Birds getting sucked into an engine is a routine hazard for pilots. But the multiple bird strikes suspected of disabling both engines of the US Airways plane Thursday may be a first for a modern jetliners.
According to a Federal Aviation Administration official, the pilot reported flying through a flock of geese, sucking several of the birds into both engines and forcing an emergency landing in the Hudson River.
Air safety experts put the odds of two engines simultaneously being disabled by birds at less than one in several million. Airplane engine maker General Electric has no record of such a dual hit causing an accident in at least two decades.
Preliminary indications were that the plane, which departed from New York's LaGuardia Airport, suffered several bird strikes and the speed of the impact -- which can amount to being hit by something weighing a ton or more -- was significant enough that some passengers believed they were going through an area of turbulence.
Pilots are trained to routinely inform controllers and fellow pilots if they spot even a single bird or balloon or some other object floating in the path of landing aircraft. The danger is greatest at takeoff and in low altitude, when turbine blades in jet engines are sucking in lots of air.
The FAA and airport operators have long conducted research on how to keep birds from flocking around busy airstrips -- but have never completely succeeded. Over the years, federal regulators have tightened safety regulations to try to reduce the danger of bird strikes. Before they are approved for commercial use, engines are tested repeatedly to assure that they can withstand the impact of birds that weigh several pounds apiece. Engine makers test their product design by throwing frozen poultry into the spinning fan blades to make sure the engines don't disintegrate.
Those standards have gotten tougher in recent years, but experts say it's impossible to build a failsafe engine. The Airbus engines were tested to withstand the impact of a single bird weighing less than five pounds, but some geese can weigh more than three or four times that. "It's like throwing bowling balls into engines," says Greg Feith, a former National Transportation Safety Board investigatorr. "You can't build engines to handle that because they would weigh so much that the plane would never get off the ground."
In 2007 in Rome, a Delta Air Lines Boeing 767 sucked birds into both of its engines shortly after talking off. The widebody jet barely managed to climb, keep one engine running and limp back to the airport, without any injuries.
Bird Strike Committee USA, a voluntary organization that includes representatives from the FAA, the Defense Department, airports and the airline industry, estimates that bird and other wildlife strikes to aircraft have resulted in 219 deaths world-wide since 1988 and hundreds of million of dollars of damage annually.
The group exchanges information and researches new technology to reduce such hazards. The FAA has a Web site where pilots and others can report bird strikes. The FAA says that overall, bird strikes have been climbing in recent years and the current average of more than 7,000 annual incidents is almost three times what they were at the beginning of the decade. Most experts say growing bird populations and changing migration patterns are largely to blame.
Some large international airports, including New York's Kennedy International, Tel Aviv's Ben Gurion airport and several fields in India are renowned among pilots for having a persistent problem with flocks of birds. In some cases, pilots have urged changes in arrival or departure routes to minimize such dangers. (info from The Wall Stree Journal)