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: A method of autonomous flight path planning for a group of cooperating aircraft operating in formation includes: receiving information related to obstructions that interfere with an aircraft of the group continuing on a flight path; calculating a velocity obstacle for each obstruction; calculating a plurality of candidate velocities outside of the velocity obstacles; selecting a first velocity from the candidate velocities and operating a leader of the group at the first velocity; calculating, based upon keeping a follower aircraft in formation, a second velocity for the follower; determining whether the second velocity is inside one of the velocity obstacles; operating the follower at the second velocity when the second velocity is outside the velocity obstacles; and calculating a revised velocity that is outside of the velocity obstacles and operating the follower at the revised velocity when the second velocity is inside one of the velocity obstacles.

Abstract: An example of a hub for a tail rotor includes a body configured to couple to a mast of a rotor system, a trunnion disposed within the body, first and second shafts disposed on opposite sides of the trunnion, first and second end plates secured to the body, and first and second end bearings, the first end bearing disposed between the first shaft and the first end plate and the second end bearing disposed between the second shaft and the second end plate.

Abstract: A bearing system includes an inboard bearing assembly and an outboard bearing assembly. The inboard bearing assembly includes an inboard fitting and an inboard race. The inboard fitting includes a plate with a convex mating surface and a first aperture formed through the plate for receiving a blade root of a rotor blade. The inboard race comprising a concave mating surface configured to receive the convex mating surface a second aperture formed the inboard race. The outboard bearing assembly includes an outboard bearing assembly comprising an outboard fitting having an aperture formed therethrough for receiving the blade root of the rotor blade.

Abstract: A rotorcraft comprising a rotor blade designed to flap about a hinge point, a measurement system designed to measure blade flapping, and a processing system designed to alter blade flapping measurements. The processing system further comprises a correction process to alter a blade flapping measurement dependent on rotor RPM or rotor torque.

Abstract: A compound helicopter includes a fuselage including a fuselage airframe, a translational thrust system coupled to the fuselage airframe and a pylon assembly subject to vibration. The pylon assembly includes a transmission and a rotor system having a main rotor assembly. The compound helicopter also includes a main rotor vibration isolation system including a plurality of augmented liquid inertia vibration eliminator units each having an isolation frequency and each coupled between the fuselage airframe and the pylon assembly to reduce transmission of the pylon assembly vibration to the fuselage airframe at the isolation frequency. Each augmented liquid inertia vibration eliminator unit includes at least one active tuning element movable to tune the isolation frequency thereof.

Abstract: In an embodiment, a method includes acquiring a current condition indicator of a condition indicator set associated with an operating condition of a machine, the condition indicator set indicating sensor readings associated with an operating element of the machine under the operating condition. The method also includes determining, by a data server, a relative trend significance over a trend window of the condition indicator set based, at least in part, on an evaluation of the trend window in relation to a historical window of the condition indicator set. The method also includes determining, by the data server, whether trend criteria associated with the operating element is satisfied, where the trend criteria may include criteria related to the relative trend significance. The method also includes executing, by the data server, an alerting process in response to the determining that the trend criteria is satisfied.

Abstract: A seal system for coaxially aligned shafts includes an input shaft and an output shaft coaxially aligned with the input shaft. The seal system includes a seal adapter support housing coupled to the output shaft and a seal positioned between an end of the input shaft and an end of the seal adapter support housing. The input shaft is configured to rotate at a speed that is different than a speed of the output shaft.

Abstract: An example of a collapsible pylon for a drone aircraft includes a bore extending through a length of a barrel, a first and a second flex-pin bore formed through a wall of the barrel, a first arm slidably positioned within a first end of the bore, a first flex pin disposed on the first arm to engage the first flex-pin bore, a second arm slidably positioned within a second end of the bore, and a second flex pin disposed on the second arm to engage the second flex-pin bore.

Abstract: One embodiment is a rotor system comprising a duct ring; a hub disposed centrally to the duct ring; first and second stators each connected between the duct ring and the hub; first and second control vanes rotatably connected to the first and second stators, respectively; a structural hoop having a first end connected to the first control vane and a second end connected to the second control vane, the structural hoop for translating rotation of the first control vane about a vane axis to the second control vane; and a mechanism for restricting at least one of forward-aft movement and side-to-side movement of the structural hoop relative to the duct ring.

Abstract: In an embodiment, a duct for a ducted-rotor aircraft includes a hub, the hub including a rotor and one or more motors configured to drive the rotor. The duct also includes a duct ring that defines an opening surrounding at least a portion of the hub. The duct also includes a plurality of stators that extend outward from the hub. The duct also includes at least one battery electrically coupled to the rotor and configured to power the one or more motors.

