01-9074. Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V Helicopters

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes superseding an existing airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-61A, D, E, L, N, NM, R, and V helicopters. That AD currently requires a nondestructive inspection (NDI) for a crack in the main rotor shaft (shaft) and replacing any cracked shaft. This action would require establishing and defining new life limits and removing certain shafts from service. This proposal is prompted by the final results of fatigue tests indicating the need to establish life limits for certain shafts. The actions specified by the proposed AD are intended to prevent structural failure of the shaft, loss of power to the main rotor, and subsequent loss of control of the helicopter.

DATES:

Comments must be received on or before June 11, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Regional Counsel, Southwest Region, Attention: Rules Docket No. 2000-SW-43-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137. You may also send comments electronically to the Rules Docket at [e-mail]. 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:

Wayne Gaulzetti, Aviation Safety Engineer, Boston Aircraft Certification Office, 12 New England Executive Park, Burlington, MA 01803, telephone [phone], fax [phone].

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 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. 2000-SW-43-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. 2000-SW-43-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.

Discussion

On December 7, 1998, the FAA issued AD 98-26-02, Amendment 39-10943 (63 FR 69177, December 16, 1998), for Sikorsky Model S-61A, D, E, L, N, NM, R, and V helicopters. That AD required an NDI of certain shafts used in repetitive external lift (REL) operations, replacing any cracked shaft, appropriately marking shafts, and establishing a new shaft retirement life. That action was prompted by reports of cracked shafts in helicopters utilized in REL operations. The requirements of that AD are intended to detect a fatigue crack in the shaft that could result in shaft structural failure, loss of power to the main rotor, and subsequent loss of control of the helicopter.

REL operation is defined as an operation during which the average number of external lifts equals or exceeds six per flight hour for any 250-hour TIS period during the main gearbox overhaul interval. An external lift is defined as a flight cycle in which an external load is picked up, the helicopter is repositioned (through flight or hover), and the helicopter hovers and releases the load and departs or lands and departs.

Since the issuance of that AD, Sikorsky has issued an Alert Service Bulletin No. 61B35-68B, Revision B, dated July 6, 2000 (ASB), to establish a retirement time for shafts used in REL and non-REL operations and to perform an NDI on certain shafts with expired time. Sikorsky conducted fatigue testing, evaluated three S-61 shafts, and investigated two shafts that cracked in service. With this additional data and analysis, new life limits for shafts operated in all categories, REL and non-REL, and all configurations have been established.

Since an unsafe condition has been identified that is likely to exist or develop on other Sikorsky Model S-61A, D, E, L, N, NM, R, and V helicopters of these same type designs, the proposed AD would supersede AD 98-26-02 to require for each shaft, part number (P/N) S6135-20640-001, S6135-20640-002, or S6137-23040-001, the following:

• Determine whether the shaft has been utilized in REL or non-REL operations;
• If the shaft has been used in REL operations, perform an NDI.
• Acid-etch the letters “REL” on any airworthy shaft that will be used in REL operations;
• Remove from service at or before the next main gearbox overhaul, any shaft using an oversize dowel pin bore repair identified as TS-281 or TS-041-3; and
• This proposal would also establish new life limits for shafts in all REL and non-REL operations.

The FAA estimates that 30 helicopters of U.S. registry involved in REL and 30 involved in non-REL operations would be affected by this proposed AD. It would take approximately 2.2 work hours to inspect a shaft when it is removed during transmission overhaul, and the average labor rate is $60 per work hour. Required material for each shaft inspection would cost approximately $50 per shaft, and a replacement shaft costs $44,753. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $1,353,510, assuming that all shafts used in REL operation would need to be replaced as a result of this proposal.

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.

§ 39.13

[Amended]

2. Section 39.13 is amended by removing Amendment 39-10943 (63 FR 69177, December 16, 1998), and by adding a new airworthiness directive, to read as follows:

Sikorsky Aircraft Corporation: Docket No. 2000-SW-43-AD. Supersedes AD 98-26-02, Amendment 39-10943, Docket No. 96-SW-29-AD.

Applicability: Model S-61A, D, E, L, N, NM, R, and V helicopters, with main rotor shaft (shaft), part number (P/N) S6135-20640-001, S6135-20640-002, or S6137-23040-001, 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 (g) 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 detect a fatigue crack in the shaft that could result in shaft structural failure, loss of power to the main rotor, and subsequent loss of control of the helicopter, accomplish the following:

(a) Within the next 30 days or 240 hours time-in-service (TIS), whichever occurs first, determine if the shaft has been used in repetitive external lift (REL) operations. REL operation is defined as an operation during which the average number of external lifts equals or exceeds 6 per flight hour for any 250-hour TIS period during the main gearbox overhaul interval. An external lift is defined as a flight cycle in which an external load is picked up, the helicopter is repositioned (through flight or hover), and the helicopter hovers and releases the load and departs or lands and departs.

(1) On the component log card or equivalent record, record the total number of hours TIS during which external lifts have been conducted and the number of external lifts conducted during each hour.

(2) If the hours TIS of external lift operations or the number of lifts cannot be determined, assume REL operations were conducted.

(b) Within the next 1,100 hours TIS, conduct a non-destructive inspection (NDI) for a crack on shafts used in REL operations in accordance with the Overhaul Manual.

(1) Before further flight, replace any cracked shaft with an airworthy shaft.

(2) If the shaft has been used or will be used in REL operations, prior to installation, mark the shafts in accordance with the Accomplishment Instructions in paragraphs 2E and 2F of Sikorsky Aircraft Corporation Alert Service Bulletin (ASB) No. 61B35-68B, dated July 6, 2000. Once a shaft has been designated and marked as an REL shaft, it is life-limited in accordance with paragraph (g) of this AD for the remainder of that shaft's airworthy service life.

(c) During or before the next main gearbox overhaul, remove all shafts used in REL or non-REL operations that were repaired using an oversize dowel pin bore repair TS-281 or TS-041-3, and replace the shaft with an airworthy shaft. Shafts repaired using TS-281 or TS-041-3 cannot be reinstalled in any gearbox.

(d) For shafts that have been used in REL operations,

(1) On or before attaining 2,200 hours TIS, remove any shaft that has been modified (modified REL shaft) in accordance with Sikorsky Customer Service Notice 6135-10, dated March 18, 1987, and Sikorsky ASB No. 61B35-53, dated December 2, 1981.

(2) On or before attaining 1,500 hours TIS, remove any shaft that has not been modified (unmodified REL shaft) in accordance with Sikorsky Customer Service Notice 6135-10, dated March 18, 1987, and Sikorsky ASB No. 61B35-53, dated December 2, 1981.

(3) On or before attaining 535 hours TIS, remove any shaft, modified or unmodified, if the total TIS is unknown.

(e) For shafts used exclusively in non-REL operations,

(1) Record the hours TIS. If the total hours TIS cannot be determined, record 12,500 hours TIS.

(2) On or before attaining 42,000 hours TIS, remove any shaft used exclusively in non-REL operations.

(f) This AD revises the airworthiness limitations section of the maintenance manual by establishing for shafts, P/N S6135-20640-001, S6135-20640-002, and S6137-23040-001:

(1) A retirement life for shafts that have been used in REL operations as follows: 1,500 hours TIS for unmodified shafts; 2,200 hours TIS for modified shafts; or 535 hours TIS for modified or unmodified shafts when previous TIS is unknown; and

(2) A retirement life for shafts used exclusively in non-REL operations of 42,000 hours TIS.

(g) 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, Boston Aircraft Certification Office. 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.

(h) 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 April 4, 2001.

Eric Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.