NIFE Aerodynamics Practice Exam

An increase in angle of attack (AOA) beyond a certain critical point on a positively cambered airfoil results in both an increase in drag and a loss of lift. As the AOA increases, the airflow can become disrupted, particularly if the angle exceeds the critical AOA. This disruption leads to a phenomenon known as stall.

During the stall, the airflow separates from the upper surface of the airfoil, which significantly reduces the lift generated by the wing. Instead of the smooth flow of air over the wing that creates lift, the separation creates turbulence and a vortex, reducing pressure on the upper surface and thus diminishing the lift force. At the same time, because the airflow is not smooth and is disrupted, drag increases due to the turbulent wake created behind the airfoil.

At lower angles of attack, lift is generally more efficient and drag is lower, but exceeding the critical AOA introduces these conflicting aerodynamic characteristics. Thus, when the angle of attack grows too high, the combined effects of increased drag and reduced lift occur, making it clear that both phenomena happen when the critical angle is surpassed.