The FAA has received reports that Pratt & Whitney Model PW4000 series engines with certain early-production fan blades (Phase 0/1, FB2B or FB2T) installed on Boeing Model 747-400, 747-400F, 767-200, and 767-300 series airplanes do not produce the amount of thrust indicated in the Airplane Flight Manual (AFM). This thrust shortfall is due to erosion of the fan blade's leading edge. The flight crew has no indication of this shortfall in thrust. This condition results in reduced acceleration and climb performance relative to performance data in the AFM, which, if not corrected, could result in an overrun of the runway or impact with an obstacle or terrain. \n\nExplanation of Relevant Service Information \nThe FAA has reviewed and approved Boeing Telex M-7200-00-02672, dated November 1, 2000, including two attachments titled, "Performance for Operation of PW4000 Series Engines with FB2B or FB2T Fans Installed(,) 747-400," and "Performance for Operation of PW4000 Series Engines with FB2B or FB2T Fans Installed(,) 767-200/767-300," both dated November 1, 2000. The telex and its attachments contain performance adjustments for the AFM for Model 747-400, 747-400F, 767-200, and 767-300 series airplanes equipped with one or more Pratt & Whitney Model PW4000 series engines with early production fan blades. Inclusion of these performance adjustments in the AFM addresses the unsafe condition associated with the shortfall in thrust caused by the early production fan blades. \n\nExplanation of the Requirements of the Rule \nSince an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design, this AD is being issued to prevent reduced acceleration and climb performance relative to performance data in the AFM, which could result in runway overruns or impact with obstacles or terrain. This AD requires accomplishment of the actions specified in the telex and attachments described previously, except as discussed below. \n\nDifferences Between Telex and This AD \nOperators should note that, although the telex states that the airplane manufacturer was advised that the FAA would recommend a compliance time of 45 days after the effective date of the AD for the actions in the telex, paragraph (a) of this AD actually requires revising the AFM within 30 days after the effective date of this AD. In developing an appropriate compliance time for this AD, the FAA considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to revise the AFM. In light of all of these factors, the FAA finds a 30-day compliance time for completing the required actions to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety. \n\n\tOperators also should note that thisAD applies to all Boeing Model 747-400, 747-400F, 767-200, and 767-300 series airplanes equipped with Pratt & Whitney Model PW4000 series engines. For airplanes that have current-production fan blades (Phase 3, FB2C) installed on all engines, the performance adjustments in the attachments to the telex referenced above are not applicable. However, this AD requires revision of the AFM for all airplanes to address the potential for future installation of early production fan blades (Phase 0/1, FB2B or FB2T). Note 1 is included in this AD to clarify this point. \n\nDetermination of Rule's Effective Date \nSince a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. \n\nComments Invited \nAlthough this action is in the form of a final rule that involves requirements affecting flight safety and,thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed. \n\n\tSubmit comments using the following format:\n--\tOrganize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.\n-- \tFor each issue, state what specific change to the AD is being requested. \n--\tInclude justification (e.g., reasons or data) for each request. \n\n\tComments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket. \n\n\tCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 2000-NM-391-AD." The postcard will be date stamped and returned to the commenter. \n\nRegulatory Impact \nThe 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\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39 \nAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \nAccordingly, 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\n1. The authority citation for part 39 continues to read as follows: 2. \n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n2. Section 39.13 is amended by adding the following new airworthiness directive: