COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 737 Series Aeroplanes AD/B737/74 Thrust Reverser Actuator Piston Seal 2/93 DM Applicability: Boeing 737-300,-400 and -500 series aeroplanes as listed in Boeing Service Bulletin 737-78A1055, dated 2 April 1992. Note: FAA AD 92-24-04 refers. Requirement: Action in accordance with Boeing Service Bulletin 737-78A1055 dated 2 April 1992. Compliance: By 1 January 1994. Background: Analysis by the manufacturer indicates that a potential exists for leakage across the piston seal in the thrust reverser actuator. The actions specified in this AD are intended to prevent uncommanded deployment.