COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES McDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters AD/HU 369/13 Main Rotor Blade - Inspection 10/74 Applicability: All 500 model 369H series. Document: Hughes SIN No. HN-73. Compliance: Within 25 hours time in service after 7 October 1974 and thereafter at intervals not exceeding 100 hours time in service.