A rotor hub is presented that uses a low profile and frontal area design that reduces drag and combines the advantages of utilizing a virtual flapping hinge and a soft in-plane rotor hub.

A proprotor system for a tiltrotor aircraft having a helicopter flight mode and an airplane flight mode. The proprotor system includes a yoke having a plurality of blade arms with inboard pockets. A centrifugal force and shear bearing assembly is disposed in each of the inboard pockets of the yoke. Each of a plurality of proprotor blades is coupled to the yoke by one of the bearing assemblies such that each proprotor blade has a pitch change degree of freedom about a pitch change axis and a tilting degree of freedom about a focal point. Each bearing assembly includes a centrifugal force bearing coupled to the yoke, a shear bearing coupled to the yoke and an inboard beam coupled between the centrifugal force bearing and the shear bearing. Each inboard beam is coupled to a respective proprotor blade.

A proprotor system for a tiltrotor aircraft having a helicopter flight mode and an airplane flight mode. The proprotor system includes a yoke having a plurality of blade arms with inboard pockets. A centrifugal force and shear bearing assembly is disposed in each of the inboard pockets of the yoke. Each of a plurality of proprotor blades is coupled to the yoke by one of the bearing assemblies such that each proprotor blade has a pitch change degree of freedom about a pitch change axis and a tilting degree of freedom about a focal point. Each bearing assembly includes a centrifugal force bearing coupled to the yoke, a shear bearing coupled to the yoke and an inboard beam coupled between the centrifugal force bearing and the shear bearing. Each inboard beam is coupled to a respective proprotor blade.

An aircraft rotor assembly has a central yoke and a plurality of rotor blades coupled to the yoke for rotation with the yoke about an axis, each blade having a Lock number of approximately 5 or greater. A lead-lag pivot for each blade is a radial distance from the axis and allows for in-plane lead-lag motion of the associated blade relative to the yoke, each pivot allowing for in-plane motion from a neutral position of at least 1 degree in each of the lead and lag directions. Lead and lag motion of each blade is opposed by a biasing force that biases the associated blade toward the neutral position, and the biasing force is selected to achieve a first in-plane frequency of greater than 1/rev for each blade.

An aircraft rotor assembly has a central yoke and a plurality of rotor blades coupled to the yoke for rotation with the yoke about an axis, each blade having a Lock number of approximately 5 or greater. A lead-lag pivot for each blade is a radial distance from the axis and allows for in-plane lead-lag motion of the associated blade relative to the yoke, each pivot allowing for in-plane motion from a neutral position of at least 1 degree in each of the lead and lag directions. Lead and lag motion of each blade is opposed by a biasing force that biases the associated blade toward the neutral position, and the biasing force is selected to achieve a first in-plane frequency of greater than 1/rev for each blade.

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.

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.

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.

A laminated elastomeric bearing has layers of elastomeric material and layers of metal. A tab is located on a periphery of one of the layers of metal and protrudes from the bearing. A thermoelectric device is coupled to the tab, and heat generated within the bearing during use is conducted to the tab and to the thermoelectric device, allowing for measurement of the heat.

A laminated elastomeric bearing has layers of elastomeric material and layers of metal. A tab is located on a periphery of one of the layers of metal and protrudes from the bearing. A thermoelectric device is coupled to the tab, and heat generated within the bearing during use is conducted to the tab and to the thermoelectric device, allowing for measurement of the heat.