Propulsion assembly comprising: an inner casing (13); an outer casing (3); an inter-duct casing (15) delimiting a primary duct (12) between the inner casing (13) and an outer wall (14), and a secondary duct (16) between the outer casing (3) and an outer wall (17); a fan capable of generating an air flow (24) circulating from downstream to upstream in the secondary duct (16); the assembly further comprising: at least one duct (27) for bleeding air from said flow (24), this bleed duct (27) comprising an inlet port (28) in the outer wall (17) and an outlet port (29) in the inner wall (14); an outer flap (30) movable between an open position and a closed position of the inlet port (28); an inner flap (31) movable between an open position and a closed position of the outlet port (29).