Desert sandstorms add dangers for pilots

April 9, 2003

COLLEGE STATION - As the war continues in Iraq, helicopter and fighter pilots face dangers of experiencing disorientation during landings in areas prone to sandstorms. Dr. Charles Lessard, associate professor in the Department of Biomedical Engineering at Texas A&M University, has studied pilots and the spatial disorientation they might experience operating in environments with poor visibility. The Air Force defines spatial disorientation as an incorrect perception of one's position and motion relative to the earth's surface. In Iraq where the terrain is mostly sand, pilots are likely to experience a brownout, a lack of distinct horizon due to blowing sand or dust. When the sand blows across the terrain, the illusion of the horizon is tilted and the pilot, if not watching his instruments, may react by lining his plane's wings with the false horizon. This can result in hard landings or a crash because the plane isn't flying level as it approaches the landing strip. "Helicopter pilots suffer most from brownouts because they fly at very low altitudes," Lessard said. In the landing phase, helicopters cause sand to blow upward and in a circular pattern, which not only obscures the ground but can lead to vection. Vection is the perception of moving (forward, up-down, or in rotation) when in fact the helicopter is hovering but not moving. "Most of us experience the illusion of vection when stopped at a light and the car beside us moves," Lessard said. "The peripheral vision causes us to perceive that it is our car that is moving so we step harder on the brake peddle." Lessard studied experienced instructor fighter pilots and the various types of spatial disorientation they experienced during flight and in flight simulators. Pilots can overcome disorientation by relying on their cockpit instruments. However, in worst-case scenarios the reaction time may not allow enough time for the pilot to overcome the illusion.

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