How Angle of Attack Affects Lift and Causes an Airplane Stall
Understanding the relationship between angle of attack and lift is essential in the study of basic aerodynamics. This principle explains how wings generate lift and why airflow separation can lead to an aerodynamic stall.
Lift and Angle of Attack
As an aircraft flies, air flows over its wings. When the angle of attack—the angle between the wing’s chord line and the relative wind—is increased, the wing typically generates more lift. This is because a higher angle of attack changes the way air moves over the curved surface of the wing, increasing pressure differential.
However, there is a limit. Lift is only generated when the airflow remains attached and conforms to the upper surface of the wing. As the angle of attack increases beyond a certain point, the airflow begins to separate from the wing’s surface.
Airflow Separation and Stall
When the angle of attack becomes too great, the airflow can no longer conform to the surface of the wing. Instead of flowing smoothly over the airfoil, the air separates, creating turbulent flow characterized by backfilling, burbling, and eddies.
This disruption in airflow results in a rapid decrease in lift. At this point, the wing is no longer producing sufficient lift to sustain flight, and the aircraft is said to have entered a stall.
The Critical Angle of Attack
It is important to note that an airplane stalls not at a specific airspeed, but at a specific critical angle of attack. This critical angle varies slightly between different wing designs but remains constant for a given airfoil regardless of aircraft weight, speed, or configuration.
Once the critical angle of attack is exceeded, lift decreases dramatically due to airflow separation, resulting in a stall. This principle is a cornerstone of stall awareness and prevention in both student pilot training and advanced flight operations.
Summary
Lift increases with angle of attack up to a point.
Airflow must conform to the wing surface to generate lift.
Airflow separation occurs when the angle of attack is too high.
An aerodynamic stall happens when lift is destroyed due to separation.
Stalls occur at a specific angle of attack, not a specific airspeed.
A solid understanding of angle of attack, lift, and stall behavior is crucial for safe and effective flight operations. Pilots must monitor angle of attack during various phases of flight to avoid unintentional stalls, especially during takeoff, approach, and landing.
