Crosswind & Headwind Component
Crosswind and headwind or tailwind on a runway from the reported wind and gusts, true-to-magnetic done for you, and your own crosswind limit compared.
How much of the wind is across the runway and how much along it, in the steady wind and in the gust, which side it comes from, whether it exceeds the limit you enter, and the rule-of-thumb table beside it.
Example: Runway 27, wind 300° true at 15 gusting 25 with 10° E variation: 20° off the runway, crosswind 5.1 kt (8.6 in the gust) from the right, headwind 14.1 — within a 15 kt demonstrated crosswind.
Sine across,
cosine along.
How the wind is resolved onto the runway, why the variation step matters, what gusts do, and what the demonstrated crosswind figure is and is not.
Resolving the wind
The angle between the wind direction and the runway heading is all that matters: crosswind = wind speed × sin θ and headwind = wind speed × cos θ, negative for a tailwind. At 30° off the runway half the wind is crosswind, at 45° seven tenths, at 60° nine tenths, and at 90° all of it — the rule-of-thumb table the page shows beside the exact figure. The side the crosswind comes from follows from which way round the wind lies.
True and magnetic
A METAR, a TAF and a winds-aloft forecast give the wind in degrees true; the runway number and the wind a tower or ATIS reads to you are magnetic. Ten degrees of variation is ten degrees of wind angle — enough to move the crosswind component by a knot or two at 15 kt — so the page applies the variation you enter to a true wind before resolving it. Choose “magnetic” for a tower wind and the step is skipped.
Gusts and the limit
A gust is resolved the same way, and it is the gust component that meets the limit first. The maximum demonstrated crosswind in a handbook is the strongest crosswind a test pilot showed the aircraft could handle at certification; it is not a legal limit, and it says nothing about your own. The page only compares the components with the figure you enter.
What the number does not settle
A wet, icy or contaminated runway, a gust that arrives during the flare, wind shear and the aircraft’s own handling are not in the arithmetic. A planning aid, not a substitute for the pilot’s operating handbook, the aircraft’s limitations or the rules that apply to the flight. Inputs stay in your browser; the same anonymous usage counts as the rest of the site apply.