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 747-400 series airplanes. The NPRM published in the Federal Register on February 7, 2013 (78 FR 8999). The NPRM was prompted by reports of APU faults due to power feeder cable chafing. The NPRM proposed to require detailed inspections for damage of the APU power feeder cables; replacing the clamps and installing grommets; and related investigative and corrective actions if necessary. We are issuing this AD to detect and correct chafing of the APU power feeder cables within a flammable fluid leakage zone, which, with arcing, could result in fire and structural damage. \n\nRelevant Service Information \n\n\n\tSince we issued the NPRM (78 FR 8999, February 7, 2013), we reviewed Boeing Service Bulletin 747-24A2360, Revision 2, dated October 2, 2013. (The NPRM referenced Boeing Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012, as the appropriate source of service information for accomplishing the required actions.) Boeing Service Bulletin 747-24A2360, Revision 2, dated October 2, 2013, among other things, revises the recommended compliance time from 14 months to 18 months. For information on the procedures and compliance times, see this service information at http://www.regulations.gov by searching for and locating Docket No. FAA-2013-0089. \n\tWe have determined that extending the compliance time, as recommended by the manufacturer, will not adversely affect safety. We have revised the compliance time in paragraph (g) of this AD accordingly. We have also revised paragraphs (c), (g), (h), and (i) of this AD to refer to Boeing Service Bulletin 747-24A2360, Revision 2, dated October 2, 2013. \n\n((Page 15655)) \n\n\n\tIn addition, we have revised paragraph (j) of this final rule to include Boeing Alert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012, for credit forthe actions required by paragraph (g) of this AD, if those actions were performed before the effective date of this AD. \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 8999, February 7, 2013) and the FAA's response to each comment. \n\nRequest To Extend Compliance Time \n\n\n\tKLM Royal Dutch Airlines (KLM) requested that we revise the compliance time of the NPRM (78 FR 8999, February 7, 2013) from 14 months to 36 months. KLM explained that due to the possible operational impact when damage is found, and since the Accomplishment Instructions of Boeing Service Bulletin 747-24A2360, Revision 2, dated October 2, 2013, are performed with electrical power removed, the recommended maintenance check to perform Boeing Service Bulletin 747-24A2360, Revision 2, dated October 2, 2013, is a C-check, and therefore 14 months is not effective. \n\tWe disagree with the request to extend the compliance time to 36 months. Based on a review of the safety aspects and the potential impact to the affected fleet, in conjunction with the latest recommendation from Boeing, as discussed previously, we determined that an extension of the compliance time to 18 months for this final rule is appropriate. \n\nRequest for Clarification of a Possible Process To Prevent Undoing the Actions Required by ADs \n\n\n\tUnited Airlines (UA) requested clarification of a possible process to prevent undoing the actions required by ADs. UA stated that clamp replacement could take place by non-routine maintenance after accomplishment of Boeing Alert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012, and could undo the mandate of the NPRM (78 FR 8999, February 7, 2013). UA asked if there are any means that this AD or future ADs will mandate a process to identify items/areas affected by the AD that may be followed by the industry and original equipment manufacturers (OEMs) so as not to undo theAD. \n\tWe acknowledge that operators must prevent non-routine maintenance from impacting AD requirements. The FAA worked in conjunction with industry, under the Airworthiness Directives Implementation Aviation Rulemaking Committee (ARC), to enhance the AD system. One enhancement involves design approval holder (DAH) recommendations to evaluate the potential for undoing an AD-mandated configuration during all stages of design and development of service bulletins, maintenance documents, or Instructions for Continued Airworthiness (ICA). Refer to Advisory Circular (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). The DAH recommendations in this AC are voluntary. \n\tAlso in response to the AD Implementation ARC, the FAA released AC 39-9, (http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2039-9%20CHG%201.pdf). This AC includes guidance to operators for developing an AD management process that includes information about preventative measures to eliminate and/or mitigate the risk of altering the AD configuration. It is the responsibility of operators to apply necessary controls to maintain the airplane in accordance with the required configuration of an AD. However, given the variety of maintenance and inspection programs of affected operators, we do not believe it is necessary or appropriate to prescribe a particular process to ensure that operators fulfill this responsibility. We have made no changes to this final rule in this regard. \n\nRequest for Clarification of Compliance Time \n\n\n\tVirgin Atlantic Airways (the commenter) requested that we clarify the compliance time of the NPRM (78 FR 8999, February 7, 2013). The commenter explained that the compliance time is not clear because Boeing Alert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012, states a recommended compliance time of 14 months from the date of BoeingAlert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012, but that paragraph (h)(2) of the NPRM states, ''this AD requires compliance within the specified compliance time after the effective date of this AD.'' \n\tBoeing requested that we clarify the compliance time of the NPRM (78 FR 8999, February 7, 2013). Boeing explained that paragraph (h)(2) of the NPRM states: ''Where Boeing Alert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012, specifies a