Abstract: A rotor assembly has a composite driveshaft extending between a transmission and a yoke for providing torque from the transmission to the yoke to cause rotation of the yoke and a plurality of rotor blade assemblies attached thereto. The rotor hub also has a composite static mast coupled to the yoke and a frame. The static mast being configured to carry the lift and thrust forces from the yoke to the frame.

Abstract: An advancing blade concept rotorcraft includes an airframe and a pylon assembly subject to vibration. The pylon assembly includes a dual rotor system having coaxially disposed top and bottom rotor assemblies that counter rotate relative to one another. The advancing blade concept rotorcraft includes a vibration isolation system including at least one pylon link coupled to the airframe and the pylon assembly. The pylon link includes a Liquid Inertia Vibration Eliminator unit operable to reduce transmission of the pylon assembly vibration to the airframe. The advancing blade concept rotorcraft includes active force generators adjacent to the pylon assembly. The active force generators include a first active force generator producing a force in a first direction and a second active force generator producing a force in a second direction to counteract multidirectional oscillations of the pylon assembly, thereby reducing vibration of the advancing blade concept rotorcraft.

Abstract: A vibration attenuator for a rotor of an aircraft has a housing adapted for rotation with the rotor about an axis. A first ring is rotatably carried within the housing on a first bearing, a first weight being coupled to the first ring for rotation therewith relative to the housing about the axis. A second ring is rotatably carried by the first ring on a second bearing, a second weight being coupled to the second ring for rotation therewith relative to the housing and to the first ring. A first motor is configured for rotating the first ring relative to the housing, and a second motor is configured for rotating the second ring relative to the housing and to the first ring. The first and second motors are operated to rotate the weights within the housing and position the weights relative to each other for attenuating vibrations.

Abstract: A quad tiltrotor aircraft has a longitudinally extending fuselage with forward and aft stations. A forward wing having first and second outboard ends extends laterally from the forward station. An aft wing having first and second outboard ends extends laterally from the aft station. First and second forward rotors are respectively coupled proximate the first and second outboard ends of the forward wing and are tiltable relative to the forward wing between vertical lift and forward thrust orientations. First and second aft rotors are respectively coupled proximate the first and second outboard ends of the aft wing and are tiltable relative to the aft wing between vertical lift and forward thrust orientations. The forward rotors are higher disk-loading rotors than the aft rotors. The aft rotors are foldable in the forward flight mode to provide extended range for the quad tiltrotor aircraft.

Abstract: A duct configured with a fan to increase thrust. The duct includes an interior surface configured to surround a rotation axis of the fan. The interior surface includes a nozzle portion configured to be located upstream of the fan and a diffuser portion configured to be located downstream of the fan. The interior surface defines an opening configured to introduce additional airflow along the diffuser portion.

Abstract: An aircraft, has an airframe, a transmission, and a liquid inertia vibration elimination (LIVE) system disposed between the airframe and the transmission via spherical bearings of two legs and via a central spherical bearing.

Abstract: A vibration attenuator for an aircraft has first and second coaxial spinners configured for rotation about a mast axis and relative to a rotor. Upper and lower weights of each spinner are spaced radially from the axis and positioned 180 degrees from each other about the axis. The weights of each spinner are spaced from each other a distance parallel to the mast axis, each weight rotating about the mast axis in a different plane. The spinners rotate together relative to the rotor at a selected angular rate and are selectively rotatable relative to each other between a minimum-moment configuration, in which the upper weight of each spinner is angularly aligned with the lower weight of the other spinner, and a maximum-moment configuration, in which the upper weights are angularly aligned and the lower weights are angularly aligned, producing a whirling moment about the mast axis as the spinners rotate.

Abstract: A rotor blade assembly includes a rotor blade comprising an inboard end and an outboard end. A composite yoke fitting made from a composite material is attached to the rotor blade. The composite yoke fitting includes an outboard portion inserted into the inboard end of the rotor blade, an inboard portion, and a flexure region about which the rotor blade is configured to flex. The inboard portion and the flexure region are outside the rotor blade.

Abstract: A vibration attenuator for a rotor of an aircraft has a track housing adapted for rotation relative to the rotor and configured for rotation at a second angular velocity greater than a first angular velocity of the rotor. A track is located within the track housing and has a reaction surface, a pair of weights being configured for movement within the track and in contact with the reaction surface. A stop assembly has a pair of stops spaced 180 degrees apart, the stops separating the weights from each other, and each weight being allowed to travel within the track between the stops. A motor rotates the track housing relative to the rotor. The weights are free to travel relative to each other between a minimum-force configuration, in which the weights are positioned 180 degrees apart, and a maximum-force configuration, in which both weights are adjacent one of the stops.

Abstract: An aircraft comprising a pair of ducted thrusters. Each of the ducted thrusters comprises a duct surrounding a rotor assembly with a rotor hub having a plurality of rotor blades extending therefrom, wherein the plurality of rotor blades have a modulated angular distribution about a central longitudinal axis of the duct. Each of the ducted thrusters further comprises a stator assembly having a stator hub with a plurality of stator vanes extending from the stator hub to an interior surface of the duct, wherein each of the plurality of the stator vanes are angularly modulated around the stator hub such that angular spacing between pairs of adjacent vanes of the plurality of stator vanes varies for each pair of the adjacent vanes.

Abstract: A rotor system includes a yoke, a plurality of blade grip assemblies and a plurality of centrifugal force bearings coupling the blade grip assemblies with the yoke. A plurality of rotor blades are coupled to the blade grip assemblies such that each rotor blade has a coincident hinge and such that each rotor blade has three independent degrees of freedom including blade pitch about a pitch change axis, blade flap about a flapping axis and lead-lag about a lead-lag axis. A blade-to-blade damping ring includes a plurality of damper anchors each coupled to one of the blade grip assemblies along the respective pitch change axis and a plurality of lead-lag dampers each coupled between adjacent damper anchors. During blade pitch operations, each blade grip assembly is operable to rotate relative to the respective damper anchor, such that the blade-to-blade damping ring is operable to provide pitch independent lead-lag damping.

Abstract: A hub system comprises at least one yoke, at least one shear bearing, and at least one mast adapter. The at least one mast adapter is configured to support the at least one yoke and the at least one shear bearing, and the at least one yoke has a flapping hinge that is non-coincident with a flapping hinge of the at least one shear bearing. Another hub system comprises a stacked yoke and a mast adapter. The mast adapter is configured to transfer rotation from a rotor mast to the hub system to rotate the hub system about a central axis of rotation. The mast adapter is further configured to support the stacked yoke such that each yoke in the stacked yoke is configured to accommodate at least some amount of rotation about an axis that is perpendicular to or about perpendicular to the central axis of rotation.

Abstract: A proprotor system for tiltrotor aircraft having a helicopter mode and an airplane mode. The proprotor system includes a hub and a plurality of proprotor blades coupled to the hub such that each proprotor blade is operable to independently flap relative to the hub and independently change pitch. In the airplane mode, the proprotor blades have a first in-plane frequency greater than 2.0/rev.

Abstract: Systems and methods include providing a coaxial helicopter with a main rotor system having an upper rotor system, a coaxial counter-rotating lower rotor system, and a rotor mast assembly having an upper rotor mast and a coaxial counter-rotating lower rotor mast. The upper rotor system and an associated upper vibration reduction system are coupled to the upper rotor mast. The upper vibration reduction system provides in-plane vibration control and reduction to the upper rotor system. The lower rotor system and an associated lower vibration reduction system are coupled to the lower rotor mast. The lower vibration reduction system provides in-plane vibration control and reduction to the lower rotor system. A third vibration reduction system is coupled to the rotor mast assembly and cooperates with the upper and lower vibration reduction systems to provide total in-plane vibration control and reduction to the main rotor system.

Abstract: A yoke for providing a centrifugal force retention load path between a proprotor blade and a hub of a soft-in-plane proprotor system operable for use on a tiltrotor aircraft. The yoke includes a continuous loop having a longitudinal axis and first and second longitudinal sections extending between inboard and outboard arcuate sections. A flapping bearing receiving region is disposed at least partially within the inboard arcuate section to an interior of the continuous loop. A centrifugal force bearing receiving region is disposed at least partially within the outboard arcuate section to the interior of the continuous loop. The continuous loop is formed from a composite material having a plurality of double bias material plies and a plurality of unidirectional material plies such that the number of unidirectional material plies is greater than the number of double bias material plies.

Abstract: A soft-in-plane proprotor system for a tiltrotor aircraft having a helicopter mode and an airplane mode. The proprotor system includes a hub, a plurality of proprotor blades and a plurality of loop yokes, each coupling one of the proprotor blades with the hub and each including first and second longitudinal sections extending between inboard and outboard arcuate sections and a bearing assembly disposed between the inboard and outboard arcuate sections of each loop yoke. Each bearing assembly includes a flapping bearing disposed generally within the inboard arcuate section of the respective loop yoke and coupled to the hub, a lead-lag damper coupled to the hub, a centrifugal force bearing disposed generally within the outboard arcuate section of the respective loop yoke and a blade anchor coupled between the lead-lag damper and the centrifugal force bearing. The blade anchor is also coupled to the respective proprotor blade.

Abstract: A rotorcraft has a low density altitude flight mode and a high density altitude flight mode. The rotorcraft includes a turboshaft engine forming a gas path in sequence through an air inlet section, a compressor section, a combustor section, a turbine section and an exhaust section. A drive system is coupled to the engine and is operable responsive to rotation of at least a portion of the turbine section. A rotor is coupled to the drive system and is operable to receive torque and rotational energy therefrom. A fuel injection system supplies fuel to the combustor section. An oxidizer injection system and a coolant injection system are used to selectively inject an oxidizer and a coolant into the gas path when it is desired to operate the rotorcraft in the high density altitude flight mode, thereby increasing the altitude density ceiling of the rotorcraft for maneuvers including takeoffs and landings.

Abstract: A proprotor system for a tiltrotor aircraft having helicopter and airplane flight modes includes a yoke having a plurality of blade arms each having an inboard pocket. Each of a plurality of bearing assemblies is disposed at least partially within one of the inboard pockets with each bearing assembly including a bearing cage, a shear bearing and a centrifugal force bearing. Each of a plurality of inboard beams is disposed at least partially between one of the centrifugal force bearings and one of the shear bearings. Each of a plurality of proprotor blades is coupled to one of the inboard beams. Hub bolts couple each of the bearing cages to the yoke such that the hub bolts provide centrifugal force load paths between the bearing assemblies and the yoke inboard of the inboard pockets.

Abstract: A propulsion assembly for a rotorcraft includes a blade assembly, a drive shaft coupled to the blade assembly and an electric motor coupled to the drive shaft and operable to provide rotational energy to the drive shaft to rotate the blade assembly. The propulsion assembly includes a landing assistance turbine coupled to the drive shaft and operable to selectively provide rotational energy to the drive shaft during an underpowered descent to rotate the blade assembly and provide upward thrust, thereby reducing a descent rate of the rotorcraft prior to landing.

Abstract: A proprotor system operable for use on a tiltrotor aircraft having a helicopter flight mode and an airplane flight mode. The proprotor system includes a rotor hub and a plurality of proprotor blades coupled to the rotor hub such that each proprotor blade has three independent degrees of freedom relative to the rotor hub including blade pitch about a pitch change axis, blade flap about a flapping axis and lead-lag about a lead-lag axis. Each of a plurality of spherical bearings couples one of the proprotor blades with the rotor hub. In addition, each of a plurality of lead-lag dampers couples one of the proprotor blades with the rotor hub, wherein each lead-lag damper is aligned with the pitch change axis of the respective proprotor blade, thereby providing pitch independent lead-lag damping.