AD 2001-25-02

This amendment adopts a new airworthiness directive (AD) for Enstrom Helicopter Corporation (EHC) Model TH-28 and 480 helicopters. This AD requires 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 AD 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 this 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.

Final rule.

2001-25-02 Enstrom Helicopter Corporation: Amendment 39-12554. 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 proposedactions 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.

(e) This amendment becomes effective on January 15, 2002.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD for EHC Model TH-28 and 480 helicopters was published in the Federal Register on September 18, 2001 (66 FR 48102). That action proposed 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. Also proposed was replacing hub plates, P/N 28-14280-1 and 28-14281-1, having 5000 or more hours TIS with airworthy hub plates.

Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposal or the FAA's determination of the cost to the public. The FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

The FAA estimates that 4 helicopters of U.S. registry will be affected by this AD, that it will 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 will 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 this 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 adopted herein will 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 final rule does not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

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

Sec. 39.13 [Amended]

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