A turbofan engine with a nacelle including a runner translationally mobile between advanced and back-off positions to open a window between a stream and an outside, a plurality of blades, each rotatable on the runner between retracted and deployed positions, and a maneuvering system displacing each blade and comprising, for each blade, a shaft rotatable on the runner and to which the blade is fixed, and a toothed segment on the shaft, and a toothed arc rotatable on the runner about a longitudinal axis, the tooth arc teeth meshing with the toothed segment teeth, a slip translationally mobile on the runner in a plane at right angles to the longitudinal axis between first and second positions, a connecting rod mounted articulated between the slip and the toothed arc, a rib integral to the fixed structure, and a guiding U integral to the slip and which straddles the rib.