The FAA has found that the Operational Limits specified in the Limitations Section of the Airplane Flight Manual (AFM) for McDonnell Douglas Model MD-11 series airplanes equipped with Pratt & Whitney Model PW4400 series engines do not adequately list the performance correction sections in the AFM. Section 4B, the applicable performance correction section for Model MD-11 series airplanes with Pratt & Whitney Model PW4462 engines, is not listed. Model PW4462 engines are rated for higher thrust than other Model PW4400 series engines. Omitting the reference to Section 4B in the required performance correction paragraph of the Operational Limits subsection in the Limitations Section of the AFM could cause the flight crew to be incorrectly informed about limitations in airplane performance. \n\n\tAlso, the FAA has received reports that Pratt & Whitney Model PW4400 series engines with certain early-production fan blades (Phase 0/1, FB2B), as installed on certain McDonnell Douglas Model MD-11 series airplanes, do not produce the amount of thrust indicated in the AFM. This thrust shortfall is due to erosion of the fan blade's leading edge. This condition causes a thrust shortfall of 2.5 percent at high-thrust settings. The flight crew has no indication of this shortfall in thrust. This condition could result in reduced acceleration and climb performance relative to performance data in the AFM, which, if not corrected, could lead to the airplane overrunning the end of the runway during takeoff or landing, or impacting obstacles or terrain. \n\nExplanation of the Requirements of the Rule \n\tSince 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 ensure that the flight crew is informed of applicable limitations in airplane performance, and to prevent reduced acceleration and climb performance relative to performance data in the AFM, which could resultin the airplane overrunning the end of the runway during takeoff or landing, or impacting obstacles or terrain. This AD requires revising the Limitations Section of the AFM, and, for certain airplanes, Section 4A or 4B of the Performance Section of the AFM, to advise the flight crew of applicable operational limits. \n\nInterim Action \n\tThis is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking. \n\nDetermination of Rule's Effective Date \n\tSince 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 \n\tAlthough 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 invitedon 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\nOrganize 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\nFor each issue, state what specific change to the AD is being requested. \n\nInclude justification (e.g., reasonsor 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 2001-NM-43-AD." The postcard will be date stamped and returned to the commenter \n\nRegulatory Impact \n\tThe 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 \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 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: Authority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n\t2. Section 39.13 is amended by adding the following new airworthiness directive: