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- 2/5 Induction Air Box Door - Inspection and Modification 9/73 Applicability: Model S-2A with S/Nos. 2001 to 2059. Requirement: 1. Inspection: Visually inspect the induction air box flapper door assembly, Pitts P/N 2-7112-7, for cracks in the welded areas. Note: This inspection may be performed by the pilot. 2. Modification: Install stiffener, Pitts P/N 2-7112-16, to the induction air box flapper door assembly in accordance with Pitts SL No. 2; or Pitts SL No. 2 - For Aircraft with more than 50 hours time in service from new. Compliance: 1. Inspection: Prior to first flight of each day until incorporation of the modification. 2. Modification: Within 100 hours time in service after 28 September 1973.