Abstract: A tip gap control system for a ducted aircraft includes a flight control computer including an inner duct surface control module configured to generate an inner duct surface actuator command and a proprotor system in data communication with the flight control computer. The proprotor system includes a duct having active inner duct surfaces movable into various positions including a retracted position and an extended position. The proprotor system also includes proprotor blades surrounded by the duct and one or more actuators coupled to the active inner duct surfaces. The one or more actuators move the active inner duct surfaces between the various positions based on the inner duct surface actuator command, thereby controlling a tip gap between the proprotor blades and the duct.

Abstract: A rotor system for an aircraft includes an open rotor assembly comprising an open rotor assembly comprising a plurality of rotor blades connected to a rotor mast, wherein the rotor assembly is tiltable relative to a wing of the aircraft between a first position corresponding to an airplane mode of the aircraft and a second position corresponding to a helicopter mode of the aircraft; and a drive system for providing rotational energy to the open rotor assembly via the rotor mast. The drive system includes at least one electric motor for generating rotational energy to a motor shaft; and a gearbox connected to receive rotational energy from the at least one electric motor via the motor shaft and to provide rotational energy to the rotor mast via a rotor shaft, wherein the at least one electric motor is fixed relative to the wing of the aircraft.

Abstract: A rotor system for an aircraft is described and includes an open rotor assembly comprising a plurality of rotor blades connected to a rotor mast; and a drive system for providing rotational energy to the open rotor assembly via the rotor mast. The drive system includes at least one electric motor for providing rotational energy to a motor shaft; and a gearbox connected to the drive shaft for receiving rotational energy from the at least one electric motor via the motor shaft and providing rotational energy to the rotor mast via a rotor shaft.

Abstract: A rotor system for an aircraft includes an open rotor assembly comprising a plurality of rotor blades connected to a rotor mast via a yoke, wherein the rotor assembly is tiltable between a first position corresponding to an airplane mode and a second position corresponding to a helicopter mode; and a drive system for providing rotational energy to the open rotor assembly via the rotor mast, the drive system comprising at least one electric motor for providing rotational energy to a drive shaft and a gearbox connected to the drive shaft for receiving rotational energy from the at least one electric motor via the drive shaft and providing rotational energy to the rotor mast via a rotor shaft; wherein the drive system is rotatable relative to the wing about a tilt axis and the rotor shaft is coaxial with the drive shaft.

Abstract: A tip gap control system for a ducted aircraft includes a flight control computer including a blade length control module configured to generate a blade tip actuator command and a proprotor system in data communication with the flight control computer. The proprotor system includes a duct and proprotor blades surrounded by the duct. Each of the proprotor blades includes an active blade tip movable into various positions including a retracted position and an extended position. The tip gap control system also includes one or more actuators coupled to the active blade tips. The one or more actuators move the active blade tips between the various positions based on the blade tip actuator command, thereby controlling a tip gap between the proprotor blades and the duct.

Abstract: A proprotor blade for a ducted aircraft including a duct includes a main body having a distal end and a sacrificial blade tip coupled to the distal end of the main body. The sacrificial blade tip includes a deformable core material and a shell layer at least partially covering the deformable core material. The sacrificial blade tip deforms upon contact with the duct, thereby reducing damage to the ducted aircraft.

Abstract: An aircraft having multiple wing planforms. The aircraft includes an airframe having first and second half-wings with first and second pylons extending therebetween. A distributed thrust array is attached to the airframe. The thrust array includes a plurality of propulsion assemblies coupled to the first half-wing and a plurality of propulsion assemblies coupled to the second half-wing. A flight control system is coupled to the airframe. The fight control system is configured to independently control each of the propulsion assemblies and control conversions between the wing planforms. The aircraft is configured to convert between thrust-borne lift in a VTOL orientation and wing-borne lift in a forward flight orientation. In addition, the aircraft is configured to convert between a biplane configuration and a monoplane configuration in the forward flight orientation.

Abstract: A proprotor system for a ducted aircraft convertible between a vertical takeoff and landing flight mode and a forward flight mode includes a plurality of proprotor blades and a duct surrounding the proprotor blades. The duct includes an adaptive geometry device movable into various positions including a hover position and a cruise position. One or more actuators coupled to the adaptive geometry device are configured to move the adaptive geometry device between the hover position and the cruise position based on the flight mode of the ducted aircraft, thereby improving flight performance of the ducted aircraft.

