A method and apparatus are presented. An active flow control system comprises a flow control valve, a manifold, and a temperature control system. The flow control valve is configured to control a flow of air into the manifold. The manifold is operatively connected to a number of actuators. The temperature control system is configured to heat at least a portion of the flow of air.

An aircraft inlet comprising an annular air intake structure defined by an inner surface and an outer surface, a plurality of perforations formed in the outer surface of the aircraft inlet, a plenum chamber situated within the aircraft inlet and configured to receive air entering the plurality of perforations, and/or a plurality of sensors disposed about the outer surface of the aircraft inlet, each sensor associated with a region of the plurality of perforations. Each sensor may comprise a hot film anemometer. The aircraft inlet may further comprise a regulator coupled at one end to the plenum chamber and at another end to a pump, wherein the regulator regulates a suction produced by the pump.

A propulsion system for an aircraft includes an electric propulsion engine configured to be mounted to the aircraft at an aft end of the aircraft. The electric propulsion engine includes a fan rotatable about a central axis of the electric propulsion engine. The fan includes a fan shaft mechanically coupled to a power gearbox. The electric propulsion engine also includes an electric motor having a driveshaft, with the electric motor coupled to the power gearbox through the drive shaft. The electric motor rotates the fan through the power gearbox. The driveshaft includes a flexible element for accommodating a misalignment of the electric motor and the power gearbox.

A propulsion system for an aircraft includes an electric propulsion engine configured to be mounted to the aircraft at an aft end of the aircraft. The electric propulsion engine includes a power gearbox mechanically coupled to an electric motor. The electric propulsion engine further includes a fan rotatable about a central axis of the electric propulsion engine by the electric motor through the power gearbox. Moreover, the electric propulsion engine includes an attachment assembly for mounting at least one of the electric motor or the power gearbox. The attachment assembly includes a torsional damper for accommodating a torsional vibration of the electric motor or the power gearbox.

Technologies are described herein for a drag recovery scheme using a boundary layer bypass duct system. In some examples, boundary layer air is routed around the intake of one or more of the engines and reintroduced aft of the engine fan in the nozzle duct in a mixer-ejector scheme. Mixer-ejectors mix the boundary layer flow to increase mass flow.

A system for controlling aircraft boundary layer airflow comprising a frame structure configured to be coupled or integral to an inner surface of an aircraft nacelle, the frame configured to support to the nacelle, and/or a modular plenum configured to be received by the frame structure, the modular plenum comprising a truncated tetrahedron intersected at its apex by a duct. The frame may comprise a plurality of sub-frames. The system may further comprise a plurality of modular plenums, each configured to fit within a sub-frame. The system may further comprise a flexible material configured to couple a first duct to a second duct. The system may further comprise a nacelle configured to receive the system.

A swept gradient air boundary layer diverter for an aircraft. The aircraft includes a fuselage and an air inlet for an engine of the aircraft, where the air inlet includes a cowl at a leading edge of the inlet. The diverter includes a V-shaped ramp portion formed in the fuselage in an area proximate to and in front of the cowl where the ramp portion extends downward away from an outer surface of the fuselage towards an inside of the aircraft. The diverter also includes a V-shaped trough portion formed into the fuselage and being positioned adjacent to and integral with the ramp portion between the ramp portion and the air inlet. Air flowing over the fuselage towards the cowl is expanded and compressed by the ramp portion and the trough portion so as to create pressure gradients that generate vortices to redirect boundary layer airflow around the air inlet.

An active laminar flow control arrangement may comprise a modular arrangement comprising a plurality of frames and cover panels coupled to an outer skin having a plurality of hat stiffeners and stringers. A first cover panel may be coupled between a first frame and a first hat stiffener. A second cover panel may be coupled between a second frame and a second hat stiffener. A third cover panel may be coupled between the first cover panel and the second cover panel. The cover panels may enclose associated plenums whereby a flow of air is pumped into the arrangement for maintaining a laminar flow across an aerodynamic surface of the outer skin.

Technologies are described herein for a drag recovery scheme using a boundary layer bypass duct system. In some examples, boundary layer air is routed around the intake of one or more of the engines and reintroduced aft of the engine fan in the nozzle duct in a mixer-ejector scheme. Mixer-ejectors mix the boundary layer flow to increase mass flow.

An inlet for use with a nacelle having an axis includes an outer barrel. The inlet further includes a lip skin defining a plurality of elongated exit holes including a first circumferential outer hole, a second circumferential outer hole, and a plurality of center holes located between the first circumferential outer hole and the second circumferential outer hole, the first circumferential outer hole being located at least 10 degrees of an entire circumference of the inlet away from the second circumferential outer hole.