COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bell Helicopter Textron 47 (All Variants) Series Helicopters AD/BELL 47/97 Main Rotor Flight Control System Bolts 2/90 Applicability: All models. Requirement: Action in accordance with Bell Alert Service Bulletin No 47-89-16. Compliance: At the next scheduled inspection for issue of a Maintenance Release after 30 March 1990 or by 30 June 1990, whichever occurs first. Thereafter, reinspect at intervals not exceeding 24 months calendar time. Background: Bell have advised that some of the rotating control bolts have been found corroded, fretting and/or with excessive wear on the bolt shank.