COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Fokker F50 (F27 Mk 50) Series Aeroplanes AD/F50/45 Fuselage Power Supply Box Surround Structure 10/91 Applicability: Serial numbers 20103 to 20108 inclusive and 20110 to 20131 inclusive. Requirement: Action in accordance with the Technical Requirements of RLD AD 89-130, dated 27 October 1989. Note: Fokker Service Bulletin F50-53-024, dated 25 October 1989 refers. Compliance: Prior to exceeding 15 000 pressurisation cycles. Background: During full-scale fatigue testing, cracks occurred in the aircraft skin near the door hinge of the external power supply box. To improve the fatigue life of the skin in this area this AD calls for the installation of a reinforcement plate.