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A system for adjusting the pitch of a counter-rotating propeller has a propeller shaft, a forward propeller driven by the propeller shaft, and an aft propeller connected with the forward propeller. The forward propeller has a hub, blades mounted within the hub, and an actuator connected with an end

A system for adjusting the pitch of a counter-rotating propeller has a propeller shaft, a forward propeller driven by the propeller shaft, and an aft propeller connected with the forward propeller. The forward propeller has a hub, blades mounted within the hub, and an actuator connected with an end of the blades. The aft propeller has a hub, blades mounted within the hub, and a cam assembly connected with an end of the blades. The actuator of the forward propeller has a forward end and an aft end, wherein the aft end is connected with the cam assembly of the aft propeller. Thus, when the actuator moves in an axial direction, the cam assembly moves relative to the actuator and the pitch of the forward propeller blades and the pitch of the aft propeller blades are simultaneously adjusted.

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1. A system for adjusting pitch of a counter-rotating propeller, the system comprising: a propeller shaft;a forward propeller driven by the propeller shaft, the forward propeller having a forward hub, forward propeller blades mounted within the forward hub; andan aft propeller connected with the for

1. A system for adjusting pitch of a counter-rotating propeller, the system comprising: a propeller shaft;a forward propeller driven by the propeller shaft, the forward propeller having a forward hub, forward propeller blades mounted within the forward hub; andan aft propeller connected with the forward propeller, the aft propeller having an aft hub, aft propeller blades connected to the aft hub, and a cam assembly within the aft hub connected with an end of the aft propeller blades; andan actuator within the forward hub connected with an end of the forward propeller blades, the actuator having a forward end and an aft end, wherein the aft end is connected with the cam assembly and, when the actuator moves in an axial direction, the pitch of the forward propeller blades and the pitch of the aft propeller blades are adjusted simultaneously. 2. The system of claim 1, wherein when the actuator moves in a first axial direction, the cam assembly moves in the first axial direction, and the pitch of the forward propeller blades and the pitch of the aft propeller blades decrease; and when the actuator moves in a second axial direction, the cam assembly moves in the second axial direction, and the pitch of the forward propeller blades and the pitch of the aft propeller blades increase. 3. The system of claim 1, wherein the aft propeller is connected with the forward propeller assembly with a gear system that allows the forward propeller assembly to rotate in a first direction while the aft propeller assembly rotates in a second direction. 4. The system of claim 3, wherein the forward propeller assembly rotates at a first speed and the aft propeller assembly rotates at a second speed. 5. The system of claim 4, wherein the second speed is between about 85% and 115% of the first speed. 6. The system of claim 3, wherein the gear system is a planetary gear system having a sun gear mounted to the propeller shaft. 7. The system of claim 1, the cam assembly comprising: a push-rod for connecting the cam assembly to the aft end of the actuator. 8. The system of claim 1, the cam assembly comprising: a slot; anda cam, wherein when the actuator moves in the axial direction, the cam moves in the axial direction in the slot. 9. The system of claim 1, wherein the actuator is selected from the group consisting of mechanical actuators and hydraulic actuators. 10. The system of claim 9, wherein the actuator is a mechanical actuator. 11. The system of claim 10, wherein the actuator is a nut of a ball screw having a threaded portion that rotates to move the nut in the axial direction. 12. The system of claim 11, and further comprising: a motor; anda gear train having a pinion gear driven by the motor and a gear mounted on a first end of the ball screw for rotating the threaded portion of the ball screw. 13. The system of claim 11, wherein the nut has a push-rod connected at an end of the nut near the aft propeller assembly. 14. A system for adjusting pitch of a counter-rotating propeller, the system comprising: a propeller shaft;a forward propeller driven by the propeller shaft and rotating in a first direction, the forward propeller comprising: a forward hub; andforward propeller blades mounted within the forward hub;an actuator within the forward hub connected with an end of the forward propeller blades;an aft propeller driven by a gear train having a gear mounted to the propeller shaft, the aft propeller rotating in a second direction and comprising: an aft hub; andaft propeller blades connected to the aft hub;a cam assembly within the aft hub connected with an end of the aft propeller blades; anda push-rod connecting the cam assembly with an aft end of the actuator, wherein when the actuator moves in a first axial direction, the push-rod moves the cam assembly in the first axial direction to simultaneously decrease the pitch of the forward propeller blades and the pitch of the aft propeller blades, and when the actuator moves in a second axial direction, the push-rod moves the cam assembly in the second axial direction to simultaneously increase the pitch of the forward propeller blades and the pitch of the aft propeller blades. 15. The system of claim 14, wherein the push-rod extends axially from the aft end of the actuator, through the gear train, and connects to the cam assembly. 16. The system of claim 14, wherein the actuator is a nut of a ball screw having a threaded portion that rotates to move the nut in the axial direction. 17. The system of claim 14, the cam assembly comprising: a slot; anda cam, which moves in the first axial direction within the slot when the actuator moves in the first axial direction, and moves in the second axial direction within the slot when the actuator moves in the second axial direction. 18. A method of adjusting the pitch of a counter-rotating propeller, the method comprising: driving a propeller shaft to rotate a forward propeller in a first rotational direction and an aft propeller in a second rotational direction, wherein the forward propeller includes a hub, blades, and an actuator connected with the forward propeller blades and the aft propeller includes a hub, blades, and a cam assembly connected with the aft propeller blades;moving the actuator in a first axial direction;moving a cam assembly at an aft end of the actuator in the first axial direction while the actuator moves in the first axial direction to simultaneously decrease the pitch of the blades of the forward propeller and the pitch of the blades of the aft propeller;moving the actuator in a second axial direction; andmoving the cam assembly in the second axial direction while the actuator moves in the second axial direction to simultaneously increase the pitch of the blades of the forward propeller and the pitch of the blades of the aft propeller. 19. The method of claim 18, wherein the actuator comprises a mechanical actuator or a hydraulic actuator. 20. The method of claim 19, wherein the actuator is a nut of a ball screw having a threaded portion that rotates to move the nut in the first axial direction and the second axial direction.