[Federal Register Volume 66, Number 181 (Tuesday, September 18, 2001)]
[Proposed Rules]
[Pages 48102-48103]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-23250]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-SW-27-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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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: [email protected]. 
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: 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.

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

[[Page 48103]]

plates, 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.

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.


Sec. 39.13  [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.

    Issued in Fort Worth, Texas, on September 6, 2001.
David A. Downey,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 01-23250 Filed 9-17-01; 8:45 am]
BILLING CODE 4910-13-U