Abstract: A tiltrotor aircraft is designed to accommodate rotors of different diameters, as well as corresponding wings and fuselages with different span and length, while maintaining very high parts commonality, especially with respect to drive train and power source. This enables design and operation of a fleet of such aircraft with significantly different rotor diameters, which are nevertheless optimized for different missions. In preferred embodiments the rotors are configured to have high stiffness and low weight to reduce aero-structural dynamic issues across the fleet. Also in preferred embodiments drive systems are designed for a full range of speed, torque, and power associated with all intended rotors. Turboshaft engine speeds are restricted to a narrow RPM range, so that a single gearset can be replaced to achieve the desired rotor RPM. Also in preferred embodiments, aircraft in a fleet can differ in folded length, empty weight, payload length by up 50%.

Abstract: An up-down flapping wingtip is provided for a ground effect vehicle. The wingtip is positionable at an anhedral angle to control the wingtip clearance from ground. Variable wingtip clearance reduces the risk of damage due to collision with the ground or water, thereby permitting more efficient flight at lower altitude with an equivalent safety. The wingtip is positioned by a wingtip flap and an actuator. The wingtip anhedral angle is controlled by a flight control system. A sensor is included for determining whether an object lies in the path of the wingtip. The sensor communicates with the flight control system in order to vary the flapping angle of the wingtip to increase clearance from the ground or water, thus avoiding impact with the object. The wingtip anhedral angle is reduced to increase the wingspan for flight out of ground effect.

Abstract: A tiltrotor aircraft is designed to accommodate rotors of different diameters, as well as corresponding wings and fuselages with different span and length, while maintaining very high parts commonality, especially with respect to drive train and power source. This enables design and operation of a fleet of such aircraft with significantly different rotor diameters, which are nevertheless optimized for different missions. In preferred embodiments the rotors are configured to have high stiffness and low weight to reduce aero-structural dynamic issues across the fleet. Also in preferred embodiments drive systems are designed for a full range of speed, torque, and power associated with all intended rotors. Turboshaft engine speeds are restricted to a narrow RPM range, so that a single gearset can be replaced to achieve the desired rotor RPM. Also in preferred embodiments, aircraft in a fleet can differ in folded length, empty weight, payload length by up 50%.

Abstract: Systems and methods are contemplated for favorably improving flight dynamics of aircraft, including enhanced aerodynamic braking and improved flight maneuverability. Air braking systems selectively position a first set of blades at a negative thrust pitch to product a net negative thrust across first and second sets of blades, while balancing torque of the drive shafts to zero. First and second sets of IBC blades can be driven by the same shaft or torque-linked shafts. Flight maneuver systems operate a powerplant at a high power mode, and dissipate the energy from the high power output by positioning a first set of IBC blades at a low efficiency pitch while maintaining constant thrust. As increased or rapid flight maneuverability is required, the first set of blades is positioned toward a high efficiency pitch to instantly increase thrust to the aircraft without requiring a related increase in energy output from the powerplant.

Abstract: Apparatus, systems, and methods are contemplated for electric powered vertical takeoff and landing (eVTOL) aircraft. Such are craft are engineered to carry safely carry at least 500 pounds (approx. 227 kg) using a few (e.g., 2-4) rotors, generally variable speed rigid (non-articulated) rotors. It is contemplated that one or more rotors generate a significant amount of lift (e.g., 70%) during rotorborne flight (e.g., vertical takeoff, hover, etc), and tilt to provide forward propulsion during wingborne flight. The rotors preferably employ individual blade control, and are battery powered. The vehicle preferably flies in an autopilot or pilotless mode and has a relatively small (e.g., less than 45? diameter) footprint.

Abstract: Methods of manufacturing and operating a solar powered aircraft having segmented wings that can be reconfigured during flight to optimize collection of solar energy are described. The aircraft have rigid construction that is resistant to inclement weather and is configured to rely on free flight control at high altitude and under conventional conditions, thereby providing flight duration in excess of 2 months. The aircraft is particularly suitable for use as part of a telecommunications network.

