Discussion \n\n\tWe issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to certain Boeing Model 747 Airplanes. That NPRM was published in the Federal Register on April 1, 2009 (74 FR 14750). That NPRM proposed to require replacing the inboard trailing edge (TE) flap transmission carbon disk no-back brakes with skewed roller no-back brakes at the TE flap transmission, positions 4 and 5. \n\nComments \n\n\tWe gave the public the opportunity to participate in developing this AD. We considered the comments received from the three commenters. \n\nSupport for the NPRM \n\n\tBoeing concurs with the contents of the NPRM. \n\nClarification of Criteria for AD \n\n\tLufthansa has doubts that all criteria for the issuance of an AD are met. The commenter states that there is no comprehensible technical background. \n\tWe infer that the commenter is requesting that we withdraw the NPRM. We disagree. Although Boeing Special Attention Service Bulletin 747-27-2422, dated October 30, 2008, states that "since 1999, four operators have reported that the inboard TE flaps blew back due to the failure of a transmission carbon disk no-back brake,'' there have been ten reports of failed inboard and outboard carbon disk no-back brakes since 1973, and six reports since 1999. Nine of the reports were for the inboard no-back, and one for an outboard no-back. All of the failures (i.e., uncommanded blowbacks) occurred at a sufficient altitude for the pilots to react and control the airplane. As a result of these events, Boeing conducted extensive lab tests to check the wear properties and friction characteristics of new and used carbon disk brakes. The tests revealed a wide variation in friction capability but no wear correlation between friction coefficient and the number of cycles. Therefore, the carbon brake may be ineffective regardless of wear. Because of the test results and the number ofevents that have occurred in the fleet, we find it was necessary to proceed with issuing this AD to ensure the safety of the fleet. \n\nRequest to Include an Optional Method of Compliance \n\n\tLufthansa requests that we include a repetitive D-Check shop overhaul (with updated procedures, if necessary) as an optional method of compliance to the proposed modification. Lufthansa states that no- back brakes are removed every 6 years during D-Check and are overhauled in accordance with the latest Boeing overhaul manuals. Lufthansa states that since 1995 there have been no failures of the brake system, or a flap blow back event (which Lufthansa states is extremely improbable due to the fact that a simultaneous double failure has to exist). With the above-mentioned overhaul and an additional maintenance task, Lufthansa states that it is reducing if not even excluding the risk of a double failure. Lufthansa requests a compliance time of 8 years for the first D-check, 8 years for the second D-check, and 6 years for subsequent D-checks. \n\tWe do not agree with the commenter's request to include an optional method of compliance. Based on the results of Boeing's extensive testing of carbon disk brakes, the carbon brakes may be ineffective regardless of wear. Therefore, overhauling the carbon brakes at D-check intervals would not adequately address the unsafe condition. In addition, we do not consider that the brake system failure--which involves a latent failure of the no-back brake, combined with an active failure of the flap drive system--is extremely improbable. No change to this AD is necessary. \n\nRequest to Delay Issuing Final Rule \n\n\tJapan Airlines (JAL) requests that we issue the AD after Revision 1 of Boeing Service Bulletin 747-27-2422 is available. The NPRM cited Boeing Special Attention Service Bulletin 747-27-2422, dated October 30, 2008, as the appropriate source of service information for installing the skewed roller no-back brakes at the trailing edge flap transmission. JAL requests that Boeing amend Service Bulletin 747-27- 2422 to improve Figure 3 to show part numbers and the assembly sequence. JAL adds that Boeing is considering issuing Revision 1. \n\tWe agree that adding part numbers and the assembly sequence to Figure 3 in Boeing Service Bulletin 747-27-2422, dated October 30, 2008, may be beneficial. However, we do not consider that delaying the final rule until after the release of a future service bulletin revision is warranted. Boeing Service Bulletin 747-27-2422, dated October 30, 2008, already includes sufficient information to install the skewed roller no-back brakes at the trailing edge flap transmission within the compliance time. However, paragraph (h) of the final rule provides operators the opportunity to request an AMOC or an extension of the compliance time if data are presented to justify such an extension. \n\nConclusion \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. \n\nCosts of Compliance \n\n\tWe estimate that this AD would affect 249 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this AD. \n\n\tTable--Estimated Costs\n\n\nAction\nWork hours\nAverage labor rate per hour\nParts\nCost\nNumber of U.S.-registered airplanes\nFleet cost\nReplacement \n25\n$80\n$60,670\n$62,670\n249\n$15,604,830\n\nAuthority for this Rulemaking \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 aircraftin 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\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), and \n\t(3) 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\tYou can find our regulatory evaluation and the estimated costs of compliance in the AD Docket. \n\nList of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\nAccordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: \n\nPART 39--AIRWORTHINESS DIRECTIVES \n\n1. The authority citation for part 39 continues to read as follows: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\nSec. 39.13 (Amended) \n\n2. The FAA amends Sec. 39.13 by adding the following new AD: