Which condition causes the most severe wake turbulence while landing?

The condition that causes the most severe wake turbulence while landing is characterized as heavy, slow, and clean. This combination is significant due to several factors.

When an aircraft is heavy, it generates more lift and, consequently, more wake turbulence as it passes through the air. Heavy aircraft displace a larger volume of air, creating stronger vortices behind them. The "slow" aspect indicates that the aircraft is flying at lower speeds, which increases the intensity and duration of the wake turbulence. This is particularly important because vortices tend to settle towards the ground and stay there longer when the aircraft is operating at slower speeds, such as during landing.

Additionally, being "clean" means the flaps and slats are retracted, leading to a more streamlined configuration that enhances the generation of more pronounced vortices. In contrast, when an aircraft is dirty (with flaps extended), the turbulent flow caused by the lift devices can somewhat mitigate the strength of the wake turbulence as it creates more disruptive airflow.

These combined factors make the heavy, slow, clean condition the most critical for wake turbulence, resulting in a potentially hazardous environment for following aircraft during the landing phase. Understanding these dynamics is essential for pilots to ensure safe separation between aircraft in landing patterns.