E8-12414. Airworthiness Directives; Sikorsky Aircraft Corporation Model S-76A, S-76B, and S-76C Helicopters

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes adopting a new airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-76A, S-76B, and S-76C helicopters. The AD would require an initial and recurring inspections of the tail rotor vertical stabilizer aft spar assembly (aft spar assembly) for a crack, loose or working fasteners, and corrosion, and, if any are found, further inspections of the vertical stabilizer forward spar assembly (forward spar assembly). Repairing or replacing any unairworthy part before further flight would also be required. The action would also require a recurring track-and-balance of the tail rotor. Finally, the proposed AD would require installing a vertical stabilizer modification kit, which would be terminating action for the requirements of the AD. This proposal is prompted by 26 reports of fatigue cracks in the aft spar assembly web and outer caps. The actions specified by the proposed AD are intended to detect and correct an unbalanced or out-of-track tail rotor, which could lead to increased vibrations, a fatigue crack, loss of a portion of the vertical stabilizer and subsequent loss of control of the helicopter.

DATES:

Comments must be received on or before August 4, 2008.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

You may get the service information identified in this proposed AD from Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical Support, Mailstop s581a, 6900 Main Street, Stratford, Connecticut 06614, phone [phone], e-mail address [e-mail].

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

We invite you to submit any written data, views, or arguments regarding this proposed AD. Send your comments to the address listed under the caption ADDRESSES. Include the docket number “FAA-2008-0609, Directorate Identifier 2008-SW-24-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed rulemaking. Using the search function of the docket Web site, you can find and read the comments to any of our dockets, and if provided, the name of the individual who sent or signed the comment. You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477).

Examining the Docket

You may examine the docket that contains the proposed AD, any comments, and other information in person at the Docket Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Operations office (telephone [phone]) is located in Room W12-140 on the ground floor of the West Building at the street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

Discussion

This document proposes adopting a new AD for Sikorsky Model S-76A, S-76B, and S-76C helicopters with any of the following part-numbered aft spar assemblies installed:

Helicopter model	Aft spar assembly part No.
S-76A	76201-05002-114
	76201-05002-115
S-76B and S-76C	76201-05002-047
	76201-05002-048
	76201-25002-041
	76201-25002-044
	76201-25002-045
	76201-25002-046

For any aft spar assembly having 1,000 or more hours time-in-service (TIS), the AD would require, initially and then at intervals not to exceed 50 hours TIS, inspecting the aft spar assembly for a crack, a loose or working fastener, or corrosion. If a crack, a loose or working fastener, or corrosion is found, repairing or replacing any unairworthy parts and inspecting the forward spar assembly would be required before further flight. If that inspection reveals a crack, a loose or working fastener, or corrosion in the forward spar assembly, then the damage would have to be repaired or the parts would need to be replaced with airworthy parts before further flight. The AD would also require a track-and-balance of the tail rotor within 30 days and thereafter at intervals not to exceed 200 hours TIS. The AD would also require, on or before December 31, 2010, installing a vertical stabilizer modification kit, part number (P/N) 76070-20562, 76070-20563, or 76070-20564, which would be terminating action for the requirements of the AD.

This proposal is prompted by 26 reports of fatigue cracks in the aft spar assembly web and outer caps since February 1998. The actions specified in this proposed AD are intended to detect and correct an unbalanced or out-of-track tail rotor, which could lead to increased vibrations, a fatigue crack, loss of a portion of the vertical stabilizer and subsequent loss of control of the helicopter.

We have reviewed the following service information:

• Sikorsky Alert Service Bulletin (ASB) No. 76-55-20A, Revision A, dated November 11, 2003, that applies to Sikorsky Model S-76A and Model S-76C helicopters and describes procedures for a one-time inspection of the vertical stabilizer aft spar assembly for cracks, loose or working fasteners, and/or corrosion, and if necessary an inspection of the forward spar assembly.
• ASB No. 76-65-58A, Revision A, dated November 11, 2003, that applies to all Sikorsky Model S-76 serial numbered helicopters up to and including 760526 and describes procedures for an initial enhanced tail rotor balance check.

This proposal would differ from those ASBs in that the inspections described in ASB No. 76-55-20A would be required for the Model S-76B helicopters as well as for the Model S-76A and Model S-76C helicopters. Also, the proposed AD would require repetitive inspections of the aft spar assembly and the forward spar assembly, if necessary, and repetitive tail rotor track-and-balance inspections, whereas the two ASBs specify only a one-time tail rotor balance check and an aft spar assembly inspection and, if necessary, a one-time forward spar assembly inspection.

This unsafe condition is likely to exist or develop on other helicopters of the same type designs. Therefore, the proposed AD would require, for any spar assembly that has 1,000 or more hours TIS, within 30 days and thereafter at intervals not to exceed 50 hours TIS, inspecting the aft spar assembly, and if you find a crack, a loose or working fastener, or corrosion, inspecting the forward spar assembly before further flight and replacing or repairing any unairworthy part with an airworthy part before further flight.

