Drift Angle

What is Drift Angle?

Drift angle is the angular difference between the direction an aircraft is pointed (heading) and the path it actually follows over the ground (track). This deviation is created by wind pushing the aircraft sideways, causing it to drift left (port) or right (starboard) of its intended path.

Causes and Symptoms of Drift Angle

Drift angle occurs whenever there is a crosswind component. If the wind blows from the left, the aircraft drifts right of its heading, and vice versa. The greater the crosswind relative to the aircraft's speed, the larger the drift angle. Symptoms of drift include the aircraft not staying on the planned track, requiring heading corrections.

Drift Angle Calculation

To calculate drift angle:

• Use the triangle of velocities, which relates heading, track, and wind.
• On a navigation computer, input true airspeed, wind speed and direction, and heading to find the drift angle and groundspeed.
• The maximum drift angle occurs when the wind is perpendicular to the track.

Drift Angle vs Wind Correction Angle (WCA)

The drift angle measures the deviation caused by wind, while the wind correction angle is the heading adjustment made to counteract drift and maintain the desired track. Numerically, they are equal but have opposite signs: if drift is left, the WCA is right, and vice versa.

Practical Application

Pilots regularly estimate or calculate drift angle during flight, especially after observing an off-course fix. The 1 in 60 rule helps: a 1 NM deviation after 60 NM flown equals a 1° drift angle. Correcting for drift ensures accurate navigation and timely arrival.