COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Fokker F28 Series Aeroplanes AD/F28/50 Amdt 1 Boundary Layer Fence 10/86 Applicability: All model F28 with S/Nos 11092, 11093, 11111 to 11234, 11237 and 11238. Requirement: Action in accordance with Fokker S.B. F28/57-75, Rev. 1. Note: RLD AD 85-45 Rev. 2 refers. Compliance: Prior to 31 December 1987. Air-leakage through boundary layer fences results in a deterioration of the wing performance. Modified boundary layer fences provide labyrinth-type seals to overcome this problem. Amendment 1 of this Directive references Rev 1 of Fokker SB F28/57-75 which requires additional work.