COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bell Helicopter Textron Canada (BHTC) 206 and Agusta Bell 206 Series Helicopters AD/BELL 206/74 Tail Rotor Drive Shaft Bearings - Replacement 4/74 Applicability: All models AB206, 206A and 206B as referenced in requirement documents. Document: Bell SB 206-76-12, Rev. A, or Agusta SB No. BT206-116, Rev. A. Compliance: Within 100 hours time in service after 30 April 1977. Background: AD/Agusta 206/59 equivalent.