Abstract: An anemometer for measuring the component of air or of a similar fluid speed along its axis of rotation, in which the anemometer has a plurality of generally radially directed, helicoidal airfoils. The airfoil effect is produced by the helicoidal twisting which results in a vacuum being produced on one side thereof according to the direction of rotation. Each of the airfoils has a plurality of helicoidal edges, each edge being formed by the intersections of two or more plane surfaces so as to form airfoils having parallelogram or substantially parallelogram cross-sections. Each airfoil extends outwardly from a rotatable hub and is attached to the hub at its inner end but is spaced in part from the hub by a cutout area, such as a slot across the airfoil.

Abstract: This invention relates to an improved helicoidal-bladed, cosine anemometer which is capable of accurately sensing very small elements of fluid flow at any angle of attack in hostile environments where extremes of temperature, dust, and moisture are encountered. This invention relies on principles of miniaturization which permit accurate measurement with a minimum of supporting equipment and which also permits thermal protection of the device in situations where temperature extremes are encountered. A notched lower end of the blade together with a plurality of parallel ridges around the circumference of the hub form a channel for deflecting air along the blade for the purpose of controlling the anemometer blade, tip, and edge vortices to eliminate dynamic pressures on adjacent blades which frequently occur in conventional bladed anemometers when the angle of fluid attack is large.