Air Propulsion

This paper describes experiments with propellers proving that the accepted screw theory of air propulsion does not accord with the facts. Air is impelled by a propeller at a speed approaching twice the screw advance for small blade angles, hence the theory of reflection or batting action should replace the screw theory. Thrust is shown to be due in greater degree to velocity and less to blade disk area than is commonly supposed. A method of predicting the complete flying performance of a propeller from a single static test of an accurate model is indicated.