turbine and a five-stage compressor driven by the single-stage high-pressure turbine. Notably, the engine has two bypass channels which are located at the front and rear of the first compressor stage of the high-pressure spool, also known as the core-driven fan stage; these two bypass channels are key to the engine's variable cycle operation. The annular combustor is a double-dome design. The high and low-pressure spools are counter-rotating, which eliminates the stationary vanes between the turbines and reducing the number of parts and decreasing weight. The engine is controlled by a three-channel fuel-cooled full authority digital engine control (FADEC) system. Variable cycle The YF120's variable cycle system worked by varying the bypass ratio of the engine for different flight regimes, allowing the engine to act like either a low bypass turbofan or nearly a turbojet. As a low bypass turbofan (like competitor F119), the engine performed similarly to comparable engines, with the aft bypass channel behind the core-driven fan stage open. When needed, however, the engine could direct more airflow through the hot core of the engine (like a turbojet) by closing the aft bypass channel, increasing the specific thrust of the engine. This made the engine more efficient at high altitude, high thrust levels than a traditional low bypass turbofan. Fan-to-core pressure matching was performed by a variable area bypass injector (VABI). An expected disadvantage of this variable cycle system would be increased complexity and weight. GE claims to have combated this by using simple pressure driven valves rather than complex mechanically actuated valves to divert airflow. GE stated that this system resulted in the variable cycle system adding only 10 lb to the engine. Additionally, a production F120 engine was expected to have 40% fewer parts than the F110 engine. Nozzle The YF120 had different nozzle designs for the YF-22 and YF-23 technology demonstrator prototypes tailored to the specific airframe. The engine for the YF-22 featured a two-dimensional thrust vectoring nozzle that could vector in the pitch direction. This capability gave the aircraft a serious advantage in pitch agility by greatly increasing the amount of nose pitching moment available to the aircraft. The pitching moment is traditionally generated by the horizontal stabilizer (and/or canard, if applicable), but with a thrust vectoring nozzle that moment can be augmented by the thrust of the engine. During high AoA demonstrations, the YF120-powered YF-22 flew at trimmed AoA of 60 degrees at