AD 2010-17-16

AD Final Rules - 2010-17-16.pdf
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AD Number:
2010-17-16
Document Type:
AD Final Rules
Docket Number:
FAA-2008-0609
Subject Heading:
Airworthiness Directives; Sikorsky Aircraft Corporation Model S- 76A, S-76B, and S-76C Helicopters
Subject:
Vertical Stabilizer
Status:
Current
Citation:
Federal Register: September 13, 2010
Citation Publish Date:
09/13/2010
Effective Date:
10/18/2010
Make:
Sikorsky Aircraft Corporation
Model:
S-76A | S-76B | S-76C
Product Type:
Aircraft
Product Subtype:
Rotorcraft
Affected AD:
Superseded AD:
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39
Comments:
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[Federal Register: September 13, 2010 (Volume 75, Number 176)]


[Rules and Regulations]


[Page 55453-55455]


From the Federal Register Online via GPO Access [wais.access.gpo.gov]


[DOCID:fr13se10-1]


––––––––––––––––––––––––––––––––––


DEPARTMENT OF TRANSPORTATION


Federal Aviation Administration


14 CFR Part 39


[Docket No. FAA-2008-0609; Directorate Identifier 2008-SW-24-AD; Amendment 39-16408 AD


2010-17-16]


RIN 2120-AA64


Airworthiness Directives; Sikorsky Aircraft Corporation Model S-76A, S-76B, and S-76C


Helicopters


AGENCY:
 
Federal Aviation Administration, DOT.


ACTION:
 
Final rule.


––––––––––––––––––––––––––––––––––


SUMMARY:
 
We are adopting a new airworthiness directive (AD) for Sikorsky Aircraft Corporation


(Sikorsky) Model S-76A, S-76B, and S-76C helicopters. This AD requires 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 is also required. This AD also requires a recurring track-and-balance of the tail rotor.


Finally, this AD requires installing a vertical stabilizer modification kit, which is terminating action


for the requirements of the AD. This AD is prompted by 26 reports of fatigue cracks in the aft spar


assembly web and outer caps. The actions specified by this 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:
 
Effective October 18, 2010.


The incorporation by reference of certain publications listed in the regulations is approved by the


Director of the Federal Register as of October 18, 2010.


ADDRESSES:
 
You may get the service information identified in this 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.


Examining the Docket: You may examine the docket that contains this AD, any comments, and


other information on the Internet at http://www.regulations.gov or at the Docket Operations office,


West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC.


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FOR FURTHER INFORMATION CONTACT:
 
Nicholas Faust, Aviation Safety Engineer, 16


New England Executive Park, Burlington, MA 01803; telephone: (781) 238-7763; fax: (781) 238-


7170.


SUPPLEMENTARY INFORMATION:
 
A proposal to amend 14 CFR part 39 to include an AD for


certain Sikorsky Model S-76A, S-76B, and S-76C helicopters was published in the Federal Register


on June 4, 2008 (73 FR 31780). The proposed action applied to 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 number (P/N)


76201–05002–114
S–76A


76201–05002–115


76201–05002–047


76201–05002–048


76201–25002–041


76201–25002–044


76201–25002–045


S–76B and S–76C


76201–25002–046


That action proposed to require, for any spar assembly that has 1,000 or more hours time-in-service


(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 fasteners, 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 action also proposed to require, within 30 days and thereafter at


intervals not to exceed 200 hours TIS, track-and-balance of the tail rotor. Accomplishing the tail rotor


track-and-balance 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, proposed was requiring, 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 proposed AD.


Interested persons have been afforded an opportunity to participate in the making of this


amendment. Due consideration has been given to the one comment received from the manufacturer.


Sikorsky states that the effectivity should also include the aircraft serial number as referenced in


their Alert Service Bulletin (ASB) No. 76-55-21. Sikorsky recommends the following wording ''Note


All S-76 helicopter serial numbers greater than 760578 but not including helicopter serial number


762976 are not affected.'' Sikorsky states that ''this would ease the operator burden for aircraft built


after the affected population of verifying the spar part numbers to show compliance with the AD.''


We concur with Sikorsky's recommendation to limit the applicability to only specified serial


numbered helicopters and have revised the AD accordingly. Further, we inadvertently omitted the


dash numbers to the part numbers of the modification kits contained in paragraph (c) of the proposed


AD; ''-011'' has been added to each of the part numbers in this final rule.


We have reviewed the following service information:


•
 
Sikorsky Alert Service Bulletin (ASB) No. 76-55-20A, Revision A, dated November 11, 2003


(76-55-20A), 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.


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