During the 1950s and early 1960s Pratt & Whitney (Canada) experimented with small gas turbine engines. As a result the simple and highly reliable PT-6 was certified in December 1963 at 500 shp.
They have been built in both turboshaft and turboprop forms, and are still in production.
Over 52,000 have been built since 1963 for over 130 applications. Ours is an early A-20 of 500 shp, but most modern ones are rated at 1,150 shp, with a few going as high as 1,750 shp.