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 737-600, - 700, -700C, -800, and -900 series airplanes was published in the Federal Register on November 15, 2002 (67 FR 69157). That action proposed to require installing speedbrake limitation placards in the flight compartment, and revising the Limitations Section of the Airplane Flight Manual (AFM) to ensure the flightcrew is advised not to extend the speedbrake lever beyond the flight detent. For certain airplanes, that action also proposed to require modifying the elevator and elevator tab assembly. \n\nComments \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. One commenter concurs with the proposed AD. Two commenters state that they have no comments on the proposed AD. \n\nRequest To Clarify Certain Language in Paragraph (a)(2) \n\n\tOne commenter asks that certain language, as specified in paragraph (a)(2) of the proposed AD, be clarified. The commenter notes that the current language, which is to be included in the AFM, states the following: "Do not extend the speedbrake lever beyond the flight detent in flight." That statement, as written, does not match the language specified in the existing AFM. The language should be changed, for clarification, to match the AFM language and should state: "In flight, do not extend the speedbrake lever beyond the FLIGHT detent." \n\n\tThe FAA agrees with the commenter in that the language used in paragraph (a)(2) of the AD should be clarified to match the AFM language. We have changed paragraph (a)(2) of this final rule accordingly. \n\nRequest To Change Discussion Section \n\n\tThe same commenter asks that the Discussion section of the proposed AD be changed to remove the reference to Boeing Model 737-900 series airplanes from the first sentence. That sentence states, "The FAA has received several reports of excessive in-flight vibrations of the elevator and elevator tab on certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes." The commenter notes that no excessive in-flight vibrations of the elevator and elevator tab have occurred on Model 737-900 series airplanes. \n\n\tThe same commenter asks that certain terminology in the Discussion section of the proposed AD be changed. That section reads, in part, "(t)he elevator and elevator tab are susceptible to excessive vibration and, under certain conditions, limit-cycle flutter. These vibration events have been attributed to loose or missing components, excessive wear, or excessive freeplay of the tab." The commenter requests that it be changed to, "(t)he elevator and elevator tab are susceptible to excessive vibration and, under certain conditions, limit-cycle oscillation (LCO). These vibration events have been attributed to lack oftorsional rigidity (in the case of LCO); or missing components, excessive wear, or excessive freeplay of the tab." The commenter states that LCO is the accepted and proper term to use when referring to the severe vibrations associated with lack of torsional stiffness. \n\n\tWe acknowledge that no excessive in-flight vibrations of the elevator and elevator tab have been reported on Model 737-900 series airplanes in-service. The intent of the Discussion section is to provide the background and events that prompted the proposed AD, and to specify that vibrations did occur on Model 737-600, -700, -700C, and - 800 series airplanes in-service. \n\n\tWe acknowledge that the term "lack of torsional rigidity" is a valid term and could be used to describe a design deficiency that also contributes to excessive in-flight vibration. However, the terms "LCO" and "LCF" are not commonly used terms in the airline industry; these terms are used primarily by airplane manufacturers. We have concluded thatthe term "high amplitude oscillations of the elevator tab" best describes the condition in a manner understood by the airline industry. \n\n\tSince the Discussion section of a proposed AD is not restated in a final rule, no change to this final rule is necessary to address the issues raised by the commenters. \n\nConclusion \n\n\tAfter 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 that this change will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 1,174 airplanes of the affected design in the worldwide fleet. We estimate that 550 airplanes of U.S. registry will be affected by this AD. \n\n\tIt will take approximately 1 work hour per airplane to accomplish the required placard installation, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the required installation on U.S. operators is estimated to be $33,000, or $60 per airplane. \n\n\tIt will take approximately 1 work hour per airplane to accomplish the required AFM revision, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the required revision on U.S. operators is estimated to be $33,000, or $60 per airplane. \n\n\tIt will take approximately 88 work hours per airplane to accomplish the required modification of the elevator and elevator tab assembly, at an average labor rate of $60 per work hour. The FAA has been advised by Boeing that the manufacturer will provide parts for the elevator/tab retrofit, including shipping, at no cost to operators. The manufacturer will have operators "exchange" their existing parts for new parts to support the retrofit program. Based on this information, the cost impact of the required modification on U.S. operators is estimated to be $2,904,000, or $5,280 per airplane. \n\n\tThe cost impact figures discussed above are 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 the 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\tThe 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\tFor 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 ADDRESSES. \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\n\tAccordingly, 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\t1. 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\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: