Crosswind Component

When wind is not blowing directly across or directly along a runway, only part of its speed pushes the aircraft sideways. The crosswind component is the side-to-side part of the wind vector, and the sine function appears because we take the component opposite the angle between the wind direction and the runway. As the angle to the runway increases from 0° to 90°, the sideways effect grows from none to the full wind speed.

Use this formula when checking whether an aircraft can safely land or take off with a wind blowing at an angle to the runway. It is also useful for flight planning, runway selection, and estimating how much rudder or aileron correction may be needed.

• using cosine instead of sine for the sideways component
• forgetting that the angle must be measured relative to the runway, not the wind direction alone
• mixing up total wind speed with the crosswind component