A turbofan comprising a fan casing and a nacelle comprising a cowl translatable between an advanced position and a pushed-back position in which the mobile cowl and the fan casing define a window therebetween. The nacelle also comprises reverser flaps, each reverser flap being mounted in a linked manner on the mobile assembly between a closed position in which it obstructs the window and an open position in which it does not obstruct the window. The nacelle also has an impelling mechanism comprising a lever arm rotatable on the mobile assembly and having a roller, a connecting rod mounted rotatably between the reverser flap and the lever arm, and a channel receiving the roller, the channel having a front part parallel with the translation direction and a rear part extending after the front part and oriented inward as it progresses from the front toward the rear.