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/F50/68 Lower Cowling By-Pass Duct Opening 11/95 Applicability: Fokker Aircraft B.V. Model F.27 Mk.050 series, serial numbers as listed in the requirement document. Requirement: Modify the air outlet opening of the engine by-pass duct in accordance with Fokker S.B. F50-71-041 dated 10 November 1993. Note: Dutch AD BLA 1995-065 (A) dated 30 June 1995 also refers. Compliance: Required within the next three (3) calendar months after the 12 October 1995, unless accomplished previously. Background: There have been a number of in-flight power fluctuations in the service experience of the Fokker Model F.27 Mk.050 series aircraft. In certain weather conditions ice can build up in the engine air intake leading to a loss of engine power as a result of ice ingestion. This Directive mandates the by-pass duct modification to reduce the possibility of ingestion of ice into the engine.