AD 98-21-12 ACTIVE

This amendment adopts a new airworthiness directive (AD) that is applicable to McDonnell Douglas Helicopter Systems (MDHS) Model 369D, 369E, 369FF, 500N, AH-6 and MH-6 helicopters. This action requires visual inspections of the overrunning clutch retainer, carrier, housing, and pin for wear from spinning of the bearing outer race. This amendment is prompted by a report of inflight vibrations and subsequent investigations of three other overrunning clutches, which indicated wear of the bearing carrier due to spinning of the bearing outer race. The actions specified in this AD are intended 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.

Final rule; request for comments

98-21-12 MCDONNELL DOUGLAS HELICOPTER SYSTEMS: Amendment 39-10820. Docket No. 97-SW-47-AD.

Applicability: Model 369D, 369E, 369FF, 500N, AH-6, and MH-6 helicopters, with overrunning clutch assembly, part number (P/N) 369F5450-501, installed, certificated in any category.

NOTE 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (d) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changedconfiguration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any helicopter from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

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, accomplish the following:

(a) Visually inspect the overrunning clutch retainer, P/N 369F5460-1, carrier, P/N 369F5461-1, housing, P/N 369F5451-1, and pin, P/N MS16556-801, for clutch or carrier wear or pin damage in accordance with the Accomplishment Instructions in McDonnell Douglas Helicopter Systems Service Information Notice No. DN-190, EN-83, FN-70, NN-011, dated July 25, 1997. For helicopters with a clutch assembly having less than 100 hours time-in-service (TIS), conduct the visual inspection beforeor upon reaching 100 hours TIS. For helicopters with a clutch assembly having 100 or more hours TIS, conduct the visual inspection within 25 hours TIS.

(b) Repeat the inspection required by paragraph (a) at intervals not to exceed 100 hours TIS.

(c) If the inspections specified in paragraph (a) or (b) reveal wear or damage to components, replace those components with airworthy components prior to further flight.

(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Los Angeles Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Los Angeles Aircraft Certification Office.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles Aircraft Certification Office.

(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the helicopter to a location where the requirements of this AD can be accomplished.

(f) The inspections shall be done in accordance with McDonnell Douglas Helicopter Systems Service Information Notice No. DN-190, EN-83, FN-70, NN-011, dated July 25, 1997. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from McDonnell Douglas Helicopter Systems, Field Service Department, 5000 E. McDowell Road, Mesa, Arizona, telephone (800) 388-3378, fax (602) 891-6782. Copies may be inspected at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.(g) This amendment becomes effective on October 22, 1998.

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:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Regional
Counsel, Southwest Region, Attention: Rules Docket No. 97-SW-47-AD, 2601 Meacham Blvd., Room 663, Fort Worth,
Texas 76137.
The service information referenced in this AD may be obtained from McDonnell Douglas Helicopter Systems, Field Service Department, 5000 E. McDowell Road, Mesa, Arizona, telephone (800) 388-3378, fax (602) 891-6782. This
information may be examined at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd.,
Room 663, Fort Worth, Texas 76137; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700,
Washington, DC.

Mr. Bruce Conze, Aerospace Engineer, FAA, Los Angeles Aircraft
Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712, telephone (562) 627-5261, fax
(562) 627-5210.