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-76/30 Amdt 1 Applicability: Model S76A. Tail Rotor Blade Elliptical Centering Plug and Retaining Pad 12/94 Requirement: Action in accordance with Sikorsky SB 76-65-35 Rev A. Note: FAA AD 94-14-20 refers. This supersedes FAA AD 84-06-02. Compliance: Unless already accomplished, within 25 hours time in service after 13 October 1994. The effective date of the initial issue was 27 February 1984. Background: An operator encountered severe vibration during flight while executing a left turn after take-off. Investigation revealed disbonding of the aluminium elliptical spar plug which allowed the tail rotor blade to be displaced in a radial direction. Amendment 1 withdraws the repetitive inspection requirement as a result of no further reports of failure following the inspection and modification in accordance with the Service Bulletin.