US Patent 9605557 Variable bypass turbofan engine

A variable bypass turbofan engine includes a bypass fan having a plurality of bypass fan blades mated to a first low pressure shaft segment. A second low pressure shaft segment includes a low pressure compressor and a low pressure turbine mated thereto. The engine also includes a clutch coupled between the first low pressure shaft segment and the second low pressure shaft segment and is configured to selectively couple and decouple the first low pressure shaft segment from the second low pressure shaft segment. A brake is configured to selectively halt or oppose rotation of the first low pressure shaft segment or the bypass fan.