Modern aircraft navigation relies less on the arithmetic of pilots and more on digital technology and the global positioning system, also known as GPS. Wind correction angle is found from a trigonometric function using the known values for wind direction, wind speed, true airspeed, desired course angle and the wind-to-track angle. Altitude is used to find the value of true airspeed, while the desired course angle and wind direction are given measurements. To calculate for the wind correction angle, you must first calculate for the values of true air speed and the wind-to-track angle.
- Skill level:
Things you need
- Speed indicator
- Scientific calculator
Record the indicated airspeed from your speed indicator and the altitude reading from your altimeter. Factor a 2 per cent increase of indicated airspeed for every thousand feet the altitude is above mean sea level. This value will give you the true airspeed. For example, a plane with an altitude of 6,000 feet and an indicated airspeed of 600 miles per hour would have a true airspeed of 618 miles per hour [600 + (6,000/1,000) + (.02 x 600)]. The equation should read as follows:
true air speed = indicated air speed + [(altitude/1000)+(0.02*indicated airspeed)]
Find the wind-to-track angle by subtracting wind direction from the desired course angle. The equation should read as follows:
wind to track angle = desired course angle - wind direction
Input your new values for the true airspeed and the wind-to-track angle into your scientific calculator to solve for the wind correction angle. Take a moment to find the sine function on your calculator for this next calculation. First solve for the value "sin(wind correction angle)" by inputting values for wind speed, wind to track angle and true airspeed into the following equation:
sin(wind correction angle) = wind speed * [sin(wind to track angle) / airspeed]
Solve for wind correction angle using the value "sin(wind correction angle)" and input the following equation into your calculator:
wind correction angle = arcsin(sin(wind correction angle))
Tips and warnings
- Run all calculations twice to double check your work. A graphing calculator is ideal for the type of trigonometry used for these equations.
- Make sure all instruments in the aircraft have been recently calibrated and are functioning properly before the aircraft takes flight.
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