Airworthiness Directives; MD Helicopters, Inc. Model 369D, 369E, 369F, and 369FF Helicopters

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes to revise an existing airworthiness directive (AD) for the specified MD Helicopters, Inc. (MDHI) helicopters. That AD currently requires identifying the part number (P/N) of the bolts that attach the tail rotor gearbox to the tailboom and replacing any bolt of inadequate grip length with an airworthy bolt. That AD also requires adding an additional washer if more than four threads protrude from the nutplate. This action would contain the same requirements as the existing AD but would reduce the applicability to only certain tailboom serial numbers and parts modified in accordance with either Supplemental Type Certificate (STC) SH5055NM or SH4801NM. The action would also correct a typographical error and clarify that a slippage mark needs to be reapplied to each bolt regardless of the outcome of the required torque test. This proposal is prompted by the need to reduce the applicability and to correct and clarify other portions of the existing AD. The actions specified by the proposed AD are intended to prevent loss of a tail rotor gearbox due to bolts of inadequate grip length and subsequent loss of control of the helicopter.

DATES:

Comments must be received by November 25, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Regional Counsel, Southwest Region, Attention: Rules Docket No. 2001-SW-40-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137. You may also send comments electronically to the Rules Docket at the following address: 9-asw-adcomments@faa.gov. Comments may be inspected at the Office of the Regional Counsel between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT:

John Cecil, Aviation Safety Engineer, FAA, Los Angeles Aircraft Certification Office, Airframe Branch, 3960 Paramount Blvd., Lakewood, California 90712-4137, telephone (562) 627-5228, fax (562) 627-5210.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this document may be changed in light of the comments received.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their mailed comments submitted in response to this proposal must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket No. 2001-SW-40-AD.” The postcard will be date stamped and returned to the commenter.

Discussion

On June 18, 2002, the FAA issued AD 2002-13-05, Amendment 39-12793 (67 FR 43227, June 27, 2002), for specified MDHI model helicopters with a tailboom modified according to either Aerometals STC SH5055NM or SH4801NM. These STC's were formerly owned by Yehnert Helicopters, Inc. That action was prompted by the discovery that the maintenance instructions supplied to installers of STC SH5055NM and SH4801NM incorrectly specified the tail rotor gearbox attaching bolt as S/B NAS 1304-25, which has an inadequate grip length. That condition, if not corrected, could result in loss of a tail rotor gearbox and subsequent loss of control of the helicopter.

Before its issuance, the FAA solicited comments to the proposed AD by a Notice of Proposed Rulemaking that was published in the Federal Register on December 27, 2001 (66 FR 66821). One commenter stated that the applicability of the AD should be limited to certain part-numbered tailbooms with serial number (S/N) 5001-5032 specified in the FAA-approved Aerometals Service Bulletin. We did not agree with the commenter and, except for minor editorial changes, issued the AD as it had been proposed.

Since the issuance of AD 2002-13-05, the FAA has determined that we inappropriately responded to the comment and that the commenter's concern was valid. We are now proposing to reduce the applicability of AD 2002-13-05 to include only certain tailboom serial numbers and parts that are modified in accordance with either STC SH5055NM or SH4801NM. We have also found that the P/N for washer, P/N AN960D416, was incorrect where referenced in Figure 1 and that clarification that a slippage mark needs to be reapplied to each bolt regardless of the outcome of the required torque test is necessary.

The unsafe condition described previously is likely to exist or develop on other helicopters of these same type designs. Therefore, the actions required by AD 2002-13-05 will remain the same, but this proposed AD would reduce the applicability of AD 2002-13-05, correct the P/N for the washer, and clarify that a slippage mark must be reapplied to each bolt regardless of the outcome of the required torque test.

The FAA estimates that this proposed AD would affect 500 helicopters of U.S. registry. It would take approximately 1/2 work hour per helicopter to determine whether a helicopter has been modified by either STC and 1 work hour to inspect and replace the bolts for each of approximately 40 helicopters modified by the STC's. The average labor rate is $60 per work hour. Required parts would cost approximately $40 per helicopter. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $19,000.

The regulations proposed herein would not have a substantial direct effect 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, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this proposed regulation (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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.