COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Airparts (NZ) Ltd. FU 24 Series Aeroplanes AD/FU24/40 Cockpit Ventilators - Modification 4/71 Applicability: Model FU24-950 and other FU24 Series aeroplanes fitted with Mod. AP55 Part A with cockpit ventilators to Mod. AP23 or similarly located air intakes. Requirement: Seal off subject cockpit ventilators. Compliance: Within 50 hours time in service after 19 April 1971.