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 777-200, -200LR, -300, and -300ER series airplanes. The NPRM published in the Federal Register on December 23, 2015 (80 FR 79754) (''the NPRM''). The NPRM was prompted by a report indicating that the manufacturer discovered locations where the control components and wiring of the left and right engine fuel spar valves do not have adequate physical separation to meet the redundant system separation requirements. The NPRM proposed to require modifying the wiring, and installing a new relay bracket and new location for the relay on the left and right engine fuel spar valves. The NPRM also proposed to require an inspection to identify the part number of the MOV actuators for the left and right engine fuel spar valves; replacement of specified MOV actuators with new MOV actuators; certain bonding resistance measurements; and applicable corrective actions. We are issuing this AD to prevent loss of control of both the left and right engine fuel spar valves during a single event, such as local wire bundle damage or a wire bundle fire, which could cause both engines to shut down or result in the inability to control an engine fire. \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. Boeing stated that it has reviewed the NPRM and concurs with the contents of the NPRM. \n\nRequest To Reduce the Compliance Time \n\n\n\tOne commenter, Geoffrey Barrance, requested that we reduce the compliance time in paragraph (g) of the proposed AD. Mr. Barrance stated he is concerned that the timescale proposed for implementing the required modification, 60 months after the effective date of the AD, is too long. Mr. Barrance commented that the unsafe condition is a common failure affecting the continued operation of both engines, and therefore is critical to the safe flight and landing of any airplane. \n\tWe disagree with the commenter's request. It is important to note that while the commenter has indicated there is currently a common mode failure affecting the continued operation of both engines, it is more accurate to say that certain airplanes are currently in a configuration that makes them vulnerable to a single event causing a common mode failure. However, there have been no reports of any events causing this condition. This AD is intended to eliminate that condition. \n\tThe compliance time is determined to be appropriate in consideration of the risk and the safety implications, the average utilization rate of the affected fleet, the practical aspects of an orderly modification of the fleet during regular maintenance periods, and the availability of required modification parts. In addition to our own criteria, we have also considered the manufacturer's safety assessment and recommendation for the compliance time. The compliance time accounts for the risk to the fleet, availability of parts, and other factors. Therefore, we have determined that the compliance time is acceptable. We have not changed this AD in this regard. \n\nRequest To Remove the Concurrent Requirements \n\n\n\tAll Nippon Airways (ANA), Japan Airlines (JAL), and United Airlines (UAL) requested that we remove the concurrent requirement for accomplishing Boeing Service Bulletin 777-28A0034, Revision 3, dated September 25, 2015. JAL and ANA stated that there was no relationship between the wiring change and the actuator replacement. ANA, JAL, and UAL commented that Boeing Service Bulletin 777-28A0034, Revision 3, dated September 25, 2015, is already mandated by AD 2013-05-03, Amendment 39-17375 (78 FR 17290, March 21, 2013) (''AD 2013-05-03''), and it addressed MOV actuator part number (P/N) MA20A1001-1; therefore, it should not be a concurrent requirement. ANAalso added that because the MOV actuator has been addressed, paragraphs (i)(2) and (i)(3) of the proposed AD should not be included. \n\tWe partially agree with the commenters. We agree that the actions in Boeing Service Bulletin 777-28A0034, Revision 3, dated September 25, 2015, are the same actions that are required by AD 2013-05-03 in accordance with Boeing Service Bulletin 777-28A0034, Revision 2, dated September 20, 2010, with a compliance date of April 25, 2018. Because of the overlap in compliance times, the action required by AD 2013-05- 03 may not be fully completed by the time the requirements of this AD become effective. To ensure that the actuator change, in accordance with Boeing Service Bulletin 777-28A0034, Revision 3, dated September 25, 2015, is done prior to the wiring change in accordance with Boeing Special Attention Service Bulletin 777-28-0061, Revision 2, dated May 4, 2015, we have required Boeing Service Bulletin 777-28A0034, Revision 3, dated September 25, 2015,as a concurrent requirement in this AD. Without this concurrent requirement, it is possible that this AD could approve certain configurations that are not compliant and safe. The concurrent requirement eliminates this possibility. The requirements of Boeing Service Bulletin 777-28A0034, Revision 3, dated September 25, 2015, and related credit for previous actions, will remain as stated. We have not changed this AD in this regard. \n\nRequest To Use Boeing Information Notice for Completing the Requirements in the AD \n\n\n\tANA requested that we include Boeing Service Bulletin Information Notice 777-28-0061, IN 03, dated November 16, 2015, to this AD to allow the operators to complete the proposed requirements of the NPRM. \n\tWe partially agree with the commenter's request. We cannot include Boeing Service Bulletin Information Notice 777-28-0061, IN 03, dated November 16, 2015, as an \n\n((Page 79386)) \n\nappropriate source of service information in this AD because it is not an FAA-approved document. However, we acknowledge that for certain airplanes, Figure 22, Sheet 9, of Boeing Special Attention Service Bulletin 777-28-0061, Revision 2, dated May 4, 2015, includes an editorial error, which shows incorrect wire routing. Boeing Service Bulletin Information Notice 777-28-0061, IN 03, dated November 16, 2015, allows for a modification of Group 2 airplanes that meets the requirements of the AD without an additional burden to operators. We have included a corrected figure in paragraph (h) of this AD to address this issue. \n\tIn addition, Figure 11, Sheet 