Precise, reliable measurement and display of Angle of Attack (AOA) from takeoff to landing can substantially improve aircraft performance as well as assure a safe operating margin above stall speed.
Angle of attack is defined as the angle formed between the wing chordline and the direction of air flowing past the wing. At any specific AOA, the airflow over some percentage of the wing surface will generate lift as well as some amount of drag. Maximum lift is usually obtained at a relatively high angle.
Stall is defined as the condition which arises when the angle grows so large that the flow is completely disrupted and not enough lift is generated to overcome the weight of the aircraft. This AOA, the stall angle, is constant for a particular aircraft, although various wing designs stall at differing angles.
The amount of useful lift and drag generated by any wing at some specific AOA will depend upon the influence of such variables as the wing geometry, density altitude, aircraft gross weight and velocity. However, the ratio of lift to drag coefficients at a given angle remains constant. Therefore, the theoretically ideal ratio of lift and drag coefficients for any flight maneuver will always be found at the same AOA under all speeds or load conditions.