COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES AlliedSignal (Lycoming) Turbine Engines - T53 Series AD/T53/17 Centrifugal Compressor Impeller 3/86 Applicability: All model T5317A, T5313B and T 53-L-13B series engines with centrifugal Compressor Impeller P/N 1-100-078-07 and 08 installed. Requirement: Inspect impeller in accordance with Lycoming Service Bulletin No 0052. Compliance: 1. On T5313B and T53-L-13B series engines within 200 engine operating cycles on impellers that have accumulated 4600 cycles and thereafter at intervals not exceeding 500 cycles. 2. On T5317A engines within 200 engine operating cycles on impellers that have accumulated 3500 cycles and thereafter at intervals not exceeding 500 cycles. Background: This Directive is issued to reflect the manufacturers special inspection requirements, advised in LYC SB NO 0052, which are necessary to enable these impellers to achieve the maximum life limits advised in Service Bulletins No 0020 and 0034.