A three-dimensional droplet impingement code for aircraft propellers has been developed. The code allows the modeling of propellers of arbitrary geometry in three dimensions, but is limited to modeling axi-symmetric spinner / nacelles combinations. The code was used to analyze several 3-D wind tunnel propeller-nacelle models which were used to validate a theoretical relationship between two-dimensional and three-dimensional impingement efficiencies for rotating propellers. The effects of the spinner, engine nacelle geometry, contraction of the slipstream, and blade-to-blade interference on the impingement efficiency and limits of impingement were studied. Parametric studies of the effects of the advance ratio J and droplet size on the efficiencies and limits were performed.