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2002-21-07 Sikorsky Aircraft Corporation: Amendment 39-12913. Docket No. 2001-SW-59-AD.
Applicability: Model S-76A, S-76B and S-76C helicopters, except those having a serial number of 760501, or 760506 through 760515, 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 addressit.
Compliance: Required within 1,250-hours time-in-service or 2 years, whichever comes first, unless accomplished previously.
To detect installation of an incorrect main rotor spindle attachment bolt (bolt), which could result in reduced hub or bolt fatigue life, separation of the main rotor blade at the spindle attachment, and subsequent loss of control of the helicopter, accomplish the following:
(a) Remove and measure each bolt to ensure that the length is 1.181 +/-.015 inches. There are 10 bolts per rotor spindle and 40 bolts per helicopter that require inspection.
(1) If 1 or 2 bolts are found on any spindle that are longer than 1.196 inches (1.181 inches + .015-inch permissible tolerance), visually inspect the main rotor hub internal threads for distortion and the hole-bottoms for scoring.
(i) If thread distortion or hole-bottom scoring is found, remove the rotor hub from service.
(ii) If no thread distortion or hole-bottom scoring is found, replaceall 10 bolts with new airworthy bolts.
(2) If 3 or more bolts that exceed 1.196 inches are found on any spindle, remove and replace the main rotor hub with an airworthy main rotor hub.
(3) If any bolt is found that is shorter than 1.166 inches (1.181 inches -.015 permissible tolerance), replace it with a new airworthy bolt.
(b) Report the results of the inspections of the main rotor hubs whenever the bolts exceed 1.196 inches in length, within 5 calendar days of the inspection, to the Manager, Boston Aircraft Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone: (781) 238-7150; fax: (781) 238-7170. Include the following information in the report:
(1) Serial number of the helicopter.
(2) Quantity of incorrect bolts.
(3) Description of thread distortion or hole-bottom scoring caused by each bolt. Information collection requirements contained in this AD have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056.
Note 2: Sikorsky Aircraft Corporation Alert Service Bulletin No. 76-65-52 (321), dated July 24, 2001, pertains to the subject of this AD.
(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, Engine and Propeller Directorate, 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 21.197and 21.199 to operate the helicopter to a location where the requirements of this AD can be accomplished.
(e) This amendment becomes effective on November 25, 2002.
