COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Fokker F28 Series Aeroplanes AD/F28/75 Fuselage Skin Lap Joint at Stringer 17/58 9/94 Applicability: F28 aircraft (except Mark 0100), all serial numbers. Requirement: Repair the fuselage skin lap joint between stringers 16 and 17 (58 and 59) in accordance with Fokker Service Bulletin (SB) F28/53-121 Revision 1. Note: RLD AD 91-022 refers. Compliance: 1. For aircraft modified in accordance with Fokker SB F28/21-16, repair before 32000 flights or before 15 February 1995, whichever occurs last. 2. For aircraft not modified in accordance with Fokker SB F28/21-16, repair before 48000 flights or before 15 February 1995, whichever occurs last. Note: This repair eliminates the need for further inspections in accordance with the F28 Structural Integrity Program, Part 1, item 53-30-08 (AD/F28/45 refers). Background: A Fokker evaluation has shown that current NDT methods are not effective at detecting small cracks in non-bonded dimpled riveted skin lap joints, such as the joint at Stringer 17/58. Therefore, as the cracks cannot reliably be detected, the RLD has determined that the Stringer 17/58 lap joint should be permanently repaired to avoid the possibility of joint failure and subsequent aircraft depressurisation.