On October 22, 1998, the FAA issued priority letter AD 98-22-16, applicable to RHC Model R44 helicopters, which requires inspecting each main rotor blade for cracks every 5 hours time-in-service (TIS) until each main rotor blade is replaced with a redesigned main rotor blade. The main rotor blade must be replaced prior to further flight after November 15, 1998. The AD was prompted by an incident in which a pilot heard a loud noise and felt severe vibrations while hovering, resulting in a forced landing. Upon inspection, a crack was found in a main rotor blade. The crack started at the mid-span inboard trim tab, ran chordwise to the spar, and turned along the spar for about an inch. The crack originated from a hole in the main rotor blade skin. Subsequent investigations revealed that the manufacturing process utilized to drill the holes in the main rotor blade skin can allow a fatigue crack to originate at these holes and propagate in the skin. That condition, if not corrected, could result in failure of a main rotor blade and subsequent loss of control of the helicopter. \n\n\tThis AD supersedes AD 98-12-19, Amendment 39-10712 (63 FR 43299, August 13, 1998), that required the same inspections as this AD. However, since the issuance of that AD, it has been determined that continued inspections are inadequate to ensure continued operational safety and that mandatory terminating action is required to permanently resolve this unsafe condition. Therefore, this AD mandates replacement of all the affected main rotor blades prior to further flight after November 15, 1998. \n\n\tThe FAA has reviewed RHC R44 Service Bulletin SB-27B, Revision B, which recommends replacing daily preflight inspections with repetitive inspections at intervals not to exceed 5 hours TIS and clarifies the inspection procedure. The FAA has also reviewed RHC R44 Service Bulletin SB-28, which describes procedures for main rotor blade replacement and recommends replacement by December 31, 1998. Both service bulletins are dated June 18, 1998. \n\n\tRHC has also issued a Safety Alert to all Model R44 helicopter owners, operators, and service centers which states that long term usage of main rotor blades, part number (P/N) C016-1, is not recommended. RHC recently commented to Rules Docket No. 98-SW-25-AD (AD 98-12-19). RHC states that AD 98-12-19 should not permit visual inspections of main rotor blade, P/N C016-1, to continue indefinitely, and requests that the compliance procedures be modified to require the installation of redesigned main rotor blades, P/N C016-2, to "avoid possible catastrophic failure." The commenter also requests that NOTE 5 reference "Revision B of R44 Service Bulletin 27" for blade inspection and "R44 Service Bulletin 28" for blade replacement. The FAA concurs that as the TIS and total number of repetitive inspections on these main rotor blades increase, so does the possibility for a crack to develop and remain undetected. Based on that re-evaluation, the FAA has determined that the required compliance time for main rotor blade replacement should be earlier than the date stated in RHC R44 Service Bulletin SB-28 in order to ensure public safety. \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other RHC Model R44 helicopters of the same type design, the FAA issued priority letter AD 98-22-16 to require repetitively inspecting both holes on both the upper and lower surfaces of each main rotor blade for cracks until the main rotor blades are replaced with redesigned main rotor blades. The main rotor blades must be replaced prior to further flight after November 15, 1998. \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 October 22, 1998 toall known U.S. owners and operators of RHC Model R44 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 96 helicopters of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per helicopter to perform the inspections and 10 work hours to replace both main rotor blades on each helicopter, and the average labor rate is $60 per work hour. Required parts will cost approximately $3,900 per main rotor blade. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $817,920, assuming one inspection and replacement of both main rotor blades on all helicopters. \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-56-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 removing Amendment 39-10712 (63 FR 43299, August 13, 1998), and by adding a new airworthiness directive (AD), Amendment 39-10874, to read as follows: