One of the most powerful tools in an analysis of aircraft icing is the knowledge of where the water in a given cloud will impinge on a surface. The determination of where a structure will accrete ice is expressed by the impingement efficiency, b. An improvement to the dye-tracer method for the experimental determination of impingement efficiency is presented. The improved method, which saves both time and expense, was then used to determine the impingement efficiency on a four-bladed, constant chord propeller with a nacelle. The propeller impingement tests showed the limitations of the current droplet impingement test techniques and found impingement efficiencies greater than one for a large portion of the propeller blade. Using blade-element theory it is shown how impingement efficiencies greater than one can occur for the case of a propeller. Suggestions are also made as to how the dye-tracer test method can be improved.