01-31556. 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 the adoption of a new airworthiness directive (AD) for MD Helicopters, Inc. Model 369D, 369E, 369F, and 369FF helicopters with a tailboom modified according to Aerometals supplemental type certificate (STC) SH5055NM or SH4801NM. The AD would require an inspection to identify 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. This AD would also require determining the number of bolt threads protruding from each nutplate and adding an additional washer if more than four threads protrude. This proposal is prompted by the discovery that bolts of inadequate grip length were specified to attach the tail rotor gearbox to the tailboom. 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 on or before February 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: [e-mail]. 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 [phone], fax [phone].

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 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.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the 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.

Discussion

This document proposes adopting a new AD for MD Helicopters, Inc. Model 369D, 369E, 369F, and 369FF helicopters with a tailboom modified according to either Aerometals STC SH5055NM or SH4801NM. Yehnert Helicopters, Inc. formerly owned both STCs. This proposal is prompted by the discovery that the maintenance instructions supplied to installers of STCs SH5055NM and SH4801NM incorrectly specified the tail rotor gearbox attaching bolt as P/N NAS6204-25, which has an inadequate grip length. This condition, if not corrected, could result in loss of a tail rotor gearbox and subsequent loss of control of the helicopter.

The FAA has reviewed Aerometals Service Bulletin SB-001, dated August 3, 2000, which describes procedures for verifying that the proper attaching bolts are used to install the tail rotor gearbox to the tailboom.

We have identified an unsafe condition that is likely to exist or develop on other MD Helicopters, Inc. Model 369D, 369E, 369F, and 369FF helicopters of the same type design modified by STC SH5055NM or SH4801NM. Therefore, the proposed AD would require the following:

• Inspect the tail rotor gearbox attach bolts to determine the P/N. Replace any bolt for which a P/N cannot be determined and any bolt that is not P/N NAS1304-26 before further flight. After replacing a bolt, inspect for loosening of the bolt torque at a specified interval. Retorque the bolt, reapply the slippage mark, and reinspect the torque between 2 and 10 hours TIS thereafter.
• 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. At least one thread must protrude. If more than four threads protrude, add an additional washer under the bolt head.

The FAA estimates that this proposed AD would affect 500 helicopters of U.S. registry. The FAA estimates approximately 1/2 work hour would be required to determine whether either STC has been installed. For the estimated 40 helicopters that have been modified by either STC, approximately 1 work hour per helicopter will be required to inspect and replace the bolts. The average labor rate is approximately $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.

§ 39.13

[Amended]

2. Section 39.13 is amended by adding a new airworthiness directive to read as follows:

MD Helicopters, Inc.: Docket No. 2001-SW-40-AD.

Applicability: Model 369D, 369E, 369F, and 369FF helicopters, modified in accordance with Aerometals Supplemental Type Certificate (STC) SH5055NM or SH4801NM, certificated in any category.

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), conduct the following inspections:

(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. 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.

(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. and reapply a slippage mark. 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.

Issued in Fort Worth, Texas, on December 14, 2001.

David A. Downey,

Manager, Rotorcraft Directorate, Aircraft Certification Service.