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 767 series airplanes was published in the Federal Register on April 14, 1999 (64 FR 18386). That action proposed to require modification of the engine thrust control cable installation; repetitive inspections to detect certain discrepancies of the cables, pulleys, pulley brackets, and cable travel; and repair, if necessary. For certain airplanes, that action also proposed to require replacement of certain pulleys with new pulleys, and re-rigging of the engine thrust control cable. \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. \n\nSupport for the Proposal \n\n\tOne commenter supports the proposed AD. \n\nRequest for Clarification on Allowable Part Numbers \n\n\tOne commenter requests clarification on which part numbers of aluminum pulleys will satisfy the intent of paragraph (b) of the proposed AD. This commenter states that it has accomplished Boeing Service Bulletin 767-76-0010, dated April 19, 1985, on its fleet. That bulletin specifies replacement of the non-metallic pulleys of the engine thrust control cable that are located in the leading edge of the wing adjacent to the left and right engine strut, with aluminum pulleys having the part number 255T1232-1. The proposed AD would require pulleys to be replaced in accordance with Boeing Service Bulletin 767-76-0010, Revision 1, dated February 20, 1992. That bulletin specifies that replacement with aluminum pulleys having the part number 255T1232-3 is preferred, but use of aluminum pulleys having the part number 255T1232-1 is allowed. The commenter states that, if aluminum pulleys having the part number 255T1232-3 are the only approved pulleys, the lack of availability of that pulley maycause unplanned delays in the accomplishment of the proposed AD. \n\n\tThe FAA intends that paragraph (b) of this AD require replacement of non-metallic pulleys of the engine thrust control cable that are located in the leading edge of the wing adjacent to the left and right engine strut, with aluminum pulleys having the part number 255T1232-1 or -3. Pulleys having the part number 255T1232-3 are preferred because they use a different bearing that has high temperature grease. After reviewing Boeing Service Bulletin 767-76-0010, dated April 19, 1985, the FAA finds that accomplishment of the replacement specified in that service bulletin is acceptable for compliance with the replacement required by paragraph (b) of the final rule; therefore, a note stating this has been added to the final rule. \n\nRequest for Information on Other Relevant Rulemaking \n\n\tOne commenter notes that the proposed rule states that the damage criteria in Appendix 1., "Thrust Control Cable Inspection Procedure," is based on the requirements in the Boeing 757 Maintenance Manual, which are more stringent than the requirements for the Model 767 series airplane. The commenter requests information regarding similar rulemaking for the Boeing Model 757 series airplane. No specific change to the rule is requested. \n\n\tThe FAA has issued two proposed rules to address the unsafe condition on other Boeing airplane models that have an engine thrust control cable installation similar to the Model 767 series airplane: \n\n\tFAA Rules Docket No. 98-NM-323-AD (64 FR 49105, September 10, 1999), which applies to certain Model 757-200 series airplanes; and \n\n\tFAA Rules Docket No. 99-NM-22-AD (64 FR 53275, October 1, 1999), which applies to certain Model 747 series airplanes. \n\n\tNo change to the final rule is necessary in this regard. \n\nRequest for Extension of the Compliance Time \n\n\tTwo commenters request that the compliance time for the repetitive inspections specified in paragraph (a) of the proposed AD be extended. One commenter suggests that its inspection program, which specifies inspection of different sections of the engine thrust control cable installation at intervals from 2,600 flight hours to 9,000 flight hours, including inspections of certain sections to be performed only on a sampling of airplanes in an operator's fleet, is adequate. Therefore, reducing the interval by 50 percent, as specified in the proposed AD, is unnecessary. The other commenter suggests that the engine thrust control cables be inspected at every "2C" check, with certain sections of the cable run to be inspected at every "C" check. (This commenter considers a "C" check interval to be 456 days.)\tThis commenter states that it will have to modify its maintenance program to accomplish the proposed repetitive inspections every 18 months or 4,500 flight hours. \n\n\tThe FAA does not concur with the commenters' request to extend the compliance time. There has been one engine thrust control cable failure on a Model 767 series airplane, and two failures on Model 757 series airplanes. (The engine thrust control cable installation on certain Model 757 series airplanes is similar to that on certain Model 767 series airplanes.) There was no evidence in these events that the operators were not following the Boeing maintenance planning document recommendations for the engine thrust control cable inspections. Given this experience and the possibly catastrophic effect of a thrust control cable failure, the FAA has determined