used during the initial design. The NPRM proposed to retain the requirements of AD 2004-12-07, which required modification of the nacelle strut and wing structure; and for certain airplanes, repetitive detailed inspections of certain aft bulkhead fasteners for loose or missing fasteners, and corrective action if necessary. For certain other airplanes, AD 2004-12-07 required a one-time detailed inspection of the middle gusset of the inboard side load fitting for proper alignment, and realignment if necessary; a one-time eddy current inspection of certain fastener holes for cracking, and repair if necessary; and a detailed inspection of certain fasteners for loose or missing fasteners, and replacement with new fasteners if necessary. The NPRM proposed to specify a maximum compliance time limit to modify the nacelle strut and wing structure. We are issuing this AD to prevent fatigue cracking in primary strut structure and consequent reduced structural integrity of the strut. \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 proposal (78 FR 22215, April 15, 2013) and the FAA's response to each comment. \n\nSupport for the NPRM (78 FR 22215, April 15, 2013) \n\n\n\tBoeing stated that it concurs with the contents of the NPRM (78 FR 22215, April 15, 2013). \n\n((Page 14983)) \n\nClarification of Effect of Winglet Installation \n\n\n\tAviation Partners Boeing stated that accomplishing the supplemental type certificate (STC) ST01518SE does not affect the actions specified in the NPRM (78 FR 22215, April 15, 2013). \n\tWe concur with the commenter. We have redesignated paragraph (c) of the NPRM (78 FR 22215, April 15, 2013) as (c)(1) and added new paragraph (c)(2) to this final rule to state that installation of STC ST01518SE (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/48e13cdfbbc32cf4862576a4005d308b/Body/0.48A!OpenElement&FieldElemFormat=gif) does not affect the ability to accomplish the actions required by this final rule. Therefore, for airplanes on which STC ST01518SE 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 Clarify Concurrent Requirements \n\n\n\tFedEx requested that we clarify the requirements of paragraph (j) of the NPRM (78 FR 22215, April 15, 2013), which specified concurrent actions. FedEx explained that the NPRM requirement and paragraph 1.B., of Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, conflict with the information in paragraph D., of Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011. FedEx stated that paragraph D. of Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, states that Boeing Service Bulletin 757-54- 0003, Revision 1, dated August 30, 1985; and Boeing Service Bulletin 757-54-0028, Revision 1, dated August 25, 1994 (the concurrent actions required by paragraph (j) of the NPRM); no longer need to be accomplished. \n\tWe agree to clarify the concurrent actions. Table I of paragraph D. in Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, is in error. We have added Note 1 to paragraph (j) of this final rule, which states that paragraph D. of Boeing Service Bulletin 757-54- 0035, Revision 6, dated December 2, 2011, incorrectly states that the actions described in Boeing Service Bulletin 757-54-0003, Revision 1, dated August 30, 1985; and Boeing Service Bulletin 757-54-0028, Revision 1, dated August 25, 1994; no longer need to be accomplished. \n\nRequest To Change When Concurrent Actions Are To Be Done \n\n\n\tAmerican Airlines (AAL) requested that we change paragraph (j) (concurrent actions) of the NPRM (78 FR 22215, April 15, 2013), which specifies doing the actions at the same time as paragraph (i) of the NPRM, to specify that the concurrent actions are to be done at the same time as the actions required by paragraph (g) of the NPRM. AAL stated that the pylon modification action is mandated by paragraph (g) of the NPRM, and paragraph (i) of the NPRM mandates only the time at which the modification must be accomplished. \n\tWe do not agree with the commenter's request because, although the requirement for the modification is first specified in paragraph (g) of this final rule, which is a restatement from AD 2004-12-07, Amendment39-13666 (69 FR 33561, June 16, 2004), the new requirement is in paragraph (i) of this final rule. Paragraph (i) of this final rule correctly references paragraph (g) of this final rule. If the concurrent actions specified in paragraph (j) of this final rule are to be accomplished at the same time as paragraph (g) of this final rule, as the commenter suggests, that would make the requirement retroactive, and would potentially put operators out of compliance. We have not changed this final rule in this regard. \n\nRequest for Repair Credit \n\n\n\tAAL requested that we allow credit for repairs specified in paragraph (k) of the NPRM (78 FR 22215, April 15, 2013) that are made ''before the effective date of this AD'' using Boeing Service Bulletin 757-54-0028, dated March 31, 1994; or Boeing Service Bulletin 757-54- 0028, Revision 1, dated August 25, 1994. \n\tWe do not agree with the commenter's request. Paragraph (k)(1) of this final rule requires that cracking be repaired using a method approved by the FAA as specified in paragraph (n) of the final rule. Boeing Service Bulletin 757-54-0028, dated March 31, 1994; and Boeing Service Bulletin 757-54-0028, Revision 1, dated August 25, 1994; do not contain procedures for repairing cracking, and only specify to contact Boeing if cracking is found. We infer that the commenter is requesting credit for any repair done in accordance with procedures provided by Boeing or with the operator's own methods. The commenter has not provided any details about any such repairs, and therefore we cannot give credit for these repairs. However, under the provisions of paragraph (n) of this final rule, repairs may be approved if substantiating data are provided showing that the repair provides an acceptable level of safety. \n\tFor paragraph (k)(2) of this final rule, Boeing Service Bulletin 