COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Brantly B-2 Series Helicopters AD/B-2/26 Main Rotor Mast Upper Bearing - Replacement 7/67 Applicability: All model B-2, B-2A and B-2B with P/N B2-324 transmission with S/Nos. prior to 307. Document: Brantly SB No. 21. Compliance: Within 100 hours time in service after 15 August 1967.