The FAA proposed to amend 14 CFR part 39 with an AD for certain Boeing Model 747-100B SUD, -200B, -300, -400, and -400D series airplanes. That action, published in the Federal Register on September 28, 2004 (69 FR 57884), proposed to require repetitive inspections for cracking in fuselage stringers 8L, 8R, 10L, and 10R at body stations 460, 480, and 500 frame locations; and repair if necessary. \n\nComments \n\n\tWe provided the public the opportunity to participate in the development of this AD. We have considered the comments that have been submitted on the proposed AD. \n\nSupport for the Proposed AD \n\n\tOne commenter concurs with the FAA's compliance recommendations specified in the proposed AD. A second commenter, the manufacturer, requested that the compliance time be changed to match the referenced service bulletin; the commenter later submitted a comment stating that it reanalyzed the data and now concurs with the compliance time specified in the proposed AD. \n\nRequest for Clarification of the Compliance Time \n\n\tOne commenter states that paragraph (f) of the proposed AD specifies repeating the inspection at intervals not to exceed 3,000 flight cycles until the optional terminating action is accomplished. The commenter adds that the referenced service bulletin recommends inspections at specific thresholds that equate to a 3,000-flight-cycle interval, until the airplane accumulates 25,000 flight cycles. The commenter also notes that the referenced service bulletin recommends that airplanes having more than 25,000 total flight cycles be inspected at intervals not to exceed 2,000 flight cycles, and adds that the proposed AD does not seem to address this situation. The commenter asks that the preamble in the proposed AD clearly specify that the 3,000- flight-cycle interval cited in paragraph (f) replaces the threshold values in the referenced service bulletin. \n\n\tAlthough we acknowledge the commenter's concern, the difference in compliance times was explained in the proposed AD. In the section titled "Differences Between the Proposed AD and Service Information" of the preamble of the proposed AD, we define the difference in compliance times, as follows: "The manufacturer reanalyzed the service problem and has advised the FAA that the reanalysis has resulted in threshold and repetitive inspection intervals different from the service bulletin. This resulted in simplified initial thresholds and an increased number of flight cycles between repetitive inspections." That section of the preamble of the proposed AD is not restated in the final rule; therefore, we made no change to the final rule in this regard. \n\nRequest for Optional Open-Hole and Surface High Frequency Eddy Current (HFEC) Inspections To Extend Repetitive Inspection Intervals \n\n\tOne commenter states that, subsequent to the release of the referenced service bulletin, Boeing advised the commenter of optional open-hole and surface HFEC inspections that could be performed in addition to the specified detailed inspections. The commenter adds that these optional inspections would allow extending the repetitive inspection interval to 4,000 flight cycles, until the accumulation of 25,000 total flight cycles on the airplane. The commenter asks that the FAA consult with Boeing about this alternative inspection process and, if appropriate, include that option in the final rule. \n\tAlthough we acknowledge that the optional inspections may be a viable alternative to the detailed inspections, we have confirmed with the manufacturer that while an open-hole and surface HFEC inspection may be accomplished, there are no existing procedures available. Therefore, we do not agree to add the optional inspections and extend the repetitive inspection interval in this final rule. Paragraph (i) of this AD provides affected operators the opportunity to apply for an alternative method of compliance (AMOC) and to present data to justify adding the optionalinspections and extending the repetitive inspection interval. In addition, if the referenced service information is revised to add the optional inspections, we may approve it as an AMOC to the final rule, if appropriate. We have made no change to the final rule in this regard. \n\nRequest To Change Costs of Compliance Section \n\n\tOne commenter states that the proposed AD cites 3 work hours for accomplishing the inspection, and uses this estimate to determine the cost of compliance. The commenter notes that although 3 hours to accomplish the inspection is valid, no consideration is given for access and restoration, which can require up to 61 work hours for each airplane per the referenced service information. The commenter adds that it is inappropriate and unrealistic to cite a cost of compliance that fails to account for access and restoration when such tasks do not occur frequently enough to warrant them as negligible. The commenter asks that the cost of compliance be recalculated toinclude the work hours for access and restoration. \n\n\tWe do not agree to change the work hours in this AD. This number represents the time necessary to perform only the action actually required by the AD. The action in this final rule reflects only the direct costs of the specific required action (inspection) based on the best data available from the manufacturer. The cost analysis in AD rulemaking actions typically does not include incidental costs such as the time required to gain access and close up, time necessary for planning, or time necessitated by other administrative actions. Those incidental costs, which may vary significantly among operators, are almost impossible to calculate. We have made no change to the final rule in this regard. \n\nConclusion \n\n\tWe have carefully reviewed the available data, including the comments that have been submitted, and determined that air safety and the public interest require adopting the AD as proposed. \n\nCosts of Compliance \n\n\tThisAD will affect about 243 Boeing Model 747-100B SUD, -200B, - 300, -400, and -400D series airplanes worldwide. The following table provides the estimated costs for U.S. operators to comply with this AD. \n\n\tEstimated Costs\n\n\nAction\nWork hours\nAverage labor rate per hour\nParts\nCost per airplane\nNumber of U.S.-registered airplanes\nFleet cost\nInspection \n3 \n$65 \nNone \n$195 \n69 \n$13,455 \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\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\tWe have determined that this 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\n\tFor the reasons discussed above, I certify that this AD: \n\n\t(1) Is not a "significant regulatory action" under Executive Order 12866; \n\n\t(2) Is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and \n\n\t(3) Will not have a significant economic impact, positive or negative, on a substantial number of small entitiesunder the criteria of the Regulatory Flexibility Act. \n\n\tWe prepared a regulatory evaluation of the estimated costs to comply with this AD. See the ADDRESSES section for a location to examine the regulatory evaluation. \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 airworthiness directive (AD):