Night Flying: Understanding the Importance of Shadows

Written by Andre Louis-Ferdinand

As most of you know, flying any aircraft at night carries its own particular set of challenges. First, the lack of visibility. Second, visual illusions caused by your eye's inability to understand what is going on in low or zero light. Visibility seems obvious, but it truly isn't. Your eyes are very dependent on many basic visual cues that are only present with proper daylight. These include movement, distance/altitude, shapes, and even color. One of these basic visual cues that we don't even think about are shadows. Don't believe me? Look to the right. Is the shape to the right two different colors or is it one? Put your finger entirely over the red box so the middle of the shape is blocked out and look again. Do you see that the shape is actually one color now?

Believe it or not, shadows are a vital part in how your eyes interpret many things that are important to safe flight. You are probably thinking, why is color important at night anyway? Well, the problem isn't just color. "In a world with a single light source, your brain has learned to trust shadow as a near fool-proof way to know the behavior of objects in space." Shadows are extremely important to determine movement and distance. For more on this, check out this VIDEO.

Now, because we fly UAS (Unmanned Aircraft Systems), we are immune to many of the illusions that burdened manned flight for over a century. For example, Coriolis Illusions, Somatogravic Illusions, Elevator Illusions, and Inversion Illusions are all night flying illusions we don't have to worry about as UAS operators. However, with unmanned aviation, many old challenges are now exacerbated, such as reliance on shadows.

Even experienced aviators that are aware of these situations still fall victim to them. For example, yesterday evening I was doing patterns (take-offs and landings) with my drone. While on approach on my seventh landing, using FPV (First Person Video), I had to do an abrupt go-around (aborted landing) that could have caused a crash.

On the approach I was passing through and over a well lit area to a darker area. Once I moved into the darker area, the shadows caused by the lights from behind, became elongated. This caused my eyes to be momentarily tricked into believing that I was much lower than my altimeter stated. For a second, I made a very big mistake that they tell aviators to never do in a bad situation: I trusted my eyes over my instruments. The light from behind mimicked the sun and caused me to feel as if the tree's shadows in front of me were too long for my current altitude. Feeling that I was too low to the ground at this speed, I panicked and clumsily accelerated to take off as quickly as possibly, nearly missing a collision with a slender tree. In actuality, nothing was ever wrong and I was on the correct approach angle the entire time.

When in a bad situation, TRUST your instruments on your FPV, but verify what they are telling you if you can. A quick glance to my left would have confirmed that my altimeter was correct. For more information on night illusions while flying, click HERE.

Please feel free to comment below? What are your experiences flying at night?