True Airspeed Calculator

Wolfgang Polak

To calculate the true airspeed of your aircraft, fly three legs at headings that differ by 90 degrees. For example, fly north, east, and then south, but any initial heading will do. Determine the ground speed on each of the legs using your GPS. Then plug all the data into the form below and find your true airspeed and actual wind speed. If you also provide the correct initial heading, you'll get the wind direction. Any speed unit will work, the output will be in the same unit as the input.

If you are curious why and how all of this works, you can find a detailed description of this technique in a tech note (requires Acrobat reader).

First leg	Speed	Heading
Second leg	Speed	Turns
Last leg	Speed

True airspeed:
Wind speed:
Wind direction: