Why does ice or snow on the wing increase stall speed?

The presence of ice or snow on the wing increases stall speed primarily because it disrupts smooth airflow over the wing and adds drag. When ice or snow accumulates on the wing, it alters the wing's aerodynamic shape, which is critical for generating adequate lift. The smooth flow of air is essential for maintaining lower pressure above the wing, which in turn produces lift according to Bernoulli's principle.

With ice or snow on the surface, the airflow becomes turbulent and separated. This disruption causes the wing to lose its lift at a higher angle of attack than it would under normal clean conditions. Consequently, the stall speed—the speed at which the aircraft can no longer maintain lift—increases, putting the aircraft at risk of a stall at lower airspeeds than anticipated.

This effect highlights the necessity for pilots to ensure that wings are clean and free of contaminants to maintain optimal performance, especially in winter conditions where ice and snow accumulation is common.