Propeller outer slipstream control system for counter-rotating propellers
A counter rotating propeller system comprises a structure configured to control the front propeller outer slipstream and prop wash. Specifically disclosed is a structure configured to vary the effective hub-tip radius ratio of the rear propeller.
1. A method of controlling a counter rotating propeller system, the propeller system comprising a front propeller axially aligned with an axially spaced apart rear propeller, the method comprising the step of:
a. controlling a convergence of a prop wash of the front propeller by varying an effective hub to tip radius ratio of the rear propeller.
2. The method of claim 1 , wherein the step of controlling the convergence of the prop wash of the front propeller comprises controlling the convergence of the prop wash of the front propeller in response to changing flight conditions.
3. The method of claim 1 , wherein the step of controlling the convergence of the prop wash of the front propeller comprises deflecting an inner hub region prop wash outwardly.
4. The method of claim 1 , wherein the step of controlling the convergence of the prop wash of the front propeller comprises operating the counter rotating propeller system at its design point with respect to a position of the prop wash of the front propeller on the rear propeller.
5. The method of claim 1 , wherein the step of controlling the convergence of the prop wash of the front propeller comprises varying the effective hub to tip radius to cause the front propeller tip slipstream to pass coincident through the rear propeller tip through most of the counter rotating propeller system's operating regime.
6. The method of claim 1 , wherein the step of controlling the convergence of the prop wash of the front propeller comprises varying the effective hub to tip radius ratio to prevent unintended rear propeller tip stall.