Aerial vehicles are equipped with propellers having clutch mechanisms that contract around a shaft when the propellers are not rotating, or are rotating at low angular velocities, and expand around the shaft when the propellers are rotating at sufficiently high angular velocities. The clutch mechanisms surround one or more fixed posts within an opening or window defined therein. When the clutch mechanisms contract into a closed position, components of the clutch mechanisms come into contact with the posts, and the propellers are forced to remain in an alignment defined by the posts. When the clutch mechanisms expand into an open position, such components may rotate freely without contacting the posts. The clutch mechanisms cause propellers to remain aligned in desired orientations when the propellers are not required for operation, thereby reducing drag or adverse acoustic effects.

An unmanned aerial vehicle includes a propulsion system having at least one propulsion module comprised of at least one propeller and at least two motors/engines, one or more of the motors/engines providing mechanical energy to drive the propeller, wherein the difference between the angular velocities of the motors/engines provides energy input to a mechanical or magneto-mechanical linkage system to change the blade pitch angle of the propeller, in cyclic and/or collective manner.

An unmanned aerial vehicle includes a propulsion system having at least one propulsion module comprised of at least one propeller and at least two motors/engines, one or more of the motors/engines providing mechanical energy to drive the propeller, wherein the difference between the angular velocities of the motors/engines provides energy input to a mechanical or magneto-mechanical linkage system to change the blade pitch angle of the propeller, in cyclic and/or collective manner.

An exemplary pitch lock for a tiltrotor aircraft to enable and disable a pitching degree of freedom of a rotor blade assembly includes a first tab coupled to a blade stop assembly, the first tab having a first ramp surface, a second tab coupled to a blade cuff, the second tab having a second ramp surface, a hasp having a central opening to receive the first and the second tab and rollers rotatably coupled to the hasp on opposite sides of the central opening, where the rollers engage the first and second ramp surfaces and retain the first and the second tabs in the central opening.

An exemplary spring-loaded link for an aircraft including a spring interposed between a first and a second rod, the spring, when compressed, urging the first rod and the second rod away from each other.

An exemplary pitch lock for a tiltrotor aircraft to enable and disable a pitching degree of freedom of a rotor blade assembly includes a first tab coupled to a blade stop assembly, the first tab having a first ramp surface, a second tab coupled to a blade cuff, the second tab having a second ramp surface, a hasp having a central opening to receive the first and the second tab and rollers rotatably coupled to the hasp on opposite sides of the central opening, where the rollers engage the first and second ramp surfaces and retain the first and the second tabs in the central opening.

An exemplary length adjustable link includes a tube having an internal bore and internal surface, a first rod end having a first shaft disposed in a first end of the internal bore, a second rod end having a second shaft disposed in a second end of the internal bore, and a member threadably connecting the first rod end to the second rod end.

A rotor craft changes a torsional angle of a blade by driving an actuator. The rotor craft includes a plurality of torsion applying mechanisms that each twist a proximal end portion of a corresponding blade relative to a distal end portion of the corresponding blade about a center axis A of the blade. Each blade includes a spar having a proximal end portion connected to a hub and a skin in which the spar is inserted, such that a distal end portion of the skin and a distal end portion of the spar are connected to each other, and such that other portions of the skin than the distal end portion are rotatable relative to the spar about a center axis of the spar. The hub includes a hub body mounted to a main rotor shaft, and a hub arm that connects the spar to the hub body.

A gas turbine engine includes a fan having a plurality of fan blades configured to rotate about a central axis of the gas turbine engine. Each fan blade is configured to pivot about a pivot axis that extends radially away from the central axis to vary a pitch of the fan blade. The fan further includes a counterforce system configured to resist forces that urge the fan blades away from their pitch positions during operation of the gas turbine engine.

A gas turbine engine includes a fan having a plurality of fan blades configured to rotate about a central axis of the gas turbine engine. Each fan blade is configured to pivot about a pivot axis that extends radially away from the central axis to vary a pitch of the fan blade. The fan further includes a counterforce system configured to resist forces that urge the fan blades away from their pitch positions during operation of the gas turbine engine.