A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 94-25-10, amendment 39-9094 (59 FR 64112, December 13, 1994), which is applicable to all Raytheon (Beech) Model 400, 400A, 400T, and MU-300-10 airplanes, and all Mitsubishi Model MU-300 airplanes, was published in the Federal Register on February 26, 1997 (62 FR 8650). That action proposed to continue to require a revision to the Airplane Flight Manual (AFM) to provide pilots with special operating procedures during icing conditions, and proposed to require modification of the horizontal stabilizer ice protection system. That action also proposed to remove Model MU-300 airplanes from the applicability of the existing AD. (The FAA is in the process of issuing separate rulemaking action (Docket 96-NM-210-AD) for Model MU-300 airplanes that will require, among other things, certain AFM revisions and installation of an ice detector on those airplanes.) That proposal was prompted by the development of a modification that will positively address the unsafe condition. The proposed requirements of that action are intended to prevent uncommanded nose-down pitch at certain flap settings during icing conditions. \n\nActions Since the Issuance of the NPRM \n\tThe FAA has reviewed and approved Raytheon Service Instructions No. T-1A-0064 (undated). This service information describes procedures for installation of an additional anti-ice control valve and pressure switch for the bleed air supply in the aft fuselage compartment, and an ice detector on the nose of the aircraft, and related annunciators, relays, a selector switch, and electrical wiring in the flight compartment and fuselage areas. In addition, the service information contains a "Note" that provides procedures to perform if icing conditions are encountered during flight. \n\nComments to the NPRM \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\nRequest to Delay Issuance of the Final Rule \n\tOne commenter requests that the FAA delay the issuance of the final rule until a new modification of the horizontal stabilizer icing protection system is available for field installation on the Model 400T. The commenter states that such a modification would require less down time of the airplane and lower costs to the operator. \n\n\tThe FAA considers that a delay in issuance of this final rule is unnecessary. The FAA considers that accomplishment of the actions required by the existing AD were adequate to prevent uncommanded nose-down pitch at certain flap settings during icing conditions in the interim until the modification required by this final rule could be accomplished. However, as noted in the proposal, accomplishment of the modification of the ice protection system improves the ice protection of the horizontal stabilizer. Since such a modification is nowavailable for Model 400T airplanes, the FAA has determined that it is appropriate to add a provision for accomplishment of this modification in this final rule. Paragraph (b)(2) of this AD has been revised accordingly. \n\nRequest to Revise the Cost Impact Paragraph \n\tThis same commenter requests that the FAA revise the number of airplanes specified in the Cost Impact paragraph of the proposal to reflect the actual number of airplanes affected by the proposal. The manufacturer notes that there are currently 360 Raytheon (Beech) Model 400, 400A, and 400T airplanes and MU-300-10 airplanes in the worldwide fleet, 64 Model 400 and MU-300-10 airplanes, 107 Model 400A airplanes, and 189 Model 400T airplanes of U.S. Registry. \n\n\tThe FAA concurs with revising the number of airplanes, and the resulting revision of the cost estimate figures involved. However, since the submittal of the manufacturer's initial comments, the manufacturer has updated the correct number of airplanes again. TheFAA has revised the Cost Impact paragraph of the final rule to specify the latest number of airplanes and the consequent revision of the cost estimate figures. \n\nRequest to Revise the Description of the Ice Protection System \n\tThis same commenter also requests that the description of the ice protection specified in the Summary section of the proposed rule be clarified from "horizontal stabilizer ice protection system ." to specify "airplane ice protection system." The manufacturer states that the proposal refers not only to the horizontal stabilizer ice protection, but pertains to the entire airplane's ice protection system. \n\n\tThe FAA acknowledges that the actions specified in the final rule apply to the entire "airplane" ice protection system, although the modification applies primarily to the horizontal stabilizer ice protection system. The FAA has revised the final rule to reflect the description of the modification as the "airplane ice protection system." \n\nAdditional Change to the Final Rule \n\tAs discussed previously, the FAA has reviewed and approved Raytheon Service Instructions No. T-1A-0064 (undated), which describes procedures for modification of the airplane ice protection system. The FAA has added the service instruction as the appropriate source of service information for accomplishment of the requirements of paragraph (b)(2) of this final rule. \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 388 Raytheon (Beech) Model 400, 400A, 400T, and MU-300-10 airplanes of the affected design in the worldwide fleet. \n\n\tThe FAA estimates that 64 Model 400 and MU-300-10 airplanes, 90 Model 400Aairplanes, and 183 Model 400T airplanes of U.S. registry will be affected by this AD. \n\n\tThe actions that are currently required by AD 94-25-10 (AFM revision) take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact on U.S. operators of the actions currently required is estimated to be $20,220, or $60 per airplane. \n\n\tFor Model 400, 400A, and MU-300-10 airplanes: The modification that is required by this AD will take approximately 320 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost between $37,000 and $45,000 per airplane. Based on these figures, the cost impact on the requirements of this AD for U.S. operators of those airplanes is estimated to be between $8,654,800 and $9,886,800, or between $56,200 and $64,200 per airplane. \n\n\tFor Model 400T airplanes: The modification required by this AD will take approximately 360 work hours per airplane to accomplish, at an average rate of $60 per work hour. Required parts will cost approximately $40,000 per airplane. Based on these figures, the cost impact of the AD on U.S. operators of those airplanes is estimated to be $11,272,800, or $61,600 per airplane. However, the FAA has been advised that, for Model 400T airplanes, the manufacturer has committed previously to its customers that it will bear the cost of replacement parts and labor costs necessary to accomplish the replacement of those parts. Therefore, the future economic cost impact of this rule on U.S. operators may be less than the cost impact figure indicated above. \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. \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\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."List of Subjects in 14 CFR Part 39 \n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\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: \n\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\n§ 39.13 (Amended) \n\t2. Section 39.13 is amended by removing amendment 39-9094 (59 FR 64112, December 13, 1994), and by adding the following new airworthiness directive (AD), amendment 39-11372, to read as follows: