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Proposed Rule

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

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Federal Aviation Administration, DOT.


Notice of proposed rulemaking (NPRM).


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.


Comments must be received by November 25, 2002.


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: Comments may be inspected at the Start Printed Page 59795Office of the Regional Counsel between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays.

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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.

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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.


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.

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List of Subjects in 14 CFR Part 39

  • Air transportation
  • Aircraft
  • Aviation safety
  • Safety
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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:

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1. The authority citation for part 39 continues to read as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701.

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2. Section 39.13 is amended by removing Amendment 39-12793 (67 FR 43227, June 27, 2002), and by adding a new airworthiness directive (AD), to read as follows:

MD Helicopters, Inc.: Docket No. 2001-SW-40-AD. Revises AD 2002-13-05, Amendment 39-12793.

Applicability: The following MD Helicopters, Inc. helicopter models, certificated in any category:

Helicopter modelWithModified in accordance with
(1) 369D, 369E, 369F, 369FFTailboom, serial number (S/N) 5001-5032Aerometals Supplemental Type Certificate (STC) SH5055NM.
(2) 369D and 369ETail Rotor Gearbox Attach BoltsAerometals STC SH4801NM.
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Note 1:

This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise 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 request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent loss of the tail rotor gearbox due to attaching bolts of inadequate grip length and subsequent loss of control of the helicopter, accomplish the following:

(a) Within 25 hours time-in-service (TIS):

(1) For each tail rotor gearbox attaching bolt (bolt):

(i) Determine the part number (P/N).

(ii) If the P/N cannot be determined or if the bolt is not P/N NAS1304-26, before further flight, replace the bolt with bolt, P/N NAS1304-26.

(iii) Torque the bolt to 100-110 in-lbs and apply a slippage mark.

(2) Remove the tailboom control rod and determine the number of bolt threads protruding from each nutplate on the internal surface of the aft tailboom frame casting, P/N 369D23503, as shown in Figure 1 of this AD. At least one thread must protrude. If more than four threads protrude, add an additional washer, P/N AN960D416, under the bolt head. Torque the bolt to 100-110 in-lbs, and reapply a slippage mark. See Figure 1:

(b) Between 2 and 10 hours TIS after accomplishing the requirements of paragraph (a) of this AD, inspect the torque on each bolt by applying 100 in-lbs. If any bolt movement occurs, retorque the bolt to 100-110 in-lbs. Reapply a slippage mark to the bolt regardless of the outcome of the torque test. Reinspect the torque between 2 and 10 hours TIS thereafter until no bolt movement occurs.

Note 2:

Aerometals Service Bulletin SB-001, dated August 3, 2000, pertains to the subject of this AD.

(c) 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 (LAACO), FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, LAACO.

Note 3:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the LAACO.

(d) Special flight permits will not be issued.

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Issued in Fort Worth, Texas, on September 13, 2002.

Eric D. Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

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BILLING CODE 4910-13-CStart Printed Page 59797

[FR Doc. 02-24182 Filed 9-23-02; 8:45 am]