Discussion \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 certain Boeing Model 737-300, -400, and -500 series airplanes. That NPRM was published in the Federal Register on August 16, 2007 (72 FR 45972). That NPRM proposed to require, among other actions, modifying the door-mounted escape system of the forward right side door slide compartment. \n\nComments \n\n\tWe provided the public the opportunity to participate in the development of this AD. We have considered the comments received. \n\nSupport for NPRM \n\n\tBoeing and the Air Transport Association (ATA), on behalf of its member Continental, support the NPRM as proposed. \n\nRequest To Allow Replacement of Entire Compartment Assembly \n\n\tThe ATA requests that operators be allowed to replace the entire compartment assembly rather than modifying it in accordance with Boeing Special Attention Service Bulletin 737-25-1567, dated March 21, 2007 (referred to as the appropriate source of service information in the AD for accomplishing the required modification). The ATA has concerns about the availability of the slide compartment parts from Boeing. \n\tWe partially agree with the ATA. We agree that replacing the entire compartment assembly may be an alternative method of compliance (AMOC) to the modification requirements of this AD. However, we do not have service information which describes such a replacement. We consider delaying issuance of this AD until Boeing revises Boeing Special Attention Service Bulletin 737-25-1567 or develops other service information to be inappropriate, since we have determined that an unsafe condition exists and that modification of the door-mounted escape system must be done to ensure continued safety. However, under the provision of paragraph (h) of this AD, we might consider requests for approval of an AMOC if sufficient data are submitted to substantiate that such a design change would provide an acceptable level of safety. \n\tIn consideration of the ATA's concern about parts availability, we have confirmed with Boeing that it can provide the material listed in Boeing Special Attention Service Bulletin 737-25-1567 within the 60- month compliance time. The only new component required to modify the compartment assembly is the material for the enlarged window. Therefore, 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 received, and determined that air safety and the public interest require adopting the AD as proposed. \n\nCosts of Compliance \n\n\tThere are about 1,949 airplanes of the affected design in the worldwide fleet. This AD will affect about 660 airplanes of U.S. registry. The required modification and installation actions will take about 2 work hours per airplane, at an average labor rate of $80 per work hour. Required parts will cost about $207 per airplane. Based on these figures, the estimated cost of the AD for U.S. operators is $242,220, or $367 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 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 FindingsWe 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\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\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\tAirtransportation, 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 Federal Aviation Administration (FAA) amends Sec. 39.13 by adding the following new airworthiness directive (AD):