Helicopter antitorque system using circulation control

摘要

An antitorque system for use in a helicopter produces antitorque moments with efficiency comparable to that of the tail rotor it is designed to replace. The antitorque forces are generated mainly from the main rotor downwash by the circulation control effect. The downwash is deflected laterally as it passes around the tail boom by a sheet of air continuously discharged tangentially to the surface of the tail boom on one side of it at velocities in the range 30 to 120 meters per second from slots extending longitudinally along the tail boom and having a width in the range 4 to 20 millimeters. The discharged air is supplied by a relatively low-pressure-ratio fan within the fuselage which directs a stream of air rearwardly into the tail boom. The tail boom is provided at its rear end with a laterally disposed aperture through which some of the fan-supplied air is discharged to create a direct jet thrust. The flow through the aperture is throttled to vary the antitorque moment for trim and maneuvering.