COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Short SD3-30 Series Aeroplanes AD/SD3-30/21 Rudder Lower Bearing 5/87 Applicability: All models. Requirement: Action in accordance with Shorts SB SD3-55-05 R2 Part A. Compliance: At next scheduled inspection for Maintenance Release issue after 7 May 1987 and thereafter at intervals not exceeding 600 hours time in service or 6 months, whichever occurs first. Background: This requirement will reduce possible ice formation due to water ingress in the rudder lower bearing.