The angle of attack is the angle between the chord line of aircraft’s wing and direction of the relative wind. In another terms, It is a fundamental aerodynamic concept that refers to the angle between the oncoming airflow and a reference line on an object, typically an aircraft wing. It is an important parameter that affects the lift and drag characteristics of the aircraft.
Let’s not forget that the angle of attack is different from angle of incident which is the angle between the chord line of aircraft’s wing and aircraft’s longitudinal axis.
To understand the angle of attack, let’s consider an aircraft in flight. The oncoming air exerts a force on the wing, generating lift, which opposes the force of gravity and keeps the aircraft airborne. The angle of attack is the angle at which the wing meets the oncoming airflow.
The reference line for measuring the angle of attack is usually the chord line of the wing. The chord line is a straight line drawn between the leading edge and the trailing edge of the wing. The angle between the chord line and the oncoming airflow is the angle of attack.
On each part of an airfoil or wing surface, a small force is present. This force is of a different magnitude and direction from any forces acting on other areas forward or rearward from this point. It is possible to add all of these small forces mathematically. That sum is the resultant force or lift. This resultant force has magnitude, direction, and location, and is as a vector.
The point of intersection of the resultant forceline with the chord line of the airfoil is called the center of pressure (CP).
So when The CP moves along the airfoil chord as the AOA changes. Throughout most of the flight range, the CP moves forward with increasing AOA and rearward as theAOA decreases.
The aircraft’s attitude changes according to AOA. When The AOA is decreasing, lift forces decreases as well.
When the AOA increases to the angle of maximum lift, the eburble point is reached. This is known as the critical angle.
When the critical angle is reached, the air ceases to filow smoothly over the top surface of the airfoil and begins toburble or eddy. This means that air breaks away from the upper camber line of the wing. What was formerly the area of decreased pressure is now filled by this burbling air. When this occurs, the amount of lift drops and drag becomes excessive. The force of gravity exerts itself, and the nose of aircraft. Durble point the aircraft drops. This is a stall. Thus, the burble point is the stalling angle.
The angle of attack is a critical parameter for pilots as it directly affects the performance and controllability of an aircraft.
During takeoff and landing, pilots carefully manage the angle of attack to ensure sufficient lift for a safe ascent or descent. In normal flight, pilots adjust the angle of attack to control the aircraft’s speed, climb or descent rate, and maneuverability.
In addition to aircraft, the concept of angle of attack is also applicable to other aerodynamic bodies, such as propellers. Understanding the angle of attack is crucial for efficient and safe operation in various fields of engineering and transportation.
