Daytime Black Holes

demonstrating how the black-hole approach effect works in daytime conditions."

Glenn Grubb

Friday, September 22, 2017 at 12:00 AM ET

Verified

Key Takeaways:

Optical illusions, particularly the "black-hole illusion," pose a significant safety risk in aviation by causing pilots to misjudge their height and descent rate, often leading to landing short of the runway.
This illusion primarily occurs when visual cues are limited (e.g., night landings over unlit terrain), where the brain misinterprets the runway's changing visual angle, making a straight glideslope appear too high and prompting pilots to increase their descent.
Beyond night flying, the author discovered the black-hole illusion can also affect daytime approaches to upsloping runways, as the terrain configuration similarly reduces peripheral visual cues and distorts depth perception.
Pilots must understand how these visual deceptions trick the brain's interpretation of distance and height to anticipate and compensate for illusions, ensuring stabilized and safe approaches.

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Optical illusions are all around us. A classic example might be when looking through a camera and a slow-turning airplane propeller or the wheel spokes on a car appear to slow and then reverse direction. None of that happens, of course; part what we “see” is determined by how well our eyes and brain work and play together. The bad news is there are many other optical illusions, and they can actually be quite dangerous if encountered while flying. The good news is we can understand them, anticipate them, then compensate for them.