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-2/31 Main Rotor Mast - Inspection 9/71 Applicability: All model B-2, B-2A and B-2B. Requirement: 1. Remove mast plug P/N 151-18. 2. Visually inspect the inner bore surface over the entire length of the main rotor mast for presence of rust or corrosion using a light and mirror. The presence of any rust or corrosion which cannot be removed with a lint free cloth is cause for removal of the transmission assembly. 3. Prior to reinstallation or replacement of the mast accomplish the appropriate inspection items under the heading "Main Transmission" of the 1200 Hour Interval Inspection, Section 1.8.7, Brantly Maintenance Manual. 4. If the main rotor mast is free or can be freed of rust or corrosion following the inspections noted in Para. (2), apply a thin film of Esso Rust-Ban 626, Avrex 901 or equivalent preserving type lubricating oil to the entire length of the inner bore surface. 5. Re-install the mast plug with a new "O" ring packing P/N AN 6227-26 and retain in place with the clevis pin P/N AN 393-11 that retains the hub retaining nut P/N 150-1. Secure clevis pin by installing washer, P/N AN 960-10L and cotter pin AN 380-2-1; or FAA AD 71-17-5. Compliance: Within 10 hours time in service and thereafter at intervals not exceeding 50 hours time in service.