COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Casa 212 Series Aeroplanes AD/CASA/20 Corrosion of Rudder Torsion Tube 9/96 DM Applicability: All models. Requirement: Action in accordance with CASA SB 212-27-34. Note: Spanish DGAC AD 06/96 refers. Compliance: Before 30 August 1996. Background: Corrosion has been detected in the rudder lower shaft and support structure. This has been caused by water entry through the space between the upper bearing and the fuselage structure.