Windsock - An aviation instrument for wind speed & direction

What is a windsock?

What we call a "windsock" is actually a fabric tube, either conical or cylindrical, with one open and one closed end, fixed on a pole in an open area. It is mostly found in places like airports and workplaces and indicates wind direction and speed. Depending upon the strength of the wind, the windsock changes its form and size. It is inflated and extended in stronger winds and deflated and relaxed in weaker winds. 

History of windsock

Windsocks have been used since at least the times of ancient China and Japan; however, their inventors are unknown. In Japan, flying paper and silk-made windsocks were a traditional way to celebrate the arrival of a new baby, particularly a son. The Romans used windsocks as battle flags. Some have speculated that the windsock was inspired by the windsail, which was used to direct air into a ship's cabin. Today, windsocks are available in many different types for a wide range of sectors.

The first contemporary fabric windsocks were designed for airports in the early 20th century. For pilots, knowing the direction and speed of the wind is crucial during takeoff and landing; hence these devices are installed and are now commonly seen at airports across the world. Also, if there is a fire, a chemical spill, or a toxic gas leak, it is crucial to evacuate in the opposite direction of the wind. So, windsocks are also found at hazardous workplaces to find out the wind direction during an emergency evacuation.

Different types of windsocks

There are several types of windsocks that are used for different purposes. They can be made of different materials like Nylon, Vinyl, Canvas, Polyester, etc. Some common types of windsocks include:

Airport windsocks: The most common type of windsocks is what we see at airports. They are typically made of durable, weatherproof fabric and mounted high on a pole. Their purpose is to provide pilots with information about wind direction and speed. 

Industrial windsocks: This type can be seen at many hazardous workplaces like oil & gas, manufacturing, and processing facilities. Their purpose is the same; however, they are mounted on a relatively shorter pole.

Emergency response windsocks: These windsocks are used by emergency responders, such as firefighters, to indicate wind direction and speed during an emergency situation. They are typically made of bright, reflective fabric and are mounted on a portable, lightweight pole.

Agriculture windsocks: These windsocks are specifically for use in agricultural spraying. These windsocks are installed on agricultural crop sprayers to prevent off-target spray drift of pesticides.

Personal windsocks: These wind socks are compact and lightweight, perfect for taking with you anywhere. Sailors, hikers, and others who spend time in outdoors often use them to assess wind direction and speed. In most cases, they are fixed on a short, collapsible pole and made from a lightweight, packable cloth.

Decorative windsocks: These windsocks are mostly used for aesthetic purposes, such as in gardens and on porches. They are usually made of vibrant, patterned fabrics and mounted on a shorter pole.

Windsock Colors

The color of a windsock does not convey any specific information about wind direction or speed. However, the color may vary depending on the intended use and region. Some windsocks may be painted with unique colors or patterns for the identification or decorative purposes.

Typically, airport windsocks are orange or international orange, a bright, highly visible color that is seen in a variety of lighting conditions. There can be white stripes on the windsocks. Industrial windsocks are often white, red, or a combination of these colors. As a means of increasing their visibility in emergency situations, emergency response windsocks are frequently red, yellow, or orange. Personal and decorative windsocks can be any color, and people usually choose them based on how they look.

Installation method of a windsock

To mount a windsock, you will need a windsock, a mounting pole, and any necessary hardware. Here are the steps for mounting a windsock:

1. Choose a location for the windsock: Pick a spot for the windsock, making sure it will be exposed to wind from all directions. The height should be appropriate for the purpose of the windsock.
2. Install the mounting pole: The mounting pole should be anchored in a stable base, such as a concrete pad or a sturdy fence post. The pole should be tall enough to allow the windsock to hang at the appropriate height when it is fully extended.
3. Attach the windsock to the mounting pole: Most windsocks have a ring or loop at the closed end that can be attached to the mounting pole using a snap swivel or a carabiner. The windsock should be attached so that it can rotate freely on the mounting pole.
4. Test the windsock: Once the windsock is installed, you should test it to make sure it is working properly. Blow on the windsock or wait for the wind to fill it, and observe the direction that the windsock points. If the windsock is not pointing in the direction that you expect, you may need to adjust the mounting pole or the attachment point of the windsock.

