Angle of attack

Angle of Attack is the difference between the direction a wing is traveling and the direction the wing is pointing. Unlike pitch it changes during flight.

The lift generated by a wing is roughly proportional to the angle of attack, up to about 15 degrees when the wing stalls. Lift is also proportional to speed (squared) so a given aircraft will be flying at a low angle of attack when it is going quickly, and a high angle of attack when it is flying slowly. If the same aircraft is in a turn or some other manover at more than 1g, it generates the extra lift by increasing angle of attack.

It is generally represented in equations by the greek character alpha, thus flying at a large angle of attack is often referred to as 'high alpha'.

Angle of attack also applies to helicopter and propeller blades.