The helical flow is generated by a jet from a single nozzle inflowing tangentially into a pipe. The effect of the distance travelled by the air in the pipe from its tangential inlet to its axial outlet on the issuing jet is investigated. The axial and tangential velocity distributions were measured at the outlet cross-section of the pipe using the hot-wire probe. It was observed that for a short pipe the strongest asymmetry of the tlow velocity distributions exists for a part of the pipe crosssection near the pipe wall. Contrary to this, for a long pipe, the largest deviations from axisymmetry appear in the middle part. In this result the total effect of asymmetry expressed by RMS of swirl number considerably decreases.