COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Aerospatiale (Socata) TB20 (Trinidad) Series Aeroplanes AD/TB20/23 Console Attachment 11/91 Applicability: Model TB20 and TB21 with serial numbers 1 through 1286. Requirement: Action in accordance with the Technical Requirement of DGAC AD 91-160 (A). Note: SOCATA TB aircraft SB 49 refers. Compliance: Within 50 hours time in service after 31 October 1991, and thereafter at intervals not to exceed 200 hours time in service; until Kit No. 9172 is installed. Background: Cracks have been reported on frame No. 0 at the nose gear mount lower attachments.