Counter-torque device with rotor and flow straightening stator, both of which are ducted, and inclined flow-straightening vanes

Counter-torque device for a helicopter, comprising a variable-pitch multi-blade rotor mounted so that it can rotate substantially coaxially in a duct for a flow of air of axis substantially transversal to the helicopter and passing through a fairing incorporated into a tail part of the helicopter, so that the pitch change axes of the blades move in a plane of rotation substantially perpendicular to the axis of the fairing duct, as well as a flow-straightening stator fixed into the duct downstream of the rotor and including stationary vanes located substantially in a star configuration about the axis of the duct and each exhibiting an asymmetric aerodynamic profile, of which the camber and the angular setting with respect to the axis of the duct are such that the vanes straighten out the airflow downstream of the rotor substantially parallel to the axis of the duct, wherein the vanes of the flow-straightener are each inclined equally to the radial direction from the axis of the duct towards its periphery and in the opposite direction from the direction of rotation of the rotor, and inclined equally at a slant from the centre of the duct to its periphery and which slant is from upstream to downstream of the duct, and wherein the vanes of the flow-straightener are evenly distributed around the duct axis and support inside the duct a body which is substantially coaxial with the duct, and containing members for driving the rotor and members for collectively controlling the pitch of the blades of the rotor, which rotor is mounted so that it can rotate on the body.