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/F50/26 Amdt 1 Forward Passenger Door Frame to Torsion Box Connection 5/92 Applicability: Serial numbers 20103 - 20152 inclusive. Requirement: 1. Inspect in accordance with Part 1 of Fokker SB F50-53-031, dated 23 July 1990. Note: RLD AD(BLA) 90 - 089 refers. 2. For aircraft serial numbers 20103 and 20108 to 20152 inclusive, accomplish Part 2 of Fokker SB F50-53-031, dated 23 July 1990. 3. For aircraft serial numbers 20104 to 20107 inclusive: (a) Accomplish SB F50-53-005. Note: RLD AD (BLA) 89-58 refers. (b) Accomplish Part 3 of Fokker SB F50-53-031. Compliance: For paragraph 1. Prior to accomplishing paragraphs 2 or 3. For paragraph 2. Prior to accumulating 20 000 flight cycles. For Paragraph 3. Prior to accumulating 10 000 flight cycles Background: Full scale fatigue tests revealed cracks in frame 4110 near the connection to the upper torsion box above the forward passenger entrance door. The original issue of this Directive required the installation of a steel reinforcement plate. Subsequent fatigue tests revealed even this connection to have an insufficient fatigue life. This amendment requires an additional reinforcement which should give the structure above the passenger door a crack-free life of 45 000 flight cycles.