US Patent 9242721 Aircraft propulsion system and a method of controlling the same

An aircraft propulsion system has a propulsive rotor assembly rotatable about an axis of rotation and comprising a plurality of blades and a rotationally fixed vane assembly located adjacent to the propulsive rotor assembly and arranged circumferentially around the axis of rotation. As airflow enters the propulsive rotor assembly, a portion of the airflow passes over the vane assembly which is configured to direct the airflow away from the rotor blades so as to reduce the relative velocity of the redirected airflow over the rotor blades. This results in a reduced tendency of the airflow through the propulsive rotor assembly to become choked.