Off-design analysis of counter-rotating propeller configurations

An analysis is conducted to determine whether the counterrotating propeller configuration maintains, and perhaps improves, its excellent performance in the off-design mode for the constant-speed or variable-pitch case. While the twist distribution is maintained, the blade angle is changed to absorb shaft horsepower as a constant rpm setting is maintained under varying freestream velocities. A relatively flat propeller efficiency curve is obtained for advance ratios of 1.5-5.0.