The Problem of the Propeller in Yaw with Special Reference to Airplane Stability

The quantity of air which the disk area described by propeller blades travels through, is accelerated rearward conformably to the momentum of the forces acting on the propeller. The accelerated air mass forms behind the propeller the so-called slipstream, in which among others, the mean velocity of advance is increased. If the propeller axis slopes toward the relative flight direction, the slipstream direction likewise changes, i.e., it sets up a downwash behind the propeller. It was shown how this deviation can be mathematically defined. With appreciable slope the momentum of the slipstream is partially split up in the surrounding air because of the circulation, and the downwash of the slipstream is diminished.