that it is necessary to conduct more frequent inspections of the cable installations. Therefore, this AD requires the engine thrust control cable inspections to be accomplished every 18 months or 4,500 flight hours, whichever occurs first. No change to the final rule is necessary in this regard. \n\nRequest for Clarification of Applicability \n\n\tOne commenter requests clarification of the applicability of the proposed AD. The commenter states that this proposed AD affects Model 767 series airplanes powered by Pratt & Whitney JT9D series turbofan engines, and Model 767 series airplanes powered by General Electric CF6 series turbofan engines that do not use full authority digital electronic controls (FADEC). \n\n\tThe FAA concurs partially. This AD only affects certain Model 767 series airplanes powered by General Electric CF6 series turbofan engines that do not use FADEC (as well as Model 767 series airplanes powered by Pratt & Whitney JT9D series turbofan engines). Specifically, this AD affects Model 767 series airplanes powered by CF6-80A series turbofan engines. The engine thrust control cable installation is different on airplanes powered by other General Electric CF6 series turbofan engines that do not use FADEC, and the unsafe condition discussed previously does not exist on those airplanes. Therefore, no change to the final rule is necessary in this regard. \n\nExplanation of Changes Made to the Cost Impact \n\n\tThe FAA has been advised that the replacement of pulleys required by paragraph (b) of this AD has been accomplished on 23 airplanes of U.S. registry. Accordingly, the FAA has revised the cost impact, below, to reflect this information. Explanation of Changes Made to Appendix 1. \n\n\tPrompted by two comments received to FAA Rules Docket No. 98-NM-323-AD (64 FR 7822, February 17, 1999), which proposed actions similar to those required by this AD for the Model 757 series airplane, the FAA reviewed Appendix 1., "Thrust Control Cable Inspection Procedure," of the proposed AD. One commenter to FAA Rules Docket No. 98-NM-323-AD stated that the proposed procedure would require disassembly of the engine thrust control cable installation. The other commenter suggested that the procedure be revised to eliminate all steps that do not contribute to the intent of the AD. \n\n\tIn FAA Rules Docket No. 98-NM-323-AD (the FAA issued a supplemental NPRM for reasons other than the inspection procedure), the FAA concurred with the commenters' request to revise the inspection procedure. The FAA's intent was to define a thorough inspection of the engine thrust control cable installation while minimizing the amount of disruptive maintenance to the installation. With technical input from the airplane manufacturer, an improved and simplified inspection procedure has been developed, and Appendix 1. of this AD has been revised accordingly. Figure 2 of Appendix 1. has been removed because it is no longer needed for the inspection. The FAA has determined that the revision, although extensive, does not change the intent of the proposed procedure and actually decreases the scope of the inspection. In addition, the FAA has revised certain language in the preamble of this AD to reflect the changes to Appendix 1. \n\n\tIn addition, the FAA has corrected the summary of the final rule. The summary of the proposed AD stated a modification of the engine thrust control cable installation would be required on all affected airplanes. No such requirement was included in the proposed AD.\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 changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 211 airplanes of the affected design in the worldwide fleet. The FAA estimates that 100 airplanes of U.S. registry will be affected by this AD. \n\n\tFor all airplanes (100 U.S.-registered airplanes), it will take approximately 3 work hours per airplane to accomplish the required inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspection required by this AD on U.S. operators is estimated to be $18,000, or $180 per airplane, per inspection cycle. \n\n\tFor airplanes identified in Boeing Service Bulletin 767-76-0010, Revision 1 (52 U.S.-registered airplanes), it will take approximately 9 work hours per airplane to accomplish the required replacement and re-rigging, at an average labor rate of $60 per work hour. Required parts will cost $484 per airplane. Based on these figures, the cost impact of the replacement and re-rigging required by this AD on U.S. operators is estimated to be $53,248, or $1,024 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. However, the FAA has been advised that 23 airplanes of U.S. registry have been modified in accordance with Boeing Service Bulletin 767-76-0010, Revision 1, as required by paragraph (b) this AD. Therefore, the future economic cost impact of the required replacement and re-rigging on U.S. operators is now only $29,696, or $1,024 per airplane. \n\nRegulatory Impact \n\n\tThe regulations adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \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: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\t2. Section 39.13 is amended by adding the following new airworthiness directive: