Abstract: A pitch change system (30) for varying the pitch of the blades (16) of a multi-bladed propulsor (10) comprises a pitch change actuation assembly (40) and a pitch change drive assembly (70) for selectively actuating the pitch change actuation assembly (70) whenever it is desired to change blade pitch. The pitch change actuation assembly (40) comprises a ballscrew (42), a ballscrew nut (44) threadably mounted to the ballscrew (42), and a pitch stop assembly (100) having a retractable feather stop (135) which in its normal position prevents the ballscrew (42) from driving the ballscrew nut (44) to move the blades (16) beyond the coarse pitch setting corresponding to blade feather, but in its retracted position permits the ballscrew (42) to drive the ballscrew nut (44) to move the blades (16) through feather to a desired reverse pitch setting.

Abstract: A pitch change actuation system for changing the pitch of the blades (16) of a prop-fan propulsor (10) comprises a translating pitch change actuator (30) and a flexible feather latch member (50) including a feather stop (56) and a feather latch (58), the feather latch member (50) being selectively releasable so as to permit the pitch change actuator (30) to drive the blades (16) through feather to a desired reverse pitch setting. Pitchlock lugs (96) and (98) operatively engage a pitchlock screw lug (97) on a pitchlock screw (80) to provide pitchlock screw stops at full reverse pitch and feather, respectively, with the pitchlock lug (98) being selectively displaceable so as to permit the pitchlock screw (80) to rotate when the pitch change actuator (30) is translated to drive the blades (16) through feather to reverse pitch.

Abstract: A propeller system has a pair of hub assemblies driven in counter-rotation, each hub assembly having a mechanical pitch change actuator, each actuator being provided with a pitch lock that rotates simultaneously with the motion of the actuator to allow the actuator to set propeller blade pitch, but locks the propeller blade positionally when not rotating simultaneously with the actuator, and a differential for transmitting a pitch change signal across a rotating gap between the two hub assemblies and for providing power to a means for providing the pitch change signals. A pair of motors provide the rotative signal to set the pitch of the blades in each hub assembly. One of the pair of motors drives the actuator towards high pitch and the other motor drives the actuator towards low pitch. A synchronizer coordinates the signals of the first and second motors so that a pitch lock moves simultaneously with the actuator.

Abstract: A mechanical pitch lock includes a pitch lock screw (60) that simultaneously rotates within an actuator (42) while the actuator moves to change the pitch of a propeller blade (16). While rotating simultaneously with the motion of the pitch actuator, the pitch lock screw maintains a longitudinal position allowing the actuator to move. If the pitch lock screw does not rotate simultaneously with the actuator, the pitch lock screw moves longitudinally with the actuator until it abuts a projection 66 thereby preventing further movement by the actuator.

Abstract: A modular, easily replaceable, pitch actuation system is removably secured within the hub of an aircraft. The modular system houses a driving system which provides a rotational output to set the pitch of propeller blades mounted to the hub, and a pitch changing system that controls the driving system. The driving system includes a high-speed, low-torque hydraulic motor that drives an harmonic drive to amplify the torque of the motor. The pitch changing system includes an actuator which positions a valve that controls the hydraulic motor, and a nulling gear which repositions the valve and acts as a pitch lock.

Abstract: An actuator (10) tolerant of ballistic damage thereto includes a piston (25) longitudinally reciprocable within a cylinder (15) and connected to a rod (30), the piston comprising a plurality of longitudinally stiff, circumferentially spaced ribs (35) joined by a bulkhead (40) which transfers hydraulic loading to the ribs and readily ruptures in response to impact with an obstruction (45) in the cylinder wall due to for example, ballistic damage to the actuator. The bulkhead carries a sealing ring (60) for sealing leakage around the piston and may be formed integrally with the ribs or separately therefrom and attached thereto as an end cap to the piston. Analogous structure may be employed in a gland (20) for the actuator to accommodate ballistic damage to the rod.

Abstract: An actuator (10) tolerant of ballistic damage thereto includes a piston (25) longitudinally reciprocable within a cylinder (15) and connected to a rod (30), the piston comprising a plurality of longitudinally stiff, circumferentially spaced ribs (35) joined by a bulkhead (40) which transfers hydraulic loading to the ribs and readily ruptures in response to impact with an obstruction (45) in the cylinder wall due to for example, ballistic damage to the actuator. The bulkhead carries a sealing ring (60) for sealing leakage around the piston and may be formed integrally with the ribs or separately therefrom and attached thereto as an end cap to the piston. Analogous structure may be employed in a gland (20) for the actuator to accommodate ballistic damage to the rod.

Abstract: The torque to the blades for pitch change movement of a variable pitch fan of the type having a harmonic pitch change actuator is increased by coupling both the outputs of the rigid spline and flexispline to drive the blade for pitch change movement.