This amendment adopts a new AD applicable to BHTI Model 412, 412EP, and 412CF helicopters. This action requires inspecting and measuring each yoke, part number (P/N) 412-010-101-123 or -127, installed on Model 412 and 412EP helicopters, serial numbers (S/N) 33001 through 33213, 34001 through 34036, and 36001 through 36204; and on Model 412CF helicopters, S/N 46400 through 46499. If a yoke measures less than 0.478-inch thickness, this AD requires adding 500 hours TIS to the total time for the component and noting the measurement and the increase in hours TIS on the component history card or equivalent record. This amendment is prompted by a report of an emergency landing due to severe main rotor vibration on a BHTI Model 412 helicopter. Subsequent fatigue analysis indicates that a yoke does not have the anticipated service life when manufactured to less than a 0.478-inch thickness. This condition, if not corrected could result in a fatigue failure of the yoke, loss of a main rotor blade, and subsequent loss of control of the helicopter.
The FAA has reviewed BHTI Service Bulletins 412-98-93 and 412CF-98-5, both dated March 2, 1998 (ASB), which describe procedures for inspecting and measuring certain yokes and imposing a flight-hour penalty of 500 hours TIS for yokes measuring less than 0.478-inch thickness.
Since an unsafe condition has been identified that is likely to exist or develop on other BHTI Model 412, 412EP, and 412CF helicopters of the same type design, this AD is being issued to prevent a fatigue failure of a yoke, loss of a main rotor blade, and subsequent loss of control of the helicopter. This AD requires inspecting and measuring each yoke, P/N 412-010-101-123 and - 127, for thickness. The AD also requires noting on the component history card or equivalent record the thickness measurement and adding 500 hours TIS to the total time of any yoke that measures under 0.478-inch thickness. The actions are required to be accomplished in accordance with the applicable ASB described previously.
The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the controllability of the helicopter. Therefore, to prevent a fatigue failure of the yoke, this AD must be issued immediately.
Since 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.
The FAA estimates that 149 helicopters will be affected by this AD, that it will take approximately 8 work hours to accomplish the measurement of the yoke thickness and to annotate the history card or equivalent component record, and that the average labor rate is $60 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $71,520.
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-55." 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 finalrule 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 AmendmentAccordingly, 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: