What does a down sloping runway cause during an approach?

A down sloping runway can create the illusion of being lower than normal during an approach. This is primarily due to the visual perception of pilots; as they approach a runway that slopes downward, they may feel as though they are at a lower altitude than they truly are. This perception can affect their approach judgment, potentially leading them to miscalculate their descent and level-off point.

In aviation, visual illusions can significantly impact a pilot's decision-making and control inputs. Specifically, when facing a downward sloping runway, pilots might underestimate their height above the ground, resulting in a higher chance of approaching the runway too low or, conversely, making a steep and abrupt change in their flight attitude to compensate for the perceived altitude difference.

Understanding this illusion is crucial for pilots, as it emphasizes the importance of relying on instruments and maintaining situational awareness rather than solely trusting visual cues while approaching a runway.