COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bell Helicopter Textron 412 Series Helicopters AD/BELL 412/4 Amdt 1 Main Rotor Yoke - Inspection, Retirement and Modification 2/83 Applicability: As specified in requirement documents. Document: Bell Alert Service Bulletin No. 412-82-6; and Bell Alert Service Bulletin No. 412-82-8; and Bell Alert Service Bulletin No. 412-82-9. Compliance: As specified in requirement documents. Background: This Directive follows action recommended by the manufacturer relating to cracking of the main rotor titanium yoke.