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 757-200, -200PF, and -200CB series airplanes was published as a supplemental notice of proposed rulemaking (NPRM) in the Federal Register on September 10, 1999 (64 FR 49105). That action proposed to require modification of the engine thrust control cable installation, and repetitive inspections to detect certain discrepancies of the cables, pulleys, pulley brackets, and cable travel; and repair, if necessary. That action also proposed to require a one-time inspection to determine the part number of thrust control cable pulleys and replacement of existing pulleys with new pulleys, if necessary.\n\nComments\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\tOne commenter supports the proposed rule, and one commenter states that it is not affected by the rule and has no comments.\n\nRequest to Include Additional Source of Service Information\n\tOne commenter requests that the FAA cite Boeing Service Bulletin 757-30A0018, Revision 2, dated September 9, 1999, as an additional source of service information for accomplishment of the modification specified in paragraph (e) of the proposed rule.\n\tThe FAA concurs with the commenter's request. Boeing Service Bulletin 757-30A0018, Revision 2, removes an airplane that has a different routing of the window heat wire bundle (and, therefore, does not need the support bracket assembly to ensure proper clearance between the wire bundle and engine thrust control cable) from the effectivity listing. In addition, Revision 2 corrects minor errors in the accomplishment instructions. The FAA has revised paragraph (e) of the final rule to state that the paragraph is applicable to airplanes listed in Revision 2 of the service bulletin. Also, paragraph (e) has been revised to reference Revision 2 of the service bulletin, in addition to Boeing Alert Service Bulletin 757-30A0018, Revision 1, dated September 17, 1998 (which was cited in the proposal), as appropriate sources of service information.\n\nRequest to Revise Cost Impact\n\tOne commenter states that it would take approximately 18 work hours per airplane to accomplish the inspection specified in paragraph (a) of the proposed rule. The commenter also requests that the Cost Impact section include the estimated cost for replacement of phenolic pulleys with aluminum pulleys, specified in paragraph (b) of the proposed rule. The FAA concurs with the commenter's requests and has revised the Cost Impact section of the final rule in accordance with new cost data provided by the commenter and the airplane manufacturer.\n\nRequest to Revise Applicability\n\tOne commenter requests that Model 757-200PF series airplanes be removed from the applicability of the proposed AD. The commenter states that Model 757-200PF series airplanes are not listed in the effectivity of any of the Boeing service bulletins referenced in the proposed AD.\n\tThe FAA does not concur. Although Model 757-200PF series airplanes are not subject to paragraphs (c), (d), and (e) of the final rule (which reference Boeing service bulletins), these airplanes are subject to paragraphs (a) and (b). The engine installation of the Rolls-Royce Model RB211-535E4 turbofan engine on the Model 757-200 and -200PF series airplanes is identical; therefore, the same unsafe condition exists. No change to the final rule is necessary in this regard.\n\nRequest to Eliminate Repetitive Inspections\n\tOne commenter requests that the repetitive inspections of the engine thrust control cables be removed from the proposed AD. The commenter states that the proposed rule addresses specific failure modes of the cables, and that once those corrective actions have been accomplished, the existing Boeing Maintenance Planning Document (MPD) inspection interval is adequate. The commenter states that the tracking and records burden of the repetitive inspections would not provide a cost-effective benefit or substantially increase safety margins. The commenter suggests that, if the FAA determines that more frequent inspections are necessary, a maintenance review board (MRB) revision would be the most appropriate means to provide for such inspections.\n\tThe FAA does not concur with the commenter's request. The corrective actions and modifications to the engine thrust control cable installation specified in paragraphs (b) through (e) of the AD do not eliminate the unsafe condition. The thrust reverser control system on this airplane model is such that, when the engine thrust control "B" cable fails during landing, it changes the position of the thrust reverser directional control valve causing the thrust reverser to stow and the engine to accelerate. The oppositeengine is unaffected by the cable failure and remains in full reverse. This severe asymmetric thrust condition during landing is the unsafe condition. None of the modifications required by this AD change the failure mode of the cable. The repetitive inspections specified in paragraph (a) of the AD are intended to detect wear and corrosion prior to cable failure. Such wear and corrosion could be caused by numerous problems, not just those addressed by the actions specified in paragraphs (b) through (e) of the AD. Furthermore, a revision to the MRB report would not adequately address the unsafe condition. The MRB process allows for extension of inspection intervals, on an operator-by-operator basis, based on the rate of discrepancies identified in previous inspections. The discrepancies detected during the repetitive inspections would not necessarily be chronic problems but could be induced by unrelated airplane configuration changes near the cable run. No change to the final rule is necessary in this regard.