About This Site

What the Tool Computes

The tool applies two trigonometric identities to one reported wind: the crosswind component equals wind speed multiplied by the sine of the wind angle, and the along-runway component equals wind speed multiplied by the cosine of that same angle.

The wind angle is the difference between the reported wind direction and the runway heading, normalised to a value between −180° and +180°. The sign of that value carries the side information: a positive result places the crosswind on the right of the runway centreline, a negative result places it on the left. A cosine result below zero is reported as a tailwind rather than a negative headwind.

Wind speed is accepted in knots, kilometres per hour, metres per second and miles per hour. Every entry converts to knots once, before any component is computed, because the caution thresholds the tool marks against are defined in knots.

Accuracy and Its Limits

Every figure is exact to the trigonometry and rounded to one decimal knot, which makes the arithmetic tighter than any printed chart or mental estimate.

Accuracy in the air is governed by the input rather than the calculation. A reported surface wind is a two-minute average taken at one sensor, usually about ten metres above the ground, and the wind at the threshold differs from it. The tool models a steady wind and does not model mechanical turbulence, low-level wind shear or microbursts. Gust handling is limited to recomputing the same geometry at the gust speed.

Reference direction matters as much as speed. Runway numbers and tower-reported winds are magnetic, while METAR, TAF and winds aloft forecasts are referenced to true north. Comparing a true-referenced wind against a magnetic runway heading introduces an error equal to the local magnetic variation.

Sources and Corrections

Aircraft figures on this site come from published type manuals and manufacturer documentation, and demonstrated crosswind values are reproduced as information rather than as operating limits.

Regulatory framing follows 14 CFR Part 23 certification requirements and FAA Advisory Circular 91-79B. Nothing here replaces the aircraft flight manual or a current official weather report. Corrections to any figure can be sent through the contact page, and the full list of pages is on the site index.