AD 98-21-12

This amendment adopts a new AD that is applicable to MDHS Model 369D, 369E, 369FF, 500N, AH-6, and MH-6 helicopters. This action requires a visual inspection of the overrunning clutch retainer, part number (P/N) 369F5460-1, carrier, P/N 369F5461-1, housing, P/N 369F5451-1, and pin, P/N MS16556-801, for wear due to spinning of the bearing retainer and the outer race of the bearing. This amendment is prompted by a report of an operator that experienced inflight vibrations. Subsequent investigation revealed that the bearing retainer and the outer race of the bearing were spinning, which led to wear of the bearing carrier and movement of the bearing outer race. Investigations of three other overrunning clutches with the same P/N also indicated there had been spinning of the retainer. This condition, if not corrected, could result in wear on the bearing carrier, which could lead to failure of the overrunning clutch, excessive vibration, wear of other clutch components, and subsequent loss of power to the helicopter rotor drive system.

The FAA has reviewed MDHS Service Information Notice No. DN-190, EN-83, FN-70, NN-011, dated July 25, 1997, which describes procedures for visually inspecting the overrunning clutch retainer, carrier, and pin for clutch or carrier wear, or pin damage, and replacing any unairworthy clutch assembly with an airworthy clutch assembly.

Since an unsafe condition has been identified that is likely to exist or develop on other MDHS Model 369D, 369E, 369FF, 500N, AH-6, and MH-6 helicopters of the same type design, this AD is being issued to detect wear of other clutch components, excessive vibration which could lead to failure of the overrunning clutch, wear on the bearing carrier, and subsequent loss of power to the helicopter rotor drive system. This AD requires visual inspections of the overrunning clutch retainer, carrier, housing, and pin, for wear from spinning of the bearing retainer. The actions are required to be accomplished in accordance with the service information notice 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, inspections of the overrunning clutch components is required within 25 hours time-in-service (TIS) and 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 2,200 helicopters of U.S. registry will be affected by this AD, that it will take approximately 2 work hours to accomplish the inspection and 14 work hours to accomplish either the replacement of components, or replacement of the entire clutch assembly, and that the average labor rate is $60 per work hour. Required parts will cost approximately $1,098 if only components are replaced, or $7690 if the entire clutch assembly is replaced, per helicopter. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $4,527,600 to accomplish one inspection and replace components, or $19,030,000 to accomplish one inspection and replace the entire clutch assembly.

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 forcomments 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. 97-SW-47-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: