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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-SW-16-AD 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

This document proposes adopting a new airworthiness directive (AD) for Bell Helicopter Textron, Inc. (BHTI) Model 204B helicopters. The AD would require replacing any main rotor mast assembly (mast), part number (P/N) 204-011-450-001, within 25 hours time-in-service (TIS). This proposal is prompted by the crash of a restricted category Model UH-1B helicopter due to failure of a mast, P/N 204-011-450-001. The same mast P/N is used on the Model 204B helicopters. The actions specified by the proposed AD are intended to prevent failure of the mast and subsequent loss of control of the helicopter. 

# DATES:

Comments must be received on or before December 1, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Regional Counsel, Southwest Region, Attention: Rules Docket No. 2000-SW-16-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:

Michael Kohner, Aviation Safety Engineer, FAA, Rotorcraft Directorate, Rotorcraft Certification Office, Fort Worth, Texas 76193-0170, telephone (817) 222-5447, fax (817) 222-5783. 

# 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 notice 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 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket No. 2000-SW-16-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. 2000-SW-16-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137. 

## Discussion 

This document proposes adopting a new AD for BHTI Model 204B helicopters. The AD would require replacing any mast, P/N 204-011-450-001, within 25 hours time-in-service (TIS). This proposal is prompted by the crash of a restricted category Model UH-1B helicopter due to failure of a mast, P/N 204-011-450-001, as a result of an undetected fatigue crack in the stabilizer bar damper spline. Metallurgical examination of the failed part by the National Transportation Safety Board (NTSB) Materials Laboratory revealed fatigue cracking adjacent to the upper groove on the stabilizer bar damper spline. Several other cracks were noted in the same area during visual examination. The mast was reported to have accumulated 4006 hours TIS. The accident investigation also revealed that the U. S. Army removed the masts, P/N 204-011-450-001 and -005, from service in July 1984. 

The FAA issued AD 2000-15-21 on August 1, 2000 (65 FR 48605, August 9, 2000), requiring removal of the mast, P/N 204-011-450-001 and -005, from service on former U.S. military restricted category helicopters. Because the same P/N mast is used on the Bell Model 204B helicopters, this AD proposes to remove the mast, P/N 204-011-450-001, from service on these model helicopters as well. The actions specified by the proposed AD are intended to prevent failure of the mast. This condition, if not corrected, could result in loss of control of the helicopter. 

We have identified an unsafe condition that is likely to exist or develop on other BHTI Model helicopters of the same type design. The proposed AD would require replacing any mast, P/N 204-011-450-001, which would no longer be eligible for installation on any helicopter. 

We estimate that 15 helicopters of U.S. registry would be affected by this proposed AD, that it would take approximately 10 work hours per helicopter to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Required parts would cost approximately $8,862 per helicopter. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $141,930. 

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:                           ( print page 58682)    

# 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 

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

**Bell Helicopter Textron, Inc.:**                                 Docket No. 2000-SW-16-AD.                             

*Applicability:*                                 Model 204B helicopters with main rotor mast assembly, part number (P/N) 204-011-450-001, 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 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 (b) 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 within 25 hours time-in-service, unless accomplished previously.                             

To prevent failure of the main rotor mast assembly (mast) and subsequent loss of control of the helicopter, accomplish the following: 

(a) Remove any mast, P/N 204-011-450-001, from service and replace it with an airworthy mast. Accomplishing the requirement of this paragraph constitutes terminating action for the requirements of this AD. P/N 204-011-450-001 is not eligible for installation on any helicopter. 

(b) 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, Rotorcraft Certification Office, Rotorcraft Directorate, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Rotorcraft Certification Office. 

# Note 2:

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

(c) 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. 

Issued in Fort Worth, Texas, on September 25, 2000. 

Eric Bries, 

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service. 

[FR Doc. 00-25154 Filed 9-29-00; 8:45 am] 

BILLING CODE 4910-13-P