On June 16, 1999, the FAA issued Priority Letter AD 99-13-09, applicable to MDHI Model 369D and E helicopters with fork assembly, part number (P/N) 369D21701-2 installed, which requires, prior to further flight, inspecting each fork assembly, P/N 369D21701-2, for the presence of ridges on the arms and, if no ridges are present, conducting a dye-penetrant and visual inspection for cracks. If a crack is found, the fork assembly must be replaced with an airworthy fork assembly that has ridges. This AD also requires a repetitive visual inspection at intervals not to exceed 50 hours TIS of those fork assemblies without ridges that are currently installed but for which the initial visual and dye-penetrant inspection did not uncover a crack and removing and replacing, if necessary, each unairworthy fork assembly with an airworthy fork assembly before further flight. That action was prompted by reports from the manufacturer of the discovery of a discrepant part. During the manufacturing process, an unknown number of certain fork assemblies were incorrectly machined in critical areas after the shot-peening process. The two ridges on each of the arms of the fork assemblies were incorrectly machined off. This condition, if not corrected, could result in failure of certain fork assemblies, which could cause loss of a tail rotor blade and subsequent loss of control of the helicopter. \n\n\tSince the unsafe condition described is likely to exist or develop on other MDHI Model 369D and E helicopters of the same type design, the FAA issued Priority Letter AD 99-13-09 to prevent failure of the fork assembly which can result in loss of a tail rotor blade and subsequent loss of control of the helicopter. The AD requires, prior to further flight, inspecting and replacing, if necessary, the fork assembly, P/N 369D21701-21, with an airworthy fork assembly. This AD also requires a repetitive inspection of P/N 369D21701-21 without ridges, at intervals not to exceed 50 hours TIS and removing and replacing, if necessary, each unairworthy fork assembly with an airworthy fork assembly before further flight. The actions are required to be accomplished in the area defined in Figure 1, Sheet 2 of 2 of this AD. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the structural integrity of the helicopter. Therefore, inspecting and replacing, if necessary, the fork assembly, P/N 369D21701-21, with an airworthy fork assembly is required prior to further flight, and this AD must be issued immediately. \n\n\tSince it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual letters issued on June 16, 1999 to all known U.S. owners and operators of MDHI Model 369D and E helicopters. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective to all persons. \n\n\tThe FAA estimates that 24 helicopters of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per helicopter to perform the initial inspection and 1 work hour per helicopter for each repetitive inspection. Replacing a fork assembly, if necessary, will take approximately 5 work hours. The average labor rate is $60 per work hour. The manufacturer states that there will be no parts cost since the required parts are covered under the manufacturer's warranty. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $20,880; assuming $2,880 for the initial inspection of the entire fleet, $14,400 for 10 repetitive inspections for the entire fleet, and $3,600 to replace 12 fork assemblies. \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 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 should 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\tComments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a needto 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 No. 99-SW-40-AD." The postcard will be date stamped and returned to the commenter. \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\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 AviationAdministration 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: \n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n\t2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: