A tiltrotor aircraft includes a fuselage, a wing member extending from the fuselage, an engine disposed relative to the wing member and a proprotor mechanically coupled to the engine. The proprotor includes a plurality of proprotor blade assemblies each including a spar and a sheath extending spanwise along the spar forming the leading edge of the proprotor blade assembly. The spar has a root section, a main section and a tip section. The spar has a generally oval cross section at radial stations along the main section and a first edge having a structural bias relative to a generally oppositely disposed second edge at the radial stations along the main section.

In a first aspect, there is a method for improving a lift to drag ratio of a rotor blade, including providing a blade member having a leading edge and a trailing edge; providing a leading edge extension member; and coupling the leading edge extension member to a portion of the leading edge of the blade member to form the rotor blade. In a second aspect, there is a rotor blade including a blade member having a leading edge, and a trailing edge; and a leading edge extension member disposed on the leading edge of the blade member, wherein the leading edge extension member is configured to extend the chord length of at least a portion of the rotor blade. In a third aspect, there is a leading edge extension member for a rotor blade including a convex exterior surface configured to extend at least a portion of the chord length of the rotor blade.

In a first aspect, there is a method for improving a lift to drag ratio of a rotor blade, including providing a blade member having a leading edge and a trailing edge; providing a leading edge extension member; and coupling the leading edge extension member to a portion of the leading edge of the blade member to form the rotor blade. In a second aspect, there is a rotor blade including a blade member having a leading edge, and a trailing edge; and a leading edge extension member disposed on the leading edge of the blade member, wherein the leading edge extension member is configured to extend the chord length of at least a portion of the rotor blade. In a third aspect, there is a leading edge extension member for a rotor blade including a convex exterior surface configured to extend at least a portion of the chord length of the rotor blade.

An unducted fan having variable pitch blades for an aircraft or wind propulsion system is described. The fan includes a hub provided with housings pivotally receiving vanes about radial axes, and an outer casing of the hub into which circular openings of the housings open. Each vane includes a root which is rotatably mounted in the associated housing, a radially oriented blade and a disc-shaped platform extending from the blade to an edge of the circular opening. The blade includes at least one skin which includes a free lower edge facing the side of the root, wherein the platform is attached to the free lower edge of the skin.

A blade, for a rotor of an aircraft, comprising a hollow cylindrical sleeve, a stop fastened to the cylindrical sleeve, a profiled portion, and an anchoring device, a blade body and a hollow torsion box secured to the profiled portion. The anchoring device and the blade body are positioned inside the cylindrical sleeve. The anchoring device surrounds the stop in order to form a stop for the profiled portion parallel to a longitudinal axis of the blade. The hollow torsion box is secured to the profiled portion, and comprises a bearing zone in contact with an inner wall of the cylindrical sleeve, taking up the bending loads on the blade.

A blade, for a rotor of an aircraft, comprising a hollow cylindrical sleeve, a stop fastened to the cylindrical sleeve, a profiled portion, and an anchoring device, a blade body and a hollow torsion box secured to the profiled portion. The anchoring device and the blade body are positioned inside the cylindrical sleeve. The anchoring device surrounds the stop in order to form a stop for the profiled portion parallel to a longitudinal axis of the blade. The hollow torsion box is secured to the profiled portion, and comprises a bearing zone in contact with an inner wall of the cylindrical sleeve, taking up the bending loads on the blade.

A method is provided for installing an add-on component to a surface of a wind turbine blade, as well as the blade with attached add-on component, and the add-on component as a stand-alone device. A slot is defined in one or both of the pressure side or suction side surfaces of the add-on component. The adhesive side of strips of a double-sided adhesive tape are attached onto either the surface of the wind turbine blade or an interior surface of the add-on component, the tape strips having a release liner on an opposite exposed side thereof. The tape strips are arranged longitudinally along one or both sides of the slot, and each strip has an extension tail that extends beyond an edge of the add-on component when component is held at a desired position against the surface of the wind turbine blade. The extension tails are pulled along the slot at an angle such that that release liner is removed through the slot along the length of the tape strip while maintaining the desired position of the add-on component against the surface of the wind turbine blade.

A method for installing an add-on component to a surface of a wind turbine blade includes attaching an adhesive side of strips of a double-sided adhesive tape onto either the surface of the wind turbine blade or a surface of the add-on component, the tape strips having a release liner on an opposite exposed side thereof. The tape strips having an extension tail of the release liner that extends beyond an edge of the add-on component when the add-on component is placed and held at a desired position against the surface of the wind turbine blade. With the add-on component held at the desired position, the extension tail is pulled away at an angle such that that release liner is removed along the length of the tape strip while maintaining the add-on component against the blade surface to attach the exposed adhesive under the release liner to either the surface of the wind turbine blade or the surface of the add-on component.

A method for installing an add-on component onto a tip of a wind turbine blade, the associated blade, and the component, are provided. The add-on component has a span-wise end and a separated trailing edge, and is slidable onto the blade tip. Strips of a double-sided adhesive tape are attached onto either or both pressure and suction side surfaces of the blade adjacent the blade tip, or onto interior surfaces of the add-on component, the tape strips having a release liner on an opposite exposed side thereof. An extension tail is configured with the release liner that extends beyond the span-wise end of the add-on component when the add-on component is placed and held at a desired position on the blade. The add-on component is slid onto and maintained in position on the blade tip and, starting from the tape strip furthest from the separated trailing edge, extension tails of the respective tape strips are sequentially peeled through the separated trailing edge and away from the add-on component.

Disclosed is a hollow structure, particularly propeller blade, having excellent productivity, high strength, light weight, and high quality. The hollow structure is made of a resin, and includes: an outer surface; a retaining section; and a space in the structure; wherein at least one of the retaining sections is configured to support the outer surface at multiple points.