The Williams FJ33 is an American family of turbofan jet engines intended for use in very light jet aircraft. The FJ33 is a scaled-down version of the FJ44 engine. The FJ33-5A is the latest version certified in June 2016.
Engine configuration is a single stage fan, with booster stage, driven by a two-stage LP turbine, supercharging a centrifugal HP compressor, driven by a single stage HP turbine. An annular combustor is featured.
The FJ33 has a dry weight of less than , overall diameter of , overall length, and produces between and static thrust. Specific fuel consumption at thrust (SLS, ISA) is understood to be .
Iran apparently reverse engineered a variant, and is using it as high endurance UAV powerplant.