COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES SAAB SF340 Series Aeroplanes AD/SF340/37 Fuselage Structure Protective Shield 13/92 Applicability: 1. SAAB SF340A Serial Number 004 to159 inclusive. 2. SAAB SF340B Serial Number 160 to 252 inclusive. Requirement: Action in accordance with the technical requirement of SAAB 340 Service Bulletin number SAAB 340-53-028 Mod 1948 dated 20 August 1992. Note: Swedish Airworthiness Directive No. 1-055 issued 4 September 1992 refers. Compliance: No later than 3 000 flight hours after 10 December 1992. Background: Leakage of hot air from the Air Cycle Machine and ducts may cause damage to the structure. Should this continue for a prolonged time, the structure would be weakened below an acceptable level.