Abstract: A convertible aircraft engine, capable of turboshaft and/or turbofan modes of operation, is provided in a configuration that combines certain components to permit variation in bypass flow to match engine airflows with the mode of engine operation. The provided components permit the engine to decrease the power requirements of the engine's forward fan when the engine is operated in the turboshaft mode. To permit a decrease in fan power requirements, the fan is split into an outer portion and an inner portion separated by a rotating shroud. Airflow into the fan's outer portion is controlled with a part span inlet guide vane and an outlet guide vane. The guide vanes can be used to lessen the load on the outer portion of the fan while the inner portion continues to accelerate and compress a normal airflow into an engine compressor for supplying the engine's core. The power normally used to drive the fan outer portion is used instead to power a transfer shaft in the turboshaft mode.