Aviator's Dilemma: Pilots Encounter Illusions Everywhere

Military aviators learn to second-guess their senses

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MAJOR PAUL “Goose” Gosden, U.S. Marine Corps, piloted his UH-1 Huey close air support helicopter across the Kuwait-Iraq border through the night’s oily blackness. His aircraft was first to cross into Iraqi airspace in the second Gulf War, in support of Cobra attack helicopters tasked to destroy observation posts on Safwan Hill, near the infamous Highway of Death. Their mission was the opening salvo of Operation Iraqi Freedom, designed to kick in the door for the U.S. Army’s Third Infantry Division, which would follow in a ground assault from Kuwait into Iraq. The Iraqi forces, however, anticipated the aerial sortie and had begun to destroy oil fields, filling the night air with oil smoke and haze so thick that it blinded the marines.

Military flight training ingrains night flying so deeply that pilots can do it practically in their sleep. Flying through an oil cloud at night, on the other hand, definitely ups the pucker factor. “Saddam had exploded the oil rigs to fill the air with oil. I couldn’t see the Cobra in front of me or the stars or the moon. It was just black,” Gosden recalled. To give yourself an idea of this feeling, start a mission in the helicopter combat Xbox game Apache (which one of us, Macknik, diligently toiled over as “research” for this article). Fly very high over enemy territory, then turn off your television (but not the Xbox) and try to land your helicopter blind as the bad guys begin to shoot at you. Remember, to simulate the experience of Gosden and his crew, you would have to commit to actually killing yourself if your simulated copter crashes; otherwise it’s just a game.

Spatial D and the Leans
Gosden told his hair-raising story at the Aviation Survival Training Center in Marine Corps Air Station Miramar near San Diego, Calif., during a course one of us (Gayles) teaches. This air station was the storied home of the U.S. Navy’s (“Top Gun”) Fighter Weapons School, featured in the 1986 Tom Cruise movie.

Gosden—coincidentally “Goose” is the call sign of Cruise’s wingman in Top Gun—continued, “We all had ‘spatial D’ or were suffering from ‘the leans.’” Spatial D is short for spatial disorientation, a catchall term to describe the summed result of the various perceptual illusions and degraded sensory perceptions that may occur on a mission. It is the total failure of situational awareness and, shockingly, the most common cause of crashes in the navy, accounting for almost 80 crashes between 1990 and 2008. Performance fails because pilots can no longer pay attention to what is happening—everything is off-kilter. All they can do is scan the instruments continually to give themselves as much factual information about the aircraft as possible, to counteract the false information from deceitful bodily senses.

The leans is not a colorful military term for gastrointestinal distress, although the two phenomena are, unsurprisingly, often experienced together. Rather the leans is a type of somatogyral illusion you feel in flight when your vestibular system (the inner ear organ responsible for balance and your sense of traveling through space) and your somatosensory system (skin and other bodily positioning sensors) together fail to provide you with an accurate description of where gravity indicates is down. The illusion happens when you come out of a tight acrobatic turn and the fluid in your vestibular semicircular canals system continues to flow even though you are no longer turning. As a result, you may feel like you are flying straight when in fact you are in a turn, something that investigators concluded happened when John F. Kennedy, Jr.’s plane crashed at Martha’s Vineyard in 1999. Technically, the leans is the name of a solution to the problem: leaning your head until your instruments match your perception. Even so, most pilots use the term to relay the problem rather than the solution.

To get an idea of how critical your vestibular system is to your vision, hold up one finger in front of you at arm’s length, then look at it as you rotate your head back and forth. Fine, no problem: your finger is nice and clear. Your vestibular system tracked the turning of your head and gave your eyes the information to stay on target. Now hold your head still and move your finger back and forth while following it with your eyes. Now there is no vestibular input because your head is stationary, so your finger becomes blurry. Motion sickness arises from a mismatch between vision and vestibular perception and is a major component of spatial D.

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This article was originally published with the title "The Aviator's Dilemma."

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