A wind cone is a device that provides a visual indication of wind direction and relative wind speed. These devices are installed at airports to provide pilots with information about conditions on the ground so that they can exercise appropriate precautions when landing. In addition, wind cones can be placed along high wind areas of a freeway to warn drivers when winds are high, and they can be used at facilities like chemical plants and refineries where wind direction and speed may be important to know about.
The wind cone consists of a tube of lightweight fabric mounted on a pole. The tube is able to swivel freely all the way around the pole so that it can move as the wind changes direction. A light breeze will lift the tube and partially fill it with air, causing it to project from the pole while the end of the tube hangs down. As the wind picks up, the part of the tube that droops down will gradually fill up, extending more and more of the tube. In high winds, the entire wind cone will be fully extended at a 90 degree angle from the pole.
Also known as a windsock, a wind cone is usually bright so that it will be highly visible. A lighted wind cone can be used at night in airports where pilots make night landings. Several wind cones will be scattered around a facility so that people can readily gather information about wind direction and wind speed when they are coming in for a landing.
Reading a wind cone is relatively easy. The wind is coming from the opposite direction that the wind cone is pointing in. For example, if a wind cone is pointing due East, it means that the wind is coming from the West. If the wind cone is partially extended, it means that air speed is relatively low. The more extended the cone, the higher the wind. Many cones are marked with rings so that people can clearly see how much of the cone is extended at any given time.
Wind cones manufactured to Federal Aviation Administration (FAA) standards are fully extended in winds that exceed 17 miles per hour (28 kilometers per hour or 15 knots). Some people use an anemometer, a device that measures wind speed, to take measurements when wind cones are at various stages of extension in order to learn which speed each stage corresponds to.