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-8/56 Main Landing Gear Uplock Actuator Modification 12/98 Applicability: All DHC 8 aircraft, serial numbers 3 through 339, without Bombardier Modification 8/1828 incorporated. Requirements: Unless previously accomplished, install Bombardier Modification 8/1828 (Landing Gear - Redesigned Main Gear Uplock Actuator) on both left and right main landing gear in accordance with the instructions in Bombardier Service Bulletin 8-32-98, Revision C, dated 31 July 1998. Note: Transport Canada Airworthiness Directive CF-98-26 dated 26 August 1998 refers. Compliance: Within 12 months of the effective date of this Directive. This Airworthiness Directive becomes effective on 5 November 1998. Background: Operators are reporting incidents of main landing gears failing to extend when a down selection is made. The cause is attributed to failure of the gear uplock unit to disengage. The alternate extension system must then be used to extend the landing gear. This modification is introduced to improve the reliability of the gear uplock and minimise the risk of experiencing landing gear hang up.