the invention relates to a variable area nozzle for a turbo - jet engine . this nozzle comprises a convergent portion , formed by a fixed semi - shell and a semi - shell pivotal about a diametral axis ; the fluid - tightness of the convergent portion is ensured by a substantially semi - circular seal and by two longitudinal seals . the nozzle can be used for example with an engine comprising a partial re - heat system of moderate output .