Experiments are performed on an elliptic circulation control aerofoil in an open-jet wind tunnel facility. The influence of blowing from a single trailing-edge slot on the external flow is assessed using two-component particle image velocimetry (PIV) and steady surface pressure measurements. The test section configuration (open jet or closed wall) significantly affects the leading-edge region of the flow field. PIV is also used to measure the curved wall jet and its interaction with the external flow near the trailing edge. PIV measurements of the curved wall jet reveal mean tangential velocity similarity in the outer region of the flow above the location where the tangential velocity reaches a local maximum. The length and velocity parameters required for similarity scale with the product of the chord Reynolds number and the momentum coefficient in accordance with the recent publication by Stalnov, Kribus & Seifert (J. Renew. Sustain. Energy, vol. 2, 2010, p. 063101). The separation location is also a function of the product of these parameters. The dataset is used to assemble equations to predict the similarity length scales, velocity scales and separation location. These equations compare well with the present measurements.