Examining the Docket \n\n\n\tYou may examine the airworthiness directive (AD) docket on the Internet at http://dms.dot.gov or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is located on the plaza level of the Nassif Building at the street address stated in the ADDRESSES section. \n\nDiscussion \n\n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to all McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 series airplanes. That NPRM was published in the Federal Register on April 11, 2006 (71 FR 18249). That NPRM proposed to require replacing the clamp bases for the fuel vent pipe with improved clamp bases. \n\nNew Relevant Service Information \n\n\n\tSince we issued the NPRM, Boeing has issued Service Bulletin DC9- 28-211, Revision 1, dated June 21, 2006. (The NPRM referred to the original issue of that service bulletin, dated February 23, 2005, as the appropriate source of service information for the replacement of the clamp bases.) The instructions in Revision 1 are essentially the same as those in the original issue of the service bulletin. Among other things, Revision 1 of the service bulletin reduces the recommended compliance time from 10 years to 5 years, and revises the cost of parts. The NPRM specified a compliance time of 60 months, so no change to the compliance time in this AD is needed. We have, however, revised the Costs of Compliance section of this AD to reflect the increased parts cost. We have also added a new paragraph (g) to give credit for actions accomplished before the effective date of this AD in accordance with the original issue of the service bulletin, and re-identified subsequent paragraphs accordingly. \n\nComments \n\n\n\tWe provided the public the opportunity to participate in the development of this AD. We have considered the comments received. \n\nRequest To Extend Compliance Time \n\n\n\tThe Air Transport Association, on behalf of its member Northwest Airlines (NWA), agrees with the intent of the NPRM. However, NWA notes that the proposed 60-month compliance time is significantly less than the 10-year compliance time recommended in the original issue of Boeing Service Bulletin DC9-28-211. NWA states that its current maintenance program necessitates gaining access to the outboard fuel tanks every 9 years. NWA notes that the 60-month compliance time would necessitate additional work hours and more out-of-service time. \n\tWe infer that NWA is requesting that we extend the compliance time to agree with the original issue of the Boeing service bulletin. We do not agree that any change is necessary. In developing an appropriate compliance time for this AD, we considered not only the manufacturer's recommendation, but also the degree of urgency associated with the subject unsafe condition and the average utilization of the affected fleet. In light of all of these factors, we have determined that a 60- month compliance time represents an appropriate interval of time for affected airplanes to continue to operate without compromising safety. Further, we note that the 60-month compliance time is consistent with the recommended 5-year compliance time specified in Revision 1 of Boeing Service Bulletin DC9-28-211. We have not changed the AD in this regard. \n\nRequest To Revise Costs of Compliance \n\n\n\tBoeing comments that the service bulletin estimates that it will take 8 work hours to do the actions therein, but the NPRM estimates 4 work hours are needed to do the proposed actions. \n\tWe infer that Boeing is requesting that we revise the Costs of Compliance section to reflect the 8-work-hour estimate in the service bulletin. We do not agree. The cost information below describes only the direct costs of the specific actions required by this AD. The estimate of 4 work hours represents the time necessary to perform only the actions actually required by this AD. 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. We recognize that, in doing the actions required by an AD, operators may incur incidental costs in addition to the direct costs. Those incidental costs, which may vary significantly among operators, are almost impossible to calculate. We have not changed the AD in this regard. \n\nConclusion \n\n\n\tWe have carefully reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We have determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCosts of Compliance \n\n\n\tThere are about 640 airplanes of the affected design in the worldwide fleet. This AD affects about 413 airplanes of U.S. registry. The required actions will take up to 4 work hours per airplane, at an average labor rate of $80 per work hour. Required parts will cost between $1,034 and $2,068 per airplane. Based on these figures, the estimated cost of this AD for U.S. operators is between $559,202 and $986,244, or $1,354 and $2,388 per airplane. \n\nAuthority for This Rulemaking \n\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\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\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 numberof small entities under the criteria of the Regulatory Flexibility Act. \n\tWe prepared a regulatory evaluation of the estimated costs to comply with this AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \nAdoption of the Amendment \n\n0 Accordingly, 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 Federal Aviation Administration (FAA) amends Sec. 39.13 by adding the following new airworthiness directive (AD):