A leading edge high-lift device, that may be deployable from a wing of an aircraft, may include a leading edge and a trailing edge. A lower surface and an upper surface may both extend between the leading edge and the trailing edge. A trailing edge region may be defined by the trailing edge and an adjacent region thereto. A shaping device may be disposed at the trailing edge region and may be movable between a non-activated position and an activated position.

A gas turbine engine nacelle comprising an intake liner. The liner includes a plurality of cells. Each cell includes an open radially inner end in fluid communication with an interior side of the nacelle, and an open radially outer end in fluid communication with an exterior side of the nacelle. Each open end of each cell defines a respective cross sectional area. The intake liner further comprises radially inner and outer facing sheets overlying a respective radially inner and outer open ends of the respective cell. Each facing sheet defines at least one aperture overlying at least one cell, an overlying portion of the respective aperture having a smaller cross sectional area than the respective open end of the respective cell.

Systems and methods according to one or more embodiments are provided for reducing noise levels in a passenger cabin of an aircraft. In one example, an aircraft includes a wing coupled to a fuselage. The wing is configured to heat air to provide a first stream of air from a central portion of a wing segment of the wing extending between the fuselage and a first engine of an aircraft. The first stream of air is at a higher temperature than an adjacent stream of air from the wing.

Sounds are generated by an aerial vehicle during operation. For example, the motors and propellers of an aerial vehicle generate sounds during operation. Disclosed are systems, methods, and apparatus for actively adjusting the position of one or more propeller blade treatments of a propeller blade of an aerial vehicle during operation of the aerial vehicle. For example, the propeller blade may have one or more propeller blade treatments that may be adjusted between two or more positions. Based on the position of the propeller blade treatments, the airflow over the propeller is altered, thereby altering the sound generated by the propeller when rotating. By altering the propeller blade treatments on multiple propeller blades of the aerial vehicle, the different sounds generated by the different propeller blades may effectively cancel, reduce, and/or otherwise alter the total sound generated by the aerial vehicle.

Sounds are generated by an aerial vehicle during operation. For example, the motors and propellers of an aerial vehicle generate sounds during operation. Disclosed are systems, methods, and apparatus for actively adjusting the position of one or more propeller blade treatments of a propeller blade of an aerial vehicle during operation of the aerial vehicle. For example, the propeller blade may have one or more propeller blade treatments that may be adjusted between two or more positions. Based on the position of the propeller blade treatments, the airflow over the propeller is altered, thereby altering the sound generated by the propeller when rotating. By altering the propeller blade treatments on multiple propeller blades of the aerial vehicle, the different sounds generated by the different propeller blades may effectively cancel, reduce, and/or otherwise alter the total sound generated by the aerial vehicle.

A core cowl for a turbofan engine may include a plurality of valleys formed in an outer surface of the core cowl. Each valley may include a convex portion upstream of a concave portion, and may be configured to disrupt a shock cell exiting a fan nozzle of the turbofan engine. Associated methods for reducing turbofan engine noise are also described.

A cavity system is provided. The cavity system (100-600) comprises: a cavity (2) and a spoiler (104-604); and the spoiler (104-604) having a front surface and a rear surface. The spoiler (104-604) is positioned in proximity to a leading edge (14) of the cavity (2), the leading edge (14) being relative to an actual or intended flow direction (3) of a fluid over the cavity (2). The spoiler (104-604) is arranged with its longitudinal axis perpendicular or at an oblique angle to the actual or intended flow direction (3) such that the front surface faces towards the flow direction (3). A first region of the spoiler (104-604) extends further toward the leading edge than a second region of the spoiler (104-604).

Ground effect acting on an aerial vehicle, such as an unmanned aerial vehicle, may be simulated by discharging a gas around propeller blades of the aerial vehicle while the propeller blades are rotating. For example, a gas, such as air, may be discharged at or near the tip of the propeller blades with enough velocity to disrupt the airflow around the blade tips, thereby altering the sound generated by rotation of the propeller blade.

Aerial vehicles may be operated with discrete sets of propellers, which may be selected for a specific purpose or on a specific basis. The discrete sets of propellers may be operated separately or in tandem with one another, and at varying power levels. For example, a set of propellers may be selected to optimize the thrust, lift, maneuverability or efficiency of an aerial vehicle based on a position or other operational characteristic of the aerial vehicle, or an environmental condition encountered by the aerial vehicle. At least one of the propellers may be statically or dynamically imbalanced, such that the propeller emits a predetermined sound during operation. A balanced propeller may be specifically modified to cause the aerial vehicle to emit the predetermined sound by changing one or more parameters of the balanced propeller and causing the balanced propeller to be statically or dynamically imbalanced.

An aerial vehicle is provided including rotor units connected to the aerial vehicle, and a control system configured to operate at least one of the rotor units. The rotor unit includes rotor blades, wherein each rotor blade includes a surface area, and wherein an asymmetric parameter is defined, at least in part, by the relationship between the surface areas of the rotor blades. The value of the asymmetric parameter is selected such that the operation of the rotor unit: (i) moves the rotor blades such that each rotor blade produces a respective vortex and (ii) the respective vortices cause the rotor unit to produce a sound output having an energy distribution defined, at least in part, by a set of frequencies, wherein the set of frequencies includes a fundamental frequency, one or more harmonic frequencies, and one or more non-harmonic frequencies having a respective strength greater than a threshold strength.