COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Allison Turbine Engines - 250 Series AD/AL 250/12 Amdt 2 Pc Filter Flanged Insert - Inspection 1/71 Applicability: All "Blue Ribbon" Allison 250-C18 series. Document: Allison 250 CEB-112, Rev. 1. Compliance: Within 25 hours' time in service after 12 January 1971 and thereafter at intervals not exceeding 25 hours' time in service until the insert is installed with EPOXYLITE 814.