When a thin jet sheet exits from the tip of a straight wing in the spanwise direction, the wing experiences a lift augmentation. In many cases, lateral blowing causes a lateral displacement of the tip vortices, without complicating the vortex structure. In such cases, simple scaling laws for blowing intensity and lift augmentation have been found to hold. However, in some instances blowing also produces secondary vortices, which sometimes are associated with a breakdown of the scaling laws. Flow surveys for several tip jet configurations giving rise to multiple-vortex structures were conducted in a low-speed wind tunnel. An analysis of the near wake structure in such cases indicated that the presence of strong secondary vortices provided the mechanism for the scaling-law breakdown.