COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Robinson R22 Series Helicopters AD/R22/23 Main Rotor Gearbox Ring Gear Bolts - Inspection and Modification Applicability: All R22 servo helicopters. 10/84 Requirement: Robinson service bulletin No. 43 dated 24 August 1984, or FAA AD 84-18-04 of 6 September 1984. Compliance: 1. Inspect in accordance with the Requirement Document. Within the next 15 hours time in service after 13 September 1984. Thereafter at intervals not exceeding 50 hours time in service from the last inspection. 2. Modify the main rotor gearbox in accordance with Robinson Kit No. KI-37 within the next 200 hours time in service after 13 September 1984. Note: When gearbox has been modified, inspection may be discontinued. Background: There have been cases of ring gear bolt breaking/head separation in main rotor gearbox during normal service.