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/31 Handling Qualities and Aerodynamic Stall Characteristics - Modification Applicability: All model 23 with S/Nos 23-003 to 23-099. All model 24 with S/Nos 24-100 and subsequent. All model 25 with S/Nos 25-003 to 25-061. 25-067 to 25-201. 25-204 and subsequent. 7/85 With unmodified wings. Requirement: 1. Install modification kit AMK 83-4, or 2. Install modification kit AMK 84-5. Note: FAA AD No 80-19-11 R1 refers. Compliance: Before 1st October, 1986. Background: GLC and the FAA have recently found evidence of undesirable handling characteristics at the limits of the flight envelope.