\n\nRequest to Extend Repetitive Inspection Interval\n\tOne commenter requests that the interval for the repetitive inspections specified in paragraph (a) of the proposed rule be extended to an interval coinciding with a "2C" check. The commenter states that this is what is currently required by the Boeing MPD.\n\tThe FAA does not concur. There have been two engine thrust control cable failures on Model 757 series airplanes. One event was described in the NPRM. Another event, which the FAA became aware of shortly before the NPRM was released, occurred in January 1999. There was no evidence in these events that the operators were not following the Boeing MPD recommendation for thrust control cable inspections every "2C" check. Given this experience and the possibly catastrophic effect of a thrust control cable failure, the FAA has determined that it is necessary to require more frequent inspections of the cable installation. Therefore, this AD requires the cable inspection at an interval coinciding approximately with a "C" check for the majority of the affected fleet. No change to the final rule is necessary in this regard.\n\tIn addition, two commenters request that the repetitive interval for the inspections specified in paragraph (a) of the proposed rule be extended. The commenters suggest intervals that would coincide with the commenters' own "C" check intervals. One commenter states that the proposed interval would require special scheduling and would create an economic burden. The other commenter notes that the FAA stated in the proposed rule that it is the FAA's intent that the inspections be performed during a regular scheduled maintenance visit.\n\tThe FAA does not concur with the commenters' request to extend the compliance time. In developing an appropriate compliance time for this action, the FAA considered not only the practical aspect of accomplishing the inspections at an interval of time that parallels normal scheduled maintenance for the majority of affected operators, but the possible failure modes of the engine thrust control cables. In consideration of these items, as well as the in-service failures of the cables described previously, the FAA has determined that 24 months or 6,000 flight hours, whichever occurs first, represents an appropriate interval of time allowable wherein the inspections can be accomplished during scheduled maintenance intervals for the majority of affected operators, and an acceptable level of safety can be maintained. No change to the final rule is necessary in this regard.\n\nRequest to Eliminate One-Time Inspection\n\tOne commenter requests that paragraph (b) of the proposed rule, which requires a one-time inspection of the engine thrust control cable pulleys in the struts and replacement of any phenolic pulleys with aluminum pulleys, be removed. Instead, the commenter suggests that the phenolic pulleys be replaced with aluminum pulleys only if damage is detected during the repetitive inspections specified in paragraph (a) of the proposed rule. The commenter states that the repetitive inspections would preclude the elapse of a significant time period of operation with a seized pulley and that a seized pulley would be identified before any significant cable wear could occur. \n\tThe FAA does not concur. Although the in-service problems with the phenolic pulleys in a high-temperature environment have not resulted in an engine thrust control cable failure, the FAA has determined that there is enough variability in how airplanes in the fleet are operated, in addition to the possible catastrophic effect of a cable failure, to warrant removal of the phenolic pulleys prior to seizure. Therefore, no change to the final rule is necessary in this regard.\n\nRequest to Clarify Affected Part Numbers\n\tTwo commenters suggest that phenolic engine thrust control cable pulleys having part number (P/N) BACP30M4 in the strut be included in any requirement that specifies phenolic pulleys having P/N 65B80977-1. The commenters state that pulleys having P/N BACP30M4 are interchangeable with pulleys having P/N 65B80977-1 and are installed on many of the airplanes affected by the proposed rule.\n\tThe FAA concurs. Paragraph (b) of the final rule has been revised to include phenolic pulleys having P/N BACP30M4. The FAA has determined that this addition does not necessitate reopening of the comment period. The supplemental NPRM clearly states in the preamble that the unsafe condition is associated with any phenolic pulleys in the struts, not just those having P/N 65B80977-1. Therefore, the FAA finds that the public has had a reasonable opportunity to comment on its intent.\n\nRequest for Information on Service Information\n\tOne commenter notes that paragraph (b) of the proposed rule does not reference a service bulletin. The commenter requests information regarding the availability of service information for the actions specified in paragraph (b), and the configuration of the airplanes to which paragraph (b) applies at the time of airplane delivery to the operator. No specific change to the rule is requested.