A hybrid-electric propulsion system includes a propulsor, a turbomachine, and an electrical system. The electrical system includes a first electric machine coupled to the turbomachine and an electric energy storage unit. A method for operating the propulsion system includes operating the hybrid electric propulsion system in a flight operation mode. The method also includes operating the hybrid electric propulsion system in a maintenance operation mode, wherein operating the hybrid electric propulsion system in the maintenance operation mode includes providing electrical power from an electrical power source to the first electric machine such that the first electric machine rotates a compressor and a turbine of the turbomachine during a borescope inspection of the turbomachine.

A hybrid power or thrust generator including at least one thermodynamic turbine engine and at least one electric power generator. An electric power generator is electrically connected to at least one electric motor, mechanically and rotatably coupled to one or more rotating portions of the thermodynamic turbine engine, and the electric power generator operates simultaneously with the thermodynamic engine so as to supply the electric motor(s) to reduce the power drawn from the turbines of the thermodynamic turbine engine in operation. The electric power generator may comprise a thermoacoustic engine driving a linear electric alternator. The generator is advantageously implemented in a vehicle, such as an aircraft.

An aircraft, such as an unmanned aerial vehicle or a small-sized manned aircraft, can be hybrid-powered by fuel engines and electric motors. In various embodiments, such an aircraft can include both of rotors and fixed wings, and can perform vertical take-off and landing like a helicopter and level flight like a fixed-wing aircraft.

Embodiments refer generally to systems and methods for providing autorotative enhancement for helicopters using an autorotative assist unit coupled to the transmission of the helicopter. Methods of utilizing an autorotative assist unit as well as retrofitting an autorotative assist unit to an existing helicopter are also disclosed. By employing an autorotative assist unit, improved autorotation can be achieved without the need to increase the weight of the rotor.

A hybrid propulsion system includes a heat engine configured to drive a heat engine shaft. An electric motor is configured to drive an electric motor shaft. A transmission system includes at least one gearbox. The transmission system is configured to receive rotational input power from each of the heat engine shaft and the electric motor shaft and to convert the rotation input power to output power.

An aircraft with hybrid thermal/electrical propulsion includes a turbomachine; a first electrical source; a second electrical source equipped with an electrical energy storage device; a non-propulsion electrical distribution network; a low-voltage electrical distribution network; and a propulsion electrical distribution network. The three electrical distribution networks are electrically supplied by the first and second electrical sources and electrically interconnected by static converters.

A convertiplane is described that comprises: a fuselage, having a first longitudinal axis and, in turn, comprising a nose and a tail portion; a pair of wings arranged on respective opposite sides of the fuselage, carrying respective rotors and generating a lift value; and a pair of engines operatively connected to respective rotors; each rotor comprising a mast rotatable about a second axis between a helicopter configuration and an aeroplane configuration; each rotor is interposed between the fuselage and the relative rotor along the direction of extension of the relative wing.

During a cruise mode, a cruise-only propeller provides thrust using power from a first power source. During a hovering mode and a transitional mode, the propeller provides no thrust. The first power source includes an internal combustion engine; a second power source includes a high discharge rate battery and a high energy battery. The propeller is electrically connected to the first power source and is electrically disconnected from the second power source. During the hovering mode and the transitional mode, a hover-and-transition-only tiltrotor provides thrust using power from the second power source. During a vertical landing, the tiltrotor switches power sources from the high energy battery to the high discharge rate battery, independent of current draw. The tiltrotor is electrically disconnected from the first power source and is electrically connected to the second power source. During the cruise mode, the tiltrotor provides no thrust.

The present invention includes a distributed propulsion system for a craft that comprises a frame, a plurality of hydraulic or electric motors disposed within or attached to the frame in a distributed configuration; a propeller operably connected to each of the hydraulic or electric motors, a source of hydraulic or electric power disposed within or attached to the frame and coupled to each of the disposed within or attached to the frame, wherein the source of hydraulic or electric power provides sufficient energy density for the craft to attain and maintain operations of the craft, a controller coupled to each of the hydraulic or electric motors, and one or more processors communicably coupled to each controller that control an operation and speed of the plurality of hydraulic or electric motors.

A hybrid electric propulsion (HEP) system included in an aircraft includes a generator configured to output a first power, an energy storage system configured to output a second power, a propulsion system configured to generate thrust based on at least one of the first power and the second power, and an HEP controller in signal communication with the generator, the battery, and the HEP system. The HEP controller is configured to detect loss of the first power output from the generator, to determine an altitude of the aircraft and to actively control delivery of the second power to the propulsion system based on the altitude during the loss of the first power.