On September 28, 1998, the FAA issued Priority Letter AD 98-21-09, applicable to RHC Model R22 helicopters, which requires installing fuel tank vent tube(s), with modified attachment to the mast tube, if not previously accomplished; installing a spring into the flexible tube leading to the main fuel tank; and installing a spring into the flexible tube leading to the auxiliary fuel tank, if an auxiliary fuel tank is installed. That action was prompted by an incident in which a hard landing resulted from an uncommanded engine shutdown. The pilot reported that the fuel quantity gauges indicated fuel consumption from the auxiliary fuel tank only, with the main fuel tank indication remaining at or near full. When the auxiliary fuel tank quantity gauge reached empty, the engine misfired and then stopped. An inspection revealed a kink in the flexible vent tube connecting the rigid vent tube to the main fuel tank. Two similar incidents have occurred with this single vent design. This condition, if not corrected, could result in fuel starvation, loss of engine power, and a subsequent forced landing. \n\n\tThe FAA has reviewed RHC R22 Service Bulletin SB-83 dated March 4, 1997 (SB-83), which describes procedures for modifying attachment of the fuel tank vent(s); and RHC R22 Service Bulletin SB-84 dated September 8, 1998 (SB-84), which describes procedures for installing springs in the vent tubes to prevent kinks. RHC kit instructions KI-118-1 R22 Fuel Tank Vent Upgrade For Ships Without Auxiliary Tank, dated March 4, 1997, and RHC KI-118-2 R22 Fuel Tank Vent Upgrade For Ships With Auxiliary Tank, dated April 29, 1997, which describe procedures for installing fuel tank vent tube(s), part number (P/N) A731-3, are attached to SB-83. RHC kit instructions KI-140 R22 Fuel Tank Vent Upgrade For Fuel Tanks With Single Vent, dated September 3, 1998, which describe procedures for installing springs into the flexible tube leading to the main fueltank, and, if an auxiliary fuel tank is installed, into the flexible tube leading to the auxiliary fuel tank, are attached to SB-84. \n\n\tSince the unsafe condition described is likely to exist or develop on other RHC Model R22 helicopters of the same type design, the FAA issued priority letter AD 98-21-09 to prevent fuel starvation, loss of engine power, and a subsequent forced landing. The AD requires, within 25 hours time-in-service (TIS) or 30 calendar days after the effective date of this AD, whichever occurs first, installing fuel tank vent tube(s), P/N A731-3, with modified attachment to the mast tube, if not previously accomplished; installing a spring, P/N B408-2, into the flexible tube leading to the main fuel tank; and installing a spring, P/N B408-1, into the flexible tube leading to the auxiliary fuel tank, if an auxiliary fuel tank is installed. The short compliance time involved is required because the previously described critical unsafe condition can adversely affectthe controllability of the helicopter. Therefore, the installations are 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 September 28, 1998, to all known U.S. owners and operators of RHC Model R22 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 only change to the priority letter in this published version of this AD is that the reference in NOTE 1 to the alternative methods of compliance is corrected from paragraph "(d)" to paragraph "(c)". \n\n\tThe FAA estimates that 700 helicopters of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per helicopter to accomplish the required actions, and the average labor rate is $60 per work hour. Required parts will cost approximately $65 for each helicopter without an auxiliary fuel tank installed or $105 for each helicopter with an auxiliary fuel tank installed. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $225 per helicopter for helicopters with an auxiliary fuel tank installed, or $185 per helicopter for helicopters without an auxiliary fuel tank installed. \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 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 No. 98-SW-45-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 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: \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: