AD 73-16-01

73-16-01 SIKORSKY: Amendment 39-1694.

Pursuant to the authority of the Federal Aviation Act of 1958, as amended, delegated to me by the Administrator, the following airworthiness directive applicable to operators of Sikorsky S-55 series helicopters modified to incorporate AiResearch TSE331-3U-303N engines installed in accordance with Supplemental Type Certificate No. SH125-WE or SH127WE was effective immediately upon receipt of the telegram dated July 17, 1973. This directive is necessary because of the possibility of engine overspeed and resultant third stage turbine failure. Except as provided by FAR 21.197, the following is required prior to further flight:

(a) Install a fuel bypass system in accordance with AiResearch Service Bulletin No. TSE331-73-5004 and Aviation Specialties Service Bulletin No. AS55-01-1, both dated July 16, 1973, or later FAA-Approved revisions thereto.

(b) Incorporate the FAA-Approved Aviation Specialties Rotorcraft Flight Manual Revision3 dated July 17, 1973.

(c) Equivalent modifications and rotorcraft flight manual revisions may be approved by the Chief, Aircraft Engineering Division, FAA Western Region.

This amendment is effective July 31, 1973, for all persons except those to whom it was made effective immediately by telegram dated July 17, 1973.