[Federal Register Volume 59, Number 119 (Wednesday, June 22, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-15148]


[[Page Unknown]]

[Federal Register: June 22, 1994]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-SW-18-AD]

 

Airworthiness Directives: Sikorsky Aircraft Model S-58 and S-58T 
Series Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to Sikorsky Aircraft Model S-58 and 
S-58T series helicopters. This proposal would require the removal and 
replacement of the transmission main gear box ring gear (ring gear) 
within certain time intervals and would establish a retirement life for 
the ring gear. This proposal is prompted by reports of failures of the 
ring gear due to slow-growth fatigue cracks. The actions specified by 
the proposed AD are intended to prevent failure of the ring gear, 
failure of the main transmission, and subsequent loss of control of the 
helicopter.

DATES: Comments must be received by August 22, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Assistant Chief Counsel, Attention: 
Rules Docket No. 93-SW-18-AD, 2601 Meacham Boulevard, Room 663, Fort 
Worth, Texas 76137. Comments may be inspected at this location between 
9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal 
holidays.
    The service information referenced in the proposed rule may be 
obtained from Sikorsky Aircraft, Commercial Customer Support, 6900 Main 
Street, Stratford, Connecticut 06601-1381. This information may be 
examined at the FAA, Office of the Assistant Chief Counsel, 2601 
Meacham Boulevard, Room 663, Fort Worth, Texas.

FOR FURTHER INFORMATION CONTACT: Mr. Francis X. Walsh, Aerospace 
Engineer, Boston Aircraft Certification Office, FAA, New England 
Region, 12 New England Executive Park, Burlington, Massachusetts 01803-
5299, telephone (617) 238-7158, fax (617) 238-7199.

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, 
specified above, 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, 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 comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 93-SW-18-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 Assistant Chief Counsel, Attention: Rules 
Docket No. 93-SW-18-AD, 2601 Meacham Boulevard, Room 663, Fort Worth, 
Texas 76137.

Discussion

    This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to Sikorsky Aircraft Model S-58 and 
S-58T series helicopters. There have been four failures of the 
transmission main gear box ring gear (ring gear), part number (P/N) 
S1635-20058-2, reported by the manufacturer. The failures were caused 
by a slow-growth fatigue crack in a single tooth on the drive side of 
the ring gear. The ring gear is a critical part in the main 
transmission. Therefore, any cracks in the teeth of the ring gear 
create an unsafe condition. This condition, if not corrected, could 
result in failure of the ring gear, failure of the main transmission, 
and subsequent loss of control of the helicopter.
    The FAA has reviewed and approved Sikorsky Aircraft Alert Service 
Bulletin No. 58B35-32, dated July 6, 1993, that describes procedures 
for removal and replacement of the ring gear, provides a new mandatory 
retirement life for the ring gear, provides for originating a component 
time-in-service record, and provides for marking a permanent serial 
number on zero-time and replacement ring gears as well as ring gears 
removed for servicing.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require removing and replacing the ring gear within 
certain time intervals, establishing a mandatory retirement life of 
2,500 hours' total time-in-service, originating a component service 
record, and marking a serial number on the ring gear, P/N S1635-20058-
2. The actions would be required to be accomplished in accordance with 
the service bulletin described previously.
    The FAA estimates that 125 helicopters of U.S. registry would be 
affected by this proposed AD, that it would take approximately 31.5 
work hours per helicopter to accomplish the proposed actions, and that 
the average labor rate is $55 per work hour. Required parts would cost 
approximately $2,000 per ring gear. Based on these figures, the total 
cost impact of the proposed AD on U.S. operators is estimated to be 
$466,562.
    The regulations proposed herein would not have substantial direct 
effects 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, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    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. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Sikorsky Aircraft: Docket No. 93-SW-18-AD.

    Applicability: Model S-58 and S-58T series helicopters, 
certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the transmission main gear box ring gear 
(ring gear), failure of the main transmission, and subsequent loss 
of control of the helicopter, accomplish the following:
    (a) Within the next 25 hours' time-in-service (TIS) after the 
effective date of this AD, accomplish the following:
    (1) From component records, determine the TIS for the ring gear, 
part number (P/N) S1635-20058-2,
    (i) If the TIS on the ring gear is 2,400 or more hours' on the 
effective date of this AD, replace it with an airworthy serialized 
ring gear within the next 100 hours' TIS.
    (ii) If the TIS on the ring gear is less than 2,400 hours' on 
the effective date of this AD, replace it with an airworthy 
serialized ring gear at or before reaching 2,500 hours' TIS.
    (2) If the TIS on the ring gear cannot be determined, replace it 
in accordance with the time since last overhaul (TSO) as follows:
    (i) If the TSO on the ring gear is 1,150 or more hours' on the 
effective date of this AD, replace it with an airworthy serialized 
ring gear within the next 100 hours' TIS.
    (ii) If the TSO on the ring gear is less than 1,150 hours' on 
the effective date of this AD, replace with an airworthy serialized 
ring gear at or before reaching 1,250 hours' TSO.
    (3) Create a component log and a serial number and apply the 
serial number to the ring gear between the ring gear flanges in 
accordance with Paragraph B of the Accomplishment Instructions of 
Sikorsky Aircraft Alert Service No. 58B35-32 (ASB 58B35-32), dated 
July 6, 1993.
    (b) Create a component log and a serial number for replacement 
ring gears and apply the serial number to the ring gear between the 
ring gear flanges in accordance with Paragraph B of the 
Accomplishment Instructions of the ASB 58B35-32, dated July 6, 1993, 
prior to installing a replacement ring gear on the helicopter.
    (c) This AD establishes a retirement life of 2,500 hours' TIS 
for the ring gear. However, ring gears with 2,400 or more hours' TIS 
or, if the TIS cannot be determined, 1,150 or more hours' TSO on the 
effective date of this AD, need not be retired until on or before 
the accumulation of an additional 100 hours' TIS.
    (d) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used when approved by the Manager, Boston Aircraft Certification 
Office, FAA. Operators shall submit their requests through an FAA 
Principal Maintenance Inspector, who may concur or comment and then 
send it to the Manager, Boston Aircraft Certification Office.

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

    (e) 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 June 14, 1994.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 94-15148 Filed 6-21-94; 8:45 am]
BILLING CODE 4910-13-P