COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES DHC-2 (Beaver) Series Aeroplanes AD/DHC-2/18 Tailplane Rear Spar - Inspection and Modification 7/77 Applicability: All models. Document: De Havilland Aircraft of Canada SB No. 2/19. Compliance: Initially inspect within 25 hours time in service after 8 July 1977 and thereafter as per requirement document.