Using Windsocks

Windsocks help make pilots aware of wind direction, gust factors and wind speed.   Some windsocks (like the one above) are calibrated.   Most airports use these because they meet specifications that make their behavior in wind more consistent.   Lighter weight fabric and windsocks without the framed structure at the sock opening are not exactly the same, but you can learn to gauge the wind speed with experience.

Calibrated windsocks are designed to fill with wind without any kinks when the wind is above 15 knots per hour.   A nautical mile is 1.15 miles.   Below are some conversions of knots  converted to miles per hour (MPH).

•   5 Knots   =   5.75 MPH
  
•   8 Knots   =     9.2 MPH
• 10 Knots   =   11.5 MPH
• 15 Knots   = 17.25 MPH

Although there is not that much difference between KNOTS and MPH, it is important to be aware of the difference.   A full windsock (no kinks) indicates not only 17 MPH, but perhaps any velocity above that.

Criteria for “calibrated” windsocks in MPH (numbers rounded slightly):

•   7    MPH      –  the windsock will be 30° below the horizontal
• 11.5 MPH     – the windsock will be 5° below the horizontal with a slight kink
• 17    MPH     – the windsock should be fully inflated, without kinks.  Any wind speed above this, the sock will be full and without kinks.

Below are some pictures of calibrated windsocks with estimated velocities noted: