Wind is vector that can be broken down into its components. The crosswind component (w_{c}) — that is the contribution of the wind that is perpendicular to the lifting surface (aerofoil wing) — is a function of the mathematical Sine function. As the crosswind acts perpendicular to the lifing surface, the more orthogonal this is (i.e. the greater the angle) the less lift that is available to the wing. The headwind/tailwind component (w_{h}), acts towards the front of the wing (headwind) or from behind of the wing (tailwind) and is a function of the mathematical Cosine function.
Quick ruleofthumb
The crosswind component can be estimated by a general quick ruleofthumb:
If the wind is...
30° off runway heading, the crosswind component is 50%
45° off runway heading, the crosswind component is 75%
60° off runway heading, the crosswind component is 100%
Note: for simplicity, one can consider a crosswind 60 degrees or more off the runway heading has a near 100% crosswind component. In actual fact at 90° the crosswind component is 100% and at 60° it is closer to 90%, but this is a useful approximation.
