Night Visual Illusions - In Air and On the Ground
Automobiles are familiar places to begin to discuss how we estimate car speed when we drive a boxy sedan or a race car.
If you own a sports car you get used to viewing the objects you pass on the road as a way to judge your car speed. If you take the family on a vacation you might use a SUV. The driver sits higher above the road in a SUV.
Now, at sixty miles per hour, it seems to the sports car driver, the Van is going slower. You just experienced a visual illusion in perception.
A runway is outlined with a lighting system. During normal night landings, in no-wind conditions, the lights help you judge when the wheels will touch the runway. As you descend towards the runway the lights move faster in your peripheral vision.
In a strong head wind the runway lights in your peripheral vision seem to move slower than usual. You perceive you are higher than you think. Dangerous illusion. You may hit the surface of the runway before you are ready to land. You thought you were higher because of the slower movement of the lights.
With a significant tail wind the illusion changes. If you make a mistake, and fail to notice the direction of the lighted windsock, a downwind landing illusion is possible.
In this illusion you may be considerably higher than you think. Now, in your peripheral vision, the lights indicate you are just about to touchdown. You slow your plane and prepare to stall perfectly in a smooth landing. Instead, at the moment of the stall, you realize you are some distance above the runway and hit the runway in a nose down attitude. This is not good for you or the airplane.
The purpose of this post is making you aware of the possibility of illusions when landing at night. Don't succumb to them. Know the flight conditions at the airport.
Of course, if you are a newbie to flying you used landing lights to help you visualize the runway.
