COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Fokker F100 (F28 Mk 100) Series Aeroplanes AD/F100/2 Main Landing Gear Downlock - Inspection/Replacement 1/99 Applicability: F28 Mk. 100 aircraft all serial numbers, fitted with Dowty Aerospace Hydraulics MLG Downlock Actuators (Jack & Springpot Units) Part Number (P/N) 201218001, P/N 201218002, P/N 201218003, or P/N 201218004, all serial numbers. Requirement: 1. Inspect the applicable MLG Downlock Actuator in accordance with Fokker Service Bulletin SB F100-32-072 dated 30 March 1993 and in accordance with Dowty Aerospace Hydraulics SB F100-32-505 dated 24 March 1993. 2. Replace MLG Downlock Actuator in accordance with the Aircraft Maintenance Manual Chapter 32-32-05 and return the defective unit to the manufacturer for further analysis. Note: RLD Airworthiness Directive 93-052 (A) dated 23 April 1993 refers. Compliance: 1. At intervals not to exceed 1250 flight hours. 2. Following failure to meet the requirements of the inspection at requirement 1 above. This Airworthiness Directive becomes effective on 28 January 1999. Background: In service experience had revealed arisings of landing gear "unsafe" warnings which had been attributed to MLG Downlock actuator internal failures. This Directive is issued to introduce regular inspections to ensure correct operation of the MLG Downlock actuators.