A flow body for an aircraft includes a recess in a surface of the flow body, a first structural component with a porous material and may also include a second structural component with a porous material. The recess includes a front recess region and a rear recess region. The first structural component is arranged in, or on, the front recess region and the second structural component may be arranged in, or on, the rear recess region. An aircraft having the flow body, a weapons system having the flow body and a method for manufacturing a flow body for a vehicle are also described.

An apparatus configured to reduce acoustic interactions between a propeller and a surface of an aircraft positioned downstream of the propeller includes a surface modification element of the surface of the aircraft. The surface modification element defines a modified contour of the surface. The modified contour is configured to decorrelate a phase distribution of a plurality of sound sources within a source field positioned on at least a portion of the surface.

Noise-abatement for a leading edge wing slat is provided by a noise-abatement airflow shield integral with the lower trailing edge of the slat, wherein the shield is reciprocally autonomously curvable from a substantially planar configuration when the slat is in a retracted position thereof and into a convexly curved configuration when the slat is in a deployed position thereof.

A noise attenuation element can be arranged for connection to an air directing structure such as a wing flap. The element has a non-uniform lattice density across at least a portion of the body of the element.

A propulsion assembly for an aircraft, the assembly including a turbojet having at least one unducted propulsive propeller, and an attachment pylon for attaching the turbojet to a structural element of the aircraft, the pylon being positioned on the turbojet upstream from the propeller and having a streamlined profile defined by two opposite side faces extending transversely between a leading edge and a trailing edge. The pylon includes a plurality of blow nozzles situated in the vicinity of its trailing edge and configured to blow air taken from a pressurized portion of the turbojet, the blow nozzles being positioned over at least a fraction of the trailing edge of the pylon that extends longitudinally facing at least a portion of the propeller. A method of reducing the noise generated by a pylon attaching a turbojet to an aircraft is presented.

A propulsion assembly for aircraft, the assembly including a turbojet having at least one unducted propulsion propeller; and an attachment pylon for attaching the turbojet to a structural element of the aircraft, the pylon being positioned on the turbojet upstream from the propeller and having an airfoil extending transversely between a leading edge and a trailing edge, the trailing edge of the airfoil of the pylon includes a cutout extending longitudinally over a fraction of the trailing edge facing at least a portion of the propeller, the cutout being configured to increase locally the distance between the trailing edge and the propeller, the cutout presenting an outline having a curved shape presenting at least two points of inflection.

Sounds are generated by an aerial vehicle during operation. For example, the motors and propellers of an aerial vehicle generate sounds during operation. Systems, methods, and apparatus may actively adjust the position and/or configuration of one or more propeller blades of a propulsion mechanism to generate different sounds and/or lifting forces from the propulsion mechanism.

A rotor system is provided in one example embodiment and may include a first pair of rotor blades comprising a first pitch and a first diameter; and a second pair of rotor blades comprising a second pitch and a second diameter, wherein the first pitch of the first pair of rotor blades and the second pitch of the second pair of rotor blades are different.

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.

A dispenser for storing and launching countermeasures from an aircraft, comprising an elongate body provided with at least one launch opening adapted for storing the countermeasures in cartridges, where the dispenser comprises a manoeuvrable spoiler arranged in front of the launch opening, where the spoiler is adapted to be fully retracted before a countermeasure has been launched, and that the spoiler is adapted to extend outwards in a predefined manner when a countermeasure has been launched. The advantage of the invention is that a spoiler will reduce induced noise from the open cartridges by extending a spoiler outwards depending on the number of launched countermeasures. This allows for a simple, reliable and cost-effective solution.