1, of Boeing Special Attention Service Bulletin 777-28-0061, Revision 2, dated May 4, 2015, is incorrect in that it shows the cap and stow of an existing wire, W4255- 1002-20, which is terminated at splice SP41201. The correct wire number to be capped and stowed is W6251-1002-20, which is terminated at splice SP41201. We have clarified this information in paragraph (h)(2) of this AD. \n\nRequest To Clarify the Terminating Action \n\n\n\tJAL and UAL requested that we clarify the terminating action specified in the proposed rule. JAL asked that Boeing Service Bulletin 777-28A0034 be used as a terminating action for the requirements of the proposed rule. UAL stated that since AD 2013-05-03 already addressed MOV actuator P/N MA20A2027 and P/N MA30A1001, it contradicts airworthiness limitations (AWL) 28-AWL-MOV, which was mandated in AD 2015-19-01, Amendment 39-18264 (80 FR 55521, dated September 16, 2015) (''AD 2015-19-01''). \n\tWe agree that clarification is necessary. We agree that certain configurations in Boeing Service Bulletin 777-28A0034, Revision 3, dated September 25, 2015, in conjunction with previous airplane configurations, alleviate the need to do the AWL task implemented by AD 2013-05-03 because the configurations are outside the applicability of that AWL. However, we disagree with using Boeing Service Bulletin 777- 28A0034, Revision 3, dated September 25, 2015, as a terminating action because the requirement of AD 2015-19-01 is to implement the airworthiness limitations items (ALI) into an operator's maintenance program, and this must be done regardless of the configuration of the airplane. Further, certain MOV actuator part numbers can be installed that will place an airplane in the applicability of AWL 28-AWL-MOV, thus requiring periodic inspections to ensure safe operation. Each operator has the option to select a configuration best for its circumstances and can evaluate its configurations and determine if AWL 28-AWL-MOV is applicable to their fleet configuration. We have not changed this AD in this regard. \n\nRequest To Review the Design and Certification Process \n\n\n\tGeoffrey Barrance requested that we review the design and certification process that allowed for the unsafe condition to exist, as well as a review of designs in other airplanes with similar unsafe conditions. Mr. Barrance commented that the unsafe condition indicated a failure has occurred in the design and certification process for the airplane type. Mr. Barrance also commented that a review of the airplane design is required to prevent the implementation of common mode fault exposures for redundant systems. \n\tWe acknowledge the commenter's concerns. We continuously evaluate our certification system and procedures and improve them when problems are found. If the FAA is made aware of potential design deficiencies occurring on a certificated product, we conduct an investigation, evaluate the manufacturer's root-cause analysis, and make a determination whether or not an unsafe condition exists. We then take appropriate action to mitigate the unsafe condition and to identify and incorporate certification system process improvements for future designs. Furthermore, the manufacturer performs a cross model evaluation to determine if the condition exists on other models. We agree with the manufacturer's actions in this regard. We have not changed this AD regarding this issue. \n\nConclusion \n\n\n\tWe reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously and minor editorial changes. We have determined that these minor changes: \n\tAre consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM. \n\tWe also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tWe reviewed Boeing Special Attention Service Bulletin 777-28-0061, Revision 2, dated May 4, 2015. The service information describes procedures for modifying the wiring, and installing a new relay bracket and new location for the relay on the left and right engine fuel spar valves. \n\tWe have also reviewed Boeing Service Bulletin 777-28A0034, Revision 3, dated September 25, 2015. The service information describes procedures for an inspection of the MOV actuators of the left and right engine fuel spar valves for (P/N) MA20A1001-1, replacement of MOV actuators, measurement of the electrical resistance of the bond from the adapter plate to the airplane structure, and applicable corrective actions. \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 133 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 ---------------------------------------------------------------------------------------------------------------- Installation and modification... 119 work-hours x Up to $3,780 Up to $13,895 Up to $1,848,035 \n\t$85 per hour = depending on depending on depending on \n\t$10,115. airplane airplane airplane \n\tconfiguration. configuration. configuration. Inspection of MOV actuators 1 work-hour x $85 $0................ $85............... $11,305. \n\t(concurrent requirements). per hour = $85. ---------------------------------------------------------------------------------------------------------------- \n\n\n\n((Page 79387)) \n\n\n\tWe estimate the following costs to do any necessary replacements and bonding resistance measurements that would be required based on the results of the inspection. We have no way of determining the number of aircraft that might need these replacements: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tAction Labor cost Parts cost Cost per product ---------------------------------------------------------------------------------------------------------------- Replacement of MOV actuators for the Up to 105 work-hours x Up to $10,954.......... Up to $19,879. \n\tleft and right engine fuel spar $85 per hour = $8,925. \n\tvalves. Bonding resistance measurements...... 1 work-hour x $85 per $0..................... $85. \n\thour = $85. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tWe have received no definitive data on the costs of the corrective actions for the bonding resistance measurement in this AD. \n\nAuthority for This Rulemaking \n\n\n\tTitle 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describesthe 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\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.