\n\tThe FAA agrees that paragraph (b) of the proposed rule does not reference a service bulletin. The airplane manufacturer has not issued a service bulletin for the Model 757 series airplane describing procedures for the actions specified in paragraph (b); however, it has published Boeing Service Letter 757-SL-004-A, dated July 21, 1997, addressing this subject. Model 757 series airplanes powered by Rolls-Royce engines and having line numbers 1 through 636 inclusive were delivered from the airplane manufacturer to the operator with phenolic pulleys installed in the struts. Airplanes having line numbers 637 and subsequent were delivered with aluminum pulleys installed in the struts. No specific change to the final rule is necessary in this regard.\n\nRequest to Extend Compliance Time for Modification\n\tOne commenter requests that the compliance time for the modification specified in paragraph (e) of the proposed rule be extended. The commenter suggests no specific compliance time. The commenter states that a single failure without sufficient evidence that the engine thrust control cable was being inspected in accordance with the Boeing MPD does not warrant regulatory action within 60 days.\n\tThe FAA does not concur with the commenter's request to extend the compliance time. In developing an appropriate compliance time for this action, the FAA considered the safety implications, parts availability, and normal maintenance schedules for timely accomplishment of the modification. In consideration of these items, as well as a report of another airplane with contact between the window heat wire bundle and engine thrust control cables in service, the FAA has determined that 60 days represents an appropriate interval of time allowable wherein the modifications can be accomplished during scheduledmaintenance intervals for the majority of affected operators, and an acceptable level of safety can be maintained. No change to the final rule is necessary in this regard.\n\nExplanation of Other Changes to Cost Impact\n\tThe cost impact section, below, has been revised. The applicability of the AD has not changed, but because the airplane model affected by this AD is continuing to be manufactured, the number of affected airplanes has increased slightly since publication of the proposed rule. Also, the proposed rule estimated the cost of the one-time inspection for all airplanes; however, this action only applies to a limited number of airplanes.\n\nConclusion\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\tThere are approximately 500 Model 757-200, -200PF, and -200CB series airplanes of the affected design in the worldwide fleet. The FAA estimates that 257 airplanes of U.S. registry will be affected by this AD.\n\tFor all airplanes, it will take approximately 18 work hours per airplane to accomplish the required inspection to verify the integrity of the thrust control cables, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this inspection required by this AD on U.S. operators is estimated to be $277,560, or $1,080 per airplane, per inspection cycle.\n\tFor airplanes required to accomplish the one-time inspection to determine the part number of the thrust control cable pulleys (142 U.S.-registered airplanes), it will take approximately 1 work hour per airplane, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this inspection required by this AD on U.S. operators is estimated to be $8,520, or $60 per airplane.\n\tShould an operator be required to accomplish the pulley replacement, it will take approximately 16 work hours per airplane, at an average labor rate of $60 per work hour. Required parts will cost approximately $2,224 per airplane. Based on these figures, the cost impact of this inspection required by this AD on U.S. operators is estimated to be $3,184 per airplane.\n\tFor airplanes identified in Boeing Service Bulletin 757-76-1 (8 U.S.-registered airplanes), it will take approximately 2 work hours per airplane to accomplish the required guide bracket removal, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this replacement required by this AD on U.S. operators is estimated to be $960, or $120 per airplane.\n\tFor airplanes identified in Boeing Service Bulletin 757-76-0005 (14 U.S.-registered airplanes), it will take approximately 14 work hours per airplane to accomplish the required replacement, atan average labor rate of $60 per work hour. Required parts will cost approximately $1,410 per airplane. Based on these figures, the cost impact of this replacement required by this AD on U.S. operators is estimated to be $31,500, or $2,250 per airplane.\n\tFor airplanes identified in Boeing Alert Service Bulletin 757-30A0018, Revision 1 (167 U.S.-registered airplanes), it will take approximately 2 work hours per airplane to accomplish the required installation and adjustment, at an average labor rate of $60 per work hour. Required parts will cost approximately $192 per airplane. Based on these figures, the cost impact of this installation and adjustment required by AD on U.S. operators is estimated to be $52,104, or $312 per airplane.\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. \n\nRegulatory Impact\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\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\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.\nAdoption of the Amendment \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: \nPART 39 - AIRWORTHINESS DIRECTIVES\n\t1. The authority citation for part 39 continues to read as follows:\nAuthority: 49 U.S.C. 106(g), 40113, 44701. \n§ 39.13 (Amended)\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: