A VTOL aircraft powerplant choosing between a low-power, turbofan mode during cruise flight and a high-power, lift fan mode during vertical flight. Turbofan mode is a gas turbine engine's shaft power driving a remote front fan. Its fan flow goes to thrust for cruising flight. During VTOL, front fan output enters a boost compressor. It produces the compressed air for a combustion chamber which feeds a large lift-fan turbine. That is the implementation of lift-fan mode. The boost compressor has more stages than the front fan and is a big added load. The gas turbine engine is supercharged to turn that added load: Part of the boost compressor output is taken during VTOL. This is a new version of the supercharging. During cruise flight, a low pressure turbine stage is bypassed to match the lesser load. That completes the apparatus for a variable-cycle VTOL engine.