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 250/27 Compressor Bleed Valve Strainer - Installation 7/77 Applicability: Model 250-C20, -C20B, -B17 and B17B. Document: 1. Allison CEB 250-C20/C20B-1116; or 2. Allison CEB 250-B17/B17B TP CEB 1071; or 3. FAA AD No. 77-09-08. Compliance: Within 100 hours' time in service after 31 July 1977.