What pilots see from the cockpit may not be what's really there.
Although there are no statistics to back him up, research optician Dr. Van B. Nakagawara of the Civil Aeromedical Institute at the Mike Monroney Aeronautical Center feels that optical illusions play a big role in air crashes and near misses.
"Accident investigators are not trained to ask these types of questions (regarding optical illusions), and pilots are not going to volunteer anything for fear of losing their license," said Nakagawara, who has been involved with the Federal Aviation Administration optical testing for eight years. "They will come in a talk with me to tell me things that have occurred while they were flying. They realize that I'm not going to yank their license.
"I feel that this is a much bigger problem than most people suspect, even though there are no hard numbers to support this."
Optical illusions range from lack of depth perception to empty field myopia where a person becomes almost hypnotized from staring into empty space for a long period.
"This type is especially prevalent when a pilot is flying above the clouds with nothing to see but blue sky above and white clouds below," he said. "It's like a person riding in a car and staring out the window for a long time, that person may find himself with a nearsighted focus, not being able to see anything outside the window."
Clear and bright objects which have brilliant colors appear to be closer, especially when in the air, while indistinct objects appear to be farther away than they actually are, Nakagawara said.
This is one reason why some pilots sometimes make a harder landing than intended, he said. "This is something that all pilots must be aware of," he said. "It doesn't matter how experienced a pilot is, anyone can be susceptible to an optical illusion.
"The best thing a pilot can do is be aware of something like this could happen and seek information from other sources."
A form of vertigo, or spatial disorientation, also is caused by an optical illusion.
There's a case that Nakagawara has written about where a pilot lost his glasses in flight and as he fumbled around to find them, the plane went into a dive.
"He couldn't see his instruments to relate to where he was, but he felt like he was climbing," Nakagawara said. "But something told him that he was diving, he was experienced enough to take information from other senses besides his sight. Even though he had the full sensation of being in a climbing airplane, he would hear the engines roaring as if the plane were diving.
"He pulled up, found his glasses and was able to land without incident.
"This just shows how easy it is to get disoriented in an airplane."
In another incident, this one involving a nonroutine landing, was created when the pilot was making a landing and had everything lined up perfectly. Only thing is, his vision told him that he was over a section of flat land, but there was an embankment between him and the runway. The pilot crashed, but there were no fatalities, Nakagawara said.
"There are numerous things which can cause an optical illusion, ranging from pilots wearing the wrong optometric equipment (eyeglasses) to having dirty glasses and a dirty windscreen," he said. …