Abstract: A rotorcraft propulsion system includes a mast coupled to a rotor assembly, a gear coupled to the mast, the gear during use producing an axial reaction force, a flexure shaft extending from the gear, where the flexure shaft does not rotate with the gear and the flexure shaft flexes in response to radial loads from the gear, and a load cell on the flexure shaft to measure the axial reaction force.

Abstract: A drive system for an aircraft includes a first gearbox assembly and a second gearbox assembly that is in mechanical communication with the first gearbox assembly. A first pressurized lubrication system is configured to circulate a first lubricant through the first gearbox assembly. A second pressurized lubrication system is configured to circulate a second lubricant through the second gearbox assembly. An emergency lubrication system is configured to autonomously supply a portion of the first lubricant to the second gearbox assembly responsive to a loss of pressure in the second pressurized lubrication system. The emergency lubrication system is also configured to autonomously supply a portion of the second lubricant to the first gearbox assembly responsive to a loss of pressure in the first pressurized lubrication system.

Abstract: A drive system has a gearbox, comprising a passage therethrough, a coupling shaft disposed at least partially within the passage and a first coupling carried by a first end of the coupling shaft. The first coupling is configured to accommodate misalignment. The drive system also has a second coupling carried by a second end of the coupling shaft. The second coupling is also configured to accommodate misalignment.

Abstract: A tail rotor isolation system for rotorcraft includes a secondary engine, first and second freewheeling units, an isolation assembly and a tail rotor system. The secondary engine is coupled to the input race of the first freewheeling unit. A main rotor system is coupled to the output race of the second freewheeling unit. The isolation assembly is coupled to the output race of the first freewheeling unit and has a fully engaged position coupling the input and output races of the second freewheeling unit and a partially engaged position coupled to the input race but decoupled from the output race of the second freewheeling unit. The tail rotor system is coupled to the input race of the second freewheeling unit such that in the partially engaged position of the isolation assembly, the overrunning mode of the second freewheeling unit isolates the tail rotor system from the main rotor system.

Abstract: A bearing raceway for a shaft includes a tubular sleeve comprising a raceway section and a clamp section, the raceway section having a hardened outer surface and a first, axially linear, inner surface, and the clamp section having first threads and a second, axially non-linear, inner surface, where the first threads are configured to mate with second threads on a nut to clamp the tubular sleeve to the shaft.

Abstract: A drive system for an aircraft includes a first gearbox assembly and a second gearbox assembly that is in mechanical communication with the first gearbox assembly. A first pressurized lubrication system is configured to circulate a first lubricant through the first gearbox assembly. A second pressurized lubrication system is configured to circulate a second lubricant through the second gearbox assembly. An emergency lubrication system is configured to autonomously supply a portion of the first lubricant to the second gearbox assembly responsive to a loss of pressure in the second pressurized lubrication system. The emergency lubrication system is also configured to autonomously supply a portion of the second lubricant to the first gearbox assembly responsive to a loss of pressure in the first pressurized lubrication system.

Abstract: A bearing raceway for a shaft includes a tubular sleeve comprising a raceway section and a clamp section, the raceway section having a hardened outer surface and a first, axially linear, inner surface, and the clamp section having first threads and a second, axially non-linear, inner surface, where the first threads are configured to mate with second threads on a nut to clamp the tubular sleeve to the shaft.

Abstract: A system includes a chip detector that includes a magnet, the chip detector operable to collect a plurality of chips in a lubricant flow. The system also includes a radiation sensor associated with the magnet and operable to detect radiation emitted by at least some of the plurality of chips collected by the magnet.

Abstract: An exemplary passive oil system includes a reservoir housing configured in operation to rotate around a rotational axis, the reservoir housing defining a reservoir between a top wall, a bottom wall, innermost side, and an outer sidewall; and an outlet positioned adjacent the outer sidewall to discharge a lubrication fluid contained in the reservoir in response to the reservoir housing rotating around the rotational axis.

Abstract: A failsafe multimode clutch assembly positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling having a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly uses pressurized lubricating oil to shift the bypass assembly between the engaged position and a disengaged position. A lock assembly enables and disables actuation of the bypass assembly. In the disengaged position, the overrunning mode of the freewheeling unit enables a unidirectional torque transfer mode of the clutch assembly. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.

