COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bell Helicopter Textron 212 Series Helicopters AD/BELL 212/35 Tail Rotor Trunnion Bearing Housing 9/86 DM Applicability: All model 212 S/N: 30501 to 30999 31101 to 31273 and 31275 32101 to 32142 32201 to 32262. Requirement: Action in accordance with Bell Alert Service Bulletin No. 212-86-39, Revision A. Compliance: Part I of the Requirement Document: Within 25 hours time in service or seven days whichever occurs first after 6 August 1986 and thereafter at intervals not exceeding 25 hours time in service or 7 days, whichever occurs first, until Part II is complied with. Part II of the Requirement Document: Within 150 hours time in service or 60 days whichever occurs first after 31 July 1986. Background: A trunnion bearing housing end web has been found below specified dimensions. Failure of the housing caused excessive tail rotor vibration and loss of control.