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: 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: 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 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: Embodiments are directed to a rotor blade comprising a blade tip attached to the outboard end of the rotor blade. The blade tip has at least two sides that are tapered together to an edge. The length of the blade tip extending away from the outboard end to the edge is a distance that is greater than half the thickness of the outboard end. When the rotor blade is operating in a folded configuration, air flows over the sides in a direction generally parallel to a longitudinal axis of the rotor blade. The sides have profiles that minimize or prevent separation of the air flow from the blade tip.

Abstract: Embodiments are directed to a blade lock comprising a fold lock adapted to prevent folding of a rotor blade in a fold-lock position and to allow folding of the rotor blade in a pitch-lock position. The blade lock further comprises a pitch lock adapted to allow pitch movement of a rotor blade in a fold-lock position and to prevent pitch movement of the rotor blade in the pitch-lock position. A spring-loaded link pivotally connects both the fold lock and the pitch lock and is adapted to provide passive, overcenter locking in the fold-lock position. An actuator is coupled to the pitch lock and is adapted to move the pitch lock and the fold lock between the fold-lock and pitch-lock positions.

Abstract: Embodiments are directed to a pitch horn assembly for an aircraft comprising a pitch horn rotatably coupled to a connector pin along a first axis using a first set of spherical bearings. The connector pin is rotatably coupled to a housing along a second axis using a second set of spherical bearings. A crank is fixedly coupled to the connector pin, wherein the pitch horn and the crank are configured to commonly rotate relative to the housing.

Abstract: An example of a method of manufacturing a component from a composite prepreg includes collecting a specimen from the composite prepreg and quantifying an amount of surface resin of the specimen by submerging the specimen in a container containing a fluid to determine a fluid pickup percentage. Responsive to a determination that the fluid pickup percentage exceeds a predefined threshold value, forming a component from the composite prepreg.

Abstract: A gearbox system for a rotorcraft includes a gearbox housing, an oil pump receiving bore formed into the gearbox housing and having formed therein a first opening having a first diameter and a second opening, and an oil pump positioned within the oil pump receiving bore. The second opening is bounded by a lip that extends radially into the second opening, the second opening having a second diameter that is smaller than the first diameter.

Abstract: An exemplary tiltrotor aircraft having a vertical takeoff and landing (VTOL) flight mode and a forward flight mode includes tiltable rotors located at forward boom ends, tiltable ducted fans located at wings aft of the forward boom ends, and aft rotors located on aft boom portions.

Abstract: A movable ballast system for an aircraft includes first and second ballast docks secured to the aircraft. The first ballast dock includes a first housing and a first ballast tray and a first stop plate secured within the first housing. The first ballast tray includes a plurality of channels. The second ballast dock is positioned aft of a CG of the aircraft and includes a second housing and a second ballast tray and a second stop plate secured within the second housing. The second ballast tray includes a plurality of channels. The movable ballast system includes a plurality of movable ballasts, each movable ballast of the plurality of movable ballasts being configured to fit within at least one channel of each of the plurality of channels of the first and second ballast trays.

Abstract: A rotatable nacelle includes an engine inlet configured to receive air and an inlet air management system (IAMS). The IAMS includes a primary inlet configured to selectively allow air to flow into a duct associated with the engine air inlet via the primary inlet and a secondary inlet configured to selectively allow air to flow into the duct associated with the engine air inlet via the secondary inlet. The secondary inlet is configured to receive an air filter.

Abstract: A method of repairing an aircraft component having a structural core surrounded by an exterior skin of composite material includes removing damaged material from the component to create a cavity therein that exposes an undamaged portion of the structural core, applying a septum comprising composite material to the undamaged portion of the structural core within the cavity such that an orientation of fibers in the septum matches an orientation of fibers in the exterior skin, placing a repair core onto the septum in the cavity such that cells of the repair core are in alignment with cells of the undamaged portion of the structural core, inserting a shim into the cavity along a perimeter of the repair core, applying a patch that covers the cavity to the exterior skin, and co-curing the septum, shim, and patch to bond the repair core in place within the cavity.

Abstract: A rotor blade retention device for use in an aircraft having a plurality of blades includes an array of cavities, each cavity adapted to receive a portion of a tension-torsion strap therein. Each cavity is oriented such that, when the portion of the tension-torsion strap is received therein, a central plane of the tension-torsion strap is inclined relative to a blade plane of rotation defined by the plurality of blades. The retention device may have a body that defines an aperture adapted to receive a portion of a rotor mast of the aircraft, may comprise a rotor mast of the aircraft, or may comprise first and second plates that cooperate to form the array of cavities and that are adapted to receive a portion of the rotor mast of the aircraft.