Abstract: A multimode clutch assembly is positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling unit having a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly shifts the bypass assembly between engaged and disengaged positions. An engagement status sensor is configured to determine the engagement status of the bypass assembly. In the disengaged position, the overrunning mode of the freewheeling unit is enabled such that the clutch assembly is configured for unidirectional torque transfer. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.

Abstract: A tail rotor isolation system for rotorcraft includes a secondary engine, first and second freewheeling units, an isolation assembly and a tail rotor system. The secondary engine is coupled to the input race of the first freewheeling unit. A main rotor system is coupled to the output race of the second freewheeling unit. The isolation assembly is coupled to the output race of the first freewheeling unit and has a fully engaged position coupling the input and output races of the second freewheeling unit and a partially engaged position coupled to the input race but decoupled from the output race of the second freewheeling unit. The tail rotor system is coupled to the input race of the second freewheeling unit such that in the partially engaged position of the isolation assembly, the overrunning mode of the second freewheeling unit isolates the tail rotor system from the main rotor system.

Abstract: Systems and methods include providing an aircraft with a fuselage and a wing assembly rotatable relative to the fuselage about a stow axis between a flight position and a stowed position. The aircraft includes an engine reduction gearbox having a retractable driveshaft that selectively engages the mid-wing gearbox via axially translatable motion along a rotation axis when the wing assembly is in the flight position. The mid-wing gearbox includes a plunger seal that is displaced in response to contact with the retractable driveshaft. Displacement of the plunger seal allows lubricant to flow through an inner bore in the retractable driveshaft, across splines of the retractable driveshaft and the mid-wing gearbox, and through lubrication ports in the mid-wing gearbox to lubricate the engine reduction gearbox, splines of the retractable driveshaft and the mid-wing gearbox, and the mid-wing gearbox via a single lubrication system.

Abstract: Briefly, implementations of claimed subject matter relate to methods and devices for coupling a first rotating shaft to a second shaft. In a particular implementation, an end of a plurality of resilient fingers of a resilient structure may be radially displaced to permit positioning of the resilient structure over a first shaft. An inwardly-directed portion of each of the plurality of the resilient fingers of the resilient structure may be secured to a channel located on an inner surface of a second shaft. After securing the resilient structure to the second shaft, the one or more resilient fingers of the resilient structure may be positioned within a slotted ladder ring encircling the first shaft.

Abstract: A multimode clutch assembly is positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling unit having a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly shifts the bypass assembly between engaged and disengaged positions. An engagement status sensor is configured to determine the engagement status of the bypass assembly. In the disengaged position, the overrunning mode of the freewheeling unit is enabled such that the clutch assembly is configured for unidirectional torque transfer. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.

Abstract: An exemplary tiltrotor aircraft with a hybrid drive system includes a first propulsion system having a first engine and a first supplemental driver operably coupled to a first proprotor that is operable between a helicopter mode and an airplane mode and a second propulsion system having a second engine and a second supplemental driver operably coupled to a second proprotor that is operable between a helicopter mode and an airplane mode.

Abstract: A tiltrotor aircraft includes a propulsion system with a fixed engine and a rotatable proprotor. The engine is located below the wing of the tiltrotor aircraft, and the rotatable proprotor assembly is mounted on the top surface of the wing. The engine and proprotor assembly are connected via a series of one or more gearboxes that route the engine output from the engine to the proprotor.

Abstract: A failsafe multimode clutch assembly positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling having a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly uses pressurized lubricating oil to shift the bypass assembly between the engaged position and a disengaged position. A lock assembly enables and disables actuation of the bypass assembly. In the disengaged position, the overrunning mode of the freewheeling unit enables a unidirectional torque transfer mode of the clutch assembly. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.

Abstract: A failsafe multimode clutch assembly is positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling unit having input and output races. The freewheeling unit has a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly must be energized to shift the bypass assembly from the engaged position to a disengaged position. In the disengaged position, the overrunning mode of the freewheeling unit is enabled such that the clutch assembly is configured for unidirectional torque transfer. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.

Abstract: A multimode clutch assembly is positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling unit having a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly shifts the bypass assembly between engaged and disengaged positions. An engagement status sensor is configured to determine the engagement status of the bypass assembly. In the disengaged position, the overrunning mode of the freewheeling unit is enabled such that the clutch assembly is configured for unidirectional torque transfer. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.