A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737 series airplanes was published as a supplemental notice of proposed rulemaking (NPRM) in the Federal Register on June 5, 2001 (66 FR 30114). That action proposed to require inspection of wire bundles in four junction boxes in the main wheel well to detect chafing or damage, and follow-on actions.\n\nComments\n\n Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.\n\n One commenter concurs with the proposed rule; another commenter indicates that it is already accomplishing the proposed inspections and has no further comments.\n\nExtend Compliance Time\n\n One commenter asks that we extend the compliance time for the proposed requirements from 12 to 18 months after the effective date of the AD. The commenter states that the 12-month compliance time is not a sufficient amount of time to perform the inspection (check) during its 737 fleet 'C-check' cycle. The assessment was based on the amount of \noperational testing that would have to be performed on the systems that would be disturbed by the proposed inspections and modifications. The commenter recommends the compliance time be extended to 18 months to \nensure the inspection may be accomplished during a scheduled maintenance visit.\n\n The FAA agrees to extend the compliance time for the inspection to 18 months. In developing an appropriate compliance time for the inspection required by the final rule, we considered not only the degree of urgency associated with addressing the unsafe condition, but the practical aspect of accomplishing the inspection of the wire bundles on the Model 737 fleet in a timely manner. It is our intent in this final rule to allow the inspections to be done within the time \nframe of a regular maintenance interval. We took the commenter's recommendations into account, as well as the time necessary to do the specified actions, and we find that an 18-month compliance time should correspond with the regular maintenance schedules of the majority of affected operators. An extension of the compliance time to 18 months will not adversely affect safety. Paragraph (a) of the final rule has been changed accordingly.\n\n Two commenters ask that the proposed compliance time be extended to 24 months. One commenter, the airplane manufacturer, states that, based on input from the airlines and an internal Boeing review, the compliance time should be extended. The commenter notes that this extension will provide adequate time for compliance to operators with \nlarge fleets because they will be able to accomplish the inspection during routine maintenance, rather than scheduling an inspection specifically to address the proposed rule. The second commenter states that a 24-month compliance time would allow it to accomplish the inspections during regularly scheduled maintenance.\n\n We do not agree to extend the compliance time for the inspection to 24 months. We have already considered factors such as operators' maintenance schedules in setting a compliance time for the required modification, and have determined that 18 months is an appropriate compliance time in which the inspection may be accomplished during \nscheduled airplane maintenance for the majority of affected operators. Since maintenance schedules vary from operator to operator, it would not be possible to guarantee that all affected airplanes could be modified during scheduled maintenance, even with a compliance time of 24 months. In any event, we find that 18 months represents the maximum time wherein the affected airplanes may continue to operate prior to inspection without compromising safety. No further change to the final rule is necessary in this regard.\n\nAdd New Service Information\n\n One commenter asks that Boeing Service Letter 737-SL-24-138, dated May 24, 1999, be added to the proposed rule as another source of service information for accomplishment of certain actions related to those specified in the proposed rule. The service letter was referenced in a Civil Airworthiness Authorities' Additional Airworthiness \nDirective.\n\n On July 2, 2001, the FAA issued AD 2001-14-06, amendment 39-12316 (66 FR 36445, July 12, 2001), which references that service letter as the appropriate source of service information for accomplishment of the inspections of the circuit connectors of the fuel shutoff valve in the main wheel well. As the service letter has been addressed in another \nAD, no change to the final rule is necessary in this regard.\n\nChange Certain Requirements\n\n One commenter asks that the proposed requirement of wire protection features, as specified in paragraph (a)(1) of the proposed rule, be changed to agree verbatim with the procedures specified in Boeing Service Letter 737-SL-24-111, dated February 27, 1996. The commenter states that the proposed requirement implies that the protective methods need to be incorporated regardless of the condition of the wire bundles, whereas the service letter does not specify incorporation of wire protection features unless contact between the wiring and junction box is found. The commenter adds that such action would require re-inspection of the fleet, in addition to added work that may be unjustified. The commenter also adds that installation of wire protection would not be necessary in that the affected wire bundles are \nshort in length and, due to the relatively rigid nature of the installation at the pressure seal, if a wire bundle was found to have adequate clearance from the cover, this condition probably would not change.\n\n The FAA does not agree. Although there may be no damage to the wiring found during the inspection, the chafing condition that prompted this rulemakingaction could still develop eventually, due to airplane vibration. Incorporation of the wire protection features will ensure that this condition does not develop. No change to the final rule is necessary in this regard.\n\nAdd Work Hours to Cost Impact Section\n\n One commenter asks that the estimate of 8 work hours per airplane for doing the proposed actions, as specified in the Cost Impact section of the proposed rule, be changed. The commenter states that the estimate is not accurate based on the amount of operational checks required after disturbing the affected connectors/systems in the junction boxes to repair damage to wiring. The commenter recommends that the estimate be changed to 35 work hours per aircraft and adds that this labor estimate is based on its experience with accomplishment of the original release of the referenced service letter.\n\n The FAA does not agree with the commenter's request to include the work hours necessary for repairs of the wiring and subsequent operational checks in the Cost Impact section of the proposed AD. The Cost Impact section only includes the "direct" costs of the specific actions required, which include inspecting the wire bundles and protecting the wires from chafing. The AD does not include the cost of "on-condition" actions, such as repair of the wiring if chafing is \ndetected during the required inspection (''repair, if necessary''). Such on-condition repair actions would be required to be accomplished, regardless of AD direction, to correct an unsafe condition identified in an airplane and to ensure the airworthiness of that airplane, as required by the Federal Aviation Regulations. No change to the work hour estimate in the final rule is necessary.\n\nConclusion\n\n After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined thatthis change will neither increase the economic burden on any operator nor increase the scope of the AD.\n\nCost Impact\n\n There are approximately 3,719 airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,467 airplanes of U.S. registry will be affected by this AD, that it will take approximately 8 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. The cost of required parts \nwill be negligible. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $704,160, or $480 per airplane.\n\n The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform \nthe specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.\n\nRegulatory Impact\n\n The regulations adopted herein 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. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.\n\n For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action"under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption \nADDRESSES.\n\nList of Subjects in 14 CFR Part 39\n\n Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.\n\nAdoption of the Amendment\n\n Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:\n\nPART 39--AIRWORTHINESS DIRECTIVES\n\n 1. The authority citation for part 39 continues to read as follows:\n\n Authority: 49 U.S.C. 106(g), 40113, 44701.\n\n\nSec. 39.13 (Amended)\n\n 2. Section 39.13 is amended by adding the following new airworthiness directive: