ON THE INDUCED DRAG REDUCTION DUE TO PROPELLER-WING INTERACTION

The aerodynamic interaction between a wing and a couple of propellers in tractor configuration is investigated by means of a model based on the lifting line concept and under the assumption of quasi-steady incompressible motion of inviscid fluid. The ways the propellers influence the wing performances, particularly the induced drag, are analysed. It turns out that the lift increase and the possible drag reduction depend strongly on the direction of the blade rotation and on the propeller distances from midspan, and result from two main effects: the direct propeller induction on the wing and the modification of the lift distribution along the span. An additional nonlinear (mixed) contribution affects the drag but has only negligible influence on the lift. The described model allows one to evaluate separately all these effects and helps understanding their-influence on the global modification of the wing performances.