COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Beechcraft 19, 23 and 24 Series Aeroplanes AD/BEECH 23/10 Wing Spar Lower Boom 4/66 Applicability: All models with Hawker de Havilland Kit No. 05-F-63 incorporated. Requirement: Action in accordance with Hawker de Havilland TNS Beech-Aus No. 5. Compliance: At 2500 hours total time in service and thereafter at intervals not exceeding 500 hours time in service after 1 September 1971.