On August 13, 1999, the FAA issued Emergency Priority Letter AD 99-17-17, applicable to RHC Model R44 helicopters, which requires, prior to further flight, replacing certain yoke assemblies with airworthy yoke assemblies. That action was prompted by an incident in which, during cruise flight, the pilot heard a loud bang and noticed no tail rotor effectivity after entering autorotation. An investigation revealed that the yoke assembly, which connects the main rotor gearbox pinion shaft to the forward flexplate, had failed at a weld joint due to a crack. The cause of the crack is unknown but still under investigation. RHC has identified the manufacturing lots associated with the failed yoke. This condition, if not corrected, could result in failure of the yoke assembly, loss of main and tail rotor drive, and subsequent loss of control of the helicopter.
The FAA has reviewed RHC R44 Service Bulletin SB-35, dated July 26, 1999, which prescribes procedures for identifying the manufacturing lot for each yoke assembly, part number (P/N) C908-1C, and for removing and replacing the yoke assembly.
Since the unsafe condition described is likely to exist or develop on other RHC Model R44 helicopters of the same type design, the FAA issued Emergency Priority Letter AD 99-17-17 to prevent failure of the yoke assembly, which could result in loss of main and tail rotor drive and subsequent loss of control of the helicopter. The AD requires, prior to further flight, replacing the yoke assembly, P/N C908-1C, from Lot Nos. 36B, 37, and 38, with an airworthy yoke assembly from a lot other than 36B, 37, or 38. The actions must be accomplished in accordance with the service bulletin described previously.
The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the structural integrity of the helicopter. Therefore, replacing any yoke assembly, P/N C908-1C, from LotNos. 36B, 37, and 39, is required prior to further flight, and this AD must be issued immediately.
Since 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 August 13, 1999 to all 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.
The FAA estimates that 75 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 $840 per helicopter. Based on these figures, the total costimpact of the AD on U.S. operators is estimated to be $72,000, assuming that the yoke assembly is replaced in each helicopter.
Comments Invited
Although 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.
Comments 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.
Commenters 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-46-AD." The postcard will be date stamped and returned to the commenter.
The 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.
The 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."
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft,Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, 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:
PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: