AD 84-01-51

84-01-51 SIKORSKY AIRCRAFT: Amendment 39-4826. Applies to Model S-61 series aircraft certificated in all categories.

Compliance required within the next 25 hours time in service after the effective date of this AD, unless already accomplished.

As a result of finding a crack in a rotary wing head shaft nut and finding the nut had improper Rockwell hardness and because of possible incomplete processing of these nuts, P/N S6110-21082-0, accomplish the following:

(a) Fluorescent magnetic particle inspect and Rockwell hardness test the rotary wing head shaft nut, in accordance with Section B of Sikorsky Service Bulletin No. 61B10-14, dated November 3, 1969, as revised by Sikorsky Message Number CST-P-83-171, Revision 2, dated December 5, 1983. Visible magnetic particle inspection and Rockwell hardness test in accordance with Section B of the service bulletin may be used as an alternate to fluorescent magnetic particle inspection and Rockwell hardness test.

(b) Anynut with cracks or not within the proper hardness range specified in Sikorsky service documents specified in paragraph (a) of this AD must be replaced before further flight with a nut that has been inspected in accordance with paragraph (a) of this AD and baked and marked in accordance with paragraph (c) of this AD or with a Sikorsky provided nut inspected and marked in accordance with this AD.

(c) Any nut not cracked and with proper hardness as specified in the Sikorsky service documents must be baked at 375 degrees fahrenheit plus/minus 25 degrees fahrenheit for a minimum of three hours and marked in accordance with the Sikorsky service documents specified in paragraph (a) of this AD.

(d) Alternate inspections, processes, or other means of compliance which provide an equivalent level of safety to this AD must be approved by the Manager, Boston Aircraft Certification Branch, New England Region, Federal Aviation Administration, 12 New England Executive Park, Burlington, Massachusetts 01803. In accordance with FAR 21.197, flight is permitted to a base where the requirements of this AD -may be accomplished.

Sikorsky Service Bulletin No. 61B10-14, dated November 3, 1969, and Sikorsky message Number CST-P-83-171, Revision 2, dated December 5, 1983, identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 551(a)(1). All persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to United Technologies Corporation, Sikorsky Aircraft, North Main Street, Stratford, Connecticut 06602, ATTN: S-61 Commercial Product Support Department. These documents also may be examined in the Office of the Regional Counsel, Federal Aviation Administration, Southwest Region, 4400 Blue Mound Road, Fort Worth, Texas 76106.

This amendment supersedes Amendment 39-889 (34 FR 19545), AD 69-25-05, which became effective December 10, 1969.

This amendment becomes effective March 27, 1984, as to all persons except those persons to whom it was made immediately effective by the telegram dated December 30, 1983, which contained this amendment.