A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to all Boeing Model 747 series airplanes was published in the Federal Register on May 7, 2004 (69 FR 25519). That notice of proposed rulemaking (NPRM) proposed to require repetitive inspections for cracking of the top and side panel webs and panel stiffeners of the nose wheel well (NWW), and corrective actions if necessary. \n\nExplanation of New Service Information \n\n\tSince the issuance of the NPRM, Boeing has issued and we have reviewed Revision 2 of Boeing Alert Service Bulletin 747-53A2465, dated November 11, 2004 (the NPRM referred to Revision 1 of the service bulletin as the appropriate source of service information for accomplishing the proposed actions). Revision 2 of the service bulletin describes procedures for performing repetitive external detailed inspections for cracking of the top and side panel webs of the NWW (specified as Area 1 and Area 2 in the service bulletin), as applicable; performing repetitive internal detailed and surface high frequency eddy current (HFEC) inspections for cracking of the top and side panel stiffeners of the NWW (specified as Area 3 in the service bulletin); replacing cracked stiffeners with new stiffeners; and repairing any cracked panel web. \n\n\tWe have revised the final rule by adding new paragraph (a)(2) as an option to accomplishing the repetitive inspections required by paragraph (a)(1) (specified as paragraph (a) of the NPRM). The option allows operators to do the repetitive inspections specified in Revision 2 of the service bulletin. The compliance time intervals for the new, optional repetitive inspections are: (1) 1,000 flight cycles for the external detailed inspection, and (2) 6,000 flight cycles for the internal detailed and suface HFEC inspections, which is less stringent than the 1,000 flight-cycle interval for the repetitive inspections required by paragraph (a)(1) of this final rule. \n\n\tWe have also added Revision 2 of the service bulletin to paragraph (b) of the final rule to allow repairs to be done according to either Revision 1 or Revision 2 of the service bulletin, as applicable. \n\n\tAccomplishing the actions specified in either Revision 1 or Revision 2 of the service bulletin at the times specified in the final rule is intended to adequately address the identified unsafe condition. \n\nComments \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\nRequest To Revise or Cancel the NPRM \n\n\tTwo commenters request that the NPRM be revised or cancelled due to the upcoming release of Revision 2 of Boeing Alert Service Bulletin 747-53A2465. One commenter, the airplane manufacturer, notes that Revision 2 of the service bulletin will have different inspections and compliance times than what is specifiedin paragraph (a) of the NPRM. The commenter states that the procedures for ultrasonic inspection will be removed from the service bulletin and that the repetitive interval recommended for the detailed inspection of the NWW sidewall and top webs will be changed. The commenter notes that the detailed inspection will be performed every 1,000 flight cycles, starting at 16,000 total flight cycles, and then, after accumulating 25,000 flight cycles, the detailed inspection will be performed every 100 flight cycles for the web common to the fore-aft stiffeners at water lines (WL) 150, 160 and 170 (left and right sides). The commenter suggests that paragraph (a) of the NPRM be revised to reflect these changes. \n\n\tThe other commenter suggests that the NPRM be revised or cancelled because of the differences between the NPRM and Revision 2 of the service bulletin. The commenter also asks that a new proposal be issued that cites the changes specified in Revision 2 of the service bulletin. \n\n\tWedo not agree with the commenters' requests to revise or cancel the NPRM. Revision 2 of the service bulletin does not contain a 25,000 flight-cycle inspection threshold to reduce the repetitive inspection interval. In addition, as stated earlier, we have revised the final rule by adding the actions specified in Revision 2 of the service bulletin as an option to doing the actions specified in Revision 1 of the service bulletin. \n\nRequest To Extend Inspection Threshold \n\n\tOne commenter requests that the second inspection threshold be extended from 25,000 flight cycles to 28,000 flight cycles for Model 747-400D series airplanes. The commenter states that the fatigue cracks are caused by cabin pressurization and Model 747-400D series airplanes operate with lower cabin differential pressure. \n\n\tWe do not agree with the commenter. We infer that the commenter is referring to Revision 2 of Boeing Alert Service Bulletin 747-53A2465, but as stated earlier, Revision 2 does not contain a second inspection threshold. No change is made to the final rule in this regard. \n\nConclusion \n\n\tAfter careful review of the available data, including the comments noted above, we have determined that air safety and the public interest require adopting the AD with the changes previously described. These changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 1,127 airplanes of the affected design in the worldwide fleet. We estimate that 255 airplanes of U.S. registry will be affected by this AD. \n\n\tIt will take approximately 42 work hours per airplane to accomplish the required inspections specified in Boeing Service Bulletin 747- 53A2465, Revision 1, dated October 16, 2003, and that the average labor rate is $65 per work hour. Based on these figures, the cost impact of the required inspections on U.S. operators is estimated to be $2,730 per airplane, per inspection cycle. \n\n\tIn lieu of the inspections specified in Revision 1 of Boeing Service Bulletin 747-53A2465, it will take approximately 87 or 97 work hours per airplane (depending on the airplane configuration) to accomplish the required inspections specified in Boeing Alert Service Bulletin 747-53A2465, Revision 2, dated November 11, 2004, and that the average labor rate is $65 per work hour. Based on these figures, the cost impact of the required inspections on U.S. operators is estimated to be $5,655 or $6,305 per airplane, per inspection cycle (depending on the airplane configuration). \n\n\tThe cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not includeincidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. \n\nAuthority for This Rulemaking \n\n\tThe FAA's authority to issue rules regarding aviation safety is found in Title 49 of the United States Code. 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\n\tThis rulemaking is promulgated under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, "General requirements." Under that section, the FAA is charged 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 AD.Regulatory Impact \n\n\tThe regulations adopted herein 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. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132. \n\n\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption ADDRESSES. \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, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new airworthiness directive: