01-2428. Airworthiness Directives; Sikorsky Aircraft Corporation Model S-76A Helicopters

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes revising an existing airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-76A helicopters. That AD currently requires a one-time inspection of the tail rotor blade (blade) spar elliptical centering plug (centering plug) for disbonding and the addition of a retaining pad on the pitch change shaft between the output tail rotor gearbox flange and the inboard tail rotor spar. This action would contain the same requirements as the existing AD but would clarify that the 500-hour time-in-service (TIS) repetitive inspections, which could cause inadvertent damage, are not required. This AD would also incorporate by reference a revised alert service bulletin (ASB) that does not include the 500-hour TIS repetitive inspections. This proposal is prompted by operator confusion about whether the current AD continues to require the 500-hour TIS repetitive inspections. The proposed AD is intended to verify that the FAA has determined that the 500-hour TIS repetitive inspections are not required to prevent the centering plug from disbonding and moving out of position, loss of tail rotor control, and subsequent loss of control of the helicopter.

DATES:

Comments must be received on or before April 2, 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-40-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137. You may also send comments electronically to the Rules Docket at the following address: [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:

Richard Noll, 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-40-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-40-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.

Discussion

On June 30, 1994, the FAA issued AD 94-14-20, Amendment 39-8969 (59 FR 41238, August 11, 1994), to require inspecting each blade centering plug for disbonding; adding a retaining pad on the pitch change shaft between the tail rotor output gearbox flange and the inboard blade spar; and removing the 500-hour repetitive inspection. That action was prompted by successful service experience and an improved bonding procedure. The requirements of that AD are intended to prevent the centering plug from disbonding and moving out of position, loss of tail rotor control, and subsequent loss of control of the helicopter.

Since the issuance of that AD, Sikorsky has issued revised ASB 76-65-35B, dated October 2, 1997, to supersede the basic ASB. The revised ASB amplifies the basic procedures and specifies that the recurring inspection interval (formerly 500-hours time-in-service (TIS)) is the interval specified in the S-76A Airworthiness Limitations and Inspection Schedule. The ASB also revises the text referencing consumables by changing military specifications to commercial equivalents.

The FAA has become aware that 500-hour TIS repetitive inspections are being conducted because of the misconception that AD 94-14-20 mandates the entire ASB. These repetitive inspections could result in inadvertent damage to the tail rotor blades. The FAA understands how this confusion could occur since the AD language does inadvertently incorporate all the inspection requirements of Sikorsky Aircraft Alert Service Bulletin 76-15-35A, Revision A, dated February 29, 1984. However, that was not the intent of the AD as explained in the preamble to AD 94-14-20. The FAA intended to eliminate the 500-hour TIS repetitive inspections for centering plug disbonding. Incorporating specific portions of ASB 76-65-35B, dated October 2, 1997, that does not contain the 500-hour TIS repetitive inspections will clarify the intended AD requirements.

We have identified an unsafe condition that is likely to exist or develop on other Sikorsky Model S-76A helicopters of the same type design. The proposed AD would revise AD 94-14-20 and would retain the same basic requirements but would incorporate by reference portions of the revised ASB and would clarify that the repetitive inspections are not required by the AD.

The FAA estimates that this proposed AD would affect 150 helicopters of U.S. registry. The revised AD would not impose any additional burden or costs.

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 39-8969 (59 FR 41238, August 11, 1994), and by adding a new airworthiness directive (AD), to read as follows:

Sikorsky Aircraft Corporation: Docket No. 2000-SW-40-AD. Revises AD 94-14-20, Amendment 39-8969, Docket No. 93-SW-13-AD.

Applicability: Model S-76A helicopters, with tail rotor blade (blade) assembly, part number (P/N) 76101-05001 (all dash numbers) or 76101-05101 (all dash numbers), installed with more than 130 hours time-in-service (TIS), 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 within 25 hours TIS, unless accomplished previously.

To prevent the blade spar elliptical centering plug (centering plug) from disbonding and moving out of position, loss of tail rotor control, and subsequent loss of control of the helicopter, accomplish the following:

(a) Inspect the centering plug for disbonding of the polyurethane filler that fills the space between the aluminum centering plug and the graphite spar in accordance with the Accomplishment Instructions, paragraph 3.A.(1) and (2), of Sikorsky Aircraft Corporation Alert Service Bulletin No. 76-65-35B, dated October 2, 1997 (ASB).

Note 2:

The 500-hours TIS repetitive inspections contained in the Accomplishment Instructions, paragraph 3.D., of Sikorsky Aircraft Corporation Alert Service Bulletin 76-65-35A, Revision A, dated February 29, 1984, are not required by this AD.

(1) If the inspection of the centering plug reveals disbonding of 1/2-inch or less in length, install a retaining pad, P/N 76102-05004-111, in accordance with the Accomplishment Instructions, paragraph 3.C., of the ASB.

(2) For disbonds greater than 1/2-inch in length, repair the blade assembly in accordance with the Accomplishment Instructions, paragraph 3.B.(1), of the ASB except you are not required to contact Sikorsky Worldwide Customer Service. If blades are found with polyurethane filler excessively cracked or deteriorated to extent of breaking away from the spar or aluminum plug by 0.005-inch or greater, replace the blade with an airworthy blade.

(3) For spars with complete spar to centering plug disbond in which the polyurethane filler is intact and remains fully bonded to the centering plug, repair the blade assembly in accordance with the Accomplishment Instructions, paragraph 3.B.(2), of the ASB.

(4) For spars with complete polyurethane filler to centering plug disbond in which the polyurethane filler is intact and remains fully bonded to the spar, repair the blade assembly in accordance with the Accomplishment Instructions, paragraph 3.B.(3) of the ASB.

(b) Install a retaining pad, P/N 76102-05004-111, in accordance with the Accomplishment Instructions, paragraph 3.C., of the ASB.

(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, 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 3:

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

(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 if a retaining pad has been installed.

Issued in Fort Worth, Texas, on January 22, 2001.

Henry A. Armstrong,

Manager, Rotorcraft Directorate, Aircraft Certification Service.