An exemplary ducted fan includes a duct having a central longitudinal axis, a rotor hub and stator hub extending along the central longitudinal axis, rotor blades extending from the rotor hub, each of the rotor blades operable to rotate about its own pitch-change axis, the pitch-change axes lying in a rotor plane that is generally perpendicular to the central longitudinal axis, each of the rotor blades having a rotor trailing edge and a rotor chord length, stators extending from the stator hub to an interior surface of the duct, each of the stators having a stator leading edge and a stator thickness, and a first separation between the rotor plane and the stator leading edge of not less than approximately 1.5 times the stator thickness.

An exemplary ducted fan includes a duct having a central longitudinal axis, a rotor hub and stator hub extending along the central longitudinal axis, rotor blades extending from the rotor hub, each of the rotor blades operable to rotate about its own pitch-change axis, the pitch-change axes lying in a rotor plane that is generally perpendicular to the central longitudinal axis, each of the rotor blades having a rotor trailing edge and a rotor chord length, stators extending from the stator hub to an interior surface of the duct, each of the stators having a stator leading edge and a stator thickness, and a first separation between the rotor plane and the stator leading edge of not less than approximately 1.5 times the stator thickness.

A method of operating an unmanned aerial vehicle (UAV) includes generating, with aid of one or more processors, a signal that causes the UAV to flip from a first orientation to a second orientation opposite to the first orientation, and effecting, with aid of one or more propulsion units, flip of the UAV from the first orientation to the second orientation in response to the signal.

A method of operating an unmanned aerial vehicle (UAV) includes generating, with aid of one or more processors, a signal that causes the UAV to flip from a first orientation to a second orientation opposite to the first orientation, and effecting, with aid of one or more propulsion units, flip of the UAV from the first orientation to the second orientation in response to the signal.

A multirotor aircraft that includes a chassis, at least three engines that are equipped with propellers, and one or more axial free wings that are connected to the chassis by axial connections. The leading edges of the one or more axial free wings are designed to face constantly same direction when the multirotor flying, and the attack angles of the one or more axial free wings are designed to be changed relatively to the chassis due to flow of air over the one or more axial free wings.

A multirotor aircraft that includes a chassis, at least three engines that are equipped with propellers, and one or more axial free wings that are connected to the chassis by axial connections. The leading edges of the one or more axial free wings are designed to face constantly same direction when the multirotor flying, and the attack angles of the one or more axial free wings are designed to be changed relatively to the chassis due to flow of air over the one or more axial free wings.

An interference sensor dataset associated with interference between airflows from at least two rotors in a multicopter and a first isolated sensor dataset and a second isolated sensor dataset which are associated with isolated airflows from a first rotor and a second rotor in the multicopter, respectively, are received. A generalized flow model associated with a generalized rotor is received. An altitude for the multicopter is generated based at least in part on the interference sensor dataset, the first isolated sensor dataset, the second isolated sensor dataset, and the generalized flow model, including by using a non-linear filter that builds a consolidated probability function associated with altitude that reconciles the interference sensor dataset, the first isolated sensor dataset, and the second isolated sensor dataset with the generalized flow model.

A differential thrust vectoring system including a first thruster rotation assembly configured to rotate a first thruster relative of an aircraft, a second thruster rotation assembly configured to rotate a second thruster of an aircraft, and an actuator. The system is configured such that actuation of the actuator causes disparate rotation about the tilt axis of the first and second thrusters.

A differential thrust vectoring system including a first thruster rotation assembly configured to rotate a first thruster relative of an aircraft, a second thruster rotation assembly configured to rotate a second thruster of an aircraft, and an actuator. The system is configured such that actuation of the actuator causes disparate rotation about the tilt axis of the first and second thrusters.

An unmanned aircraft includes: rotor blades; a duct that shrouds the rotor blades and through which airflow generated by rotation of the rotor blades passes; and a processor that controls rotation of the rotor blades. The height to width ratio of an inner space of the duct in which the rotor blades are shrouded is at least 0.5.