COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Pitts S-1 and S-2 Series Aeroplanes AD/PITTS S-2/1 Horizontal Stabiliser - Modification 6/73 Applicability: All model S-2A. Requirement: Modify horizontal stabiliser structure in accordance with Pitts SB No. 7 dated 12 March 1973. Compliance: Before issue of a Certificate of Airworthiness.