Rolls-Royce Allison T56 is a single shaft, modular design military turboprop with a 14 stage axial flow compressor driven by a four stage turbine. It was originally developed by the Allison Engine Company for the Lockheed C-130 transport entering production in 1954. It is now produced under Rolls-Royce which acquired Allison in 1995. The commercial version is designated 501-D. With an unusually long and numerous production run, over 18,000 engines have been produced since 1954, logging over 200 million flying hours.