COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Airbus Industrie A319, A320 and A321 Series Aeroplanes AD/A320/37 Thrust Reverser Check Valve Replacement 7/94 Applicability: All A320 aircraft not incorporating Airbus Industrie modification 22537 or SB A320- 29-1048 R1. Requirement: Action in accordance with Airbus Industrie Service Bulletin A320-29-1048 R1. Note: DGAC AD 94-059-054(B) dated 16 March 1994 refers. Compliance: No later than 31 December 1994. Background: Airbus Industrie advise that this action is required to prevent pressurisation of the Hydraulic Control Unit return line in the event of failure in the closed position of the check valve in the thrust reverser hydraulic return line.