The disclosure generally relates to aircraft vehicles, specifically vertical takeoff and landing (VTOL) aircraft that include propellers. A propeller is coupled to a boom and the boom includes a boom control effector. The boom control effector is configured to direct the airflow behind or below the propeller. The boom control effector can be configured to control the yaw movement of the aircraft and mitigate noise from the propeller. A boom control effector can be a single effector or a split effector. The split effector may operate in conjunction with a boom that operates as a resonator to reduce noise produced by the propeller.

An aircraft can include a stacked propeller to generate lift during assent and descent. The stacked propeller includes a first propeller and a second propeller that co-rotate about an axis of rotation. In one embodiment, the blades are coupled to a rotor mast that contains an internal cavity. In one mode of operation, the first propeller and/or the second propeller can be stored in the internal cavity in order to reduce drag during flight. The aircraft can include one or more stacked propellers, such as a port propeller and a starboard propeller, which rotate in opposite directions during one or more modes of flight.

A vertical landing and take-off aircraft VTOL transitions from a vertical takeoff state to a cruise state where the vertical takeoff state uses propellers to generate lift and the cruise state uses wings to generate lift. The aircraft has an M-wing configuration with propellers located on the wingtip nacelles, wing booms, and tail boom. The wing boom and/or the tail boom can include boom control effectors. Hinged control surfaces on the wings, tail boom, and tail tilt during takeoff and landing to yaw the vehicle. The boom control effectors, cruise propellers, stacked propellers, and control surfaces can have different positions during different modes of operation in order to control aircraft movement and mitigate noise generated by the aircraft.

In one embodiment, a tailsitter aircraft comprises a fuselage; a plurality of wings extending radially from the fuselage; a plurality of rotors coupled to the plurality of wings, wherein each rotor of the plurality of rotors is coupled to a particular wing of the plurality of wings, and wherein the plurality of rotors consists of three rotors; and at least one engine to power the plurality of rotors.

A thermal management system comprises a first heat exchanger configured to exchange heat between a first component and a first working fluid, a first working fluid compressor downstream in first working fluid flow of the first heat exchanger and configured to compress the first working fluid, a second heat exchanger downstream in first working fluid flow of the compressor and configured to exchange heat between the first working fluid and a second working fluid and an expander downstream in first working fluid flow of the second heat exchanger, and configured to expand and cool first working fluid and deliver cooled first working fluid to the first heat exchanger. The system further comprises a third heat exchanger upstream in second working fluid flow of the second heat exchanger, and configured to exchange heat between a second component and the second working fluid.

A propulsion system that includes a plurality of power units, a plurality of propulsors, where respective power units of the plurality of power units are controllably coupled to the plurality of propulsors, and a controller configured to receive a desired throttle value corresponding to a desired propulsive force, determine a number of power units of the plurality of power units to be coupled to the plurality of propulsors to achieve the desired propulsive force based on a respective power value associated with each respective power unit of the plurality of power units, and cause the number of power units of the plurality of power units to be coupled to the plurality of propulsors.

Features for a tail-sitter aircraft having efficiently designed propulsive elements are disclosed. The aircraft may have a tail with landing mounts to support the aircraft in a vertical position for takeoff and landing. The aircraft may have a hybrid propulsion system including an electric power source, such as a generator and an electric motor, and a prime power subsystem, such as an internal combustion engine. The electric and prime power subsystems may be used controllably in varying amounts depending on the phase of flight, such as takeoff, horizontal flight, landing, or maneuvers. The aircraft may have blades with piezo elements to provide shape-changing capability to the blade. The shape of the blade, such as the pitch and/or twist, may be controllably changed for optimal efficiency with the blade depending on phase of flight. The blade shape may be changed from a rotor-like shape during takeoff and landing, to a propeller-like shape during horizontal flight.

There is provided a heat management system for a hybrid electrical aircraft comprising electric propulsors powered by a power plant. The heat management system comprises a heat exchanger integrated to a nacelle of at least one of the electric propulsors for dissipating heat withdrawn from the power components of the power plant into ambient air.

Features for a tail-sitter aircraft having efficiently designed propulsive elements are disclosed. The aircraft may have a tail with landing mounts to support the aircraft in a vertical position for takeoff and landing. The aircraft may have a hybrid propulsion system including an electric power source, such as a generator and an electric motor, and a prime power subsystem, such as an internal combustion engine. The electric and prime power subsystems may be used controllably in varying amounts depending on the phase of flight, such as takeoff, horizontal flight, landing, or maneuvers. The aircraft may have blades with piezo elements to provide shape-changing capability to the blade. The shape of the blade, such as the pitch and/or twist, may be controllably changed for optimal efficiency with the blade depending on phase of flight. The blade shape may be changed from a rotor-like shape during takeoff and landing, to a propeller-like shape during horizontal flight.

An unmanned aerial vehicle comprising at least one rotor motor. The rotor motor is powered by a micro hybrid generation system. The micro hybrid generator system comprises a rechargeable battery configured to provide power to the at least one rotor motor, a small engine configured to generate mechanical power, a generator motor coupled to the small engine and configured to generate AC power using the mechanical power generated by the small engine, a bridge rectifier configured to convert the AC power generated by the generator motor to DC power and provide the DC power to either or both the rechargeable battery and the at least one rotor motor, and an electronic control unit configured to control a throttle of the small engine based, at least in part, on a power demand of at least one load, the at least one load including the at least one rotor motor.