From the NYtimes:
Ditching can be tricky. The first step is to extend the slats and the flaps, the movable surfaces on the front and back edges of the wings that allow the plane to fly more slowly and to descend to just over the water’s surface.
Another step is to hit the “ditching button,” which seals the openings in the plane. One is the intake, where the engines grab air to pressurize and force it into the cabin, essential to high-altitude flight. Another is the valve at the back that lets air out.
When the plane is flying low enough, it will generate its own cushion of air, a phenomenon called “ground effect,” that lets it fly even more slowly.
“The whole point is to get the airplane slow, to minimize the damage and the forces on the airplane,” said John Cox, a safety consultant who flew the A320 for US Airways and USAir for six years.
From the Globe and Mail:
Passenger jets are designed to remain buoyant long enough to let passengers exit after landing. When the doors are opened, inflatable emergency slides automatically deploy, then detach from the aircraft so they can be used as life rafts.
When pilots face an emergency landing caused by power failure, water is often preferable to dry land, which is typically covered with obstacles such as buildings, power lines, hills or roads. In general, ditching follows the same flying principles as landing on a paved runway. “You want to minimize the speed and stay in control,” said a pilot for one major U.S. airline. “You just treat it like a landing, but you leave the gear up.”
