Abstract: A clutch has an inner race, an outer race spaced from the inner race and forming a radial cavity between the races, and a plurality of sprags disposed in the radial cavity. The sprags have a different coefficient of thermal expansion (CTE) from the inner race, the outer race, or both races, and a sprag cage retains the sprags at a uniform spacing within the radial cavity. When the clutch is at a first temperature, a gap exists between the sprags and the inner race, between the sprags and the outer race, or between the sprags and both races, and the clutch is disengaged. When the clutch is at a second temperature the sprags are in contact with both the races, and the clutch is engaged.

Abstract: An anti-torque system for a rotorcraft includes a first tail fan assembly including a plurality of first fan blades and a second tail fan assembly including a plurality of second fan blades. The first tail fan assembly has a larger diameter than the second tail fan assembly. The first fan blades have a larger rotational inertia than the second fan blades such that the second fan blades experience a larger angular acceleration than the first fan blades in response to torque, thereby providing yaw control for the rotorcraft.

Abstract: An aircraft that is convertible between a helicopter mode and an airplane mode. The aircraft includes a fuselage with a longitudinal axis and a vertical axis and distributed propulsion array that surrounds the vertical axis when the aircraft is operating the helicopter mode and surrounds the longitudinal axis when the aircraft is operating in the airplane mode.

Abstract: Systems and methods include providing an aircraft with a direct drive dual-concentric valve (D3V) having a body, an outer secondary spool coaxially located within a bore of the body and linearly displaceable relative to the body, an inner primary spool coaxially located within a bore of the secondary spool and linearly displaceable relative to the secondary spool and the body. A plurality of piezo stacks is coupled to a first end of the primary spool, and applying a voltage to at least one of the piezo stacks causes an output stroke of the plurality of the piezo strokes for displacing the primary spool. The secondary spool is displaced together with the primary spool relative to the body if displacement of the primary spool relative to the secondary spool cannot occur.

Abstract: A clutch has an inner race, an outer race spaced from the inner race and forming a radial cavity between the races, and a plurality of sprags disposed in the radial cavity. The sprags have a different coefficient of thermal expansion (CTE) from the inner race, the outer race, or both races, and a sprag cage retains the sprags at a uniform spacing within the radial cavity. When the clutch is at a first temperature, a gap exists between the sprags and the inner race, between the sprags and the outer race, or between the sprags and both races, and the clutch is disengaged. When the clutch is at a second temperature the sprags are in contact with both the races, and the clutch is engaged.

Abstract: An aircraft comprises a fuselage, one or more support structures connected to the fuselage, one or more engines or motors disposed within or attached to the one or more support structures or the fuselage, and a distributed propulsion system. The distributed propulsion system comprising two or more propellers symmetrically distributed in an array along the one or more support structures with respect to a center of gravity of the aircraft and operably connected to the one or more engines or motors, wherein each propeller has a rotation direction within a tilted plane of rotation, and a summation of horizontal force vectors created by the tilted plane of rotation of all the propellers is substantially zero when all the propellers are creating a substantially equal thrust magnitude. Movement of the aircraft is controlled by selectively increasing or decreasing a thrust of at least one of the two or more propellers.

Abstract: An aircraft capable of vertical takeoff and landing, stationary flight and forward flight, includes a closed wing that provides lift whenever the aircraft is in forward flight, a fuselage at least partially disposed within a perimeter of the closed wing, and one or more spokes coupling the closed wing to the fuselage. One or more motors are disposed within or attached to the spokes. Three or more propellers are proximate to a leading edge of the one or more spokes, distributed along the one or more spokes, and operably connected to the one or more motors to provide lift whenever the aircraft is in vertical takeoff and landing and stationary flight and provide thrust whenever the aircraft is in forward flight.

Abstract: A sprag clutch has an inner race, an outer race, and a radial cavity between the races. A plurality of sprags are disposed in the radial cavity, and each sprag is configured to rotate about an axis of rotation that is perpendicular to its longitudinal axis. A sprag cage retains each of the plurality of sprags at a uniform spacing within the radial cavity, and a plurality of actuators are positioned to exert or withdraw a force upon a corresponding sprag.

Abstract: An aircraft comprises a fuselage, one or more support structures connected to the fuselage, one or more engines or motors disposed within or attached to the one or more support structures or the fuselage, and a distributed propulsion system. The distributed propulsion system comprising two or more propellers symmetrically distributed in an array along the one or more support structures with respect to a center of gravity of the aircraft and operably connected to the one or more engines or motors, wherein each propeller has a rotation direction within a tilted plane of rotation, and a summation of horizontal force vectors created by the tilted plane of rotation of all the propellers is substantially zero when all the propellers are creating a substantially equal thrust magnitude. Movement of the aircraft is controlled by selectively increasing or decreasing a thrust of at least one of the two or more propellers.

Abstract: A system and method for providing a supplemental power includes: an engine, a transmission coupled to the engine, a motor-generator coupled to the transmission, and a battery system coupled to the motor-generator. The motor-generator is configured to draw an energy from the transmission and store the energy in the battery system when the engine is driving the transmission. The battery system is configured to discharge the energy to the motor-generator, and the motor-generator is configured to provide the supplemental power to the transmission.

Abstract: A powertrain for a rotorcraft includes first and second engines and a transmission system that includes a main rotor gearbox, a first freewheeling unit coupling the first engine to the main rotor gearbox and a second freewheeling unit coupling the second engine to the main rotor gearbox. The first freewheeling unit has a driving configuration and a bypass configuration. In a preflight configuration of the rotorcraft, the first engine provides power to at least one auxiliary component with the first freewheeling unit in the bypass configuration while the second engine provides power to the main rotor. In a flight configuration of the rotorcraft, the first engine provides power to the main rotor with the first freewheeling unit in the driving configuration while the second engine also provides power to the main rotor.

Abstract: A system for deploying and retrieving a parasite aircraft includes a parasite aircraft with a dock and a carrier aircraft that includes a maneuverable capture device tethered to the carrier aircraft via a cable. The maneuverable capture device includes a plurality of rotors and is configured to dock in the dock of the parasite aircraft. A method of deploying a parasite aircraft includes positioning a parasite aircraft on a loading surface; positioning a carrier aircraft above the parasite aircraft; releasing, from the carrier aircraft, a maneuverable capture device comprising a plurality of rotors; securing the maneuverable capture device to a dock positioned on the parasite aircraft; lifting, via a cable secured at a first end to the carrier aircraft and at a second end to the maneuverable capture device, the parasite aircraft with the carrier aircraft; and releasing the parasite aircraft from the maneuverable capture device.

Abstract: An aerial sky tram system includes a plurality of towers, a cable track suspended from the plurality of towers by a support cable, and a sky tram coupled to the cable track. The sky tram includes a plurality of rotors that propel the sky tram along the cable track.

Abstract: A parasite aircraft for airborne deployment and retrieve includes a wing; a fuselage rotatably mounted to the wing; a dock disposed on top of the fuselage and configured to receive a maneuverable capture device of a carrier aircraft; a pair of tail members extending from the fuselage; and a plurality of landing gear mounted to the wing. A method of preparing a parasite aircraft for flight includes unfolding an end portion of a wing; unfolding an end portion of a tail member of the parasite aircraft; and rotating a fuselage of the parasite aircraft so that the fuselage is perpendicular to the wing. A method of preparing a parasite aircraft for storage includes rotating a fuselage of the parasite aircraft to be parallel with a wing of the parasite aircraft; folding an end portion of the wing; and folding an end portion of a tail member of the parasite aircraft.

Abstract: A parasite aircraft for airborne deployment and retrieve includes a wing; a fuselage rotatably mounted to the wing; a dock disposed on top of the fuselage and configured to receive a maneuverable capture device of a carrier aircraft; a pair of tail members extending from the fuselage; and a plurality of landing gear mounted to the wing. A method of preparing a parasite aircraft for flight includes unfolding an end portion of a wing; unfolding an end portion of a tail member of the parasite aircraft; and rotating a fuselage of the parasite aircraft so that the fuselage is perpendicular to the wing. A method of preparing a parasite aircraft for storage includes rotating a fuselage of the parasite aircraft to be parallel with a wing of the parasite aircraft; folding an end portion of the wing; and folding an end portion of a tail member of the parasite aircraft.

Abstract: An aircraft includes a variable-speed gearbox. The variable-speed gearbox includes a low-speed gear train and a high-speed gear train, each gear train of which is configured to selectively provide torque from an engine of the aircraft to a proprotor. The variable-speed gearbox also includes a hydraulic system configured to provide torque to the proprotor. The hydraulic system includes a hydraulic pump driven by the engine of the tiltrotor aircraft and a variable-displacement motor driven by a hydraulic fluid from the hydraulic pump.

Abstract: A system and method for providing supplemental power includes: a motor-generator or a hydraulic pump-motor configured to attach to a transmission of an engine, a controller connected to the motor-generator or the hydraulic pump-motor, and a battery system or a hydraulic accumulator coupled to the motor-generator or the hydraulic pump-motor, respectively. During normal operation of the engine, the engine drives the transmission to rotate rotor blades connected to the transmission, and the motor-generator or the hydraulic pump-motor draws an energy from the transmission and store the energy in the battery system or the hydraulic accumulator, respectively. Upon a manual and/or an automatic control by the controller, the battery system or the hydraulic accumulator discharges the energy to the motor-generator or the hydraulic pump-motor, respectively, and the motor-generator or the hydraulic pump-motor provides the supplemental power to drive the transmission to rotate the rotor blades.

Abstract: In an embodiment, a maneuverable capture device includes a frame, a plurality of rotors secured to the frame, an attachment point disposed on the frame for securing a cable of a carrier aircraft to the frame, and an attachment feature configured to secure maneuverable capture device to a dock of a parasite aircraft. In an embodiment, a method of docking a maneuverable capture device with a parasite aircraft includes positioning a carrier aircraft above a parasite aircraft, releasing the maneuverable capture device attached to the carrier aircraft by a cable from the carrier aircraft, flying the maneuverable capture device to a dock of the parasite aircraft, and securing the maneuverable capture device to the dock of the parasite aircraft.

Abstract: A powertrain for a rotorcraft includes first and second engines and a transmission system that includes a main rotor gearbox, a first freewheeling unit coupling the first engine to the main rotor gearbox and a second freewheeling unit coupling the second engine to the main rotor gearbox. The first freewheeling unit has a driving configuration and a bypass configuration. In a preflight configuration of the rotorcraft, the first engine provides power to at least one auxiliary component with the first freewheeling unit in the bypass configuration while the second engine provides power to the main rotor. In a flight configuration of the rotorcraft, the first engine provides power to the main rotor with the first freewheeling unit in the driving configuration while the second engine also provides power to the main rotor.

Abstract: An aircraft capable of vertical takeoff and landing, stationary flight and forward flight includes a closed wing that provides lift whenever the aircraft is in forward flight, a fuselage at least partially disposed within a perimeter of the closed wing, and one or more spokes coupling the closed wing to the fuselage. One or more engines or motors are disposed within or attached to the closed wing, fuselage or spokes. Three or more propellers are proximate to a leading edge of the closed wing or the one or more spokes, distributed along the closed wing or the one or more spokes, and operably connected to the one or more engines or motors. The propellers provide lift whenever the aircraft is in vertical takeoff and landing and stationary flight, and provide thrust whenever the aircraft is in forward flight.