A fuel efficient aircraft propulsion system comprises a wingtip mounted ducted pusher fan with convergent backwash and a skewed conical engine nacelle. The system both mitigates wingtip vortex drag and converts a portion of vortex energy into propulsion force and lift force. The forward-tapering nacelle skews both downward and inward, so the lower nacelle surface is flush with the lower wing surface and the inboard nacelle surface does not alter flow over the upper wing surface. This firstly preserves lift at the outboard wing end. Secondly, air displacement by the nacelle accelerates flow only on the outboard and upper nacelle surfaces, and because the nacelle occupies the core of the nascent wingtip vortex, rotational air velocity is greatest on the upper nacelle surface. The resultant pressure drop on the upper nacelle surface contributes to aircraft lift. And because the nacelle surface tapers forward, this pressure drop does not exert backward-acting drag on the aircraft. Aft of the nacelle, the pusher fan hub surface conforms with the aft nacelle surface and tapers aft. Propulsion foils project from the forward portion of the pusher fan hub at an outward-aft angle, which directs convergent high pressure backwash flow along the aft tapering hub surface. This isolates aft-facing hub surfaces from drag-inducing vortex core pressure drop. Downstream fan backwash convergence then forms a central volume of high pressure flow where the low pressure trailing vortex core would otherwise develop. This is an efficient means to dissipate the cyclonic structure of the vortex, because vortex persistence requires low pressure core persistence. The direction of pusher fan rotation opposes the direction of wingtip vortex rotation as described in the prior art. This cross-flow interaction increases the effective power of the fan and also further counters vortex formation. An integral peripheral duct links the outer ends of the fan propulsion foils to provide thrust efficiency similar to that of a high bypass fanjet engine, but without the internal air friction within a bypass channel. In an alternative horizontal axis wind turbine embodiment, the same nacelle form supports secondary power-takeoff turbines mounted in high energy density flow at the turbine blade tips.

A wing for an aircraft, including a main wing and a wing tip device, a front blade and a rear blade of the wing tip device extending from an attachment end, a front blade leading edge extending in front of a rear blade leading edge and a front blade trailing edge extending in front of a rear blade trailing edge, in a chord direction, and at a front blade tip the front blade extending under a different dihedral angle than the rear blade at a rear blade tip. The front blade leading and trailing edges, as well as the rear blade leading and trailing edges have a tangent-continuous developing. The front blade leading edge extends tangent-continuously with the wing leading edge. The rear blade trailing edge extends tangent-continuously with the wing trailing edge. The front blade trailing edge extends behind the rear blade leading edge, in the chord direction.

Embodiments of methods and apparatus for close formation flight are provided herein. In some embodiments, a method of operating aircraft for flight in close formation includes establishing a communication link between a first aircraft and a second aircraft, assigning to at least one of the first aircraft or the second aircraft, via the communication link, initial positions relative to one another in the close formation, providing flight control input for aligning the first and second aircraft in their respective initial positions, tracking, by at least one aircraft in the close formation, at least one vortex-generated by at least one other aircraft in the close formation, and based on the tracking, providing flight control input to adjust a relative position between the first aircraft and the second aircraft.

An active winglet includes a body portion substantially parallel to a wing of an aircraft, as if it were an extension of the wing. The body portion is attachable to an aircraft wing and includes a controllable airflow modification device coupled thereto. By virtue of having a controllable airflow modification device, the winglet is capable of adjusting a control surface of the controllable airflow modification device in response to in-flight conditions, to reduce wing loads, increase range, and/or increase efficiency.

A winglet includes a winglet body and a control body. The winglet body includes a first winglet surface arranged opposite a second winglet surface. The second winglet surface is joined to the first winglet surface to form front and trailing edges of the winglet body. The second winglet surface defines a control body seat. The control body is coupled to the winglet body to move between a stowed position seated in the control body seat and a deployed position rotated out of the control body seat. The control body includes a first control surface arranged to face toward the winglet body, a second control surface arranged opposite the first control surface to face away from the winglet body and joined to the first control surface to form a trailing edge of the control body and a control front connecting the first control surface and the second control surface.

Vortex reduction apparatus for use with airfoils are disclosed. An example vortex reduction apparatus includes a housing to couple to a tip of an airfoil. The housing defines a volute fluid flow passageway between an inlet and an outlet. The volute fluid flow passageway is structured to induce a rotational fluid flow in a first rotational direction opposite a second rotational direction of a shed vortex induced at the tip of the airfoil during flight.

Systems, devices, and methods for tracking and/or predicting motion of a wing of an aircraft are disclosed herein. The systems, devices, and methods track wing motion (e.g., in real-time). In some embodiments, the systems and devices include stereo binocular vision (SBV) cameras and/or light detection and ranging (LIDAR) emitters and receivers mounted on the aircraft. In these and other embodiments, the systems and devices include a network of contact sensors (e.g., accelerometers or strain gauges) mounted on a wing and corresponding receivers mounted on the aircraft. In these and other embodiments, based at least in part on the captured wing motion data, machine learning is employed to predict wing motion (e.g., normal, turbulent, and/or chaotic wing motion) of the aircraft.

An aircraft is disclosed having a wing, the wing having a fixed wing with a wing tip device moveably mounted about a hinge at the tip thereof. The wing tip device is operable between a flight configuration, and a load alleviating configuration for load alleviation during flight. The aircraft includes a restraining assembly operable between a restraining mode in which the wing tip device is held in the flight configuration using a restraining force such as by a brake, and a releasing mode in which the restraining force on the wing tip device is released, such that the wing tip device may adopt the load alleviating configuration.

A fluid adjustment device is provided with: a body part mounted on a wing tip, which is an end part of a main wing on the opposite side to the wing root, and having an upper opening and a lower opening formed in an upper surface of the body part and a lower surface of the body part; a first Francis turbine that sucks air from the upper opening and the lower opening and discharges the sucked air from the trailing edge side of the main wing; and a first motor for rotating the first Francis turbine in a direction opposite to a rotation direction of a wingtip vortex generated at the wingtip. The first Francis turbine has a central axis extending from the leading edge of the main wing toward the trailing edge, sucks air from the circumferential direction, and discharges the sucked air in the axial direction.

A propeller system combines innovative strategies to create a new methodology to reduce propeller or rotor noise. The propeller is specifically aimed for ultra-quiet electrically powered aircraft for use in high proximity aviation, but its low-noise advantages will extend to other purposes. The propeller blade includes geometries, along with size and operational limitations that minimize rotational and vortex noise, vibration and span-wise air flow on the blade. To further reduce noise, the propeller provides greater relative thrust on the inboard portions of the blade than do conventional propellers and provides less than conventional relative thrust including negative thrust at the outermost portions of the blade. The propeller blade includes stepped changes in local blade stiffness at calculated intervals that can reduce resonant blade vibrations and their resultant noise. This ultra-quiet propeller design can also be used for quieting hovercraft, drones, surveillance aircraft, indoor fans, wind tunnels and other applications.