COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Fokker F27 Series Aeroplanes AD/F27/101 Cowlings - Gearbox Access Door - Modification 11/80 Applicability: All model F27 with S/Nos. as detailed in Fokker F27 SB No. F27/71-27. Document: Fokker F27 SB No. F27/71-27. Compliance: Before 1 June 1981. Background: SB No. F27/71-27 introduces a modification designed to prevent departure of the aeroplane with an unlocked gearbox access door.