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/15 Refrigeration System Condenser Fan - Inspection and Replacement 7/77 Applicability: Model 24 with S/Nos. 24-100 to 24-356. Model 25 with S/Nos. 25-002 to 25-253. And any 23/24 or 25 Series Learjet which has had a Condenser Fan changed since 1 July 1977. Requirement: 1. Inspect the P/No. rubber-stamped on a blade of the refrigeration condenser fan. 2. If the fan bears the P/No. 6608059-3, attach a placard worded as follows to the instrument panel adjacent to the refrigeration system control switch: WARNING DO NOT OPERATE REFRIGERATION SYSTEM UNDER ANY CIRCUMSTANCES ON THE GROUND OR IN THE AIR UNTIL FAN HAS BEEN REPLACED. Note: The correct fans have blades which taper in thickness towards the tip and bear the P/Nos. 6608059-2 or 6608059-4. or Gates Learjet SB 23/24/25-284. Compliance: Before further flight after 31 July 1977.