COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Sikorsky S-76 Series Helicopters AD/S-76/35 Tail Rotor Controls Centering Quadrant - Modification 10/84 Applicability: All models S-76A. Requirement: Sikorsky CSN No. 76-133 Revision A. Note: FAA AD 84-15-04 Amdt. 39-4893 refers. Compliance: Unless already accomplished, within 30 days after 31 October 1984. Background: There have been two reports of tail rotor cable failure. Both failures have been caused by misrigging of the control cables over the pulley guide pin at the lower left-hand pulley, located under the main gearbox. The misrigging has resulted in accelerated wear and subsequent failure. The modification incorporates a centering quadrant which returns the tail rotor pitch controls to the basic rigging position if tail rotor control cable fails.