A propulsion system for an aircraft is provided having a propulsion engine configured to be mounted to the aircraft. The propulsion engine includes an electric machine defining an electric machine tip speed during operation. The propulsion system additionally includes a fan rotatable about a central axis of the electric propulsion engine with the electric machine. The fan defines a fan pressure ratio, R.sub.FP, and includes a plurality of fan blades, each fan blade defining a fan blade tip speed. The electric propulsion engine defines a ratio of the fan blade tip speed to electric machine tip speed that is within twenty percent of the equation, 1.68R.sub.FP0.518, such that the propulsion engine may operate at a desired efficiency.

An aircraft includes a fuselage, a forward wing assembly, and aft wing assembly, and a propulsion system. The propulsion system includes a port forward propulsor and a starboard forward propulsor, each of which rotatable between a forward thrust position and a vertical thrust position and together defining a maximum forward thrust capability. The propulsion system also includes a port aft propulsor and a starboard aft propulsor, each of which also rotatable between a forward thrust position and a vertical thrust position, and together defining a maximum aft thrust capability. The maximum forward thrust capability is different than the maximum aft thrust capability to achieve certain efficiencies.

An assembly for an aircraft having a propeller, including a wheel well configured for receiving a retracted landing gear, the wheel well including walls and a closable bottom opening for deploying the landing gear therethrough, an engine assembly having an engine shaft configured for driving engagement with the propeller, and a mount assembly for supporting the engine assembly, the mount assembly connected to at least one of the walls of the wheel well. A method of supporting an engine assembly in an aircraft having a retractable landing gear and a propeller driven by the engine assembly is also discussed.

An assembly for an aircraft having a propeller, including a wheel well for a retracted landing gear, first and second cooling ducts; and an engine assembly having an engine shaft configured for driving engagement with the propeller, the engine assembly including a coolant circulation system for circulation of a liquid coolant, a lubricant circulation system for circulation of a lubricant, a first heat exchanger in fluid communication with at least the coolant circulation system, and a second heat exchanger in fluid communication with at least the lubricant circulation system. Each heat exchanger is positioned and configured for receiving a cooling airflow from the respective cooling duct. The wheel well is located between the heat exchangers. A method of cooling a lubricant and a liquid coolant of an engine assembly is also discussed.

An assembly for an aircraft having a propeller, including an engine assembly having an engine shaft configured for driving engagement with the propeller. The engine assembly includes first and second heat exchangers configured for circulation of at least one of a liquid coolant and a lubricant therethrough. A wheel well is configured for receiving a retracted landing gear. A first cooling duct receives the first heat exchanger and has a first outlet downstream of the first heat exchanger, and a second cooling duct receives the second heat exchanger and has a second outlet downstream of the second heat exchanger. The outlets are in direct fluid communication with an environment of the aircraft, and laterally spaced from each other. The wheel well is located between the outlets. A method of cooling an engine assembly is also discussed.

Systems and methods of augmenting the thrust of the prime power engine(s) of an aircraft from a tank of compressed gas are described herein.

Variations of an aerial vehicle, all with capability of vertical take-off and landing (VTOL), with one variation comprising at least three engines, at least three rotors, a flight control system, battery, and propulsion system. The second VTOL aerial vehicle variation being a hybrid with engine-powered rotors and electric-powered rotors configured to work with a flight control system and battery. The first and second variations having the option of a genset system which recharges the battery. The third VTOL aerial vehicle variation being all-electric-powered rotors configured to work with a flight control system and a genset system which powers the rotors and/or recharges the battery.

A method and apparatus for lifting a payload wherein a first mechanical-rotor is driven by an internal combustion engine. A portion of the mechanical work developed by the internal combustion engine is used to generate electrical power, which is either stored in a battery or used to power an electric motor that drives a second rotor. Thrust developed by the mechanical and electrical rotors is directed downward to provide lift for the payload.

A method for operating a propulsion system of an aircraft includes moving a plurality of forward and aft propulsors to a vertical thrust position. While in the vertical thrust positions, the method also includes providing a first forward to aft ratio of electric power to the plurality of forward and aft propulsors. The method also includes moving the plurality of forward and aft propulsors to a forward thrust position. While in the forward thrust positions, the method also includes providing a second forward to aft ratio of electric power to the plurality of forward and aft propulsors. The first forward to aft ratio of electric power is different than the second forward to aft ratio of electric power to provide certain efficiencies for the aircraft.

An aircraft includes a fuselage and a wing assembly attached to or formed integrally with the fuselage. The aircraft also includes a propulsion system having a port propulsor and a starboard propulsor. The port and starboard propulsors are each attached to the wing assembly on opposing sides of the fuselage and are rotatable between a forward thrust position and a vertical thrust position. The propulsion system also includes a supplemental propulsor mounted to the fuselage to provide certain efficiencies for the aircraft.