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/F50/10 Outboard Nacelle Ventilation Air Inlets 3/89 DM Applicability: F27-050 S/Nos 20103 to 20108 and 20110 to 20128. Requirement: Action in accordance with Fokker SB F50-54-003. Note: RLD AD 88-94 refers. Compliance: Prior to 31 March 1989. Background: There have been several reports of ice build-up on cable systems. These occurred at high altitude and high humidity conditions with low OAT.