Abstract: A method of operating an electrically powered rotorcraft of the type having a fuselage and a set of N rotors driven by a set of electric motors and coupled to the fuselage, N?4, under a failure condition preventing ordinary operation of the rotorcraft. The method includes entering a failsafe mode of operation wherein autorotation of at least four of the rotors is enabled. The method also includes using electrical braking associated with a selected group of the rotors to control pitch, roll and yaw of the rotorcraft.

Abstract: An improved electrically powered rotorcraft is of the type having a rotor including a rotor hub and a pair of rotor blades mounted to the rotor hub on opposite sides thereof, the rotor being rotatably mounted on a primary drive shaft, and a rotary electric motor coupled to the drive shaft. In this rotorcraft, the improvement includes a common pitch-angle shaft coupled to each of the blades; a limited-angle electric motor, mechanically coupled to the common pitch-angle shaft, and configured to cause rotation of the common pitch angle shaft and therefore adjustment of pitch of the pair of rotor blades; and a controller system in communication with the limited-angle electric motor, configured to provide cyclic control of pitch of the pair of rotor blades.

Abstract: A contra-rotating electric helicopter utilizes an electric motor having a base and an output shaft and a power source. The helicopter couples the base to a first rotor, thus allowing both the base and the power source to rotate within the frame of reference of the first rotor, while a contra-rotating and coplanar second rotor is coupled to the output shaft of the electric motor.

Abstract: An improved vertical takeoff aircraft of the type having a set of pads that are in contact with the ground when the aircraft is at rest on the ground and a controllable lift and propulsion system. The aircraft includes an array of force sensors coupled to the set of pads. The array has an output providing measurements over time of forces exerted on the pads along at least two independent axes. The aircraft also includes a controller, coupled to the lift and propulsion system and to the array of force sensors. The controller is configured to control the lift and propulsion system in a manner to counteract forces exerted externally on the aircraft that would cause undesired motion of the aircraft when on the ground and transitioning from the ground to flight.

Abstract: A method of operating an electrically powered rotorcraft of the type having a fuselage and a set of N rotors driven by a set of electric motors and coupled to the fuselage, N?4, under a failure condition preventing ordinary operation of the rotorcraft. The method includes entering a failsafe mode of operation wherein autorotation of at least four of the rotors is enabled. The method also includes using electrical braking associated with a selected group of the rotors to control yaw of the rotorcraft.

Abstract: An improved rotorcraft of the type having a fuselage and a set of N?4 rotors. The rotorcraft includes a structural support system affixed to the fuselage and mounting the set of rotors. The support system is configured as a set of airfoils that provide lift when the fuselage is in level flight. The fuselage has a central longitudinal axis that defines the direction of forward flight of the rotorcraft. Each of the rotors defines a corresponding rotational plane, that is tilted forward in the direction of the forward flight, when the central longitudinal axis of the fuselage is horizontal. Each airfoil may be positioned so that a majority of its length is disposed beneath the rotational plane of its corresponding rotor. When the rotorcraft is at a cruise speed, the airfoils are configured to provide lift that approximately matches the lift provided by the rotors.