Abstract: An architecture for an electric distributed propulsion system includes one or more generators connected to a gearbox, a first and a second plurality of motors connected to the one or more generators, each motor of the plurality of motors connected to a blade to provide thrust, a first and a second power bus electrically connected between the one or more generators and the first and the second plurality of motors, each power bus independent of the other power bus, a first and a second controller independently connected to each of the first and second plurality of motors, each of the first and second controllers serving as a primary and a backup controller to provide redundant control to both the first and the second plurality of motors, and dual channels in communication between pilot input sensors and the first and the second controllers, each channel of the dual channels independent of the other channels, and the dual channels including an additional channel to provide redundant communication to the first an

Abstract: An exemplary distributed propulsion system with thermal management includes two or more rotors individually controlled by associated motors and an input control connected to the associated motors to demand the associated motors produce a demanded thrust, wherein a motor power output of each motor of the associated motors is independently controlled to produce the demanded thrust and to control a motor temperature of one or more of the associated motors.

Abstract: In an embodiment, a vertical-lift augmentation system for an aircraft includes a fan bank mounted to the aircraft in proximity to a wing of the aircraft, where the fan bank may include at least one fan. The vertical-lift augmentation system also includes a panel movably attached to the aircraft in relation to the fan bank, where the panel is adjustable between at least a first position in which the panel encloses the fan bank in the aircraft and a second position in which the panel at least partially exposes the fan bank.

Abstract: An exemplary continuous variable pitch rotor system includes a blade extending radially from a hub along a longitudinal axis, the blade rotationally coupled to the hub to permit limited rotation of the blade about the longitudinal axis in response to a change in a rotational speed of the hub. In some embodiments, the blade is held in a radially fixed position relative to the hub. In some embodiments, the blade is permitted to translate radially.

Abstract: A rotorcraft includes a plurality of fan assemblies. Each fan assembly of the plurality of fan assemblies includes a drivetrain having a gearbox with an input shaft and a mast coaxially aligned with the input shaft, and a plurality of electric motors coupled to the input shaft. Each electric motor of the plurality of electric motors is coupled to the input shaft via a sprag clutch.

Abstract: A gimbal joint may employ a plurality of wear sleeves, each disposed between a pin or pin receptive bore of a first structure and a corresponding bore or pin of a second structure and between another pin or bore of the second structure and a corresponding bore or pin of a third structure. Each of these structures may be adapted to rotate in a single plane, with one structure adapted to also tilt about a first axis, and one other structure adapted to tilt about a second axis. Each integral flanged wear sleeve may comprise a right circular hollow cylindrical body portion, which may be interiorly sized to be retained on one of the pins and externally sized to be retained in one of the pin receptive bores, and a flange portion may radiate from one end of the cylindrical body portion.

Abstract: An unmanned rotorcraft includes an airframe, rotor blades that are coupled to the airframe for rotation therewith, a propulsion unit having a propeller, and an actuator that is coupled to the airframe and adapted to temporarily reorient the propulsion unit such that an axis of the propeller moves out of alignment with an axis of the rotor blades. Rotation of the propeller causes counter-rotation of the airframe and rotor blades. The rotor blades and blades of the propeller are adapted to deploy from collapsed positions when flight of the rotorcraft is initiated. A method of operation by the rotorcraft includes, when it is determined that a current heading does not correspond to a determined flight path, causing the actuator to temporarily reorient the propulsion unit in accordance with an angular orientation of the actuator relative to the current heading.

Abstract: Various implementations described herein are directed to a lubrication system for a gearbox of an aircraft. A lubrication line is coupled to a plurality of jets and/or orifices to provide lubrication to one or more components of the gearbox. A check valve is placed within the lubrication line in a location upstream from the plurality of jets and/or orifices.

Abstract: A method for mobile robotic based inspection includes delivery of inspection requirements identifying a part and one or more inspection mode types. A three-dimensional model of the part and one or more physical attributes or specifications of the aeronautical part are received. A plurality of different motion sequences for the robot inspection system are determined to evaluate a plurality of predefined points on the component using one or more sensors for the one or more inspection types. Data acquisition parameters are determined for inspection sequence to allow for collection of inspection data for one or more inspection modes. A motion sequence from the plurality of different motion sequences is selected based on one or more parameters. An optimized inspection program configured to update operating parameters of the robot inspection system to perform the selected motion sequence and capture data using the one or more sensors is generated.