What visual condition may cause a pilot to perceive a runway as higher than it is?

The phenomenon known as the upsloping runway illusion occurs when pilots misjudge the angle or elevation of a runway. This illusion is typically experienced in certain visual conditions, primarily when a pilot is approaching a runway that slopes upward relative to their flight path. When this happens, the pilot can perceive the runway as being higher than it actually is.

This misperception can lead to dangerous situations, especially during approaches and landings, where a pilot might be overly cautious and reduce the descent rate too much, potentially causing a prolonged approach or even a stall. The illusion is often amplified under low visibility conditions or when the surrounding terrain obscures the perspective of the runway's alignment with the ground.

Understanding this illusion is crucial for pilots because it highlights the importance of relying on instruments as well as visual cues when making landing decisions, particularly in varied environments and conditions. Reducing reliance solely on visual perception helps mitigate safety risks associated with this illusion.