The AD would also require, within 30 days and thereafter at intervals not to exceed 200 hours TIS, inspecting the tail rotor track-and-balance. Accomplishing the tail rotor track-and-balance inspection would involve both a pilot and mechanic. The pilot's function would be to operate the helicopter to a “light on wheels” state—almost to the point of takeoff, and the mechanic would accomplish the vibration measurements. Also, the AD would require, on or before December 31, 2010, installing a vertical stabilizer modification kit, P/N 76070-20562, 76070-20563, or 76070-20564, which would be terminating action for the requirements of the AD. The inspections and repairs or replacements, if necessary, would have to be accomplished in accordance with specified portions of the ASBs previously described.

We estimate that this proposed AD would affect 216 helicopters of U.S. registry. We also estimate that the inspections for a crack, a loose or working fastener, or corrosion would take approximately 7 work hours per helicopter to accomplish; the tail rotor track-and-balance inspections and adjustments would take approximately 10 work hours per helicopter; and installing the vertical stabilizer modification kit would take approximately 120 hours, at an average labor rate of $80 per work hour. The vertical stabilizer modification kit would cost approximately $4,250. Based on these figures, we estimate the total cost impact of this AD on U.S. operators would be $4,961,520, assuming that, on each helicopter, 12 spar assembly inspections would be done ($1,451,520), that 3 tail rotor track-and-balance inspections would be done ($518,400), that no spar assembly would need to be repaired or replaced, and that the vertical stabilizer modification is done.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. Additionally, this proposed AD 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.

For the reasons discussed above, I certify that the 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. 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.

We prepared a draft economic evaluation of the estimated costs to comply with this proposed AD. See the AD docket to examine the draft economic evaluation.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

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 adding a new airworthiness directive to read as follows:

Sikorsky Aircraft Corporation: Docket No. FAA-2008-0609; Directorate Identifier 2008-SW-24-AD.

Applicability: Model S-76A, S-76B, and S-76C helicopters with any of the following part-numbered vertical stabilizer aft spars assemblies having 1,000 or more hours time-in-service (TIS) installed, certificated in any category.

Helicopter model	Vertical stabilizer aft spar assembly part No.
S-76A	76201-05002-114
	76201-05002-115
S-76B and S-76C	76201-05002-047
	76201-05002-048
	76201-25002-041
	76201-25002-044
	76201-25002-045
	76201-25002-046

Compliance: Required as indicated.

To detect and correct an unbalanced or out-of-track tail rotor, which could lead to increased vibrations a fatigue crack, loss of a portion of the vertical stabilizer, and subsequent loss of control of the helicopter, accomplish the following:

(a) Within 30 days, unless accomplished previously, and thereafter at intervals not to exceed 50 hours TIS, inspect the vertical stabilizer aft spar assembly (aft spar assembly) for a crack, a loose or working fastener, or corrosion in accordance with the Accomplishment Instructions, paragraph 3.A., in Sikorsky Alert Service Bulletin (ASB) No. 76-55-20A, Revision A, dated November 11, 2003 (No. 76-55-20A). For purposes of this AD, ASB No 76-55-20A pertains to Model S-76B helicopters as well as Model S-76A and S-76C helicopters.

(1) If a crack, a loose or working fastener, or corrosion is found in the aft spar assembly, before further flight:

(i) Repair or replace any unairworthy parts and

(ii) Inspect the vertical stabilizer forward spar assembly (forward spar assembly) for a crack, a loose or working fastener, or corrosion in accordance with the Accomplishment Instructions, paragraph 3.B., in ASB No. 76-55-20A. Contacting the manufacturer is not required by this AD.

(2) If a crack, a loose or working fastener, or corrosion is found in the forward spar assembly, repair in accordance with the applicable maintenance manual or replace with airworthy parts before further flight.

(b) Within 30 days, unless accomplished previously, and thereafter at intervals not to exceed 200 hours TIS, track-and-balance the tail rotor in accordance with the Accomplishment Instructions, paragraph 3.A., in ASB No. 76-65-58A, dated November 11, 2003.

Note 1:

Although the ASB specifies only an initial inspection of the aft spar assembly and a track-and-balance of the tail rotor, this AD requires inspecting the aft spar assembly and track-and-balancing the tail rotor repetitively.

Note 2:

The track-and-balancing of the tail rotor that is required by paragraph (b) of this AD involves both a pilot and mechanic. The pilot's function is to operate the helicopter to a “light on wheels” state—almost to the point of takeoff. The mechanic is needed to accomplish the vibration measurements.

(c) On or before December 31, 2010, install a vertical stabilizer modification kit, part number 76070-20562, 76070-20563, or 76070-20564. Installing the vertical stabilizer modification kit is terminating action for the requirements of this AD.

(d) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact the Manager, Boston Aircraft Certification Office, Engine and Propeller Directorate, ATTN: Richard Noll, Aviation Safety Engineer, FAA, 12 New England Executive Park, Burlington, MA 01803, telephone [phone], fax [phone], for information about previously approved alternative methods of compliance.

Issued in Fort Worth, Texas, on May 22, 2008.

David A. Downey,

Manager, Rotorcraft Directorate, Aircraft Certification Service.