COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Instruments and Automatic Pilots AD/INST/19 ARC PA 500A Actuators - Cessna Auto Pilot, AFCS & Yaw Damper - Inspection and Modification Applicability: ARC PA500A actuators S/Nos. 6265 and below. Document: 1. ARC Field Engineering SB No. 181; or 2. Cessna Avionics SL AV75-10; or 3. FAA AD 76-04-03. 6/76 Compliance: Inspection - within 100 hours time in service after 30 July 1976 and thereafter at intervals not exceeding 100 hours time in service until actuator is modified. Modification -Before 30 April 1977.