AD 95-10-09 ACTIVE

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

Final rule

95-10-09 SIKORSKY AIRCRAFT: Amendment 39-9226. Docket No. 93-SW-18-AD.

Applicability: Model S-58 and S-58T series helicopters, certificated in any category.

NOTE 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been 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 use the authority provided in paragraph (d) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any helicopter from the applicability of this AD.

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 it 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 Bulletin 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, for 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, those ring gears 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 2: 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.

(f) The removal and replacement shall be done in accordance with Sikorsky Aircraft Alert Service Bulletin No. 58B35-32, dated July 6, 1993. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Sikorsky Aircraft, Commercial Customer Support, 6900 Main Street, Stratford, Connecticut 06601-1381. Copies may be inspected at the FAA, Office of the Assistant Chief Counsel, 2601 Meacham Boulevard, Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(g) This amendment becomes effective on June 16, 1995.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to Sikorsky Aircraft Model S-58 and S-58T series helicopters was published in the Federal Register on June 22, 1994 (59 FR 32144). That action proposed to require the removal and replacement of the ring gear within certain time intervals, and proposed to establish a retirement life for the ring gear.

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. Since the issuance of the proposed rule, the FAA has revised the average labor rate from $55 per work hour to $60 per work hour, which increases the estimated cost impact on operators to $486,250.

The FAA estimates that 125 helicopters of U.S. registry will be affected by this AD, that it will take approximately 31.5 work hours per helicopter to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $2,000 per helicopter. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $486,250.

The regulations adopted herein will 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 final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

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 location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, 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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

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

The service information referenced in this AD 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; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

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.