PREFLIGHT» HOW IT WORKS BY ALTON K. MARSH The windsock Measuring the wind WINDSOCKS ARE CRITICAL even if the airport has a tower with a controller updating you on the wind speed and direction. Most likely the controller's information on speed and direction is measured at the center of the airport. But what if it is a crazy day with windsocks pointing in all directions? Knowing how to read a windsock directly affects the crosswind corrections you will make. There are many airports where swirling winds can result in unusual conditions, such as two windsocks at opposite ends of the runway pointing at one another. What matters to you is the windsock nearest your point of liftoff or landing. Windsocks are critical during taxi as well, to limit the effect of the wind through proper positioning of the aileron and elevator controls. Windsocks are calibrated to give a certain amount of hang or bend until the wind reaches a specific speed, at which point the sock is blowing arrow straight. The FAA-which refers to the sock as a wind cone-says the wind sock will be fully extended at 15 knots (17 mph). The windsock will orient itself according to the direction of the wind. The bigger end faces the wind. WHEN THE WINDSOCK changes from being droopy to straight and back again, the wind is gusting, and the degree of slack between straight and droopy indicates the relative size of the gusts. Gusts that come and go violently will have a much more dramatic effect on the airplane. Standard windsocks are usually eight feet or 12 feet long. Both must lift to the horizontal position, parallel to the ground, at 15 knots. A windsock drooping along a 45-degree angle is indicating seven to eight knots. Windsocks must be able to pivot around a pole to indicate direction when winds are three knots or more. Many are lit at night. 14 / FLIGHTTRAINING.AOPA.ORG STEVE KARP SOCK IT TO MEhttp://FLIGHTTRAINING.AOPA.ORG