Helicopter antitorque system using circulation control

For use in a helicopter having a fuselage elongated in a longitudinal direction, suspended beneath a main rotor, and extending aftward from the center of the main rotor through the rotor downwash to an aft end, an antitorque system usable at high flight speeds, comprising:

• a linear nozzle extending generally in the longitudinal direction along the fuselage on one side of it and oriented to discharge a sheet of fluid substantially tangentially to the fuselage and downwardly around it;
• a chamber within the fuselage, having a surface including an aperture, said chamber communicating with said linear nozzle, said surface having the shape of a portion of a cone whose axis is generally aligned with the longitudinal direction of the fuselage;
• a subsonic low-pressure-ratio fan oriented relative to said chamber so as to blow air into it and to maintain an overpressure within said chamber sufficient to produce a flow of fluid through said linear nozzle characterized by a momentum coefficient between 0.2 and 0.8, and a flow velocity between 2.5 and 4.5 times the velocity of the rotor downwash;
• a throttle in the form of a sleeve substantially in contact with said surface and conforming generally to the shape of said surface, having an opening, and mounted for rotation about said axis so that said opening overlaps said aperture to a chosen degree to obstruct the flow of fluid through said aperture to a chosen extent;
• and,
• a jet thruster located near the aft end of the fuselage, communicating with said chamber through said aperture to receive fluid from said chamber, and oriented to discharge the fluid laterally from the side of the fuselage opposite the side on which said linear nozzle is located so as to produce an antitorque reaction force when flight conditions render said linear nozzle ineffective for that purpose.

For use in a helicopter having a fuselage elongated in a longitudinal direction, suspended beneath a main rotor, and extending aftward from the center of the main rotor through the rotor downwash to an aft end, an antitorque system usable at high flight speeds, comprising:

• a linear nozzle extending generally in the longitudinal direction along the fuselage on one side of it and oriented to discharge a sheet of fluid substantially tangentially to the fuselage and downwardly around it;
• a chamber within the fuselage, having a surface including an aperture, said chamber communicating with said linear nozzle, said surface having the shape of a portion of a cylinder whose axis is generally aligned with the longitudinal direction of the fuselage;
• a subsonic low-pressure-ratio fan oriented relative to said chamber so as to blow air into it and to maintain an overpressure within said chamber sufficient to produce a flow of fluid through said linear nozzle characterized by a momentum coefficient between 0.2 and 0.8, and a flow velocity between 2.5 and 4.5 times the velocity of the rotor downwash;
• a throttle in the form of a sleeve substantially in contact with said surface and conforming generally to to the shape of said surface, having an opening, and mounted for rotation about said axis so that said opening overlaps said aperture to a chosen degree to obstruct the flow of fluid through said aperture to a chosen extent;
• and,
• a jet thruster located near the aft end of the fuselage, communicating with said chamber through said aperture to receive fluid from said chamber, and oriented to discharge the fluid laterally from the side of the fuselage opposite the side on which said linear nozzle is located so as to produce an antitorque reaction force when flight conditions render said linear nozzle ineffective for that purpose.