Drift angle

Also written as: wind correction angle, crab angle.

The aircraft flies through the air; the air moves over the ground. Point at 090 with a wind from the south and you will travel somewhere north of that line over the ground. The angle between the heading you are holding and the track you are making good is the drift angle, and correcting for it means turning into wind by roughly that amount so the track comes back to what you wanted.

Because the correction is applied to heading and the result is read as track, an instrument that shows both at once makes the whole problem visible. On an HSI with the course set, a centred needle held with a heading that differs from the course tells you the drift you are carrying, without any mental arithmetic.

Where this comes up

• Wind-correcting a heading on the HSI
• Wind correction in the hold