Abstract: An aerial surveillance and reconnaissance system includes a gimbal-stabilized ISR imaging sensor with 0.8-1.2 microradian optical resolution, using pulsed ultraviolet laser (0.330-0.380 micrometer wavelength) radiation to illuminate the observed target, and a narrow-band-pass filter at the focal plane detector to remove light at frequencies other than the illuminating frequency. Preferred sensors can be operated in a snapshot mode using intermittent illuminating pulses, with timing of the pulses selected for minimum detectability based on observations made with a lower-resolution sensor, or in a video-mode with illuminating pulses selected to generate full-motion video at operator-selectable frame rates. Some sensor embodiments may further combine the UV system described above with conventional daylight optical and sensor systems, though alternative arrangements could also include an IR sensor as well (either using a common aperture with the UV system or with a separate set of light-gathering optics).

Abstract: A solar powered aircraft having segmented wings that can be reconfigured during flight to optimize collection of solar energy are described. The aircraft have rigid construction that is resistant to inclement weather and is configured to rely on free flight control at high altitude and under conventional conditions, thereby providing flight duration in excess of 2 months. The aircraft is particularly suitable for use as part of a telecommunications network. A telecommunications network incorporating such aircraft is also discussed.

Abstract: An aerial surveillance and reconnaissance system includes a gimbal-stabilized ISR imaging sensor with 0.8-1.2 microradian optical resolution, using pulsed ultraviolet laser (0.330-0.380 micrometer wavelength) radiation to illuminate the observed target, and a narrow-band-pass filter at the focal plane detector to remove light at frequencies other than the illuminating frequency. Preferred sensors can be operated in a snapshot mode using intermittent illuminating pulses, with timing of the pulses selected for minimum detectability based on observations made with a lower-resolution sensor, or in a video-mode with illuminating pulses selected to generate full-motion video at operator-selectable frame rates. Some sensor embodiments may further combine the UV system described above with conventional daylight optical and sensor systems, though alternative arrangements could also include an IR sensor as well (either using a common aperture with the UV system or with a separate set of light-gathering optics).

Abstract: A harmonic drive has an outer gear, an elliptical follower hub, and an outer chain coupled to the follower hub, and having teeth that mate with the outer gear. Preferred embodiments further include an inner chain disposed such that the follower hub is functionally interposed between the inner and outer chains.

Abstract: An electric linear actuator is disposed to pitch a blade of a hingeless, swashplateless rotor in rotary motion. This actuator can be equipped with an electric motor advantageously made fault tolerant by winding the motor for at least 4, 5, 6, 8, or even 12 phases. Rotational motion of the electric motor is preferably converted to a translatory linear actuator output motion using a planetary roller screw coupling the rotation of the motor with pitch of the blade. The output link of the actuator can be advantageously coupled to the planetary roller screw using an internal spherical joint providing an isolated load path through the actuator. It is contemplated that a preferred rotorcraft having an electric blade pitch actuator might also be equipped with a controller that could provide the vehicle with individual blade control, in which the pitch of any rotor blade can be controlled independently of the others.

Abstract: A gearbox comprising a gearset is able to transmit high output torques at high numerical reduction ratios at a power-to-weight ratio higher than previously attainable with existing designs. A distributor gear is disposed relative to a spur gear in order to produce automatic torque balancing. The distributor gear can be advantageously configured as an input floatring gear, for which support in all directions is provided by gear tooth mesh forces rather than bearings. Automatic torque balancing is achieved by configuring the distributor gear with first and second rows of helical teeth on the external circumference, and with a set of double helical teeth disposed on the internal circumference of the distributor gear. This allows for the placement of up to 50 or more planet gears in a countershaft arrangement with one end having helical teeth and the other end having spur teeth.

Abstract: A tiltrotor aircraft having a fixed wing and tilting rotors has a rotor blade with a shaped tip portion that provides improved hover performance. The shaped tip portion preferably has a terminal anhedral of at least 20° with respect to its stacking line, and the blade has an overall twist from root to tip of at least 20°, and a thickness ratio between 19% and 30% at a radial station of 10%. These features advantageously conspire to provide a hover figure of merit of at least 0.84 and a cruise propulsive efficiency of at least 0.85. A controller preferably limits the rotor speed in sustained airplane-mode forward flight cruise of at most 40% of a hover maximum rotor speed, and alternatively or additionally limits a rotor edgewise advance ratio to at most 0.20.

Abstract: Systems and methods are provided in which an electrical control system independently effects acceleration of both driven and driving elements of a clutch to engage each other. In preferred embodiments the clutch is not a friction clutch, but a dog clutch, and forms part of a drive drain of a rotorcraft. A second clutch can be used, along with a mechanical interlock to prevent simultaneous engagement of the clutches. Speeds of the driven and driving elements can be sensed, and altered using at least one of a rotor, a brake, a generator, an electric motor, and a combustion motor. In rotorcraft embodiments, the gearbox can have a neutral condition in which no power is transmitted from the engine to the rotor.

Abstract: A spar of a rotor blade having moderate depth transitions to a relatively much deeper shank over a relatively short distance. This rapid transition enables a low-weight blade root that is structurally efficient, offers a high moment capability, and enables high Mach number axial flow. A transition could advantageously reduce section depth by at least 15%, 20%, 30%, or even 40% over at most 5%, 6%, 10%, or 12% of a total length of the rotor blade. Such a transition could advantageously be accomplished using a cuff, which has interfaces with each of the spar and the shank. The rotor blade shank has a generally circular cross-section which allows for a rotary attachment to a hub, where the attachment may advantageously comprise a mechanical or elastomeric bearing. Preferred embodiments have a spar with a generally rectangular cross-section.

Abstract: Electrically controlled and/or actuated landing gear mechanisms are presented that allow for adjustment of aircraft attitude on the ground as well as for retraction and extension of the landing gear in a single unit. Most preferably, the electric actuator is positioned within the diameter of the strut to thereby form a compact and load bearing structure.

Abstract: A tiltrotor aircraft having a fixed wing and tilting rotors has a rotor blade with a shaped tip portion that provides improved hover performance. The shaped tip portion preferably has a terminal anhedral of at least 20° with respect to its stacking line, and the blade has an overall twist from root to tip of at least 20°, and a thickness ratio between 19% and 30% at a radial station of 10%. These features advantageously conspire to provide a hover figure of merit of at least 0.84 and a cruise propulsive efficiency of at least 0.85. A controller preferably limits the rotor speed in sustained airplane-mode forward flight cruise of at most 40% of a hover maximum rotor speed, and alternatively or additionally limits a rotor edgewise advance ratio to at most 0.20.

Abstract: An aircraft is equipped with hingeless rotors on tilting nacelles, and the tilt angles of the nacelles are controlled using either or both of an actuator and a mast moment generated by a hingeless rotor. An aircraft with two or more rotors on tilting nacelles can achieve control of yaw orientation by differential tilt of its nacelles or masts. Hingeless rotors can be manipulated to control a tilt angle of a mast by changing the rotor blade pitch to produce a mast moment. The rotor and nacelle tilt of a tiltrotor rotorcraft can be controlled and effected in order to manipulate the yaw orientation and flight mode of a rotorcraft such as a tiltrotor. The use of mast moment to control nacelle tilt angle can reduce tilt actuator loads and allows for the control of nacelle tilt even in the event of an actuator failure.

Abstract: Systems and methods are provided in which an electrical control system independently effects acceleration of both driven and driving elements of a clutch to engage each other. In preferred embodiments the clutch is not a friction clutch, but a dog clutch, and forms part of a drive drain of a rotorcraft. A second clutch can be used, along with a mechanical interlock to prevent simultaneous engagement of the clutches. Speeds of the driven and driving elements can be sensed, and altered using at least one of a rotor, a brake, a generator, an electric motor, and a combustion motor.

Abstract: Systems and methods are provided in which an electrical control system independently effects acceleration of both driven and driving elements of a clutch to engage each other. In preferred embodiments the clutch is not a friction clutch, but a dog clutch, and forms part of a drive drain of a rotorcraft. A second clutch can be used, along with a mechanical interlock to prevent simultaneous engagement of the clutches. Speeds of the driven and driving elements can be sensed, and altered using at least one of a rotor, a brake, a generator, an electric motor, and a combustion motor.