The invention relates to the field of fairings of aircraft propulsion units, and more particularly to an assembly comprising a longitudinal beam (31) configured to be mounted on a lateral of a turbofan (7) engine core (11), oriented parallel to a longitudinal axis (X) of the turbofan (7), an opening fairing (18) cowl (50) of the engine core (11) and a deployment mechanism (60) mounted on the longitudinal beam (31) to move the opening cowl (50) between an open position and a closed position.