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/F50/44 Fuselage - Flight Compartment Window Frames -2 9/91 Applicability: All F50 aircraft serial numbers 20103 to 20108 inclusive; 20110 to 20149 inclusive, 20151 to 20155 inclusive, 20159 and 20160. Requirement: Action in accordance with the Technical Requirements of Netherlands AD BLA 90-002, dated 10 January 1990. Compliance: Prior to accumulating 15,000 pressurization cycles. Background: Full-scale fatigue tests indicated cracks occurring in the edges of the window frames. These edges are sharp, which creates local stress concentrations. To remove these stress concentrations, AD/F50/43 was issued, calling for outside edges of the flight compartment window frames to be modified around the sliding windows and the direct vision windows. This AD calls for a similar modification to the outside edges of the windshield frames and reinforcing plates to be installed to the window frames of the sliding windows, direct vision windows and windshields.