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 thrust reverser for an aircraft propulsion assembly, this reverser including an outer structure movable between a closed position and an open position of two primary latches configured to lock the movable outer structure in the closed position. The movable outer structure includes an output end that is oblique with respect to the longitudinal central axis so as to orient the thrust laterally. In order to compensate the tilting moment of the movable outer structure, which results from this lateral orientation of the thrust, the primary latches are offset with respect to a median longitudinal plane passing through the longitudinal central axis of the reverser.

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 nacelle for a gas turbine engine includes a ring shaped body defining a center axis and having a radially outward surface and a radially inward surface. An aft portion of the radially inward surface includes an axially extending convergent-divergent exit nozzle. An axially extending secondary duct passes through the nacelle in the convergent-divergent exit nozzle. The axially extending secondary duct includes an inlet at a convergent portion of the convergent-divergent exit nozzle and an outlet at a divergent portion of the convergent-divergent exit nozzle.

A nacelle for a gas turbine engine includes a ring shaped body defining a center axis and having a radially outward surface and a radially inward surface. An aft portion of the radially inward surface includes an axially extending convergent-divergent exit nozzle. An axially extending secondary duct passes through the nacelle in the convergent-divergent exit nozzle. The axially extending secondary duct includes an inlet at a convergent portion of the convergent-divergent exit nozzle and an outlet at a divergent portion of the convergent-divergent exit nozzle.

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 disclosed turbofan engine includes a gas generator section for generating a gas stream flow and a propulsor section for generating propulsive thrust as a mass flow rate of air through a bypass flow path. The propulsor section includes a fan driven by a power turbine through a speed reduction device at a second rotational speed lower than a first rotational speed of the power turbine. An Engine Unit Thrust Parameter (“EUTP”) defined as net engine thrust divided by a product of the mass flow rate of air through the bypass flow path, a tip diameter of the fan and the first rotational speed of the power turbine is between 0.05 and 0.13 during operation of the turbofan engine.

A disclosed turbofan engine includes a gas generator section for generating a gas stream flow and a propulsor section for generating propulsive thrust as a mass flow rate of air through a bypass flow path. The propulsor section includes a fan driven by a power turbine through a speed reduction device at a second rotational speed lower than a first rotational speed of the power turbine. An Engine Unit Thrust Parameter (“EUTP”) defined as net engine thrust divided by a product of the mass flow rate of air through the bypass flow path, a tip diameter of the fan and the first rotational speed of the power turbine is between 0.05 and 0.13 during operation of the turbofan engine.

A boundary layer ingestion fan system for location aft of the fuselage of an aircraft is shown. It comprises a nacelle (501) defining a duct (502), and a fan (503) 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. Each blade has a span (r) from a root at the hub defining a 0 percent span position (r=0) to a tip defining a 100 percent span position (r=1) and a plurality of span positions therebetween (r ∈ [0, 1]), and a stagger angle at the 0 percent span position (ζ.sub.hub) relative to the rotational axis of 40 degrees or greater.

A nozzle having a forward portion skewed downwards and an aft portion translated downwards provides sufficient clearance between the nozzle and the heat shield structure to prevent contact in the event of large deflections (e.g., as associated with a fan blade Out (FBO) condition). Such large deflections must be accounted for to meet federal aviation regulations and gain airplane CFR 14 Part 25 Certification.