How to Calculate the Crosswind Wind Gust Speed

Written by marty simmons
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How to Calculate the Crosswind Wind Gust Speed
Crosswind gusts can make or break take-offs and landings. (plane image by martini from Fotolia.com)

The crosswind speed is vital for pilots during take-off and landing. Strong crosswinds can make landing dangerous, if not impossible, and every pilot considers them when deciding what runway to use. But the crosswind speed must be calculated based on the angle between the measured wind direction and the runway direction. In addition, wind measurements include a value known as the gust factor. The gust factor is the maximum measured wind speed, while the normal value is the average or sustained speed. While the average speed may allow for a safe landing, violent gusts could upset your plane.

Skill level:
Moderate

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Things you need

  • Calculator with trigonometric functions

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Instructions

  1. 1

    Determine the wind speed at the airport where you are going to land or take off. Wind speed measurements include the sustained speed and the gust factor. You need the gust factor. Wind speed is recorded in knots for pilots. If you are in the air, you can radio the tower at the airport or the local airport services for weather information. Otherwise, weather reports are available online or over the phone through the National Weather Service. Sometimes wind speed will be reported using the Beaufort Wind Scale, and you can approximate the speed using conversion charts from the National Weather Service.

  2. 2

    Calculate the angle between the wind direction and the direction of the runway. Runways are numbered based on their compass orientation. For example, Runway 10/19 runs roughly north to south from 10 degrees to 190 degrees. Since runways can be used in either direction, the angle changes based on which direction you will be facing. A take-off from runway 19 with wind coming from the southeast at 145 degrees would create an angle of 190 minus 45 or 45 degrees.

  3. 3

    Multiply the wind speed gust factor by the sine of the angle between the direction you are going and the wind direction. The result is the crosswind gust factor.

Tips and warnings

  • Calculations for the crosswind gust factor and crosswind speed are the same. However, they will have different meanings since a normal crosswind is sustained while the gust is a maximum possible value. You can make calculations quickly by using online calculators or crosswind charts.

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