Windsock facts for kids
Windsock in Freiburg im Breisgau, Germany
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| Classification | Meteorological instrument |
|---|---|
| Uses | Indicates wind direction and estimates its speed. |
| Related | Anemometer, weather vane, anemoscope |
A windsock is a giant, lightweight cloth tube shaped like an open cone. It is often called a wind cone or wind sleeve. When it hangs from a tall pole, air catches inside it. It helps people quickly see which way the wind is blowing and estimate wind speed. You will often see them at airports, airfields, and next to open, windy highways.
Wind flows right into the wide opening of the cloth and exits through the narrow tail. Because of this, the narrow tail always points away from the blowing breeze. This means the actual wind direction is the exact opposite of where the tail points. If a windsock points directly north, the wind is blowing from the south. The angle of the cloth also shows how powerful the breeze is. When there is almost no breeze, the tube droops downward. When strong gusts blow, the tube fills up and stretches straight out horizontally.
How Does a Windsock Work to Measure Wind Speed?
Many windsocks have bright alternating stripes of orange and white fabric. These bright stripes make them very easy for pilots to see from high above. Each stripe that puffs open adds an estimated 3 knots (about 3.5 miles per hour) of speed. When the entire tube is completely filled with air and flies straight, the wind is blowing at 15 knots or even faster. At night, airports often shine bright lights onto the sock so pilots can land safely in the dark.
Official safety agencies have special rules for how windsocks must be built. The United States FAA requires that a proper windsock must turn smoothly in a gentle breeze of only 3 knots. It must also fly completely straight and level in a stronger breeze of 15 knots.
In Canada, Transport Canada uses angles to tell pilots how fast the wind is moving. A 6-knot breeze lifts the windsock 30 degrees below horizontal. A 10-knot wind lifts it to 5 degrees below horizontal. Finally, a 15-knot breeze pulls it completely level. Global flight safety rules set by the ICAO state that large windsocks must measure at least 3.6 meters long. They must also be visible to pilots from an altitude of 300 meters in the sky.
Other Airport Wind Indicators
Airports sometimes use other tools to help airplane pilots read the breeze. A wind tee is a device shaped like a small airplane. It turns freely on a pivot so its nose points directly into the wind, showing the best direction to take off. A wind tetrahedron is a three-sided pyramid on a swivel with a tip pointing into the breeze. While these tools show pilots direction, they do not show wind speed like a windsock does.
See also
In Spanish: Manga de viento para niños
- Anemoscope – an instrument for showing wind direction
- Anemometer – a tool used to measure wind speed
- Draco (military standard) – an ancient military standard shaped like a windsock
- Koinobori – traditional Japanese decorative windsocks shaped like carp fish
- Traffic pattern indicator – airport markings that help guide landing airplanes