How to read a windsock?

To read a windsock, you need to observe its shape and the direction that it is pointing.

Shape: The shape of the windsock can provide information about the strength of the wind. When the wind is strong, the windsock will be fully inflated and extended. When the wind is weaker, the windsock will be less inflated and more relaxed.

Direction: The direction in which the windsock is pointing indicates the direction of the wind. The open end of the windsock will always point in the direction that the wind is coming from.

Windsock speed chart

The stripes of a windsock are not designed just for their ability to be seen from a long distance. If a stripe has been inflated by the wind, it can be used to determine the current windspeed. Each inflated stripe adds three knots of wind speed.

1 stripe = 3 knots (3.5 mph / 5.6 km/h);

2 stripes = 6 knots (7 mph / 11.1 km/h);

3 stripes = 9 knots (10.4 mph / 16.7 km/h);

4 stripes = 12 knots ( 13.9 mph / 22.2 km/h);

5 stripes = 15 knots + (over 17.3 mph / 27.8 km/h);

Windsock speed chart

Windsocks accuracy in measuring wind speed

It is essential to remember that the windsock is not a precise tool and should not be used to precisely measure wind speed.  Instead, it is intended to provide a general indication of wind direction and strength. The shape and size of the windsock can provide some information about the wind speed, but it is not a precise measurement.

When the wind is strong, the windsock will be fully inflated and extended. When the wind is weaker, the windsock will be less inflated and more relaxed. However, the exact wind speed cannot be determined from the shape and size of the windsock alone. Factors such as the size and shape of the windsock, the material it is made of, and the wind conditions in the surrounding area can all affect the way the windsock appears.

To accurately measure wind speed, you will need a wind speed gauge or anemometer. Anemometers are instruments built exclusively to measure wind speed, and they are often more accurate and precise than windsocks. Cup anemometers, vane anemometers, and ultrasonic anemometers are among the several types of anemometers. These instruments measure wind speed using various techniques, such as measuring the rotation of a cup or vane in the wind or the time it takes a sound wave to travel through the wind.

Windsocks Standards & Regulations

There are various standards and regulations that apply to windsocks, depending on the location and purpose of the windsock. Some common standards and regulations that may apply to windsocks include:

Airport standards: At airports, windsocks are typically required to meet certain standards to ensure that they are visible and accurate. The International Civil Aviation Organization (ICAO) has published standards for airport windsocks that specify the minimum size, color, and mounting requirements for airport windsocks. These standards are intended to ensure that the windsocks are easily visible to pilots and provide accurate wind information.

Industrial standards: Industrial windsocks may be subject to standards and regulations that are specific to the industry in which they are used. For example, chemical plants and refineries may have specific requirements for the materials and construction of the windsock to ensure that it is safe and durable.

Building codes: In some cases, windsocks may be subject to building codes and other regulations that apply to structures and facilities. For example, the windsock may need to meet certain requirements for wind resistance, fire safety, and other issues.

Some examples of windsock standards and regulations are:

International Civil Aviation Organization 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.)

Rotation: 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.

Federal Aviation Administration US (FAA)

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.

Height:

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.

Rotation:

AC 150/5345-27E states that a properly-functioning windsock will orient itself to a breeze of at least 3 knots (5.6 km/h; 3.5 mph) and will be fully extended by a wind of 15 knots (28 km/h; 17 mph). In addition, wind cone assemblies must be designed to operate in wind speeds of up to 75 knots (140 km/hr or 86 mph) and ambient temperatures between -67° F (-55° C) and 131° F (+55° C.)

Transport Canada

TC AIM-AGA-Aerodromes-5.9 "Wind Direction Indicators", requires that a 15-knot (28 km/h; 17 mph) wind will fully extend the windsock, a 10-knot (19 km/h; 12 mph) wind will cause the windsock to be 5° below the horizontal, a 6-knot (11 km/h; 6.9 mph) wind will cause the windsock to be 30° below the horizontal.

It's important to note that the standards and regulations for windsocks may vary depending on the location and purpose of the windsock. It is important to follow any applicable standards and regulations to ensure the safety and effectiveness of the windsock.