757-54-0028, Revision 1, dated August 25, 1994, is already specified as the appropriate source of service information for accomplishing repair of the holes. In addition, since Boeing Service Bulletin 757-54-0028, dated March 31, 1994, does not contain procedures for repairing holes, we cannot give credit for Boeing Service Bulletin 757-54-0028, dated March 31, 1994. However, under the provisions of paragraph (n) of this final rule, repairs may be approved if substantiating data are provided showing that the repair provides an acceptable level of safety. We have not changed this final rule in this regard. \n\nRequest To Clarify Inspections \n\n\n\tAAL requested that we not require the paragraph following the compliance table in paragraph l.E., ''Compliance,'' of Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011. AAL stated that the interim inspections specified in the paragraph following the compliance table in paragraph l.E., ''Compliance,'' of Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, are unclear and that, if required, the inspections should be specified in a new (additional) paragraph. \n\tWe agree to clarify. Paragraphs (g) and (i) of this final rule specifically require accomplishment of the modification of the strut as specified in Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, and do not require any interim inspections. Although there are certain inspections specifically required in paragraphs (h) and (j) of this final rule, there are no interim inspections specified in any paragraph of this final rule. Therefore, the interim inspections defined in the paragraph following the table in paragraph l.E., ''Compliance,'' of Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, are not required by this final rule. We have not changed this final rule in this regard. \n\nRequest To Do Work Out of Sequence \n\n\n\tAAL requested that we allow instructions to be worked out of sequence. AAL stated that by requiring operators to adhere to the sequence of steps as organized in the service information, based on the strictest interpretation, it can place an undue burden on operators and drive longer aircraft out-of-service time. AAL asserted that not allowing instructions to be worked out of sequence prevents operators from working on the wing \n\n((Page 14984)) \n\nstructure and the removed pylon structure simultaneously. AAL also stated that without the leeway to work steps out of sequence, if damage is encountered during a particular step, maintenance must wait for a disposition and corrective action for that damage before continuing to the next step. \n\tWe partially agree with the commenter's request. We agree with revising the final rule to allow work to be accomplished on the wing structure and the removed pylon structure simultaneously, and for work to be accomplished on both pylons simultaneously, because no detrimental effect on the airplane results from accomplishing the service information in this way. \n\tWe disagree with allowing all service information steps to be worked out of sequence. This allowancecould be interpreted as allowing service information steps at one pylon, or at one wing location, to be performed out of sequence, which could detrimentally affect the result of the modification. \n\tWe also disagree with stating that opposite sides of the strut can be worked at different rates, as some tasks are necessary to be performed in sequence. For further clarification of strut task sequencing, operators may request approval of an AMOC by providing additional details defining the tasks using the procedures defined in paragraph (n) of this final rule. \n\tWe have added new paragraph (l) to this final rule, which states that although Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, specifies to work the wing modification before the strut modification, this AD allows for the wing and strut modifications to occur simultaneously. This AD also allows for both struts to be modified simultaneously. We have redesignated subsequent paragraphs accordingly. We have also referenced paragraph (l) in paragraphs (g) and (h) of this final rule. \n\nRequest To Require Only Certain Service Information Steps \n\n\n\tAAL requested that we require only the steps in the service information that are critical for safety of flight. AAL suggested that only Part II, Steps 6, 7, and 9-12; Part III, Steps 4-24; Part IV, Steps 3-7; and Part VI, Steps 3-16 and 19; of Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, should be required. AAL stated that preparation and open-up and close-up instructions are not necessary to mandate and can be left to operator discretion on the best methods without affecting the ability to address the safety issue that exists. \n\tWe do not agree with AAL's request. Boeing Service Bulletin 757-54- 0035, Revision 6, dated December 2, 2011, already allows operator's discretion for certain actions. Note 8 of paragraph 3.B.A., ''General Information,'' of Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2,2011, specifies that when the words ''refer to'' are used for a procedure, operators may use an accepted alternative procedure. Note 11 of paragraph 3.B.A., ''General Information,'' of Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, specifies that for access, all the identified parts do not need to be removed if you can get access without removing the identified parts and that additional parts may be removed if needed. \n\tHowever, due to the complexity of the modification to the strut, certain preparation and installation steps are needed to prevent damage to the strut structure, systems components, and the engine. In addition, a fuel leak check is specified in Boeing Service Bulletin 757-54-0035, Revision 6, dated December 2, 2011, to ensure that the modification and reassembly were completed and that no hidden damage exists. Therefore, no changes have been made to this final rule in this regard. \n\tAlthough we have not revised this final rule, we do agree with