Runway wind component calculator
A wind that is 20 knots straight down the runway and a wind that is 20 knots across it are completely different propositions. This splits any reported wind into the part along the runway and the part across it.
Calculator
This is an educational and planning aid. Use current official weather, your aircraft flight manual, and the rules that apply to your flight before you act on any figure here. See the aviation disclaimer.
What the result means
The crosswind component is the part of the wind trying to push you sideways off the centreline. It is what you compare against your own demonstrated crosswind figure and your own currency.
The along track component is a headwind when positive and a tailwind when negative. A headwind shortens the takeoff and landing roll. A tailwind lengthens both, and it does so faster than most pilots expect.
If a gust is entered, the calculator resolves it as well, because the gust is the figure that matters for handling on the runway.
When this is useful
- Before every takeoff and landing where the wind is not close to straight down the runway.
- Choosing between two runways at an airfield when neither is aligned with the wind.
- Comparing a forecast wind against an aircraft limit during flight planning, well before you get near the airfield.
How it is calculated
The angle between the runway and the wind is taken, then the wind speed is split into two parts with basic trigonometry. The crosswind is the wind speed multiplied by the sine of that angle, and the along track component is the wind speed multiplied by the cosine.
References are handled explicitly. A runway designator is magnetic, and so is a wind passed by the tower or read from an ATIS. A wind in a METAR or a TAF is true. If the two references you select differ, the calculator asks for magnetic variation and converts before comparing, which removes the commonest source of error in this calculation.
crosswind = wind speed x sin(angle), headwind = wind speed x cos(angle)
Worked example
- Runway heading
- 090 magnetic
- Wind direction
- 120 magnetic
- Wind speed
- 20 kt
The wind is 30 degrees off the runway, giving a 10 kt crosswind from the right and a 17.3 kt headwind.
Check: At 30 degrees the sine is exactly 0.5, so the crosswind must be exactly half the wind speed. Half of 20 is 10, which the calculator returns. The 30, 45, 60 degree rule of thumb gives a half, two thirds and nearly all of the wind speed as crosswind, and this matches the first of those.
Limitations
- Reported wind is measured at one point on the airfield, usually at 10 metres, and averaged over a period. The wind at 50 ft on short final can differ considerably.
- Terrain, buildings and trees near the runway produce local effects that no component calculation can describe.
- The result is a component, not a limit. Whether it is acceptable depends on your aircraft, the surface, and your own recent experience.
Common mistakes
- Comparing a METAR wind directly against a runway designator without converting. One is true and the other is magnetic, and in some parts of the world that difference is well over 10 degrees.
- Using the steady wind and ignoring the gust. Handling on the runway is set by the gust, not the average.
- Forgetting that a tailwind component of even a few knots can add a surprising amount to the landing distance.
Sources
- Airplane Flying Handbook (FAA-H-8083-3), crosswind approach and landing , US Federal Aviation Administration
- Crosswind Landing , SKYbrary, EUROCONTROL
- Aviation Weather Handbook (FAA-H-8083-28) , US Federal Aviation Administration