
[Federal Register: June 4, 2008 (Volume 73, Number 108)]
[Proposed Rules]               
[Page 31780-31782]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr04jn08-8]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0609; Directorate Identifier 2008-SW-24-AD]
RIN 2120-AA64

 
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).

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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: 202-493-2251.
     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 (203) 383-4866, e-mail address tsslibrary@sikorsky.com.

FOR FURTHER INFORMATION CONTACT: Richard Noll, Aviation Safety 
Engineer, Boston Aircraft Certification Office, 12 New England 
Executive Park, Burlington, MA 01803, telephone (781) 238-7160, fax 
(781) 238-7170.

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

[[Page 31781]]

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 (800) 647-5527) 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:

------------------------------------------------------------------------
                                                       Aft spar assembly
                  Helicopter model                         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.

[[Page 31782]]

    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.


Sec.  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.

------------------------------------------------------------------------
                                                           Vertical
                                                        stabilizer aft
                  Helicopter model                    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 (781) 238-7160, fax (781) 238-7170, 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.
[FR Doc. E8-12414 Filed 6-3-08; 8:45 am]

BILLING CODE 4910-13-P
