COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Hiller UH-12 Series Helicopters AD/HILLER 12/37 Soloy Conversion: Power Turbine Governor Control System - Modification Applicability: All Soloy turbine conversion UH12D/E and E (4 Place) helicopters. Requirement: Soloy Conversions S.B. 06-560. Compliance: Prior to the issue of the next Maintenance Release after 30 June 1985. 6/85 Background: The design, applicable prior to the issue of the Requirement Document, could result in loss of collective pitch control. This modification includes a spring bungee unit that will allow the collective lever to operate independently, if the governor cable seizes.