This paper describes initial measurements of the near wake of a 2-bladed teetering, untwisted, square-tipped rotor in forward flight. Issues of periodicity and repeatability of the core are studied using LDV and flow-visualization.

Core passage uncertainity is seen to be less than 1 degree of rotor revolution at 1050 rpm. Velocity measurements on the ABS of the rotor show wake-like core axial velocities higher than core-circumferential velocity for the first 180 degrees of vortex age. Both the axial and circumferential velocities approach 50% of the blade tip-speed. The inboard vortex sheet has substantial wake-like velocities and rolls up into a concentrated circulatory region opposite in sense to the tip-vortex, within 30 degrees from the blade. The fully-developed values of circulation, radius and axial velocity remain constant over the first 180 degrees of wake-age.