Planes can float, but the US Airways Airbus A320 that crashed into the Hudson River yesterday had a better chance than most because it was equipped with a special device unique to Airbus planes that increased the likelihood it would stay on top of the water. The device, called a "ditching switch," effectively seals the plane by closing valves and ventilation ports. Industry experts said the ditching switch is rarely invoked, as "it's not as if anyone expects to ditch these planes." With the valves and ports shut, "a float line" is created. "The ditching switch closes all of the open ports in the bottom of the fuselage." Opening an emergency exit - which happened yesterday when the plane was evacuated - is not a problem as long as the door is above the waterline.
Peter R. Leffe, an aviation accident investigator in Malibu, Calif., noted that because airplanes in general are pressurized, they have some ability to float, providing they don't break up when they hit water. "The airplane is a pressure vessel," he said. "It can float as long as water doesn't leak in." But airplanes can't float forever. Water will eventually find a way to seep in, and the airplane's weight will drive it to the bottom, they're not amphibious. "But the general rule of thumb is, when they're full of fuel, which is lighter than water, they will float, as long as their structural integrity is intact."
The Airbus A320, along with the Boeing 737-800, is one of the two most "ubiquitous aircraft" in American air travel. It has an aluminum hull and is "as garden variety as airplanes get." There are about 2,000 A320 Airbuses worldwide, 425 of which are in North America. The planes, which debuted in 1988, typically seat 150 passengers and are the most popular Airbuses.