What is the primary consequence of icing on an airfoil?

Icing on an airfoil primarily leads to an increased stall speed. When ice forms on the wings or other surfaces of an aircraft, it alters the shape and smoothness of the airfoil, which is critical for maintaining proper airflow and lift generation. The presence of ice disrupts the airflow over the wing, resulting in a higher angle of attack being necessary to achieve the same amount of lift. This increased angle of attack can push the aircraft closer to its stall angle, causing the stall speed to rise, which is the minimum speed at which the aircraft can maintain controlled flight.

In contrast, improved lift is not a consequence of icing; rather, the altered airflow typically leads to a decrease in lift efficiency. Decreased drag is also incorrect because ice contributes to greater drag due to the rough surface it creates. Lastly, icing does not shorten flight time; in fact, it can complicate flight operations, potentially leading to longer and more difficult flights as pilots manage the issues caused by ice accumulation.