compliance time after the date on the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD.'' Boeing stated that the compliance statement within Boeing Alert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012, states: ''Boeing recommends that the inspection, change and/or repair given in this service bulletin be done within 14 months after the Revision 1 date of this service bulletin.'' \n\tWe agree to clarify the compliance time. The NPRM (78 FR 8999, February 7, 2013) referred to the compliance times specified in Boeing Alert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012, except that where the service bulletin specifies a compliance time after the date on the service bulletin, this AD would require a compliance time within a specified compliance time after the effective date of this AD. In other words, where Boeing Alert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012, specifies a compliance time of ''within 14 months after the Revision 1 date of this service bulletin,'' the NPRM would require a compliance time of ''within 14 months after the effective date of this AD.'' However, as stated previously, we have extended the compliance time and stated it directly in paragraph (g) of this AD. \n\nRequest To Revise Parts Installation Limitation \n\n\n\tBoeing requested that we revise the NPRM (78 FR 8999, February 7, 2013) to either remove the requirement in paragraph (i) of the NPRM, which only allows the use of part number (P/N) TA025097L16 clamps, or that we remove the size suffix (16) from the part number (e.g., P/N TA025097L()). Boeing explained that the variability in wire bundle size due to different wire types/part numbers or wire quantity sometimes requires clamp sizing flexibility. Boeing also expressed that paragraph (i) conflicts with Note 5 of paragraph 3.A., ''GENERAL INFORMATION,'' of Boeing Alert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012. \n\tVirgin Atlantic Airways also requested that we revise paragraph (i) of the NPRM (78 FR 8999, February 7, 2013) to not specify the clamp size. Virgin Atlantic Airways explained that if an operator needs to install a different size clamp, then that would require requesting an alternative method of compliance (AMOC) to comply with this AD. \n\n((Page 15656)) \n\n\n\tWe agree with the request to revise paragraph (i) in this final rule. Paragraph (i) as written in the NPRM (78 FR 8999, February 7, 2013), would not allow theflexibility needed to use a different size clamp of the same basic part number to accommodate wire bundle size differences. We have revised paragraph (i) of this final rule by adding a parenthesis ''()'', which designates different size clamps to accommodate possible wire bundle diameter size differences. We disagree to remove paragraph (i) in this final rule because installation of an improper or unsafe clamp may be detrimental to the safety of the airplane. \n\nRequest for Clarification of Areas Affected by the Parts Installation Limitation \n\n\n\tVirgin Atlantic Airways requested that we clarify paragraph (i) of the NPRM (78 FR 8999, February 7, 2013). Virgin Atlantic Airways explained that the current wording in paragraph (i) of the NPRM can be interpreted as if it applies to the entire aircraft and not just those clamps that are required to be replaced as per Boeing Alert Service Bulletin 747-24A2360, Revision 1, dated May 2, 2012. \n\tWe agree to revise paragraph (i) of this final rule. Paragraph (i), as written in the NPRM (78 FR 8999, February 7, 2013), could be misinterpreted to mean it applies to all areas of the airplane when, in fact, it applies to those areas of the airplane identified in Boeing Service Bulletin 747-24A2360, Revision 2, dated October 2, 2013. We have revised paragraph (i) of this final rule accordingly. \n\nRequest To Delay the NPRM (78 FR 8999, February 7, 2013) \n\n\n\tMr. David Jiang, a private citizen, requested that we delay the NPRM (78 FR 8999, February 7, 2013), until more independent research to assess the cost to Boeing can be performed. Mr. Jiang explained that the estimate in the NPRM is not correct and would like the FAA to disclose how we calculated the cost associated with inspecting and replacing the affected clamps and grommets. Mr. Jiang expressed that if independent third-party entities determine that the financial costs of these minor repairs outweigh other concerns, perhaps this AD will be scrapped entirely, saving Boeing and the public much unnecessary work and expense. \n\tWe disagree to delay this final rule. The estimated costs of the inspections and replacement of the clamps and grommets, which are industry accepted, have been thoroughly assessed by Boeing, and is part of the Boeing service information provided to the operators. The safety merits of this final rule have also been assessed by both Boeing and the FAA, and it was determined that this final rule needs to be released in order to maintain an acceptable level of safety for the affected airplanes. We have made no changes to this 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\t(Agr)re consistent with the intent that was proposed in the NPRM (78 FR 8999, February 7, 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 8999, February 7, 2013). \n\tWe also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD. \n\nCosts of Compliance \n\n\n\tWe estimate that this AD affects 55 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 ---------------------------------------------------------------------------------------------------------------- Inspection, and clamp and 6 work-hours x $85 $70............... $580 per $31,900 per \n\tgrommet replacement. per hour = $510 inspection cycle. inspection cycle. \n\tper inspection \n\tcycle. ---------------------------------------------------------------------------------------------------------------- \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\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\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 ofSubjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.