OMMONWEALTH 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/F100/9 Forward Partial Pressure Bulkhead 4/99 Applicability: F.28 Mk.0100 aircraft, serial numbers 11244 through 11286, 11289, 11291 through 11293, 11295, 11297, 11300, 11303, 11306 and 11308. Requirement: Install new doubler assemblies at the avionics cooling outlet valve fitting on the LH forward partial pressure bulkhead, in accordance with Part 1 of the Accomplishment Instructions of Fokker Service Bulletin (SB) F100-53-052 dated 17 January 1992 and at the cargo bay outlet valve fitting on the RH forward partial pressure bulkhead, in accordance with Part 2 of the Accomplishment Instructions of Fokker SB F100-53- 052 Revision 1 dated 7 June 1993. Note: RLD BLA 92-029/2(A) refers. Compliance: Unless previously accomplished, before accumulating 15,000 flight cycles since new. This Airworthiness Directive becomes effective on 22 April 1999. Background: During fatigue tests on the F.28 Mk.0100, cracks were found in the area of the avionics cooling outlet valve fitting. This AD requires a modification to prevent cracks developing in service and to improve the fatigue life of the affected structure to above 45,000 flight cycles.