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 certain Boeing Model 737-600, - 700, -700C, -800, and -900 series airplanes was published in the Federal Register on August 20, 2002 (67 FR 53893). That action proposed to require replacement of the existing fueling float switch and conduit assemblies in the main and center fuel tanks with new, improved assemblies. \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 Add Revised Service Information \n\n\tOne commenter, the manufacturer, asks that Boeing Alert Service Bulletin 737-28A1142, Revision 2, dated November 26, 2002, be added to the proposed AD as another source of service information for accomplishment of the specified actions. Boeing Alert Service Bulletin 737-28A1142,dated February 7, 2002, was referenced in the proposed AD as the appropriate source of service information for accomplishment of the actions. \n\n\tThe FAA agrees with the commenter. We have reviewed and approved Boeing Alert Service Bulletin 737-28A1142, Revision 2, dated November 26, 2002. \n\n\tWe find that the changes incorporated in Revision 2 of the service bulletin are not substantive, meaning that airplanes modified per the original issue of the service bulletin are not subject to any additional work under Revision 2 of the service bulletin. Therefore, we have revised paragraph (a) of this final rule to refer to Revision 2 of the service bulletin as the appropriate source of service information for the actions in that paragraph. In addition, we have added a new paragraph (b) to this final rule (and reordered subsequent paragraphs accordingly) to give credit for replacements accomplished before the effective date of this AD according to the original issue of the service bulletin.Request To Change Number of Airplanes Affected \n\n\tThe same commenter asks that the number of affected airplanes that is specified in the Cost Impact section of the proposed AD be changed. The commenter provided supporting data which confirms that the number of airplanes in the worldwide fleet is 927, and the number of U.S.- registered airplanes is 421. \n\n\tWe agree with the commenter, as we inadvertently specified the incorrect numbers of affected airplanes in the proposed AD. We have changed the Cost Impact section in this final rule to reflect the correct numbers of airplanes. \n\nRequest To Change Work Hours \n\n\tOne commenter states that the man hours specified in the Cost Impact section of the proposed AD are conservative, and notes that the actual man hours will be higher and will increase the out-of-service time for its airplanes. \n\n\tAlthough the commenter does not request a change, we infer that the commenter would like the number of work hours specified in the Cost Impact section to be increased. \n\n\tWe do not agree to change the work hours for the replacements. The number of work hours necessary to accomplish the replacements, as specified in the Cost Impact section, is consistent with the service bulletin. The number represents the time necessary to perform only the replacements actually required by this AD. We recognize that, in accomplishing the requirements of any AD, operators may incur "incidental" costs in addition to the "direct" costs. The cost analysis in AD rulemaking actions, however, typically does not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. Because incidental costs may vary significantly from operator to operator, they are almost impossible to calculate. Therefore, no change is made to the final rule in this regard. \n\nExplanation of Change to Final Rule \n\n\tWe have changed the compliance time terminology specified in paragraphs (a)(1), (a)(2), and (a)(3) of the proposed AD from flight cycles to flight hours in the final rule. We inadvertently used the term "flight cycles," in the proposed AD; however, the referenced service bulletin specifies "flight hours," and the proposed AD also should have specified "flight hours." \n\nConclusion \n\n\tAfter careful review of the available data, we have determined that air safety and the public interest require the adoption of the rule with the changes previously described. We have determined that 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 927 airplanes of the affected design in the worldwide fleet. The FAA estimates that 421 airplane of U.S. registry will be affected by this AD.\n\n\tIt will take approximately 56 work hours per airplane to accomplish the replacement in the two main fuel tanks, as specified in Work Page I, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the work hours for this required replacement on U.S. operators is estimated to be $1,414,560, or $3,360 per airplane. \n\n\tIt will take approximately 23 work hours per airplane to accomplish the replacement in the center fuel tank, as specified in Work Package II, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the work hours per this required replacement on U.S. operators is estimated to be $580,980, or $1,380 per airplane. \n\n\tThe kit required to accomplish the replacement in all three fuel tanks will cost approximately $5,116 per airplane. \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 include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. \n\nRegulatory 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\n\tAccordingly, 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\n\t1. The authority citation for part 39 continues to read as follows: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: