AD 99-04-12

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to MDHS Model 369D, 369E, 369FF, 369H, MD500N, and MD600N helicopters was published in the Federal Register on May 15, 1998 (63 FR 27011). That action proposed to require a one-time visual inspection of certain input shaft coupling assemblies for pitting.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

One commenter states that the addition of a calendar period to supplement the time-in-service compliance time is necessary to account for the effects of corrosion which caused the internal spline pitting. The FAA does not concur for the following reasons:

The original corrosion occurred during the manufacturing process due to exposure of unprotected machined parts and porosity in the material. The corrosion was subsequently removed in normal processing and parts coated with dry lube. The corrosion is not a result of time-in-service.

After examining parts returned from the field, there is no evidence suggesting that the original corrosion damage increases with time.

The same commenter also states that there are no guidelines or references to Boeing instructions, service bulletins, or manuals given to strip the input shaft coupling assembly and perform the visual inspection. The FAA does not concur; Note 2 states that Boeing Service Bulletin SB369H-240, SB369E-085, SB500N-013, SB369D-192, SB369F-072, SB600N-003, dated September 26, 1997, pertains to the subject of the AD. No additional guidelines for stripping shaft coupling assembly and performing the visual inspection are deemed necessary because the corrosion on the input shaft coupling assemblies is obvious and easily discernible with the naked eye without stripping the shaft coupling assembly.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

The FAA estimates that 82 helicopters of U.S. registry will be affected by this AD, that it will take approximately 3 work hours per helicopter to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $638 per coupling assembly. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $67,076 if the coupling assembly is replaced in all 82 helicopters.

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.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the FAA, Office of the Regional Counsel, Southwest Region, Attention: Rules Docket No. 97-SW-61-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.

List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment Accordingly, pursuant to the authority delegated to me by theAdministrator, 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: