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/F50/43 Fuselage - Flight Compartment Window Frames -1 9/91 Applicability: All F50 aircraft. Serial numbers 20103 to 20108 inclusive and 20110 to 20122 inclusive. Requirement: Action in accordance with the Technical Requirements of Netherlands AD BLA 89-98, dated 25 August 1989. Compliance: Prior to accumulating 10,000 pressurization cycles. Background: During full-scale fatigue tests of the forward fuselage test article, cracks occurred on the outside edges of the flight compartment window frames. These edges are sharp, which creates local stress concentrations. This AD calls for reworking of the outside edges of the flight-compartment window-frames to introduce a 0.5 mm radius.