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Proposed Rule

Airworthiness Directives; Enstrom Helicopter Corporation Model TH-28 and 480 Helicopters

Document Details

Information about this document as published in the Federal Register.

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AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) for Enstrom Helicopter Corporation (EHC) Model TH-28 and 480 helicopters. The AD would require establishing a life limit for certain upper and lower main rotor hub plates of 5000 hours time-in-service (TIS), creating a component history card or equivalent record, and replacing each main rotor hub plate (hub plate) having 5000 or more hours TIS with an airworthy hub plate. This proposal is prompted by a recent reliability-based stress analysis that indicates a 5000-hour TIS life limit should be imposed on certain hub plates. The actions specified by the proposed AD are intended to prevent failure of a hub plate, loss of control of the main rotor, and subsequent loss of control of the helicopter.

DATES:

Comments must be received on or before November 19, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Regional Counsel, Southwest Region, Attention: Rules Docket No. 2001-SW-27-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.

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FOR FURTHER INFORMATION CONTACT:

Joseph McGarvey, Fatigue Specialist, FAA, Chicago Aircraft Certification Office, Airframe and Administrative Branch, 2300 East Devon Ave., Des Plaines, Illinois 60018, telephone (847) 294-7136, fax (847) 294-7834.

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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-27-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-27-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.

Discussion

This document proposes the adoption of a new AD for EHC Model TH-28 and 480 helicopters. This AD would require establishing a life limit of 5000 hours TIS for both upper and lower hub plates, part number (P/N) 28-14280-1 and 28-14281-1. This proposal is prompted by a recent reliability-based stress analysis of loads, their frequency of occurrence, and fatigue strength data, which showed that a life limit of 5000 hours TIS should be established for hub plates, P/N 28-14280-1 and 28-14281-1. The actions specified by the proposed AD are intended to prevent failure of a hub plate, loss of control of the main rotor, and subsequent loss of control of the helicopter.

We have identified an unsafe condition that is likely to exist or develop on other EHC Model TH-28 and 480 helicopters of the same type designs. Therefore, the proposed AD would require establishing a 5000-hour TIS life limit and creating a component history or equivalent record for hub Start Printed Page 48103plates, P/N 28-14280-1 and 28-14281-1. The proposed AD would also require replacing hub plates, P/N 28-14280-1 and 28-14281-1, having 5000 or more hours TIS with airworthy hub plates.

The FAA estimates that 4 helicopters of U.S. registry would be affected by this proposed AD, that it would take approximately 10 work hours per helicopter to replace the hub plates, and that the average labor rate is $60 per work hour. Creating a component history or equivalent record would take approximately 2 hours. Required parts would cost approximately $5350 to install hub plates, P/N 28-14280-3 and 28-14281-3 and $5000 to install hub plates, P/N 28-14280-5 and 28-14281-5, per helicopter. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $24,280 maximum, assuming that all hub plates are replaced and that hub plates, P/N 28-14280-3 and 28-14281-3, are installed.

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

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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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PART 39—AIRWORTHINESS DIRECTIVES

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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[Amended]

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

Enstrom Helicopter Corporation: Docket No. 2001-SW-27-AD.

Applicability: Model TH-28 and 480 helicopters, with upper hub plate, part number (P/N) 28-14280-1, and lower hub plate, P/N 28-14281-1, 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 (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 failure of a hub plate, loss of control of the main rotor, and subsequent loss of control of the helicopter, accomplish the following:

(a) Within 30 days after the effective date of this AD, for upper hub plate, P/N 28-14280-1, and for lower hub plate, P/N 28-14281-1, create a component history card or equivalent record, and determine the total hours time-in-service (TIS). Thereafter, record the hours TIS for each hub plate and replace each hub plate having 5000 or more hours TIS as follows:

(1) Install hub plates, P/N 28-14280-3 and 28-14281-3, on helicopters with main rotor damper, P/N 28-14375-8.

(2) Install hub plates, P/N 28-14280-5 and 28-14281-5, on helicopters with main rotor damper, P/N 28-14375-10.

(b) This AD revises the Limitations section of the applicable maintenance manual by establishing a life limit of 5000 hours TIS for the upper hub plate, P/N 28-14280-1, and for the lower hub plate, P/N 28-14281-1.

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

Note 2:

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

(d) Special flight permits may be issued in accordance with 14 CFR 21.197 and 21.199 to operate the helicopter to a location where the requirements of this AD can be accomplished.

Start Signature

Issued in Fort Worth, Texas, on September 6, 2001.

David A. Downey,

Manager, Rotorcraft Directorate, Aircraft Certification Service.

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[FR Doc. 01-23250 Filed 9-17-01; 8:45 am]

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