A turbofan engine having a duct for a bypass flow and blades. Each blade is mobile between a stowed position and a deployed position. Each blade includes a rigid core a second, free end, and a sheath into which the core and the second end slide. Each sheath includes a first part which surrounds at least one part of the core and the second end, and an aileron which extends beyond the core facing the first part of the adjacent blade. The sheath is made of a flexible material such that the bypass flow causes the sheath to come into contact with the first part of the adjacent blade. A turbofan engine of this kind makes it possible to create blades whose production costs are low but whose aerodynamic behavior is effective.