An iconic feature found at many airfields since the earliest days of aviation, the humble windsock is without a doubt one of the most helpful tools available to pilots. It’s hard to imagine a simpler weather instrument, typically consisting of a brightly-colored fabric cone rotating about a pole. Yet it readily displays crucial wind information including direction, shifts, speed, and gusts. A smooth and safe takeoff or landing often hinges on how well this little piece of fabric does its job.
Windsocks, also referred to as wind cones, fall under the Federal Aviation Administration (FAA) design standards outlined in Advisory Circular150/5345-27 FAA Specification for Wind Cone Assemblies. While they are often sold in many different styles, the two sizes officially defined by the FAA are 8 feet and 12 feet long models. They can be constructed of cotton, synthetic, or a blend, must be water repellent, and come in colors of orange, yellow, or white. A windsock must be durable enough to withstand winds up to 75 knots and temperatures ranging from negative 67 degrees Fahrenheit up to 131 degrees Fahrenheit. It is important to note that windsocks are required to drain properly, freely move in just a three knot wind, fully extend in a 15 knot wind, and accurately indicate wind direction within plus or minus five degrees. They may also be illuminated for nighttime operations, using internal fixtures or downward-facing spotlights.
Airports should make a habit of frequently inspecting their windsocks. The fabric gradually fades over time and may become poorly visible, wear through, or tatter. They can snag and twist around mountings or vegetation. Poles can become tilted or bent, and lights will inevitably burn out. Proper drainage is essential, as storms can quickly fill windsocks with water, snow, or ice. This produces a telltale bulge in the fabric surrounding the frame and can add more than 10 pounds of weight to the windsock, reducing its accuracy or potentially even stopping its rotation. To prevent this, some windsocks are fabricated with built-in drain slits or grommets, and airport staff can easily install grommets onto non-equipped models. Care should be taken when installing a windsock to ensure the proper orientation of any drain slits or grommets, otherwise the drains will be rendered all but useless, as seen in this photo.
The North Dakota Aeronautics Commission (NDAC) administers a state Windsock Program to help airports keep their windsocks in tip-top shape. Each public-use airport in North Dakota may request one free windsock from the NDAC in each calendar year. We also offer windsocks for sale, in sizes of 12 feet, 8 feet, 5 feet, and 4 feet, as well as a small selection of windsock frames. For more information, please visit our website at https://aero.nd.gov or call (701)328-9650.
Adam Dillin, Airport Planner
North Dakota Aeronautics Commission
701-328-9650 | adillin@nd.gov
