A proposal to amend part 39 of the Federal Aviation Regulations to include an AD that applies to certain Collins TCAS II processors that are installed on aircraft was published in the Federal Register on September 9, 1993 (58 FR 47409). The action proposed to require (1) removing from service all processors that do not have computer logic "Change 6.04A" incorporated; and (2) mandatory incorporation of "Change 6.04A" into the TCAS II computer system.\n\n\tThe affected TCAS II processors are not designed for a specific aircraft type. The Collins TCAS II processors are installed on, but not limited to the following:\n\nGeneral Aviation Airplanes:\nAstra Model 1125 airplanes;\nBAC Model 1-11 airplanes;\nBritish Aerospace Model 125-800 airplanes;\nBeech Models C90A, B200, 300, 350, and 400A airplanes;\nCanadair Models CL-600, CL-600-2B16, CL-601, CL-601-1A, and CL-601-3A airplanes;\nLearjet Models 31, 55, and 60 airplanes;\nFalcon Models 20, 50, 200, and 900 airplanes\nGulfstream Models G2 and G3 airplanes; \nBritish Aerospace Models HS-125-700 airplanes; and\nSabreliner Model 60 airplanes.\n\nAir Transport Airplanes:\nAerospatiale Models ATR-42 and ATR-72 airplanes;\nAirbus Industries Models A300B2, A-300B, and A-320 airplanes;\nBritish Aerospace Models ATP and 146 airplanes;\nBoeing Models 707, 727, 737, 747, 757, and 767 airplanes;\nBritish Aerospace/Aerospatiale Model Concorde SST airplanes;\nde Havilland DHC-7 and DHC-8 series airplanes;\nMcDonnell Douglas Models DC-8, DC-9, and DC-10, MD-80, and MD-11 airplanes;\nIlyushin Model IL-86 airplanes;\nLockheed Model L-1011 airplanes;\nSAAB Models SF340A and SF340B airplanes; and\nShorts Models SD3-60-300 airplanes.\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 from 31 different owners, operators, manufacturers, and organizations.\n\n\tAll commenters express their concern of theFAA's compliance date of December 30, 1993. The following summarizes the compliance times that the commenters recommended:\n\n21 recommended one year or less;\n\n3 recommended longer than one year; and\n\n7 recommended an extension without a proposed time.\n\nThe National Air Traffic Controllers Association and the Airline Pilots Association both recommend an "aggressive implementation" of "Change 6.04A". The FAA has re-evaluated the December 30, 1993, compliance time and has determined that the compliance time should be changed to December 31, 1994. In addition, "Change 6.04A" has been upgraded to "Change 6.04A Enhanced", which eliminates unnecessary non-crossing resolution advisories (RA's) included in "Change 6.04A". Collins has assured the FAA that (1) the upgrade to "Change 6.04A Enhanced" is minor and will be incorporated in the logic change for the TCAS II processor upgrades; and (2) this compliance time correlates with their schedule for disseminating service information and kits necessary to accomplish the incorporation of "Change 6.04A Enhanced". The proposed AD has been changed to reflect the compliance time change and logic change described above.\n\n\tOne commenter states that the affected aircraft operators should operate their TCAS II units in the "TA Mode Only" until the new logic is incorporated because of possible hidden problems that could exist between different logic versions currently installed. The FAA does not concur that these TCAS II units should be operated in the "TA Mode Only". The information provided by an RA may prove to be useful to the pilot. The pilot has the option of whether to utilize the RA information. The proposed AD is unchanged as a result of this comment.\n\n\tA commenter recommends referencing Collins Service Bulletin (SB) No. 16, TTR-920-34-16, dated December 9, 1993, as a way of complying with the proposed AD. The FAA concurs that this service information is a way of complying with the proposed action, and hasincluded a note in the final rule that so indicates this.\n\n\tAnother commenter proposes a change to the proposed AD that would allow reprogramming the existing unit on board the aircraft as a method of compliance with the proposed action. The FAA concurs that certain existing TCAS II part numbers may be reprogrammed with the unit on board the aircraft. The proposed AD has been modified to include this method on the applicable TCAS II processor part numbers.\n\n\tOne commenter states that reference to the SAAB 340B airplanes in the General Aviation Airplanes list should be deleted. This commenter also recommends that reference to the Aerospatiale ATR-42 and ATR-72 airplanes be moved from the General Aviation Airplanes list to the Air Transport Airplanes list. The FAA concurs and has revised the proposed AD accordingly.\n\n\tOne commenter, who supports the implementation of "Change 6.04A Enhanced", requests that the FAA issue a supplementary notice of proposed rulemaking (NPRM) to propose installing this revised software by June 30, 1995. This commenter states that significant differences exist between "Change 6.04A" and "Change 6.04A Enhanced". The FAA does not concur. Comments received in response to the proposed AD reflect unanimous support for implementing "Change 6.04A Enhanced". The FAA considers the logic change (which reduces non-crossing RA's) to be minor. The intent is to correct the unsafe condition by installing modified TCAS II computer units that incorporate updated logic. The FAA has determined that the requirement to implement Version 6.04A software, including the latest enhancement, will (1) correct the unsafe condition; (2) maintain the same intent originally proposed without altering the substance of the proposed rule; and (3) impose no additional burden on the public than was previously proposed.\n\n\tIn addition, issuing a supplemental NPRM would necessitate (under the provisions of the Administrative Procedures Act) reissuing the notice,reopening the public comment period, considering any additional comments received, and eventually issuing a final rule. The time required for these procedures could take as long as four additional months. In light of this, and in consideration of the amount of time that has already elapsed since issuance of the original NPRM, the FAA concludes that soliciting further public comment is not necessary and that further delay of the final rule action is not appropriate.\n\n\tSeveral commenters request that the FAA revise the economic impact specified in the proposed AD to reflect costs associated with the development, testing prior to certification, and certification of the modified processor. These costs would be absorbed by suppliers, installers, and airline operators. The FAA does not concur that the economic impact statement include this information. The 5 workhours necessary to accomplish the proposed action was provided to the FAA by the TCAS II processor manufacturer based on thebest data available to date. This number represents the time required to install the revised software and test for proper operation after installation. The cost analysis in AD rulemaking actions typically does not include costs associated with development, testing prior to certification, and certification of a modified processor. The proposed action remains unchanged as a result of these comments.\n\n\tAfter careful review of all available information including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for the change in compliance time, the logic reference change, the option of reprogramming certain units on board the aircraft, reference to Collins SB No. 16, TTR-920-34-16, dated December 9, 1993, and minor editorial corrections. The FAA has determined that these changes and corrections will not change the meaning of the AD nor add any additional burden upon the public than was already proposed.\n\n\tThe FAA estimates that 1,995 TCAS II processors in the U.S. registry will be affected by this AD, that it will take approximately 5 workhours per processor (1 workhour for installation and 4 workhours for operational testing) to accomplish the required action, and that the average labor rate is approximately $55 an hour. Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $548,625. These figures are based on the assumption that none of the operators of the airplanes equipped with the affected TCAS II processors have accomplished the actions specified in this AD.\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 copy of the final evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting 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, Safety.\n\nAdoption of the Amendment\n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 14 CFR part 39 of the Federal Aviation Regulations as follows:\n\nPART 39 - AIRWORTHINESS DIRECTIVES\n\t1.\tThe authority citation for part 39 continues to read as follows:\nAuthority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.\n\nSection 39.13 - (AMENDED)\n\t2.\tSection 39.13 is amended by adding the following new AD: