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 McDonnell Douglas airplanes. That NPRM was published in the Federal Register on August 1, 2008 (73 FR 44937). That NPRM proposed to require installing a dam assembly for the container of the fuel boost pump of the center tank located in the right main tank, and doing the related investigative actions, and corrective actions if necessary. \n\nComments \n\n\tWe gave the public the opportunity to participate in developing this AD. We considered the comment received. \n\nRequest for Service Bulletin Validation \n\n\tNorthwest Airlines (NWA) has concerns that Boeing Service Bulletin DC9-28-216, dated March 18, 2008, has not been fully validated on an airplane. NWA states that the referenced service bulletin specifies that the identified change was completed on an airplane having fuselage number 807, before the initial release of the service bulletin. However, although accomplishment of the referenced service bulletin was started on that airplane (for a NWA airplane), it was determined that the fuel line hardware specified in the service bulletin is incorrect, and the actions could not be accomplished. NWA has contacted Boeing regarding the problem, and adds that, as written, the referenced service bulletin cannot be accomplished. NWA recommends that the service bulletin be validated prior to release of the AD. \n\tWe acknowledge the commenter's concern but we do not agree that Boeing Service Bulletin DC9-28-216, dated March 18, 2008, cannot be accomplished. The manufacturer has informed us that the fuel line hardware specified in Boeing Service Bulletin DC9-28-216, dated March 18, 2008, is correct. During validation of the service bulletin on the airplane having fuselage number 807, the identified problem was corrected prior to the release of Boeing Service Bulletin DC9-28-216, dated March 18, 2008. Therefore, we have made no change to the AD in this regard. \n\nConclusion \n\n\tWe reviewed the relevant data, considered the comment 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 affects 413 airplanes of U.S. registry. We also estimate that it will take 3 or 7 work-hours per product, depending on airplane configuration, to comply with this AD. The average labor rate is $80 per work-hour. Required parts will cost $1,142 or $1,697 per product, depending on configuration of the airplane. Based on these figures, we estimate the cost of this AD to the U.S. operators to be $570,766 or $932,141, or $1,382 or $2,257 per product, depending on configuration of the airplane. \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 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\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: