A rotorcraft includes a body and a plurality of rotary-wing parts. The body has a front-end portion, a rear-end portion, two side portions, and a reference plane passing through the front-end portion, the rear-end portion, and the two side portions. The plurality of rotary-wing parts are disposed to the body. Each of the rotary-wing parts includes at least one blade and a shaft coupled to the at least one blade. The at least one blade is rotated around an axis of the shaft. An angle between the axis of the shaft and a normal line of the reference plane is between 5 and 30 degrees. The rotorcraft can provide additional lift force, to help reduce the weight of the rotorcraft.

A rotorcraft includes a body and a plurality of rotary-wing parts. The body has a front-end portion, a rear-end portion, two side portions, and a reference plane passing through the front-end portion, the rear-end portion, and the two side portions. The plurality of rotary-wing parts are disposed to the body. Each of the rotary-wing parts includes at least one blade and a shaft coupled to the at least one blade. The at least one blade is rotated around an axis of the shaft. An angle between the axis of the shaft and a normal line of the reference plane is between 5 and 30 degrees. The rotorcraft can provide additional lift force, to help reduce the weight of the rotorcraft.

A method of forming a balanced rotor blade assembly includes measuring a weight of a plurality of sub-components of the rotor blade assembly excluding a core. A configuration of a core of the rotor blade assembly is determined. In combination, the core and the plurality of sub-components achieve a target weight distribution and moment. The core is then fabricated and assembled with the plurality of sub-components to form a rotor blade sub-assembly.

A method of forming a balanced rotor blade assembly includes measuring a weight of a plurality of sub-components of the rotor blade assembly excluding a core. A configuration of a core of the rotor blade assembly is determined. In combination, the core and the plurality of sub-components achieve a target weight distribution and moment. The core is then fabricated and assembled with the plurality of sub-components to form a rotor blade sub-assembly.

Anti-icing stacks for protecting an aerodynamic surface are described. In some embodiments, an anti-icing stack includes an anti-icing layer, an elastomeric erosion protection layer, and an additional layer. The erosion protection layer is disposed between the anti-icing layer and the additional layer. The additional layer has a thickness greater than the thickness of the erosion protection layer and a tensile modulus of no more than the tensile modulus of the erosion protection layer. The additional layer may be a foam adhesive layer.

Anti-icing stacks for protecting an aerodynamic surface are described. In some embodiments, an anti-icing stack includes an anti-icing layer, an elastomeric erosion protection layer, and an additional layer. The erosion protection layer is disposed between the anti-icing layer and the additional layer. The additional layer has a thickness greater than the thickness of the erosion protection layer and a tensile modulus of no more than the tensile modulus of the erosion protection layer. The additional layer may be a foam adhesive layer.

A rotor is described that comprises: a hub; a plurality of blades; each blade extends along an axis and comprises: a leading edge and a trailing edge; a top surface and a bottom surface, a chord joining points of the leading edge and the trailing edge; and a closed shell made of composite material and adapted to withstand the torque directed along a first axis of the blade; the shell comprises a first and a second element separate from each other, delimiting the respective shell on mutually opposite sides; a first connection element arranged on the side of the associated leading edge and interposed between the first ends of the respective first and second elements; and a third element connected to the associated first and second elements and arranged on the side of the leading edge; the first connection element is connected to respective first faces, and the third element is connected to respective second faces of the first and second elements; the blade comprises a fourth element interposed between the fourth element and the first connection element.

A rotor is described that comprises: a hub; a plurality of blades; each blade extends along an axis and comprises: a leading edge and a trailing edge; a top surface and a bottom surface, a chord joining points of the leading edge and the trailing edge; and a closed shell made of composite material and adapted to withstand the torque directed along a first axis of the blade; the shell comprises a first and a second element separate from each other, delimiting the respective shell on mutually opposite sides; a first connection element arranged on the side of the associated leading edge and interposed between the first ends of the respective first and second elements; and a third element connected to the associated first and second elements and arranged on the side of the leading edge; the first connection element is connected to respective first faces, and the third element is connected to respective second faces of the first and second elements; the blade comprises a fourth element interposed between the fourth element and the first connection element.

A rotor system includes a rotor assembly and a duct system. The rotor assembly includes rotor blades extending from a mast axis and configured to rotate about the mast axis. The duct assembly includes a moveable duct portion and a stationary duct portion. In a first duct configuration, the moveable duct portion surrounds a first portion of the rotor assembly, the stationary duct portion surrounds a second portion of the rotor assembly, and the moveable duct portion and the stationary duct portion enclose the rotor assembly. In a second duct configuration, the stationary duct portion surrounds the second portion of the rotor assembly, and the moveable duct portion is moved away from the first portion of the rotor assembly, such that the rotor assembly is not enclosed.

A rotor system includes a rotor assembly and a duct system. The rotor assembly includes rotor blades extending from a mast axis and configured to rotate about the mast axis. The duct assembly includes a moveable duct portion and a stationary duct portion. In a first duct configuration, the moveable duct portion surrounds a first portion of the rotor assembly, the stationary duct portion surrounds a second portion of the rotor assembly, and the moveable duct portion and the stationary duct portion enclose the rotor assembly. In a second duct configuration, the stationary duct portion surrounds the second portion of the rotor assembly, and the moveable duct portion is moved away from the first portion of the rotor assembly, such that the rotor assembly is not enclosed.