The FAA proposed to amend 14 CFR part 39 with an AD for certain Boeing Model 737-100, -200, -200C, and -300 series airplanes. That action, published in the Federal Register on August 17, 2004 (69 FR 51017), proposed to require repetitive detailed inspections to detect discrepancies of the retaining pin lugs on the support fitting of the main landing gear (MLG) beam, and rework of the support fitting or replacement of the fitting if necessary. \n\nComments \n\n\tWe provided the public the opportunity to participate in the development of this AD. We have considered the comments that have been submitted on the proposed AD. \n\nAgreement With the Proposed AD \n\n\tOne commenter, the manufacturer, agrees with the proposed AD. \n\nConditional Agreement With the Proposed AD \n\n\tOne commenter, an operator, agrees with the proposed AD provided that there are adequate parts available if the discrepant condition is found. \n\n\tThe FAA agrees that adequate availability ofparts is necessary. We have received no information from the manufacturer concerning a possible delay in availability of parts. In the event there is a delay in the availability of parts, an operator may request approval for an alternative method of compliance as specified in paragraph (k)(1) of this AD. \n\nRequest for Clarification of Paragraph (g) of the Proposed AD \n\n\tOne commenter, an operator, requests additional information and clarification regarding the reference in paragraph (g)(2) of the proposed AD to replacing the fittings in accordance with the Accomplishment Instructions, Part III--Fitting Replacement, of Boeing Service Bulletin 737-57-1216, Revision 2, dated May 6, 1999. The commenter notes that, in certain situations, those Accomplishment Instructions instruct the operator to install a self-locking nut to secure the support pin of the MLG support beam. However, the commenter advises that installing a self-locking nut would be in conflict with AD 2002-02-08 (67 FR 6372, February 12, 2002). \n\n\tWe agree that clarification of paragraph (g)(2) of the AD is necessary in order to prevent a conflict between the requirements of this AD and AD 2002-02-08. Therefore, we have added further information to paragraph (g)(2) of the AD to specify that, if operators choose to accomplish the corrective action specified in paragraph (g)(2) of the AD, replacing the fitting in accordance with the Accomplishment Instructions, Part III--Fitting Replacement, of Boeing Service Bulletin 737-57-1216, Revision 2, dated May 6, 1999, must also include replacing the retaining bolt, self-locking nut, and associated hardware of the support beam for the MLG with a new bolt, castellated nut, and new hardware; in accordance with Boeing Service Bulletin 737-57A1260, Revision 2, dated October 18, 2001. \n\nRequest for Credit for Accomplishing Certain Service Bulletins \n\n\tOne commenter, an operator, requests that the original issue, dated December 17, 1992, and Revision 1, dated September 23, 1993, of Boeing Service Bulletin 737-57-1216 be approved as acceptable for terminating the requirements of the proposed AD. The commenter states that the original issue and Revision 1 provide procedures for replacing the fitting that are essentially the same as those in Revision 2, which is cited as the appropriate service information in paragraph (g)(2) of the proposed AD. \n\n\tWe agree with the commenter for the reason stated and have revised paragraph (g)(2) of the AD accordingly. \n\nRequest To Clarify Paragraph (j) of the Proposed AD \n\n\tOne commenter, an operator, requests that the fittings acceptable for installation be stated in a more definite manner than "a new lug." The commenter suggests that paragraph (j) of the proposed AD be revised to specify a part number or serial number, rather than just "a new lug." The commenter also requests that the inspection and rework instructions of paragraph (j) of the proposed AD be more specific. \n\n\tWe agree that clarifyingthe intent of the words "new lug" is necessary. Although the inspection requirements of this AD are intended to detect cracking of "the retaining pin lugs of the support fitting of the MLG, or elongation of a bolt hole in a lug," the corrective actions of paragraph (g) of this AD require reworking or replacing the fittings. We specify reworking or replacing the fittings, rather than the lugs, since the lugs are not available as individual replacement parts. The intent and purpose of paragraph (j) of this AD is to specify that any lug must be inspected and the fitting reworked or replaced, as applicable, except for those fittings that previously have been reworked or replaced, in accordance with paragraph (g) of this AD. We have revised paragraph (j) of the AD accordingly. We do not, however, agree that the inspection and rework instructions of paragraph (j) of the AD need to be more specific. The requirements of paragraph (j) of the AD indicate multiple actions that are clearly encompassed by stating "in accordance with this AD," rather than to specify each action that has already been stated in previous paragraphs of the AD. \n\nChanges to Delegation Authority \n\n\tBoeing has received a Delegation Option Authorization (DOA). We have revised this final rule to delegate the authority to approve an alternative method of compliance for any repair required by this AD to the Authorized Representative for the Boeing DOA Organization rather than the Designated Engineering Representative (DER). \n\nConclusion \n\n\tWe have carefully reviewed the available data, including the comments that have been submitted, 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\tThere are about 1,670 airplanes worldwide of the affected design and 668 airplanes of U.S. registry. The required actions take about 2 work hours per airplane, at an average labor rate of $65 per work hour. Based on these figures, the estimated cost of the required actions for U.S. operators is $86,840, or $130 per airplane, per inspection cycle. \n\n\tThe rework, if accomplished, will take about 24 work hours per airplane to accomplish at an average labor rate of $65 per work hour. Required parts will cost about $1,006 per airplane. Based on these figures, the cost impact of the rework provided by this AD is estimated to be $2,566 per airplane. \n\n\tThe replacement of the support fitting of the MLG beam, if accomplished, will take about 128 work hours per airplane to accomplish at an average labor rate of $65 per work hour. Required parts will cost between $4,540 and $5,271 per airplane. Based on these figures, the cost impact of the replacement provided by this AD is estimated to be between $12,860 and $13,591 per airplane. \n\n\tThe replacement of the support fitting and installation of a special bushing of the MLG beam (for Group 9 and Group 10 airplanes), if accomplished, will take about 144 work hours per airplane to accomplish at an average labor rate of $65 per work hour. Required parts will cost about $5,081 per airplane. Based on these figures, the cost impact of this replacement and installation is estimated to be $14,441 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\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\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\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\n\t(2) Is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and \n\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\n\tWe prepared a regulatory evaluation of the estimated costs to comply with this AD. See the ADDRESSES section for a location to examine the regulatory evaluation. \n\nList of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.