Abstract: A gear system includes a gear assembly having a shaft that is at least partially disposed within a housing of the gear system. A thrust bearing has inner and outer races with the outer race coupled to the housing. A bearing flexure is disposed between the inner race of the thrust bearing and the shaft. The bearing flexure includes a cylindrical cage having at least one shaft journal ring and a plurality of circumferentially distributed axially extending fingers coupled thereto with the shaft journal ring coupled to the shaft. A cylindrical bearing journal has inner and outer surfaces with the outer surface coupled to the inner race of the thrust bearing. Each of a plurality of circumferentially distributed radially extending struts extends between one of the fingers and the inner surface of the cylindrical bearing journal. The bearing flexure has an axial stiffness that is greater than its radial stiffness.

Abstract: A gear system includes a gear assembly having a shaft that is at least partially disposed within a housing of the gear system. A thrust bearing has inner and outer races with the outer race coupled to the housing. A bearing flexure is disposed between the inner race of the thrust bearing and the shaft. The bearing flexure includes a cylindrical cage having at least one shaft journal ring and a plurality of circumferentially distributed axially extending fingers coupled thereto with the shaft journal ring coupled to the shaft. A cylindrical bearing journal has inner and outer surfaces with the outer surface coupled to the inner race of the thrust bearing. Each of a plurality of circumferentially distributed radially extending struts extends between one of the fingers and the inner surface of the cylindrical bearing journal. The bearing flexure has an axial stiffness that is greater than its radial stiffness.

Abstract: A drivetrain for an aircraft includes an engine, a driveshaft receiving rotational energy from the engine and a gearbox including a planetary gear system receiving rotational energy from the driveshaft. The planetary gear system includes a sun gear, planet gears, a ring gear and an integral carrier forming flexured carrier posts. Each flexured carrier post supports a respective one of the planet gears and has a fixed proximal end and a cantilevered distal end. The planetary gear system includes flexured roller races, each having a fixed end and a cantilevered end. The fixed end of each flexured roller race is coupled to the cantilevered distal end of a respective flexured carrier post. The planet gears engage with the flexured roller races to rotate about the flexured carrier posts. The cantilevered ends of the flexured roller races experience cantilevered motion to absorb loads from the planet gears.

Abstract: A drivetrain for an aircraft includes an engine, a driveshaft receiving rotational energy from the engine and a gearbox including a planetary gear system receiving rotational energy from the driveshaft. The planetary gear system includes a sun gear, planet gears, a ring gear and an integral carrier forming flexured carrier posts. Each flexured carrier post supports a respective one of the planet gears and has a fixed proximal end and a cantilevered distal end. The planetary gear system includes flexured roller races, each having a fixed end and a cantilevered end. The fixed end of each flexured roller race is coupled to the cantilevered distal end of a respective flexured carrier post. The planet gears engage with the flexured roller races to rotate about the flexured carrier posts. The cantilevered ends of the flexured roller races experience cantilevered motion to absorb loads from the planet gears.

Abstract: A drivetrain for an aircraft includes an engine, a driveshaft to receive rotational energy from the engine and a gearbox including a multistage planetary gear system to receive rotational energy from the driveshaft. The multistage planetary gear system includes an integral multistage ring gear system having flanged and cantilevered ends. The integral multistage ring gear system forms a first stage ring gear at the cantilevered end and a second stage ring gear interposed between the flanged end and the first stage ring gear. The multistage planetary gear system includes a first stage sun gear, first stage planet gears and a first stage carrier. The first stage planet gears mate with the first stage ring gear. The multistage planetary gear system includes a second stage sun gear, second stage planet gears and a second stage carrier. The second stage planet gears mate with the second stage ring gear.

Abstract: A drivetrain for an aircraft includes an engine, a driveshaft receiving rotational energy from the engine and a gearbox including a planetary gear system receiving rotational energy from the driveshaft. The planetary gear system includes a sun gear, planet gears, a ring gear and an integral carrier forming flexured carrier posts. Each flexured carrier post supports a respective one of the planet gears and has a fixed proximal end and a cantilevered distal end. The planetary gear system includes flexured roller races, each having a fixed end and a cantilevered end. The fixed end of each flexured roller race is coupled to the cantilevered distal end of a respective flexured carrier post. The planet gears engage with the flexured roller races to rotate about the flexured carrier posts. The cantilevered ends of the flexured roller races experience cantilevered motion to absorb loads from the planet gears.

Abstract: A drivetrain for an aircraft includes an engine, a driveshaft receiving rotational energy from the engine and a gearbox including a planetary gear system receiving rotational energy from the driveshaft. The planetary gear system includes a sun gear, planet gears, a ring gear and an integral carrier forming flexured carrier posts. Each flexured carrier post supports a respective one of the planet gears and has a fixed proximal end and a cantilevered distal end. The planetary gear system includes flexured roller races, each having a fixed end and a cantilevered end. The fixed end of each flexured roller race is coupled to the cantilevered distal end of a respective flexured carrier post. The planet gears engage with the flexured roller races to rotate about the flexured carrier posts. The cantilevered ends of the flexured roller races experience cantilevered motion to absorb loads from the planet gears.

Abstract: A drivetrain for an aircraft includes an engine, a driveshaft to receive rotational energy from the engine and a gearbox including a multistage planetary gear system to receive rotational energy from the driveshaft. The multistage planetary gear system includes an integral multistage ring gear system having flanged and cantilevered ends. The integral multistage ring gear system forms a first stage ring gear at the cantilevered end and a second stage ring gear interposed between the flanged end and the first stage ring gear. The multistage planetary gear system includes a first stage sun gear, first stage planet gears and a first stage carrier. The first stage planet gears mate with the first stage ring gear. The multistage planetary gear system includes a second stage sun gear, second stage planet gears and a second stage carrier. The second stage planet gears mate with the second stage ring gear.

Abstract: A propulsion assembly for a rotorcraft includes a mast including a distal ridge and a proximal ridge forming a retaining pocket therebetween, a raceway receivable by the retaining pocket to form a press fit between the mast and the raceway and a mast bearing assembly including a plurality of bearings facing the mast to engage the raceway. The distal and proximal ridges are operable to reduce axial motion of the raceway along the mast, thereby securing the raceway in the retaining pocket.

Abstract: A dual rotor propulsion system for a tiltrotor aircraft having VTOL and forward flight modes. The dual rotor propulsion system includes an engine operable to provide an input torque to a transmission that, responsive thereto, generates an output torque. A first output shaft is coupled to the transmission and is operable to receive a first portion of the output torque. A first rotor assembly is coupled to and rotatable with the first output shaft. A second output shaft is coupled to the transmission and is operable to receive a second portion of the output torque. A second rotor assembly is coupled to and rotatable with the second output shaft. In operation, the first and second rotor assemblies rotate coaxially, the first rotor assembly is a different diameter than the second rotor assembly and the first rotor assembly is stoppable and foldable in the forward flight mode.

Abstract: A propulsion assembly for a rotorcraft includes a mast including a distal ridge and a proximal ridge forming a retaining pocket therebetween, a raceway receivable by the retaining pocket to form a press fit between the mast and the raceway and a mast bearing assembly including a plurality of bearings facing the mast to engage the raceway. The distal and proximal ridges are operable to reduce axial motion of the raceway along the mast, thereby securing the raceway in the retaining pocket.

Abstract: A dual rotor propulsion system for a tiltrotor aircraft having VTOL and forward flight modes. The dual rotor propulsion system includes an engine operable to provide an input torque to a transmission that, responsive thereto, generates an output torque. A first output shaft is coupled to the transmission and is operable to receive a first portion of the output torque. A first rotor assembly is coupled to and rotatable with the first output shaft. A second output shaft is coupled to the transmission and is operable to receive a second portion of the output torque. A second rotor assembly is coupled to and rotatable with the second output shaft. In operation, the first and second rotor assemblies rotate coaxially, the first rotor assembly is a different diameter than the second rotor assembly and the first rotor assembly is stoppable and foldable in the forward flight mode.