No doubt that you’ve seen windsocks before. But it would surprise you how little is known about what it actually is and what it’s used for.
We’re happy to explain that to you! At the end of this article, you will know everything about windsocks and their use worldwide.
What is a windsock?
A windsock, as we know it today, is a conically shaped tube made of woven textile which is used to measure both wind direction and speed.
A windsock, or wind cone, is a conical textile tube that resembles a giant sock. Windsocks can be used as a basic guide to wind direction and speed.
At many airports, windsocks are lit at night, either by floodlights on top surrounding it or with one mounted on the pole shining inside it.
Wind direction is the opposite of the direction in which the windsock is pointing, so a windsock pointing due north indicates a southerly wind. Wind speed is indicated by the windsock’s angle relative to the mounting pole; in low winds, the windsock droops; in high winds, it flies horizontally.
Alternating stripes of high visibility orange and white were initially used to help to estimate the speed of the wind. Each stripe adds up to 3 knots to the estimated wind speed.
However, some circle frames mountings cause windsocks to be held open at one end, indicating a velocity of 3 knots, even though anemometers would show no wind speed. A fully extended windsock suggests a wind speed of 15 knots (28 km/h; 17 mph) or greater.
ICAO (Annex 14)/UK CAA
- Size: 3.60 m (12 ft) in length and 0.9 m (36 inches) throat diameter at the large end.
- Height: At a 6.0 m (20 ft) mast height, the taper of the fabric windsock from the throat to the trailing end must be designed to cause the windsock to fully extend when exposed to a wind of 15 knots (28 km/hr or 17 mph.)
“Wind direction indicators, including supplemental indicators, must be lighted if the airport is open for air carrier operations at night.”
Windsocks must rotate freely around a vertical shaft, must indicate true wind direction +/- 5 degrees, and indicate 15 knots of wind when fully extended. Windsocks must be white, yellow, or orange to contrast with the surroundings.
- Size 1: 2.5 m (8 ft) in length and 0.45 m (18 inches) throat diameter at the large end.
- Size 2: 3.60 m (12 ft) in length and 0.9 m (36 inches) throat diameter at the large end.
- FAA type L-806 support – those mounted on low mass supporting structures – maximum of 3.0 m (10 ft) mast height
- FAA type L-807 support – those mounted on rigid supporting structures – Maximum of 4.8 m (16 ft) height to windsock.
How is a windsock mounted?
They are mounted on a special installation. These usually consist of a metal mast made of aluminum or galvanized steel. The mast is placed on a metal foundation so that it can withstand high wind speeds.
A metal basket (or so-called swivel frame) is placed on top of the mast, which can rotate 180 degrees horizontally. The windsock is attached to this so that it can move freely depending on where the wind comes from.
Depending on the application, installation can be simple or expanded. For example, lighting can be placed on the installation if it’s supposed to be visible at night. The mast can also be made tiltable so that the bag can be replaced more easily.
What’s the purpose of a windsock?
Windsocks are used in various industries. The goal is to give staff or other attendees a quick indication of where the wind is coming from and how hard the wind is blowing. The most commonly used location is next to the runway or helipad is at an airport. This allows pilots to quickly estimate the wind direction and speed before take-off.
But they’re also used in factories or industrial areas where hazardous gases or substances can be released. In the event of an emergency, attendees can quickly estimate which way the hazardous substances are being blown, in order to determine the best possible escape route.
What does the color of a windsock mean?
The red/white stripe is the most famous version that you’ll often see alongside the road. Yet many different colors are used internationally, such as orange (striped), green, blue, and completely orange.
In general, the colors are chosen in such a way that the entire installation is clearly visible in contrast with the background. Almost no blue windbags are used in the maritime world. But at airports where there’s a lot of grass around the runway, green windsocks will hardly ever be used.
But a green windsock is very useful near a nature reserve where a red/white windsock is not always allowed. Near places like that, a green windsock is a perfect solution.
Are windsocks calibrated?
Brand new windsocks are produced according to the guidelines of the ICAO. This means that all current models are calibrated to be fully inflated at wind speeds of 15 knots or more.
What are the windsock speed charts?
The stripes on a windsock are not only chosen to be visible from a great distance. If a stripe is “blown up” by the wind, you can use it to read the current wind speed.
- 3 knots
- 6 knots
- 9 knots
- 12 knots
- 15 knots or more