A boundary layer ingestion fan system for location aft of the fuselage of an aircraft is shown. It comprises a nacelle defining a duct, and a fan located within the duct. The fan comprises a hub arranged to rotate around a rotational axis (A-A) and a plurality of blades attached to the hub. A blade blockage, which is the ratio of the blade thickness to the product of the circumferential pitch and the cosine of a blade inlet angle (t/s.Math.cosβ.sub.1), is 0.25 or greater at the 0 percent span position.

A hybrid electric gas turbine propulsion system may comprise: a first propulsion system, a second propulsion system, and a third propulsion system. The first propulsion system may comprise a first fan, a first turbine, a first compressor, and a first electric motor, the first fan operably coupled to the first turbine and the first compressor by a first shaft, the first shaft coupled to the first electric motor, the first shaft configured to be disposed radially inward of a fuselage of an aircraft. The second propulsion system and the third propulsion system may be in accordance with the first propulsion system. The hybrid electric gas turbine propulsion system may be symmetric about a vertical plane extending through a neutral aerodynamic axis.

This instant invention provides an airplane design mainly to eject rearward the high-speed exhaust gas from the engine of the airplane to flow through the upper surface of the wing, such that the forward propulsion forcing can be obtained via rearward ejecting the high-speed exhaust gas to push the air rearward, and also larger uplift forcing induced by a larger velocity difference vertically across the wing can be obtained to ascend the airplane at the same time. This velocity difference is generated because the air over the wing is accelerated by the ejected high-speed exhaust gas, but the air below the wing stays the same velocity, such that a bigger velocity difference is directly produced vertically across the wing, and thus more uplift forcing can be provided to ascend the airplane.

An airfoil segment for inclusion in an aircraft wing is provided. The multi-element slotted airfoil segment has at least one propeller operatively located in a slot communicating therethrough for improved low speed performance and control. Upstream propeller flow field effects generated allow the front portion of the airfoil segment to be structurally efficient thicker airfoils with higher lift-to-drag laminar airfoils or higher maximum lift coefficient designs. The downstream propeller flow field acting on the aft portion of the airfoil segment increases lift and allows flaps on the aft portion to provide control forces/moments at static or low flight speeds for short or vertical take-off.

A propulsion system of an aircraft has at least one unducted fan and at least one ducted fan, the at least one unducted fan and the at least one ducted fan being powered by an electric power source and rotatable between a vertical thrust position and a forward thrust position, and a controller configured to distribute electrical power between the at least one unducted fan and the at least one ducted fan. During a first mode when the at least one unducted fan and the at least one ducted fan are in the vertical thrust position, the controller is configured to distribute the electrical power between the plurality of unducted fans and the plurality of ducted fans such that the at least one unducted fan is a primary source of thrust.

A hybrid electric gas turbine propulsion system may comprise: a first propulsion system, a second propulsion system, and a third propulsion system. The first propulsion system may comprise a first fan, a first turbine, a first compressor, and a first electric motor, the first fan operably coupled to the first turbine and the first compressor by a first shaft, the first shaft coupled to the first electric motor, the first shaft configured to be disposed radially inward of a fuselage of an aircraft. The second propulsion system and the third propulsion system may be in accordance with the first propulsion system. The hybrid electric gas turbine propulsion system may be symmetric about a vertical plane extending through a neutral aerodynamic axis.

An aircraft with an integrated boundary layer ingesting propulsion having a mechanically-distributed propulsion system. The mechanically-distributed propulsion system may include an engine to generate a mechanical drive power, a drive shaft, a direction-reversing transmission, and a propulsor fan. The drive shaft may be operatively coupled to the engine to receive the mechanical drive power. The direction-reversing transmission may have a first rotating shaft and a second rotating shaft, the first rotating shaft operatively coupled to the drive shaft to receive the mechanical drive power, which is configured to redirect the mechanical drive power received at the first rotating shaft from a first direction to face a second direction at the second rotating shaft. The propulsor fan may be coupled to the second rotating shaft to convert the mechanical drive power into thrust.

An aircraft with an integrated boundary layer ingesting propulsion having a mechanically-distributed propulsion system. The mechanically-distributed propulsion system may include an engine to generate a mechanical drive power, a drive shaft, a direction-reversing transmission, and a propulsor fan. The drive shaft may be operatively coupled to the engine to receive the mechanical drive power. The direction-reversing transmission may have a first rotating shaft and a second rotating shaft, the first rotating shaft operatively coupled to the drive shaft to receive the mechanical drive power, which is configured to redirect the mechanical drive power received at the first rotating shaft from a first direction to face a second direction at the second rotating shaft. The propulsor fan may be coupled to the second rotating shaft to convert the mechanical drive power into thrust.

An asymmetric aircraft configuration having a first and a second wing, the first wing having a span larger than the second wing. A first engine is mounted on the first wing, and a second engine mounted on the rear end of the aircraft with its centerline aligned with the aircraft longitudinal axis. The rear end of the aircraft has a T tail, and the second engine is configured to ingest and consume air forming a boundary layer during the flight. A main landing gear assembly includes a first landing gear attached to the first wing, and a second landing gear attached to an area of the fuselage close to the second wing.

Systems and methods for varying excess thrust of an aircraft include: a first electric fan rotatable about a first axis for directing a first air flow along a first air flow path; and a second electric fan rotatable about a second axis different from the first axis for directing a second air flow along a second air flow path fluidly isolated from the first air flow path, wherein the first electric fan and the second electric fan are disposed radially about a roll axis of the aircraft and adjacent an aft end of the aircraft, and the first electric fan and the second electric fan are configured to intake boundary layer air to form the first air flow and the second air flow.