COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Gates Learjet 24 & 25 Series Aeroplanes AD/LEARJET/20 Upper Cabin Door Lock Mechanism Bolts - Modification Applicability: All model 24 with S/Nos. 24-100 to 24-357, All model 25 with S/Nos. 25-003 to 25-291. 3/80 Requirement: Modify the upper cabin door lock mechanism bolts by installing Gates Learjet Kit No. AMK 79-9. Compliance: Within 150 hours time in service after 30 April 1980. Background: Modification kit AMK 79-9 provides an additional safety feature to the upper cabin door lock mechanism by installing drilled bolts and lockwiring these bolts in situ.