Discussion \n\n\n\tWe issued a supplemental notice of proposed rulemaking (SNPRM) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to the specified products. That SNPRM published in the Federal Register on March 5, 2012 (77 FR 13043). The original NPRM (75 FR 27966, May 19, 2010) proposed to require installing aluminum gutter reinforcing brackets to the forward and aft drip shield gutters of the MEC; and adding a reinforcing fiberglass overcoat to the top surface of the MEC drip shield, including an inspection for cracking and holes in the MEC drip shield, and corrective actions if necessary. That NPRM also provided for an option to install an MEC drip shield drain system, which, if accomplished, would extend the compliance time for adding the reinforcing fiberglass overcoat to the top surface of the MEC drip shield. The SNPRM proposed to revise the locating dimensions of the brackets and change the routing of the forwarddrain tubes. \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 (77 FR 13043, March 5, 2012) and the FAA's response to each comment. \n\nConcurrence With Supplemental NPRM (77 FR 13043, March 5, 2012) \n\n\n\tBoeing concurs with the contents of the proposed rule (77 FR 13043, March 5, 2012). \n\nRequest To Extend Compliance Time \n\n\n\tUnited Airlines (UAL) requested an extension of the compliance time from 24 months to 48 months to accomplish the actions in paragraph (g)(1) of the supplemental NPRM (77 FR 13043, \n\n((Page 46944)) \n\nMarch 5, 2012). UAL stated that based on parts availability and its normal maintenance schedule, a 48-month compliance time would save costs and would allow time for the operators to perform the terminating action without having to perform the interim action, which would permanently add 26 lbs. to the airplane. \n\tWe do not agree with the commenter's request to extend the compliance time. In developing an appropriate compliance time for this action, we considered the safety implications, parts availability, and normal maintenance schedules for the timely accomplishment of the modification. In consideration of these items, as well as the reports of multi-power system loss affecting flight-critical systems of an airplane in flight, we have determined that a 24-month compliance time will ensure an acceptable level of safety and allow the modifications to be done during scheduled maintenance intervals for most affected operators. The interim action is provided to give operators additional time to perform the more time-consuming action of accessing the necessary locations to perform the terminating action. We have not changed the AD in this regard. \n\nRequest To Reduce Compliance Time \n\n\n\tCara Leigh Bitton (Weber State University) concurred with the actions proposed by the supplemental NPRM (77 FR 13043, March 5, 2012), but questionedwhy the compliance time would need to be extended for adding the reinforcing fiberglass overcoat to the top surface of the MEC drip shield, as required by paragraph (g)(2)(ii) of the supplemental NPRM. The commenter noted the risk and the importance to the passengers and crew of these airplanes. The commenter contended these changes should be made as soon as possible. \n\tWe infer the commenter is requesting we reduce the compliance time in paragraph (g)(2)(ii) of this AD. We disagree with the commenter's request. In developing an appropriate compliance time for adding the reinforcing fiberglass overcoat to the top surface of the MEC drip shield, we considered the safety implications, parts availability, and normal maintenance schedules for timely accomplishment of replacement of the fasteners. Further, we arrived at the compliance time with operator and manufacturer concurrence. \n\tIn consideration of these factors, we determined that the compliance time, as proposed and retained in this final rule, represents an appropriate interval in which operators can install the modification in a timely manner within the fleet, while still maintaining an adequate level of safety. Operators are always permitted to accomplish the requirements of an AD at a time earlier than the specified compliance time; therefore, an operator may choose to add the reinforcing fiberglass overcoat before the specified compliance time of 96 months after the effective date of this AD. \n\tIn addition, the purpose of two different compliance times is to provide a more immediate solution to the safety risk of cracked MEC drip shields by installing aluminum reinforcing brackets (i.e., an interim corrective action that specifies installing drains for the water to travel away from the MEC drip shield), and adding a reinforcing fiberglass overcoat to the top surface of the MEC drip shield (i.e., the long-term corrective action). Reducing the compliance time for the terminating action is not necessary based on the safety risk for affected operators of Model 747-400 and 747-400D airplanes. If additional data are presented that would justify a shorter compliance time, we may consider further rulemaking on this issue. However, we have not changed the AD in this regard. \n\nRequest To Correct Discrepancies \n\n\n\tAn email thread between ST Aerospace and The Boeing Company was forwarded to the FAA by The Boeing Company as an ex parte request that we reference a pending service bulletin revision planned by The Boeing Company. The pending service bulletin will address discrepant quantities of nut plates and types of fasteners called out in Boeing Alert Service Bulletin 747-25A3555, Revision 1, dated July 27, 2011, which affects certain airplanes operated by ST Aerospace. \n\tWe disagree that a change to the AD is needed, because the ST Aerospace configuration affects a very small number of the airplanes listed in Boeing Alert Service Bulletin 747-25A3555, Revision 1, dated July 27, 2011. Furthermore, doing the actions specified in Boeing Alert Service Bulletin 747-25A3555, Revision 1, dated July 27, 2011, addresses the identified unsafe condition. Operators are allowed to use different types of fasteners, as specified in Note 7. of paragraph 3.A., ''Accomplishment Instructions,'' of Boeing Alert Service Bulletin 747-25A3555, Revision 1, dated July 27, 2011. However, if an operator has a different airplane configuration that might use a different quantity of nut plates than what is specified in Boeing Alert Service Bulletin 747-25A3555, Revision 1, dated July 27, 2011, they may request an alternative method of compliance (AMOC) in accordance with paragraph (i) of the final rule. In addition, if a later revision of the referenced service bulletin is issued, affected operators may request approval to use a later revision as an AMOC, under the provisions of paragraph (i) of the final rule. We have not changed the AD in this regard. \n\nChanges to the AD \n\n\n\tBoeing has issuedInformation Notice 747-25A3555 IN 04, dated February 10, 2012, to inform operators of airplanes in groups 1, 2 and 3 of incorrect applicability tags specified in Boeing Alert Service Bulletin 747-25A3555, Revision 1, dated July 27, 2011. We have included this corrected information in new paragraph (h) of this AD, and changed the subsequent paragraph identifiers 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 the AD as proposed except for minor editorial changes. We have determined that these minor changes: \n\tAre consistent with the intent that was proposed in the SNPRM (77 FR 13043, March 5, 2012) for correcting the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the SNPRM (77 FR 13043, March 5, 2012). \n\nCosts of Compliance \n\n\n\tWe estimate that this AD affects 71 airplanes of U.S. registry. \n\tWe estimate the following costs to comply with this AD: \n\n((Page 46945)) \n\n\n\n\n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost on U.S. \n\tAction Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Install brackets............... 19 work-hours x Up to $2,408 \1\. Up to $4,023 \1\. Up to $285,633.\1\ \n\t$85 per hour = \n\t$1,615. Add overcoat................... 63 work hours x $1,731 ($577 x 3) $7,086........... $503,106. \n\t$85 per hour = \n\t$5,355. Install optional MEC drip 22 work hours x Up to $8,982 \1\. Up to $10,852 \1\ Up to $770,492.\1\ \n\tshield drain system. $85 per hour = \n\t$1,870. ---------------------------------------------------------------------------------------------------------------- \1\ Dependingon work package. \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 ADwill 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.