the concept of minimizing AD requirements when appropriate. The FAA worked in conjunction with industry, under the Airworthiness Directives Implementation Aviation Rulemaking Committee (ARC), to enhance the AD system. One enhancement is a new process for annotating which steps in the service information are ''required for compliance'' (RC) with an AD. Differentiating these steps from other tasks in the service information is expected to improve an owner's/operator's understanding of AD requirements and help provide consistent judgment in AD compliance. In response to the AD Implementation ARC, the FAA released AC 20-176, dated December 19, 2011 (http://rgl.avs.faa.gov/Regulatory-- and--Guidance--Library/rgAdvisoryCircular.nsf/0/ a78cc91a47b192278625796b0075f419/$FILE/AC%2020-176.pdf); and Order 8110.117, dated September 12, 2012 (http://rgl.avs.faa.gov/Regulatory-- and--Guidance--Library/rgOrders.nsf/0/984bb9eb07cdd86986257a7f0070744c/ $FILE/Order%208110.117.pdf), which include the concept of RC. The FAA has begun implementing this concept in ADs when we receive service information containing RC steps. While some design approval holders have implemented the RC concept, the implementation is voluntary. The FAA does not intend to develop or revise AD requirements to incorporate the RC concept if it is not included in the service information. \n\tContrary to AAL's statement that ADs should mandate only those service bulletin provisions that are necessary to ensure safety of flight, ADs generally contain requirements that are reasonably related to addressing the unsafe condition, as determined by the FAA and the design approval holder that developed the service bulletin. Typically, operators' maintenance programs were not developed in recognition of the unsafe condition that is being addressed by an AD. Whenever we issue an AD, those programs had failed to prevent the unsafe condition in the first place. Therefore, many provisions of ADs address aspects of accomplishing the required maintenance that are necessary to prevent operators from inadvertently aggravating the unsafe condition or introducing new unsafe conditions. \n\tFor many years, the Air Transport Association (now Airlines for America, A4A) has sponsored the ''Lead Airline'' program through which individual airlines are provided an opportunity to prototype manufacturers' draft service instructions before they are finalized. One objective of this activity is to minimize the procedures included in the instructions that are considered unnecessary. Therefore, when the FAA receives a manufacturer's service bulletin, we recognize that the procedures specified have been determined to be necessary by both the manufacturer and affected operators. As in this case, the instructions provided in service bulletins referenced in ADs are reasonably related to addressing the unsafe condition. \n\tAs always, if AAL or any other operator prefers to address the unsafe condition by means other than those specified in the referenced service information, they may request approval for an alternative method of compliance using the procedures specified in paragraph (n) of this final rule, and, if approved, may use it instead of the procedures specified in the service information. \n\nRequest To Correct Typographical Error \n\n\n\tAAL requested that we revise paragraph (j)(1) of the NPRM (78 FR 22215, April 15, 2013) to remove the extra word ''dated'' from the service information citation. \n\n((Page 14985)) \n\n\n\tWe agree to correct the typographical error and have removed the extra word ''dated.'' \n\nAdditional Change Made to This Final Rule \n\n\n\tThe information in paragraph (l)(3) of the NPRM (78 FR 22215, April 15, 2013) has been separated into two paragraphs in this final rule (paragraphs (m)(3) and (m)(4) of this final rule). In addition, we changed the reference in paragraph (m)(3) of this final rule to refer to the actions required by paragraph (j)(1) of this final rule. We also changed the reference in paragraph (m)(4) to this final rule to refer to the actions required by paragraph (j)(2) of this final rule. The content has not been changed. \n\tThe information in paragraph (m)(4) of the NPRM (78 FR 22215, April 15, 2013) has been added to new paragraph (n)(4) of this final rule. The content has not been changed. \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 (78 FR 22215, April 15, 2013) for correcting the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM (78 FR 22215, April 15, 2013). \n\tWe also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD.Costs of Compliance \n\n\n\tWe estimate that this AD affects 176 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 -------------------------------------------------------------------------------------------------------------------------------------------------------- Modification............................ Up to 1,188 work-hours x $85 $0 Up to $100,980........... Up to $17,772,480. (retained from AD 2004-12-07, Amendment per hour = $100,980. \n\t39-13666 (69 FR 33561, June 16, 2004)). One-time Inspection (retained from AD 1 work-hour x $85 per hour = 0 $85...................... $14,960. \n\t2004-12-07,Amendment 39-13666 (69 FR $85. \n\t33561, June 16, 2004)). Concurrent modification (new action, 30 142 work-hours x $85 per hour 0 $12,070.................. $362,100. \n\tairplanes). = $12,070. Concurrent inspection and fastener 104 work-hours x $85 per hour 0 $8,840................... $106,080. \n\tinstallation (new action, 12 airplanes). = $8,840. -------------------------------------------------------------------------------------------------------------------------------------------------------- \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.Authority 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\nRegulatory Findings \n\n\n\tWe have determined that this AD will not have federalism implications under Executive Order 13132. ThisAD 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.