QPROP: propeller/windmill analysis and design. PROP is an analysis program for predicting the performance of propeller-motor or windmill-generator combinations. QMIL is a companion propeller/windmill design program. QPROP’s output is entirely in tabular text format, and is typically used in conjunction with the user’s own plotting programs. It is intended for large-scale parametric sweeps, driven manually or via batch execution.