Abstract: A method for operating a vertical takeoff and landing aircraft includes modifying a first variable component of a wing associated with a first portion of the plurality of vertical thrust electric fans relative to a second variable component of the wing associated with a second portion of the plurality of vertical thrust electric fans to adjust an exposure ratio of the first portion of the plurality of vertical thrust electric fans relative to the second portion of the plurality of vertical thrust electric fans.

Abstract: A fan for a gas turbine engine is provided. The fan includes a rotor including at least one rotor stage having a rotatable disk defining a flowpath surface and an array of rotor airfoils extending outward from the flowpath surface; an array of splitter airfoils extending outward from the flowpath surface, wherein the splitter airfoils and the rotor airfoils are disposed in a sequential arrangement; and a shroud extending between the rotor airfoils and the splitter airfoils.

Abstract: A method of controlling a transition from a laminar flow to a turbulent flow for an airfoil of a turbomachine includes forming an airfoil. The airfoil defines a span extending between a root and a tip and a chord extending between a leading edge and a trailing edge. The airfoil includes a suction side surface and a pressure side surface, opposite the suction side surface, each extending between the leading edge, the trailing edge, the root, and the tip. The method also includes finishing a majority of the suction and pressure side surfaces in order to form a finished surface. The finished surface defines a first roughness. The method additionally includes leaving at least a portion of the suction side surface and/or pressure side surface unfinished in order to form an unfinished surface. Furthermore, the unfinished surface defines a second roughness greater than the first roughness.

Abstract: A propulsion system is provided, the propulsion system including a rotor assembly configured to rotate relative to the engine centerline axis, and wherein one or more blades of the rotor assembly are configured to rotate along a blade pitch angle axis. A vane assembly is positioned in aerodynamic relationship with the rotor assembly. The vane assembly includes one or more vanes, wherein each vane includes a vane pitch angle. A controller is configured to execute operations, the operations including moving each blade to a reverse thrust position about its respective blade pitch axis, and adjusting each vane about its respective vane pitch axis when the plurality of blades is in the reverse thrust position to modify an amount of reverse thrust generated by the propulsion system.

Abstract: A propulsion system according to aspects of the present disclosure is provided, the propulsion system including a rotor assembly with a plurality of blades extended radially relative to the engine centerline axis, and a vane assembly positioned in aerodynamic relationship with the rotor assembly. The vane assembly includes a plurality of vanes extended radially relative to the engine centerline axis, and the propulsion system includes a ratio of a quantity of blades to a quantity of vanes between 2:5 and 2:1.

Abstract: An aircraft extending between a forward end and an aft end is provided. The aircraft includes an auxiliary power unit positioned proximate the aft end of the aircraft, the auxiliary power unit having an auxiliary power unit inlet duct and an auxiliary power unit exhaust duct, and a boundary layer ingestion fan positioned proximate the aft end of the aircraft, the boundary layer ingestion fan having a support shaft, wherein the auxiliary power unit exhaust duct extends through a portion of the support shaft of the boundary layer ingestion fan.

Abstract: A method is provided of operating a single unducted rotor engine, the single unducted rotor engine comprising a single stage of unducted rotor blades. The method includes operating the single unducted rotor engine to define a flight speed, V0, in a length unit per second and an angular speed, n, in revolutions per second, the single stage of unducted rotor blades defining a diameter, D, in the length unit; wherein operating the single unducted rotor engine comprises operating the single unducted rotor engine to define an advance ratio greater than 3.8 while operating the single unducted rotor engine at a net efficiency of at least 0.8, the advance ratio defined by the equation V0/(n×D).

Abstract: A unshrouded vane assembly for an unducted propulsion system includes a plurality of vanes which have non-uniform characteristics configured to generate a desired vane exit swirl angle.

Abstract: An apparatus and method of managing negative incidence of an airfoil are provided. The apparatus includes a row of vane pairs including a first row of main vanes extending radially inwardly from a stationary casing member and spaced circumferentially about a first axial location of the stationary casing member. The apparatus also includes a second row of auxiliary vanes extending radially inwardly from the stationary casing member and spaced circumferentially about a second axial location of the stationary casing member. The apparatus also includes a flow channel defined between a pressure side of each auxiliary vane and a suction side of an adjacent main vane proximate a leading edge of the adjacent main vane.

Abstract: An aircraft includes a fuselage; a wing coupled to, and extending from, the fuselage; and a hybrid-electric propulsion system. The hybrid-electric propulsion system includes a power source including a combustion engine and an electric generator; a plurality of vertical thrust electric fans integrated into the wing and oriented to generate thrust along the vertical direction, the plurality of vertical thrust electric fans arranged along a length of the wing and driven by the power source; and a forward thrust propulsor. The forward thrust propulsor it is selectively or permanently mechanically coupled to the combustion engine.

Abstract: An unducted thrust producing system, includes a rotating element, a stationary element. An inlet may be located forward or aft of the rotating element and the stationary element. An exhaust may be located forward, aft, or between the rotating element and the stationary element.

Abstract: A noise reducing airfoil defining a span extending between a root and a tip and a chord at each point along the span extending between a leading edge and a trailing edge. The airfoil includes a pressure side, a suction side, and a trailing edge sheath including an outer surface coupled to the trailing edge of the airfoil. The trailing edge sheath extends at least partially along the chord on the pressure and suction sides at each point along the span within the trailing edge sheath. The trailing edge sheath defines a fluid passageway extending along at least a portion of the span. Further, the trailing edge sheath defines at least one aperture on at least one of the pressure side, the suction side, or trailing edge fluidly coupling the fluid passageway to the outer surface.

Abstract: A unshrouded vane assembly for an unducted propulsion system includes a plurality of vanes which have non-uniform characteristics configured to generate a desired vane exit swirl angle.

Abstract: A gas turbine engine is provided including a turbine section including a turbine having a plurality of first speed turbine rotor blades; a compressor section including a compressor having a plurality of first speed compressor rotor blades and a plurality of second speed compressor rotor blades; a gearbox; and a first spool rotatable by the plurality of first speed turbine rotor blades, the first spool coupled to the plurality of first speed compressor rotor blades for driving the plurality of first speed compressor rotor blades in a first direction and to the plurality of second speed compressor rotor blades across the gearbox for driving the plurality of second speed compressor rotor blades in a second direction, opposite the first direction.

Abstract: An aircraft includes a fuselage; a wing coupled to, and extending from, the fuselage; and a propulsion system. The propulsion system includes a plurality of electric fans integrated into the wing and oriented to generate thrust along a vertical direction, the plurality of electric fans arranged along a length of the wing and including an outer-most electric fan along a transverse direction relative to the fuselage. The outer-most electric fan is at least one of a variable pitch fan or a variable speed fan to provide increased stability to the aircraft.

Abstract: An unducted thrust producing system has a rotating element with an axis of rotation and a stationary element. The rotating element includes a plurality of blades, and the stationary element has a plurality of vanes configured to impart a change in tangential velocity of the working fluid opposite to that imparted by the rotating element acted upon by the rotating element. The system includes an inlet forward of the rotating element and the stationary element.

Abstract: A shroud assembly for a gas turbine engine includes: at least one shroud hanger; an annular array of shroud segments carried by the child hanger at least one and arrayed about an engine centerline axis, each of the shroud segments having a flowpath side defining a portion of a primary engine flowpath, and an opposed backside facing the at least one shroud hanger, wherein the shroud segment is mounted to the at least one shroud hanger such that it is movable in a radial direction between an inboard position and an outboard position, in response to a balance of gas pressures prevailing on the flowpath side and the backside; and biasing means which urge each of the shroud segments towards one of the positions.

Abstract: A unshrouded vane assembly for an unducted propulsion system includes a plurality of vanes which have non-uniform characteristics configured to generate a desired vane exit swirl angle.

Abstract: A noise reducing airfoil defining a span extending between a root and a tip and a chord at each point along the span extending between a leading edge and a trailing edge. The airfoil includes a pressure side, a suction side, and a trailing edge sheath including an outer surface coupled to the trailing edge of the airfoil. The trailing edge sheath extends at least partially along the chord on the pressure and suction sides at each point along the span within the trailing edge sheath. The trailing edge sheath defines a fluid passageway extending along at least a portion of the span. Further, the trailing edge sheath defines at least one aperture on at least one of the pressure side, the suction side, or trailing edge fluidly coupling the fluid passageway to the outer surface.

Abstract: A lift fan apparatus includes: a rotor having at least one rotatable hub carrying at least one row of blades; a duct surrounding the rotor, the duct including spaced-apart peripheral walls extending between an inlet and an exit, the peripheral walls collectively defining a flow channel which includes a diffuser disposed downstream of the rotor, in which a flow area at the exit is greater than a flow area at the rotor; and a plurality of spaced-apart splitters disposed in the diffuser, each of the splitters having opposed side walls extending between an upstream leading edge and a downstream trailing edge, wherein the splitters divide the diffuser into a plurality of side-by-side flow passages.