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 Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. That NPRM was published in the Federal Register on October 17, 2007 (72 FR 58773). That NPRM proposed to require replacing the drain tube assemblies and support clamps on the aft fairings of the engine struts. \n\nComments \n\n\tWe gave the public the opportunity to participate in developing this AD. We considered the comments received from the two commenters. \n\nSupport for the NPRM \n\n\tBoeing supports the NPRM. \n\nRequest for Revision of Compliance Time \n\n\tThe Air Transport Association (ATA), on behalf of a member, American Airlines, requests that the compliance time specified in paragraph (f) of the NPRM be revised from 60 to 72 months. The ATA states that the operators' routine maintenance schedules may not allow for accomplishment of the proposed replacement on affected aircraft within the proposed compliance time, and thus operators would incur additional costs associated with special scheduling. \n\tWe do not agree with the commenter's request to extend the compliance time. In developing an appropriate compliance time for this action, we considered the urgency associated with the subject unsafe condition, the availability of required parts, and the practical aspect of accomplishing the required replacement within a period of time that corresponds to the normal scheduled maintenance for most affected operators. However, according to the provisions of paragraph (g) of the final rule, we may approve requests to adjust the compliance time if the request includes data that prove that the new compliance time would provide an acceptable level of safety. \n\nRequest To Change the Work Hours of the "Costs of Compliance'' Section \n\n\tThe ATA also requests that the work hours specified in the "Costs of Compliance'' section of the NPRM be changed from 4 to 10.5 work hours. The ATA states that Boeing Special Attention Service Bulletin 737-54-1043, dated May 2, 2007 (referred to as the appropriate source of service information for accomplishing the proposed actions in the NPRM), includes 7 work hours for open and close access. The ATA states that such a change will provide a better representation of the time included in the service bulletin. \n\tWe do not agree with the ATA's request to increase the work hours specified in the "Costs of Compliance'' section of the NPRM. That section describes only the direct costs of the specific actions required by this AD. Based on the best data available, the manufacturer provided the number of work hours (four) necessary to do the required actions. This number represents the time necessary to perform only the actions actually required by this AD. We recognize that, in doing the actions required by an AD, operators might 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, time necessary for planning, or time necessitated by other administrative actions. Those incidental costs, which might vary significantly among operators, are almost impossible to calculate. Therefore, we have made no change to the AD in this regard. \n\nClarification of Replacement \n\n\tFor clarification purposes, we have revised paragraph (f) from: "Within 60 months after the effective date of this AD, remove the drain tube assemblies and support clamps on the aft fairing of the struts of engine number 1 and engine number 2. These are to be replaced with new drain tube assemblies and clamps * * *'' to: "Within 60 months after the effective date of this AD, replace the drain tube assemblies and support clamps on the aft fairing of the struts of engine number 1 and engine number 2 with new drain tube assemblies and clamps * * *'' to provide consistency of terminology. \n\nConclusion \n\n\tWe reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting the AD with the change described previously. We also determined that this change will not increase the economic burden on any operator or increase the scope of the AD. \n\nCosts of Compliance \n\n\tThere are about 2,058 airplanes of the affected design in the worldwide fleet. This AD affects about 721 airplanes of U.S. registry. The actions take about 4 work hours per airplane, at an average labor rate of $80 per work hour. Required parts cost about $2,351 per airplane. Based on these figures, the estimated cost of this AD for U.S. operators is $1,925,791, or $2,671 per 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 \nthe 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\tForthe 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: