An airfoil section of a blade for an open rotor includes: a pressure side and a suction side, the pressure side and the suction side intersecting at a leading edge and a trailing edge, wherein a chord of the airfoil section is defined as a straight-line distance between the leading edge and the trailing edge; the airfoil section has a meanline defined midway between the pressure side and the suction side; and the meanline is shaped such that, in the presence of predetermined transonic or supersonic relative velocity conditions, maximum and minimum ideal Mach numbers on the suction side will lie within a 0.08 band, between 25% and 80% percent of the chord.

An aircraft includes a fuselage having a tail section and an engine core coupled via an external pylon to the fuselage. The aircraft further includes a boundary layer ingestion (BLI) fan coupled to the tail section of the fuselage and coupled via a shaft to the engine core.

Aspects of the disclosure are directed to a nacelle of an aircraft, comprising a surface that is profiled such that during cruise flight operation lines of constant static pressure of a boundary layer around the nacelle in a given region are substantially contained within a plane that is normal to an engine axis.

An air duct arrangement (58) for an aircraft (40). The arrangement (58) comprises an environmental control system (ECS) (50). The ECS (50) comprises an air inlet (60) arranged to ingest a low velocity portion of a boundary layer flow adjacent the aircraft fuselage (44), and to deliver a flow of air to an environmental control system air intake (66). The arrangement (58) further comprises an ejector (70) arranged to receive an ECS exhaust (76), and boundary layer air from an aft region of the aircraft (40), and to exhaust air to the ambient airstream at an aft portion of the aircraft (40).

An aircraft is equipped with multiple fans for boundary layer ingestion. The aircraft comprises a fuselage, having an exterior surface and a rearward-most end. The aircraft also comprises a plurality of fans that are fixed to and positioned about the exterior surface of the fuselage at an axial location forward of the rearward-most end of the fuselage. Each one of the plurality of fans comprises a plurality of fan blades and a fan drive configured to rotate the plurality of fan blades. The plurality of fan blades are positioned at lateral locations relative to the exterior surface of the fuselage such that when rotated by the fan drive the plurality of fans receive and accelerate fuselage boundary layer air flow, along the exterior surface of the fuselage, from a first average velocity to a second average velocity, greater than the first average velocity, when the aircraft is in flight.

An aircraft is equipped with multiple fans for boundary layer ingestion. The aircraft comprises a fuselage, having an exterior surface and a rearward-most end. The aircraft also comprises a plurality of fans that are fixed to and positioned about the exterior surface of the fuselage at an axial location forward of the rearward-most end of the fuselage. Each one of the plurality of fans comprises a plurality of fan blades and a fan drive configured to rotate the plurality of fan blades. The plurality of fan blades are positioned at lateral locations relative to the exterior surface of the fuselage such that when rotated by the fan drive the plurality of fans receive and accelerate fuselage boundary layer air flow, along the exterior surface of the fuselage, from a first average velocity to a second average velocity, greater than the first average velocity, when the aircraft is in flight.

An aircraft and flow guide system including a flow guide structure are provided. The aircraft has an airflow generator, and a duct extending from the airflow generator to an outlet through which an airflow generated by the airflow generator is expelled. The flow guide structure is positioned towards the outlet, and has a set of flow guide surfaces defining a plurality of channels. At least some of the flow guide surfaces divert at least some of the airflow from a first direction in which the airflow travels immediately upstream of the flow guide structure towards a second direction that is orthogonal to the first direction. The flow guide structure is reorientable to cause the at least some of the flow guide surfaces to divert at least some of the airflow towards a third direction that is orthogonal to the first direction.

An aircraft and flow guide system including a flow guide structure are provided. The aircraft has an airflow generator, and a duct extending from the airflow generator to an outlet through which an airflow generated by the airflow generator is expelled. The flow guide structure is positioned towards the outlet, and has a set of flow guide surfaces defining a plurality of channels. At least some of the flow guide surfaces divert at least some of the airflow from a first direction in which the airflow travels immediately upstream of the flow guide structure towards a second direction that is orthogonal to the first direction. The flow guide structure is reorientable to cause the at least some of the flow guide surfaces to divert at least some of the airflow towards a third direction that is orthogonal to the first direction.

An aircraft includes an airframe, an engine mounted to the airframe, and an engine inlet for receiving an ambient airflow and providing the ambient airflow to the engine. An amount of airflow provided to the engine inlet is controllable.

A propulsion system for an aircraft comprises at least two main gas turbine engines and a plurality of dedicated boundary layer ingestion fans. An aircraft is also disclosed.