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.

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 variable-solidity propeller apparatus, comprising a propeller having at least one rotatable hub carrying at least one row of propeller blades, wherein the propeller has a first configuration in which the propeller has a first average solidity, and a second configuration in which the propeller has a second average solidity which is greater than the first average solidity.

An aircraft turbine engine has a pair of rotating and non-ducted propellers. An upstream propeller has an outer diameter D1 and a downstream propeller has an outer diameter D2. The engine further includes a system for varying the diameter D2. The downstream propeller includes an annular row of blades, each of which is configured to be mounted telescopically in the radial direction (R) in an outer fan duct.

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 variable-solidity propeller apparatus, comprising a propeller having at least one rotatable hub carrying at least one row of propeller blades, wherein the propeller has a first configuration in which the propeller has a first average solidity, and a second configuration in which the propeller has a second average solidity which is greater than the first average solidity.

A method and apparatus for controlling a propeller of a contra-rotation open fan (CROF) engine of an aircraft is provided. A diameter of the propeller is set to be at a first diameter during at least a portion of a first flight condition of the aircraft. The diameter of the propeller is set to be at a second diameter, different from the first diameter, during at least a portion of a second flight condition of the aircraft.

A retractable rotor system for an aircraft includes a rotor blade with a leading edge, a trailing edge, and an internal collapsible web. The leading edge includes a flexible portion whose lower edge contacts but is not structurally joined to the lower skin. When the leading edge is peeled forward from the lower skin, the blade elastically collapses to the thickness of its constituent layers. The rotor blade extends through a support frame connectable to the aircraft to secure the rotor blade to a spool. Rotating the spool retracts the rotor blade through the support frame while pulling the rotor blade over a fixed actuating member, placing the rotor blade in the collapsed condition and winding the rotor blade onto the spool. Rotating the spool in the opposite direction unwinds the rotor blade from the spool, through the frame, causing the rotor blade to relax into the expanded condition.

A drone with a horizontal rotor includes one or more rotor(s) (115, 116) which rotate in a horizontal plane, each rotor (115, 116) being equipped with one or more rigid or non-rigid blades (120, 121), the blade end being mounted on an electric motor (110, 111) with a propeller.