COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Beechcraft 90 and 65-90 (King Air) Series Aeroplanes AD/BEECH 90/30 Heater - Differential Pressure Switches and Fuse Replacement and Inspection Applicability: Models 65-90, 65-A90 and B90 S/Nos. LJ-1 to LJ-501. 10/72 Requirement: 1. Determine that the ventilation blower is operating. Operation of the heater is prohibited if the ventilation blower is not functioning. This determination may be made by checking for airflow out of the air distribution openings in the cockpit and/or by the sound of the blower. Note: The above inspection may be performed and certified for by the pilot in command. 2. Replace existing ventilation blower and combustion blower differential switches in accordance with Beechcraft SI No. 0500-412. 3. Inspect the heater fuse to determine that a standard fuse of proper value is installed in accordance with Beechcraft SI No. 0500-412. Compliance: For Para. 1 - Prior to each flight until incorporation of Paras. 2 and 3. For Paras. 2 and 3 - Within 100 hours' time in service after 3 October 1972.