Abstract: An adaptive fan system for a variable cycle turbofan engine having at least one turbine, includes a shaft structured to receive mechanical power from a turbine in the variable cycle turbofan engine and a first fan stage that is coupled directly to the shaft and is driven directly by the shaft. A transmission system is coupled to the shaft and a second fan stage is coupled to the shaft via the transmission system and is driven by the shaft via the transmission system. The transmission system is structured to selectively vary a speed between high and low speeds at which power is supplied from the shaft to the second fan stage relative to at least one of the shaft and the first fan stage, wherein the first fan stage and the second fan stage are configured to rotate in the same direction and at the same high speed to increase the mechanical power of the turbine.

Abstract: One embodiment of the present invention is a unique gas turbine engine. Another embodiment is a unique variable cycle gas turbine engine. Another embodiment is a unique adaptive fan system for a variable cycle turbofan engine having at least one turbine. Another embodiment is a unique method for operating a variable cycle gas turbine engine. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for gas turbine engines and related systems.