COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes AD/DHC-8/17 Flap Ballscrews 12/91 DM Applicability: All model DHC-8 aircraft with serial numbers 3 through 216. Requirement: Action in accordance with the technical requirements of Transport Canada AD CF- 91-34. Compliance: Within 50 hours time in service after 4 November 1991. Background: It has been found from recent test programs carried out on DHC-8 aircraft at de Havilland that the flap loads may not be evenly distributed into the flap ballscrews. This condition, if not corrected could lead to accelerated wear, reduced fatigue life and possible overloading of the flap structure which could ultimately result in an asymetric flap condition.