What is the primary outcome of rain on the windscreen during flight?

When rain accumulates on the windscreen during flight, it can create visual illusions that affect the pilot's perception of altitude. Specifically, the precipitation can obscure outside references and alter the visual cues that pilots rely on, leading to the sensation of being higher than the aircraft's actual altitude. This phenomenon occurs because the visual system becomes confused as the rain drips down and distorts the view, making the horizon appear lower and possibly misleading the pilot's judgment of altitude.

Understanding this effect is crucial for pilots, as it emphasizes the importance of relying on instruments for altitude rather than visual references, especially in conditions where rain or precipitation is present. This helps to mitigate the risks associated with spatial disorientation and ensures safe flight operations.