In one aspect the subject matter herein describes a cable tilt actuator for an aircraft propulsion unit. One embodiment comprises: a cable spool, fore and aft cable sections, a compression beam, a compression beam guide, and a linear actuator. As the linear actuator drives the compression beam, relative rotation is imposed between the compression beam and the spool. Described, in one aspect, is an embodiment configured to tilt an aircraft propulsion unit.

A rotor assembly for a rotary wing aircraft includes a rotor hub including a hub arm and a central opening. The rotor assembly further includes a hydraulic actuation cylinder positioned in the central opening, a pitch change shaft assembly including a pitch change shaft positioned partially within the hydraulic actuation cylinder, a pitch beam coupled to a distal end of the pitch change shaft and configured to be coupled to a rotor blade rotatably mounted to the hub arm. The rotor assembly additionally includes at least one guide rod coupled to the rotor hub and slidably coupled to an opening in the pitch change shaft.

In one aspect the subject matter herein describes a cable tilt actuator for an aircraft propulsion unit. One embodiment comprises: a cable spool, fore and aft cable sections, a compression beam, a compression beam guide, and a linear actuator. As the linear actuator drives the compression beam, relative rotation is imposed between the compression beam and the spool. Described, in one aspect, is an embodiment configured to tilt an aircraft propulsion unit.

A system to prevent or limit resonance in a rotocraft. The system comprises an airframe, a rotor system having a natural frequency and including a rotor and a mast attached to the airframe, and a non-linear spring positioned between the rotor system and the airframe. The rotor system and the airframe are operable to move relative to each other as the rotor system begins to oscillate. The non-linear spring is configured to be deformed when the rotor system and the airframe move relative to each other such that the deformation of the non-linear spring causes the natural frequency of the rotor system to change. Also disclosed is a related method for preventing or limiting resonance in a rotorcraft.