COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Ayres Thrush (Snow) Commander Series Aeroplanes AD/AC-SNOW/12 Rudder Control Surface Upper Hinge - Inspection and Modification 6/79 Applicability: All model S-2D and S-2R with rudder assembly with single upper hinge P/N 54030- 87. Requirement: To prevent the possible separation of the single upper hinge from the rudder assembly accomplish the following: 1. (a) Remove rudder assembly from aeroplane. (b) Strip fabric and dope from area around upper hinge. (c) Inspect with 10X glass in and around weld head on upper hinge attachment for cracks. (d) If cracks are discovered comply with para. 2. 2. If cracks are discovered in the upper hinge area comply with one of the following options: (a) Replace rudder ith rudder P/N 54030-987 having triple upper hinges. (b) Modify existing rudder P/N 54030-87 by installing Ayres Custom Kit No. CK-AG-18; or (c) Replace defective rudder P/N 54030-87 with serviceable rudder P/N 54030- 87. Note: FAA AD 79-10-10 Amendment 39-3469 refers to this subject. Compliance: 1. Within 100 hours' time in service after 31 July 1979 and thereafter at intervals not exceeding 100 hours' time in service until para. 2(a) or (b) accomplished. 2. Modify in accordance with para. 2(a) or (b) not later than 300 hours' time in service after 31 July 1979. Background: There are three reports of failures of the single upper hinge type rudders on overseas aeroplanes.