A turbofan having a nacelle delimiting a duct for a bypass flow and including a fixed structure including a guide vane support with guide vanes, a mobile cowl movable in translation between an advanced position and a retracted position, arms, each one being mobile in rotation on the guide vane support between a stowed position and a deployed position and comprising a distal end and a proximal end, for each pair of adjacent arms, a flexible screen extending angularly between the two arms, and of which an exterior edge is attached to the guide vane support, and wherein the distal end of each arm is fixed along the interior edge, a link rod mounted articulated between the distal ends, actuators to cause the mobile cowl to move, and an operating system which moves each arm. Such an arrangement allows a reduction in weight.