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 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: A rotor system includes a rotor assembly and a duct system. The rotor assembly includes rotor blades extending from a mast axis and configured to rotate about the mast axis. The duct assembly includes a moveable duct portion and a stationary duct portion. In a first duct configuration, the moveable duct portion surrounds a first portion of the rotor assembly, the stationary duct portion surrounds a second portion of the rotor assembly, and the moveable duct portion and the stationary duct portion enclose the rotor assembly. In a second duct configuration, the stationary duct portion surrounds the second portion of the rotor assembly, and the moveable duct portion is moved away from the first portion of the rotor assembly, such that the rotor assembly is not enclosed.

Abstract: A proprotor system for a ducted aircraft includes a duct and proprotor blades surrounded by the duct. Each proprotor blade is rotatable about a respective pitch change axis. The proprotor blades are configured to change collective pitch about the pitch change axes. The proprotor blades are extendable along the pitch change axes into various positions including a retracted position and an extended position. The proprotor blades change between the retracted position and the extended position based on the collective pitch of the proprotor blades, thereby controlling a tip gap between the proprotor blades and the duct.

Abstract: A proprotor blade for a ducted aircraft including a duct includes a main body having a distal end and a sacrificial blade tip coupled to the distal end of the main body. The sacrificial blade tip includes a deformable core material and a shell layer at least partially covering the deformable core material. The sacrificial blade tip deforms upon contact with the duct, thereby reducing damage to the ducted aircraft.

Abstract: A tip gap control system for a ducted aircraft includes a flight control computer including an inner duct surface control module configured to generate an inner duct surface actuator command and a proprotor system in data communication with the flight control computer. The proprotor system includes a duct having active inner duct surfaces movable into various positions including a retracted position and an extended position. The proprotor system also includes proprotor blades surrounded by the duct and one or more actuators coupled to the active inner duct surfaces. The one or more actuators move the active inner duct surfaces between the various positions based on the inner duct surface actuator command, thereby controlling a tip gap between the proprotor blades and the duct.

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: A tip gap control system for a ducted aircraft includes a flight control computer including a blade length control module configured to generate a blade tip actuator command and a proprotor system in data communication with the flight control computer. The proprotor system includes a duct and proprotor blades surrounded by the duct. Each of the proprotor blades includes an active blade tip movable into various positions including a retracted position and an extended position. The tip gap control system also includes one or more actuators coupled to the active blade tips. The one or more actuators move the active blade tips between the various positions based on the blade tip actuator command, thereby controlling a tip gap between the proprotor blades and the duct.

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: A tip gap monitoring system for a ducted aircraft having a proprotor system including a duct and a plurality of proprotor blades includes sensors coupled to the proprotor system. The sensors are configured to detect one or more parameters of the proprotor system to form a plurality of sensor measurements. The tip gap monitoring system also includes a flight control computer in data communication with the sensors. The flight control computer includes a tip gap measurement module configured to determine a tip gap distance between the duct and the proprotor blades based on the sensor measurements.

Abstract: A proprotor system for a ducted aircraft includes a duct and proprotor blades surrounded by the duct. Each proprotor blade is rotatable about a respective pitch change axis. The proprotor blades are configured to change collective pitch about the pitch change axes. The proprotor blades are extendable along the pitch change axes into various positions including a retracted position and an extended position. The proprotor blades change between the retracted position and the extended position based on the collective pitch of the proprotor blades, thereby controlling a tip gap between the proprotor blades and the duct.

Abstract: One embodiment is a rotor system comprising a rotor duct; at least one rotor blade, wherein the at least one rotor blade comprises an outboard end; a tip extension mechanism affixed at the outboard end of the at least one rotor blade, wherein the tip extension mechanism comprises at least one shim, the at least one rotor blade with the tip extension mechanism affixed thereto comprising an extended rotor blade; and a blade tip affixed to an outboard end of the extended rotor blade, wherein the blade tip is affixed to the extended rotor blade via at least one removable fastener.