An aircraft is provide including an airframe, an extending tail, and a counter rotating, coaxial main rotor assembly including an upper rotor assembly and a lower rotor assembly. A translational thrust system positioned at the extending tail, the translational thrust system providing translational thrust to the airframe. At least one flight control computer configured to independently control the upper rotor assembly and the lower rotor assembly through a fly-by-wire control system. A plurality of sensors to detect sensor data of at least one environmental condition and at least one aircraft state data, wherein the sensors provide the sensor data to the flight control computer.

An aircraft is provide including an airframe, an extending tail, and a counter rotating, coaxial main rotor assembly including an upper rotor assembly and a lower rotor assembly. A translational thrust system positioned at the extending tail, the translational thrust system providing translational thrust to the airframe. At least one flight control computer configured to independently control the upper rotor assembly and the lower rotor assembly through a fly-by-wire control system. A plurality of sensors to detect sensor data of at least one environmental condition and at least one aircraft state data, wherein the sensors provide the sensor data to the flight control computer.

Propeller assemblies, aircraft including the same, and associated methods. A propeller assembly includes a first propeller and a second propeller operatively coupled to a coupling shaft and configured to pivot with respect to one another about a propeller rotation axis. The propeller assembly additionally includes a coupling assembly operatively coupled to the first propeller and the second propeller and configured to transition between a plurality of pivotal configurations defined between and including a stowed configuration and a deployed configuration. The coupling assembly transitions from the stowed configuration toward the deployed configuration when a coupling assembly rotational velocity rises above a threshold stowed rotational velocity. In examples, an aircraft includes one or more propeller assemblies operatively coupled to a fuselage. In some examples, a method of operating a propeller assembly includes automatically transitioning a coupling assembly of the propeller assembly between a stowed configuration and a deployed configuration.

Propeller assemblies, aircraft including the same, and associated methods. A propeller assembly includes a first propeller and a second propeller operatively coupled to a coupling shaft and configured to pivot with respect to one another about a propeller rotation axis. The propeller assembly additionally includes a coupling assembly operatively coupled to the first propeller and the second propeller and configured to transition between a plurality of pivotal configurations defined between and including a stowed configuration and a deployed configuration. The coupling assembly transitions from the stowed configuration toward the deployed configuration when a coupling assembly rotational velocity rises above a threshold stowed rotational velocity. In examples, an aircraft includes one or more propeller assemblies operatively coupled to a fuselage. In some examples, a method of operating a propeller assembly includes automatically transitioning a coupling assembly of the propeller assembly between a stowed configuration and a deployed configuration.

One embodiment is a rotor system including a rotor hub comprising a plurality of extension arms for connecting rotor blades to the rotor hub; a plurality of dampers connected between a respective one of the extension arms and the rotor hub; and a fairing disposed over the rotor hub, the fairing including an inlet plenum through which air is drawn from outside the fairing into the fairing; and at least one duct for conducting the air toward the at least one of the dampers.

Technologies are generally described for lead-lag dampers. An example lead-lag may include a single- or two-stage floating annular ring, elastomer bearings, a tension stop, a compression stop, and a plunger/spring volume compensator. The floating annular ring(s) form orifice(s) in conjunction with the remaining damper components may provide stable performance by tracking with any center shaft misalignment during operation. The lead-lag damper may also include a secondary spring system allowing or disallowing fluid flow between chambers based on slow or sudden movement of the shaft.

Technologies are generally described for lead-lag dampers. An example lead-lag may include a single- or two-stage floating annular ring, elastomer bearings, a tension stop, a compression stop, and a plunger/spring volume compensator. The floating annular ring(s) form orifice(s) in conjunction with the remaining damper components may provide stable performance by tracking with any center shaft misalignment during operation. The lead-lag damper may also include a secondary spring system allowing or disallowing fluid flow between chambers based on slow or sudden movement of the shaft.

A device for self-balancing a rotating part, such as a propeller, along a given axis is disclosed. The propeller 102 coupled to, a drive shaft with freedom for linear movement along longitudinal axis L-L; at least one pair of levers 614/616, comprising a first lever 614-1/616-1 and a second lever 614-2/616-2, that are pivotally mounted on mounting plate 606 at two diametrically opposite points 618; and at least one pair of weights 622 fixed at external ends of the levers 614/616. inner ends of levers 614/616 are operatively coupled to the propeller 102 such that when propeller 102 undergoes a linear movement in any direction along the longitudinal, axis L-L due to unbalance, inner ends of levers are, moved to cause the weights 622 to move to provide a balancing force to neutralize the unbalance in the propeller. An embodiment with only one pair of levers is also disclosed.

A device for self-balancing a rotating part, such as a propeller, along a given axis is disclosed. The propeller 102 coupled to, a drive shaft with freedom for linear movement along longitudinal axis L-L; at least one pair of levers 614/616, comprising a first lever 614-1/616-1 and a second lever 614-2/616-2, that are pivotally mounted on mounting plate 606 at two diametrically opposite points 618; and at least one pair of weights 622 fixed at external ends of the levers 614/616. inner ends of levers 614/616 are operatively coupled to the propeller 102 such that when propeller 102 undergoes a linear movement in any direction along the longitudinal, axis L-L due to unbalance, inner ends of levers are, moved to cause the weights 622 to move to provide a balancing force to neutralize the unbalance in the propeller. An embodiment with only one pair of levers is also disclosed.

A piston assembly for a lead-lag damper for a blade mounted on a rotor of a helicopter includes a piston-rod that has an inside surface and a piston-head that extends radially outward therefrom. The piston-rod has two ports extending therethrough on opposing sides of the piston-head. A sleeve is positioned in the piston-rod and has two annular passages that communicate with the respective ports. A valve spool is disposed in and slidingly engages the sleeve. The valve spool has a channel which is in variable fluid communication with two passages. The piston assembly includes a biasing member that biases the valve spool axially away from it. The channel has an axial width configured to variably regulate fluid flow between the two ports to control dampening of the piston-rod in response to centrifugal forces applied to the valve spool.