Unducted-Fan Engine

Unducted-fan (UDF(TM) engine advanced counterrotating-pusher-propeller propulsion system for high-subsonic (mach 0.7 to 0.85) aircraft. Combines modern high-pressure-ratio gas-turbine engine with multistage counterrotating power turbine directly coupled to counterrotating, advanced high-speed propellers. Key feature of system is unique direct turbine drive eliminating need for gearbox to transmit power to propeller blades.